JP2009139260A - Liquid level estimating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid level estimating device which enables accurate estimation of a liquid level when a liquid surface fluctuates. <P>SOLUTION: The liquid level estimating device estimates a liquid level H which is a distance from the bottom of a fuel tank 2 storing a liquid to the liquid surface. The device includes an estimating means which estimates the level H when no wave rises on the liquid surface, based on the propagation velocity V of waves rising on the liquid surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid level estimation device that estimates a liquid level that is a distance from a bottom surface of a container in which a liquid is stored to a liquid level.

In a conventional liquid level estimation device, a liquid level is detected by a liquid level sensor that outputs a voltage corresponding to the liquid level. In addition, as another liquid level estimation apparatus, the thing of patent document 1 is known, for example.
JP 2000-65623 A

  However, according to the above-described conventional apparatus, when the vibration occurs on the liquid surface, the output value of the sensor fluctuates accordingly, and it is difficult to estimate the accurate liquid level. That is, when the amplitude of the vibration of the liquid level that is the detection target of the liquid level by the sensor increases, a voltage larger than the voltage corresponding to the original liquid level, that is, the liquid level when no vibration is generated is output. Therefore, the detected liquid level is also higher than the original liquid level.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid level estimation device capable of accurately estimating the liquid level when vibration occurs on the liquid surface.

In the following, means for achieving the above object and its effects are described.
(1) According to the first aspect of the present invention, in the liquid level estimation device that estimates the liquid level that is the distance from the bottom surface of the container in which the liquid is stored to the liquid level, the propagation of the wave generated on the liquid level The gist of the invention is to provide an estimation means for estimating the liquid level when no wave is generated on the liquid surface based on the velocity.

According to the above invention, since the liquid level is estimated by actively utilizing the behavior of the wave generated on the liquid level, the liquid level can be accurately estimated when vibration occurs on the liquid level. become.
(2) The invention described in claim 2 is the liquid level estimation device according to claim 1, wherein the estimation means sets the wave propagation velocity to “V”, the gravitational acceleration to “g”, and the wave is generated. The gist is to calculate the liquid level by the following arithmetic expression (A), assuming that the liquid level when it is not is “H”.

H = V2 / g (A)

According to the above invention, the liquid level can be estimated only by grasping the wave propagation velocity and the gravitational acceleration, so that the process for estimating the liquid level can be simplified. Become.

(3) The invention according to claim 3 is the liquid level estimation apparatus according to claim 1, wherein the estimation means sets the wave propagation velocity to “V”, the wave amplitude to “h”, and the gravitational acceleration. The gist is to calculate the liquid level by the following arithmetic expression (B), where “g” is the liquid level when no wave is generated and “H”.

H = (V2 / g) -h (B)

According to the arithmetic expression (A), it is confirmed that when the actual wave amplitude with respect to the liquid level when no wave is generated is large, the liquid level estimation accuracy is greatly reduced due to this. . In this respect, in the above invention, since the liquid level is estimated by the calculation formula (B) in which the influence of the amplitude of the wave on the estimation accuracy is smaller than that of the calculation formula (A), a wave is generated. Even when the amplitude of the actual wave with respect to the liquid level when it is not high is large, the liquid level can be accurately estimated.

(4) The invention according to claim 4 is the liquid level estimation device according to claim 1, wherein the estimating means sets the wave propagation velocity to “V”, the wave amplitude to “h”, and the gravitational acceleration. Is “g”, and the liquid level when no wave is generated is “H”. First, the liquid level is calculated by the following equation (A),

H = V2 / g (A)

Next, using “H” calculated here, it is determined whether or not the term “h / H” in the following equation (C) is less than a predetermined value set as a value smaller than “1”.

V = (H · g (1 + h / H)) 1/2 (C)

When a result indicating that the result is less than a predetermined value is obtained by this determination, “H” according to the arithmetic expression (A) is used as an estimated value of the final liquid level, and a result indicating that the result is greater than or equal to the predetermined value is obtained by the determination. Sometimes, the gist is to calculate “H” by the following equation (B) and use this as the final estimated liquid level.

H = (V2 / g) -h (B)

Here, the calculation formula (C) is a basic calculation formula showing the relationship between the wave propagation velocity and the liquid level, and the calculation formula (B) is modified so that the liquid level appears on the left side. In the above equation (A), the term of “h / H” is replaced with “0”, and this is modified so that only the liquid level exists on the left side. Equivalent to. In the above invention, even when the term “h / H” is less than the predetermined value, that is, the term “h / H” is regarded as “0” and the liquid level is estimated by the above equation (A). When there is no significant influence on the accuracy, the liquid level is calculated by the equation (A), and when the term “h / H” cannot be ignored, the liquid level is calculated by the arithmetic equation (B). Therefore, the estimation accuracy can be increased as compared with the case where the liquid level is estimated only by the arithmetic expression (A).

(5) The invention according to claim 5 is the liquid level estimation device according to any one of claims 1 to 4, wherein the estimation means sets the representative length of the container to “L”, The gist of this is to calculate the propagation speed of the wave by the following arithmetic expression (D), where “T” is the propagation time which is the time required for the wave to propagate this representative length.

V = L / T (D)

According to the above invention, the wave propagation speed can be calculated only by grasping the representative length and propagation time of the container, so that the processing for calculating the wave propagation speed is simplified. Will be able to. Note that the typical length of the container is unique to the container, and if this is set in advance, the only parameter that needs to be monitored when estimating the liquid level is the propagation time, and the processing for calculating the wave propagation velocity is thereby performed. Can be made simpler.

  (6) The invention according to claim 6 is the liquid level estimation device according to claim 5, wherein the estimation means is configured to measure the liquid level based on an output signal from a sensor that outputs a signal corresponding to an actual liquid level. The gist of this is to calculate one period of the wave generated in the above and set it as the propagation time.

  (7) The invention according to claim 7 is the liquid level estimation device according to claim 5, wherein the estimation means is configured to detect the liquid level based on an output signal from a sensor that outputs a signal corresponding to an actual liquid level. The N period (N is an integer of 2 or more) of the wave generated in the above is calculated, and this is used as the propagation time. In conjunction with this, the representative length is multiplied by N, and the propagation time and the representative length are represented by the arithmetic expression. The gist is to calculate the wave propagation velocity by applying to (D).

  According to the above invention, the N period of the wave generated on the liquid surface is calculated, and this is used as the propagation time. In conjunction with this, the representative length is multiplied by N, and the propagation time and the representative length are calculated using the above equation ( The wave propagation velocity is calculated by applying to (D). For this reason, compared with the invention according to claim 6, that is, when one cycle of the wave on the liquid surface is defined as the propagation time and the wave propagation velocity is calculated based on the propagation time and the representative length, Since the influence of the dispersion of the propagation time, which is one cycle of the wave, is reduced, the propagation time of the wave and hence the liquid level can be estimated more accurately.

(8) The invention according to claim 8 is the liquid level estimation device according to claim 5, wherein the estimation means calculates the natural frequency of the wave composed of the largest vibration component among the waves including a plurality of vibration components. F ”, the natural frequency is calculated by frequency analysis of the output signal from the sensor that outputs a signal corresponding to the actual liquid level, and then the propagation time is calculated by the following equation (E): It is a summary.

T = 1 / F (E)

According to the above invention, frequency analysis is performed on an output signal from a sensor that outputs a signal corresponding to an actual liquid level, and a natural frequency of a wave composed of the largest vibration component is calculated for a wave including a plurality of vibration components, In addition, the wave propagation time is calculated from the reciprocal of this natural frequency. For this reason, even when it is difficult to accurately calculate the propagation time of the liquid surface wave due to the wave generated on the liquid surface being a wave containing a plurality of vibration components, Can do. Therefore, the liquid level can be accurately estimated when a wave including a plurality of vibration components is generated.

  (9) The invention according to claim 9 is the liquid level estimation apparatus according to any one of claims 1 to 8, wherein the estimation means is a first estimation means, and the liquid level is estimated by the estimation means. Apart from that, the gist is to further include second estimating means for estimating the liquid level when no wave is generated on the liquid surface.

  (10) The invention according to claim 10 is the liquid level estimation device according to claim 9, wherein the estimated liquid level by the first estimating means and the estimated liquid level by the second estimating means The gist is to determine that an abnormality has occurred in the estimation device based on the fact that the degree of divergence is greater than a predetermined degree.

  When the liquid level estimation device is normal, the estimated value of the liquid level by each estimating means shows a close value. Therefore, when the degree of deviation of the estimated value by each estimating means is larger than a predetermined degree, the liquid level is estimated with this. It can be determined that an abnormality has occurred in any part of the apparatus.

  (11) The invention according to claim 11 is the liquid level estimation device according to claim 9 or 10, wherein the second estimation means estimates the liquid level by a method different from that of the first estimation means. The gist is to do.

  According to the above invention, the first estimation means and the second estimation means estimate the liquid level by a different method. Therefore, when an abnormality occurs in any part of the estimation device, this is the first The difference between the estimated value by the estimating means and the estimated value by the second estimating means is reflected more remarkably. Accordingly, it is possible to more accurately determine the abnormality of the apparatus as compared with the first estimation unit and the second estimation unit that estimate the liquid level by the same method.

  (12) The invention according to claim 12 is the liquid level estimation device according to claim 11, wherein the second estimation means smoothes the output signal of the sensor for detecting the liquid level to thereby adjust the liquid level. The gist is to estimate.

<First Embodiment>
A first embodiment in which the liquid level estimation device according to the present invention is specifically used as a fuel level estimation device for a fuel tank of an in-vehicle internal combustion engine will be described with reference to FIGS.

  As shown in FIG. 1, the vehicle includes a fuel tank 2, an electronic control device 6 that estimates the fuel level in the tank 2, that is, the distance from the bottom surface of the fuel tank 2 to the fuel level, and the vehicle An acceleration sensor 8 that outputs a signal corresponding to the acceleration G is provided.

  The fuel tank 2 has a rectangular parallelepiped shape, and is provided such that its longitudinal direction coincides with the longitudinal direction of the vehicle. Here, the length of the fuel tank 2 in the front-rear direction of the vehicle is referred to as “representative length L”. A liquid level sensor 4 that outputs a signal corresponding to the actual liquid level is provided inside the fuel tank 2. The liquid level sensor 4 includes a float 42 that floats on the liquid surface, and outputs a signal corresponding to the vertical position of the float 42, that is, a signal corresponding to the liquid level.

  The electronic control unit 6 includes a central processing control unit (CPU), a read-only memory (ROM) that stores various programs and maps in advance, a random access memory (RAM) that temporarily stores CPU calculation results, a timer counter, an input The microcomputer is mainly configured with an interface and an output interface.

Based on the output signal S of the liquid level sensor 4, the propagation speed V of the wave generated on the liquid surface is calculated. Based on the propagation speed V, the liquid level H when no wave is generated on the liquid surface is calculated. presume.
Next, details of the liquid level estimation method will be described with reference to FIGS. 2 schematically shows the state of the float 42 and the wave when the wave is generated on the liquid surface, and FIG. 3 shows an example of the time change of the output signal S by the liquid level sensor 4. . FIG. 4 shows the state of the float 42 and the wave when the wave is generated on the liquid surface, where (a) shows the state when the liquid level H is larger than the amplitude h, and (b) shows the state where the amplitude h. On the other hand, the situation when the liquid level H is small is shown.

  As shown in FIG. 2, when a wave traveling forward is generated on the liquid surface when the vehicle moves forward, the float 42 is displaced in the vertical direction as the wave propagates. Therefore, as shown in FIG. 3, the output signal S from the liquid level sensor 4 is a predetermined value S0 according to the vertical displacement of the float 42, that is, an output signal when no wave is generated on the liquid surface. As shown in FIG. 4, the value fluctuates between the maximum value S1 and the minimum value S2.

Here, when estimating the liquid level, the time when the output signal reaches the maximum value S1 is set to “t1”, the time when the output signal reaches the maximum value S1 again is set to “t2”, and then the maximum value is set again. When the time when S1 is reached is “t3”, the period from time t1 to time t3, that is, two periods of the wave generated on the liquid surface is calculated, and this is adopted as the propagation time 2T. At the same time, the representative length L is doubled, and the doubled representative length 2L and the propagation time 2T are applied to the following equation (D) to calculate the wave propagation velocity V. .

V = L / T (D)

Then, the liquid level H when no wave is generated is calculated by applying the propagation velocity V calculated in this way and the gravitational acceleration g to the following arithmetic expression (A).

H = V2 / g (A)

Further, as shown in FIG. 3, the minimum value S2 of the output signal S is detected, and the minimum value S2 and the maximum value S1 are applied to the following equation (F) to calculate the wave amplitude h.

h = (S1-S2) / 2 (F)

Here, when the relationship between the liquid level H calculated by the arithmetic expression (A) and the amplitude h calculated by the arithmetic expression (F) satisfies the following relational expression (G), that is, the actual liquid level. When it is estimated that the relationship between H and amplitude h is in the state shown in FIG. 4A, the value calculated by the arithmetic expression (A) is the final liquid level H.

h / H <C (C <1) (G)

On the other hand, when the relationship between the liquid level H calculated by the arithmetic expression (A) and the amplitude h calculated by the arithmetic expression (F) does not satisfy the relational expression (G), that is, the actual liquid When it is estimated that the relationship between the position H and the amplitude h is in the state shown in FIG. 4B, it is calculated by the following equation (B) instead of the value calculated by the above equation (A). Is the final liquid level H.

H = (V2 / g) -h (B)

The relational expression (G) is for determining the magnitude of the influence of the term “h / H” on the wave propagation velocity V in the following arithmetic expression (C). The arithmetic expression (B) is obtained by modifying the following arithmetic expression (C), which is a basic arithmetic expression indicating the relationship between the wave propagation velocity and the liquid level.

V = (H · g (1 + h / H)) 1/2 (C)

In the arithmetic expression (C), when the relational expression (G) is satisfied, the term “h / H” has little influence on the wave propagation velocity V (liquid level H), and the relational expression (G ) Is not satisfied, the above-mentioned “h / H” term has a great influence on the wave propagation velocity V (liquid level H). Therefore, when the term “h / H” is less than the predetermined value C, the term “h / H” is replaced with “0”, and the equation (C) is obtained by modifying the equation (C). The liquid level is estimated by A), and when the term “h / H” is equal to or greater than the predetermined value C, this is maintained and the liquid level is estimated by the arithmetic expression (B).

  With reference to FIG. 5, the process procedure of the “liquid level estimation process” in which the liquid level estimation method described above is embodied as a process by the electronic control unit 6 will be described. This process is repeatedly executed by the electronic control unit 6 with a predetermined period. The liquid level estimation process by the electronic control unit 6 corresponds to an estimation unit (first estimation unit).

  In this series of processes, first, it is determined whether or not the acceleration G of the vehicle is greater than or equal to a predetermined value G1 (step S1). Here, when the acceleration G of the vehicle is less than the predetermined value G1 (step S1: “NO”), it is assumed that no wave is generated on the liquid surface, and this process is temporarily terminated. On the other hand, if the acceleration G of the vehicle is greater than or equal to the predetermined value G1 (step S1: “YES”), it is assumed that a wave is generated on the liquid level, and then the output signal S of the liquid level sensor 4 at that time From the above, the propagation time 2T is calculated (step S2). Next, the liquid level H1 is calculated by the arithmetic expression (A) (step S3). Next, the amplitude h is calculated by the arithmetic expression (F) (step S4), and a value obtained by dividing the amplitude h by the liquid level H1, that is, “h / H1” is less than a predetermined value C (C <1). It is determined whether or not there is (step S5).

  As a result, when the division value h / H1 is less than the predetermined value C (step S5: “YES”), as shown in FIG. 4A, the calculation value (A) is calculated. Assuming that the amplitude h is so small as to be negligible with respect to the liquid level H1, the liquid level H1 calculated by the above equation (A) is set as the final liquid level H (step 6), and this estimation process is temporarily terminated.

  On the other hand, when the division value “h / H1” is equal to or greater than the predetermined value C in the determination process of the previous step S5 (step S5: “NO”), as shown in FIG. Assuming that the amplitude h is so large that it cannot be ignored with respect to the liquid level H1 calculated by the equation (A), the liquid level H is calculated by the arithmetic equation (B) (step 7). Then, the calculated liquid level H2 is set as the final liquid level H (step 8), and the present estimation process is temporarily terminated.

According to the liquid level estimation apparatus according to the present embodiment, the following effects can be obtained.
(1) The liquid level estimation device includes estimation means for estimating the liquid level H when no wave is generated on the liquid level based on the propagation velocity V of the wave generated on the liquid level. In this way, since the liquid level H is actively estimated using the behavior of waves generated on the liquid level, the liquid level H can be accurately estimated when vibration occurs on the liquid level. become.

  (2) The estimation means calculates the liquid level H by the arithmetic expression (A). As described above, since it is possible to estimate the liquid level H only by grasping the wave propagation velocity V and the gravitational acceleration g, the process for estimating the liquid level H can be simplified. It becomes like this.

  (3) According to the arithmetic expression (A), when the actual wave amplitude h with respect to the liquid level H1 when no wave is generated is large, the estimation accuracy of the liquid level H1 is greatly reduced due to this. It has been confirmed. In this regard, the estimation means estimates the liquid level H2 by the above calculation formula (B) in which the influence of the wave amplitude h on the estimation accuracy is smaller than the calculation formula (A). Therefore, the liquid level H can be accurately estimated even when the actual wave amplitude h with respect to the liquid level H when no wave is generated is large.

  (4) When the term “h / H” in the arithmetic expression (C) is less than the predetermined value C, that is, the estimating means regards the term “h / H” as “0” and treats the arithmetic expression (A If the accuracy of the liquid level H1 is not significantly affected even if the liquid level H1 is estimated by (), the liquid level H1 is calculated according to the equation (A). If the term of “h / H” cannot be ignored, the above calculation is performed. The liquid level H2 was calculated from the formula (B). For this reason, it becomes possible to improve the estimation accuracy as compared with the case where the liquid level H1 is estimated only by the arithmetic expression (A).

  (5) The estimation means calculates the wave propagation velocity V according to the arithmetic expression (D). As a result, it is possible to calculate the wave propagation velocity V as long as the representative length L and propagation time T of the fuel tank 2 are grasped. Therefore, the processing for calculating the wave propagation velocity V can be simplified. To be able to. The representative length L of the fuel tank 2 is unique to the tank 2, and if this is set in advance, the only parameter that needs to be monitored when the liquid level H is estimated is the propagation time T. The process for calculating the speed V can be made simpler.

  (6) The estimation means calculates two periods of the wave generated on the liquid surface based on the output signal S from the liquid level sensor 4 that outputs a signal corresponding to the actual liquid level, and sets this as the propagation time 2T. At the same time, the representative length L is doubled, and the propagation time 2T and the representative length 2L are applied to the arithmetic expression (D) to calculate the wave propagation velocity V. Thereby, one cycle of the wave on the liquid surface is defined as a propagation time T, and one cycle of the wave on the liquid surface is compared with the case where the wave propagation velocity V is calculated based on the propagation time T and the representative length L. Since the influence of the variation in the propagation time T is small, the wave propagation time T and thus the liquid level H can be estimated more accurately.

  (7) As a conventional liquid level estimation apparatus, there has been proposed an apparatus in which the output signal S of the liquid level sensor 4 is smoothed in order to accurately grasp the liquid level. However, according to such an estimation device, the estimation accuracy of a plurality of estimation results by liquid level estimation performed at different timings may vary greatly due to the influence of the fluctuation of the wave amplitude. It is inevitable that excessive variations occur in the reliability of the device.

  Here, it is assumed that the liquid level estimation is performed twice by the conventional liquid estimation apparatus. Of these two estimations, the first estimate is the first estimate and the next estimate is the second estimate. Further, it is assumed that the second estimation is performed based on the output signal S of the liquid level sensor 4 obtained in a period in which the wave amplitude is sufficiently larger than the first estimation.

  According to the above assumed situation, the estimation accuracy (the degree of deviation from the liquid level H when no wave is generated on the liquid surface) is estimated for the liquid level X1 which is the estimation result obtained by the first estimation. ) Is the reference accuracy, the level of the estimation accuracy of the liquid level X2, which is the estimation result obtained by the second estimation, is excessively larger than the reference accuracy due to the influence of the wave amplitude. .

  On the other hand, in order to minimize the variation in the estimation accuracy as described above, for example, it may be possible to set the liquid level sampling period by the liquid level sensor 4 to be sufficiently large. An increase in time required for one estimation in exchange for maintenance is unavoidable.

  As described above, according to the estimation apparatus, it is difficult to achieve both of maintaining the level of estimation accuracy as constant as possible and setting the time required for one estimation small. .

  On the other hand, in the liquid level estimation device of the present embodiment, the wave period 2T is calculated from the output signal S of the liquid level sensor 4, and the liquid level H is estimated based on this, so Even in a situation where the variation degree of the amplitude is large, an increase in variation in estimation accuracy due to this is suppressed. Further, since the two cycles 2T of the wave of the liquid level generated when the vehicle travels are relatively short, the time required for one estimation of the liquid level is also shortened accordingly. That is, it is possible to achieve both of maintaining the estimation accuracy as constant as possible and shortening the time required for one estimation.

Second Embodiment
With reference to FIG.6 and FIG.7, 2nd Embodiment of the liquid level estimation apparatus concerning this invention is described.

  In the present embodiment, the following changes are mainly added to the previous first embodiment. That is, in addition to the liquid level sensor 4, the liquid level sensor 5 that outputs a signal corresponding to the liquid level is provided, and the electronic control unit 6 performs “smooth estimation” that is a separate process from the previous “liquid level estimation process”. In the “processing”, the output signal X is smoothed to estimate the liquid level Hb when no wave is generated on the liquid surface.

  The degree of divergence between the estimated liquid level value Ha by the “liquid level estimation process” as the first estimation means and the estimated liquid level value Hb by the “annealing estimation process” as the second estimation means is predetermined. It is determined that an abnormality has occurred in any part of the liquid level estimation device including the liquid level sensor 4 and its peripheral device and the liquid level sensor 5 and its peripheral device. . In the present embodiment, the liquid level Hb estimated by the “annealing estimation process” is the liquid level of the fuel tank 2 that notifies the driver, and the liquid level Ha estimated by the “liquid level estimation process” is the above-described abnormality. It is used only for judgment.

  As shown in FIG. 6, a liquid level sensor 5 that outputs a signal X corresponding to the actual liquid level is provided inside the fuel tank 2. Similar to the liquid level sensor 4, the liquid level sensor 5 also includes a float 52 that floats on the liquid surface, and outputs a signal corresponding to the vertical position of the float 52, that is, a signal corresponding to the liquid level.

  The electronic control unit 6 executes “liquid level estimation processing” and “annealing estimation processing” in parallel, and in the latter case, the output signal X of the liquid level sensor 5 is smoothed, that is, the output signal X is predetermined. The liquid level is estimated by sampling over a period of 5 to calculate the average value of the plurality of output signals X. In addition, an “abnormality determination process” is performed in conjunction with each of the above processes. In this process, an estimated liquid level value Ha by the “liquid level estimation process” and an estimated liquid level value Hb by the “annealing estimation process” are obtained. Comparison is made, and based on this result, it is determined whether or not an abnormality has occurred in the estimation apparatus.

A specific processing procedure of the “abnormality determination process” will be described with reference to FIG. This process is repeatedly executed by the electronic control unit 6 with a predetermined period.
In this series of processes, first, the current liquid level Ha estimated by the “liquid level estimation process” is read (step S11). Next, the current liquid level Hb estimated by the “annealing estimation process” is read (step S12). Next, whether or not the absolute value | Ha−Hb | of the difference between the estimated value Ha by the “liquid level estimation process” and the estimated value Hb by the “smooth estimation process” is larger than a predetermined determination value D is determined. Judgment is made (step S13).

  As a result, if the absolute value | Ha−Hb | is larger than the preset determination value D (step S13: “YES”), it is determined that an abnormality has occurred in the device, and this abnormality has occurred. The determination process is temporarily terminated. On the other hand, when the absolute value | Ha−Hb | is equal to or smaller than the preset determination value D in the determination process in step S13 (step S13: “NO”), no particular abnormality has occurred in the device. This abnormality determination process is once terminated.

According to the liquid level estimation apparatus according to the present embodiment, the following operational effects can be obtained in addition to the effects (1) to (7) of the first embodiment.
(8) The absolute value | Ha−Hb | of the difference that is the degree of deviation between the estimated liquid level value Ha by the “liquid level estimation process” and the estimated liquid level value Hb by the “smoothing estimation process” is a predetermined determination value. Based on the fact that it is larger than D, it is determined that an abnormality has occurred in any part of the estimation device. When the liquid level estimation device is normal, the estimated liquid level values Ha and Hb by the respective estimation processes are close to each other. Therefore, the absolute value of the difference between the estimated values Ha and Hb by the respective estimation processes | Ha−Hb | Can be determined that an abnormality has occurred in any part of the liquid level estimation device.

  (9) The “smoothing estimation process” that is the second estimation means estimates the liquid level by a method different from the “liquid level estimation process” that is the first estimation means. Thereby, when an abnormality occurs in any part of the estimation device, this is more significantly reflected as a deviation between the estimated value Ha by the “liquid level estimation process” and the estimated value Hb by the “annealing estimation process”. Become so. Accordingly, it is possible to more accurately determine the abnormality of the apparatus as compared with the first estimation unit and the second estimation unit that estimate the liquid level by the same method.

<Other embodiments>
In addition, the embodiment of the liquid level estimation apparatus according to the present invention is not limited to the configuration exemplified in the above-described embodiment, and can be implemented as, for example, the following forms appropriately modified.

  In the second embodiment, the role of the “liquid level estimation process” is set to determine that an abnormality has occurred in the liquid level estimation apparatus, and the liquid level Ha obtained by the process is the fuel in the fuel tank 2. However, the role of the “liquid level estimation process” can be changed as follows, for example. That is, the liquid level estimation by the “liquid level estimation process” and the “annealing estimation process” is executed in parallel when the vehicle is running, and the final liquid level estimation value is calculated by taking into account the liquid level estimation result. Based on this calculation, the remaining amount of fuel in the fuel tank 2 can be notified to the driver. Alternatively, either one of the estimation results obtained by the “liquid level estimation process” and the “annealing estimation process” can be selected, and based on this, the remaining amount of fuel in the fuel tank 2 can be notified to the driver.

  The following configuration can be further adopted in the second embodiment. In other words, the “liquid level estimation process” is to estimate the liquid level by actively utilizing the behavior of waves generated on the liquid level, and the “annealing estimation process” is to generate waves on the liquid level. In view of both of the fact that the liquid level can be estimated most accurately when it is not, the estimation process used for estimating the liquid level H is sometimes switched according to the vibration mode of the fuel tank 2. it can. In other words, based on the estimated or detected vibration mode of the fuel tank 2, it is determined which of “liquid level estimation processing” and “smooth estimation processing” can be used to ensure higher estimation accuracy, and this determination Depending on the result, the liquid level can be estimated at any time through only one of the estimation processes.

  More specifically, it is determined whether or not an excessively large vibration is generated in the fuel tank 2 based on the traveling state of the vehicle, that is, the liquid level by the “smoothing estimation process” due to the vibration of the fuel tank 2. It is determined whether or not the estimation accuracy is lower than the allowable range, and when a determination result indicating that the estimation accuracy is lower than the allowable determination is obtained, the liquid level is estimated by the “liquid level estimation process”. When a determination result indicating high is obtained, the liquid level can also be estimated by the “smoothing estimation process”.

  In each of the above embodiments, the acceleration sensor 8 detects the acceleration G of the vehicle, and based on this, it is determined whether or not there is vibration on the liquid level. The configuration for determining whether or not is not limited to this. For example, a sensor that directly detects vibration generated on the liquid surface can be used.

In each of the above embodiments, the propagation time 2T is directly calculated from the change mode of the output signal S of the liquid level sensor 4 at that time, but instead of this, the output from the liquid level sensor 4 The signal S may be frequency-analyzed to calculate the natural frequency F, and then the propagation time T may be indirectly calculated by the following equation (E).

T = 1 / F (E)

Here, when the wave generated on the liquid surface includes a plurality of vibration components, the natural frequency F of the wave composed of the largest vibration component may be employed. Accordingly, even in a situation where it is difficult to accurately calculate the propagation time T of the wave on the liquid surface due to the wave generated on the liquid surface being a wave including a plurality of vibration components, this is accurately calculated. be able to. Accordingly, the liquid level H can be accurately estimated when a wave including a plurality of vibration components is generated.

  In each of the above embodiments, the two periods of the wave generated on the liquid surface are calculated based on the output signal S from the liquid level sensor 4 and this is set as the propagation time 2T. Instead, the N period of the wave is calculated. (N is an integer of 3 or more) is calculated, and this may be set as the propagation time 3T. Alternatively, one wave period may be calculated and used as the propagation time T.

  In each of the above embodiments, the liquid level sensors 4 and 5 that output signals in accordance with the vertical positions of the floats 42 and 52 that float on the liquid surface, that is, the liquid level are illustrated. However, the present invention is not limited to this, and for example, it is possible to change to one that detects the liquid level without contacting the liquid surface using ultrasonic waves or light waves.

  In the first embodiment, the wave propagation velocity V is indirectly calculated by applying the representative length L of the fuel tank 2 and the wave propagation time T to the arithmetic expression (D). However, the wave propagation velocity V may be detected by a different method.

  In each of the above embodiments, when the relational expression (G) is satisfied, the liquid level H1 according to the calculation expression (A) is set as the final liquid level H, and when the relational expression (G) is not satisfied, the calculation expression ( Although the estimation mode in which the liquid level H2 according to B) is the final liquid level is adopted, instead of satisfying the relational expression (G), the calculation expression (B) is always used. The liquid level H2 may be changed to an estimation mode in which the final liquid level H is used.

  In each of the above embodiments, the liquid level H when no wave is generated is estimated by one of the arithmetic expression (A) and the arithmetic expression (B). Is not limited to this. In short, as long as the liquid level is estimated when the wave is not generated on the liquid surface based on the propagation velocity V of the wave generated on the liquid surface, the specific mode can be appropriately changed.

  In each of the above embodiments, the cuboid fuel tank 2 is illustrated, but the shape of the fuel tank is not limited to this, and it may be changed to any shape such as a cylindrical shape. It is.

  In each of the above embodiments, the liquid level sensors 4 and 5 that output signals in accordance with the vertical positions of the floats 42 and 52 that float on the liquid surface, that is, the liquid level, are illustrated. However, the present invention is not limited to this, and can be changed to one that detects the liquid level without contacting the liquid surface using ultrasonic waves or light waves, for example.

  In each of the above embodiments, the liquid level estimation device of the present invention is exemplified as a liquid level estimation device that estimates the liquid level of the fuel stored in the fuel tank 2 of the in-vehicle internal combustion engine. The application target of the liquid level estimation device of the invention is not limited to the liquid level of the fuel stored in the fuel tank 2, but can be any liquid level that is the distance from the bottom surface of the container in which the liquid is stored to the liquid level. Can be changed arbitrarily.

The schematic diagram which shows schematic structure of the liquid level detection apparatus concerning 1st Embodiment of this invention. The schematic diagram which shows the mode of a float and a wave when the wave has generate | occur | produced in the liquid level about the liquid level detection apparatus of the embodiment. The time chart which shows an example of the time change of the output signal by a sensor about the liquid detection apparatus of the embodiment. FIG. 4 is a schematic diagram illustrating a state of a float and a wave when a wave is generated on the liquid level in the liquid level detection device of the embodiment, and (a) a schematic diagram when the liquid level is larger than the amplitude. And (b) A schematic diagram when the liquid level is small compared to the amplitude. The flowchart which shows the specific process sequence about the liquid level estimation process by the liquid level detection apparatus of the embodiment. The schematic diagram which showed schematic structure of the liquid level detection apparatus concerning 2nd Embodiment of this invention. The flowchart which shows the specific process sequence about the abnormality determination process by the liquid level detection apparatus of the embodiment.

Explanation of symbols

  2 ... Fuel tank, 4, 5 ... Liquid level sensor, 42, 52 ... Float, 6 ... Electronic control unit, 8 ... Acceleration sensor.

Claims (12)

In the liquid level estimation device for estimating the liquid level, which is the distance from the bottom surface of the container in which the liquid is stored, to the liquid level,
An apparatus for estimating a liquid level, comprising: estimation means for estimating a liquid level when no wave is generated on the liquid surface based on a propagation speed of the wave generated on the liquid surface. In the liquid level estimation apparatus of Claim 1,
The estimation means calculates the liquid level according to the following equation (A), where the wave propagation velocity is “V”, the gravitational acceleration is “g”, and the liquid level when no wave is generated is “H”. Do

H = V2 / g (A)

The liquid level estimation apparatus characterized by the above-mentioned. In the liquid level estimation apparatus of Claim 1,
The estimation means sets the wave propagation velocity as “V”, the wave amplitude as “h”, the gravitational acceleration as “g”, and the liquid level when no wave is generated as “H” as follows. The liquid level is calculated by the formula (B).

H = (V2 / g) -h (B)

The liquid level estimation apparatus characterized by the above-mentioned. In the liquid level estimation apparatus of Claim 1,
The estimation means sets the wave propagation velocity to “V”, the wave amplitude to “h”, the gravitational acceleration to “g”, and the liquid level when no wave is generated to “H”. Calculate the liquid level by the arithmetic expression (A),

H = V2 / g (A)

Next, using “H” calculated here, it is determined whether or not the term “h / H” in the following equation (C) is less than a predetermined value set as a value smaller than “1”.

V = (H · g (1 + h / H)) 1/2 (C)

When a result indicating that the result is less than a predetermined value is obtained by this determination, “H” according to the arithmetic expression (A) is used as an estimated value of the final liquid level, and a result indicating that the result is greater than or equal to the predetermined value is obtained by the determination. Sometimes “H” is calculated by the following calculation formula (B), and this is used as the final estimated liquid level.

H = (V2 / g) -h (B)

The liquid level estimation apparatus characterized by the above-mentioned. In the liquid level estimation apparatus as described in any one of Claims 1-4,
The estimation means sets the representative length of the container to “L”, and sets the propagation time, which is the time required for the wave on the liquid surface to propagate through the representative length, to “T”. Calculate the wave propagation velocity

V = L / T (D)

The liquid level estimation apparatus characterized by the above-mentioned. In the liquid level estimation apparatus according to claim 5,
The estimation means calculates one cycle of a wave generated on the liquid surface based on an output signal from a sensor that outputs a signal corresponding to an actual liquid level, and sets this as the propagation time. Position estimation device. In the liquid level estimation apparatus according to claim 5,
The estimation means calculates an N cycle (N is an integer of 2 or more) of a wave generated on the liquid surface based on an output signal from a sensor that outputs a signal corresponding to an actual liquid level, and calculates the propagation period. In addition to this, the representative length is multiplied by N, and the propagation speed of the wave is calculated by applying the propagation time and the representative length to the arithmetic expression (D). . In the liquid level estimation apparatus according to claim 5,
The estimation means sets the natural frequency of a wave composed of the largest vibration component in a wave including a plurality of vibration components to “F”, and frequency-analyzes an output signal from a sensor that detects an actual liquid level to perform the natural vibration. The number is calculated, and then the propagation time is calculated by the following equation (E)

T = 1 / F (E)

The liquid level estimation apparatus characterized by the above-mentioned. In the liquid level estimation apparatus as described in any one of Claims 1-8,
In addition to the estimation of the liquid level by the estimation means, the estimation means is further provided with second estimation means for estimating the liquid level when no wave is generated on the liquid surface. A liquid level estimation device. In the liquid level estimation apparatus according to claim 9,
An abnormality has occurred in the estimation device based on the fact that the degree of divergence between the estimated liquid level by the first estimating means and the estimated liquid level by the second estimating means is greater than a predetermined degree. The liquid level estimation apparatus characterized by determining. In the liquid level estimation apparatus according to claim 9 or 10,
The liquid level estimation apparatus, wherein the second estimation means estimates the liquid level by a method different from that of the first estimation means. In the liquid level estimation apparatus according to claim 11,
The liquid level estimation device, wherein the second estimation means estimates the liquid level by smoothing an output signal of a sensor that detects the liquid level.

Images