Object quantity detection device

Abstract

Provided is an object amount detection device which can determine the amount and state of a coagulable liquid object in a container.　The object amount detection device comprises: a container into which a coagulable liquid object can be put; an electrode which is provided across the vertical direction in the container, and can detect a variation in a capacity value accompanying a positional change in the vertical direction of the surface of the liquid object or the surface of the coagulated object; and a determination unit which continuously or intermittently detects, on the basis of the capacity value of the electrode, the position of the liquid surface or the surface of the object in the container, obtains the permittivity of the object from the capacity value of the electrode, and determines the state of the object on the basis of the obtained permittivity.

Description

[Technical field]

[0001] The present invention relates to an apparatus for detecting the amount of an object such as a solidifiable liquid. [Background technology]

[0002] Conventionally, object amount detection devices that detect the amount of water or the like have been known, and the object amount detection devices are installed and used in ice making devices, etc. The conventional ice making device includes an ice making tray made of an insulator, a water supply means that supplies water to the ice making tray, a capacitance sensor having two or more electrodes that are insulated from each other and attached to the ice making tray, a water amount detection unit that detects the amount of water in the ice making tray supplied from the water supply means by a change in capacitance between the electrodes of the capacitance sensor, and an ice making tray driving means that elastically deforms the ice making tray by rotating the ice making tray until the opening of the ice making tray faces downward after detecting that the water in the ice making tray has frozen, and the electrodes of the capacitance sensor are attached to the outside of the ice making tray via an elastically deformable displacement absorbing member in a state in which they are in close contact with the ice making tray but are not joined to the ice making tray (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-207824 A Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional object amount detection devices used in ice making machines detect the amount of water and whether the water is frozen, but cannot determine the degree of frozen state or the amount of water present.

[0005] Therefore, an object of the present invention is to provide an object amount detection device capable of determining the amount and state of a solidifiable liquid object in a container. [Means for solving the problem]

[0006] An object quantity detection device according to an embodiment of the present invention includes a container for holding a solidifiable liquid object, electrodes arranged vertically within the container and capable of detecting a change in capacitance value associated with a change in vertical position of the liquid level of the object or the surface of the solidified object, and a determination unit that continuously or intermittently detects the position of the liquid level or surface of the object within the container based on the capacitance value of the electrodes, determines the dielectric constant of the object from the capacitance value of the electrodes, and determines the state of the object based on the determined dielectric constant. Effect of the Invention

[0007] It is possible to provide an object amount detection device capable of determining the amount and state of a solidifiable liquid object in a container. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a configuration of an object amount detection device 100 according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing an electrostatic sensor 110. [Diagram 3] FIG. 13 is a diagram showing an example of a calculation result of a water surface height. [Figure 4] 10 is a diagram illustrating a difference in capacitance value of the electrostatic sensor 110 due to a difference in the height of the surface of the washer fluid 20A. FIG. [Figure 5A] FIG. 13 is a diagram showing an electrostatic sensor 110 used in a third correction method. [Figure 5B] FIG. 13 is a diagram showing the results of actual measurement using the third correction method. [Figure 6] FIG. 13 is a diagram illustrating a sixth correction method. [Figure 7] 11 is a flowchart showing a process for detecting the height H of the surface of the washer fluid 20A and the frozen state of the washer fluid 20A. FIG. [Figure 8] 11A and 11B are diagrams illustrating a method for correcting a change in capacitance value due to a gradient. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment to which the object amount detection device of the present invention is applied will be described.

[0010] <Embodiment> FIG. 1 is a diagram showing a configuration of an object amount detection device 100 according to an embodiment. FIG. 1 shows a vehicle system 10 in addition to the object amount detection device 100. The vehicle system 10 includes an ECU (Electronic Control Unit) 11 and a power supply 12. The vehicle system 10 is, as an example, a system that controls electronic devices of a vehicle, and the electronic devices may be of any type. For example, the vehicle system 10 may be an ADAS (Advanced Driver-Assistance Systems). The ECU 11 controls the vehicle system 10. The power supply 12 is a power supply that supplies 12V DC power from a power supply source such as a vehicle battery.

[0011] The object amount detection device 100 is a device that detects the amount of washer fluid 20A stored in a tank 20 for washer fluid of a vehicle. If mud, dust, insects, etc. adhere to a camera, optical sensor, etc. mounted on an autonomous vehicle or a vehicle with an automatic driving function equipped with a vehicle system 10 such as ADAS, appropriate images, optical information, etc. cannot be obtained, so a system that washes the camera, optical sensor, etc. with washer fluid has been developed.

[0012] The vehicle system 10 detects the amount of the washer fluid 20A in the tank 20 to determine whether or not the vehicle is in a safe driving state. However, when the outside temperature is low, such as in winter, the washer fluid may freeze. If the washer fluid 20A freezes, it may not be able to be sprayed as a liquid.

[0013] Therefore, the object amount detection device 100 detects the liquid level of the washer fluid 20A or the height position of the surface of the washer fluid 20A when at least a portion of the washer fluid 20A is frozen, and determines whether the washer fluid 20A is frozen.

[0014] Here, the state of the washer fluid 20A refers to either a non-frozen liquid state or a frozen state. The frozen state may be a completely frozen state, or may be a state in which it is difficult to spray the washer fluid 20A from the tank 20. Here, the frozen state refers to a state in which it is difficult to spray the washer fluid 20A from the tank 20.

[0015] In addition, the washer fluid 20A is an example of a liquid substance that can solidify (freeze). In the following, when the washer fluid 20A is described, it is not limited to a liquid state, but may be in a solid state or a state in which the liquid and solid are mixed. In addition, the surface height of the washer fluid 20A refers to the height position of the liquid level of the washer fluid 20A in a liquid state, or the height position of the surface of the washer fluid 20A in a frozen state.

[0016] The object amount detection device 100 includes a control board 101, an electrostatic sensor 110, an IC (Integrated Circuit) chip 120, and an LDO (Low Dropout) 130. As an example, the electrostatic sensor 110, the IC chip 120, and the LDO 130 are mounted on one control board 101, but may be mounted on separate control boards, etc. The control board 101 is a wiring board. The electrostatic sensor 110 will be described with reference to FIG. 2 in addition to FIG. 1. FIG. 2 is a diagram showing the electrostatic sensor 110, and shows a view of the electrostatic sensor 110 viewed from the front direction.

[0017] The electrostatic sensor 110 is configured with electrodes S0, S1, S2, S3, SS1, and SS2 on an insulating substrate (not shown), as shown in FIG. 2, and is attached to the outer surface of the plastic tank 20 with tape, adhesive, or the like. In FIG. 1, the electrostatic sensor 110 is shown in a simplified form with the electrodes SS1 and SS2 omitted. As shown in FIG. 1, the electrostatic sensor 110 is provided on the side wall of the tank 20 so as to extend in the vertical direction. This is to enable detection of the liquid level that changes up and down. The shapes of the electrodes S0, S1, S2, S3, SS1, and SS2 shown in FIG. 2 are the shapes of the surfaces that are placed against the side surface of the tank 20. The electrodes S0, S1, S2, S3, SS1, and SS2 are plate-shaped electrodes.

[0018] The electrodes S0, S1, S2, S3, SS1, and SS2 are capacitively coupled to a metal part (ground part) at ground potential, such as the body of a vehicle in which the vehicle system 10 and the object amount detection device 100 are mounted. In the following, the capacitance values ​​of the electrodes S0, S1, S2, S3, SS1, and SS2 are the electrostatic capacitance values ​​between the electrodes S0, S1, S2, S3, SS1, and SS2 and the ground part of the vehicle.

[0019] The electrodes S0, S1, S2, S3, SS1, and SS2 are connected to the IC chip 120. The electrodes S0, S1, S2, and S3 are provided to detect the vertical position of the liquid surface of the washer fluid 20A and to detect the state of the washer fluid 20A. The electrodes SS1 and SS2 are provided for use in correcting the capacitance values ​​of the electrodes S0, S1, S2, and S3.

[0020] The electrodes S0, S1, S2, and S3 are provided in this order from bottom to top. The electrodes S0, S1, S2, and S3 are arranged against the side surface of the tank 20 and have a shape that is a vertically long rectangle divided by three parallel diagonal straight lines. The bottom and top of the three straight lines pass through the top and bottom vertices of the rectangle, and the center of the length of the middle straight line passes through the center of the rectangle.

[0021] The electrodes S0 and S3 have surfaces that are disposed against the side surface of the tank 20 and have the same shape as each other and are triangular. The triangles of the electrodes S0 and S3 are obtained by dividing a rectangle along its diagonal.

[0022] The electrodes S1 and S2 have the same surface shape that is placed against the side surface of the tank 20, and have a parallelogram shape obtained by combining two electrodes S0 and S3. Therefore, the electrodes S1 and S2 have a shape that includes two triangles obtained by dividing a rectangle along its diagonal.

[0023] The lower end of electrode S0 and the lower end of electrode S1 are equal in height and are located above the lower end of the tank 20. The upper end of electrode S3 and the upper end of electrode S2 are equal in height and are located below the upper end of the tank 20. The lower end of electrode S0 and the lower end of electrode S1 are at a height X0, and the upper end of electrode S3 and the upper end of electrode S2 are at a height X3. When the surface of the washer fluid 20A in the tank 20 is at a height of X0 or more and X3 or less, the surface of the washer fluid 20A always overlaps with two of the electrodes S0 to S3. Therefore, the electrodes S0 and S1 adjacent to each other in the vertical direction are an example of an electrode pair, the electrodes S1 and S2 are an example of an electrode pair, and the electrodes S2 and S3 are an example of an electrode pair. The details of the heights X0 to X3 will be described later. The gaps between the electrodes S0 and S1, between the electrodes S1 and S2, and between the electrodes S2 and S3 are formed small enough to ensure insulation and be negligible in actual measurements.

[0024] The IC chip 120 is a chip component having an AFE (Analog Front End) 120A and an MCU (Micro Computer Unit) 120B. The IC chip 120 is connected to the ECU 11 of the vehicle system 10 via a communication cable 40 for a LIN (Local Interconnect Network), for example.

[0025] The AFE 120A is connected to the electrodes S0, S1, S2, S3, SS1, and SS2 of the electrostatic sensor 110, and converts the capacitance values ​​of the electrodes S0, S1, S2, S3, SS1, and SS2 into digital form and outputs the digitalized values ​​to the MCU 120B. Note that the application of voltage to the electrodes S0, S1, S2, S3, SS1, and SS2 of the electrostatic sensor 110 is performed by applying an AC voltage to a power source (not shown) or a shield electrode (not shown) and capacitively coupling the electrodes to the shield electrode.

[0026] The MCU 120B is realized by a computer including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an input / output interface, an internal bus, and the like.

[0027] MCU 120B has a determination unit 121, a notification unit 122, and a memory 123. Determination unit 121 and notification unit 122 are functional blocks showing the functions of a program executed by MCU 120B. Memory 123 is a functional representation of the memory of MCU 120B. Note that processing units other than determination unit 121 and notification unit 122 of MCU 120B are omitted here.

[0028] The determination unit 121 detects the liquid level of the washer fluid 20A, or the height of the surface of the washer fluid 20A when at least a part of the washer fluid 20A is frozen, as a continuous or intermittent height value. The determination unit 121 also determines whether the washer fluid 20A is frozen based on the detected surface height, the relative dielectric constant of the washer fluid 20A in the frozen state, and the capacitance value of the electrostatic sensor 110. When determining whether the washer fluid 20A is frozen, the difference between the relative dielectric constant of the washer fluid 20A in the liquid state (80.4) and the relative dielectric constant of the washer fluid 20A in the frozen state (4.2) is used.

[0029] When determining the height of the washer fluid 20A, the determination unit 121 determines the height of the center of gravity of the washer fluid 20A and doubles the height of the center of gravity to determine the height of the surface of the washer fluid 20A. When determining the height of the center of gravity of the washer fluid 20A, the determination unit 121 uses heights X0 to X3 shown in FIG.

[0030] X0 is the height of the bottom end of electrode S0. X1 is the height of the vertical center of electrode S1. X2 is the height of the vertical center of electrode S2. X3 is the height of the top end of electrode S3. As an example, if the height from the bottom end to the top end of electrodes S0 to S3 is 300 mm, then X0 = 0 mm, X1 = 100 mm, X2 = 200 mm, and X3 = 300 mm, and the values ​​of X0 to X3 are fixed values.

[0031] The determination unit 121 obtains the height H of the surface of the washer fluid 20A by the following formula (1).

[0032]

number

[0033] In the formula (1), Xn is the above-mentioned X0 to X3, and An is the capacitance of the electrodes S0, S1, S2, and S3.

[0034] Next, the meaning of formula (1) will be explained. First, the capacitance value of each electrode is proportional to the area in the height direction of the liquid or solid that each electrode contacts. And the area in the height direction is proportional to the mass of the liquid or solid within the range of each electrode in the height direction. In other words, the capacitance value of each electrode corresponds to the mass of the range of the liquid or solid that corresponds to each electrode. Generally, the position of the center of gravity of the mass can be calculated by the weighted average of the mass and distance of each element. From these facts, the position of the center of gravity of the liquid or solid can be calculated by the weighted average of the capacitance value (corresponding to the mass) and the distance of each electrode (Σ(Xn×An) / ΣAn). And, since the surface height of the liquid or solid is twice the position of the center of gravity (Σ(Xn×An) / ΣAn), it is possible to calculate the surface height by formula (1).

[0035] Next, the calculation result of the water level height when the washer fluid is actually liquid using the formula (1) will be illustrated, and it will be explained that the water level height can actually be obtained using the formula (1). Figure 3 is a diagram showing an example of the calculation result of the water level height. Table 1 is a diagram showing an example of the calculation result of the water level height.

[0036] Assuming that the water surface is at a height of 250 mm as shown in Figure 3, Example 1 is shown in Table 1. Table 1 also shows the results of four calculations other than Example 1.

[0037] [Table 1]

[0038] The relative permittivity of the washer fluid is equal to that of water and is sufficiently larger than that of air, so the capacitance value measured at each electrode is proportional to the area of ​​the electrode immersed in the liquid. If the capacitance value measured when the entire electrode S0 is immersed in the liquid is 50 pF, then in Example 1, the electrodes S0 and S1 are all immersed in the liquid, and the area of ​​electrode S1 is twice that of electrode S0, so S0 = 50 pF and S1 = 100 pF are measured. In addition, for electrode S2, the capacitance value corresponding to the electrode area of ​​200 mm-300 mm is 50 pF, which corresponds to the electrode area of ​​100 mm-200 mm, and the capacitance value corresponding to the electrode area of ​​200 mm-250 mm is 50 pF x (1-1 / 2 x 1 / 2) = 37.5 pF, and the capacitance value of electrode S2 is 50 + 37.5 = 87.5 Pf. The capacitance of electrode S3 corresponds to an area in the range of 200 mm to 250 mm, and is therefore 50 pF x (1 / 2 x 1 / 2) = 12.5 pF.

[0039] Then, by calculating the water level using formula (1) from the measured values ​​of each electrode, we get H = 2 x (0 x 50 + 100 x 100 + 200 x 87.5 + 300 x 12.5) / (50 + 100 + 87.5 + 12.5) = 250 mm, which matches the assumed water level height in Example 1. In this way, the liquid level can be calculated from the capacitance value of each electrode.

[0040] Similarly, Table 1 shows an example of the capacitance values ​​of each electrode obtained by changing the assumed water surface height, and the calculation results of the water surface obtained from the capacitance values ​​of each electrode. As is clear from Table 1, the assumed water surface height and the water surface height calculated from the capacitance values ​​match, confirming that it is possible to obtain the water surface height from equation (1). Even if the dielectric constant changes, the capacitance value is proportional to the dielectric constant, so as is clear from equation (1), the calculated value of H itself does not change. In addition, when the capacitance values ​​of electrodes S1, S2, and S3 in equation (1) are all 0, the denominator becomes 0, but in that case the water level height is considered to be 0.

[0041] Furthermore, the determination unit 121 determines whether the washer fluid 20A is frozen or liquid based on the detected surface height, the capacitance value of the electrostatic sensor 110, and the relative dielectric constant of the washer fluid 20A in a frozen state or in a liquid state, based on the following formula (2). The coefficient C is set in consideration of the relative dielectric constant of the washer fluid 20A in a liquid state and the relative dielectric constant of the washer fluid 20A in a frozen state. The value of the coefficient C may be set by determining the degree to which the washer fluid 20A becomes difficult to spray, depending on the shape, capacity, etc. of the tank 20. That is, since the capacitance value is proportional to the dielectric constant, if the capacitance value to be measured according to the surface height is small and formula (2) is established, the dielectric constant is considered to be low, and the determination unit 121 determines that the washer fluid 20A is frozen.

[0042] The relative dielectric constant of water is 80.4, and that of ice is 4.2, and the relative dielectric constants of the washer fluid 20A in its liquid and frozen states are also equivalent to these values. As such, since the relative dielectric constants in the liquid and frozen states differ greatly, by appropriately setting the coefficient C, it is possible to easily determine whether the washer fluid 20A is frozen.

[0043]

number

[0044] Similarly, it is also possible to determine whether the capacitance value to be measured according to the surface height is larger than that of the frozen state and to determine whether the liquid state is present. Also, by appropriately determining the threshold value, it is possible to determine the intermediate state from liquid to solid, such as a sherbet-like state.

[0045] The notification unit 122 notifies the ECU 11 of the vehicle system 10 of data representing the height H of the surface of the washer fluid 20A calculated by the determination unit 121. In addition, when the determination unit 121 determines that the washer fluid 20A is frozen, the notification unit 122 notifies the ECU 11 of the vehicle system 10 of data representing that the washer fluid 20A is frozen.

[0046] The memory 123 stores data such as the capacitance values ​​of the electrodes S0, S1, S2, S3, SS1, and SS2, X0 to X3, and the height H of the surface of the washer fluid 20A. The memory 123 stores data on the height H previously obtained and data on past judgment results, etc., in order to obtain a moving average of the height H and to refer to the judgment results for the past 5 seconds for the purpose of judging whether the liquid is frozen continuously.

[0047] The LDO 130 is connected to the power supply 12 of the vehicle system 10 via a power cable 30. The LDO 130 is a regulator and a power supply IC that can output a constant voltage lower than the input voltage. The LDO 130 reduces the voltage of the DC power supplied from the power supply 12 of the vehicle system 10 from 12 V to 5 V and supplies the reduced voltage to the MCU 120B.

[0048] Next, the correction will be described. Note that the correction is not always necessary.

[0049] <First correction method> First, the first correction method will be described. As mentioned above, the height of the water level can basically be calculated by formula (1). However, in formula (1), the denominator is the measured value of each electrode. Therefore, when all the measured values ​​of each electrode are in a small range, that is, when the water level is low, there is a problem that the error between the calculated value of the surface height and the actual water surface height becomes large. This becomes an issue when high-precision detection is required even when the water level is low. One of the causes is the capacitance value C2 caused by the water present below the measurement range where the sensor is installed. That is, the capacitance value of each electrode should be zero below the measurement range where the sensor is installed, but in reality, the capacitance value C2 caused by the water below the measurement range is measured. For these reasons, the capacitance value used when actually calculating the water level needs to be the value obtained by subtracting C2 from the measured measurement value. As mentioned above, the case where correction is performed on electrode S0 for correction in the range where the water level is low will be described, but a similar correction may be performed on electrode S1. Below, the explanation will be given using FIG. 4.

[0050] 4 is a diagram for explaining the difference in capacitance value of the electrode S0 of the electrostatic sensor 110 due to the difference in the height of the surface of the washer fluid 20A. Note that the electrodes S1, S2, S3, SS1, and SS2 are omitted from the illustration. In the example shown in FIG. 4(A), the vertical distance from the ground GND to the tank is 20 mm, the vertical distance from the bottom of the tank 20 to the lower end of the electrode S0 is 20 mm, and the vertical distance from the lower end to the upper end of the electrode S0 is 100 mm. This is also true in FIG. 4(B) and FIG. 4(C).

[0051] In FIG. 4(A), the tank 20 does not contain washer fluid 20A. In this case, the capacitance value C1 between the electrode S0 and the ground section GND, ignoring the thickness of the tank 20, can be considered to be equal to the capacitance value Ca0 when air exists between the electrode S0 and the ground section GND, and can be approximated by Ca0=1×ε0×S / 140. The value 1 multiplied by ε0 is the relative dielectric constant of air. S is the surface area of ​​the electrodes S0 to S3 of the electrostatic sensor 110. 140 indicates the distance from GND to the electrode S0.

[0052] In FIG. 4B, the surface height of the washer fluid 20A (in a liquid state) contained in the tank 20 is the same height as the lower end of the electrode S0. In this case, the capacitance value C2 between the electrode S0 and the ground section GND is the sum of the capacitance value Ca1 of the portion above the washer fluid 20A, the capacitance value Cw of the portion inside the washer fluid 20A, and the capacitance value Ca2 of the portion between the tank 20 and the ground section GND. It can be approximated as Ca1=1×ε0×S / 100, Cw=80.4×ε0×S / 20, and Ca2=1×ε0×S / 20. 80.4, which is obtained by multiplying Cw by ε0, is the relative dielectric constant of the washer fluid 20A in a liquid state.

[0053] In Fig. 4(C), the surface height of the washer fluid 20A (in a liquid state) contained in the tank 20 is equal to the upper end of the electrode S0. In this case, the capacitance value C3 between the electrode S0 and the ground section GND is the sum of the capacitance value Cw of the inside of the washer fluid 20A and the capacitance value Ca2 of the portion between the tank 20 and the ground section GND. It can be approximated as Cw = 80.4 x ε0 x S / 120 and Ca2 = 1 x ε0 x S / 20.

[0054] From the above, the ratio of the capacitance value C1 between the electrode S0 and the ground section GND in the state shown in Figure 4(A), the capacitance value C2 between the electrode S0 and the ground section GND in the state shown in Figure 4(B), and the capacitance value C3 between the electrode S0 and the ground section GND in the state shown in Figure 4(C) is 100:116:651.

[0055] When the surface of the washer fluid 20A is higher than the lower end of the electrode S0, it is considered that the change in the capacitance value according to the water level of the washer fluid 20A can be appropriately detected, but when the surface of the washer fluid 20A is lower than the lower end of the electrode S0, the washer fluid 20A and the electrode S0 do not overlap in the height direction, so it is considered that the error in the value measured at the electrode S0 will be large, and the error in the water level calculated by the formula (1) will also be large. For this reason, here, a correction is performed when the capacitance value measured at the electrode S0 becomes equal to or greater than the capacitance value when there is no water in the tank 20.

[0056] Specifically, if the capacitance value of C1 is k×100 (k is a constant) F, C2 is k×116F, and C3 is k×651F. Here, C3 is 500pF because it is the maximum capacitance value measured at the electrode S0. Therefore, in the case of this embodiment, k=0.77, C1=77pF, C2=89pF, and C3=500pF. If the capacitance value of the electrode S0 is greater than or equal to C1 and less than or equal to C2, that is, if the electrode S0 is at the same height as the lower end of the electrode S0 from a state in which the washer fluid 20A is not present, the measured value is subtracted, and the capacitance value of the electrode S0 is corrected to zero. If the value of the electrode S0 is greater than C2 and less than or equal to C3, that is, if the washer fluid 20A is at the same height as the lower end of the electrode S0 from a state in which the washer fluid 20A is at a height above the upper end of the electrode S0, the measured value of the electrode S0 is corrected by subtracting C2.

[0057] If the measured value of electrode S0 is equal to or less than C2, the value may be corrected to zero, and if it exceeds C2, the value may be corrected by subtracting C2. A similar correction may be made for electrode S1. If the value of electrode S0 is greater than C2 and equal to or less than C3, simply subtracting C2 results in a maximum capacitance value of C3-C2. Therefore, if the value of electrode S0 exceeds C2, a correction may be made by subtracting C2 and then multiplying by C3 / (C3-C2). The water level is then calculated using the corrected capacitance value measured in this way, using equation (1), and the frozen state of the washer fluid is determined using equation (2).

[0058] <Second correction method> Next, a second correction method for when the water level is low will be described. In this correction method, the electrode is extended below the water level measurement area. That is, in the example shown in Fig. 4(A) to Fig. 4(C), the vertical distance from the bottom of the tank 20 to the lower end of the electrode S0 is 20 mm, and no electrode exists between them, but the electrode S0 is extended and provided in this range as well. In this way, the capacitance value of the electrode S0 can be increased even if the surface of the washer fluid 20A is located 20 mm from the bottom of the tank 20 as shown in Fig. 4(B). Then, the surface of the washer fluid from the bottom of the tank 20 is obtained, and 20 mm is subtracted from the obtained surface height to obtain the water surface height from the actual X0. In this way, the measurement accuracy in the water level measurement area can be improved.

[0059] <Third correction method> Next, a third correction method for when the water level is low will be described. The third correction method is similar to the second correction method in that electrodes are actually provided, whereas the second correction method is performed by calculation without actually providing electrodes. Figure 5A is a diagram showing an electrostatic sensor 110 used in the third correction method.

[0060] Specifically, electrodes S01 and SX having the same shape as electrodes S1 and S0 at height X0-X1 as shown in FIG. 5A are virtually provided, and the capacitance value of electrode S01 calculated corresponding to the washer fluid from height XA to height X0 is added to the actual measured value of electrode S0. Also, the capacitance value of electrode SX corresponding to the washer fluid from height XA to height X0 is calculated. Then, using equation (1), the surface height from height XA is calculated. Then, the height from height XA to height X0 is subtracted from the calculated surface height to determine the surface height from the actual height X0. In this way, the denominator of equation (1) can be made large in the water level measurement area, thereby improving the measurement accuracy.

[0061] Figure 5B is a diagram showing the results of actual measurements using the third correction method. In Figure 5B, the horizontal axis shows the actual water level, and the vertical axis shows the calculated water level calculated from the measured electrode data. The thin solid lines show ideal values ​​where the calculated value matches the actual water level, the dotted line shows the calculated water level without correction, and the thick solid line shows the result of calculating the water level using the third correction method. In the area where the water level is low, the actual water level value and the calculated value almost matched.

[0062] <The fourth correction method> As a fourth correction method, gamma correction may be performed on the capacitance value with an index greater than 1, such as 2, and a small capacitance value may be corrected to be treated as a smaller value than a large capacitance value to obtain the water level. In this way, the influence of the electrodes in the range where the washer fluid is present becomes greater. In this case, the gamma correction may be applied only to the range where the water level is low, rather than being applied to the measurement of the surface height of the entire measurement range.

[0063] <Fifth correction method> Next, each electrode will show a predetermined value even when there is no washer fluid due to the influence of stray capacitance, etc., which will result in an error in calculations, so we will explain the fifth correction method as a correction method for this.

[0064] In the fifth correction method, when the value of the electrode Sn is equal to or less than a predetermined value, the values ​​of the electrodes S(n+1), S(n+2), and S(n+3) are all corrected to zero. In other words, when the value of the electrode Sn is equal to or less than a predetermined value, the surface is located near the lower end of the electrode Sn, and it can be determined that the electrodes S(n+1), S(n+2), and S(n+3) located above the electrode Sn are not immersed in the washer fluid. By correcting the capacitance value to zero, the influence of the capacitance value measured in the absence of washer fluid can be reduced.

[0065] <6th correction method> Next, a sixth correction method having the same purpose as the fifth correction method will be described. The sixth correction method uses an electrostatic sensor 210 shown in Fig. 6. Fig. 6 is a cross-sectional view of the electrostatic sensor 210 for explaining the sixth correction method.

[0066] Note that the same members as those of the electrostatic sensor 110 are denoted by the same reference symbols. In reality, the electrodes S0 to S3, SS1, and SS2 are separate members, and the reference electrode SR also consists of multiple parts, but in Fig. 6 they are illustrated as one member. The reference electrode SR is an example of a reference electrode. The electrostatic sensor 210 differs from the electrostatic sensor 110 in that a reference electrode SR and a shield electrode SS are provided, and this point will also be included in the following description.

[0067] The electrodes S0 to S3, SS1, and SS2 are formed on the same surface of the substrate B and are arranged facing the tank 20, similarly to the electrostatic sensor 110. The reference electrode SR has the same shape as the electrodes S0 to S3, SS1, and SS2, and is provided on the surface opposite to the surface on which the electrodes S0 to S3, SS1, and SS2 are provided. The shield electrode SS is provided between the electrodes S0 to S3, SS1, and SS2 and the reference electrode SR in the thickness direction of the substrate B. The shield electrode SS is connected to the ground or is AC driven, and is capacitively coupled with the electrodes S0 to S3, SS1, and SS2 and the reference electrode SR. For this reason, the capacitance values ​​of the electrodes S0 to S3, SS1, and SS2 are affected by the washer fluid 20A in the tank 20, but the electrode SR is not affected by the washer fluid 20A.

[0068] Then, a correction is performed by subtracting the capacitance value of the reference electrode portion having the same shape as each electrode from the capacitance values ​​of the electrodes S0 to S3, SS1, and SS2. This makes it possible to determine the capacitance value due to the presence of the washer fluid 20A. In other words, even when there is no washer fluid, a predetermined capacitance value is measured, and although the value changes with temperature changes, the influence of these changes can be reduced. The corrected value is then applied to equation (1) to determine the water level, and equation (2) is used to determine whether the water is frozen.

[0069] In this embodiment, the reference electrode has the same shape as the electrodes S0 to S3, SS1, and SS2, but is not limited thereto and may be, for example, a single electrode with a different area. In that case, the area is converted to the area of ​​the electrodes S0 to S3 and subtracted from the measured value.

[0070] In this embodiment, the shield electrode SS is disposed between the reference electrode SR and the electrodes S0 to S3, SS1, and SS2 via the insulating layer of the substrate B, but a shield electrode may also be disposed on the surface of the reference electrode SR opposite the electrodes S0 to S3, SS1, and SS2 via the insulating layer of the substrate B. In other words, the reference electrode SR may be sandwiched between two shield electrodes via the insulating layer of the substrate.

[0071] In addition, after the correction is performed using the electrostatic sensor 210, the washer fluid 20A below the lower end of the electrode shown in FIG. 4 may be corrected.

[0072] It is possible to combine one of the first to fourth corrections with one of the fifth to sixth corrections, in which case any of the fifth to sixth corrections is performed on the capacitance value of each electrode, and then any of the first to fourth corrections is performed. In addition, if a combination is possible, the corrections may be appropriately combined.

[0073] 7 is a flowchart showing a process for detecting the height H of the surface of the washer fluid 20A and the frozen state in the electrostatic sensor 110 or the electrostatic sensor 210. This process is performed by the determination unit 121. Note that although the process contents of the determination unit 121 in the electrostatic sensor 110 or the electrostatic sensor 210 are different, the same processes are denoted by the same reference numerals.

[0074] When the determination unit 121 starts the process, it performs a power-on reset process (step S1). Specifically, it performs processes such as resetting values ​​in the ROM and RAM.

[0075] The determination unit 121 sets a count value i, which indicates the number of times the height H has been detected, to 0 (i=0) (step S2).

[0076] The determination unit 121 detects the capacitance values ​​of the electrodes S0 to S3 (step S3).

[0077] In the case of the electrostatic sensor 110, the determination unit 121 performs the fifth correction described above, and further performs the first correction described above, that is, when the capacitance value of S0 is 77 pF to 89 pF, the value is set to zero, and when it exceeds that, 89 pF is subtracted (step S4). At this time, as described above, in the first correction, a similar correction may also be performed for the electrode S1.

[0078] In the case of the electrostatic sensor 210, the sixth correction described above is performed, and then the first correction described above is performed (step S4).

[0079] As described above, the correction itself is not necessarily required depending on the required accuracy, and the correction may be performed by using one or a combination of the above-mentioned correction methods.

[0080] The determination unit 121 calculates the height H according to the formula (1) (step S5). Calculating the height H according to the formula (1) is synonymous with detecting the height H.

[0081] The determination unit 121 calculates a moving average of the height H calculated in step S5 and the heights H calculated over the past 19 times (step S6). The moving average can be found by the following formula (3), where j is an integer from 1 to 20 indicating each of the 20 heights H from the current step S5 to the 19th step S5 before. Also, N indicates the number of values ​​of height H, where N=20.

[0082]

number

[0083] In step S6, the determination unit 121 detects the surface height H of the washer fluid 20A multiple times over time, and determines the average value of the heights H detected multiple times as the surface height H of the washer fluid 20A.

[0084] The determination unit 121 increments the count value i (i=i+1) (step S7).

[0085] The determination unit 121 waits for 250 ms (step S8).

[0086] The determination unit 121 determines whether i≧20 (step S9), that is, whether the height H has been detected 20 times or more.

[0087] If the determination unit 121 determines that i≧20 is not satisfied (S9: NO), the flow returns to step S3. This is to repeatedly detect the height H. If i is less than 20, the determination unit 121 skips the process of step S6. This is because the data on the height H required to calculate the moving average has not been collected.

[0088] If it is determined in step S9 that i≧20 (S9: YES), the determination unit 121 determines whether or not the data is frozen according to equation (2) (step S10).

[0089] When the determination unit 121 determines that the data is not frozen (S10: NO), the determination unit 121 sets the counter value f used for the freeze determination to 0 (step S11). That is, f=0.

[0090] The determination unit 121 causes the notification unit 122 to notify the ECU 11 of the vehicle system 10 of the moving average value of the height H calculated in step S6 (step S12). When only the height H is notified, it indicates that no freezing has occurred, but data indicating that no freezing has occurred (non-freezing information) may also be notified together with the height H. When the determination unit 121 finishes the process of step S12, it returns the flow to step S3.

[0091] If it is determined in step S10 that the data is frozen (S10: YES), the determination unit 121 increments the counter value f (step S13). That is, f=f+1.

[0092] The determination unit 121 determines whether it has been determined that the image is frozen (S10: YES) 20 times in a row since step S10 19 times before the current step S10 (step S14). Since the determination is repeated every 250 ms, the process of step S14 is a process of determining whether it has been determined that the image is frozen (S10: YES) for the past 5 seconds.

[0093] If the determination unit 121 determines that the content has not been frozen 20 times in succession (S10: YES) (S14: NO), the flow proceeds to step S12.

[0094] If the determination unit 121 determines in step S14 that the washer fluid 20A has frozen 20 times consecutively (S10: YES) (S14: YES), it determines that the washer fluid 20A in the tank 20 has frozen, and causes the notification unit 122 to notify the ECU 11 of the vehicle system 10 of the moving average value of the height H calculated in step S6 and data indicating that freezing has occurred (freezing information) (step S15). This ends the series of processes.

[0095] As described above, the determination unit 121 obtains the surface height H of the washer fluid 20A based on the height of the center of gravity of the washer fluid 20A using the formula (1). In addition, the determination unit 121 determines whether the washer fluid 20A is frozen based on the detected surface height, the relative dielectric constant of the washer fluid 20A in a frozen state, and the capacitance value of the electrostatic sensor 110 using the formula (2).

[0096] Therefore, it is possible to provide an object amount detection device 100 capable of determining the amount and state of a solidifiable liquid object (washer fluid 20A) in a container (tank 20).

[0097] In addition, since the electrodes S0 to S3 are plate electrodes having an electrode pair with a triangular surface shape obtained by dividing a rectangle diagonally, which is arranged against the side surface of the tank 20, no matter what the height of the surface of the washer fluid 20A is, two of the electrodes S0 to S3 adjacent in the vertical direction (electrode pairs) always overlap with the surface. For this reason, if there were a range where the surface did not overlap with the electrodes, there would be a portion where the detection value hardly changes, but since the surface always overlaps with the electrodes, there is no unchanged portion in the detection value of the water level, and it is possible to decrease the detection value of the water level as the water level decreases, and the water level can be measured with high accuracy.

[0098] The determination unit 121 detects the surface of the washer fluid 20A based on a weighted average of the capacitance values ​​of the electrodes S0 to S3, and determines the state of the washer fluid 20A based on the height H of the detected surface of the washer fluid 20A, the capacitance value of the electrostatic sensor 110, and a coefficient C based on the relative dielectric constant of the washer fluid 20A in a liquid state or a solid state. Since the surface position is determined by a weighted average of the capacitance values ​​and heights of the multiple electrodes, the surface height can be measured even if the dielectric constant is different between a solid and a liquid. The dielectric constant can be specified from the determined height and capacitance value. Since the relative dielectric constant of water (80.4) and the relative dielectric constant of ice (4.2) are significantly different, the state of the washer fluid 20A can be detected with high accuracy by utilizing the difference in the relative dielectric constant.

[0099] Furthermore, since the electrodes S0 to S3 have multiple electrode pairs, and the multiple electrode pairs are arranged in the vertical direction, the height H and the state of the washer fluid 20A can be determined even if the surface height of the washer fluid 20A changes continuously over a fairly wide range in the vertical direction.

[0100] In addition, the surface height is calculated by subtracting the capacitance value of the washer fluid corresponding to the lower end of the electrostatic sensor. Therefore, even if the amount of the washer fluid 20A is small, the surface height H of the washer fluid 20A can be detected with high accuracy.

[0101] In addition, the electrodes S0 to S3 are arranged facing the tank 20, and a reference electrode SR is provided on the opposite side via a shield electrode, and the capacitance value of the reference electrode SR is subtracted from the capacitance value of the electrodes S0 to S3 to perform zero correction and calculate the surface height. Therefore, the surface height H of the washer fluid 20A can be detected with high accuracy.

[0102] In addition, the judgment unit 121 detects the surface height H of the washer fluid 20A multiple times over time, and takes the average value of the height H detected multiple times as the surface height H of the washer fluid 20A, thereby suppressing the effects of noise, etc. that may be contained in the capacitance value, and detecting the height H with high accuracy.

[0103] In addition, when the determination unit 121 determines that the state of the washer fluid 20A is a frozen state, the notification unit 122 notifies the ECU 11 of the vehicle system 10 of freezing information indicating the frozen state, so that it is possible to notify the ECU 11 of the vehicle system 10 of whether the washer fluid 20A can be used. In particular, when mud, dust, insects, and the like attached to a camera, an optical sensor, and the like mounted on an autonomous vehicle or a vehicle with an automatic driving function equipped with a vehicle system 10 such as an ADAS is washed with the washer fluid 20A, washing becomes impossible if the washer fluid 20A freezes, so that it is possible to provide an object amount detection device 100 that can contribute to safe operation of the vehicle.

[0104] In this embodiment, the process of measuring the surface position is started at a predetermined time interval, but it may be started immediately after the pump that sprays the washer fluid starts operating. Alternatively, it may be measured at a long period and then at a short period after the pump that sprays the washer fluid starts operating. In this case, the measurement is performed at the timing when the surface changes, so that the measurement can be performed with high accuracy and power consumption can be reduced.

[0105] In addition, when the vehicle is temporarily stopped and idling is stopped, the water level measurement period may be shortened or may not be performed at all. In this case, power consumption can be reduced when the amount of power generation is low.

[0106] Also, when the amount of noise measured by the sensor is small, it may be determined that the vehicle is stopped and the water level measurement cycle may be reduced or may not be performed at all.

[0107] When the vehicle is traveling, the vehicle may tilt with respect to the horizontal plane, and in such a case, the tank 20 may also tilt, and the surface of the washer fluid 20A may tilt with respect to the electrostatic sensor 110. The change in capacitance value due to such tilt may be corrected using the electrodes SS1 and SS2.

[0108] Fig. 8 is a diagram for explaining a method for correcting a change in capacitance value due to tilt. Fig. 8 shows a state in which the tank 20 is tilted and the electrodes SS1 and SS2 are immersed in the washer fluid 20A at different positions. The electrodes SS1 and SS2 are examples of tilt detection electrodes.

[0109] In this case, the gradient D (%) due to the inclination of the tank 20 can be calculated by the following formula (4).

[0110]

number

[0111] The capacitance values ​​of the electrodes S0 to S3 may be corrected using such gradient D, and the height H of the surface of the washer fluid 20A may be obtained based on the corrected capacitance values. Furthermore, the state of the washer fluid 20A may be determined using the height H of the surface of the washer fluid 20A based on the corrected capacitance values.

[0112] Specifically, the gradient D is calculated based on the formula (4), a section of the electrodes S0 to S3 between the electrodes SS1 and SS2 in which the surface of the washer fluid 20A is located is corrected based on the gradient D, and the height H of the surface of the washer fluid 20A is calculated based on the corrected capacitance value. Then, the state of the washer fluid 20A is determined using the height H of the surface of the washer fluid 20A based on the corrected capacitance value.

[0113] In the above explanation, multiple electrodes were arranged in the vertical direction, and the surface height of the washer fluid 20A was continuously measured over a relatively wide range in the vertical direction. However, for example, detection electrodes may be provided at intervals of 10 mm, and the height may be measured every 10 mm, i.e., intermittent height may be measured.

[0114] Although an object amount detection device according to an exemplary embodiment of the present invention has been described above, the present invention is not limited to the specifically disclosed embodiment, and various modifications and changes are possible without departing from the scope of the claims.

[0115] This international application claims priority to Japanese patent application No. 2022-028511, filed on February 25, 2022, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0116] 10 Vehicle Systems 20. Tank 20A Windshield Washer Fluid 100 Object quantity detection device 110 Electrostatic Sensor S0, S1, S2, S3, SS1, SS2 electrodes 120 IC chips 120B MCU 121 Judgment section 122 Notification Department

Claims

1. A container for containing a solidifiable liquid object; an electrode provided in the container in a vertical direction and capable of detecting a change in capacitance value associated with a change in the vertical position of the liquid level of the object or the surface of the solidified object; a determination unit that continuously or intermittently detects the position of the liquid level or surface of the object in the container based on the capacitance value of the electrodes, determines the dielectric constant of the object from the capacitance value of the electrodes, and determines the state of the object based on the determined dielectric constant; Including, the electrode is a plate-shaped electrode having a plurality of electrode pairs, the shape of the surface of which is arranged against the side surface of the container and has a triangular portion obtained by dividing a rectangle diagonally; The determination unit detects the position of the liquid level or surface of the object based on a weighted average of the capacitance values ​​and positions of the multiple electrode pairs, and determines the state of the object based on the detected position of the liquid level or surface of the object and the dielectric constant of the object in a liquid state or a solid state.

2. The object amount detection device according to claim 1 , wherein the plurality of electrode pairs are arranged in a vertical direction.

3. The electrode further includes a reference electrode disposed on the opposite side of the container to the electrode via a shield electrode; The object amount detection device according to claim 1 , wherein the determination unit corrects the capacitance value of the electrode pair based on a capacitance value of the reference electrode.

4. 3 . The object amount detection device according to claim 2 , wherein when one of the capacitance values ​​of the plurality of electrode pairs exceeds a predetermined value, the determination unit sets a capacitance value of an electrode positioned above the electrode pair to zero.

5. The object amount detection device according to claim 2 , wherein the determination unit corrects the capacitance value of the electrode pair when a position of a liquid level or a surface of the object is equal to or lower than a predetermined height.

6. The object amount detection device according to claim 2 , wherein the determination unit calculates the water level height by including in the calculation a capacitance value of an electrode pair virtually provided below the plurality of electrode pairs.

7. 2. The object amount detection device according to claim 1, wherein the determination unit detects a position of the liquid level or surface of the object a plurality of times over time, and determines an average value of the positions of the liquid level or surface of the object detected a plurality of times as the position of the liquid level or surface of the object.

8. The object amount detection device according to claim 1 , further comprising a notification unit that, when the determination unit determines that the object is in a frozen state, notifies an external device of information representing the frozen state.

9. The object amount detection device according to claim 8 , wherein the object is a windshield washer fluid of a vehicle.

Images