Sensor device

Abstract

To provide a technique for determining an amount of air ions attracted to a surface of a vehicle.SOLUTION: A sensor device 1 provided herein has a measurement electrode 10 mounted on a surface of a vehicle 90. A measurement unit 20 measures a current flowing through the measurement electrode 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sensor device mounted on a vehicle. [Background technology]

[0002] Patent Document 1 discloses an ion detection device that has a measurement unit that measures the potential of a collecting electrode that collects ions in the air, and detects ions based on the potential measured by the measurement unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4411356 Summary of the Invention [Problem to be solved by the invention]

[0004] The driving performance of a vehicle changes depending on the electrified state of the vehicle while it is running. The present inventors have recognized that it is desirable to obtain the amount of air ions attracted to the vehicle surface in order to evaluate and improve the driving performance of the vehicle.

[0005] An object of the present invention is to provide a technique that can obtain the amount of air ions attracted to the vehicle surface. [Means for solving the problem]

[0006] In order to solve the above problem, a sensor device according to one aspect of the present invention includes a measurement electrode attached to a surface of a vehicle, and a measurement unit that measures a current flowing through the measurement electrode. [Effects of the Invention]

[0007] According to the present invention, a technique can be provided that can obtain the amount of air ions attracted to the vehicle surface. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram schematically illustrating a vehicle equipped with a sensor device according to a first configuration example of an embodiment. [Figure 2] FIG. 10 is a diagram illustrating a sensor device according to a second configuration example. [Figure 3] FIG. 10 is a diagram illustrating a sensor device according to a third configuration example. [Figure 4] FIG. 10 is a diagram illustrating a sensor device according to a fourth configuration example. [Figure 5] FIG. 10 is a diagram schematically illustrating a vehicle equipped with a sensor device according to a fifth configuration example. [Figure 6] FIG. 10 is a diagram illustrating a sensor device according to a sixth configuration example. [Figure 7] Figure 7(a) is a diagram showing an example of a regression line derived by the derivation unit of Figure 6 for each electric field strength between the vehicle surface and the ground, and Figure 7(b) is a diagram showing the current value when the voltage is zero for each regression line of Figure 7(a). [Figure 8] FIG. 10 is a diagram illustrating a sensor device according to a seventh configuration example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Experimental findings have shown that attaching self-discharge static eliminators such as aluminum tape or Teflon (registered trademark) tape to parts of the doors of a vehicle changes the handling stability when going over bumps or during steering response. This is thought to be because the negative charge generated on the wheels due to friction between the wheels and the road surface is transferred to the vehicle body, causing the vehicle to be charged to a negative potential relative to the ground, and many positive air ions contained in the air are attracted to the vehicle surface and neutralize the negative charge on the vehicle, but this neutralization changes the aerodynamic characteristics such as pressure fluctuations on the vehicle surface.

[0010] The inventors recognized that supplying a negative charge to the vehicle surface can attract air ions to the vehicle surface, which have the effect of rectifying the airflow around the vehicle. Furthermore, the inventors discovered that by obtaining the amount of air ions attracted to the vehicle surface without affecting the airflow around the vehicle, the amount of air ions attracted to the vehicle surface can be adjusted to a desired amount, thereby controlling pressure fluctuations on the vehicle surface and changing the vehicle's driving characteristics. The present embodiment was devised based on this idea, and its specific configuration will be described below.

[0011] 1 schematically shows a vehicle 90 equipped with a sensor device 1 according to a first exemplary configuration of the embodiment. The vehicle 90 may be a vehicle that uses only an internal combustion engine as a driving force source, or may be an electric vehicle that uses an electric motor as a driving force source. The vehicle 90 may be a vehicle driven by a driver, or may be an autonomous vehicle.

[0012] Each of the plurality of wheels 92 of the vehicle 90 has a tire made of an insulating material such as rubber, and the body of the vehicle 90 is kept insulated from the road surface.

[0013] 1, the sensor device 1 includes a measurement electrode 10 and a measurement unit 20. The sensor device 1 can also be called a vehicle surface charge measurement device.

[0014] The measurement electrode 10 is a conductive foil, such as copper foil, and is attached to the surface of the vehicle 90. The front surface of the measurement electrode 10 contacts the air surrounding the vehicle 90. The back surface of the measurement electrode 10 faces the front surface of the vehicle 90. The thickness of the measurement electrode 10 is thin enough not to disturb the airflow around the vehicle 90 while the vehicle 90 is moving, and can be appropriately determined through experiments or simulations. The measurement electrode 10 may be a thin plate- or sheet-like electrode, or a low-profile protruding electrode, as long as it does not disturb the airflow. In FIG. 1, the thickness of the measurement electrode 10 is exaggerated for clarity. The measurement electrode 10 is, for example, rectangular in plan view. The shape of the measurement electrode 10 in plan view is not particularly limited and may be, for example, circular, elliptical, polygonal, or the like.

[0015] In the illustrated example, the measurement electrode 10 is attached to the windshield of a vehicle 90. The position where the measurement electrode 10 is attached is the position on the surface of the vehicle body where air ions 70 are attracted, and can be determined appropriately through experiments or simulations. Other examples of the position where the measurement electrode 10 is installed include the engine hood, side windows, rear window, side doors, and roof.

[0016] The measurement electrode 10 is connected to one end of a measurement unit 20 via an electric wire. The other end of the measurement unit 20 is connected to a ground 30 of the vehicle 90.

[0017] As described above, negative charges generated on the wheels 92 due to friction between the wheels 92 and the road surface are transferred to the vehicle body, and positive air ions 70 in the air are attracted to the vehicle surface. The measurement electrode 10 receives charges from the air ions 70 that are attracted to the vehicle surface and reach the measurement electrode 10, causing a current to flow. When the measurement electrode 10 receives a positive charge, a current flows from the measurement electrode 10 to the ground 30.

[0018] The measurement unit 20 includes an ammeter and measures the current flowing between the measurement electrode 10 and the earth 30. Because the current generated by the air ions 70 on the vehicle surface is extremely small, it is desirable to use a minute ammeter. The measurement unit 20 can estimate the amount of air ions 70 present on the vehicle surface based on the measured current value and a predetermined calculation formula. The current value measured by the measurement unit 20 is related to the amount of air ions 70 attracted to the vehicle surface, and therefore to the amount of charge on the vehicle surface.

[0019] According to the embodiment, the measurement electrode 10 attached to the surface of the vehicle 90 measures the current that flows when it receives charge from the air ions 70, and the amount of air ions 70 attracted to the surface of the vehicle 90 can be obtained based on the measured current value. Whether the running performance of the vehicle 90 is good or not can be evaluated based on the obtained amount of air ions 70. For example, if the amount of air ions 70 is less than a threshold value, the running performance of the vehicle 90 may be evaluated as poor. Furthermore, based on the obtained amount of air ions 70, it can be estimated whether the amount of charge on the vehicle surface needs to be adjusted, and if so, the amount of charge that should be supplied to the vehicle surface.

[0020] Furthermore, since the measurement electrode 10 is thin and attached along the vehicle surface, it is less likely to affect the airflow around the vehicle surface, and therefore, deterioration of running performance due to the installation of the measurement electrode 10 can be suppressed.

[0021] In the first configuration example, the measurement electrode 10 also attracts air ions that reach the vehicle surface around the measurement electrode 10 and can receive charge from those air ions. However, the area of ​​the range in which air ions can be attracted varies depending on the electric field strength generated in the measurement area. To adjust the amount of charge on the vehicle surface, it is easier to control accurately by using the amount of air ions attracted per unit area to the vehicle surface, i.e., the ion concentration. Therefore, it is more preferable to define the range in which air ions can be attracted, as in the second configuration example below.

[0022] 2 shows a second configuration example of the sensor device 1. The following description will focus on the differences from the first configuration example of FIG.

[0023] As shown in Fig. 2, the sensor device 1 further includes a guard electrode 12. Fig. 2 shows the structures of the measurement electrode 10 and the guard electrode 12 in a plan view. That is, Fig. 2 shows the outline of the shapes of the measurement electrode 10 and the guard electrode 12 as observed from the normal direction of the windshield in Fig. 1.

[0024] The guard electrode 12 is a conductive foil such as copper foil, and is attached to the surface of the vehicle 90 at a distance from the measurement electrode 10 so as to surround the measurement electrode 10. The front surface of the guard electrode 12 is in contact with the air surrounding the vehicle 90. The back surface of the guard electrode 12 faces the front surface of the vehicle 90. The thickness of the guard electrode 12 is approximately the same as the thickness of the measurement electrode 10. The guard electrode 12 has a rectangular frame shape with an opening in the center. The measurement electrode 10 is located in the center of the opening of the guard electrode 12. The guard electrode 12 may have a frame shape such as a circle, an ellipse, or a polygon.

[0025] The guard electrode 12 is electrically connected to the earth 30 without going through the measurement unit 20. The electric wire connecting the measurement electrode 10 and the measurement unit 20 is not connected to the guard electrode 12. Air ions attracted to the vehicle surface outside the guard electrode 12 and onto the guard electrode 12 impart an electric charge to the guard electrode 12, and the resulting current flows from the guard electrode 12 to the earth 30, preventing the amount of air ions at these locations from being measured by the measurement electrode 10. This allows the measurement electrode 10 to measure only the amount of air ions attracted onto the measurement electrode 10 and to the region between the measurement electrode 10 and the guard electrode 12.

[0026] In this way, in the second configuration example, by surrounding the measurement electrode 10 with the guard electrode 12, the range in which the measurement electrode 10 can attract air ions, i.e., the area of ​​the measurement target range, is limited to the inside of the guard electrode 12, and the amount of air ions per unit area attracted to the vehicle surface can be obtained.

[0027] 3 shows a third configuration example of the sensor device 1. The following description will focus on the differences from the second configuration example shown in FIG.

[0028] As shown in Fig. 3, the sensor device 1 further includes an insulating member 14. The insulating member 14 is provided along the inner periphery of the guard electrode 12, is in contact with the guard electrode 12, and is attached to the surface of the vehicle 90 so as to surround the measurement electrode 10 at a distance from the measurement electrode 10. The insulating member 14 insulates the measurement electrode 10 from the guard electrode 12. The insulating member 14 may be any member, such as insulating tape or paint, that has sufficiently high insulation properties against the measurement electrode 10 and is thin enough not to interfere with the airflow around the vehicle.

[0029] The provision of insulating member 14 can prevent the inner peripheral portion of guard electrode 12 from receiving charge from air ions. This prevents charge from air ions attracted to the area between measurement electrode 10 and guard electrode 12 from flowing through guard electrode 12 to earth 30. Therefore, compared to the second configuration example of Fig. 2, measurement electrode 10 can receive charge from air ions within the measurement range more accurately, increasing the amount of charge received by measurement electrode 10 from air ions within the measurement range, and enabling more accurate measurement of the amount of air ions per unit area.

[0030] 4 shows a fourth configuration example of the sensor device 1. The following description will focus on the differences from the third configuration example of FIG.

[0031] As shown in FIG. 4, the sensor device 1 further includes a voltage source 40. The voltage source 40 applies a voltage between the guard electrode 12 and the ground 30. By applying a potential difference between the measurement electrode 10 and the guard electrode 12, air ions of the polarity to be measured within the measurement range can be more efficiently collected toward the measurement electrode 10. This makes it easier for the measurement electrode 10 to receive charge from air ions within the measurement range than in the third configuration example of FIG. 3. This allows the amount of air ions per unit area to be measured more accurately than in the third configuration example. The voltage of the voltage source 40 can be determined appropriately through experiments or simulations.

[0032] When collecting the aforementioned positive ions, the positive electrode of the voltage source 40 is connected to the guard electrode 12 as shown in the figure. On the other hand, when it is necessary to collect negative ions, the negative electrode of the voltage source 40 is connected to the guard electrode 12, and the positive electrode of the voltage source 40 is connected to the earth 30.

[0033] 5 is a schematic diagram of a vehicle 90 equipped with a sensor device 1 according to a fifth configuration example. The following description will focus on the differences from the first configuration example shown in FIG.

[0034] 5, the sensor device 1 further includes a charge adjustment unit 22. The measurement unit 20 supplies the measurement results to the charge adjustment unit 22. The charge adjustment unit 22 adjusts the charge state of the surface of the vehicle 90 based on the current value measured by the measurement unit 20. The charge adjustment unit 22 adjusts the amount of charge on the surface members of the vehicle 90, thereby adjusting the charge state of the surface of the vehicle 90 so that the concentration of air ions drawn into the vehicle surface becomes a value desirable for improving driving stability.

[0035] The charge adjustment unit 22 controls the charge state of the vehicle surface by, for example, using an ionizer to supply ions to the vehicle surface, applying a current or voltage to the vehicle surface to supply an electric charge, or changing the impedance of the body of the vehicle 90 to change the amount of negative charge generated on the wheels during driving that is supplied to the vehicle surface.

[0036] When the measured current value is less than a predetermined first threshold value, the charge adjusting unit 22 supplies charge to the surface member of the vehicle 90 so that the measured current value becomes equal to or greater than the first threshold value.

[0037] If the measured current value is greater than a predetermined second threshold, the charge adjusting unit 22 may supply charge to the surface member of the vehicle 90 so that the measured current value is equal to or greater than the first threshold and less than the second threshold. The range of the current value from the first threshold to the second threshold that provides good driving stability is set in advance through experiments.

[0038] In this way, by adjusting the charge state of the surface of the vehicle 90 according to the measured current value, the charge state of the vehicle 90 can be maintained appropriately, and the concentration of air ions attracted to the vehicle surface can be maintained appropriately, thereby maintaining good driving stability.

[0039] The fifth configuration example may be combined with the second, third, or fourth configuration example. That is, the charge adjusting unit 22 may adjust the charge state of the surface of the vehicle 90 based on the current value measured by the measuring unit 20 in the second, third, or fourth configuration example.

[0040] In the first, second, and third configuration examples, the current value measured by the measurement unit 20 may be on the order of nA or less. Depending on the level of ambient noise, accurate measurement may be difficult due to the influence of noise. In the fourth configuration example, as described above, a potential difference is applied between the measurement electrode 10 and the guard electrode 12 to generate an electric field. This electric field attracts air ions, causing a current to flow through the measurement electrode 10 and be measured. This current corresponds to the amount of ions per unit time. In other words, it can be expressed as I = Q / t. Because this current value is larger than in the first, second, and third configuration examples, it is less susceptible to noise and easier to measure accurately. However, the current value measured in this manner is not the current value due to air ions naturally accumulated on the vehicle surface. The current value when there is no potential difference between the measurement electrode 10 and the guard electrode 12 is the current value due to air ions naturally accumulated on the vehicle surface, and is the desired value. Therefore, it is more preferable to estimate the current value when the voltage is zero based on multiple current values ​​when different voltages are applied to the guard electrode 12, as in the sixth configuration example described below.

[0041] 6 shows a sixth configuration example of the sensor device 1. The following description will focus on the differences from the fourth configuration example of FIG.

[0042] As shown in FIG. 6 , the sensor device 1 further includes a derivation unit 24. The voltage source 40 varies the applied voltage in stages. The derivation unit 24 acquires current values ​​measured by the measurement unit 20 when each of multiple voltages is applied by the voltage source 40. That is, the derivation unit 24 acquires a current value for each voltage applied by the voltage source 40. The derivation unit 24 derives a regression line based on the multiple applied voltage values ​​and the multiple acquired current values, and derives the current value when the voltage on the derived regression line is zero. The regression line is an approximate line obtained by performing regression analysis on multiple pairs of voltage values ​​and current values, and indicates the relationship between voltage and current. Any appropriate regression analysis method may be used. For example, the derivation unit 24 may derive a regression equation for multiple pairs of voltage values ​​and current values ​​using the least squares method.

[0043] The derivation unit 24 is realized by the cooperation of hardware resources and software resources. The hardware resources may include a CPU, GPU, DSP, FPGA, and other LSIs. The software resources may include an operating system, an application program, and the like.

[0044] The voltage applied by the voltage source 40 may be a voltage of either positive or negative polarity, but preferably includes both positive and negative voltages. This is because the regression line can be determined with higher accuracy. The voltage applied by the voltage source 40 does not include 0 V. The voltage applied by the voltage source 40 can be determined appropriately through experiments or simulations so as to obtain a current value that provides relatively high measurement accuracy for the measurement unit 20.

[0045] The current value when the voltage on the derived regression line is zero corresponds to the estimated current value when the voltage applied by the voltage source 40 is zero, and can be considered to be the current value due to air ions naturally accumulated on the vehicle surface.

[0046] Fig. 7(a) shows an example of the regression line derived by the derivation unit 24 in Fig. 6 for each electric field strength between the vehicle surface and the ground, and Fig. 7(b) shows the current value when the voltage is zero for each regression line in Fig. 7(a). The horizontal axis of the graph in Fig. 7(a) represents the voltage applied by the voltage source 40, and the vertical axis represents the current. The horizontal axis of the graph in Fig. 7(b) represents the electric field strength between the vehicle surface and the ground, and the vertical axis represents the current.

[0047] The charged state of the vehicle 90 may change depending on the driving conditions and driving environment of the vehicle 90, and the electric field strength between the vehicle surface of the vehicle 90 and the ground may change. As an example, Figures 7(a) and (b) show experimental results when the electric field strength is set to "zero," "weak," and "strong." Figure 7(a) shows a regression line 100 when the electric field strength between the vehicle surface and the ground is "zero," a regression line 102 when the electric field strength is "weak," and a regression line 104 when the electric field strength is "strong."

[0048] For example, under the condition of "zero" electric field strength, the voltage applied from voltage source 40 is changed to each of a plurality of values ​​in turn, and derivation unit 24 acquires the current value when each voltage is applied, finds regression line 100 of the acquired plurality of current values, and derives the current value when the voltage is zero on regression line 100. In other words, derivation unit 24 derives the value of the intersection of regression line 100 and the vertical axis. The derived current value is shown in the graph of FIG. 7(b) when the electric field strength is "zero."

[0049] Similarly, when the electric field strength is "weak," the derivation unit 24 finds the regression line 102 and derives the current value when the voltage on the regression line 102 is zero. The derived current value is shown in the graph for the "weak" electric field strength in FIG. 7(b), and is greater than the current value derived when the electric field strength is "zero."

[0050] Similarly, when the electric field strength is "strong," the derivation unit 24 finds the regression line 104 and derives the current value when the voltage on the regression line 104 is zero. The derived current value is shown in the graph of FIG. 7(b) when the electric field strength is "strong," and is greater than the current value derived when the electric field strength is "weak." Therefore, it can be seen from FIGS. 7(a) and (b) that a current value according to the electric field strength between the vehicle surface and the ground can be derived.

[0051] In this way, according to the sixth configuration example, it is possible to obtain the current value due to the air ions that naturally accumulate on the vehicle surface, that is, it is possible to obtain the amount of air ions that are attracted to the vehicle surface more accurately.

[0052] 6 does not include the insulating member 14 of the fourth configuration example, but the insulating member 14 may be provided. By providing the insulating member 14, the amount of air ions per unit area can be measured more accurately. The insulating member 14 does not have to be provided in the fourth configuration example.

[0053] 8 shows a seventh configuration example of the sensor device 1. The following description will focus on the differences from the sixth configuration example of FIG.

[0054] As shown in FIG. 8 , the sensor device 1 includes two sets of the measurement electrode 10, guard electrode 12, measurement unit 20, and voltage source 40 of the sixth configuration example. The sensor device 1 may include three or more of these sets. Specifically, the sensor device 1 includes a first measurement electrode 10a, a second measurement electrode 10b, a first guard electrode 12a, a second guard electrode 12b, a first measurement unit 20a, a second measurement unit 20b, a first voltage source 40a, a second voltage source 40b, and a derivation unit 24. Hereinafter, the first measurement electrode 10a and the second measurement electrode 10b will be collectively referred to as measurement electrodes 10, and the first guard electrode 12a and the second guard electrode 12b will be collectively referred to as guard electrodes 12, as appropriate. The first measurement unit 20a and the second measurement unit 20b will be collectively referred to as measurement unit 20, and the first voltage source 40a and the second voltage source 40b will be collectively referred to as voltage source 40, as appropriate.

[0055] The plurality of measurement electrodes 10 are attached to the surface of the vehicle 90. It is preferable that the plurality of measurement electrodes 10 are attached close to each other. The plurality of measurement electrodes 10 may be attached to the windshield of the vehicle 90, for example. Each of the plurality of guard electrodes 12 is attached to the surface of the vehicle 90 so as to surround the corresponding measurement electrode 10. The guard electrodes 12 do not contact each other.

[0056] The first voltage source 40a applies a fixed positive voltage to the corresponding first guard electrode 12a. The second voltage source 40b applies a fixed negative voltage to the corresponding second guard electrode 12b. In other words, each of the multiple voltage sources 40 applies a different fixed voltage to the corresponding guard electrode 12. The voltage applied by each voltage source 40 can be determined in the same manner as in the sixth configuration example.

[0057] The first measurement unit 20a measures a positive current Ia flowing between the corresponding first measurement electrode 10a and the earth 30. The second measurement unit 20b measures a negative current Ib flowing between the corresponding second measurement electrode 10b and the earth 30. In other words, the multiple measurement units 20 each measure the current flowing through the corresponding measurement electrode 10.

[0058] The derivation unit 24 acquires the current values ​​measured by each of the multiple measurement units 20, derives a regression line based on the multiple voltage values ​​applied by the multiple voltage sources 40 and the multiple acquired current values, and derives the current value when the voltage on the derived regression line is zero.

[0059] In the seventh configuration example, multiple current values ​​for deriving the regression line can be obtained simultaneously, and therefore the current value due to air ions naturally accumulated on the vehicle surface can be obtained in a shorter time than in the sixth configuration example.

[0060] It should be noted that a plurality of insulating members 14 may be provided, and each of the plurality of insulating members 14 may be provided along the inner periphery of the corresponding guard electrode 12 .

[0061] The fifth configuration example may be combined with the sixth or seventh configuration example. In this case, the charge adjustment unit 22 may adjust the charge state of the surface of the vehicle 90 based on the current value derived by the derivation unit 24 of the sixth or seventh configuration example based on the regression line. This process corresponds to the charge adjustment unit 22 adjusting the charge state of the surface of the vehicle 90 based on the current value measured by the measurement unit 20 in the sixth or seventh configuration example.

[0062] The present invention has been described above based on the embodiments. However, the embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention. [Explanation of symbols]

[0063] 1...sensor device, 10...measurement electrode, 10a...first measurement electrode, 10b...second measurement electrode, 12...guard electrode, 12a...first guard electrode, 12b...second guard electrode, 14...insulating member, 20...measurement section, 20a...first measurement section, 20b...second measurement section, 22...charge adjustment section, 24...derivation section, 30...earth, 40...voltage source, 40a...first voltage source, 40b...second voltage source, 90...vehicle.

Claims

1. measurement electrodes attached to the surface of the vehicle; a measurement unit that measures a current flowing through the measurement electrode; A sensor device comprising:

2. 2. The sensor device according to claim 1, further comprising a guard electrode connected to the ground of the vehicle and attached to a surface of the vehicle so as to surround the measurement electrode and spaced apart from the measurement electrode.

3. 3. The sensor device according to claim 2, further comprising a voltage source for applying a voltage between the guard electrode and the ground of the vehicle.

4. The voltage source varies the voltage it applies, The sensor device according to claim 3, further comprising a derivation unit that acquires current values ​​measured by the measurement unit when each of a plurality of voltages is applied by the voltage source, derives a regression line based on the plurality of voltages and the acquired plurality of current values, and derives a current value when the voltage on the derived regression line is zero.

5. 5. The sensor device according to claim 1, further comprising a charge adjusting unit that adjusts a charge state of the surface of the vehicle based on the current value measured by the measuring unit.

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