Resistive body position sensor

Abstract

A resistance body position sensor (1) of the present invention, in which variation in output at an idle position and generation of noise are suppressed, has a resistance body (11) and a slider (12) that slides on the resistance body (11), the output of the resistance body position sensor varying depending on the position at which the slider (12) comes into contact with the resistance body (11), the resistance body (11) containing carbon fibers (112) and a binder resin (111) as constituent components, the hardness of the carbon fibers (112) being set as Hc, the hardness of the binder resin (111) being set as Hr, the hardness of a contact end (12E) of the slider (12) that comes into contact with the resistance body being set as Hb, and the following relation shown by Expression (1) being satisfied: Hb ≤ 2 × Hc - Hr ≤ 1.2 × Hb... (1).

Description

Technical Field

[0001] This invention relates to a resistive position sensor for measuring the opening and closing degree of an on / off valve used to control the intake of a two-wheeled or four-wheeled vehicle. Background Technology

[0002] To improve combustion efficiency and reduce pollution, it is crucial to optimize the air-fuel mixture ratio introduced into the engine cylinders to ensure complete combustion. Therefore, intake control using a throttle valve sensor to accurately measure the opening and closing degree of the throttle valve becomes essential. For example, Patent Document 1 describes a resistive element position sensor in which the volume ratio of carbon black and carbon fiber contained in the resistive element is adjusted to meet the linearity and wear resistance requirements of a variable resistor.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-331806 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In recent years, from the perspective of global warming and environmental countermeasures, emission limits for both two-wheeled and four-wheeled vehicles have been strengthened. For example, Europe has an emission limit called EURO, which sets upper limits for emissions of carbon monoxide and nitrogen oxides. Since 2020, Euro 5 restrictions have been implemented, further tightening emission limits for two-wheeled vehicles. Furthermore, self-diagnostic functions such as On-Board Diagnosis (OBD), which allows vehicles to diagnose and detect their own malfunctions, have been raised to the OBD2 threshold. As a result, throttle sensors are required to exhibit no changes in linearity characteristics or noise generation from their initial state to after durability testing.

[0008] In the future, emission restrictions as an environmental measure are becoming increasingly stringent in Southeast Asia, South Asia, and Africa, regions expected to expand as markets for two-wheeled vehicles. Furthermore, throttle body sensors include non-contact sensors using magnetic sensors and contact sensors using variable resistors. In these regions, the demand for contact throttle body sensors, which are cheaper than non-contact sensors, is increasing. Therefore, the requirements for the durability and linearity of contact throttle body sensors are becoming more stringent. In contact throttle body sensors, the brush (slider) slides in contact with the surface of the resistive element. Therefore, with use, the portion of the brush that has slid on the surface of the resistive element and the contact end of the brush wear down. With increased sliding due to prolonged use, wear may cause abnormal output values ​​in the throttle body sensor. For example, in the case of two-wheeled vehicles, there are many instances of stopping while the engine is running. In this situation, the throttle is held in a slightly open idle position. At this time, in the throttle body sensor, the resistive element and brush are placed in a sliding state under a state of micro-vibration, i.e., within a very small range. Therefore, wear is particularly significant within this small range, which can easily lead to output fluctuations at idle position and noise.

[0009] The purpose of this invention is to provide a resistive position sensor that suppresses output fluctuations and noise generation at the idle position.

[0010] Technical means to solve the problem

[0011] To address the aforementioned problems, the present invention provides a resistive position sensor comprising a resistive element and a slider that slides on the resistive element, wherein the output of the resistive position sensor changes depending on the position of contact between the slider and the resistive element, characterized in that the resistive element contains carbon fiber and adhesive resin as constituent components, and when the hardness of the carbon fiber is set to Hc, the hardness of the adhesive resin is set to Hr, and the hardness of the contact end of the slider that contacts the resistive element is set to Hb, the relationship shown in the following formula (1) is satisfied.

[0012] Hb≤2×Hc-H≤1.2×Hb· · · (1)

[0013] Based on the above structure, the wear of the sliding component can be reduced with almost no wear on the resistive element. Therefore, for example, when the resistive element position sensor is used as the throttle position sensor for a two-wheeled vehicle, it is possible to suppress uneven wear at the idle position and suppress fluctuations in the output value.

[0014] The carbon fiber can be pulverized carbon fiber. By using pulverized carbon fiber, the wear resistance of the resistive element is improved.

[0015] Preferably, the resistive position sensor has a lubricant present between the slider and the resistive element, the lubricant being a linear perfluoropolyether.

[0016] The lubricant prevents the accumulation of wear powder caused by wear of the sliding component between the sliding component and the resistive element. Therefore, it suppresses the generation of output noise due to increased sliding frequency over long-term use.

[0017] The surface tension of the lubricant is preferably below 20 mN / m. This facilitates the removal of wear powder from around the sliding parts, thus more effectively suppressing the generation of output noise.

[0018] In the resistive element, the content of the adhesive resin is preferably more than 2 parts by volume and less than 6 parts by volume relative to 1 part by volume of the carbon fiber.

[0019] The resistive element also contains carbon black, and the content of the carbon black is preferably 0.2 parts by volume or more and 2 parts by volume or less relative to 1 part by volume of the carbon fiber.

[0020] In the resistive element, the content of the adhesive resin is preferably more than 1 part by volume and less than 5 parts by volume relative to the total volume of the carbon fiber and / or the carbon black.

[0021] By setting the volume ratio of carbon fiber, adhesive resin and carbon black to the above range, the wear resistance of the resistive element is adjusted so that the relationship of equation (1) can be easily satisfied.

[0022] Invention Effects

[0023] According to the present invention, a resistive position sensor is provided that suppresses output fluctuations in idle position and noise generation due to increased slippage caused by long-term use. Attached Figure Description

[0024] Figure 1 This is a schematic cross-sectional view illustrating the structure of the resistive position sensor of the present invention.

[0025] Figure 2 This is a schematic diagram illustrating the determination of the opening degree of an open / closed valve based on a resistive position sensor.

[0026] Figure 3 This is a schematic diagram used to illustrate the position determination principle based on a resistive position sensor.

[0027] Figure 4A This is a schematic diagram showing the relationship between the resistive element, the position of the brush sliding on the surface of the resistive element, and the rotation angle of the opening and closing valve.

[0028] Figure 4BIt is a graph showing the rotation angle of the valve and the output voltage.

[0029] Figure 5A It is a graph showing the change in output voltage Vi caused by the wear of the resistive element as the number of sliding cycles increases.

[0030] Figure 5B It is a graph showing the change in output voltage Vi caused by the wear powder layer formed as the number of sliding cycles increases.

[0031] Figure 6A This is a schematic diagram showing carbon fibers before they are crushed.

[0032] Figure 6B This is a magnified schematic diagram showing the fine structure of pulverized carbon fibers.

[0033] Figure 7 It is a graph representing the anisotropy of hardness of pulverized carbon fibers.

[0034] Figure 8A This is a graph of Example 1 showing the change in output voltage and the rate of change in total resistance as the number of sliding cycles increases.

[0035] Figure 8B This is a graph comparing the change in output voltage and the rate of change in total resistance as the number of sliding cycles increases, as shown in Example 1.

[0036] Figure 9A This is a photograph used as a substitute for the accompanying drawing of Example 1, showing the state of the resistive element and brush after the durability test.

[0037] Figure 9B The attached photograph is a substitute photograph for Comparative Example 1, showing the state of the resistive element and brush after the durability test.

[0038] Figure 10A This is a graph representing the noise intensity of Example 4.

[0039] Figure 10B This is a graph representing the noise intensity of Comparative Example 2.

[0040] Figure 11 This is a schematic diagram used to illustrate the measurement of carbon fiber hardness. Detailed Implementation

[0041] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Identical components will be labeled with the same reference numerals in the drawings, and descriptions will be omitted where appropriate.

[0042] Figure 2This is a schematic diagram illustrating a fuel injection system that uses a resistive position sensor 1 to measure the rotation angle X, which indicates the opening degree of the on / off valve 2. As shown in the diagram, the resistive position sensor 1 measures the rotation angle X of the on / off valve 2, which is used to adjust the mixing ratio of air 3 and gasoline 4 in the mixture 5 supplied to the engine 6.

[0043] Figure 3 This is a schematic diagram illustrating the position measurement principle based on the resistive position sensor 1. As shown in the diagram, the resistive position sensor 1 uses an output voltage that varies according to the contact position between the brush 12, a sliding element that slides on the surface 11S of the resistive element 11, and the resistive element 11, to detect the position of the brush 12. If the position of the brush 12 in the resistive element 11 varies according to the rotation angle X of the opening / closing valve 2 (refer to...), the position of the brush 12 in the resistive element 11 will be determined based on the rotation angle X of the opening / closing valve 2. Figure 2 The change in voltage allows for the determination of the opening / closing degree of valve 2. Furthermore, in... Figure 3 For ease of explanation, the resistor 11 is depicted as a straight line, but it can also be formed as an arc.

[0044] Figure 4A This is a schematic diagram showing the relationship between the position of the resistive element 11, the brush 12 sliding on its surface 11S, and the rotation angle X. Figure 4B It is a graph schematically showing the deviation from the ideal curve of the output voltage as it varies with the rotation angle X.

[0045] like Figure 4A As shown, the brush 12 slides on the surface 11S of the resistive body 11 within the range from rotation angle Xi to Xf. The sliding trajectory 12T represents the range of sliding of the brush 12. That is, the contact position between the resistive body 11 and the brush 12 within the rotation angle Xi is one end of the sliding range of the brush 12, i.e., the position where the detected rotation angle is the minimum value, which can also be described as the position of the 0° rotation angle of the resistive body position sensor 1. The resistance R of the resistive body 11 can be divided into the resistance Rb of the part where the brush 12 slides from the rotation angle Xi to Xf, and the resistance Ri of the part where the brush 12 does not slide from the rotation angle Xi to Xi.

[0046] Since the brush 12 does not slide within the region from rotation angle 0 to Xi, the resistance Ri is unaffected by the wear of the resistor body 11 and the brush 12. Therefore, the resistance Ri value after the durability test, which evaluates the condition after long-term use, does not change from the initial resistance value. In contrast, since the brush 12 slides within the region from rotation angle Xi to Xf, the resistance Ri value after the durability test is affected by the wear of the resistor body 11 and the brush 12. Therefore, the resistance Rb value after the durability test changes from the initial value even with wear on the resistor body 11 and the brush 12.

[0047] exist Figure 4B The ideal curve showing the relationship between the initial rotation angle and the output voltage is illustrated by a dashed line. As shown in the figure, the linearity (straightness) between the initial rotation angle and the output voltage is good. However, due to repeated use of the resistive position sensor 1, a deviation occurs between the output voltage and the ideal curve. Two possible reasons for this deviation are wear of the resistive element 11 (first case) and wear of the brush 12 resulting in a wear powder layer (second case).

[0048] <First Case>

[0049] As the brush 12 slides on the resistor 11, the resistor 11 in the sliding trajectory 12T wears, and the cross-sectional area of ​​the resistor 11 in the portion of the sliding trajectory 12T decreases. Therefore, the resistance value of resistor Rb increases. As a result, the output voltage decreases from its initial value. If the output voltage Vi, resistance Ri, and resistance Rb at the rotation angle Xi at the idle position are set as Vi, Ri, and Rb respectively, then Vi = Ri / (Ri + Rb). Therefore, through repeated use, when the resistor 11 wears and the resistance Rb increases, the output voltage Vi at the idle position decreases. Therefore, by using carbon fiber as a reinforcing material for the resistor 11, wear of the resistor 11 can be suppressed.

[0050] Figure 5A This is a graph schematically showing the change in output voltage Vi at the idle position due to wear of resistor 11 with increasing number of sliding cycles. In the first case, the output voltage Vi decreases with increasing number of repeated sliding cycles.

[0051] <Second Case>

[0052] Because the brush 12 slides on the resistive body 11, the brush 12 wears down, resulting in wear at the contact end 12E of the brush 12 (refer to...). Figure 3 A layer of wear powder forms around the brush 12. Besides the contact end 12E that contacts the surface 11S of the resistor 11, this wear powder layer also serves as a pathway for current flowing between the brush 12 and the resistor 11. Therefore, the resistance value of the resistor Rb decreases from its initial value, and the output voltage increases from its initial value. Thus, when the brush 12 wears, the output voltage Vi = Ri / (Ri + Rb) at idle position increases.

[0053] Figure 5B This is a graph schematically showing the change in output voltage Vi at the idle position caused by wear of brush 12 with increasing slip count. In the second case, the output voltage Vi at the idle position increases with increasing slip count.

[0054] Previously, due to the repeated operation of the resistive position sensor 1, wear occurred on the resistor 11 and brush 12, which caused a decrease in the linearity of the output voltage. Specifically, in the case of wear on the resistor 11 (the first case), it was impossible to prevent the resistance Rb from increasing. In contrast, for the wear on the brush 12, if wear particles could be removed from the vicinity of the contact end 12E, the change in resistance Rb could be prevented. Therefore, regarding the impact on accuracy related to the linearity of the output voltage of the resistive position sensor 1, it can be said that the wear on the resistor 11 is greater than the wear on the brush 12. Therefore, in the past, primarily to prevent wear on the resistor 11, the hardness of the resistor 11 was made greater than that of the brush 12, and the amount of wear on the resistor 11 was minimized.

[0055] However, from the perspective of global warming and environmental countermeasures, the impact of brush 12 wear cannot be ignored as requirements for durability and linearity increase. For example, in variable resistance throttle sensors for two-wheeled vehicles, the requirements for linearity have further increased with the recent advancements in motorcycle electronic controls, making the variation in the linearity characteristics of the output voltage more significant. In other words, due to the increased linearity requirements, it is necessary to suppress the variation in output voltage linearity caused by the metal film formed from the wear powder of the brush 12. Therefore, it is difficult to address this issue simply by improving the previously used resistor 11.

[0056] Therefore, the present invention suppresses wear of both the resistor 11 and the brush 12 by defining the relationship between the hardness of the resistor 11 and the hardness of the brush 12. Furthermore, the influence of wear powder is further suppressed by using a lubricant that effectively removes wear powder from the periphery of the contact end 12E.

[0057] Figure 1 This is a schematic cross-sectional view showing the structure of the resistive position sensor 1. As shown in the figure, the resistive position sensor 1 includes a resistive element 11 and a brush 12, and a lubricant 13 is present between the resistive element 11 and the brush 12 (interface).

[0058] For example, a resistor 11 is manufactured by thinly coating an ink made of carbon black 111 and carbon fiber 112 mixed with adhesive resin 113 onto an insulating substrate using screen printing or similar methods, followed by sintering. The carbon black (hereinafter also appropriately referred to as CB) 111 primarily imparts electrical conductivity to the resistor 11, while the carbon fiber (hereinafter also appropriately referred to as CF) 112 primarily imparts abrasion resistance to the resistor 11.

[0059] For example, CF112 can preferably be made from pulverized carbon fibers manufactured by pulverizing fibrous carbon fibers with a diameter of about 6 to 10 μm. When using pulverized CF as CF112, the average length in the longitudinal direction is preferably about 2.0 to 4.0 μm, and more preferably about 2.5 to 3.5 μm. Furthermore, the longitudinal direction mentioned here refers to the direction in which the carbon fibers extend before being pulverized.

[0060] Furthermore, the carbon fibers used in CF112 are heat-treated to create a structure formed by stacking graphite in a foil-like (thin-layer) shape along its length. Figure 1 The arrow in the figure shows the direction V perpendicular to the graphite surface formed along the length of CF112. As shown in the figure, each CF112 is dispersed in the adhesive resin 113 uniformly dispersed in CB111 in a random state in the direction V perpendicular to the graphite surface (the graphite surface is facing a random direction).

[0061] As described later, the hardness of CF112 is anisotropic, reaching its maximum in the direction V perpendicular to the graphite surface. The hardness of CF112 is 150–250 kgf / mm². 2 The dimensions are approximately [number], and can be adjusted through heat treatment.

[0062] The hardness of CF112 was measured using a sample in which CF112 was dispersed in adhesive resin 113. Although the hardness of CF112 in the V direction cannot be directly measured, it is presumed that the maximum measured hardness is approximately equal to the value obtained when the direction of pressing the sample (compression direction) is aligned with the V direction of CF112. Therefore, the maximum measured value is approximately consistent with the hardness of CF112 in the V direction. When the angle between the compression direction and the V direction increases and the hardness of CF112 decreases, the hardness of the adhesive resin 113 in which CF112 is dispersed affects the measured value. Moreover, as the angle approaches a right angle, the measured hardness of CF112 gradually approaches the hardness of the adhesive resin 113, with the minimum value approximately consistent with the hardness of the adhesive resin. The average hardness measured value can be estimated to be equivalent to the result measured when the angle between the V direction of CF112 and the compression direction of the measuring indenter is approximately 45 degrees.

[0063] The hardness in this invention refers to the value measured using a microhardness tester called a nanoindenter, according to the test method (nanoindentation method) specified in the international standard (ISO 14577:2015). The difference between a nanoindenter and a Vickers hardness tester is that the nanoindenter uses a triangular indenter, while the Vickers hardness tester uses a rhomboid indenter. The hardness measured using a nanoindenter can be converted to Vickers hardness using a Vickers hardness tester.

[0064] Figure 11This is a schematic diagram illustrating the measurement of carbon fiber hardness. When measuring the hardness of the resistive element 11 in which CF112 is dispersed in the binder resin 113, the measured value varies depending on the position of the measuring indenter 15. This is because the angle θ between the V direction of CF112 and the pressure direction of the measuring indenter 15 changes according to the position of the measuring indenter 15 on the surface 11S of the resistive element 11.

[0065] exist Figure 11 In the equation θc < θb < θa, since the smaller the angle θ, the greater the hardness, the hardness increases in the order of the positions of the measuring indenter 15: 15c > 15b > 15a. As θ approaches a right angle, the hardness of CF112 approaches the hardness of the adhesive resin 113, which is approximately the same as the hardness of the adhesive resin 113 at position 15d where CF112 is not present on surface 11S. In this invention, the average of the measured values ​​is set as the hardness Hc of the carbon fiber of CF112.

[0066] Adhesive resin 113 is a dispersion medium for dispersing CB and CF. The hardness of adhesive resin 113 is preferably, for example, 50 to 80 [kgf / mm²]. 2 More preferably 60-70 kgf / mm 2 For example, phenolic resin, epoxy resin, melamine resin, unsaturated polyester, etc. can be used as adhesive resin 113.

[0067] The content of adhesive resin 113 relative to 1 volume part of CF112 is preferably 2 or more and 6 or less, more preferably 3 or more and 5 or less. In addition, the content of adhesive resin 113 relative to 1 volume part of the total of CF112 and / or CB111 is preferably 1 or more and 5 or less, more preferably 1.5 or more and 4 or less.

[0068] The resistive element 11 can be manufactured, for example, using an ink that is a mixture of 60-80% by volume of phenolic resin and 20-40% by volume of the total amount of CB111 and CF112 (hereinafter appropriately referred to as carbon). The ratio of CB111 to CF112 can be appropriately adjusted according to the resistance value or hardness of the resistive element 11, for example, setting CF112 to 1 volume part (1 volume part of carbon fiber) and CB111 to 0.2-2 volume parts.

[0069] From the viewpoint of setting the resistance value of resistor 11 to an appropriate value as a resistive position sensor 1, it is preferable to use an ink made by mixing 60-70% by capacity of phenolic resin and 30-40% by capacity of carbon. From the same viewpoint, the volume ratio of CB111 content to CF112 content is preferably 1:2 to 2:1.

[0070] The brush 12 is made of a conductive metal. Preferably, the conductive metal has a hardness of 280–340 kgf / mm². 2 Approximately 50-70 micrometers. Additionally, the thickness of the brush 12 is, for example, approximately 50-70 micrometers. In this case, a thickness approximately 20 times the diameter of the CF112 (2.5-3.5 micrometers) is preferred. Furthermore, Figure 1 This is a schematic diagram, so the actual dimensions of CF112 and brush 12 in resistor 11 are ignored.

[0071] The load of brush 12 can be set to, for example, 1 to 10 g.

[0072] Figure 6A This is a schematic diagram showing the carbon fiber used as a raw material for CF112. Figure 6B This is a magnified schematic diagram showing the fine structure of CF112 obtained from pulverization. As described above and Figure 6A As shown, carbon fibers are formed by stacking graphite in a foil-like (thin-layer) shape along their length. Therefore, if carbon fibers are pulverized, they are pulverized along the direction P, which is the length direction of the stacked graphite surfaces. Moreover, the hardness of the pulverized CF used as CF112 differs significantly in the direction P, which is parallel to the graphite surface, and in the direction V, which is perpendicular to the graphite surface. The hardness of CF112 is greater in the direction V than in the direction P.

[0073] Figure 7 This is a graph illustrating the anisotropy of the hardness of CF112. The following explanation uses this graph to illustrate the hardness of CF112 as a powdered CF.

[0074] The hardness of CF112 is greatest in the direction V, which is perpendicular to the graphite surface of CF112, and least in the direction P, which is parallel to the graphite surface. The hardness of CF112 in the direction parallel to the graphite surface, which has the least hardness, is approximately equal to the hardness of the adhesive resin 113.

[0075] like Figure 1 As shown, CF112 is uniformly dispersed in three dimensions, making the direction V perpendicular to the graphite surface a random direction. Therefore, the actual measured hardness (average value) of the resistivity 11 is taken as the midpoint between the hardness Hv of CF112 in direction V and the hardness Hr of the adhesive resin 113. That is, the measured value of the resistivity 11 can be said to be approximately the same as the hardness Hc of CF112 when CF112 is dispersed at an angle of approximately 45° relative to direction V.

[0076] Therefore, the maximum value of the partial hardness in the resistive element 11, that is, the hardness of the portion of CF112 in the direction V on the surface 11S of the resistive element 11, is: 2×(Hc-Hr)+Hr=2×Hc-Hr. Compared with the average hardness of CF112, the wear of the brush 12 is more affected by the hardness of CF112 existing in the resistive element 11 at its maximum hardness.

[0077] Therefore, the hardness 2×Hc-Hr is not less than the hardness Hb of the brush 12, and becomes the same value as the hardness Hb of the brush 12. That is, the hardness of the resistor 11 and the hardness of the brush 12 are set in a manner that satisfies the following formula (1). As a result, the wear of both the resistor 11 and the brush 12 can be minimized.

[0078] Hb≤2×Hc-Hr≤1.2×Hb· · · (1)

[0079] Hb: The average hardness of brush 12 was measured.

[0080] Hc: The average hardness of CF112 was measured.

[0081] Hr: The average hardness of adhesive resin 113 was measured.

[0082] Previously, from the viewpoint that wear of the resistor 11 was a more serious defect than wear of the brush 12, it was desirable to minimize the amount of wear on the resistor 11. However, in order to minimize the wear of both the resistor 11 and the brush 12, the hardness of the resistor 11 and the brush 12 was designed in a manner that satisfies the relationship of the above equation (1). In addition, 2×Hc-Hr can be adjusted by heat treatment to graphitize CF112 so that it can slide easily.

[0083] The resistive position sensor 1 sets the hardness of the resistive element 11 and the brush 12 in accordance with equation (1) to suppress the brush 12 from sliding on the resistive element 11 and generating wear powder. However, if wear powder is generated and gets stuck at the interface between the resistive element 11 and the brush 12, the resistance R of the resistive element changes. As a result, the contact resistance of the resistive position sensor 1 increases or decreases, thereby generating noise in the output voltage. Therefore, although a lubricant 13 is originally applied between the resistive element 11 and the brush 12 to reduce wear, in the resistive position sensor 1 of this application, the lubricant 13 also has the function of removing wear powder.

[0084] As a lubricant 13, from the viewpoint of heat resistance and durability, perfluoropolyether (hereinafter referred to as PFPE) with low vapor pressure and high boiling point is preferred.

[0085] From the viewpoint of preventing the accumulation of wear powder near the brush 12, it is preferable that the PFPE does not have a branched structure. Furthermore, from the same viewpoint, it is preferable to have a small number of oxygen bonds, which contribute to the entanglement of wear powder. Therefore, a straight-chain PFPE with a small number of oxygen bonds is preferred. Examples of preferred straight-chain PFPEs include fluorine-based PFPEs with the following structural formula.

[0086] F-(CF2CF2CF2O)n-CF2CF3

[0087] Furthermore, from the viewpoint of effectively removing wear powder near the contact end 12E of the brush 12, the surface tension of the PFPE used as lubricant 13 is preferably 20 mN / m or less. From the same viewpoint, a lubricant with a low number of functional groups is preferred as lubricant 13.

[0088] That is, when the number of sliding strokes of the brush 12 increases, from the viewpoint of suppressing output noise generated in the output voltage, the lubricant 13 is preferably a linear PFPE with a surface tension of 20 mN / m or less. Commercially available PFPEs with such preferred properties include, for example, DEMNUM (trade name, manufactured by Daikin Industries, Ltd.).

[0089] The embodiments disclosed in this specification are illustrative in all respects and are not intended to limit the invention to those embodiments. The scope of the invention is not shown solely by the description of the above embodiments, but is set forth in the claims, which are intended to include all modifications within the meaning and scope of the claims.

[0090]

Example

[0091] [Example 1]

[0092] Using pulverized carbon fiber as the carbon fiber and phenolic resin (hardness Hr = 70) as the binder resin, a resistive element with a surface hardness Hc (average hardness of pulverized carbon fiber) of 200 is formed. A resistive element position sensor is manufactured using this resistive element and a brush with a measured hardness (Hb) of 310. DEMNUM S65 (trade name, manufactured by Daikin Industries, Ltd., perfluoropolyether, surface tension 18.0 mN / m) is used as the lubricant for the resistive element position sensor.

[0093] The relationship between the hardness Hc of the carbon fiber, the hardness Hr of the adhesive resin, and the hardness Hb of the contact end of the brush (slider) in the resistive position sensor of this embodiment is shown in the following formula.

[0094] 2×Hc-Hr=1.06Hb

[0095] The hardness values ​​of crushed carbon fiber, phenolic resin, and electric brush are calculated by converting the values ​​measured by the nanoindenter into Vickers hardness values.

[0096] [Example 2]

[0097] Except for using a resistive element with a surface hardness Hc of 190, a resistive position sensor was manufactured in the same manner as in Example 1. The relationship between Hc, Hr, and Hb in the resistive position sensor of this embodiment is shown in the following formula.

[0098] 2×Hc-Hr=1.0Hb

[0099] [Example 3]

[0100] Except for using a resistive element with a surface hardness Hc of 210, a resistive position sensor was manufactured in the same manner as in Example 1. The relationship between Hc, Hr, and Hb in the resistive position sensor of this embodiment is shown in the following formula.

[0101] 2×Hc-Hr=1.13Hb

[0102] [Comparative Example 1]

[0103] Except for using a resistive element with a surface hardness Hc of 250, a resistive position sensor was manufactured in the same manner as in Example 1. The relationship between Hc, Hr, and Hb in the resistive position sensor of this comparative example is shown in the following formula.

[0104] 2×Hc-Hr=1.39Hb

[0105] Figure 8A and Figure 8B It is a graph showing the changes in output voltage and total resistance as the number of sliding cycles increases. Figure 8A The results of the resistive position sensor of Example 1 are shown. Figure 8B The results for the resistive position sensor in Comparative Example 1 are shown. Additionally, Examples 2 and 3 are also compared... Figure 8A Similarly, in Example 1, the changes in output voltage and total resistance with increasing sliding frequency are minimal. Thus, by using a resistive element and brush with stiffness satisfying the relationship shown in Equation (1), a resistive position sensor with minimal changes in output voltage (ΔVi) and total resistance change rate (R) at the idle position can be manufactured. In contrast, the resistive position sensor of Comparative Example 1, which does not satisfy the relationship shown in Equation (1), is as follows... Figure 8B As shown, the rate of change of output voltage and total resistance increases with the number of sliding cycles.

[0106] Figure 9A and Figure 9BThis is a substitute photograph showing the state of the resistor 11 and brush 12 after the durability test. Figure 9A The results of Example 1 are shown. Figure 9B The results of Comparative Example 1 are shown.

[0107] like Figure 9A As shown in Embodiment 1, by using a resistive body 11 and a brush 12 with hardness satisfying the relationship shown in Equation (1), the amount of wear on the brush 12 can be suppressed, preventing wear powder from adhering to the contact end 12E. Then, a sliding trajectory 12T is formed in the metal layer where the wear powder adhering to the surface 11S of the resistive body 11 is almost invisible. Furthermore, in Embodiments 2 and 3, the same applies... Figure 9A Similarly, in Example 1 shown, the wear is minimal, and the wear powder does not adhere to the contact end 12E, forming a sliding trajectory 12T of a metal layer with almost no visible wear powder.

[0108] In contrast, such as Figure 9B As shown in Comparative Example 1, when a resistor 71 with a hardness that does not satisfy the relationship shown in Equation (1) is used, the wear of the brush 72 increases, wear powder adheres to the contact end 72E, and a brush sliding trajectory 72T with a metal layer of wear powder adhered to the surface 71S of the resistor 71 is formed.

[0109] As described above, by satisfying the relationship shown in Equation (1) for the hardness of the resistive element 11 and the brush 12, a resistive element position sensor 1 is obtained that can suppress the output variation of the idle position and the noise generated after the number of sliding times increases due to long-term use.

[0110] <Example 4>

[0111] Regarding the resistive position sensor of Embodiment 1, the noise intensity generated when the ambient temperature periodically changes within a range from -30°C to 120°C is measured on the surface 11S of the resistive element 11 while the brush 12 is repeatedly slid along the surface.

[0112] <Comparative Example 2>

[0113] For the resistive position sensor that uses Fomblin M30 (trade name, manufactured by Solvay, perfluoropolyether, surface tension of 25 mN / m) as a lubricant instead of DEMNUM S65 in Example 1, the noise intensity was measured in the same manner as in Example 4.

[0114] Figure 10A and Figure 10B It is a graph representing the noise intensity. Figure 10A These are the measurement results from Example 4. Figure 10BThis is the measurement result of Comparative Example 2. In this figure, the ambient temperature is represented by a line graph, and the noise intensity is represented by a bar chart. The vertical axis of the noise represents the noise intensity, indicating that the higher up the axis, the greater the noise.

[0115] like Figure 10A As shown, the resistive position sensor of Example 4 did not detect noise generation after 700K (700,000) repeated sliding cycles. In contrast, the resistive position sensor of Comparative Example 2 detected noise generation after more than 150K (150,000) repeated sliding cycles. Based on this result, from the viewpoint of suppressing noise generation, perfluoropolyether with a surface tension of 20 mN / m or less is preferably preferred as a lubricant.

[0116] Industrial applicability

[0117] As explained above, the resistive position sensor of the present invention suppresses output fluctuations and noise generation at the idle position, and is useful as a throttle position sensor for two-wheeled vehicles.

[0118] Explanation of reference numerals in the attached figures

[0119] 1: Resistive position sensor

[0120] 2: On / off valve

[0121] 3: Air

[0122] 4: Gasoline

[0123] 5: Mixed gas

[0124] 6: Engine

[0125] 11: Resistor

[0126] 11S: Surface

[0127] 111: Carbon Black

[0128] 112: Carbon fiber

[0129] 113: Adhesive resin

[0130] 12: Brush (sliding component)

[0131] 12E: Contact end

[0132] 12T: Sliding trajectory

[0133] 13: Lubricant

[0134] 15: Measuring the pressure head

[0135] 15a~15d: Determine the position of the indenter

[0136] 71: Resistor

[0137] 71S: Surface

[0138] 72: Brush

[0139] 72E: Contact end

[0140] 72T: Brush sliding trajectory

[0141] Hb, Hc, Hv, Hr: Hardness

[0142] P, V: Direction

[0143] R, Rb, Ri: Resistance

[0144] Vi: Output voltage at idle position

[0145] X, Xf: Rotation angle

[0146] Xi: Rotation angle at idle position

[0147] θ, θa~θc: Angles between the V direction of the carbon fiber and the pressure direction of the measuring indenter.

Claims

1. A resistive position sensor, comprising a resistive element and a slider sliding on the resistive element, wherein the output of the resistive position sensor changes depending on the position of contact between the slider and the resistive element, characterized in that, The resistor contains carbon fiber and adhesive resin as constituent components. When the hardness of the carbon fiber is set to Hc, the hardness of the adhesive resin is set to Hr, and the hardness of the contact end in the sliding member that contacts the resistor is set to Hb, the following relationship (1) is satisfied: Hb≤2×Hc-Hr≤1.2×Hb (1), The hardness values ​​used in formula (1) are calculated by converting the average values ​​obtained using a microhardness tester with a triangular indenter as the measuring indenter, according to the test method specified in ISO 14577:2015, into Vickers hardness values.

2. The resistive position sensor as described in claim 1, characterized in that, The carbon fiber is pulverized carbon fiber.

3. The resistive position sensor as described in claim 1 or 2, characterized in that, It contains a lubricant between the slider and the resistor. The lubricant is a linear perfluoropolyether.

4. The resistive position sensor as described in claim 3, characterized in that, The surface tension of the lubricant is below 20 mN / m.

5. The resistive position sensor as described in claim 1 or 2, characterized in that, In the resistive element, the content of the adhesive resin is more than 2 parts by volume and less than 6 parts by volume relative to 1 part by volume of the carbon fiber.

6. The resistive position sensor as described in claim 5, characterized in that, The resistive element also contains carbon black. The content of carbon black is 0.2 parts by volume or more and 2 parts by volume or less relative to 1 part by volume of the carbon fiber.

7. The resistive position sensor as described in claim 6, characterized in that, In the resistive element, the content of the adhesive resin is more than 1 part by volume and less than 5 parts by volume relative to the total 1 part by volume of the carbon fiber and / or the carbon black.

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