Resistor Position Sensor

Abstract

A resistor position sensor 1 according to the present invention, in which changes in output and the generation of noise in an idling position are suppressed, comprises a resistor 11 and a slider 12 that slides on the resistor 11, the output changing according to the position at which the slider 12 is in contact with the resistor 11, wherein the resistor 11 includes carbon fibers 112 and a binder resin 111 as constituent components, and if the hardness of the carbon fibers 112 is Hc, the hardness of the binder resin 111 is Hr, and the hardness of the contact end 12E of the slider 12 which is in contact with the resistor is Hb, the relationship expressed by expression (1) is satisfied.　 (1): Hb≤2×Hc-Hr≤1.2×Hb

Description

[Technical field]

[0001] The present invention relates to a resistor position sensor used to measure the opening and closing degree of an on-off valve that controls the intake of two-wheeled vehicles and four-wheeled vehicles. [Background technology]

[0002] In order to improve fuel efficiency and reduce pollution, it is important to optimize the mixture ratio of air and gasoline taken into the engine cylinder to completely burn the gasoline. Therefore, intake control using a throttle valve sensor to accurately measure the opening and closing degree of the opening and closing valve is essential. For example, Patent Document 1 describes a resistor position sensor in which the volume ratio of carbon black and carbon fiber contained in the resistor is adjusted to satisfy the linearity characteristics and wear resistance required of a variable resistor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-331806 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0004] In recent years, exhaust gas regulations for both motorcycles and automobiles have been strengthened in light of global warming and environmental measures. For example, in Europe, exhaust gas regulations called EURO have been established, which stipulate upper limits on carbon monoxide and nitrogen oxide emissions. From 2020, Euro5 regulations will be implemented, and exhaust gas regulations for motorcycles will be strengthened. In addition, the self-diagnosis function called OBD (On Board Diagnosis), which is a system that diagnoses and detects malfunctions in the vehicle itself, has been upgraded to OBD2, which judges based on a threshold value. As a result, throttle valve sensors are required to have no change in linearity characteristics or noise generation from the initial state to after durability testing.

[0005] In Southeast Asia, South Asia, and Africa, where motorcycle markets are expected to expand in the future, exhaust gas regulations as environmental measures are becoming stricter. Throttle valve sensors are classified into non-contact type sensors using magnetic sensors and contact type sensors using variable resistors. In these regions, there is a high demand for contact type throttle valve sensors, which are cheaper than non-contact type sensors. For this reason, the demand for durability and linearity of contact type throttle valve sensors is increasing. In a contact type throttle valve sensor, a brush (slider) contacts and slides on the surface of a resistor. Therefore, with use, the part on the surface of the resistor where the brush slides and the contact end of the brush wear out. If the number of slides increases due to long-term use, there is a risk that an abnormality will occur in the output value of the throttle valve sensor due to wear. For example, in the case of motorcycles, there are many cases where the engine is left running while the vehicle is stopped. In such cases, the throttle valve is left in an idling position with the throttle valve slightly open. At this time, the throttle valve sensor is left in a state where a slight vibration is applied, that is, in a state where the resistor and the brush slide in a small range. This causes a large amount of wear especially in that small area, which can cause output fluctuations and noise at the idling position. An object of the present invention is to provide a resistor position sensor in which output fluctuations and noise generation at the idling position are suppressed. [Means for solving the problem]

[0006] A resistor position sensor according to one embodiment of the present invention provided to solve the above problems comprises a resistor and a slider that slides on the resistor, and the output of the resistor position sensor changes depending on the position at which the slider contacts the resistor. The resistor contains carbon fiber and binder resin as its constituent components, and is characterized in that when the hardness of the carbon fiber is Hc, the hardness of the binder resin is Hr, and the hardness of the contact end of the slider that contacts the resistor is Hb, the resistor position sensor satisfies the relationship shown in the following formula (1). Hb≦2×Hc-H ≦1.2×Hb (1) With the above-mentioned configuration, it is possible to reduce the amount of wear on the slider without causing much wear on the resistor. Therefore, for example, when the resistor position sensor is used as a throttle position sensor for a motorcycle, uneven wear at the idling position can be suppressed, and fluctuations in the output value can be suppressed.

[0007] The carbon fibre may be milled carbon fibre, which improves the wear resistance of the resistor.

[0008] The resistor position sensor includes a lubricant interposed between the slider and the resistor, and the lubricant is preferably a straight-chain perfluoropolyether. The lubricant prevents the accumulation of wear powder between the slider and resistor due to wear of the slider, which makes it possible to suppress the generation of output noise when the number of sliding movements increases over a long period of use. The lubricant preferably has a surface tension of 20 mN / m or less, which makes it easier to remove wear particles from around the slider, thereby more effectively suppressing the generation of output noise.

[0009] The resistor preferably has a binder resin content of 2 to 6 parts by volume relative to 1 part by volume of the carbon fiber. It is preferable that the resistor further contains carbon black, and the content of the carbon black is 0.2 parts by volume or more and 2 parts by volume or less per 1 part by volume of the carbon fiber. The resistor preferably has a binder resin content of 1 part by volume or more and 5 parts by volume or less per 1 part by volume of the binder resin and / or the carbon black in total. By setting the volume ratio of the carbon fiber, the binder resin, and the carbon black within the above range, it becomes easy to adjust the wear resistance of the resistor and satisfy the relationship of formula (1). Effect of the Invention

[0010] According to the present invention, it is possible to provide a resistor position sensor in which output fluctuations and noise generation at the idling position are suppressed even after the number of sliding movements increases due to long-term use. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic structure of a resistor position sensor according to the present invention. [Diagram 2] Schematic diagram explaining measurement of the opening degree of an on-off valve using a resistor position sensor [Diagram 3] Schematic diagram explaining the principle of position measurement using a resistor position sensor [Figure 4A] A schematic diagram showing the relationship between the resistor, the position of the brush that slides on the surface of the resistor, and the rotation angle of the on-off valve. [Figure 4B] Graph showing the rotation angle of an opening / closing valve and output voltage [Figure 5A] A graph showing the change in output voltage Vi due to wear of the resistor with an increase in the number of sliding movements [Figure 5B] A graph showing the change in output voltage Vi due to the wear powder layer on the brush as the number of strokes increases [Figure 6A] Schematic diagram showing carbon fiber before crushing [Figure 6B] Schematic of the microstructure of crushed carbon fiber at a magnified scale [Figure 7] Graph showing hardness anisotropy of crushed carbon fiber [Figure 8A] Graph of Example 1 showing the change in output voltage and the rate of change in total resistance with increasing number of sliding movements [Figure 8B] Graph of Comparative Example 1 showing the change in output voltage and the rate of change in total resistance with increasing number of sliding movements [Figure 9A] A photograph of Example 1 showing the state of the resistor and brush after the durability test [Figure 9B] A drawing substitute photograph of Comparative Example 1 showing the state of the resistor and brush after the durability test [Figure 10A] Graph of Example 4 showing noise intensity [Figure 10B] Graph of Comparative Example 2 showing noise intensity [Figure 11] Schematic diagram explaining hardness measurement of carbon fiber BEST MODE FOR CARRYING OUT THEINVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The same components are designated by the same reference numerals in each drawing, and the description will be omitted as appropriate. 2 is a schematic diagram illustrating a fuel injection system that uses a resistor position sensor 1 to measure a rotation angle X that indicates the degree of opening of an on-off valve 2. As shown in the figure, the resistor position sensor 1 measures the rotation angle X of the on-off valve 2 that adjusts the mixture ratio of air 3 and gasoline 4 in the air-fuel mixture 5 supplied to an engine 6.

[0013] Fig. 3 is a schematic diagram for explaining the principle of position measurement by the resistor position sensor 1. As shown in the figure, the resistor position sensor 1 detects the position of the brush 12 using an output voltage that changes according to the contact position between the resistor 11 and a brush 12, which is a slider that slides on the surface 11S of the resistor 11. If the position of the brush 12 on the resistor 11 is made to change according to the rotation angle X (see Fig. 2) of the on-off valve 2, it is possible to measure the opening and closing degree of the on-off valve 2 based on the output voltage. Note that, although the resistor 11 is drawn as a straight line in Fig. 3 for ease of explanation, the resistor 11 may also be formed as an arc.

[0014] FIG. 4A is a schematic diagram showing the relationship between resistor 11, the position of brush 12 sliding on surface 11S, and rotation angle X, and FIG. 4B is a graph showing the deviation of the output voltage from an ideal curve according to rotation angle X.

[0015] 4A, the brush 12 slides on the surface 11S of the resistor 11 in the range between the rotation angles Xi and Xf. A sliding trajectory 12T indicates the range in which the brush 12 slides. That is, the contact position between the resistor 11 and the brush 12 at the rotation angle Xi is one end of the range in which the brush 12 slides, that is, the position where the rotation angle to be detected is the minimum value, and can also be said to be the position of the rotation angle of 0° as the resistor position sensor 1. The resistance R of the resistor 11 can be divided into a resistance Rb of a portion where the brush 12 slides from the rotation angle X of Xi to Xf, and a resistance Ri of a portion where the brush 12 does not slide from the rotation angle X of 0° to Xi.

[0016] Since the brush 12 does not slide in the range from rotation angle 0 to Xi, the resistance Ri is not affected by wear of the resistor 11 and the brush 12. Therefore, the value of the resistance Ri after a durability test that evaluates the state of long-term use does not change from the initial resistance value. In contrast, since the brush 12 slides in the range from rotation angle Xi to Xf, the value of the resistance Ri after the durability test is affected by wear of the resistor 11 and the brush 12. Therefore, the value of the resistance Rb after the durability test changes from the initial value if wear occurs in the resistor 11 and the brush 12.

[0017] In FIG. 4B, an ideal curve showing the relationship between the rotation angle and the output voltage at an initial stage is shown by a dotted line. As shown in the figure, initially, there is good linearity between the rotation angle and the output voltage. However, as the resistor position sensor 1 is used repeatedly, a deviation occurs between the output voltage and the ideal curve. There are two reasons why the output voltage deviates from the ideal curve: the resistor 11 wears out (first case), and the brush 12 wears out and a layer of wear powder is formed (second case).

[0018] <First Case> When the brush 12 slides over the resistor 11, the resistor 11 wears at the sliding locus 12T, and the cross-sectional area of ​​the resistor 11 at the sliding locus 12T decreases, so the resistance value of the resistor Rb increases. As a result, the output voltage decreases from the initial value. If the output voltage Vi, the resistance Ri, and the resistance Rb at the rotation angle Xi of the idling position are Vi, Ri, and Rb, respectively, then Vi=Ri / (Ri+Rb). Therefore, when the resistor 11 wears and the resistance Rb increases due to repeated use, the output voltage Vi at the idling position decreases. Therefore, the resistor 11 can be made to contain carbon fiber as a reinforcing material to suppress wear of the resistor 11.

[0019] 5A is a graph showing a schematic diagram of a change in output voltage Vi at an idling position caused by wear of resistor 11 with an increase in the number of sliding movements. In the first case, output voltage Vi decreases with an increase in the number of sliding movements caused by repeated use.

[0020] <Second Case> When the brush 12 wears due to sliding over the resistor 11, a layer of wear powder of the brush 12 is formed around the contact end 12E (see FIG. 3) of the brush 12. This layer of wear powder becomes a path for current flowing between the brush 12 and the resistor 11, in addition to the contact end 12E that contacts the surface 11S of the resistor 11. As a result, the resistance value of the resistor Rb decreases from its initial value, and the output voltage increases from its initial value. Therefore, the output voltage Vi=Ri / (Ri+Rb) at the idling position increases as the brush 12 wears.

[0021] 5B is a graph showing a change in the output voltage Vi at the idling position due to wear of the brush 12 with an increase in the number of sliding movements. In the second case, the output voltage Vi at the idling position increases with an increase in the number of sliding movements.

[0022] Conventionally, repeated operation of the resistor position sensor 1 causes wear in the resistor 11 and the brush 12, and this wear causes a decrease in the linearity of the output voltage. Of these, when the resistor 11 wears (first case), it is impossible to prevent the resistance Rb from increasing. In contrast, wear of the brush 12 can be prevented from changing in resistance Rb if wear powder can be removed from the vicinity of the contact end 12E. For this reason, it can be said that wear of the resistor 11 has a greater effect on the accuracy of the linearity of the output voltage of the resistor position sensor 1 than wear of the brush 12. Therefore, conventionally, mainly to prevent wear of the resistor 11, the hardness of the resistor 11 is made greater than the hardness of the brush 12, and the amount of wear of the resistor 11 is made as small as possible.

[0023] However, as the demand for durability and linearity increases from the viewpoint of global warming and environmental measures, the influence of wear of the brush 12 can no longer be ignored. For example, in variable resistance type throttle valve sensors for motorcycles, the demand for linearity has increased further with the recent evolution of electronic control of motorcycles, and the problem of changes in the linearity characteristics of the output voltage has become apparent. In other words, as the demand for linearity has increased, it has become increasingly necessary to suppress the fluctuation in the linearity of the output voltage caused by the formation of a metal film of wear powder on the brush 12. For this reason, it has become difficult to deal with this issue only by innovating and improving the resistor 11, which was previously used.

[0024] Therefore, the present invention suppresses the wear of resistor 11 and brush 12 by specifying the relationship between the hardness of resistor 11 and brush 12. In addition, the influence of wear powder is further suppressed by using a lubricant that is highly effective in removing wear powder of brush 12 from the periphery of contact end 12E.

[0025] 1 is a cross-sectional view showing a schematic structure of a resistor position sensor 1. As shown in the figure, the resistor position sensor 1 includes a resistor 11 and a brush 12, and a lubricant 13 is interposed between the resistor 11 and the brush 12 (at the interface).

[0026] The resistor 11 is manufactured by, for example, mixing carbon black 111 and carbon fiber 112 with binder resin 113, thinly applying the ink onto an insulating substrate by screen printing or the like, and baking it. Carbon black (hereinafter also referred to as CB) 111 mainly provides electrical conductivity to the resistor 11, and carbon fiber (hereinafter also referred to as CF) 112 mainly provides wear resistance to the resistor 11.

[0027] The CF112 can preferably be pulverized carbon fiber produced by pulverizing carbon fiber extending in a fibrous form with a diameter of about 6 to 10 μm. When pulverized CF is used as the 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. The longitudinal direction here refers to the direction in which the carbon fiber extended before being pulverized.

[0028] The carbon fiber used as CF112 is heat-treated and is made of graphite foils (thin layers) stacked along the longitudinal direction. In Fig. 1, the arrow indicates the direction V perpendicular to the graphite surface formed along the longitudinal direction of CF112. As shown in the figure, each CF112 is dispersed in binder resin 113 in which CB111 is uniformly dispersed, with the direction V perpendicular to the graphite surface random (the graphite surface faces in a random direction).

[0029] As will be described later, the hardness of CF112 is anisotropic and is greatest in the direction V perpendicular to the graphite surface. The hardness of CF112 is 150 to 250 [kgf / mm 2 ] and can be adjusted by heat treatment.

[0030] The hardness of CF112 is measured using a sample in which CF112 is dispersed in binder resin 113. Although the hardness of CF112 in the V direction cannot be measured directly, it is estimated that the maximum hardness value actually measured is approximately equal to the value obtained when the direction in which the sample is pressed (pressure direction) coincides with the V direction of CF112. Therefore, it is assumed that the maximum value of the actual measured values ​​approximately coincides with the hardness of CF112 in the V direction. When the angle between the pressure direction and the V direction increases and the hardness of CF112 decreases, the hardness of the binder resin 113 in which CF112 is dispersed affects the measured value. Then, as the angle approaches a right angle, the measured value of the hardness of CF112 gradually approaches the hardness of the binder resin 113, and the minimum value approximately coincides with the binder resin hardness. It can be estimated that the average of the measured hardness values ​​corresponds to the result measured when the angle between the V direction of CF112 and the pressure direction of the measuring indenter is about 45 degrees.

[0031] The hardness in the present invention refers to a value measured using a microhardness tester called a nanoindenter based on the test method (nanoindentation method) defined in the international standard (ISO14577:2015). The nanoindenter differs from the Vickers hardness tester, whose measuring indenter is a rhomboidal indenter, in that the measuring indenter is a triangular indenter. The hardness measured using the nanoindenter can be converted to Vickers hardness using a Vickers hardness tester.

[0032] 11 is a schematic diagram for explaining hardness measurement of carbon fiber. When measuring the hardness of resistor 11 in which CF112 is dispersed in binder resin 113, the measured value differs depending on the position of measuring indenter 15. This is because the angle θ between the V direction of CF112 and the pressure direction of measuring indenter 15 changes depending on the position of measuring indenter 15 on surface 11S of resistor 11.

[0033] 11, θc<θb<θa, and the smaller the angle θ, the greater the hardness, so the hardness increases in the order of positions 15c>15b>15a of the measuring indenter 15. As θ approaches a right angle, the hardness of CF 112 approaches the hardness of binder resin 113, and roughly coincides with the hardness of binder resin 113 at position 15d where no CF 112 is present on surface 11S. In the present invention, the average of the measured values ​​is taken as the hardness Hc of the carbon fiber of CF 112.

[0034] The binder resin 113 is a dispersion medium that disperses CB and CF. The hardness of the binder resin 113 is, for example, 50 to 80 [kgf / mm 2 ] is preferable, and 60 to 70 [kgf / mm 2 For example, the binder resin 113 may be a phenol resin, an epoxy resin, a melamine resin, an unsaturated polyester, or the like.

[0035] The content of the binder resin 113 is preferably 2 to 6 parts by volume, and more preferably 3 to 5 parts by volume, per 1 part by volume of the CF 112. The content of the binder resin 113 is preferably 1 to 5 parts by volume, and more preferably 1.5 to 4 parts by volume, per 1 part by volume of the total of the binder resin 113 and the CF 112 and / or the CB 111.

[0036] The resistor 11 can be manufactured using an ink obtained by mixing, for example, 60 to 80 volume % of phenol resin and 20 to 40 volume % of the total of CB111 and CF112 (hereinafter referred to as carbon as appropriate). The content ratio of CB111 to CF112 may be adjusted appropriately according to the resistance value and hardness of the resistor 11, and may be, for example, 0.2 to 2 volume parts of CB111 for every 1 volume part of CF112 (1 volume part of carbon fiber).

[0037] Ink containing 60 to 70 volume % phenol resin and 30 to 40 volume % carbon is preferred from the viewpoint of making the resistance value of resistor 11 an appropriate value for resistor position sensor 1. From the same viewpoint, the volume ratio of the content of CB111 to the content of CF112 is preferably 1:2 to 2:1.

[0038] The brush 12 is made of a conductive metal. The conductive metal has a hardness of 280-340 [kgf / mm 2 It is preferable that the brush 12 has a thickness of about 50 to 70 microns. In this case, the thickness is about 20 times the preferable diameter of the CF 112, which is 2.5 to 3.5 microns. Note that since Fig. 1 is a schematic diagram, the actual sizes of the CF 112 in the resistor 11 and the brush 12 are ignored.

[0039] The load of the brush 12 can be, for example, 1 to 10 g.

[0040] FIG. 6A is a schematic diagram showing a carbon fiber used as a raw material for CF112, and FIG. 6B is a schematic diagram showing an enlarged microstructure of CF112 obtained by pulverization. As described above and shown in FIG. 6A, carbon fiber is made of graphite foils (thin layers) stacked along the longitudinal direction. Therefore, when carbon fiber is pulverized, it is broken so that the direction P along the stacked graphite surfaces becomes the longitudinal direction. The hardness of the pulverized CF used as CF112 is significantly different between the direction P parallel to the graphite surfaces and the direction V perpendicular to the graphite surfaces. The hardness of CF112 is greater in the direction V than in the direction P.

[0041] 7 is a graph illustrating the anisotropy of the hardness of CF 112. Hereinafter, the hardness of CF 112, which is pulverized CF, will be described with reference to this figure. The hardness of CF 112 is maximum in a direction V perpendicular to the graphite surface of CF 112, and is minimum in a direction P parallel to the graphite surface. The hardness of CF 112 in the direction parallel to the graphite surface where the hardness is minimum is approximately equal to the hardness of binder resin 113.

[0042] 1, the CF112 are uniformly dispersed three-dimensionally so that the direction V perpendicular to the graphite surface is a random direction. Therefore, the hardness (average value) of the resistor 11 actually measured is an intermediate value between the hardness Hv of the CF112 in the direction V and the hardness Hr of the binder resin 113. In other words, it can be said that the measured value of the resistor 11 is approximately the same as the hardness Hc of the CF112 dispersed at an angle of approximately 45° from the direction V.

[0043] Therefore, the maximum local hardness assumed in resistor 11, i.e., the hardness of the portion of surface 11S of resistor 11 where CF112 faces direction V, is 2×(Hc−Hr)+Hr=2×Hc−Hr. The wear of brush 12 is affected more by the hardness of CF112 present in resistor 11 at the maximum hardness than by the average hardness of CF112.

[0044] Therefore, the hardness 2×Hc−Hr is set to be equal to the hardness Hb of the brush 12, and not smaller than the hardness Hb of the brush 12. In other words, the hardness of the resistor 11 and the hardness of the brush 12 are set to satisfy the following formula (1). This makes it possible to minimize wear of both the resistor 11 and the brush 12. Hb≦2×Hc-Hr≦1.2×Hb (1) Hb: Average value of hardness of brush 12 Hc: Average value of hardness measured for CF112 Hr: Average value of hardness measured for binder resin 113

[0045] Conventionally, the amount of wear of resistor 11 was minimized based on the idea that wear of resistor 11 would be a more serious defect than wear of brush 12. However, in the present invention, in order to minimize wear of both resistor 11 and brush 12, the hardness of resistor 11 and brush 12 is designed to satisfy the relationship of formula (1) above. Note that 2×Hc-Hr can be adjusted by graphitizing CF112 through heat treatment to make it more slippery.

[0046] In the resistor position sensor 1, the hardness of the resistor 11 and the hardness of the brush 12 are set so as to satisfy the formula (1), thereby suppressing the generation of wear powder caused by the brush 12 sliding on the resistor 11. However, when wear powder is generated and gets caught in the interface between the resistor 11 and the brush 12, the resistance R of the resistor changes. This causes the contact resistance of the resistor position sensor 1 to increase or decrease, generating noise in the output voltage. Therefore, although a lubricant 13 was originally applied between the resistor 11 and the brush 12 to reduce wear of the resistor 11 and the brush 12, in the resistor position sensor 1 of the present application, the lubricant 13 also has the function of removing wear powder.

[0047] From the viewpoint of heat resistance and durability, the lubricant 13 is preferably perfluoropolyether (hereinafter, appropriately abbreviated as PFPE), which has a low vapor pressure, that is, a high boiling point.

[0048] From the viewpoint of preventing the formation of wear powder accumulation near the brush 12, PFPEs without a branched structure are preferred. From the same viewpoint, PFPEs with a small number of oxygen bonds that cause wear powder to become entangled are preferred. For this reason, PFPEs with a linear structure with few oxygen bonds are preferred. Preferred PFPEs with a linear structure include fluorine-based PFPEs having the following structural formula: F-(CF2CF2CF2O)n-CF2CF3

[0049] Moreover, from the viewpoint of efficiently removing wear powder in the vicinity of contact end 12E of brush 12, the surface tension of PFPE used as lubricant 13 is preferably 20 mN / m or less. From the same viewpoint, lubricant 13 is preferably one having a small number of functional groups.

[0050] That is, from the viewpoint of suppressing the occurrence of output noise in the output voltage when the number of sliding movements of the brush 12 increases, it is preferable that the lubricant 13 is a linear PFPE having a surface tension of 20 mN / m or less. An example of a commercially available PFPE having such preferable properties is Demnum (product name, manufactured by Daikin Industries, Ltd.).

[0051] The embodiments disclosed in this specification are illustrative in all respects and are not limited to these embodiments. The scope of the present invention is indicated by the claims rather than the description of the above-mentioned embodiments, and is intended to include all modifications within the meaning and scope of the claims. EXAMPLES

[0052] [Example 1] A resistor with a surface hardness Hc (average hardness of the crushed carbon fiber) of 200 was formed using crushed carbon fiber as the carbon fiber and phenol resin (hardness Hr=70) as the binder resin. A resistor position sensor was manufactured using the resistor and a brush with a measured hardness (Hb) of 310. Demnum S65 (product name, manufactured by Daikin Industries, Ltd., perfluoropolyether, surface tension 18.0 mN / m) was used as the lubricant for the resistor position sensor. The relationship between the hardness Hc of the carbon fiber, the hardness Hr of the binder resin, and the hardness Hb at the contact end of the brush (slider) in the resistor position sensor of this embodiment is as shown in the following formula. 2×Hc-Hr=1.06Hb The hardness of each of the crushed carbon fiber, the phenolic resin, and the brush was calculated by converting the nanoindenter measurement value into a Vickers hardness value.

[0053] [Example 2] A resistor position sensor was manufactured in the same manner as in Example 1, except that a resistor with a surface hardness Hc of 190 was used. The relationship between Hc, Hr and Hb in the resistor position sensor of this example was as shown in the following formula. 2×Hc-Hr=1.0Hb

[0054] [Example 3] A resistor position sensor was manufactured in the same manner as in Example 1, except that a resistor with a surface hardness Hc of 210 was used. The relationship between Hc, Hr and Hb in the resistor position sensor of this example was as shown in the following formula. 2×Hc-Hr=1.13Hb

[0055] [Comparative Example 1] A resistor position sensor was manufactured in the same manner as in Example 1, except that a resistor with a surface hardness Hc of 250 was used. The relationship between Hc, Hr, and Hb in the resistor position sensor of this comparative example was as shown in the following formula. 2×Hc-Hr=1.39Hb

[0056] 8A and 8B are graphs showing the change in output voltage and total resistance value with an increase in the number of sliding movements, where FIG. 8A shows the results of the resistor position sensor of Example 1, and FIG. 8B shows the results of the resistor position sensor of Comparative Example 1. Also, in Examples 2 and 3, as in Example 1 shown in FIG. 8A, the change in output voltage and total resistance value with an increase in the number of sliding movements was extremely small. In this way, by using a resistor and a brush with hardness that satisfies the relationship shown in formula (1), a resistor position sensor with an extremely small change in output voltage (ΔVi) and total resistance change rate (R) at the idling position was manufactured. In contrast, the resistor position sensor of Comparative Example 1, which does not satisfy the relationship shown in formula (1), had a large change in output voltage and total resistance value with an increase in the number of sliding movements, as shown in FIG. 8B.

[0057] 9A and 9B are photographs substituting for drawings showing the state of resistor 11 and brush 12 after the durability test, with FIG. 9A showing the results of Example 1 and FIG. 9B showing the results of Comparative Example 1. As in Example 1 shown in Fig. 9A, by using resistor 11 and brush 12 having hardness satisfying the relationship shown in formula (1), it was possible to suppress the amount of wear of brush 12 and prevent adhesion of wear powder to contact end 12E. Then, sliding locus 12T in which a metal layer of wear powder adhering to surface 11S of resistor 11 is hardly observed was formed. Also, in Examples 2 and 3, similarly to Example 1 shown in Fig. 9A, a sliding locus 12T in which the amount of wear is small, wear powder does not adhere to contact end 12E, and a metal layer of wear powder is hardly observed was formed. In contrast, when resistor 71 and brush 72 having hardness that does not satisfy the relationship shown in equation (1) were used, as in comparison example 1 shown in Figure 9B, the amount of wear of brush 72 increased, wear powder adhered to contact end 72E, and brush sliding trajectory 72T was formed in which a metal layer of wear powder adhered to surface 71S of resistor 71.

[0058] As described above, by making the hardness of the resistor 11 and the brush 12 satisfy the relationship shown in equation (1), a resistor position sensor 1 was obtained in which output fluctuations and noise generation at the idling position are suppressed even after the number of sliding movements increases due to long-term use.

[0059] <Example 4> For the resistor position sensor of Example 1, the noise intensity generated when the ambient temperature was periodically changed in the range of -30°C to 120°C while the brush 12 was repeatedly slid over the surface 11S of the resistor 11 was measured.

[0060] <Comparative Example 2> The noise intensity was measured in the same manner as in Example 4 for a resistor position sensor using Fomblin M30 (product name, manufactured by Solvay, perfluoropolyether, surface tension 25 mN / m) as a lubricant instead of Demnum S65 in Example 1.

[0061] 10A and 10B are graphs showing noise intensity, with Fig. 10A showing the measurement results of Example 4 and Fig. 10B showing the measurement results of Comparative Example 2. In the figures, the temperature profile of the ambient temperature is shown as a line graph, and the noise intensity is shown as a bar graph. The vertical axis of noise indicates the strength of the noise, with the higher the axis, the greater the noise generated.

[0062] 10A, the resistor position sensor of Example 4 did not show any noise generation at 700K (700,000 times) of repeated sliding. In contrast, the resistor position sensor of Comparative Example 2 showed noise generation from when the number of repeated sliding exceeded 150K (150,000 times). Based on this result, from the viewpoint of suppressing noise generation, it can be said that perfluoropolyether with a surface tension of 20 mN / m or less is preferable as a lubricant. [Industrial Applicability]

[0063] INDUSTRIAL APPLICABILITY As described above, the resistor position sensor of the present invention suppresses output fluctuations and noise generation at the idling position, and is useful as a throttle position sensor for motorcycles. [Explanation of symbols]

[0064] 1: Resistor position sensor 2: Opening and closing valve 3: Air 4: Gasoline 5: Mixture 6: Engine 11: Resistor 11S:Surface 111: Carbon black 112: Carbon fiber 113: Binder resin 12: Brush (slider) 12E: Contact end 12T: Sliding trajectory 13: Lubricants 15: Measuring indenter 15a to 15d: Position of the measuring indenter 71: Resistor 71S:Surface 72: Brush 72E: Contact end 72T: Brush sliding path Hb, Hc, Hv, Hr: Hardness P, V: Direction R, Rb, Ri: resistance Vi: Output voltage at idle position X, Xf: rotation angle Xi: Rotation angle at idle position θ, θa to θc: angles between the V direction of the carbon fiber and the pressure direction of the measuring indenter

Claims

1. A resistor position sensor comprising a resistor and a slider that slides on the resistor, the output of which changes depending on the position at which the slider contacts the resistor, the resistor contains, as components, a binder resin and carbon fibers dispersed in the binder resin; When the hardness of the carbon fiber is Hc, the hardness of the binder resin is Hr, and the hardness of the contact end of the slider that contacts the resistor is Hb, the hardness is expressed by the following formula (1): Hb≦2×Hc−Hr≦1.2×Hb (1) The relationship shown in The various hardnesses used in the formula (1) are average values ​​measured using a microhardness tester equipped with a triangular indenter as a measuring indenter based on the test method defined in ISO14577:2015, and converted into Vickers hardness. Resistor position sensor.

2. The carbon fiber is milled carbon fiber.

2. The resistor position sensor according to claim 1.

3. A lubricant is provided between the slider and the resistor, The lubricant is a linear perfluoropolyether.

3. The resistor position sensor according to claim 1 or 2.

4. The lubricant has a surface tension of 20 mN / m or less.

4. The resistor position sensor according to claim 3.

5. The resistor has a binder resin content of 2 to 6 parts by volume relative to 1 part by volume of the carbon fiber.

3. The resistor position sensor according to claim 1 or 2.

6. The resistor further comprises carbon black, The content of the 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.

6. The resistor position sensor according to claim 5.

7. The resistor has a binder resin content of 1 part by volume or more and 5 parts by volume or less per 1 part by volume of the binder resin and / or the carbon black in total.

7. The resistor position sensor according to claim 6.

8. The hardness measurement of the carbon fiber is performed on the carbon fiber located near the surface of the binder resin.

3. The resistor position sensor according to claim 1 or 2.

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