JP2024063750A - Position Detection Device - Google Patents

Abstract

[Problem] To provide a position detection device that can be made small and lightweight. [Solution] A stroke sensor 1 includes an excitation coil 300 arranged along a rack shaft 13, and first to fourth detection coils 31 to 34 that output voltages according to the positions of first and second detectable parts 21, 22 that move together with the rack shaft 13 due to a magnetic field generated by the excitation coil 300. When the rack shaft 13 moves in one direction, the output voltages of the first to fourth detection coils 31 to 34 change in a sinusoidal shape over the entire period from when the first to fourth detection coils 31 to 34 and at least parts of the first and second detectable parts 21, 22 start to align in a direction perpendicular to the moving direction of the rack shaft 13 until the entire first and second detectable parts 21, 22 are no longer aligned in a direction perpendicular to the moving direction of the rack shaft 13 with the first to fourth detection coils 31 to 34. [Selected Figure] Figure 5

Description

The present invention relates to a position detection device that detects the position of a moving member that moves forward and backward in a predetermined moving direction.

Conventionally, position detection devices that detect the position of a moving member that moves forward and backward in a specific direction of movement are used in various fields such as industrial machinery and automobiles.

The electromagnetic induction type linear scale described in Patent Document 1 has a coil array consisting of a predetermined number of coil elements excited by a first AC signal, a magnetic member that relatively displaces the outside of the coil array along its axis, and a detection unit that detects the position of the magnetic member relative to the coil array from the output voltage of each coil element. The magnetic member changes the amplitude of the output voltage of the coil element depending on the positional relationship with the coil element. The detection unit absolutely detects the relative position of the magnetic member with respect to the coil array from the phase difference between the first AC signal and a second AC signal obtained by combining the differential outputs between the coil elements.

JP 2009-2770 A

In the electromagnetic induction type linear scale described in Patent Document 1, a large number of coil elements must be arranged in a row across the entire range of movement of the magnetic member, which increases the installation size and weight. Therefore, the present invention aims to provide a position detection device that can be made smaller and lighter.

The present invention aims to solve the above problems and provides a position detection device that detects the position of a moving member that moves forward and backward in a predetermined moving direction, comprising an excitation coil arranged to extend along the moving member in the moving direction, a detection coil that outputs a voltage according to the position of a detected part that moves with the moving member within a predetermined detection range in the moving direction due to a magnetic field generated by the excitation coil, and a calculation unit that calculates the position of the moving member based on the output voltage of the detection coil, the detected part has a predetermined length in the moving direction, a voltage is generated in the detection coil due to the difference in magnetic field strength between a part corresponding to the detected part and a part not corresponding to the detected part, and when the moving member moves in one direction, the output voltage of the detection coil changes in a sinusoidal manner over the entire period from when the detection coil and at least a part of the detected part start to align in a direction perpendicular to the moving direction until the entire detected part is no longer aligned with the detection coil in a direction perpendicular to the moving direction.

The present invention makes it possible to reduce the size and weight of position detection devices.

1 is a schematic diagram of a vehicle equipped with a steer-by-wire steering device including a stroke sensor as a position detection device according to an embodiment of the present invention. 2. A cross-sectional view taken along line AA in FIG. FIG. 3 is a perspective view showing the board, the CPU, the case member, the rack shaft, and a part of the housing. 1A is a perspective view showing a target, and FIG. 1B is a plan view of the target. 1 is an explanatory diagram showing wiring patterns formed on first to fourth metal layers of a substrate as seen through from the rear surface side; 4A to 4D are plan views showing the first to fourth metal layers, respectively, as viewed from the rear surface side. FIG. 2 is an explanatory diagram showing a first detection coil together with two first detection portions of a target. 5 is a graph showing an example of the relationship between a supply voltage supplied from a power supply unit to an excitation coil and an output voltage of a first detection coil. 13 is a graph showing the relationship between the peak voltage of a first detector coil within one period of a supply voltage supplied to an excitation coil and the peak voltage of a second detector coil within one period of the supply voltage when the rack shaft moves in one direction at a constant speed. 5 is a flowchart showing an example of a calculation process performed by a CPU to obtain a position of a rack shaft. 1 is a graph showing a relationship between the rack shaft position calculated by equations (1) and (2) and the rack shaft position calculated by equation (3) or (4). 10 is an explanatory diagram showing a configuration example of a detection coil set according to a comparative example, together with two first detection portions of a target. FIG. 11 is a graph showing a comparison of the results of calculation of the rack shaft position calculated by equation (1) based on the output voltage of a first detection coil and the rack shaft position calculated by an arithmetic formula similar to equation (1) based on the output voltage of a detection coil set according to a comparative example. 11 is an explanatory diagram showing a detection coil according to a first modified example together with a target to be combined with the detection coil; FIG. 15 is a diagram showing an example of a configuration in which a first detection coil group and a second detection coil group are configured using detection coils having the configuration shown in FIG. 14. 13 is an explanatory diagram showing a detection coil according to a second modified example, together with a target to be combined with this detection coil. FIG. FIG. 13 is an explanatory diagram showing a detection coil according to Modification 3 together with a target to be combined with this detection coil. FIG. 13 is an explanatory diagram showing a detection coil according to a fourth modified example, together with a target to be combined with this detection coil.

[Embodiment]
Fig. 1 is a schematic diagram of a vehicle equipped with a steer-by-wire steering device 10 having a stroke sensor 1 as a position detection device according to an embodiment of the present invention. Fig. 1 shows the steering device 10 as seen from the rear side in the vehicle longitudinal direction, with the right side of the drawing corresponding to the right side in the vehicle width direction and the left side of the drawing corresponding to the left side in the vehicle width direction. Note that in the following explanations referring to the drawings, the terms "right" and "left" may be used, but these terms are used for convenience of explanation and do not limit the direction of arrangement of the stroke sensor 1 in actual use.

As shown in FIG. 1, the steering device 10 includes a stroke sensor 1, a tie rod 12 connected to steered wheels 11 (left and right front wheels), a rack shaft 13 connected to the tie rod 12, a cylindrical housing 14 that accommodates the rack shaft 13, a worm reduction mechanism 15 having a pinion gear 151 meshed with rack teeth 131 of the rack shaft 13, an electric motor 16 that applies a moving force in the vehicle width direction to the rack shaft 13 via the worm reduction mechanism 15, a steering wheel 17 that is steered by the driver, a steering angle sensor 18 that detects the steering angle of the steering wheel 17, and a steering control device 19 that controls the electric motor 16 based on the steering angle detected by the steering angle sensor 18.

The rack shaft 13 is a moving member whose position relative to the housing 14 is detected by the stroke sensor 1. The direction of movement of the rack shaft 13 is an axial direction parallel to the central axis C of the rack shaft 13.

In FIG. 1, the housing 14 is shown in phantom lines. The rack shaft 13 is supported by a pair of rack bushes 141 attached to both ends of the housing 14. The worm reduction mechanism 15 has a worm wheel 152 and a worm gear 153, and a pinion gear 151 is fixed to the worm wheel 152. The worm gear 153 is fixed to a motor shaft 161 of the electric motor 16.

The electric motor 16 generates torque by the motor current supplied from the steering control device 19, and rotates the worm wheel 152 and the pinion gear 151 via the worm gear 153. When the pinion gear 151 rotates, the rack shaft 13 moves forward and backward linearly along the vehicle width direction, and the left and right steered wheels 11 are steered. The rack shaft 13 can move to the right and left in the vehicle width direction within a predetermined range from a neutral position when the steering angle is zero.

In FIG. 1, the stroke range R, which corresponds to the maximum travel distance of the rack shaft 13 when the steering wheel 17 is steered from the maximum steering angle on one side to the other side, is indicated by a double arrow. The stroke sensor 1 is capable of detecting the absolute position of the rack shaft 13 relative to the housing 14 throughout this stroke range R.

The stroke sensor 1 includes a target 2, which is a conductive member attached to the rack shaft 13, a substrate 3 arranged opposite the target 2, a calculation unit 101 configured with a CPU (computer-processing unit) 100 mounted on the substrate 3, a case member 5 having a connector 50, a power supply unit 102 that generates a high-frequency voltage, and a cable 103 for connecting the connector 50 attached to the case member 5 with the power supply unit 102 and the steering control device 19. The substrate 3 is housed in the case member 5 and arranged parallel to the rack shaft 13, and is fixed immovably relative to the housing 14.

The stroke sensor 1 detects the axial (moving) position of the rack shaft 13 relative to the housing 14, and outputs the detected position information to the steering control device 19 via the cable 103. The steering control device 19 controls the electric motor 16 so that the position of the rack shaft 13 detected by the stroke sensor 1 corresponds to the steering angle of the steering wheel 17 detected by the steering angle sensor 18.

Figure 2 is a cross-sectional view taken along line A-A in Figure 1. Figure 3 is a perspective view showing the board 3, the CPU 100, the case member 5, the rack shaft 13, and a portion of the housing 14. Figure 4(a) is a perspective view showing the target 2, and Figure 4(b) is a plan view of the target 2.

The rack shaft 13 is a rod-shaped body made of steel, such as carbon steel for mechanical construction. The housing 14 is made of a cylindrical aluminum alloy, for example, formed by die-casting. The housing 14 has an opening 140 that opens vertically upward, and the case member 5 is attached so as to close this opening 140.

The case member 5 has a case body 51 and a case lid 52. The case body 51 is provided with a plurality of fixing parts 510 for fixing to the housing 14, and these fixing parts 510 are fixed to fixed parts 142 provided on the housing 14 by bolts 500 (see FIG. 2). A packing 53 is disposed between the case body 51 and the housing 14 to prevent moisture from entering through the opening 140 of the housing 14. The case body 51 and the case lid 52 are made of, for example, a resin material that is an insulator, but one or both of the case body 51 and the case lid 52 may be conductive.

The case body 51 has a bottom plate 511 that faces the front surface 3a of the substrate 3, and a peripheral side wall 512 provided around the bottom plate 511. The substrate 3 is disposed between the bottom plate 511 of the case body 51 and the case lid 52. The case lid 52 is fixed to the open end of the peripheral side wall 512, for example by adhesive. A connector 50 is attached to the case lid 52.

The substrate 3 is a four-layer substrate in which a flat base material 30 made of a dielectric material such as FR4 (glass fiber impregnated with epoxy resin and subjected to a thermosetting treatment) is disposed between the first to fourth metal layers 301 to 304. The thickness of each base material 30 is, for example, 0.3 mm. The first to fourth metal layers 301 to 304 are made of, for example, copper, and each layer has a thickness of, for example, 18 μm. The substrate 3 is a flat rectangle whose long side (longitudinal direction) is the same as the movement direction of the rack shaft 13. The substrate 3 is not limited to a rigid substrate, and may be a flexible substrate.

The target 2 is generally in the shape of a long plate, and is fixed to the rack shaft 13 so that its longitudinal direction is parallel to the rack shaft 13. The target 2 has an opposing surface 2a parallel to the substrate 3, an attachment surface 2b to the rack shaft 13, end surfaces 2c and 2d in the longitudinal direction, one side surface 2e in the lateral direction, and the other side surface 2f in the lateral direction. The opposing surface 2a of the target 2 faces the bottom plate 511 of the case body 51 with a small gap therebetween. The opposing surface 2a of the target 2 may also be directly opposed to the surface 3a of the substrate 3.

The target 2 has a plurality of first detectable parts 21 formed along one side surface 2e and a plurality of second detectable parts 22 formed along the other side surface 2f, and these first detectable parts 21 and second detectable parts 22 move together with the rack shaft 13. The first detectable parts 21 and second detectable parts 22 each have a predetermined length in the moving direction of the rack shaft 13. The first detectable parts 21 and second detectable parts 22 are rectangular in shape when viewed from the opposing surface 2a side.

The material of the target 2 is preferably highly conductive, and for example, an aluminum alloy or a copper alloy can be suitably used. The rack shaft 13 is formed with a flat mounting surface 13a for mounting the target 2, and the target 2 is fixed to the mounting surface 13a by, for example, welding. Note that the shaft material of the rack shaft 13 may be machined to form multiple detection portions.

The first detectable portion 21 and the second detectable portion 22 are formed as recesses recessed from the opposing surface 2a toward the rack shaft 13 side. In this embodiment, the first detectable portion 21 and the second detectable portion 22 penetrate between the opposing surface 2a and the mounting surface 2b in the thickness direction of the target 2. The first detectable portion 21 opens on one side surface 2e, and the second detectable portion 22 opens on the other side surface 2f. In this embodiment, five first detectable portions 21 and six second detectable portions 22 are formed at equal intervals along the longitudinal direction of the target 2.

Figure 5 is an explanatory diagram showing the wiring patterns formed on the first to fourth metal layers 301 to 304 of the substrate 3 as seen through from the rear surface 3b side. Figures 6(a) to (d) are plan views showing the first to fourth metal layers 301 to 304, respectively, as seen from the rear surface 3b side.

In Figure 5 and Figures 6(a) to (d), the wiring pattern of the first metal layer 301 is shown by a solid line, the wiring pattern of the second metal layer 302 is shown by a dashed line, the wiring pattern of the third metal layer 303 is shown by a dashed line, and the wiring pattern of the fourth metal layer 304 is shown by a dashed double-dot line.

The substrate 3 is formed with a plurality of through holes 350 (see FIG. 3) for connecting the terminals of the connector 50, and first to fourth vias 351 to 354 for interlayer connection of the wiring patterns of each layer. In addition, a CPU 100 is mounted on the rear surface 3b of the substrate 3. The CPU 100 has a calculation processing function for executing calculation procedures according to a program, and an AD conversion (analog-to-digital conversion) function.

The substrate 3 is formed with first to fourth detection coils 31 to 34 for detecting the position of the target 2, and first to fourth transmission lines 36 to 39 for transmitting the output voltages of the first to fourth detection coils 31 to 34 to the calculation unit 101. The first detection coil 31 and the second detection coil 32 constitute a first detection coil set 3A, and the third detection coil 33 and the fourth detection coil 34 constitute a second detection coil set 3B.

In addition, an excitation coil 300 is formed on the substrate 3, extending in the axial direction of the rack shaft 13 along the rack shaft 13, so as to surround the first to fourth detection coils 31 to 34. In this embodiment, as shown in FIG. 6(a), the excitation coil 300 is formed on the first metal layer 301. Note that the excitation coil 300 may be formed across multiple metal layers among the first to fourth metal layers 301 to 304.

The first detection coil group 3A and the second detection coil group 3B are arranged in a direction perpendicular to the extension direction of the excitation coil 300 (short side direction of the substrate 3). The multiple first detection target parts 21 of the target 2 are provided corresponding to the first detection coil group 3A, and the multiple second detection target parts 22 are provided corresponding to the second detection coil group 3B. That is, when the substrate 3 is viewed from the back surface 3b side, the first detection coil group 3A and the first detection target parts 21 overlap in a direction perpendicular to the substrate 3, and the second detection coil group 3B and the second detection target parts 22 overlap in a direction perpendicular to the substrate 3. Hereinafter, the direction perpendicular to the substrate 3 is referred to as the substrate perpendicular direction. The substrate perpendicular direction is a direction perpendicular to the movement direction of the rack shaft 13.

The first to fourth detection coils 31 to 34 output voltages according to the positions of the first and second detection parts 21 and 22 of the target 2 within a predetermined detection range in the moving direction of the rack shaft 13 due to the magnetic field generated by the excitation coil 300. The CPU 100 calculates the position of the rack shaft 13 based on the output voltages of the first to fourth detection coils 31 to 34.

Figure 7 is an explanatory diagram showing the first detection coil 31 together with the two first detectable portions 21 of the target 2. In Figures 5 to 7, the left-right direction of the drawing corresponds to the longitudinal direction of the substrate 3, and the up-down direction of the drawing corresponds to the lateral direction of the substrate 3. The terms "left," "right," "upper," and "lower" in the following explanation are used for convenience of explanation and refer to the respective directions in Figures 5 to 7.

In FIG. 7, the distance in the longitudinal direction of the target 2 between the respective center points 210 of the two first detectable portions 21 is indicated as La, and the ratio of the length of the first detectable portions 21 to this distance La is indicated as Ua. The length of the first detection coil 31 in the longitudinal direction of the substrate 3 is (1-Ua)La. The distance between the two first detectable portions 21 aligned in the longitudinal direction of the substrate 3 is the same as the length of the first detection coil 31. In this embodiment, Ua is 0.25, and the length of the first detectable portions 21 in the longitudinal direction of the substrate 3 is one-fourth of the distance La.

The first detection coil 31 has two coil conductors 311, 312 spaced apart in the coil width direction (the vertical direction in FIG. 7) perpendicular to the extension direction of the excitation coil 300. The distance between the two coil conductors 311, 312 in the coil width direction is extremely small at both ends 31a, 31b of the first detection coil 31. The first detection coil 31 also has an intersection 31c where the two coil conductors 311, 312 intersect, and a left maximum portion 31d and a right maximum portion 31e where the distance between the two coil conductors 311, 312 in the coil width direction is extremely large between the intersection 31c and both ends 31a, 31b.

The first detection coil 31 has a symmetrical shape with the left and right parts sandwiched between the intersection 31c. Hereinafter, the area between the two coil conductors 311, 312 to the left of the intersection 31c is referred to as the left window 313, and the area between the two coil conductors 311, 312 to the right of the intersection 31c is referred to as the right window 314.

The distance between the two coil conductors 311, 312 gradually increases from the left end 31a of the first detection coil 31 toward the left maximum portion 31d, and gradually decreases from the left maximum portion 31d toward the intersection 31c. The distance between the two coil conductors 311, 312 gradually increases from the right end 31b of the first detection coil 31 toward the right maximum portion 31e, and gradually decreases from the right maximum portion 31e toward the intersection 31c.

In the following description of the present embodiment, when distinguishing between the two coil conductors 311, 312, the coil conductor 311 that is located above the intersection 31c in the section between the intersection 31c and the left end 31a and below the intersection 31c in the section between the intersection 31c and the right end 31b is referred to as one coil conductor 311, and the coil conductor 312 that is located below the intersection 31c in the section between the intersection 31c and the left end 31a and above the intersection 31c in the section between the intersection 31c and the right end 31b is referred to as the other coil conductor 312.

One coil conductor portion 311 is formed on the first metal layer 301 as shown in Fig. 6(a). The other coil conductor portion 312 is formed on the third metal layer 303 as shown in Fig. 6(c). The one coil conductor portion 311 and the other coil conductor portion 312 are shaped symmetrically in the short direction of the substrate 3 across a symmetry axis _A1 extending in the longitudinal direction of the substrate 3. The one coil conductor portion 311 and the other coil conductor portion 312 are electrically connected by a first via 351 at the right end portion 31b of the first detection coil 31.

The inclination of one coil conductor portion 311 and the other coil conductor portion 312 with respect to the longitudinal direction of the substrate 3 (the direction of movement of the rack shaft 13) between the left end portion 31a of the first detection coil 31 and the left maximum portion 31d is greater than the inclination of one coil conductor portion 311 and the other coil conductor portion 312 with respect to the longitudinal direction of the substrate 3 between the left maximum portion 31d and the intersection portion 31c. Also, the inclination of one coil conductor portion 311 and the other coil conductor portion 312 with respect to the longitudinal direction of the substrate 3 between the right end portion 31b of the first detection coil 31 and the right maximum portion 31e is greater than the inclination of one coil conductor portion 311 and the other coil conductor portion 312 with respect to the longitudinal direction of the substrate 3 between the right maximum portion 31e and the intersection portion 31c.

Due to the difference in inclination between the coil conductors 311, 312, the distance _L1 in the longitudinal direction of the substrate 3 from the left end 31a of the first detector coil 31 to the left maximum portion 31d is shorter than the distance _L2 from the left maximum portion 31d to the intersection 31c, and the distance _L3 from the right end 31b of the first detector coil 31 to the right maximum portion 31e is shorter than the distance _L4 from the right maximum portion 31e to the intersection 31c.

The excitation coil 300 generates a magnetic field by the current supplied from the power supply unit 102. In the target 2, an eddy current is generated by the magnetic field generated by the excitation coil 300. This eddy current acts to weaken the strength of the magnetic field in the substrate 3, causing variation in the distribution of the magnetic field strength in each part of the substrate 3. In other words, the magnetic field strength on the substrate 3 is strong in the part aligned vertically to the substrate with the first detectable part 21 or the second detectable part 22 of the target 2, and the magnetic field strength on the substrate 3 is relatively weak in the part aligned vertically to the substrate with the first detectable part 21 or the second detectable part 22 not formed.

In the first detection coil 31, a voltage is generated according to the position of the first detection target 21 relative to the board 3 due to the difference in magnetic field strength between the portion corresponding to the first detection target 21 (the portion aligned with the first detection target 21 in the board vertical direction) and the portion not corresponding to the first detection target 21 (the portion not aligned with the first detection target 21 in the board vertical direction). In other words, if there is no variation in the magnetic field strength distribution in the board 3, the electromotive force due to the magnetic flux interlinked with the left window portion 313 and the electromotive force due to the magnetic flux interlinked with the right window portion 314 cancel each other out, and the voltage generated in the first detection coil 31 becomes zero. However, in this embodiment, due to the difference in magnetic field strength between the portion corresponding to the first detection target 21 and the portion not corresponding to it, a difference occurs between the electromotive force due to the magnetic flux interlinked with the left window portion 313 and the electromotive force due to the magnetic flux interlinked with the right window portion 314, and this electromotive force difference becomes the output voltage of the first detection coil 31. When the rack shaft 13 moves, the area of the portion where the left window 313, the right window 314, and the multiple first detectable parts 21 are aligned in the vertical direction of the board changes, causing the magnitude of the output voltage of the first detection coil 31 to change periodically.

The shape of the first detection coil 31 is designed so that when the rack shaft 13 moves in one direction, the output voltage of the first detection coil 31 changes sinusoidally from the time when the first detection coil 31 and at least a part of the first detectable portion 21 start to align in the vertical direction of the board to the time when the entire first detectable portion 21 is no longer aligned in the vertical direction of the board with the first detection coil 31. The change in the output voltage of the first detection coil 31 according to the position of the rack shaft 13 will be described in detail later.

The voltage generated in the first detection coil 31 is transmitted to the calculation unit 101 via the first transmission line 36. The first transmission line 36 has a one-side conductor line 361 connected to one coil conductor portion 311 at the left end portion 31a of the first detection coil 31, and an other-side conductor line 362 connected to the other coil conductor portion 312 at the left end portion 31a of the first detection coil 31. The one-side conductor line 361 is formed on the first metal layer 301 together with the one coil conductor portion 311, and the other-side conductor line 362 is formed on the third metal layer 303 together with the other coil conductor portion 312.

Fig. 8 is a graph showing an example of the relationship between the supply voltage _V0 supplied from the power supply unit 102 to the excitation coil 300 and the output voltage _V1 of the first detection coil 31. The horizontal axis of the graph in Fig. 8 is the time axis, and the left and right vertical axes show the supply voltage _V0 and the output voltage _V1 . A high-frequency AC voltage of, for example, about 1 MHz is supplied to the excitation coil 300 as the supply voltage _V0 . In the example shown in Fig. 6, the supply voltage _V0 and the output voltage _V1 are in phase, but the output voltage _V1 switches between in-phase and out-of-phase when the center point 210 of the first detected portion 21 passes through a position corresponding to the intersection 31c.

The second detection coil 32 is offset from the first detection coil 31 in the extension direction of the excitation coil 300 (the longitudinal direction of the substrate 3). The offset is La/4 as shown in FIG. 5. The shape and size of the second detection coil 32 are the same as those of the first detection coil 31. That is, the second detection coil 32 has two coil conductor portions 321, 322 spaced apart in the coil width direction, and the spacing between the two coil conductor portions 321, 322 in the coil width direction is extremely small at both ends 32a, 32b of the second detection coil 32.

The second detection coil 32 also has an intersection 32c where the two coil conductors 321, 322 intersect, and a left maximum portion 32d and a right maximum portion 32e where the distance between the two coil conductors 321, 322 in the coil width direction is maximized between the intersection 32c and both ends 32a, 32b. The area between the two coil conductors 321, 322 to the left of the intersection 32c is the left window portion 323. The area between the two coil conductors 321, 322 to the right of the intersection 32c is the right window portion 324.

Of the two coil conductors 321, 322 of the second detection coil 32, one coil conductor 321 is formed on the second metal layer 302 of the substrate 3, and the other coil conductor 322 is formed on the fourth metal layer 304 of the substrate 3. The one coil conductor 321 and the other coil conductor 322 are electrically connected by a second via 352 at the right end 32b of the second detection coil 32.

The second detection coil 32, like the first detection coil 31, outputs a voltage according to the position of the target 2 relative to the substrate 3. The voltage generated in the second detection coil 32 is transmitted to the calculation unit 101 via the second transmission line 37. The second transmission line 37 has a one-side conductor line 371 connected to one coil conductor portion 321 at the left end 32a, and an other-side conductor line 372 connected to the other coil conductor portion 322 at the left end 32a. The one-side conductor line 371 is formed on the second metal layer 302 together with the one coil conductor portion 321, and the other-side conductor line 372 is formed on the fourth metal layer 304 together with the other coil conductor portion 322.

9 is a graph showing the relationship between a first peak voltage V P1, which is the maximum absolute value of the output voltage of the first detection coil 31 in one period of the supply voltage V 0 supplied to the excitation coil 300, and a second peak voltage V _P2 , which is the maximum absolute value of the output voltage of the second detection coil 32 in one period of the supply voltage V ₀ , when the rack shaft 13 moves in one direction at a constant speed. In this graph, the first peak voltage V _P1 is a positive value when the output voltage of the first detection coil 31 is in phase with the supply voltage, and is a negative value when the output voltage is in phase with the supply voltage. In addition, the second peak voltage V _P2 is a positive value when the output voltage of the second detection coil 32 is in phase with the supply voltage, and is a negative value when the output voltage is in phase with the supply _voltage .

なお、ｔａｎ^－１（アークタンジェント）の演算処理は、例えば不揮発性の記憶素子に記憶した数列（ルックアップテーブル）を参照して行うことにより、演算負荷を軽減することが可能である。 The first peak voltage V _P1 and the second peak voltage V _P2 change in a sinusoidal manner for a period corresponding to the number of first detectable parts 21 formed on the target 2. In this embodiment, five first detectable parts 21 are formed at equal intervals along the longitudinal direction of the target 2, so that the first peak voltage V _P1 and the second peak voltage V _P2 change for five periods. In addition, since the second detection coil 32 is offset from the first detection coil 31 by a length of La/4, the second peak voltage V _P2 is shifted in phase from the first peak voltage V _P1 by 90° (π/2 [rad]). Therefore, the CPU 100 can obtain the position Xa of the rack shaft 13 within the range of the distance La corresponding to one period of the first peak voltage V _P1 by the following formula (1).

It should be noted that the calculation load of tan ⁻¹ (arctangent) can be reduced by performing the calculation process with reference to a sequence (lookup table) stored in a non-volatile storage element, for example.

However, by only calculating this formula (1), it is not possible to determine which of the five first detectable parts 21 is located at a position corresponding to the first detection coil 31 and the second detection coil 32, and it is not possible to detect the absolute position throughout the entire stroke range R of the rack shaft 13. For this reason, the stroke sensor 1 has a second detection coil set 3B consisting of a combination of a third detection coil 33 and a fourth detection coil 34, in addition to a first detection coil set 3A consisting of a combination of the first detection coil 31 and the second detection coil 32. The third detection coil 33 and the fourth detection coil 34 are configured in the same manner as the first detection coil 31 and the second detection coil 32.

As shown in FIG. 5, the third detection coil 33 has two coil conductor portions 331, 332, and the distance between the two coil conductor portions 331, 332 in the coil width direction is extremely small at both ends 33a, 33b of the third detection coil 33. The third detection coil 33 also has an intersection portion 33c where the two coil conductor portions 331, 332 intersect, a left maximum portion 33d, and a right maximum portion 33e. The area between the two coil conductor portions 331, 332 to the left of the intersection portion 33c is the left window portion 333. The area between the two coil conductor portions 331, 332 to the right of the intersection portion 33c is the right window portion 334.

Similarly, the fourth detection coil 34 has two coil conductors 341, 342, and the distance between the two coil conductors 341, 342 in the coil width direction is extremely small at both ends 34a, 34b of the fourth detection coil 34. The fourth detection coil 34 also has an intersection 34c where the two coil conductors 341, 342 intersect, a left maximum portion 34d, and a right maximum portion 34e. The area between the two coil conductors 341, 342 to the left of the intersection 34c is the left window portion 343, and the area between the two coil conductors 341, 342 to the right of the intersection 34c is the right window portion 344.

As shown in FIG. 4(b), if the distance in the longitudinal direction of the target 2 between the respective center points 220 of the two second detectable portions 22 is Lb, the fourth detectable coil 34 is offset from the third detectable coil 33 by an offset amount of Lb/4 in the extension direction of the excitation coil 300. The ratio of the length of the second detectable portion 22 to the distance Lb is Ub, and in this embodiment, ub is 0.25. The length of the third detectable coil 33 and the length of the fourth detectable coil 34 in the longitudinal direction of the substrate 3 is (1-Ub)Lb.

The coil conductor 331 of the third detection coil 33 is formed on the first metal layer 301, the coil conductor 332 of the third detection coil 33 is formed on the third metal layer 303, the coil conductor 341 of the fourth detection coil 34 is formed on the second metal layer 302, and the coil conductor 342 of the fourth detection coil 34 is formed on the fourth metal layer 304. The coil conductors 331 and 332 of the third detection coil 33 are electrically connected by a third via 353 at the right end 33b of the third detection coil 33, and the coil conductors 341 and 342 of the fourth detection coil 34 are electrically connected by a fourth via 354 at the right end 34b of the fourth detection coil 34.

The third detection coil 33 and the fourth detection coil 34 output a voltage according to the position of the target 2 relative to the substrate 3, similar to the first detection coil 31 and the second detection coil 32, due to the difference in magnetic field strength between the portion aligned with the second detection target 22 in the vertical direction of the substrate and the portion not aligned with the second detection target 22. The output voltage of the third detection coil 33 is transmitted to the calculation unit 101 via a third transmission line 38 consisting of a one-side conductor line 381 connected to one coil conductor portion 331 at the left end 33a of the third detection coil 33 and a second-side conductor line 382 connected to the other coil conductor portion 332. The output voltage of the fourth detection coil 34 is transmitted to the calculation unit 101 via a fourth transmission line 39 consisting of a one-side conductor line 391 connected to one coil conductor portion 341 at the left end 34a of the fourth detection coil 34 and a second-side conductor line 392 connected to the other coil conductor portion 342.

The CPU 100 can determine the position Xb of the rack shaft 13 within a range of a distance Lb equivalent to one cycle of the third peak voltage _Vp3 by using the following equation (2), where the maximum absolute value of the output voltage of the third detection coil 33 within one cycle of the supply voltage supplied to the excitation coil ₃₀₀ is a third peak voltage Vp3, and the maximum absolute value of the output voltage of the fourth detection coil 34 within one cycle of the supply voltage _V0 is a fourth peak voltage _Vp4 .

The distance Lb between the center points 220 of the two second detectable parts 22 in the longitudinal direction of the substrate 3 is shorter than the distance La between the center points 210 of the two first detectable parts 21 in the longitudinal direction of the substrate 3. When the number of the first detectable parts 21 formed on the target 2 is n ₁ and the number of the second detectable parts 22 is n ₂ , the ratio of La to Lb (La/Lb) is greater than 1 and smaller than n ₂ /n _1. In this embodiment, since n ₁ = 5 and n ₂ = 6, La/Lb is less than 1.2, and in the illustrated example of FIG. 4 and FIG. 5, La/Lb is 1.143. As an example, La is 0.040 [m], and as an example, Lb is 0.035 [m].

In addition, the length of the third detector coil 33 and the length of the fourth detector coil 34 in the longitudinal direction of the substrate 3 are different from the length of the first detector coil 31 and the length of the second detector coil 32 in the longitudinal direction of the substrate 3, and the length of the third detector coil 33 is shorter than the length of the first detector coil 31, and the length of the fourth detector coil 34 is shorter than the length of the second detector coil 32. The ratio of the length of the first detector coil 31 and the length of the second detector coil 32 to the length of the third detector coil 33 and the length of the fourth detector coil 34 is the same as the ratio of La to Lb.

Figure 10 is a flowchart showing an example of the calculation process performed by the CPU 100 to determine the position of the rack shaft 13. In this flowchart, ωa is the value obtained by dividing 2π by La, and ωb is the value obtained by dividing 2π by Lb. As described above, when La = 0.040 [m], ωa = 157.08 [rad/m], and when Lb = 0.035 [m], ωb = 179.52 [rad/m].

ＣＰＵ１００は、求めたラックシャフト１３の位置Ｘの情報を、ケーブル１０３を介して操舵制御装置１９に出力する。 In the calculation process shown in this flowchart, the CPU 100 obtains Xa by the above formula (1) (step S1), and obtains Xb by the above formula (2) (step S2). Next, the CPU 100 determines whether ωb.Xb-ωa.Xa is equal to or greater than 0 (step S3), and if ωb.Xb-ωa.Xa is equal to or greater than 0, obtains the position of the rack shaft 13 by the following formula (3) (step S4), and if ωb.Xb-ωa.Xa is less than 0, obtains the position X of the rack shaft 13 by the following formula (4) (step S5).

The CPU 100 outputs the obtained information about the position X of the rack shaft 13 to the steering control device 19 via a cable 103.

11 is a graph showing the relationship between the positions Xa, Xb of the rack shaft 13 calculated by the above formulas (1) and (2) and the position X of the rack shaft 13 calculated by the above formula (3) or (4). In this embodiment, as shown in FIG. 11, the ratio of La to Lb is greater than 1 and smaller than _n2 / _n1 , so that Xb changes at intervals shorter than Xa. This makes it possible to detect the absolute position of the rack shaft 13 relative to the housing 14 over the entire stroke range R.

[Comparative Example]
12 is an explanatory diagram showing a configuration example of the detection coil group 4 according to the comparative example together with two first detection target portions 21 of the target 2. This detection coil group 4 is configured by combining a sine-wave-shaped detection coil 41 having a pair of sine-wave-shaped coil conductors 411, 412 and a cosine-wave-shaped detection coil 42 having a pair of cosine-wave-shaped coil conductors 421, 422 and a short circuit line 423. When the entirety of one first detection target portion 21 is aligned with the detection coil group 4 in the substrate vertical direction, the sine-wave-shaped detection coil 41 and the cosine-wave-shaped detection coil 42 output a sine-wave-shaped voltage like the first detection coil 31 according to the above embodiment, but when only a part of the first detection target portion 21 is aligned with the detection coil group 4 in the substrate vertical direction, the change in the output voltage becomes gradual.

Figure 13 is a graph showing a comparison of the calculation results of the position Xa of the rack shaft 13 calculated by the above formula (1) based on the output voltage of the first detection coil 31, and the position Xa' of the rack shaft 13 calculated by an arithmetic expression similar to the above formula (1) based on the output voltage of the detection coil set 4. As shown in this graph, Xa and Xa' match in the range of (Ua · La)/2 to (1-Ua/2) La, but in the range of 0 to (Ua · La)/2 and from (1-Ua/2) La to La, the change in Xa' relative to the position of the rack shaft 13 becomes gradual, resulting in an error. For this reason, a calculation for correction is required, which increases the calculation load on the CPU 100.

[Effects of the embodiment]
According to the present embodiment described above, the output voltages of the first to fourth detection coils 31 to 34 provided on the substrate 3 change in a sinusoidal manner, so that it is possible to provide a stroke sensor 1 that is small and lightweight and capable of accurately determining the position of the rack shaft 13.

[Modification of detection coil]
Next, modified examples 1 to 4 of the detection coil will be described. As in the above embodiment, with the detection coils according to these modified examples 1 to 4, when the rack shaft 13 moves in one direction, the output voltage of the detection coil changes in a sinusoidal shape over the entire period from when at least a part of the detected part that moves with the rack shaft 13 and the detection coil start to align in a direction perpendicular to the moving direction of the rack shaft 13 until the entire detected part is no longer aligned in a direction perpendicular to the moving direction of the rack shaft 13 with the detection coil. This provides the same action and effect as the above embodiment.

<Detection coil variation 1>
Fig. 14 is an explanatory diagram showing a detection coil 61 according to Modification 1 together with a target 2 combined with this detection coil 61. In Fig. 14, the left-right direction in the drawing corresponds to the moving direction of the rack shaft 13 and the target 2. Also, in Fig. 14, similar to Fig. 7, the distance in the longitudinal direction of the target 2 between the center points 210 of the first detectable portions 21 of the target 2 is indicated by La, and the ratio of the length of the first detectable portions 21 to this distance La is indicated by Ua. The length of the detection coil 61 in the moving direction of the rack shaft 13 is (1-Ua)La. In Modification 1, Ua is 0.1.

The detection coil 61 has two coil conductors 611, 612 spaced apart in the coil width direction (the vertical direction in FIG. 14). One of the coil conductors, the 611, is formed of a number of line segments 611a that extend linearly in a direction perpendicular to the direction of movement of the rack shaft 13, and a number of inclined portions 611b that are inclined with respect to the direction of movement of the rack shaft 13 and connect the ends of the line segments 611a.

The other coil conductor portion 612 has a shape symmetrical to the coil conductor portion 611 across the axis of symmetry _A1 , and is formed by a plurality of line segments 612a extending linearly in a direction perpendicular to the movement direction of the rack shaft 13, and a plurality of inclined portions 612b inclined with respect to the movement direction of the rack shaft 13 and connecting the ends of the plurality of line segments 612a.

The two coil conductors 611, 612 are formed on different layers of a single substrate, as in the above embodiment, and one end of the coil conductors 611, 612 in the direction of movement of the rack shaft 13 is connected to each other by a via 613. The other end of the coil conductors 611, 612 in the direction of movement of the rack shaft 13 is connected to the calculation unit 101.

In the first modification, the coil conductor portion 611 is formed by nine line segments 611a and eight inclined portions 611b, and the coil conductor portion 612 is formed by nine line segments 612a and eight inclined portions 612b. The coil conductor portions 611 and 612 intersect at an intersection point 610 on the axis of symmetry _A1 . The two coil conductor portions 611 and 612 are shaped point-symmetric with respect to the intersection point 610.

An interval _I61 between each of the multiple line segments 611a of the coil conductor portion 611 in the movement direction of the rack shaft 13 and an interval _I62 between each of the multiple line segments 612a of the coil conductor portion 612 are intervals corresponding to the length of the first detectable portion 21 in the movement direction of the rack shaft 13, and specifically, are the same as Ua and La, which are the lengths of the first detectable portion 21. Furthermore, a length _L61 between each of the multiple line segments 611a of the coil conductor portion 611 in the direction perpendicular to the movement direction of the rack shaft 13 and a length _L62 between each of the multiple line segments 612a of the coil conductor portion 612 are common to both.

The spacing _I61 , _I62 between each of the multiple line segments 611a, 612a and the spacing _L61 , _L62 between each of the multiple line segments 611a, 612a are adjusted, for example by electromagnetic field simulation, so that when the rack shaft 13 moves in one direction, the output voltage of the detection coil 61 changes sinusoidally throughout the entire period from when at least a portion of a first detectable portion 21 and the detection coil 61 begin to align in a direction perpendicular to the movement direction of the rack shaft 13 to when the entire first detectable portion 21 and the detection coil 61 are no longer aligned in a direction perpendicular to the movement direction of the rack shaft 13.

Figure 15 is a configuration diagram showing an example of a configuration in which the detection coil 61 shown in Figure 14 is used as the first detection coil 61, a second detection coil 62 configured similarly to the first detection coil 61 is combined with the first detection coil 61 to form a first detection coil set 6A, and a third and fourth detection coils 63, 64 whose lengths in the moving direction of the rack shaft 13 are shorter than the first and second detection coils 61, 62 are combined to form a second detection coil set 6B. Also, Figure 15 shows an excitation coil 600 formed to surround the first detection coil set 6A and the second detection coil set 6B, and shows the target 2 facing the first detection coil set 6A and the second detection coil set 6B. The excitation coil 600 is a rectangular shape that is long in the moving direction of the rack shaft 13, and extends in the moving direction of the rack shaft 13.

The first to fourth detection coils 61 to 64 and the excitation coil 600 are formed on a single four-layer substrate having first to fourth metal layers, as in the above embodiment, with the wiring pattern of the first metal layer indicated by a solid line, the wiring pattern of the second metal layer indicated by a dashed line, the wiring pattern of the third metal layer indicated by a dashed line, and the wiring pattern of the fourth metal layer indicated by a dashed double-dot line. The first detection coil 61 and the second detection coil 62 have the same length in the longitudinal direction of the excitation coil 600, and are formed offset in the longitudinal direction of the excitation coil 600. The amount of offset is La/4.

The second detection coil set 6B has a shape in which the first detection coil set 6A has been shortened in the longitudinal direction of the excitation coil 600, and the third and fourth detection coils 63, 64, like the detection coil 61 described with reference to FIG. 14, are formed of multiple line segments that extend linearly in a direction perpendicular to the moving direction of the rack shaft 13 and multiple inclined portions that connect the ends of the multiple line segments, but the length of the multiple inclined portions in the longitudinal direction of the excitation coil 600 is shorter than that of the first and second detection coils 61, 62.

The third detection coil 63 and the fourth detection coil 64 are formed with an offset in the longitudinal direction of the excitation coil 600. As in the above embodiment, if the spacing between the multiple second detectable portions 22 of the target 2 is Lb, the offset between the third detection coil 63 and the fourth detection coil 64 is Lb/4. By combining the first detection coil set 6A and the second detection coil set 6B in this manner, the absolute position of the rack shaft 13 can be detected throughout the entire stroke range R, as described with reference to Figures 9 to 11.

<Detection coil modification 2>
16 is an explanatory diagram showing a detection coil 7 according to Modification 2, together with a target 2 to be combined with the detection coil 7. The detection coil 7 has two coil conductor portions 71, 72 spaced apart in the coil width direction. Of these, one of the coil conductor portions 71 is formed by a plurality of line segments 71a extending linearly in a direction perpendicular to the moving direction of the rack shaft 13, and an inclined portion 71b inclined with respect to the moving direction of the rack shaft 13 and connecting the respective ends of the plurality of line segments 71a.

The other coil conductor portion 72 has a shape symmetrical to the one coil conductor portion 71 across the axis of symmetry _A1 , and is formed by a plurality of line segments 72a extending linearly in a direction perpendicular to the moving direction of the rack shaft 13, and inclined portions 72b connecting the respective ends of the plurality of line segments 72a at an angle with respect to the moving direction of the rack shaft 13. In the second modification, the number of line segments 71a and 72a of the coil conductor portions 71 and 72 is two each, and the number of inclined portions 71b and 72b of the coil conductor portions 71 and 72 is one each.

The two coil conductors 71, 72 are formed on different layers of a single substrate, as in the above embodiment, and one end of the coil conductors 71, 72 in the moving direction of the rack shaft 13 is connected to each other by a via 73. The other end of the coil conductors 71, 72 in the moving direction of the rack shaft 13 is connected to the calculation unit 101. The coil conductors 71, 72 intersect at an intersection 70 on the symmetric axis _A1 . The two coil conductors 71, 72 are each shaped point-symmetric with respect to the intersection 70. The length of the detection coil 7 in the moving direction of the rack shaft 13 is (1-Ua)La, and the interval between each of the multiple line segments 71a, 72a of the coil conductors 71, 72 is Ua·La. In this modification, Ua is 0.5.

The detection coil 7 of the configuration according to this modification 2 can be combined, for example, as described for modification 1 with reference to FIG. 15 to form a first and second detection coil set, thereby making it possible to detect the absolute position of the rack shaft 13 over the entire stroke range R. The same applies to the detection coils according to modifications 3 and 4 described below.

<Detection coil modification 3>
17 is an explanatory diagram showing a detection coil 8 according to Modification 3, together with a target 2 to be combined with this detection coil 8. The detection coil 8 has two coil conductor portions 81, 82 spaced apart in the coil width direction. Of these, one of the coil conductor portions 81 is formed by a plurality of line segments 81a extending linearly in a direction perpendicular to the moving direction of the rack shaft 13, and a plurality of inclined portions 81b inclined with respect to the moving direction of the rack shaft 13 and connecting the respective ends of the plurality of line segments 81a.

The other coil conductor portion 82 has a shape symmetrical to the one coil conductor portion 81 across the axis of symmetry _A1 , and is formed by a plurality of line segments 82a extending linearly in a direction perpendicular to the moving direction of the rack shaft 13, and a plurality of inclined portions 82b connecting the respective ends of the plurality of line segments 82a at an angle with respect to the moving direction of the rack shaft 13. In the third modification, the number of line segments 81a and 82a of the coil conductor portions 81 and 82 is 50 each, and the number of inclined portions 81b and 82b of the coil conductor portions 81 and 82 is 49 each.

The two coil conductors 81, 82 are formed on different layers of a single substrate, and one end of the coil conductors 81, 82 in the moving direction of the rack shaft 13 is connected to each other by a via 83. The other end of the coil conductors 81, 82 in the moving direction of the rack shaft 13 is connected to the calculation unit 101. The coil conductors 81, 82 intersect at an intersection 80 on the symmetric axis _A1 . The two coil conductors 81, 82 each have a shape that is point-symmetric with respect to the intersection 80. The length of the detection coil 8 in the moving direction of the rack shaft 13 is (1-Ua)La, and the interval between each of the multiple line segments 81a, 82a of the coil conductors 81, 82 is Ua·La. In this modification, Ua is 0.02.

<Detection coil modification 4>
18 is an explanatory diagram showing a detection coil 9 according to Modification 4, together with a target 2 to be combined with the detection coil 9. The detection coil 9 has two coil conductor portions 91, 92 spaced apart in the coil width direction. Of these, one of the coil conductor portions 91 is formed by a plurality of line segments 91a extending linearly in a direction perpendicular to the moving direction of the rack shaft 13, and a plurality of inclined portions 91b inclined with respect to the moving direction of the rack shaft 13 and connecting the respective ends of the plurality of line segments 91a.

The other coil conductor portion 92 has a shape symmetrical to the one coil conductor portion 91 across the axis of symmetry _A1 , and is formed by a plurality of line segments 92a extending linearly in a direction perpendicular to the moving direction of the rack shaft 13, and a plurality of inclined portions 92b connecting the respective ends of the plurality of line segments 92a at an angle with respect to the moving direction of the rack shaft 13. In the fourth modification, the number of line segments 91a and 92a of the coil conductor portions 91 and 92 is five each, and the number of inclined portions 91b and 92b of the coil conductor portions 91 and 92 is four each.

The two coil conductor portions 91, 92 are formed on different layers of a single substrate, and one end of the coil conductor portions 91, 92 in the moving direction of the rack shaft 13 is connected to a via 93. The other end of the coil conductor portions 91, 92 in the moving direction of the rack shaft 13 is connected to a calculation unit 101. The coil conductor portions 91, 92 intersect at an intersection 90 on a symmetrical axis _A1 . The two coil conductor portions 91, 92 each have a shape that is point-symmetric with respect to the intersection 90. The length of the detection coil 9 in the moving direction of the rack shaft 13 is (1-Ua)La, and in this modified example, Ua is 0.3.

In this modified example, the distance between the line segments 91a, 92a at both ends of the coil conductors 91, 92 in the moving direction of the rack shaft 13 and the adjacent line segments 91a, 92a is Ua·La, but in the center of the detection coil 9, the distance between each of the multiple line segments 91a, 92a is Ua·La/6. In this way, even if the distances between the multiple line segments 91a, 92a differ in some places, the output voltage of the detection coil 9 changes in a sinusoidal manner.

(Summary of the embodiment and modifications)
Next, the technical ideas grasped from the above-mentioned embodiment and modified examples will be described by using the reference numerals and the like in the embodiment and modified examples. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiment and modified examples.

[1] A position detection device (stroke sensor 1) that detects the position of a moving member (rack shaft 13) that moves back and forth in a predetermined moving direction, comprising: an excitation coil (300, 600) that is arranged extending in the moving direction along the moving member (13); detection coils (31-34, 61-64, 7-9) that output a voltage corresponding to the position of a detected part (21, 22) that moves together with the moving member (13) within a predetermined detection range in the moving direction due to a magnetic field generated by the excitation coil (300, 600); and a calculation unit (101) that calculates the position of the moving member (13) based on the output voltage of the detection coils (31-34, 61-64, 7-9), and the detected part (21, 22) has a predetermined length in the moving direction, and a voltage is generated in the detection coils (31-34, 61-64, 7-9) due to the difference in magnetic field strength between the parts corresponding to the detected parts (21, 22) and the parts not corresponding to the detected parts, and when the moving member (13) moves in one direction, the output voltage of the detection coils (31-34, 61-64, 7-9) changes in a sinusoidal shape over the entire period from when the detection coils (31-34, 61-64, 7-9) and at least a part of the detected parts (21, 22) start to align in a direction perpendicular to the moving direction until the entire detected parts (21, 22) are no longer aligned in a direction perpendicular to the moving direction with the detection coils (31-34, 61-64, 7-9). Position detection device (1).

[2] The detection coil (31 to 34) has two coil conductor parts (311, 312, 321, 322, 331, 332, 341, 342) spaced apart in the coil width direction perpendicular to the extension direction of the excitation coil (300), and the spacing between the two coil conductor parts (311, 312, 321, 322, 331, 332, 341, 342) is equal to the distance between the detection coil (3 and the coil conductor portions (311, 312, 321, 322, 331, 332, 341, 342) in the coil width direction are located at their intersections (31c, 32c, 33c, 34c), and the coil conductor portions (311, 312, 321, 322, 331, 332, 341, 342) in the coil width direction are located at their intersections (31c, 32c, 33c, 34c). and a maximum portion (31d, 31e, 32d, 32e, 33d, 33e, 34d, 34e) where the distance between the two coil conductor portions (311, 312, 321, 322, 331, 332, 341, 342) is maximum, and the two coil conductor portions (311, 312, 321, 322, 331, 332, 341, 342) are located forward from the ends (31a, 31b, 32a, 32b, 33a, 33b, 34a, 34b) of the detection coils (31 to 34). The position detection device (1) described in [1] above, in which the inclination with respect to the direction of movement up to the maximum portion (31d, 31e, 32d, 32e, 33d, 33e, 34d, 34e) is greater than the inclination with respect to the direction of movement between the maximum portion (31d, 31e, 32d, 32e, 33d, 33e, 34d, 34e) and the intersection portion (31c, 32c, 33c, 34c).

[3] The detection coil (61-64, 7-9) has two coil conductor parts (611, 612, 621, 622, 631, 632, 641, 642, 71, 72, 81, 82, 91, 92) spaced apart in the coil width direction perpendicular to the extension direction of the excitation coil (600), and each of the two coil conductor parts (611, 612, 621, 622, 631, 632, 641, 642, 71, 72, 81, 82, 91, 92) is arranged in the moving direction. The position detection device (1) described in [1] above is formed by a plurality of line segments (611a, 612a, 71a, 72a, 81a, 82a, 91a, 92a) that extend linearly in a direction perpendicular to the direction of movement, and inclined portions (611b, 612b, 71b, 72b, 81b, 82b, 91b, 92b) that are inclined with respect to the direction of movement and connect the ends of the plurality of line segments (611a, 612a, 71a, 72a, 81a, 82a, 91a, 92a).

[4] The position detection device (1) described in [3] above, in which the spacing between the multiple line segments (611a, 612a, 71a, 72a, 81a, 82a, 91a, 92a) in the movement direction corresponds to the predetermined length of the detection target portion (21, 22).

[5] A position detection device (1) described in any one of [2] to [4] above, in which the detection coils (31-34, 61-64, 7-9) are arranged offset in the extension direction of the excitation coil (300, 600).

[6] A position detection device (1) according to any one of [2] to [4] above, which has first and second detection coil sets (3A, 3B, 6A, 6B) each consisting of a combination of a plurality of the detection coils (31-34, 61-64, 7-9), the first and second detection coil sets (3A, 3B, 6A, 6B) are arranged in a direction perpendicular to the extension direction of the excitation coil (300, 600), and each of the first and second detection coil sets (3A, 3B, 6A, 6B) has a plurality of the detection coils (31-34, 61-64, 7-9) offset in the extension direction of the excitation coil (300, 600).

[7] The position detection device (1) described in [6] above, in which the length of the multiple detection coils (31, 32, 61, 62) constituting the first detection coil group (3A, 6A) in the extension direction of the excitation coil (300, 600) is different from the length of the multiple detection coils (33, 34, 63, 64) constituting the second detection coil group (3B, 6B) in the extension direction of the excitation coil (300, 600).

[8] A position detection device (1) described in [7] above, in which a plurality of the detection target parts (21) are provided corresponding to the first detection coil group (3A, 6A), and a plurality of the detection target parts (22) are provided corresponding to the second detection coil group (3B, 6B).

[9] The position detection device (1) described in [8] above, in which the detection coils (31-34, 61-64, 7-9) are formed on a single substrate (3), and the excitation coil (300, 600) is formed on the substrate (3) so as to surround the detection coils (31-34, 61-64, 7-9).

[10] The position detection device (1) described in [1] above, which has a conductive member (target 2) attached to the moving member (13), and the detected portion (21, 22) is formed on the conductive member (2).

Although the embodiments and modifications of the present invention have been described above, the above-described embodiments and modifications do not limit the invention according to the claims. It should also be noted that not all of the combinations of features described in the embodiments and modifications are necessarily essential to the means for solving the problems of the invention.

The present invention can be modified as appropriate without departing from the spirit of the invention. For example, in the above embodiment, the first detectable portion 21 and the second detectable portion 22 are formed as recesses in the target 2, but the present invention is not limited to this, and the first detectable portion and the second detectable portion may be conductive protrusions protruding toward the substrate 3. In the above embodiment, the moving member whose position is to be detected by the stroke sensor 1 is the rack shaft 13 of the steering device 10, but the moving member to be detected is not limited to this, and may be a shaft for use in a vehicle or a shaft for use in a vehicle. The shape of the moving member is not limited to a shaft-shaped body, and various shapes such as a flat plate can be used.

1...Stroke sensor (position detection device)
101... Calculation unit 13... Rack shaft (moving member)
2...Target (conductive member)
21...first detected portion 22...second detected portion 3...substrate 3A, 6A...first detection coil set 3B, 6B...second detection coil set 300, 600...excitation coils 31 to 34, 61 to 64...first to fourth detection coils 31a, 31b, 32a, 32b, 33a, 33b, 34a, 34b...ends 31c, 32c, 33c, 34c...intersections 31d, 31e, 32d, 32e, 33d, 33e, 34 d, 34e...maximum portions 311, 312, 321, 322, 331, 332, 341, 342, 611, 612, 621, 622, 631, 632, 641, 642, 71, 72, 81, 82, 91, 92...coil conductor portions 611a, 612a, 71a, 72a, 81a, 82a, 91a, 92a...line segment portions 611b, 612b, 71b, 72b, 81b, 82b, 91b, 92b...inclined portions

Claims (10)

A position detection device for detecting a position of a moving member that moves forward and backward in a predetermined moving direction,
an excitation coil disposed along the moving member and extending in the moving direction;
a detection coil that outputs a voltage corresponding to a position of a detected part that moves together with the moving member within a predetermined detection range in the moving direction by a magnetic field generated by the excitation coil;
a calculation unit that calculates a position of the movable member based on an output voltage of the detection coil;
the detected part has a predetermined length in the moving direction, and a voltage is generated in the detection coil due to a difference in magnetic field strength between a portion corresponding to the detected part and a portion not corresponding to the detected part;
When the movable member moves in one direction, the output voltage of the detection coil changes in a sinusoidal shape from the time when the detection coil and at least a part of the detected part start to align in a direction perpendicular to the moving direction until the entire detected part is no longer aligned with the detection coil in the direction perpendicular to the moving direction.
Position detection device. the detection coil has two coil conductor portions spaced apart in a coil width direction perpendicular to the extension direction of the excitation coil, the distance between the two coil conductor portions being minimal at both ends of the detection coil, and has intersection portions where the two coil conductor portions intersect, and a maximum portion where the distance between the two coil conductor portions in the coil width direction is maximum,
an inclination of the two coil conductor portions with respect to the direction of movement between the ends of the detection coil and the local maximum portion is greater than an inclination of the two coil conductor portions with respect to the direction of movement between the local maximum portion and the intersection portion;
The position detection device according to claim 1 . the detection coil has two coil conductor portions spaced apart from each other in a coil width direction perpendicular to an extension direction of the excitation coil,
Each of the two coil conductors is formed of a plurality of line segments extending linearly in a direction perpendicular to the moving direction, and an inclined portion inclined with respect to the moving direction and connecting ends of the plurality of line segments.
The position detection device according to claim 1 . an interval between the plurality of line segments in the moving direction corresponds to the predetermined length of the detection target portion;
The position detection device according to claim 3 . A plurality of the detection coils are arranged with an offset in the extension direction of the excitation coil.
5. A position detection device according to claim 2. a first detection coil set and a second detection coil set each including a plurality of the detection coils;
the first and second detection coil sets are arranged in a direction perpendicular to the extension direction of the excitation coil,
Each of the first and second detection coil sets has a plurality of detection coils arranged to be offset from one another in an extension direction of the excitation coil.
5. A position detection device according to claim 2. the lengths of the plurality of detection coils constituting the first detection coil group in the extension direction of the excitation coil are different from the lengths of the plurality of detection coils constituting the second detection coil group in the extension direction of the excitation coil;
The position detection device according to claim 6. a plurality of the detection targets are provided corresponding to the first detection coil set;
A plurality of the detection target portions are provided corresponding to the second detection coil group.
The position detection device according to claim 7. A plurality of the detection coils are formed on one substrate,
The excitation coil is formed on the substrate so as to surround the plurality of detection coils.
The position detection device according to claim 8. A conductive member is attached to the moving member,
The conductive member is provided with the detection portion.
The position detection device according to claim 1 .

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