JP2024045018A - Position detection device and vehicle steering device - Google Patents

Abstract

The present invention provides a position detection device that can be miniaturized and a vehicle steering device equipped with the position detection device.
A stroke sensor 2 detects the position of a rack shaft 12 in which a conductive part 121 and a recessed part 120 are arranged side by side in a moving direction. The stroke sensor 2 includes an excitation coil 31 and detection coils 32 and 33 that are arranged to extend in the direction of movement of the rack shaft 12, and a voltage is induced in the detection coils 32 and 33 by the magnetic field generated by the excitation coil 31. . The magnitude of the voltage induced in the detection coils 32 and 33 changes depending on the position of the rack shaft 12 in the moving direction with respect to the detection coils 32 and 33. The vehicle steering device 1 includes a rack shaft 12 , a housing 13 made of conductive metal that accommodates the rack shaft 12 , and a stroke sensor 2 that detects the position of the rack shaft 12 with respect to the housing 13 .
[Selection diagram] Figure 4

Description

The present invention relates to a position detection device that detects the position of a moving member, and a vehicle steering device equipped with the position detection device.

2. Description of the Related Art Conventionally, a position detection device for detecting the position of a moving member has been used, for example, in a moving part of an automobile. The present applicant has proposed a stroke sensor described in Patent Document 1 as such a position detection device.

The stroke sensor described in Patent Document 1 has a predetermined interval between a magnetic field detection section such as a Hall IC, two parallel yokes that sandwich the magnetic field detection section in the stroke direction of a stroke body, and two parallel yokes that sandwich the magnetic field detection section in the stroke direction of a stroke body. A magnetic path forming yoke that is open and extends in the stroke direction of the stroke body, a magnet disposed between the two parallel yokes and one end of each of the magnetic path forming yokes, and the two parallel yokes and the magnetic path forming yoke. The parallel magnetic field forming yoke is disposed movably between the yokes and faces the two parallel yokes, and the protruding yoke is integrally provided on the surface of the parallel magnetic field forming yoke on the magnetic path forming yoke side. . In this stroke sensor, since the intensity of the magnetic field detected by the magnetic field detection section changes depending on the position of the parallel magnetic field forming yoke, the position of the parallel magnetic field forming yoke can be detected based on the intensity of this magnetic field.

JP 2014-98655 A

In the stroke sensor described in Patent Document 1, it is necessary to arrange two parallel yokes and a magnetic path forming yoke so that the parallel magnetic field forming yoke and the protruding yoke are sandwiched between them over the entire movement range of the parallel magnetic field forming yoke, which results in a large installation size for the stroke sensor. Therefore, the present invention aims to provide a position detection device that can be miniaturized, and a vehicle steering device equipped with the position detection device.

In order to solve the above problems, the present invention provides position detection for detecting the position of a moving member in which a conductive part and a non-conductive part having a higher electrical resistance than the conductive part are arranged side by side in a predetermined moving direction. The device includes an excitation coil and a detection coil arranged to extend in the moving direction of the moving member, and a voltage is induced in the detection coil by a magnetic field generated by the excitation coil, and a voltage is induced in the detection coil. The present invention provides a position detection device in which the magnitude of the voltage applied to the detection coil changes depending on the position of the moving member in the moving direction with respect to the detection coil.

In order to solve the above problems, the present invention provides a vehicle steering device that includes a shaft made of conductive metal that moves axially back and forth along the vehicle width direction, a housing made of conductive metal that houses the shaft, and a position detection device that detects the position of the shaft relative to the housing, and in which the wheels are steered by the axial movement of the shaft, the shaft is provided with a recess formed by recessing in the radial direction, the position detection device includes an excitation coil and a detection coil arranged to extend in the vehicle width direction of the shaft, a voltage is induced in the detection coil by the magnetic field generated by the excitation coil, and the magnitude of the voltage induced in the detection coil changes depending on the position of the shaft relative to the housing.

According to the present invention, it is possible to miniaturize the position detection device. Furthermore, by miniaturizing the position detection device, the vehicle steering device can be easily mounted on the vehicle.

1(a) is a schematic diagram showing a partial configuration of a vehicle equipped with a vehicle steering device according to an embodiment of the present invention. FIG. (b) is a sectional view taken along line AA in (a). It is a perspective view showing a rack shaft, a housing, a lid member, and a board. 1A is an overall perspective view of a wiring pattern formed on first to fourth metal layers of a substrate, as seen from the front side, and FIG. (a) to (d) are plan views showing the first to fourth metal layers, respectively, viewed from the front side. 11 is a graph showing an example of a relationship between a supply voltage supplied from a power supply unit to an excitation coil, and an induced voltage induced in a sine-wave-shaped detection coil and an induced voltage induced in a cosine-wave-shaped detection coil. (a) is an explanatory diagram schematically showing the relationship between the peak voltage, which is the peak value of the induced voltage induced in the sine wave shape detection coil, and the position of the recess. (b) is an explanatory diagram schematically showing the relationship between the peak voltage, which is the peak value of the induced voltage induced in the cosine wave shape detection coil, and the position of the recessed portion. (a) is a graph in which the horizontal axis represents the amount of movement of the rack shaft from the reference position, and the vertical axis represents the position of the rack shaft detected by the stroke sensor. (b) is a graph in which the horizontal axis represents the amount of movement of the rack shaft from the reference position, and the vertical axis represents the ratio of detection error in the amount of movement of the rack shaft. (a) is a cross-sectional view showing a configuration example in which the position of a rack shaft according to a comparative example to which a detection target, which is a conductive metal member, is attached relative to a housing is detected by a stroke sensor according to an embodiment. (b) is a perspective view showing a rack shaft, a detection target, and a housing according to a comparative example. 6 is a graph showing a detection error of the movement amount of a rack shaft according to a comparative example.

[Embodiment]
FIG. 1(a) is a schematic diagram showing a partial configuration of a vehicle equipped with a vehicle steering device 1 according to an embodiment of the present invention. FIG. 1(b) is a cross-sectional view taken along the line AA in FIG. 1(a).

This vehicle steering device 1 is a steer-by-wire type steering device, and includes a stroke sensor 2 as a position detection device. FIG. 1A shows the vehicle steering device 1 viewed from the rear side in the longitudinal direction of the vehicle, with the right side in the drawing corresponding to the right side in the vehicle width direction, and the left side in the drawing corresponding to the left side in the vehicle width direction. Note that in the explanation with reference to the drawings below, "right" or "left" may be used, but this expression is used for convenience of explanation and limits the direction of arrangement of the stroke sensor 2 in actual use. It's not a thing.

As shown in FIG. 1(a), the vehicle steering device 1 includes a tie rod 11 connected to the rolling wheels 10 (left and right front wheels), a rack shaft 12 connected to the tie rod 11, a housing 13 that houses the rack shaft 12, a cover member 14 (see FIG. 1(b)) that closes the opening of the housing 13, a worm reduction mechanism 15 having a pinion gear 151 meshed with the rack teeth portion 122 of the rack shaft 12, an electric motor 16 that applies a moving force in the vehicle width direction to the rack shaft 12 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 12 is a moving member whose position relative to the housing 13 is detected by the stroke sensor 2. The direction of movement of the rack shaft 12 is an axial direction parallel to the central axis C1 of the rack shaft 12. The rolling wheels 10 are steered by the rack shaft 12 moving in the axial direction.

In FIG. 1(a), the housing 13 is shown by a virtual line, and the inside thereof is shown by a solid line. The rack shaft 12 is made of a steel material such as carbon steel, and is supported by a pair of rack bushes 131 attached to both ends of the housing 13. 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. Worm gear 153 is fixed to motor shaft 161 of electric motor 16.

The electric motor 16 generates torque using a motor current supplied from the steering control device 19 and rotates a worm wheel 152 and a pinion gear 151 via a worm gear 153 . When the pinion gear 151 rotates, the rack shaft 12 moves linearly forward and backward along the vehicle width direction. The rack shaft 12 is movable 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(a), the double arrow indicates the stroke range R, which corresponds to the maximum travel distance of the rack shaft 12 when the steering wheel 17 is steered from one maximum steering angle to the other maximum steering angle. The stroke sensor 2 is capable of detecting the absolute position of the rack shaft 12 relative to the housing 13 throughout this stroke range R.

(Configuration of stroke sensor 2)
The stroke sensor 2 includes a substrate 3 disposed facing the rack shaft 12, a power supply section 4, and a calculation section 5. The stroke sensor 2 detects the position of the rack shaft 12 in the axial direction (movement direction) with respect to the housing 13 and outputs information on the detected position to the steering control device 19. The steering control device 19 controls the electric motor 16 so that the position of the rack shaft 12 detected by the stroke sensor 2 becomes a position corresponding to the steering angle of the steering wheel 17 detected by the steering angle sensor 18.

FIG. 2 is a perspective view showing the rack shaft 12, the housing 13, the lid member 14, and the substrate 3. In addition, in FIG. 2, the housing 13, the lid member 14, and the substrate 3 are shown spaced apart in the vertical direction of the drawing.

The rack shaft 12 and the housing 13 are made of conductive metal. The rack shaft 12 is made of carbon steel for mechanical structures, such as S45C, for example, and has a circular cross-section perpendicular to the axial direction in the range facing the substrate 3, except for a recessed portion 120, which will be described later. The diameter D of the rack shaft 12 is, for example, 25 mm. The housing 13 is made of, for example, die-cast aluminum alloy and has a U-shaped cross section, and is open upward in the vertical direction. The opening 130 of the housing 13 is closed by the lid member 14.

A gap of, for example, 1 mm or more is formed between the outer peripheral surface 12a of the rack shaft 12 and the inner surface 13a of the housing 13. The cover member 14 is a non-conductive member formed in a flat plate shape. A suitable material for the cover member 14 is a resin such as engineering plastic.

The rack shaft 12 is provided with a recess 120 that is recessed in the radial direction of the rack shaft 12 at a portion facing the substrate 3. The recess 120 is formed in a part of the outer peripheral surface 12a of the rack shaft 12 in the circumferential direction. In this embodiment, the recess 120 is a space, but the recess 120 may be filled with a non-conductive material such as resin.

The width of the recess 120 in the axial direction of the rack shaft 12 is shorter than the length of the substrate 3 in the longitudinal direction. A portion of the rack shaft 12 where the recess 120 is not provided is a conductive portion 121 having electrical conductivity. That is, the rack shaft 12 is provided with a conductive part 121 and a non-conductive part having a higher electrical resistance than the conductive part 121, arranged side by side in the axial direction. is realized by. That is, in the present embodiment, the recess 120 faces the substrate 3, and the portion of the rack shaft 12 facing the substrate 3 has a conductive portion 121 and a non-conductive portion along the axial direction (movement direction). The recessed portion 120 and the conductive portion 121 are arranged in this order.

The recess 120 is formed by, for example, cutting out a portion of the round bar that is the material of the rack shaft 12. In this embodiment, the bottom surface 120a of the recess 120 is a flat surface parallel to the substrate 3, and both end surfaces 120b, 120b of the recess 120 face each other in the axial direction with the bottom surface 120a in between. The depth Dp of the recess 120 in the radial direction of the rack shaft 12 is, for example, 5 mm. The rotation of the rack shaft 12 relative to the housing 13 about the central axis C1 is restricted so that the bottom surface 120a always faces the substrate 3 in parallel.

The substrate 3 is attached to the cover member 14, and its front surface 3a faces a part of the axial direction of the rack shaft 12, including the recess 120, via an air gap G. The minimum width W1 of the air gap G in the direction perpendicular to the substrate 3 (the shortest distance between the front surface 3a of the substrate 3 and the outer peripheral surface 12a of the rack shaft 12) is, for example, 1 mm or less. The back surface 3b of the substrate 3 is fixed to the inner surface 14a of the cover member 14 on the rack shaft 12 side by adhesive 20.

The substrate 3 is a four-layer substrate in which a flat substrate 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 substrate 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 direction of movement of the rack shaft 12. The substrate 3 is not limited to a rigid substrate, and may be a flexible substrate.

FIG. 3(a) is an overall view of the wiring patterns formed on the first to fourth metal layers 301 to 304 of the substrate 3 seen through from the surface 3a side. FIG. 3(b) is a partially enlarged view of FIG. 3(a). FIGS. 4(a) to 4(d) are plan views showing the first to fourth metal layers 301 to 304, respectively, viewed from the surface 3a side. Note that the wiring patterns shown in FIGS. 3(a) and 3(b) and FIGS. 4(a) to 4(d) are merely examples, and various wiring patterns may be used as long as the substrate 3 is formed so as to obtain the effects of the present invention. It is possible to adopt various types of wiring patterns.

3(a) and (b) and 4(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 by a dashed line, the wiring pattern of the third metal layer 303 by a dashed line, and the wiring pattern of the fourth metal layer 304 by a dashed line. Also, in FIG. 3(a), the central axis C2 that bisects the substrate 3 in the short direction and extends in the longitudinal direction is shown, and the position of the recess 120 when the rack shaft 12 is located at one end and the other end of the range in which the stroke sensor 2 can detect the absolute position of the rack shaft 12 is shown by a dotted line. As shown in FIG. 1(b), the substrate 3 and the recess 120 overlap in the diameter direction of the rack shaft 12, but in FIG. 3(a), the position of the recess 120 is shown shifted in the short direction relative to the substrate 3.

A connector portion 340 having first to sixth through holes 341 to 346, through which the connector pins of the connector 6 shown by two-dot chain lines in FIG. 3(b) are inserted, is provided at one end in the longitudinal direction of the board 3. ing. The first to sixth through holes 341 to 346 are arranged in a straight line along the width direction of the substrate 3. A connector 71 (see FIG. 1A) of a cable 7 for connection with the power supply section 4 and the calculation section 5 is connected to the connector 6. Furthermore, first to third vias 351 to 353 are formed in the substrate 3 for interlayer connection of wiring patterns.

The first metal layer 301 is formed with a first curved portion 301a, a first connector connection portion 301b that connects one end of the first curved portion 301a to the second through hole 342, and an end connection portion 301c that connects the respective ends of the second curved portion 302a and the fourth curved portion 304a described later. The second metal layer 302 is formed with a second curved portion 302a and a second connector connection portion 302b that connects one end of the second curved portion 302a to the fourth through hole 344. The third metal layer 303 is formed with a third curved portion 303a and a third connector connection portion 303b that connects one end of the third curved portion 303a to the third through hole 343. The fourth metal layer 304 is formed with a fourth curved portion 304a and a fourth connector connection portion 304b that connects one end of the fourth curved portion 304a to the fifth through hole 345.

The first curved portion 301a and the third curved portion 303a are connected at their other ends by a first via 351. The end connecting portion 301c has one end connected to the other end of the second curved portion 302a by the second via 352, and the other end connected to the other end of the fourth curved portion 304a and the third via 352. via 353.

The first to fourth curved portions 301a, 302a, 303a, and 304a are conductor wires curved in a sinusoidal manner. The first curved portion 301a and the third curved portion 303a, and the second curved portion 302a and the fourth curved portion 304a have a symmetrical shape with respect to the central axis C2 of the substrate 3 as an axis of symmetry. It is.

The substrate 3 includes an excitation coil 31 that generates magnetic flux in the conductive portion 121 of the rack shaft 12, and two detection coils 32 and 33 with which the magnetic flux generated in the conductive portion 121 interlinks. The excitation coil 31 and the two detection coils 32 and 33 are arranged to extend in the axial direction of the rack shaft 12. One of the two detection coils 32 and 33 is formed by a first curved portion 301a and a third curved portion 303a. The other detection coil 33 is formed by a second curved portion 302a, a fourth curved portion 304a, and an end connecting portion 301c. In other words, each of the two detection coils 32 and 33 is a combination of two sinusoidal conductor wires whose shape is symmetrical with respect to the central axis C2 when viewed from a direction perpendicular to the axial direction of the rack shaft 12. It has a similar shape.

The excitation coil 31 is rectangular having a pair of long sides 311, 312 extending in the axial direction of the rack shaft 12 and a pair of short sides 313, 314 between the pair of long sides 311, 312, and is formed to surround the detection coils 32, 33. In this embodiment, the long sides 311, 312 and the short sides 313, 314 are formed as wiring patterns on the first metal layer 301. Of the pair of short sides 313, 314, the short side 313 on the connector part 340 side is made up of two straight parts 313a, 313b that sandwich the first to fourth connector connection parts 301b, 302b, 303b, 304b as shown in FIG. 3(b), and the ends of the two straight parts 313a, 313b are connected to the first through hole 341 and the sixth through hole 346 by the connector connection parts 301d, 301e formed on the first metal layer 301.

The excitation coil 31 is not limited to being formed on the first metal layer 301, but may be formed on any of the second to fourth metal layers 302 to 304, or may be formed across multiple layers. The excitation coil may also be formed separately from the substrate 3.

The excitation coil 31 is supplied with a sinusoidal alternating current from the power supply section 4 . Eddy current is generated in the conductive portion 121 of the rack shaft 12 due to magnetic flux generated by the alternating current supplied to the excitation coil 31. This eddy current lowers the density of the magnetic flux linking the two detection coils 32 and 33, and the magnetic flux density in the portion of the substrate 3 facing the conductive portion 121 is lower than that in the portion facing the recessed portion 120, which is a non-conductive portion. . The conductive portion 121 and the recess 120 are arranged facing the substrate 3 in the order of the conductive portion 121, the recess 120, and the conductive portion 121 along the axial direction (movement direction) of the rack shaft 12. Therefore, the magnetic flux density in the portion of the substrate 3 facing the recess 120 is greater than the magnetic flux density in the portion facing the conductive portion 121. Therefore, an induced voltage is generated in the two detection coils 32 and 33 due to the interlinkage of the magnetic flux of the recess 120. The peak value of the voltage induced in the detection coils 32 and 33 changes depending on the position of the recess 120. Note that the peak value of the voltage herein refers to the maximum value of the absolute value of the voltage within a period of one cycle of the alternating current supplied to the excitation coil 31.

The phases of the voltages induced in the detection coils 32, 33 while the rack shaft 12 moves from one axial end to the other axial end are different from each other. In this embodiment, the phases of the voltages induced in the detection coils 32, 33 are different by 90°. Hereinafter, of the two detection coils 32, 33, one detection coil 32 is referred to as the sine wave-shaped detection coil 32, and the other detection coil 33 is referred to as the cosine wave-shaped detection coil 33.

The peak value of the voltage induced in the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33 by the magnetic flux linkage of the conductive portion 121 of the rack shaft 12 changes within a range of one period or less while the rack shaft 12 moves from one axial end to the other axial end. This allows the stroke sensor 2 to detect the absolute position of the rack shaft 12 throughout the entire stroke range R through which the rack shaft 12 can move in the axial direction.

As shown in FIG. 3A, between each of the pair of short sides 313 and 314 of the excitation coil 31 and the sine wave shape detection coil 32 and the cosine wave shape detection coil 33, a pair of short side parts 313 and 314 are provided. , 314 are provided. First and second buffer regions E1 and E2 are provided to suppress the voltage induced in the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 by the magnetic flux generated by the current flowing through the sine wave shape detection coil 32 and the cosine wave shape detection coil 33. In the example shown in FIG. 3(a), the length L1 of the first buffer area E1 and the length L2 of the second buffer area E2 in the longitudinal direction of the substrate 3 are the same, but L1 and L2 are different. It's okay.

FIG. 5 shows the relationship between the supply voltage V0 supplied from the power supply unit 4 to the excitation coil 31, the induced voltage V1 induced in the sine wave shape detection coil 32, and the induced voltage V2 induced in the cosine wave shape detection coil 33. It is a graph showing an example. The horizontal axis of the graph in FIG. 5 is the time axis, and the left and right vertical axes indicate the supply voltage V0 and the induced voltages V1 and V2. The excitation coil 31 is supplied with a high frequency alternating current voltage of, for example, about 1 MHz as a supply voltage V0. The induced voltages V1 and V2 are outputted to the calculation unit 5 via the cable 7 as output voltages of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33.

5, the supply voltage V0 and the induced voltages V1 and V2 are in phase, but the induced voltage V1 induced in the sine wave-shaped detection coil 32 switches between in-phase and out-of-phase when the recess 120 passes through a position corresponding to the intersection of the first curved portion 301a of the first metal layer 301 and the third curved portion 303a of the third metal layer 303 as viewed from the substrate vertical direction perpendicular to the front surface 3a and back surface 3b of the substrate 3. Also, the induced voltage V2 induced in the cosine wave-shaped detection coil 33 switches between in-phase and out-of-phase when the recess 120 passes through a position corresponding to the intersection of the second curved portion 302a of the second metal layer 302 and the fourth curved portion 304a of the fourth metal layer 304 as viewed from the substrate vertical direction.

FIG. 6A is an explanatory diagram schematically showing the relationship between the peak voltage VS, which is the peak value of the induced voltage V1 induced in the sine wave shape detection coil 32, and the position of the recess 120. FIG. 6B is an explanatory diagram schematically showing the relationship between the peak voltage VC, which is the peak value of the induced voltage V2 induced in the cosine wave shape detection coil 33, and the position of the recess 120.

In the graphs of peak voltages VS and VC shown in FIGS. 6A and 6B, the horizontal axis indicates the position of the center of the recess 120 in the left-right direction. P1 on the horizontal axis indicates the position of the center point 120c of the recess 120 when the left end of the recess 120 and the left ends of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 coincide. P2 on the horizontal axis indicates the position of the center point 120c of the recess 120 when the right end of the recess 120 and the right ends of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 coincide. In FIGS. 6(a) and 6(b), the recess 120 when the center point 120c is at the position P1 is shown by a chain line, and the recess 120 when the center point 120c is at the position P2 is shown by a chain double-dot line. There is. Here, the center point 120c of the recess 120 is the center position of the bottom surface 120a, as shown in FIG.

In the sine wave shape detection coil 32 and the cosine wave shape detection coil 33, the strength of the magnetic field at the portion facing the conductive portion 121 is weaker than the strength of the magnetic field at the portion facing the recess 120. Therefore, the output voltage of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 changes depending on the position of the rack shaft 12. In the graph shown in FIG. 6(a), the peak voltage VS is a positive value when the induced voltage V1 induced in the sine wave shape detection coil 32 is in phase with the supply voltage V0 supplied to the exciting coil 31, and When it is in phase, it is taken as a negative value. In the graph shown in FIG. 6(b), the peak voltage VC is a positive value when the induced voltage V2 induced in the cosine wave shape detection coil 33 is in phase with the supply voltage V0 supplied to the exciting coil 31. , when the phase is reversed, the value is negative.

When the rack shaft 12 moves at a constant speed in one direction from one moving end to the other moving end, the peak voltage VS changes sinusoidally, as shown in FIGS. 6(a) and (b). , the peak voltage VC changes in the form of a cosine wave. Therefore, the calculation unit 5 can calculate the position of the rack shaft 12 based on the output voltages of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33.

As shown in FIG. 3A , when the position of the left end portion of the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33 in the longitudinal direction of the substrate 3 is defined as a reference position O, the length of the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33 in the longitudinal direction of the substrate 3 is defined as L, the position X of the rack shaft 12 when the center point 120c of the recess 120 is aligned with the reference position O in the substrate vertical direction is defined as 0 (zero), and the direction from the reference position O toward the right end portions of the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33 is defined as the positive side of the position X of the rack shaft 12, the position X of the rack shaft 12 can be calculated by the following formula (1).

The calculation unit 5 outputs the position calculated by equation (1) based on the output voltages of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 to the steering control device 19 as the position of the rack shaft 12. When the ratio of the length of the recess 120 in the axial direction of the rack shaft 12 to the length L of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 is u, the calculation unit 5 can calculate the absolute position of the rack shaft 12 within the length range of (1-u)L. Note that u is a value smaller than 0.5. The smaller the value of u, the longer the absolute position of the rack shaft 12 can be detected over, but if the value of u is too small, the induced voltages V1 and V2 become smaller and the error is likely to become large. For this reason, it is desirable for the value of u to be, for example, greater than or equal to 0.01 and less than 0.5.

Figure 7(a) is a graph showing the amount of movement of the rack shaft 12 from the reference position on the horizontal axis and the position of the rack shaft 12 detected by the stroke sensor 2 on the vertical axis. The values on the vertical axis are the calculated values of the above formula (1) based on the induced voltages V1 and V2 obtained using an electromagnetic field simulation. Figure 7(b) is a graph showing the amount of movement of the rack shaft 12 from the reference position on the axis and the percentage of detection error in the amount of movement of the rack shaft 12 on the vertical axis.

As shown in the graph of FIG. 7(a), there is a roughly linear relationship between the actual position of the rack shaft 12 and the position of the rack shaft 12 determined by the stroke sensor 2, and as shown in FIG. 7(b), the detection error is suppressed to 5% or less. Note that this error is not something that occurs accidentally due to vibrations, for example, but rather occurs steadily as a detection characteristic, and therefore can be corrected by performing a correction calculation.

(Comparative example)
FIG. 8(a) is a cross-sectional view showing a configuration example in which the position of the rack shaft 12A to which the detection target 123, which is a conductive metal member, is attached relative to the housing 13A is detected by the stroke sensor 2 according to the above embodiment. It is a diagram. FIG. 8(b) is a perspective view showing the rack shaft 12A, the detection target 123, and the housing 13A.

The rack shaft 12A is made of carbon steel for mechanical construction with a circular cross section perpendicular to the axial direction, like the rack shaft 12 in the above embodiment, but does not have a recess 120. The detection target 123 is made of a metal such as steel having the same electrical conductivity as the rack shaft 12A, or a metal with good electrical conductivity such as a copper alloy or an aluminum alloy having higher electrical conductivity than the rack shaft 12A, and is attached to the rack shaft 12A so as to protrude from the outer peripheral surface 12Aa of the rack shaft 12A toward the substrate 3.

The protrusion height H of the detection target 123 from the outer peripheral surface 12Aa of the rack shaft 12A in the direction perpendicular to the substrate 3 is 5 mm, which is the same as the depth Dp of the recess 120 of the rack shaft 12 according to the above embodiment. . The surface 123a of the detection target 123 facing the substrate 3 is parallel to the surface 3a of the substrate 3, and the width W2 of the air gap G between the surface 3a of the substrate 3 and the surface 123a of the detection target 123 is as described above. The width W1 of the air gap G in the embodiment is 1 mm or less.

Like the housing 13 in the above embodiment, the housing 13A is made of an aluminum alloy with a U-shaped cross section and opens vertically upward. However, the external dimensions of the housing 13A in the direction perpendicular to the substrate 3 are larger than those of the housing 13 in the above embodiment by the amount of the protruding height H of the detection target 123.

In this comparative example, the strength of the magnetic field at a portion of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 that faces the detection target 123 is weaker than the strength of the magnetic field at a portion that does not face the detection target 123. Due to this difference in magnetic field strength, the output voltages of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 change depending on the position of the rack shaft 12A.

FIG. 9 is a graph showing the detection error of the movement amount of the rack shaft 12A according to the comparative example. As shown in this graph, when the amount of movement of the rack shaft 12A from the reference position is detected based on the position of the detection target 123, the detection error is larger than in the above embodiment.

The cause of this increase in detection error is thought to be that the magnetic field generated by the excitation coil 31 also acts on the housing 13A on the side of the detection target 123. In other words, in the above embodiment, the distance between the rack shaft 12 made of conductive metal and the substrate 3 is close, so the housing 13A is less susceptible to the magnetic field acting on it, but in the comparative example, the length of the detection target 123 in the axial direction of the rack shaft 12 is relatively short compared to the substrate 3, so it is thought to be more susceptible to the magnetic field acting on the housing 13A than in the above embodiment.

(Effects of embodiment)
According to the embodiment described above, the position of the rack shaft 12 with respect to the housing 13 can be detected by arranging the substrate 3 to face the rack shaft 12 in which the recess 120 is formed, so that the installation size of the stroke sensor 2 can be adjusted. Can be made smaller. More specifically, since the concave portion 120 causes a change in the output voltage of the sine wave shape detection coil 32 and the cosine wave shape detection coil 33 depending on the position of the rack shaft 12, for example, as in the above comparative example, the detection target 123 The size of the housing 13A is not increased by attaching the housing to the rack shaft 12A. Further, by reducing the installation size of the stroke sensor 2, it is possible to reduce the size and weight of the vehicle steering device 1.

(Summary of embodiments)
Next, technical ideas understood from the embodiments described above will be described using reference numerals and the like in the embodiments. However, each reference numeral in the following description does not limit the constituent elements in the scope of the claims to those specifically shown in the embodiments.

[1] Determine the position of the moving member (rack shaft 12) in which a conductive part (121) and a non-conductive part (recess 120) having a higher electrical resistance than the conductive part (121) are arranged side by side in a predetermined moving direction. A position detection device (stroke sensor 2) for detecting the position, comprising an excitation coil (31) and a detection coil (32, 33) extending in the movement direction of the moving member (12), A voltage is induced in the detection coil (32, 33) by the magnetic field generated by the coil (31), and the magnitude of the voltage induced in the detection coil (32, 33) is the same as that for the detection coil (32, 33). A position detection device (2) that changes depending on the position of the moving member (12) in the moving direction.

[2] A position detection device (2) as described in [1] above, which includes a plurality of the detection coils (32, 33), and in which the phases of the voltages induced in each of the detection coils (32, 33) differ from each other when the moving member (12) moves.

[3] The magnitude of the voltage induced in each of the plurality of detection coils (32, 33) is 1 while the moving member (12) moves from one moving end to the other moving end in the axial direction. The position detection device (2) according to the above [2], which changes in a range equal to or less than a period.

[4] The position detection device (2) described in [2] or [3] above, in which each of the multiple detection coils (32, 33) has a shape that is a combination of two sinusoidal conductor lines (first to fourth curved portions 301a, 302a, 303a, 304a) whose shape when viewed from a direction perpendicular to the moving direction is symmetrical with respect to a symmetry axis (central axis C2) parallel to the moving direction.

[5] The position detection device (2) described in [1] above, in which the excitation coil (31) and the multiple detection coils (32, 33) are formed on a single substrate (3), and the excitation coil (31) is formed on the substrate (3) so as to surround the multiple detection coils (32, 33).

[6] The position detection device (2) described in [5] above, in which the cross-sectional shape of the conductive portion (121) of the moving member (12) is circular, the non-conductive portion is a recess (120) formed in a portion of the circumferential direction of the outer circumferential surface (12a) of the moving member (12), and the substrate (3) faces the recess (120).

[7] A vehicle steering device (1) comprising a shaft (rack shaft 12) made of conductive metal that moves axially back and forth along the vehicle width direction, a housing (13) made of conductive metal that houses the shaft (12), and a position detection device (stroke sensor 2) that detects the position of the shaft (12) relative to the housing (13), in which the wheels (10) are steered by the axial movement of the shaft (12), the shaft (12) is provided with a recess (120) formed by being recessed in the radial direction, the position detection device (2) comprises an excitation coil (31) and detection coils (32, 33) arranged to extend in the vehicle width direction of the shaft (12), a voltage is induced in the detection coils (32, 33) by the magnetic field generated by the excitation coil (31), and the magnitude of the voltage induced in the detection coils (32, 33) changes depending on the position of the shaft (12) relative to the housing (13).

[8] The position detection device (1) described in [7] above, further comprising a cover member (14) made of a non-conductive material that closes the opening (130) of the housing (13), the excitation coil (31) and the multiple detection coils (32, 33) are formed on a single substrate (3), and the substrate (3) is attached to the cover member (14).

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are essential for solving the problems of the invention.

Further, the moving member whose position is to be detected by the stroke sensor 2 is not limited to the rack shaft 12 of the vehicle steering device 1, and may be a vehicle-mounted or non-vehicle-mounted shaft. Further, the shape of the moving member is not limited to a shaft-like body, and various shapes such as a flat plate shape can be used.

1... Vehicle steering device 12... Rack shaft (moving member)
120... Concave portion (non-conductive part) 121... Conductive part 13... Housing 14... Lid member 2... Stroke sensor (position detection device) 3... Substrate 31... Excitation coil 32... Sine wave shape detection coil 33... Cosine wave shape detection coil C2 …Central axis line (axis of symmetry)
301a, 302a, 303a, 304a...first to fourth curved parts

Claims (8)

A position detection device for detecting the position of a moving member in which a conductive part and a non-conductive part having a higher electrical resistance than the conductive part are arranged side by side in a predetermined moving direction,
comprising an excitation coil and a detection coil arranged to extend in the moving direction of the moving member,
A voltage is induced in the detection coil by the magnetic field generated by the excitation coil,
The magnitude of the voltage induced in the detection coil varies depending on the position of the moving member in the moving direction with respect to the detection coil.
Position detection device. A plurality of detection coils are provided, and voltages induced in each of the plurality of detection coils when the movable member is moved have different phases.
The position detection device according to claim 1. the magnitude of the voltage induced in each of the plurality of detection coils changes within a range of one period or less while the movable member moves from one moving end to the other moving end in the axial direction;
The position detection device according to claim 2 . Each of the plurality of detection coils is a combination of two sinusoidal conductor wires whose shape when viewed from a direction perpendicular to the movement direction is symmetrical across a symmetry axis parallel to the movement direction. is the shape,
The position detection device according to claim 2 or 3. The excitation coil and the plurality of 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 1. the conductive portion of the movable member has a circular cross-sectional shape, and the non-conductive portion is a recess formed in a part of an outer circumferential surface of the movable member in a circumferential direction,
The substrate faces the recess.
The position detection device according to claim 5 . A steering device for a vehicle, comprising: a shaft made of a conductive metal that moves back and forth in an axial direction along a vehicle width direction; a housing made of a conductive metal that accommodates the shaft; and a position detection device that detects a position of the shaft relative to the housing, wherein the wheels are steered by the axial movement of the shaft,
The shaft is provided with a recess formed by being recessed in a radial direction,
The position detection device is
An excitation coil and a detection coil are disposed to extend in the vehicle width direction of the shaft,
A voltage is induced in the detection coil by a magnetic field generated by the excitation coil,
the magnitude of the voltage induced in the detection coil varies with the position of the shaft relative to the housing;
Steering device for vehicles. an opening extending in the vehicle width direction is formed in the housing;
further comprising a lid member made of a non-conductive material that closes the opening of the housing,
The excitation coil and the plurality of detection coils are formed on one substrate,
the substrate is attached to the lid member;
The vehicle steering device according to claim 7.

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