CN117734814A - Position detection device and steering device for vehicle - Google Patents

Abstract

Provided are a position detection device which can be miniaturized and a steering device for a vehicle which is provided 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 recess (120) are provided side by side in the moving direction. The stroke sensor (2) is provided with an exciting coil (31) and detection coils (32, 33) which are arranged to extend in the moving direction of the rack shaft (12), and a voltage is induced in the detection coils (32, 33) by a magnetic field generated by the exciting coil (31). The magnitude of the voltage induced by the detection coils (32, 33) varies according to the position of the rack shaft (12) relative to the detection coils (32, 33) in the moving direction. A steering device (1) for a vehicle is provided with a rack shaft (12), a housing (13) that houses the rack shaft (12) and is made of a conductive metal, and a stroke sensor (2) that detects the position of the rack shaft (12) relative to the housing (13).

Description

Position detection device and steering device for vehicle

Technical Field

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

Background

Conventionally, a position detecting device for detecting a position of a moving member is used for a movable part of an automobile, for example. As such a position detection device, the present applicant has proposed a stroke sensor described in patent document 1.

The stroke sensor described in patent document 1 includes: a magnetic field detection unit such as a hall IC; two parallel yokes sandwiching the magnetic field detection unit in the stroke direction of the stroke body; a magnetic circuit forming yoke extending in a stroke direction of the stroke body with a predetermined interval from the two parallel yokes; a magnet disposed between one end of each of the two parallel yokes and the magnetic circuit forming yoke; a parallel magnetic field forming yoke disposed so as to be movable between and opposed to the two parallel yokes and the magnetic circuit forming yoke; and a protruding yoke integrally provided on a surface of the parallel magnetic field forming yoke on a magnetic circuit forming yoke side. In this stroke sensor, the magnetic field strength detected by the magnetic field detecting unit changes according to the position of the parallel magnetic field forming yoke, and therefore the position of the parallel magnetic field forming yoke can be detected according to the magnetic field strength.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2014-98655

Disclosure of Invention

Problems to be solved by the invention

In the stroke sensor described in patent document 1, it is necessary to dispose two parallel yokes and a magnetic path forming yoke so as to sandwich the parallel magnetic field forming yoke and the projecting yoke over the entire movement range of the parallel magnetic field forming yoke, and the installation size of the stroke sensor is increased. Accordingly, an object of the present invention is to provide a position detecting device that can be miniaturized and a steering device for a vehicle provided with the position detecting device.

Means for solving the problems

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a position detecting device for detecting a position of a moving member in which a conductive portion and a non-conductive portion having a resistance greater than that of the conductive portion are provided in parallel in a predetermined moving direction, the position detecting device including an exciting coil and a detecting coil which are disposed to extend in the moving direction of the moving member, a voltage being induced in the detecting coil due to a magnetic field generated by the exciting coil, and a magnitude of the voltage induced in the detecting coil being changed according to a position of the moving member with respect to the detecting coil in the moving direction.

In order to solve the above problems, the present invention provides a steering device for a vehicle, comprising: the vehicle-width-direction-extending detection device comprises a shaft made of conductive metal and moving forward and backward in the vehicle width direction, a housing made of conductive metal for housing the shaft, and a position detection device for detecting the position of the shaft relative to the housing, wherein the shaft is moved in the axial direction to steer the wheel, a recess formed by recessing in the radial direction is formed in the shaft, and the position detection device comprises an exciting coil and a detection coil which are arranged to extend in the vehicle width direction of the shaft, wherein a voltage is induced in the detection coil due to a magnetic field generated by the exciting coil, and the magnitude of the voltage induced in the detection coil is changed according to the position of the shaft relative to the housing.

Effects of the invention

According to the present invention, the position detecting device can be miniaturized. In addition, the miniaturization of the position detection device improves the mountability of the vehicle steering device on the vehicle.

Drawings

Fig. 1 (a) is a schematic diagram showing a configuration of a part of a vehicle in which a vehicle steering device according to an embodiment of the present invention is mounted. And (b) is A-A line cross-sectional view of (a).

Fig. 2 is a perspective view showing the rack shaft, the housing, the cover member, and the base plate.

Fig. 3 (a) is an overall view of wiring patterns formed in the first to fourth metal layers of the substrate as seen from the front surface side. (b) is a partial enlarged view of (a).

Fig. 4 (a) to (d) are plan views each showing the first to fourth metal layers viewed from the front surface side.

Fig. 5 is a graph showing an example of a relationship between a supply voltage supplied from the power supply unit to the exciting coil and an induced voltage induced in the sine-wave-shaped detection coil and an induced voltage induced in the cosine-wave-shaped detection coil.

Fig. 6 (a) is an explanatory diagram schematically showing a relationship between a peak voltage, which is a peak value of an induced voltage induced in the sine wave-shaped detection coil, and a position of the concave portion. (b) The present invention is an explanatory diagram schematically showing a relationship between a peak voltage, which is a peak value of an induced voltage induced in a cosine wave shape detection coil, and a position of a concave portion.

Fig. 7 (a) is a graph showing the position of the rack shaft detected by the stroke sensor, with the horizontal axis and the vertical axis representing the movement amount of the rack shaft from the reference position. (b) The graph is a graph in which the horizontal axis represents the movement amount of the rack shaft from the reference position, and the vertical axis represents the ratio of the detection error of the movement amount of the rack shaft.

Fig. 8 (a) is a cross-sectional view showing an example of a configuration in which the stroke sensor of the embodiment detects the position of the rack shaft mounted with respect to the housing in the comparative example as a detection target of the conductive metal member. (b) A perspective view showing the rack shaft, the detection target, and the housing of the comparative example.

Fig. 9 is a graph showing a detection error of the movement amount of the rack shaft of the comparative example.

Symbol description

1 … a steering device for a vehicle; 12 … rack shaft (moving member)

120 … recess (non-conductive portion); 121 … conductive part

13 … shell; 14 … cover member

2 … stroke sensor (position detecting means); 3 … substrate

31 … field coil; 32 … sine wave shape detecting coil

33 cosine wave shape detection coil; C2.Central axis (symmetry axis)

301a,302a,303a,304a ….

Detailed Description

Embodiment(s)

Fig. 1 (a) is a schematic diagram showing a configuration of a part of a vehicle in which a vehicle steering device 1 according to an embodiment of the present invention is mounted. FIG. 1 (b) is a cross-sectional view taken along line A-A of FIG. 1 (a).

The vehicle steering device 1 is a steer-by-wire steering device, and includes a stroke sensor 2 as a position detection device. Fig. 1 (a) shows a state in which the vehicle steering device 1 is viewed from the rear side in the vehicle front-rear direction, the right side of the drawing corresponds to the right side in the vehicle width direction, and the left side of the drawing corresponds to the left side in the vehicle width direction. In the following description with reference to the drawings, the expression "right" or "left" is sometimes referred to, but this expression is used for convenience of description, and does not limit the arrangement direction of the stroke sensor 2 in the actual use state.

As shown in fig. 1 (a), a vehicle steering device 1 includes: a tie rod 11 connected to the turning wheel 10 (left and right front wheels); a rack shaft 12 connected to the tie rod 11; a housing 13 accommodating the rack shaft 12; a cover member 14 (see fig. 1 (b)) closing the opening of the housing 13; a worm reduction mechanism 15 having a pinion 151 engaged with the rack teeth 122 of the rack shaft 12; an electric motor 16 for applying a vehicle width direction moving force to the rack shaft 12 via the worm reduction mechanism 15; a steering wheel 17 for steering operation by a driver; a steering angle sensor 18 that detects a 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 that detects a position relative to the housing 13 by the stroke sensor 2. The moving direction of the rack shaft 12 is an axial direction parallel to the central axis C1 of the rack shaft 12. The rotating wheel 10 is steered by moving the rack shaft 12 in the axial direction.

In fig. 1 (a), the case 13 is shown by a phantom line, and the inside thereof is shown by a solid line. The rack shaft 12 is made of steel material such as carbon steel, for example, and is supported by a pair of rack bushings 131 attached to both end portions of the housing 13. The worm reduction mechanism 15 includes a worm wheel 152 and a worm 153, and a pinion 151 is fixed to the worm wheel 152. Worm 153 is fixed to motor shaft 161 of electric motor 16.

The electric motor 16 generates torque by a motor current supplied from the steering control device 19, and rotates the worm wheel 152 and the pinion 151 via the worm 153. When the pinion gear 151 rotates, the rack shaft 12 moves linearly forward and backward in 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), a stroke range R is shown by a double arrow, which corresponds to a maximum movement 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 can detect the absolute position of the rack shaft 12 relative to the housing 13 throughout the stroke range R.

(constitution of the Stroke sensor 2)

The stroke sensor 2 includes a substrate 3 disposed opposite to the rack shaft 12, a power supply unit 4, and a calculation unit 5. The stroke sensor 2 detects the position of the rack shaft 12 in the axial direction (moving direction) with respect to the housing 13, and outputs the detected position information 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 corresponds 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 cover member 14, and the base plate 3. In fig. 2, the case 13, the cover member 14, and the substrate 3 are shown separated in the vertical direction in the drawing.

The rack shaft 12 and the housing 13 are made of conductive metal. The rack shaft 12 is, for example, carbon steel for mechanical structure such as S45C, and has a circular cross-section perpendicular to the axial direction in a range facing the base plate 3 except for a portion of the recess 120 described later. The diameter D of the rack shaft 12 is, for example, 25mm. The case 13 is made of, for example, an aluminum alloy having a U-shaped cross section and is formed by die casting, and is opened upward in the vertical direction. The opening 130 of the housing 13 is closed by the cover member 14.

A gap of, for example, 1mm 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. As a material of the cover member 14, for example, a resin such as engineering plastic can be suitably used.

A recess 120 formed by recessing the rack shaft 12 in the radial direction is provided in a portion of the rack shaft 12 facing the base plate 3. The recess 120 is formed in a part of the circumferential direction of the outer circumferential surface 12a of the rack shaft 12. In the present embodiment, the recess 120 is a space, but the recess 120 may be buried by a non-conductive member such as a resin.

The width of the recess 120 in the axial direction of the rack shaft 12 is shorter than the length of the base plate 3 in the longitudinal direction. The portion of the rack shaft 12 where the recess 120 is not provided is a conductive portion 121 having conductivity. That is, the rack shaft 12 is provided with a conductive portion 121 and a non-conductive portion having a larger resistance than the conductive portion 121 in parallel in the axial direction, and in the present embodiment, the non-conductive portion is represented by the recess 120. That is, in the present embodiment, the concave portion 120 is opposed to the base plate 3, and the portions of the rack shaft 12 opposed to the base plate 3 are arranged in the order of the conductive portion 121, the concave portion 120 as the non-conductive portion, and the conductive portion 121 along the axial direction (moving direction).

The recess 120 is formed by, for example, cutting a part of a round bar that is a raw material of the rack shaft 12. In the present embodiment, the bottom surface 120a of the recess 120 is a plane 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 interposed therebetween. The depth Dp of the recess 120 in the radial direction of the rack shaft 12 is, for example, 5mm. The rack shaft 12 is restricted from rotating relative to the housing 13 about the central axis C1 so that the bottom surface 120a always faces parallel to and parallel to the base plate 3.

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

The substrate 3 is a four-layer substrate in which a flat-plate-shaped base material 30 made of a dielectric material such as FR4 (a material obtained by impregnating glass fibers with an epoxy resin and performing a heat curing treatment) is disposed between the first to fourth metal layers 301 to 304. The thickness of each substrate 30 is, for example, 0.3mm. The first to fourth metal layers 301 to 304 are made of copper, for example, and each layer has a thickness of 18 μm, for example. The base plate 3 is a flat rectangle in which the moving direction of the rack shaft 12 is the longitudinal direction (longitudinal direction). The substrate 3 is not limited to a rigid substrate, and may be a flexible substrate.

Fig. 3 (a) is an overall view of wiring patterns formed in the first to fourth metal layers 301 to 304 of the substrate 3 as seen from the front surface 3a side. Fig. 3 (b) is a partial enlarged view of fig. 3 (a). Fig. 4 (a) to (d) are plan views showing the first to fourth metal layers 301 to 304, respectively, as viewed from the front surface 3a side. The wiring patterns shown in fig. 3 (a) and (b) and fig. 4 (a) to (d) are merely examples, and various wiring patterns can be used as long as the substrate 3 is formed so that the effects of the present invention can be obtained.

In fig. 3 (a) and (b) and fig. 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 is shown by a broken line, the wiring pattern of the third metal layer 303 is shown by a one-dot chain line, and the wiring pattern of the fourth metal layer 304 is shown by a two-dot chain line. In fig. 3 (a), a central axis C2 is shown which bisects the substrate 3 in the short-side direction and extends in the long-side direction, and the position of the concave portion 120 in the case where the rack shaft 12 is located at one end and the other end in the range where the absolute position of the rack shaft 12 can be detected by the stroke sensor 2 is shown by a broken line. As shown in fig. 1 (b), the base plate 3 and the concave portion 120 overlap each other in the diameter direction of the rack shaft 12, but in fig. 3 (a), the position of the concave portion 120 is shown so as to be shifted in the short side direction with respect to the base plate 3.

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

The first metal layer 301 includes a first curved portion 301a, a first connector connecting portion 301b connecting one end of the first curved portion 301a to the second through hole 342, and an end connecting portion 301c connecting respective ends of a second curved portion 302a and a fourth curved portion 304a, which will be described later. A second curved portion 302a and a second connector connecting portion 302b connecting one end of the second curved portion 302a with the fourth through hole 344 are formed in the second metal layer 302. A third curved portion 303a and a third connector connecting portion 303b connecting one end portion of the third curved portion 303a to the third through hole 343 are formed in the third metal layer 303. A fourth curved portion 304a and a fourth connector connecting portion 304b connecting one end of the fourth curved portion 304a with the fifth through hole 345 are formed in the fourth metal layer 304.

The other end portions of the first curved portion 301a and the third curved portion 303a are connected to each other by a first passage 351. One end of the end connection portion 301c is connected to the other end of the second curved portion 302a through the second passage 352, and the other end is connected to the other end of the fourth curved portion 304a through the third passage 353.

The first to fourth curved portions 301a,302a,303a,304a are conductor lines bent in a sine wave shape. The first curved portion 301a and the third curved portion 303a, and the second curved portion 302a and the fourth curved portion 304a are symmetrical with respect to the central axis C2 of the substrate 3 as the symmetry axis.

The substrate 3 includes an exciting coil 31 for generating magnetic flux in the conductive portion 121 of the rack shaft 12, and two detecting coils 32 and 33 for interlinking the magnetic flux generated by the conductive portion 121. The exciting coil 31 and the two detecting coils 32 and 33 are arranged to extend in the axial direction of the rack shaft 12. One detection coil 32 of the two detection coils 32, 33 is formed of a first curved portion 301a and a third curved portion 303 a. The other detection coil 33 is formed of a second curved portion 302a, a fourth curved portion 304a, and an end connection portion 301c. That is, the shape of each of the two detection coils 32 and 33 as viewed in the direction perpendicular to the axial direction of the rack shaft 12 is a shape in which two sinusoidal conductor lines symmetrical with each other across the central axis C2 are combined.

The exciting coil 31 is rectangular and has a pair of long side portions 311 and 312 extending in the axial direction of the rack shaft 12 and a pair of short side portions 313 and 314 between the pair of long side portions 311 and 312, and is formed so as to surround the detection coils 32 and 33. In the present embodiment, long side portions 311 and 312 and short side portions 313 and 314 are formed as wiring patterns in the first metal layer 301. As shown in fig. 3 (b), the short side portion 313 on the connector portion 340 side of the pair of short side portions 313, 314 is constituted by two straight portions 313a, 313b sandwiching the first to fourth connector connecting portions 301b, 302b, 303b, 304b, and the end portions of the two straight portions 313a, 313b are connected to the first through hole 341 and the sixth through hole 346 by the connector connecting portions 301d, 301e formed in the first metal layer 301.

The exciting coil 31 is not limited to be formed in the first metal layer 301, and may be formed in any one of the second to fourth metal layers 302 to 304, or may be formed in a plurality of layers. The exciting coil may be formed separately from the substrate 3.

A sinusoidal ac current is supplied from the power supply unit 4 to the exciting coil 31. An eddy current is generated in the conductive portion 121 of the rack shaft 12 by a magnetic flux generated by an alternating current supplied to the exciting coil 31. Due to the eddy current, the density of the magnetic flux interlinking with the two detection coils 32, 33 becomes lower, and the magnetic flux density in the portion facing the conductive portion 121 in the substrate 3 becomes lower than the portion facing the recess 120 as the non-conductive portion. The conductive portion 121 and the concave portion 120 are arranged in the axial direction (moving direction) of the rack shaft 12 in the order of the conductive portion 121, the concave portion 120, and the conductive portion 121 so as to face the substrate 3. Therefore, the magnetic flux density of the portion of the substrate 3 facing the concave portion 120 is greater than the magnetic flux density of the portion facing the conductive portion 121. Therefore, in the two detection coils 32 and 33, the magnetic fluxes passing through the recess 120 are interlinked to generate an induced voltage. The peak value of the voltage induced in the detection coils 32, 33 varies according to the position of the recess 120. Here, the peak value of the voltage is the maximum value of the absolute value of the voltage during one cycle of the ac current supplied to the exciting coil 31.

During the movement of the rack shaft 12 from one moving end to the other moving end in the axial direction, the phases of the voltages respectively induced in the detection coils 32, 33 are different from each other. In the present embodiment, the voltages induced in the detection coils 32, 33 are 90 ° out of phase. Hereinafter, one detection coil 32 of the two detection coils 32 and 33 is referred to as a sine wave-shaped detection coil 32, and the other detection coil 33 is referred to as a cosine wave-shaped detection coil 33.

While the rack shaft 12 moves from one moving end to the other moving end in the axial direction, 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 cycle amount or less. Thus, the stroke sensor 2 can detect the absolute position of the rack shaft 12 over the entire stroke range R in which the rack shaft 12 can move in the axial direction.

As shown in fig. 3 (a), first and second buffer areas E1 and E2 are provided between each of the pair of short side portions 313 and 314 of the exciting coil 31 and the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33, and the first and second buffer areas E1 and E2 are used for suppressing voltages induced in the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33 due to magnetic fluxes generated by currents flowing through the pair of short side portions 313 and 314. In the example shown in fig. 3 (a), the length L1 of the first buffer area E1 in the longitudinal direction of the substrate 3 is the same as the length L2 of the second buffer area E2, but L1 and L2 may be different.

Fig. 5 is a graph showing an example of the relationship between the supply voltage V0 supplied from the power supply unit 4 to the exciting coil 31 and the induced voltage V1 induced in the sine wave-shaped detection coil 32 and the induced voltage V2 induced in the cosine wave-shaped detection coil 33. The horizontal axis of the graph of fig. 5 is a time axis, and the left and right vertical axes represent the supply voltage V0 and the induced voltages V1 and V2. A high-frequency ac voltage of, for example, about 1MHz is supplied as a supply voltage V0 to the exciting coil 31. The induced voltages V1 and V2 are output voltages of the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33, and are output to the arithmetic unit 5 via the cable 7.

In the example shown in fig. 5, the supply voltage V0 is in phase with the induced voltages V1 and V2, but when the recess 120 passes through a position corresponding to an intersection point 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 the rear surface 3b of the substrate 3, the induced voltage V1 induced in the sine wave-shaped detection coil 32 is switched between in phase and in phase. When the recess 120 passes through a position corresponding to an intersection point 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, the induced voltage V2 induced in the cosine wave-shaped detection coil 33 is switched between in-phase and out-of-phase.

Fig. 6 (a) is an explanatory diagram schematically showing a relationship between the peak voltage VS, which is a peak value of the induced voltage V1 induced in the sine wave-shaped detection coil 32, and the position of the concave portion 120. Fig. 6 (b) is an explanatory diagram schematically showing a relationship between the peak value of the induced voltage V2 induced in the cosine wave shape detection coil 33, that is, the peak voltage VC, and the position of the concave portion 120.

In the graphs of peak voltages VS and VC shown in fig. 6 (a) and (b), the horizontal axis represents the position of the center portion of the concave portion 120 in the lateral direction. The horizontal axis P1 represents the position of the center point 120c of the concave portion 120 when the left end portion of the concave portion 120 coincides with the left end portions of the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33. The horizontal axis P2 represents the position of the center point 120c of the concave portion 120 when the right end portion of the concave portion 120 coincides with the right end portions of the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33. In fig. 6 (a) and (b), the concave portion 120 when the center point 120c is located at the position of P1 is indicated by a one-dot chain line, and the concave portion 120 when the center point 120c is located at the position of P2 is indicated by a two-dot chain line. Here, as shown in fig. 2, the center point 120c of the concave portion 120 is the position of the center of the bottom surface 120 a.

In the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33, the magnetic field intensity of the portion facing the conductive portion 121 is weaker than the magnetic field intensity of the portion facing the concave portion 120. Therefore, in the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33, the output voltage changes according to the position of the rack shaft 12. In the graph shown in fig. 6 (a), the induced voltage V1 induced in the sinusoidal detection coil 32 by the peak voltage VS is positive when in phase with the supply voltage V0 supplied to the exciting coil 31, and is negative when in phase with the supply voltage V0. In the graph shown in fig. 6 (b), the peak voltage VC is positive when the induced voltage V2 induced in the cosine-waveform detection coil 33 is in phase with the supply voltage V0 supplied to the exciting coil 31, and is negative when the peak voltage VC is in phase with the supply voltage V0.

In the case where the rack shaft 12 moves from one moving end to the other moving end at a constant speed, as shown in fig. 6 (a) and (b), the peak voltage VS varies in a sine wave shape, and the peak voltage VC varies in a cosine wave shape. Therefore, the arithmetic unit 5 can calculate the position of the rack shaft 12 based on the output voltages of the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33.

As shown in fig. 3 (a), when the positions of the left end portions of the sine-wave-shaped detection coil 32 and the cosine-wave-shaped detection coil 33 in the longitudinal direction of the substrate 3 are set as the reference position O, the lengths of the sine-wave-shaped detection coil 32 and the cosine-wave-shaped detection coil 33 in the longitudinal direction of the substrate 3 are set as L, the position X of the rack shaft 12 when the center point 120c of the concave portion 120 is aligned in the substrate vertical direction with the reference position O is set 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 set as the positive side of the position X of the rack shaft 12, the position X of the rack shaft 12 can be obtained by the following expression (1).

[ number 1]

The arithmetic unit 5 outputs the position obtained by the equation (1) based on the output voltages of the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33 as the position of the rack shaft 12 to the steering control device 19. 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-shaped detection coil 32 and the cosine wave-shaped detection coil 33 is set to u, the arithmetic unit 5 can determine the absolute position of the rack shaft 12 within the length range of (1-u) L. U is a value smaller than 0.5. The smaller the value of u is, the more the absolute position of the rack shaft 12 can be detected over a longer distance, but if the value of u is too small, the induced voltages V1, V2 become small, and the error tends to become large. Therefore, the value of u is preferably 0.01 or more and less than 0.5, for example.

Fig. 7 (a) is a graph showing the position of the rack shaft 12 detected by the stroke sensor 2, with the horizontal axis and the vertical axis representing the movement amount of the rack shaft 12 from the reference position. The value of the vertical axis is an operation value of the above formula (1) based on the induced voltages V1 and V2 obtained by using electromagnetic field simulation. Fig. 7 (b) is a graph showing a ratio of detection errors of the movement amount of the rack shaft 12 on the horizontal axis and the vertical axis from the reference position of the rack shaft 12.

As shown in the graph of fig. 7 (a), the actual position of the rack shaft 12 and the position of the rack shaft 12 obtained by the stroke sensor 2 are substantially in a linear relationship, and as shown in fig. 7 (b), the detection error is suppressed to 5% or less. Further, since the error is not generated by accident such as vibration but is generated stably as a detection characteristic, the error can be corrected by performing a correction operation.

Comparative example

Fig. 8 (a) is a cross-sectional view showing an example of a configuration in which the stroke sensor 2 according to the above embodiment detects the position of the rack shaft 12A to which the detection target 123 as a conductive metal member is attached with respect to the housing 13A. 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 machine construction having a circular cross section perpendicular to the axial direction, similarly to the rack shaft 12 of the above embodiment, but the recess 120 is not formed. The detection target 123 is made of a metal such as steel having the same conductivity as the rack shaft 12A or a good conductivity metal such as a copper alloy or an aluminum alloy having a higher 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 protruding height H of the detection target 123 protruding from the outer peripheral surface 12Aa of the rack shaft 12A in the direction perpendicular to the base plate 3 is 5mm, which is the same as the depth Dp of the recess 120 of the rack shaft 12 of the above embodiment. The width W2 of the air gap G between the surface 3a of the substrate 3 and the opposing surface 123a of the detection target 123 is 1mm or less as the width W1 of the air gap G in the above embodiment, in parallel with the surface 3a of the substrate 3 in the detection target 123.

The case 13A is made of an aluminum alloy having a U-shaped cross section and is opened upward in the vertical direction, similarly to the case 13 of the above embodiment. However, not only the amount of the protruding height H of the detection target 123, but also the outer dimension of the housing 13A in the direction perpendicular to the substrate 3 is larger than the housing 13 of the above embodiment.

In this comparative example, the magnetic field intensity of the portion facing the detection target 123 in the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33 is weaker than the magnetic field intensity of the portion not facing the detection target 123. Due to the difference in magnetic field intensity, the sine wave-shaped detection coil 32 and the cosine wave-shaped detection coil 33 output voltage changes according to the position of the rack shaft 12A.

Fig. 9 is a graph showing a detection error of the movement amount of the rack shaft 12A of the comparative example. As shown in the graph, when the movement amount 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.

As a cause of this increase in detection error, it is considered that the magnetic field generated by the exciting coil 31 also acts on the housing 13A on the side of the detection target 123. That is, in the above embodiment, the distance between the rack shaft 12 made of the conductive metal and the substrate 3 is close, and thus is not easily affected by the magnetic field acting on the housing 13A, but in the comparative example, the length of the detection target 123 in the axial direction of the rack shaft 12 is relatively short with respect to the substrate 3, and thus is considered to be greatly affected by the magnetic field acting on the housing 13A, as compared with the above embodiment.

(effects of the embodiment)

According to the embodiment described above, by disposing the base plate 3 so as to face the rack shaft 12 in which the recess 120 is formed, the position of the rack shaft 12 with respect to the housing 13 can be detected, and therefore the installation size of the stroke sensor 2 can be reduced. More specifically, since the change in the output voltages of the sine-wave-shaped detection coil 32 and the cosine-wave-shaped detection coil 33 caused by the position of the rack shaft 12 occurs by the concave portion 120, the size of the housing 13A is not increased by attaching the detection target 123 to the rack shaft 12A as in the comparative example described above, for example. In addition, since the installation size of the stroke sensor 2 can be reduced, the vehicle steering device 1 can be made smaller and lighter.

(summary of embodiments)

Next, the technical ideas grasped from the above-described embodiments are described by referring to the symbols and the like in the embodiments. However, each symbol in the following description does not limit the constituent elements in the claims to the members specifically shown in the embodiments and the like.

[1] A position detection device (2) is a position detection device (travel sensor (2)) for detecting the position of a moving member (rack shaft (12)), wherein the moving member (rack shaft (12)) is provided with a conductive part (121) and a non-conductive part (concave part (120) having a resistance greater than that of the conductive part (121) in a predetermined moving direction, the position detection device (2) is provided with an exciting coil (31) and detection coils (32, 33) which are arranged to extend in the moving direction of the moving member (12), a voltage is induced in the detection coils (32, 33) due to a magnetic field generated by the exciting coil (31), and the magnitude of the voltage induced in the detection coils (32, 33) is changed according to the position of the moving member (12) relative to the detection coils (32, 33) in the moving direction.

[2] The position detection device (2) according to [1] above, comprising a plurality of the detection coils (32, 33), wherein phases of voltages induced in the plurality of the detection coils (32, 33) are different from each other when the moving member (12) moves.

[3] The position detection device (2) according to item [2], wherein the magnitude of the voltage induced in each of the plurality of detection coils (32, 33) varies within a range of one cycle amount or less during the movement of the movement member (12) from one movement end to the other movement end in the axial direction.

[4] According to the position detecting device (2) of [2] or [3], the plurality of detecting coils (32, 33) are each formed by combining two sinusoidal conductor lines (first to fourth curved portions 301a,302a,303a,304 a) symmetrical with each other across a symmetry axis (central axis C2) parallel to the moving direction, as viewed in a direction perpendicular to the moving direction.

[5] The position detection device (2) according to item [1], wherein the exciting coil (31) and the plurality of detection coils (32, 33) are formed on a single substrate (3), and the exciting coil (31) is formed on the substrate (3) so as to surround the plurality of detection coils (32, 33).

[6] The position detecting device (2) according to item [5], wherein the cross-sectional shape of the conductive portion (121) in the moving member (12) is circular, the non-conductive portion is a recess (120) formed in a part of the outer circumferential surface (12 a) of the moving member (12) in the circumferential direction, and the substrate (3) is opposed to the recess (120).

[7] A steering device (1) for a vehicle is provided with: the vehicle-width-direction-oriented steering device comprises a shaft (rack shaft 12) made of conductive metal and moving in the axial direction in a forward and backward direction, a housing (13) made of conductive metal and housing the shaft (12), and a position detection device (stroke sensor 2) for detecting the position of the shaft (12) relative to the housing (13), wherein the shaft (12) moves in the axial direction to steer the wheel (10), a recess (120) formed by recessing in the radial direction is provided in the shaft (12), the position detection device (2) is provided with an exciting coil (31) and detecting coils (32, 33) which are arranged to extend in the vehicle width direction of the shaft (12), and a voltage is induced in the detecting coils (32, 33) due to a magnetic field generated by the exciting coil (31), and the magnitude of the voltage induced in the detecting coils (32, 33) changes according to the position of the shaft (12) relative to the housing (13).

[8] According to the position detection device (1) of [7], an opening (130) extending in the vehicle width direction is formed in the case (13), the position detection device further includes a cover member (14) made of a non-conductive material for closing the opening (130) of the case (13), the exciting coil (31) and the plurality of detection coils (32, 33) are formed on one substrate (3), and the substrate (3) is mounted on the cover member (14).

The embodiments of the present invention have been described above, but the embodiments described above do not limit the invention according to the claims. Note that the combination of the features described in the embodiments is not necessarily required for a means for solving the problems of the invention.

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

Claims (8)

1. A position detecting device for detecting a position of a moving member in which a conductive portion and a non-conductive portion having a larger resistance than the conductive portion are arranged side by side in a predetermined moving direction,

the position detecting device comprises an exciting coil and a detecting coil which are arranged along the moving direction of the moving member,

a voltage is induced in the detection coil due to the magnetic field generated by the exciting coil,

the magnitude of the voltage induced in the detection coil varies according to the position of the moving member with respect to the detection coil in the moving direction.

2. The position detection apparatus according to claim 1, comprising a plurality of the detection coils, wherein phases of voltages induced in the plurality of the detection coils are different from each other when the moving member moves.

3. The position detecting device according to claim 2, wherein a magnitude of the voltage induced in each of the plurality of detection coils varies within a range of one cycle amount or less during movement of the moving member from one moving end to the other moving end in the axial direction.

4. The position detecting device according to claim 2 or 3, wherein each of the plurality of detecting coils has a shape as viewed from a direction perpendicular to the moving direction, and is formed by combining two sinusoidal conductor lines symmetrical with each other across a symmetry axis parallel to the moving direction.

5. The position detecting device according to claim 1, wherein the exciting coil and the plurality of detecting coils are formed on one substrate,

the exciting coil is formed on the substrate so as to surround the plurality of detection coils.

6. The position detecting device according to claim 5, wherein the cross-sectional shape of the conductive portion is circular, the non-conductive portion is a recess formed in a part of the outer peripheral surface of the moving member in the circumferential direction,

the substrate is opposite to the recess.

7. A steering device for a vehicle is provided with: a shaft made of a conductive metal and moving in the axial direction along the vehicle width direction, a housing made of a conductive metal housing the shaft, and a position detecting device detecting the position of the shaft relative to the housing, the shaft being moved in the axial direction to steer the wheel,

the shaft is provided with a recess formed by being recessed in a radial direction,

the position detection device comprises an exciting coil and a detection coil which are arranged along the vehicle width direction of the shaft,

a voltage is induced in the detection coil due to the magnetic field generated by the exciting coil,

the magnitude of the voltage induced in the detection coil varies according to the position of the shaft relative to the housing.

8. The vehicle steering device according to claim 7, wherein an opening portion extending in the vehicle width direction is formed in the housing,

the vehicle steering device further includes a cover member made of a non-conductive material for closing the opening of the housing,

the exciting coil and the plurality of detecting coils are formed on one substrate,

the base plate is mounted to the cover member.