JP2014162248A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of accurately detecting an absolute steering angle.SOLUTION: An EPS (an electric power steering device) includes: a steering shaft 11 which integrally rotates with a steering component; a rotation angle sensor 50 which detects a rotation angle of the steering shaft 11; a movable component 31 which is threadedly engaged with a male screw part 14D formed at an outer peripheral portion of the steering shaft 11 and moves in an axial direction ZA according to rotation of the steering shaft 11; and a position sensor 33 which detects a position of the movable component 31 in the axial direction ZA. The EPS calculates an absolute steering angle on the basis of the rotation angle of the steering shaft 11 and the position of the movable component 31 in the axial direction ZA.

Description

  The present invention relates to an electric power steering apparatus that calculates an absolute steering angle.

  The conventional electric power steering apparatus has an electric motor, a ball screw mechanism, a first rotation angle sensor, and a second rotation angle sensor. The electric motor assists the reciprocation of the rack shaft. The ball screw mechanism converts the rotation of the output shaft of the electric motor into the reciprocating motion of the rack shaft. The first rotation angle sensor is located in the electric motor. The first rotation angle sensor detects the rotation angle of the electric motor. The second rotation angle sensor is attached to the steering shaft. The second rotation angle sensor detects the rotation angle of the steering shaft. The conventional electric power steering device calculates the rotation angle (absolute steering angle) of the steering shaft from the neutral position based on the output value of the first rotation angle sensor and the output value of the second rotation angle sensor. Patent Document 1 shows an example of a conventional electric power steering apparatus.

JP 2003-75109 A

  In the conventional electric power steering apparatus, a meshing portion between the rack shaft and the steering shaft exists between the first rotation angle sensor and the second rotation angle sensor. As a result, the output value of the first rotation angle sensor in the design and the steering shaft when the steering shaft makes one rotation due to the influence of backlash at the meshing portion of the rack shaft and the steering shaft and the detection error of each rotation angle sensor. In some cases, the actual output value of the first rotation angle sensor at the time of one rotation differs greatly from each other. For this reason, in the conventional electric power steering apparatus, there is a possibility that the rotational speed of the steering shaft cannot be accurately determined. The conventional electric power steering apparatus uses a ball screw mechanism as a speed reduction mechanism for the electric motor, but the same problem occurs when a gear mechanism such as a worm gear mechanism is used as the speed reduction mechanism for the electric motor.

  The present invention was created based on the above background, and an object thereof is to provide an electric power steering apparatus capable of more accurately detecting an absolute steering angle.

  The means includes: a steering shaft that rotates integrally with a steering component; a rotation angle sensor that detects a rotation angle of the steering shaft; and a screw portion that is formed on an outer peripheral portion of the steering shaft. A movable part that moves in the axial direction of the steering shaft according to the rotation of the steering shaft, a position sensor that detects a position of the movable part in the axial direction of the steering shaft, a rotation angle of the steering shaft, and an axial direction of the steering shaft And an electric power steering apparatus including a calculating unit that calculates an absolute steering angle based on the position of the movable part.

  In the electric power steering apparatus, the rotation angle sensor detects the rotation angle of the steering shaft, and the position sensor detects the position of the movable part screwed to the steering shaft. For this reason, compared with the structure of the conventional electric power steering apparatus, the influence of the play of the meshing part of a steering shaft and a rack shaft is suppressed. Therefore, the electric power steering apparatus can more accurately detect the absolute steering angle based on the rotation angle of the steering shaft and the position of the movable part.

  One form of the means is as follows: “The calculation unit calculates a rotational position of the steering shaft based on a rotational angle of the steering shaft, and the steering shaft based on a position of the movable part in an axial direction of the steering shaft. An electric power steering apparatus that calculates the absolute steering angle based on the rotational position of the steering shaft and the rotational speed of the steering shaft.

One mode of the above means includes an “electric power steering apparatus having a guide portion that restricts the rotational motion of the movable part”.
In the electric power steering apparatus described above, the rotational movement of the movable part is limited by the guide portion, and therefore the relationship between the amount of movement of the movable part in the axial direction of the steering shaft with respect to the amount of rotation of the steering shaft changes as the movable part rotates. It is suppressed. Therefore, it is suppressed that the precision of the position of the movable component in the axial direction of the steering shaft is lowered.

One mode of the above means includes an “electric power steering apparatus that applies an assist force for assisting an operation of the steering component based on the absolute steering angle”.
One mode of the above means includes an “electric power steering apparatus having a sliding part that contacts the outer surface of the movable part and guides the movement of the movable part in the axial direction of the steering shaft”.

  In the electric power steering device, the sliding part is prevented from inclining with respect to the axial direction of the steering shaft when the sliding part comes into contact with the outer surface of the moving part. Therefore, it is suppressed that the precision of the position of the movable component in the axial direction of the steering shaft is lowered.

  One form of the above means is that the steering shaft has an input shaft, an output shaft, and a torsion bar, and the input shaft and the output shaft are connected to each other by the torsion bar, and the rotation angle The sensor has a rotation angle of one of the input shaft and the output shaft, and the movable part has an electric power steering device attached to one of the input shaft and the output shaft.

  In the electric power steering apparatus, the rotation angle sensor and the position sensor detect the operation of the same component of the input shaft or the output shaft in the steering shaft. For this reason, compared with the structure assumed that the rotation angle sensor and the position sensor detect the operation of different parts of the input shaft and the output shaft in the steering shaft, the influence of the variation in the twist amount of the torsion bar is suppressed. Therefore, the electric power steering apparatus can more accurately obtain the absolute steering angle based on the rotation angle of the steering shaft and the position of the movable part.

  The electric power steering apparatus can detect the absolute steering angle more accurately.

The block diagram which shows the structure of the electric power steering apparatus of embodiment. It is sectional drawing of the electric power steering apparatus of embodiment, (a) is sectional drawing of the Z1-Z1 line | wire of FIG. 1, (b) is an enlarged view of a movable part and a part of its periphery. It is sectional drawing of the sensor unit of embodiment, and sectional drawing of the Z2-Z2 line | wire of Fig.2 (a). It is a graph which shows the relationship between the steering angle of embodiment, and the output value of a sensor, (a) is a graph which shows the relationship between a steering angle and the output value of a rotation angle sensor, (b) is an output of a steering angle and a position sensor. A graph showing the relationship between values.

With reference to FIG. 1, the configuration of an electric power steering apparatus (hereinafter referred to as “EPS1”) will be described.
The EPS 1 includes an EPS main body 10, an assist device 20, a sensor unit 30, and a control device 70. The EPS 1 assists the steering of the steering component 2 by the assist device 20. For example, a steering wheel is used as the steering component 2.

  The EPS main body 10 includes a steering shaft 11, a rack shaft 15, a ball screw mechanism 16, and a tie rod 17. The EPS main body 10 reciprocates the rack shaft 15 by the rotation of the steering shaft 11 as the steering component 2 rotates. The EPS main body 10 changes the turning angle of the wheel 3 via the tie rod 17 by the reciprocating motion of the rack shaft 15.

  The steering shaft 11 includes a column shaft 12, an intermediate shaft 13, and a pinion shaft 14. The steering shaft 11 rotates integrally with the steering component 2. The steering shaft 11 has a configuration in which the column shaft 12, the intermediate shaft 13, and the pinion shaft 14 rotate integrally as the steering component 2 rotates. The steering shaft 11 is meshed with the rack shaft 15 at the pinion shaft 14.

  The rack shaft 15 is connected to the tie rods 17 at both ends in the axial direction of the rack shaft 15 (hereinafter referred to as “rack axial direction”). The rack shaft 15 is formed with a threaded portion 15A over a predetermined range in the rack axis direction. The rack shaft 15 is formed with a plurality of rack teeth (not shown) over a predetermined range in the rack axis direction at a portion different from the screw portion 15A. The rack shaft 15 reciprocates in the rack axis direction as the steering shaft 11 rotates.

  The ball screw mechanism 16 includes a screw portion 15A, a ball nut 16A, and a plurality of balls (not shown). The ball screw mechanism 16 has a configuration in which a plurality of balls are arranged in a spiral rolling path formed by the ball nut 16A surrounding the screw portion 15A so that the plurality of balls can roll. . In the ball screw mechanism 16, when the ball nut 16A rotates, the rack shaft 15 reciprocates in the rack axis direction via a plurality of balls.

  The assist device 20 includes a brushless motor as the electric motor 21, a first bevel gear 22, a second bevel gear 23, and a hollow shaft 24. The assist device 20 has a configuration in which the first bevel gear 22 is connected to the output shaft 21 </ b> A of the electric motor 21 and the second bevel gear 23 is fixed to the hollow shaft 24. The assist device 20 has a configuration in which a first bevel gear 22 and a second bevel gear 23 are meshed with each other. The assist device 20 is attached to the ball nut 16 </ b> A at the hollow shaft 24. The assist device 20 transmits the rotation of the electric motor 21 to the ball screw mechanism 16 through the bevel gears 22 and 23 and the hollow shaft 24, thereby reciprocating the rack shaft 15 by the ball screw mechanism 16 in the rack axis direction. Is applied to the rack shaft 15. In the assist device 20, the axis of the output shaft 21 </ b> A of the electric motor 21 is oblique to the rack axis direction. As described above, the EPS 1 has a configuration of a rack cross type electric power steering apparatus.

  The sensor unit 30 rotates the steering shaft 11 (hereinafter referred to as “steering angle θ”) accompanying the operation of the steering component 2 and a force for rotating the steering shaft 11 applied to the steering shaft 11 as the steering component 2 is operated. (Hereinafter referred to as “steering torque τ”). The sensor unit 30 transmits a signal based on the steering angle θ and a signal based on the steering torque τ to the control device 70.

  The steering angle θ is indicated as a positive value when the steering component 2 is rotated clockwise (clockwise). The steering angle θ is shown as a negative value when the steering component 2 is rotated counterclockwise (counterclockwise). When the steering component 2 is rotated clockwise (clockwise), the vehicle turns right. When the steering component 2 is rotated counterclockwise (counterclockwise), the vehicle turns left.

  The control device 70 includes a calculation unit 71. The control device 70 executes assist control for assisting steering by the assist device 20 based on the signal received from the sensor unit 30. The control device 70 calculates a steering angle from the neutral position of the steering component 2 (hereinafter, “absolute steering angle”) in the calculation unit 71. The control device 70 calculates an assist force for assisting steering based on the absolute steering angle and the steering torque τ in the assist control. The control device 70 controls driving of the electric motor 21 based on the assist force.

  A detailed configuration of the pinion shaft 14 will be described with reference to FIG. The “axial direction ZA” indicates a direction along the axial direction of the pinion shaft 14. The “radial direction ZB” indicates a normal direction of the axial direction ZA. The “circumferential direction ZC” indicates a direction along the rotation direction of the pinion shaft 14.

  The pinion shaft 14 has an input shaft 14A, an output shaft 14B, and a torsion bar 14C. The pinion shaft 14 has a configuration in which an input shaft 14A and an output shaft 14B are connected by a torsion bar 14C.

The input shaft 14A has a male screw portion 14D and a protruding portion 14E. The male screw portion 14D corresponds to a “screw portion”.
The male thread portion 14D is formed over a predetermined range in the axial direction ZA at the outer peripheral portion of the input shaft 14A.

  The protrusion 14E protrudes in the radial direction ZB from the outer peripheral surface of the input shaft 14A. The protrusion 14E has an annular shape in a plan view of the input shaft 14A. The protruding portion 14E is located closer to the rack shaft 15 than the male screw portion 14D in the axial direction ZA.

A detailed configuration of the sensor unit 30 will be described with reference to FIGS. 2 and 3.
The sensor unit 30 includes a movable part 31, two sliding parts 32, a position sensor 33, two ball bearings 35 and 36, a housing 40, a rotation angle sensor 50, a torque sensor 60, and a circuit unit (not shown). Have. The sensor unit 30 transmits the signal of the position sensor 33, the signal of the rotation angle sensor, and the signal of the torque sensor 60 to the control device 70 (see FIG. 1) via the circuit unit.

  The housing 40 has an internal space 41. The housing 40 accommodates the movable part 31, the sliding part 32, the position sensor 33, the rotation angle sensor 50, and the torque sensor 60 in the internal space 41. The housing 40 supports the pinion shaft 14 via the ball bearings 35 and 36 in a state where the pinion shaft 14 can rotate with respect to the housing 40.

  A resolver is used as the rotation angle sensor 50. The rotation angle sensor 50 includes a resolver rotor 51 and a resolver stator 52. The rotation angle sensor 50 outputs a signal corresponding to the steering angle θ within one rotation of the steering shaft 11 (input shaft 14A) (hereinafter, “rotational position of the steering shaft 11”) to the circuit unit.

The resolver rotor 51 is fixed to the input shaft 14A.
The resolver stator 52 surrounds the resolver rotor 51. The resolver stator 52 is fixed to the housing 40.

  The torque sensor 60 is located closer to the rack shaft 15 than the rotation angle sensor 50. The torque sensor 60 includes a magnet part 61, a magnetic yoke part 62, a magnetism collecting part 63, and a magnetic detection element (not shown). The torque sensor 60 outputs a signal corresponding to the twist amount of the torsion bar 14C, that is, the steering torque τ, to the circuit unit.

The magnet part 61 is fixed to the input shaft 14A.
The magnetic yoke portion 62 is fixed to the output shaft 14B. The magnetic yoke part 62 surrounds the magnet part 61. The magnetic yoke part 62 collects the magnetic flux of the magnet part 61.

The magnetic flux collector 63 is fixed to the housing 40. The magnetism collecting part 63 surrounds the magnetic yoke part 62. The magnetism collecting unit 63 collects the magnetic flux of the magnetic yoke unit 62.
The magnetic detection element outputs a signal corresponding to a change in the magnetic flux of the magnetic flux collector 63 to the circuit unit.

  The movable part 31 is made of a metal material. The movable part 31 is screwed into the male thread portion 14D of the input shaft 14A. The movable part 31 has an annular shape in plan view. The movable component 31 has a female thread portion 31A on the inner peripheral surface. The movable component 31 has two first guide portions 31B (see FIG. 3) at the outer peripheral portion. The movable component 31 is in contact with the sliding component 32 on the outer surface 31C other than the first guide portion 31B.

  The sliding component 32 is made of a resin material. As the sliding component 32, for example, a low friction sheet is used. The sliding component 32 is fixed to the housing 40. The sliding component 32 has an arc shape in plan view. The two sliding parts 32 are spaced apart from each other in the circumferential direction ZC. In the two sliding parts 32, a second guide portion 34 (see FIG. 3) is formed as a space between the two sliding parts 32 in the circumferential direction ZC. The sliding component 32 guides the movement of the movable component 31 in the axial direction ZA by contacting the outer surface 31 </ b> C of the movable component 31.

  The second guide portion 34 is fitted with the first guide portion 31B. The dimension of the second guide part 34 in the circumferential direction ZC is equal to the dimension of the first guide part 31B in the circumferential direction ZC. The second guide part 34 limits the rotation of the movable part 31 in cooperation with the first guide part 31B.

  The position sensor 33 faces the movable part 31 in the axial direction ZA. The position sensor 33 is located closer to the rack shaft 15 than the movable part 31. The position sensor 33 is located between the male threaded portion 14D and the protruding portion 14E of the input shaft 14A. In the position sensor 33, the position in the axial direction ZA relative to the input shaft 14A is determined by the protrusion 14E. As the position sensor 33, for example, an ultrasonic sensor is used. The position sensor 33 transmits ultrasonic waves toward the movable part 31. The position sensor 33 receives the reflected wave reflected by the movable part 31. The position sensor 33 transmits a signal corresponding to the distance from the position sensor 33 to the movable part 31 to the circuit unit based on the time from transmission to reception. The position sensor 33 has a signal output value that increases as the distance from the position sensor 33 to the movable part 31 increases.

The operation of the movable part 31 will be described with reference to FIGS.
The pinion shaft 14 rotates clockwise as the steering component 2 rotates clockwise. In the movable part 31, a force that rotates the movable part 31 clockwise by the clockwise rotation of the pinion shaft 14 acts on the movable part 31. The movable component 31 is limited to rotate clockwise by the first guide portion 31 </ b> B and the second guide portion 34. As a result, the pinion shaft 14 rotates relative to the movable component 31. For this reason, the movable component 31 is separated from the position sensor 33 in the axial direction ZA by the clockwise rotation of the pinion shaft 14.

  The pinion shaft 14 rotates counterclockwise as the steering component 2 rotates counterclockwise. In the movable part 31, a force that rotates the movable part 31 counterclockwise by the counterclockwise rotation of the pinion shaft 14 acts on the movable part 31. The movable component 31 is restricted from rotating counterclockwise by the first guide portion 31 </ b> B and the second guide portion 34. The pinion shaft 14 rotates relative to the movable part 31. For this reason, the movable part 31 approaches the position sensor 33 in the axial direction ZA by the counterclockwise rotation of the pinion shaft 14.

  With reference to FIG. 4, the output state of the signal of the rotation angle sensor 50 and the signal of the position sensor 33 and the method for detecting the absolute steering angle will be described. In addition, in the following description with reference to FIG. 4, each component regarding EPS1 to which the code | symbol was attached | subjected shows each component described in FIG. 1 or FIG.

  As shown in FIG. 4A, the rotation angle sensor 50 outputs a sawtooth waveform signal. The signal of the rotation angle sensor 50 has an output value “0” every time the steering component 2 makes one rotation. The output of the rotation angle sensor 50 increases as the absolute value of the steering angle θ increases within the range of the steering angle θ at which the steering component 2 makes one rotation.

  As shown in FIG. 4B, the output value of the signal from the position sensor 33 increases as the distance between the position sensor 33 and the movable part 31 increases. That is, the output value of the signal from the position sensor 33 increases as the steering angle θ in the clockwise direction of the steering component 2 increases with the neutral position as a reference. The signal of the position sensor 33 decreases as the absolute value of the steering angle θ in the counterclockwise direction of the steering component 2 increases with the neutral position as a reference.

  Next, a method for detecting the absolute steering angle will be described. In the following description, it is assumed that the rotation angle sensor 50 outputs the output value S1 and the position sensor 33 outputs the output value S2 as the steering component 2 rotates.

  As shown in FIG. 4A, when the rotation angle sensor 50 outputs the output value S1, the calculation unit 71 calculates four angles θ1, θ2, θ3, and θ4 as the rotation position of the steering shaft 11. To do. On the other hand, as shown in FIG. 4B, when the position sensor 33 outputs the output value S2, the steering angle θ is located in the region of the first right rotation. For this reason, the calculation unit 71 calculates the steering shaft 11 as one rotation in the clockwise direction. Therefore, the calculation unit 71 calculates the absolute steering angle as the angle θ3 by the combination of the output value S1 of the rotation angle sensor 50 and the output value S2 of the position sensor 33.

  The operation of the EPS 1 will be described. The “virtual EPS” has a rotation angle sensor A1 that detects the rotation angle of the steering shaft and a rotation angle sensor A2 that detects the rotation angle of the electric motor. The virtual EPS is different from the EPS 1 in that the movable part 31, the sliding part 32, and the position sensor 33 are omitted.

The virtual EPS calculates the absolute steering angle as follows.
As the reduction ratio of the virtual EPS, a decimal point value is used so that the rotation speed of the steering shaft can be determined. The reduction ratio of the virtual EPS is set to 18.3.

  In the virtual EPS, the rotation angle sensor A1 detects the rotation angle within one rotation of the steering shaft, and the rotation angle sensor A2 detects the rotation number of the steering shaft. Thereby, virtual EPS calculates an absolute steering angle by each rotation angle sensor A1, A2. In virtual EPS, when the output value of the signal of the rotation angle sensor A1 increases, it is determined that the steering shaft is rotating clockwise. In virtual EPS, when the output value of the signal of the rotation angle sensor A1 decreases, it is determined that the steering shaft is rotating counterclockwise.

The discrimination of the number of rotations of the steering shaft by the rotation angle sensor A2 will be described.
The rotation angle sensor A2 calculates the rotation angle of the decimal value of the rotation angle of the steering shaft × the reduction ratio. The rotation angle sensor A2 outputs a signal corresponding to 360 × 0.3 = 108 ° when the steering shaft makes one clockwise rotation. The rotation angle sensor A2 outputs a signal corresponding to 216 ° when the steering shaft makes two clockwise rotations.

  In the virtual EPS, when the rotation angle sensor A1 is 360 °, the rotation angle sensor A2 has an angle within the range of 54 ° (108 ° -108 ° / 2) or more and 162 ° (108 ° + 108 ° / 2) or less. When the corresponding signal is output, it is determined that the steering shaft has made one clockwise rotation. In the virtual EPS, when the rotation angle sensor A1 is 360 °, the rotation angle sensor A2 outputs a signal corresponding to an angle within a range greater than 162 ° and 260 ° (216 ° + 108 ° / 2) or less. It is determined that the steering shaft has made two clockwise rotations.

  On the other hand, the rotation angle sensor A2 outputs a signal corresponding to 252 ° (360 ° -108 °) when the steering shaft rotates once counterclockwise. The rotation angle sensor A2 outputs a signal corresponding to 144 ° (360 ° to 216 °) when the steering shaft rotates twice counterclockwise. The determination of the number of rotations of the steering shaft is the same as in the case where the steering shaft is clockwise, and the description thereof is omitted.

  By the way, the virtual EPS has a meshing portion between the steering shaft (pinion shaft) and the rack shaft and a meshing portion of each bevel gear between the steering shaft and the electric motor. There may be a deviation between the designed reduction ratio and the actual reduction ratio due to backlash and engagement errors in these engagement portions. Hereinafter, a case where the actual reduction ratio becomes 18.5 in the virtual EPS will be described.

  When the rotation angle sensor A1 is 360 ° (0 °), the rotation angle sensor A2 is calculated as 360 × 0.5 = 180 °. For this reason, the virtual EPS control device determines that the steering shaft has made two clockwise rotations despite the steering shaft having made one clockwise rotation. Accordingly, the virtual EPS may erroneously determine the number of rotations of the steering shaft when the actual reduction ratio is different from the designed reduction ratio.

  In contrast, the EPS 1 of the present embodiment calculates the absolute steering angle by the position sensor 33 and the rotation angle sensor 50. That is, the calculation unit 71 of the EPS 1 calculates the rotational position of the steering shaft 11 based on the signal from the rotation angle sensor 50, and detects the rotational direction and the rotational speed of the steering shaft 11 based on the signal from the position sensor 33. In the EPS 1, the rotation angle sensor 50 and the position sensor 33 are arranged without passing through the meshing portions of the pinion shaft 14 and the rack shaft 15 and the meshing portions of the bevel gears 22 and 23. For this reason, the rotation angle sensor 50 and the position sensor 33 are avoided from the influence of rattling of the meshing portions of the steering shaft 11 and the rack shaft 15 and the meshing portions of the bevel gears 22 and 23 as in virtual EPS. Accordingly, the EPS 1 is prevented from erroneously determining the rotational speed of the steering shaft 11 due to the actual reduction ratio being different from the designed reduction ratio.

The EPS 1 of the present embodiment has the following effects.
(1) The EPS 1 detects the absolute steering angle using the position sensor 33 and the rotation angle sensor 50. The position sensor 33 and the rotation angle sensor 50 are arranged close to each other. According to this structure, the influence of the play of the meshing part with the steering shaft 11 and the rack shaft 15 and the play of the meshing part of each bevel gear are suppressed. Therefore, EPS1 can acquire an absolute steering angle more accurately than virtual EPS.

  Further, the EPS 1 determines the rotational direction and the rotational speed of the steering shaft 11 by the position sensor 33. For this reason, since the position sensor 33 does not detect the steering angle θ, high accuracy is not required. For this reason, the EPS 1 can use an inexpensive position sensor.

  (2) The EPS 1 includes a first guide portion 31B formed on the movable component 31 and a second guide portion 34 formed as a space between the two sliding components 32 in the circumferential direction ZC. The first guide part 31 </ b> B is fitted to the second guide part 34. According to this configuration, the movable component 31 is restricted from rotating in the rotation direction of the input shaft 14A as the input shaft 14A rotates. For this reason, when the movable part 31 rotates with respect to the housing 40, it is suppressed that the relationship of the movement amount of the movable part 31 with respect to the rotation amount of the steering shaft 11 in the axial direction ZA changes. Therefore, the accuracy of the position of the movable part 31 in the axial direction ZA is suppressed from decreasing.

  (3) The EPS 1 has a sliding component 32 that contacts the outer surface of the movable component 31. According to this configuration, the sliding component 32 suppresses the movable component 31 from being inclined with respect to the axial direction ZA. Therefore, it is suppressed that the accuracy of the position of the movable part 31 in the axial direction ZA is lowered.

  (4) The position sensor 33 and the rotation angle sensor 50 are attached to the input shaft 14A. According to this configuration, the twist amount of the torsion bar 14C varies as compared with the configuration in which the rotation angle sensor 50 and the position sensor 33 are assumed to detect the operation of different parts of the input shaft 14A and the output shaft 14B in the steering shaft 11. The influence of can be eliminated. Therefore, the EPS 1 can acquire the absolute steering angle more accurately.

  (5) In the position sensor 33, the position of the axial direction ZA relative to the input shaft 14A is determined by the protrusion 14E formed on the input shaft 14A. According to this configuration, the relative positions of the position sensor 33 and the movable part 31 at the neutral position can be determined with high accuracy and easily compared to a configuration in which the protrusion 14E is omitted from the input shaft 14A.

  The electric power steering apparatus includes an embodiment different from the above embodiment. Hereinafter, the modification of the said embodiment as other embodiment of this electric power steering device is shown. The following modifications can be combined with each other.

  In the embodiment, the position sensor 33 is a non-contact ultrasonic sensor. However, the type of the position sensor 33 is not limited to the content exemplified in the embodiment. For example, the position sensor 33 of the modified example is a non-contact type position sensor such as a magnetostrictive position sensor, a laser displacement meter, or a capacitance type position sensor. Further, as the position sensor 33 of another modified example, a contact type position sensor that detects the position of the movable part 31 in the axial direction ZA by contacting the movable part 31 is used.

  -The resolver is used for the rotation angle sensor 50 of embodiment. However, the type of the rotation angle sensor 50 is not limited to the content exemplified in the embodiment. For example, the rotation angle sensor 50 according to the modification uses an encoder, a Hall IC, an MR element, a torque sensor as a twin resolver, and the like. When a twin resolver is used as the rotation angle sensor 50 of the modified example, the torque sensor 60 is omitted.

In the sensor unit 30 of the embodiment, the position sensor 33 and the rotation angle sensor 50 are attached to the input shaft 14A. However, the positional relationship between the position sensor 33 and the rotation angle sensor 50 is not limited to the content exemplified in the embodiment. For example, the sensor unit 30 of the modified example has any of the following (A) to (C) as the positional relationship between the position sensor 33 and the rotation angle sensor 50.
(A) The position sensor 33 is attached to the input shaft 14A, and the rotation angle sensor 50 is attached to the output shaft 14B.
(B) The position sensor 33 and the rotation angle sensor 50 are attached to the output shaft 14B.
(C) The position sensor 33 is attached to the output shaft 14B, and the rotation angle sensor 50 is attached to the input shaft 14A.

  In the configurations (A) and (B), the rotation angle sensor 50 detects the rotation angle of the output shaft 14B. In the configuration (C), the rotation angle sensor 50 detects the rotation angle of the input shaft 14A.

  -The movable component 31 of embodiment has the two 1st guide parts 31B. However, the number of the first guide portions 31B is not limited to the content exemplified in the embodiment. For example, the movable component 31 of the modification has one first guide portion 31B or three or more first guide portions 31B. In addition, the 2nd guide part 34 of a modification is formed so that it may become more than the number of the 1st guide parts 31B.

  -The 2nd guide part 34 of embodiment is formed as the space between the circumferential directions ZC of the two sliding components 32. As shown in FIG. However, the structure of the 2nd guide part 34 is not restricted to the content illustrated by embodiment. For example, the modified second guide portion 34 is formed as a recess that is recessed from the inner surface of the housing 40 in the radial direction ZB. The first guide portion 31 </ b> B of the modification is fitted into the recess of the housing 40.

In the sensor unit 30 of the embodiment, at least one of the two sliding parts 32 can be omitted.
In the electric motor 21 of the embodiment, a brushless motor is used. However, the configuration of the electric motor 21 is not limited to the content exemplified in the embodiment. For example, a motor with a brush is used in the modified electric motor 21. According to this configuration, since the motor with the brush is less expensive than the brushless motor, the cost of the EPS 1 is reduced.

  -EPS1 of embodiment has the structure of a rack cross type electric power steering apparatus. However, the configuration of the EPS 1 is not limited to the content exemplified in the embodiment. For example, the EPS 1 according to the modification has any of the configurations of a column assist type, a rack parallel type, a rack coaxial type, a pinion assist type, and a dual pinion assist type electric power steering device.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering component, 3 ... Wheel, 10 ... Steering device main body, 11 ... Steering shaft, 12 ... Column shaft, 13 ... Intermediate shaft, 14 ... Pinion shaft, 14A ... Input shaft, 14B ... Output shaft, 14C ... Torsion bar, 14D ... Screw part, 14E ... Projection, 15 ... Rack shaft, 15A ... Male screw part (screw part), 16 ... Ball screw mechanism, 16A ... Ball nut, 17 ... Tie rod, 20 ... Assist Device: 21 ... Electric motor, 22 ... First bevel tooth, 23 ... Second bevel tooth, 24 ... Hollow shaft, 30 ... Sensor unit, 31 ... Movable part, 31A ... Female thread portion, 31B ... First guide portion, 31C ... Outer side surface, 32 ... sliding component, 33 ... position sensor, 34 ... second guide portion, 35 ... ball bearing, 36 ... ball bearing DESCRIPTION OF SYMBOLS 40 ... Housing, 41 ... Internal space, 50 ... Rotation angle sensor, 51 ... Resolver rotor, 52 ... Resolver stator, 60 ... Torque sensor, 61 ... Magnet part, 62 ... Magnetic yoke part, 63 ... Magnetic collecting part, 70 ... Control 71, calculating unit, θ, steering angle, θ1, θ2, θ3, θ4, angle, τ, steering torque, S1, output value, S2, output value, ZA, axial direction, ZB, radial direction, ZC, circumference direction.

Claims (6)

A steering shaft that rotates integrally with the steering component;
A rotation angle sensor for detecting a rotation angle of the steering shaft;
A movable part that is screwed into a screw portion formed on an outer peripheral portion of the steering shaft and moves in the axial direction of the steering shaft according to the rotation of the steering shaft;
A position sensor for detecting the position of the movable part in the axial direction of the steering shaft;
An electric power steering apparatus comprising: a calculation unit that calculates an absolute steering angle based on a rotation angle of the steering shaft and a position of the movable part in an axial direction of the steering shaft. The calculation unit calculates a rotation position of the steering shaft based on a rotation angle of the steering shaft, calculates a rotation number of the steering shaft based on a position of the movable part in an axial direction of the steering shaft, The electric power steering apparatus according to claim 1, wherein the absolute steering angle is calculated based on a rotational position of a steering shaft and a rotational speed of the steering shaft. The electric power steering device according to claim 1, further comprising a guide portion that restricts rotational movement of the movable part.   The electric power steering apparatus according to any one of claims 1 to 3, wherein an assist force for assisting an operation of the steering component is applied based on the absolute steering angle. The electric power steering apparatus according to any one of claims 1 to 4, further comprising a sliding component that contacts an outer surface of the movable component and guides the movement of the movable component in an axial direction of the steering shaft. The steering shaft has an input shaft, an output shaft, and a torsion bar, and the input shaft and the output shaft are connected to each other by the torsion bar.
The rotation angle sensor detects one rotation angle of the input shaft and the output shaft,
The electric power steering apparatus according to any one of claims 1 to 5, wherein the movable part is attached to one of the input shaft and the output shaft.