Steering device

Abstract

A steering device 1 comprises a pinion gear 31 having a helical gear and a rack bar 40 having a plurality of helical rack teeth 41 that engage with the pinion gear 31. The rack teeth 41 have a wide pitch part 46 in which a plurality of rack teeth 41 are disposed at a predetermined pitch and a narrow pitch part 45 in which a plurality of rack teeth 41 are disposed at a narrower pitch than the pitch of the rack teeth 41 positioned in the wide pitch part 46. The rack teeth 41 positioned in the wide pitch part 46 have a tooth thickness constant in the tooth width direction W. The rack teeth 41 positioned in the narrow pitch part 45 each have, in one surface in the tooth thickness direction T, a tooth thickness change part 42 in which end portions in the tooth width direction W have a smaller tooth thickness than a tooth thickness of the center in the tooth width direction W. Thus,　change in the steering resistance during steering can be suppressed without reducing the rigidity of the rack bar 40.

Description

Steering device

[0001] The present disclosure relates to a steering device.

[0002] A steering device has a pinion gear that rotates due to the rotational torque generated when the steering wheel is steered, and a rack bar with rack teeth that mesh with the pinion gear. A steering device configured in this way transmits the rotational torque input from the steering wheel from the pinion gear to the rack bar, causing the rack bar to move linearly, thereby enabling the direction of the steered wheels to be changed in accordance with the steering angle of the steering wheel. Some conventional steering devices are equipped with a so-called variable gear ratio mechanism, in which the pitch of the rack teeth on the rack bar varies depending on the longitudinal position of the rack bar.

[0003] For example, in the steering device described in Patent Document 1, the meshing portion of the rack shaft, which is made up of a plurality of rack teeth, has a narrow-pitch portion and a wide-pitch portion where the pitch of the plurality of rack teeth is different. The steering device described in Patent Document 1, which has such a narrow-pitch portion and a wide-pitch portion, also includes a rack bushing that supports the rack shaft, and by making the sliding resistance between the rack shaft and the rack bushing when the pinion teeth mesh with the narrow-pitch portion smaller than the sliding resistance when the pinion teeth mesh with the wide-pitch portion, fluctuations in steering reaction force due to steering angle are suppressed.

[0004] Japanese Patent Application Laid-Open No. 2017-136905

[0005] In Patent Document 1, the diameter of the rack shaft is changed to change the sliding resistance between the rack shaft and the rack bush. That is, the portion of the rack shaft that comes into sliding contact with the rack bush when the pinion teeth mesh with the narrow pitch portion is a small diameter portion, and the portion that comes into sliding contact with the rack bush when the pinion teeth mesh with the wide pitch portion is a large diameter portion. As a result, when the pinion teeth mesh with the narrow pitch portion, the small diameter portion comes into sliding contact with the rack bush, which reduces the sliding resistance compared to when the large diameter portion comes into sliding contact with the rack bush when the pinion teeth mesh with the wide pitch portion.

[0006] However, if the diameter of the rack bar is reduced, the support rigidity of the rack bar decreases, which may lead to a decrease in rigidity during steering and a decrease in steering feel.For this reason, in a steering device including a rack bar having a plurality of rack tooth pitches, there is room for improvement in terms of ensuring the rigidity of the rack bar in suppressing fluctuations in steering resistance, which is resistance to steering such as sliding resistance that fluctuates with fluctuations in pitch.

[0007] The present disclosure has been made in consideration of the above, and aims to provide a steering device that can suppress changes in steering resistance during steering without reducing the rigidity of the rack bar.

[0008] The steering device of the present disclosure includes a pinion gear having a helical gear, and a rack bar having a plurality of helical rack teeth that mesh with the pinion gear, the rack teeth having a wide pitch portion where the plurality of rack teeth are arranged at a predetermined pitch, and a narrow pitch portion where the pitch of the plurality of rack teeth is narrower than the pitch between the rack teeth located in the wide pitch portion, the rack teeth located in the wide pitch portion have a constant tooth thickness in the tooth width direction, and the rack teeth located in the narrow pitch portion have a tooth thickness changing portion on one surface in the tooth thickness direction where the tooth thickness at the end in the tooth width direction is smaller than the tooth thickness at the center in the tooth width direction.

[0009] According to this configuration, the rack teeth located in the narrow pitch portion have the tooth thickness change portion 42, which makes it difficult for the rotating pinion gear to come into contact with the rack teeth located in the narrow pitch portion near the ends of the rack teeth in the tooth width direction. Therefore, the rack teeth located in the narrow pitch portion can offset the ease of contact with the pinion gear due to the narrow pitch and the difficulty of contact with the pinion gear near the ends of the rack teeth in the tooth width direction. This reduces the difference between the maximum and minimum numbers of rack teeth that simultaneously come into contact with the pinion gear. By partially reducing the diameter of the rack bar, the fluctuation in steering resistance during steering can be reduced without changing the sliding resistance between the rack bar and the rack bushing. As a result, changes in steering resistance during steering can be suppressed without reducing the rigidity of the rack bar.

[0010] The steering device of the present disclosure includes a pinion gear having a helical gear, and a rack bar having a plurality of helical rack teeth that mesh with the pinion gear, the rack teeth having a wide pitch portion where the plurality of rack teeth are arranged at a predetermined pitch, and a narrow pitch portion where the pitch of the plurality of rack teeth is narrower than the pitch between the rack teeth located in the wide pitch portion, the rack teeth located in the wide pitch portion have a tooth thickness changing portion on one surface in the tooth thickness direction where the tooth thickness of an end portion in the tooth width direction is smaller than the tooth thickness at a center in the tooth width direction, and the rack teeth located in the narrow pitch portion have the tooth thickness changing portion on both surfaces in the tooth thickness direction.

[0011] According to this configuration, a tooth thickness change portion is formed on one side of the rack teeth located in the wide-pitch portion, and a tooth thickness change portion is formed on both sides of the rack teeth located in the narrow-pitch portion, thereby making it possible to reduce the difference between the maximum and minimum numbers of rack teeth that simultaneously contact the pinion gear. This reduces the diameter of the rack bar in parts, thereby reducing the fluctuation in steering resistance during steering without changing the sliding resistance between the rack bar and the rack bushing. As a result, it is possible to suppress changes in steering resistance during steering without reducing the rigidity of the rack bar 40.

[0012] In a preferred embodiment, the tooth thickness varying portion is a crowning in which the tooth thickness is greatest at the center in the tooth width direction and decreases toward the end in the tooth width direction.

[0013] According to this configuration, because the tooth thickness changing portion is crowned, when the rotating pinion gear comes into contact with the rack teeth located in the narrow pitch portion, it is possible to make it difficult for the pinion gear to come into contact with the rack teeth located in the narrow pitch portion near the ends in the tooth width direction. This allows the rack teeth located in the narrow pitch portion to offset the ease of contact with the pinion gear due to the narrow pitch and the difficulty of contact with the pinion gear near the ends in the tooth width direction due to the crowning. This reduces the difference between the maximum and minimum numbers of rack teeth that simultaneously come into contact with the pinion gear, thereby reducing fluctuations in steering resistance during steering. As a result, changes in steering resistance during steering can be suppressed without reducing the rigidity of the rack bar.

[0014] In a preferred embodiment, the narrow pitch sections are arranged at the center and both ends of the range in the longitudinal direction of the rack bar in which the plurality of rack teeth are arranged, and the wide pitch sections are arranged between the narrow pitch sections at the center and both ends in the longitudinal direction of the rack bar.

[0015] According to this configuration, the narrow-pitch sections are located at the center and both ends of the range in which the rack teeth are arranged, ensuring a steering feel when driving near straight ahead by the narrow-pitch section in the center, and reducing stress on the rack teeth near the maximum steering angle by the narrow-pitch sections at both ends, ensuring durability. Furthermore, the wide-pitch sections are located between the narrow-pitch sections at the center and both ends in the longitudinal direction of the rack bar, so the wide-pitch sections can increase responsiveness to steering at steering angles between straight ahead driving and the maximum steering angle, ensuring a steering feel when steering at steering angles larger than when driving straight ahead. As a result, it is possible to improve both the steering feel when the vehicle is driving and the durability of the rack bar.

[0016] In a preferred embodiment, the narrow pitch portion is positioned at the center of the range in the longitudinal direction of the rack bar in which the plurality of rack teeth are arranged, and the wide pitch portion is positioned on both sides of the narrow pitch portion in the longitudinal direction of the rack bar.

[0017] With this configuration, the narrow pitch portion is located in the center of the range in which the rack teeth are arranged, and the wide pitch portions are located on both ends of the narrow pitch portion, thereby improving responsiveness when steering at large steering angles, and as a result, improving the steering feel.

[0018] In a preferred embodiment, the number of the rack teeth that simultaneously contact the pinion gear is within the range of two to four.

[0019] With this configuration, the number of rack teeth that simultaneously contact the pinion gear is two or more, thereby suppressing slapping noise and improving steering feel. Also, because the number of rack teeth that simultaneously contact the pinion gear is four or less, the difference between the maximum and minimum numbers of rack teeth that simultaneously contact the pinion gear can be reduced, thereby reducing fluctuations in steering resistance during steering. As a result, changes in steering resistance during steering are suppressed, slapping noise is suppressed, and steering feel is improved.

[0020] The steering device according to the present disclosure has the advantage of being able to suppress changes in steering resistance during steering without reducing the rigidity of the rack bar.

[0021] FIG. 1 is a schematic diagram of a steering device according to an embodiment. FIG. 2 is a front view of a plurality of rack teeth on the rack bar shown in FIG. 1. FIG. 3 is a detailed view of rack teeth arranged in the wide-pitch portion shown in FIG. 2. FIG. 4 is a detailed view of rack teeth arranged in the narrow-pitch portion shown in FIG. 2. FIG. 5 is an explanatory diagram illustrating the transition of the number of rack teeth simultaneously contacting the pinion gear when the rack teeth of a rack bar that is not crowned contacts the rotating pinion gear. FIG. 6 is an explanatory diagram illustrating the transition of the number of rack teeth simultaneously contacting the pinion gear when the rack teeth of a rack bar that is crowned on both sides contacts the rotating pinion gear. FIG. 7 is an explanatory diagram illustrating the transition of the number of rack teeth simultaneously contacting the pinion gear when the rack teeth of a rack bar that is crowned on one side of the rack teeth located in the narrow-pitch portion contacts the rotating pinion gear. FIG. 8 is an explanatory diagram illustrating a state in which two rack teeth are in contact with the pinion gear. Fig. 9 is a schematic diagram showing a modified example of the steering device according to the embodiment, in which a narrow pitch portion is arranged in the center of the rack tooth arrangement range. Fig. 10 is an explanatory diagram showing a modified example of the steering device according to the embodiment, in which a tooth thickness changing portion is formed on one side of the rack tooth arranged in the wide pitch portion. Fig. 11 is an explanatory diagram showing a modified example of the steering device according to the embodiment, in which a tooth thickness changing portion is formed on both sides of the rack tooth arranged in the narrow pitch portion.

[0022] The present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the following modes for carrying out the invention (hereinafter referred to as embodiments). Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0023] [Embodiment] Fig. 1 is a schematic diagram of a steering device 1 according to an embodiment. In the drawing, the upper side (one side in the axial direction) is indicated by D1, and the lower side (the other side in the axial direction) is indicated by D2. In addition, in the description of the embodiment, the upper side (one side in the axial direction) may be referred to as the D1 side, and the lower side (the other side in the axial direction) may be referred to as the D2 side.

[0024] As shown in FIG. 1, the steering device 1 includes a steering wheel 20, a first steering shaft 21, a second steering shaft 22, a pinion shaft 30, a rack bar 40, a worm reducer 50, a tie rod 60, a rack housing 10, an ECU 80, and a power supply unit 85.

[0025] The first steering shaft 21 is connected to the steering wheel 20. The first steering shaft 21 is rotatably supported. The first steering shaft 21 rotates due to the torque that steers the steering wheel 20. Specifically, when the driver grips and rotates the steering wheel 20, the rotational torque (steering torque) is transmitted to the first steering shaft 21, causing the first steering shaft 21 to rotate.

[0026] The second steering shaft 22 is connected to the first steering shaft 21 via a first universal joint 26. The second steering shaft 22 is rotatably supported. The rotational torque of the first steering shaft 21 is transmitted to the second steering shaft 22 via the first universal joint 26, causing the second steering shaft 22 to rotate.

[0027] The rack housing 10 is formed in a cylindrical shape and includes a pinion housing 11 and a reducer housing 12 .

[0028] As shown in FIG. 1 , the pinion shaft 30 is connected to the second steering shaft 22 via the second universal joint 27. The rotational torque of the second steering shaft 22 is transmitted to the pinion shaft 30 via the second universal joint 27, causing the pinion shaft 30 to rotate. A pinion gear 31 is provided on the pinion shaft 30. The pinion gear 31 has a helical gear 31a (see FIG. 8 ). That is, the pinion gear 31 is a so-called helical gear. The pinion shaft 30 is rotatably supported on the pinion housing 11 via a first bearing 24 and a second bearing 25. The first bearing 24 supports an upper portion of the pinion shaft 30. The second bearing 25 supports a lower portion of the pinion shaft 30. Specifically, the first bearing 24 is provided on a cylindrical surface 32 on the upper side (D1 side, one axial side) of the pinion gear 31.

[0029] A rack bar 40 is housed inside the rack housing 10. The rack bar 40 is formed in an axial shape extending in a predetermined direction, and is disposed with its longitudinal direction oriented in the vehicle width direction. The rack bar 40 has a plurality of rack teeth 41 on its surface at predetermined positions in the longitudinal direction of the rack bar 40. The plurality of rack teeth 41 are each helical and are formed side by side in the longitudinal direction of the rack bar 40, and mesh with the pinion gear 31 of the pinion shaft 30.

[0030] The tie rods 60 are disposed on both sides of the rack bar 40 in the longitudinal direction, and are respectively connected to the rack bar 40. Furthermore, the tie rods 60 are connected to wheels 65 at the portions opposite to the portions of the tie rods 60 connected to the rack bar 40. Therefore, when the pinion shaft 30 rotates, a force in the longitudinal direction of the rack bar 40 is transmitted to the rack teeth 41 that mesh with the pinion gear 31, and the rack bar 40 moves in the longitudinal direction, i.e., the rack bar 40 moves in the vehicle width direction. This causes the tie rods 60 to move in the vehicle width direction, which changes the orientation of the wheels 65 and alters the direction of travel of the vehicle.

[0031] The rack housing 10 is formed in a cylindrical shape, and is disposed such that the axial direction of the cylinder is aligned with the longitudinal direction of the rack bar 40. The rack housing 10 formed in this cylindrical shape stores the rack bar 40 inside. The pinion housing 11 and the reducer housing 12 are disposed integrally with the rack housing 10.

[0032] The worm reducer 50 includes a worm shaft 52 and a worm wheel 51. The worm shaft 52 and the worm wheel 51 are housed inside the reducer housing 12. The worm shaft 52 is provided on the output shaft of the electric motor 53. The worm shaft 52 meshes with the worm wheel 51. The worm wheel 51 is fixed to the lower end of the pinion shaft 30. Therefore, when the electric motor 53 is operated, the worm shaft 52 rotates, and the worm wheel 51 meshing with the worm shaft 52 rotates together with the pinion shaft 30. This allows the electric motor 53 to apply auxiliary steering torque to the pinion shaft 30, thereby reducing the force required to steer the steering wheel 20.

[0033] The ECU 80 is connected to a power supply device 85 (e.g., an on-board battery), and power is supplied from the power supply device 85 to the ECU 80. The ECU 80 controls the operation of the electric motor 53. The ECU 80 acquires signals from a torque sensor (not shown) and a vehicle speed sensor (not shown). The ECU 80 calculates an auxiliary steering command value based on the steering torque and the vehicle speed. The ECU 80 adjusts the value of power supplied to the electric motor 53 based on the auxiliary steering command value. The ECU 80 acquires information on the induced voltage from the electric motor 53 or information output from a resolver or the like provided in the electric motor 53. By the ECU 80 controlling the operation of the electric motor 53, as described above, the electric motor 53 can apply an auxiliary steering torque to the pinion shaft 30, thereby reducing the force required to steer the steering wheel 20.

[0034] As shown in Fig. 1, the steering device 1 according to the embodiment is a single-pinion electric power steering device in which an assist force is applied to the pinion shaft 30, but the steering device 1 is not limited to this. The steering device 1 may be, for example, a column-assist electric power steering device in which an assist force is applied to the first steering shaft 21, or a dual-pinion electric power steering device that includes a second pinion gear (not shown) that meshes with the rack bar 40 at a position different from the pinion gear 31 and in which an assist force is applied to the second pinion gear. Alternatively, the steering device 1 may be a rack-assist electric power steering device that applies an assist force to the rack bar 40 without using a pinion gear, such as a ball screw type that applies an assist force to the rack bar 40 by a ball screw.

[0035] Fig. 2 is a front view of a plurality of rack teeth 41 of the rack bar 40 shown in Fig. 1. The rack teeth 41 of the rack bar 40 are arranged side by side in the longitudinal direction of the rack bar 40. Furthermore, because the rack teeth 41 are formed as helices, each rack tooth 41 is formed at an angle with respect to the longitudinal direction of the rack bar 40. In this way, the plurality of rack teeth 41 arranged on the rack bar 40 are arranged at multiple pitches between the rack teeth 41 in the longitudinal direction of the rack bar 40.

[0036] More specifically, the rack teeth 41 have a wide pitch portion 46 where the plurality of rack teeth 41 are arranged at a predetermined pitch, and a narrow pitch portion 45 where the pitch between the plurality of rack teeth 41 is narrower than the pitch between the rack teeth 41 located in the wide pitch portion 46. That is, the pitch between the rack teeth 41 located in the wide pitch portion 46 and the rack teeth 41 located in the narrow pitch portion 45 is relatively different, and the pitch between the plurality of rack teeth 41 located in the wide pitch portion 46 is wider than the pitch between the rack teeth 41 located in the narrow pitch portion 45.

[0037] In this embodiment, the narrow pitch portions 45 are arranged at three locations in the rack tooth arrangement range 44, which is a range in which a plurality of rack teeth 41 are arranged in the longitudinal direction of the rack bar 40: the center and both ends in the longitudinal direction of the rack bar 40. The wide pitch portions 46 are arranged at two locations between the narrow pitch portions 45: the central narrow pitch portion 45 in the rack tooth arrangement range 44 and the narrow pitch portions 45 at both ends. The narrow pitch portions 45 are arranged, for example, in a range of about ±10 mm from the center of the rack tooth arrangement range 44 in the longitudinal direction of the rack bar 40, and in a range of about 10 mm from the ends of the rack tooth arrangement range 44. Note that the boundary between the narrow pitch portion 45 and the wide pitch portion 46 may have a transition region where the pitch of the rack teeth 41 gradually increases or decreases. If the narrow pitch section 45 includes a transition region where the pitch gradually increases or decreases, the narrow pitch section 45 is arranged in a range of approximately ±25 mm centered on the center of the rack tooth arrangement range 44 and in a range of approximately 25 mm from the end of the rack tooth arrangement range 44.

[0038] 3 is a detailed view of the rack teeth 41 arranged in the wide pitch portion 46 shown in FIG. The rack teeth 41 of the rack bar 40 have a tooth thickness that decreases from the base end side of the rack tooth 41 toward the tip end side. The rack teeth 41 located in the wide pitch portion 46 have a constant tooth thickness in the tooth width direction W, which is the direction in which the rack teeth 41 extend. That is, the rack teeth 41 located in the wide pitch portion 46 have flat portions 41a on both sides in the tooth thickness direction T that are formed substantially flat along the tooth width direction W. Therefore, the rack teeth 41 located in the wide pitch portion 46 have the same tooth thickness in the tooth thickness direction T at portions that are the same height from the base end, regardless of the position in the tooth width direction W.

[0039] 4 is a detailed view of a rack tooth 41 arranged in the narrow pitch portion 45 shown in FIG. The rack tooth 41 located in the narrow pitch portion 45 has, on one surface in the tooth thickness direction T, a tooth thickness changing portion 42 in which the tooth thickness at the end in the tooth width direction W is smaller than the tooth thickness at the center in the tooth width direction W. In this embodiment, the tooth thickness changing portion 42 is formed by a so-called crowning 43 in which the tooth thickness is greatest at the center in the tooth width direction W and decreases toward the end in the tooth width direction W. Therefore, the rack tooth 41 located in the narrow pitch portion 45 has, on one surface in the tooth thickness direction T, a curved shape in which the tooth thickness decreases from the center in the tooth width direction W toward both end portions in the tooth width direction W.

[0040] On the other hand, the rack tooth 41 located in the narrow pitch portion 45 does not have the tooth thickness changing portion 42 formed on the surface opposite to the surface having the tooth thickness changing portion 42, i.e., the crowning 43 is not formed. In other words, the surface of the rack tooth 41 located in the narrow pitch portion 45 on the side not having the crowning 43 is a flat portion 41a formed substantially flat along the tooth width direction W. For this reason, the flat portion 41a, which is the surface opposite to the surface having the tooth thickness changing portion 42 of the rack tooth 41 located in the narrow pitch portion 45, is formed to extend linearly in the tooth width direction W between portions having the same height from the base end side.

[0041] The crowning 43 on one surface in the tooth thickness direction T of the rack tooth 41 located in the narrow pitch portion 45 is provided on the surface on the same side in the longitudinal direction of the rack bar 40 as the plurality of rack teeth 41 located in the narrow pitch portion 45. In other words, the crowning 43 is provided on the surface on the same side in the longitudinal direction of the rack bar 40 as the plurality of rack teeth 41 located in the narrow pitch portion 45 at the center of the rack tooth arrangement range 44 and the plurality of rack teeth 41 located in the narrow pitch portions 45 at both ends.

[0042] Next, a description will be given of the operation of the steering device 1. When the steering wheel 20 is operated while driving a vehicle equipped with the steering device 1, the steering force applied to the steering wheel 20 is transmitted from the steering wheel 20 to the first steering shaft 21. The steering force transmitted to the first steering shaft 21 is transmitted as steering torque from the first steering shaft 21 to the second steering shaft 22, and from the second steering shaft 22 to the pinion shaft 30.

[0043] The pinion shaft 30 has a pinion gear 31 that meshes with rack teeth 41 of the rack bar 40, and steering torque transmitted to the pinion shaft 30 is transmitted to the rack bar 40 by the pinion gear 31 of the pinion shaft 30 and the rack teeth 41 of the rack bar 40. The rack bar 40, to which the steering torque is transmitted from the pinion shaft 30, moves in the longitudinal direction of the rack bar 40, which is the direction in which the multiple rack teeth 41 are aligned. In this way, the rack bar 40 converts the steering torque transmitted from the pinion shaft 30 into linear motion in the longitudinal direction of the rack bar 40. In other words, the rack bar 40 moves in the vehicle width direction, which is the longitudinal direction of the rack bar 40 disposed on the vehicle.

[0044] Since tie rods 60 are connected to both ends of the rack bar 40, the tie rods 60 connected to the rack bar 40 also move as the rack bar 40 moves in the vehicle width direction. Since the tie rods 60 are connected to the wheels 65, the movement of the tie rods 60 changes the orientation of the wheels 65. As a result, the direction of travel of the vehicle on which the steering device 1 is installed changes in response to the operation of the steering wheel 20.

[0045] The steering device 1 according to this embodiment also includes an electric motor 53 that generates an auxiliary steering torque to assist the driver in steering. The electric motor 53 generates the auxiliary steering torque based on the steering torque detected by a torque sensor (not shown). That is, the steering torque detected by the torque sensor is transmitted as an electric signal to the ECU 80, and the ECU 80 operates the electric motor 53 based on the electric signal transmitted from the torque sensor, thereby causing the electric motor 53 to generate the auxiliary steering torque. The auxiliary steering torque generated by the electric motor 53 is transmitted to the pinion shaft 30 via the worm reduction gear 50.

[0046] In other words, the auxiliary steering torque generated by the electric motor 53 is transmitted from the worm shaft 52 attached to the output shaft of the electric motor 53 to the worm wheel 51 attached to the pinion shaft 30 and meshing with the worm shaft 52, and then transmitted to the pinion shaft 30 via the worm wheel 51. In this way, the electric motor 53 assists the rotation of the pinion shaft 30, which is rotated by the steering torque, with the auxiliary steering torque generated by the electric motor 53. Therefore, the steering force applied by the driver to the steering wheel 20 is assisted by the auxiliary steering torque generated by the electric motor 53, and the force required to steer the steering wheel 20 is reduced by the auxiliary steering torque generated by the electric motor 53 being transmitted to the pinion shaft 30.

[0047] Furthermore, the rack teeth 41 of the rack bar 40 have narrow pitch portions 45 and wide pitch portions 46, and the narrow pitch portions 45 are located at the center and both ends of the rack tooth arrangement range 44. In other words, the narrow pitch portions 45 are located near the center and both ends of the rotation range of the steering wheel 20, which rotates the pinion gear 31 that meshes with the rack teeth 41. Therefore, the rack teeth 41 located in the narrow pitch portions 45 mesh with the pinion gear 31 when the vehicle is traveling straight and at the maximum steering angle.

[0048] When the vehicle is traveling straight, the steering wheel 20 is not rotated significantly, but is rotated slightly depending on the road direction and road surface conditions, or when changing lanes. When traveling straight, the pinion gear 31 meshes with the rack teeth 41 of the narrow pitch portion 45, so the amount of movement of the rack bar 40 in the longitudinal direction relative to the rotation of the steering wheel 20, i.e., the rotation of the pinion gear 31, is small. Therefore, when traveling straight, the amount of change in the direction of the wheels 65 relative to the rotation of the steering wheel 20 is small, making it easier to make fine adjustments to the steering, and ensuring a steering feel when traveling straight.

[0049] Furthermore, near the maximum steering angle while the vehicle is traveling, the orientation of the wheels 65 changes significantly from the orientation when traveling straight, so when the vehicle is traveling in this state, a large force acts from the road surface on the steered wheels 65 in a direction returning the orientation of the wheels 65 to the orientation when traveling straight. The large force in the direction returning the orientation of the wheels 65 to the orientation when traveling straight is transmitted from the wheels 65 via the tie rod 60 to the rack bar 40, and then transmitted from the rack teeth 41 to the pinion gear 31.

[0050] For this reason, a large force acts between the rack teeth 41 and the pinion gear 31 near the maximum steering angle when the vehicle is traveling, but the rack teeth 41 arranged on the rack bar 40 that mesh with the pinion gear 31 near the maximum steering angle are the rack teeth 41 located in the narrow pitch portion 45. In this way, near the maximum steering angle, the rack teeth 41 located in the narrow pitch portion 45 mesh with the pinion gear 31, so the number of rack teeth 41 that simultaneously contact the pinion gear 31 is greater than when the rack teeth 41 located in the wide pitch portion 46 mesh with the pinion gear 31.

[0051] As a result, near the maximum steering angle, the large force acting between the rack teeth 41 and the pinion gear 31 can be borne by a greater number of rack teeth 41 than when the rack teeth 41 located in the wide pitch portion 46 mesh with the pinion gear 31. Therefore, it is possible to reduce the stress on the rack teeth 41 near the maximum steering angle when a large force acts between the rack teeth 41 and the pinion gear 31, and to ensure durability.

[0052] Furthermore, when the vehicle is traveling, at steering angles between straight traveling and the maximum steering angle, the pinion gear 31 meshes with the rack teeth 41 located in the wide pitch portion 46. In the wide pitch portion 46, the pitch of the rack teeth 41 is wider than the pitch of the rack teeth 41 in the narrow pitch portion 45, so the amount of movement of the rack bar 40 in the longitudinal direction with respect to the rotation of the steering wheel 20, i.e., the rotation of the pinion gear 31, is greater than when the pinion gear 31 meshes with the rack teeth 41 located in the narrow pitch portion 45. Therefore, at steering angles between straight traveling and the maximum steering angle with the vehicle traveling, the amount of change in the direction of the wheels 65 with respect to the rotation of the steering wheel 20 is greater, so that steering responsiveness can be improved and a steering feeling can be ensured when steering at steering angles greater than when traveling straight.

[0053] Furthermore, when the rack teeth 41 located in the wide pitch portion 46 mesh with the pinion gear 31, the number of rack teeth 41 that simultaneously contact the pinion gear 31 is smaller than when the rack teeth 41 located in the narrow pitch portion 45 mesh with the pinion gear 31, but at steering angles smaller than near the maximum steering angle, the force acting between the rack teeth 41 and the pinion gear 31 is smaller than the force at the maximum steering angle. Therefore, at steering angles smaller than near the maximum steering angle, even if the number of rack teeth 41 that simultaneously contact the pinion gear 31 is smaller, the stress on the rack teeth 41 is less likely to increase, and durability is ensured.

[0054] Furthermore, in this embodiment, the rack teeth 41 located in the wide pitch portion 46 do not have crownings 43, and the rack teeth 41 located in the narrow pitch portion 45 have crownings 43 on one surface in the tooth thickness direction T. Therefore, when the pinion gear 31 and the rack teeth 41 are in mesh with each other, the number of the rack teeth 41 that simultaneously contact the pinion gear 31 can be made as uniform as possible across the entire rack tooth arrangement range 44. In other words, when the pinion gear 31 and the rack teeth 41 are in mesh with each other, the difference between the maximum number and the minimum number of the rack teeth 41 that simultaneously contact the pinion gear 31 can be made as small as possible.

[0055] That is, because the pinion gear 31 has a helical gear 31a (see FIG. 8) and the rack teeth 41 are also helical, when the gear 31a of the pinion gear 31 and the rack teeth 41 come into contact with each other, the contact occurs gradually from a position near the end in the direction in which the gear 31a and the rack teeth 41 are formed. For example, the rack teeth 41 gradually come into contact with the gear 31a of the pinion gear 31 from a position near the end in the tooth width direction W, and the contact position changes in the tooth width direction W as the pinion gear 31 rotates.

[0056] Furthermore, the pitch between the rack teeth 41 located in the narrow pitch portion 45 is narrower than that between the rack teeth 41 located in the wide pitch portion 46. Therefore, when the gear 31 a of the pinion gear 31 comes into contact with the rack teeth 41 as the pinion gear 31 rotates, the gear 31 a of the pinion gear 31 is more likely to come into contact with the rack teeth 41 when the pinion gear 31 is located in the narrow pitch portion 45 than when the pinion gear 31 is located in the wide pitch portion 46.

[0057] Here, the rack teeth 41 located in the narrow pitch portion 45 have the crowning 43 formed on one surface in the tooth thickness direction T, so the pinion gear 31 is less likely to come into contact with the end portion in the tooth width direction W of the surface of the rack teeth 41 located in the narrow pitch portion 45 on which the crowning 43 is formed. Also, when the pinion gear 31, which is in contact with the side of the rack teeth 41 located in the narrow pitch portion 45 on which the crowning 43 is formed, moves away from the rack teeth 41 as the pinion gear 31 rotates, it is more likely to move away from the end portion in the tooth width direction W.

[0058] For this reason, the rack teeth 41 located in the narrow pitch portion 45 have an ease of contact with the pinion gear 31 due to the narrow pitch, which offsets the difficulty of contact with the pinion gear 31 near the end in the tooth width direction W of the surface of the rack tooth 41 on which the crowning 43 is formed. As a result, the rack teeth 41 located in the narrow pitch portion 45 and the rack teeth 41 located in the wide pitch portion 46 of the multiple rack teeth 41 arranged on the rack bar 40 have similar ease of contact with the rotating pinion gear 31.

[0059] Therefore, in this embodiment, when the rotating pinion gear 31 and the rack teeth 41 mesh, the difference between the maximum and minimum numbers of the rack teeth 41 that simultaneously contact the pinion gear 31 is small throughout the entire rack tooth arrangement range 44.

[0060] Next, a description will be given of the transition in the number of teeth that simultaneously contact the rack teeth 41 of the rack bar 40 and the pinion gear 31 as the pinion gear 31 rotates. Fig. 5 is an explanatory diagram illustrating the transition in the number of teeth of the rack teeth 41 that simultaneously contact the pinion gear 31 when the rack teeth 41 of the rack bar 40 that is not provided with a crowning 43 come into contact with the rotating pinion gear 31. Fig. 5 is an explanatory diagram showing an example of the transition in the number of teeth of the rack teeth 41 that simultaneously contact the pinion gear 31 as the contact portion between the rack teeth 41 of the rack bar 40 that is not provided with a crowning 43 and the pinion gear 31 moves from one end to the other end of the rack tooth arrangement range 44. Note that Fig. 5 and Figs. 6 and 7, which will be described later, are explanatory diagrams of an embodiment in which a transition region 47, where the pitch of the rack teeth 41 changes between the narrow pitch portion 45 and the wide pitch portion 46 of the rack bar 40, is provided.

[0061] 5 , when the rack teeth 41 located in the narrow pitch portion 45 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between three and five by rotating the pinion gear 31. On the other hand, when the rack teeth 41 located in the wide pitch portion 46 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between two and three by rotating the pinion gear 31. Furthermore, when the rack teeth 41 located in the transition region 47 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between three and four by rotating the pinion gear 31. Therefore, in the example shown in FIG. 5, the number of rack teeth 41 that simultaneously contact the pinion gear 31 varies between two and five depending on the position at which the pinion gear 31 and the rack teeth 41 contact each other.

[0062] 6 is an explanatory diagram showing a transition in the number of rack teeth 41 simultaneously contacting the pinion gear 31 when the rack teeth 41 of the rack bar 40, which has crownings 43 on both sides of the rack teeth 41, come into contact with the rotating pinion gear 31. Fig. 6 is an explanatory diagram showing an example of a transition in the number of rack teeth 41 simultaneously contacting the pinion gear 31 when the contact portion between the rack teeth 41 of the rack bar 40, which has crownings 43 on both sides of the rack teeth 41, and the pinion gear 31 moves from one end side to the other end side of the rack tooth arrangement range 44.

[0063] 6 , when the rack teeth 41 located in the narrow pitch portion 45 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between two and four by rotating the pinion gear 31. On the other hand, when the rack teeth 41 located in the wide pitch portion 46 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between one and two by rotating the pinion gear 31. Furthermore, when the rack teeth 41 located in the transition region 47 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between one and three by rotating the pinion gear 31. Therefore, in the example shown in FIG. 6, the number of rack teeth 41 that simultaneously contact the pinion gear 31 varies between one and four depending on the position at which the pinion gear 31 and the rack teeth 41 contact each other.

[0064] 7 is an explanatory diagram showing a transition in the number of rack teeth 41 that simultaneously contact the pinion gear 31 when the rack teeth 41 of a rack bar 40, in which the crowning 43 is provided on one side of the rack teeth 41 located in the narrow pitch portion 45, come into contact with the rotating pinion gear 31. Fig. 7 is an explanatory diagram showing an example of a transition in the number of rack teeth 41 that simultaneously contact the pinion gear 31 when the contact portion between the rack teeth 41 of the rack bar 40, in which the crowning 43 is provided on one side of the rack teeth 41 located in the narrow pitch portion 45, and the pinion gear 31 moves from one end side to the other end side of the rack tooth arrangement range 44.

[0065] 7 , when the rack teeth 41 located in the narrow pitch portion 45 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between three and four by rotating the pinion gear 31. On the other hand, when the rack teeth 41 located in the wide pitch portion 46 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between two and three by rotating the pinion gear 31. Also, when the rack teeth 41 located in the transition region 47 are in contact with the pinion gear 31, the number of teeth of the rack teeth 41 that are in simultaneous contact with the pinion gear 31 varies between two and three by rotating the pinion gear 31. Therefore, in the example shown in FIG. 7, the number of rack teeth 41 that simultaneously contact the pinion gear 31 varies between two and four depending on the position at which the pinion gear 31 and the rack teeth 41 contact each other.

[0066] 5, 6, and 7, when the crowning 43 is provided on one side of the rack teeth 41 located in the narrow pitch portion 45, the difference between the maximum and minimum numbers of the rack teeth 41 that simultaneously contact the pinion gear 31 is smaller than when the rack teeth 41 are not crowned 43 or when the rack teeth 41 are crowned 43 on both sides. Therefore, when the crowning 43 is provided on one side of the rack teeth 41 located in the narrow pitch portion 45, the fluctuation in steering resistance during steering can be reduced more than when the rack teeth 41 are not crowned 43 or when the rack teeth 41 are crowned 43 on both sides.

[0067] 5 and 7, when the crowning 43 is provided on one side of the rack teeth 41 located in the narrow pitch portion 45, the maximum number of rack teeth 41 that simultaneously contact the pinion gear 31 is smaller than when the rack teeth 41 are not provided with the crowning 43. Therefore, when the crowning 43 is provided on one side of the rack teeth 41 located in the narrow pitch portion 45, the steering resistance during steering can be made smaller than when the rack teeth 41 are not provided with the crowning 43.

[0068] As described above, in the steering device 1 according to the embodiment, the rack teeth 41 of the rack bar 40 have the wide-pitch portion 46 and the narrow-pitch portion 45, and the rack teeth 41 located in the narrow-pitch portion 45 have, on one surface in the tooth thickness direction T, the tooth thickness changing portion 42 in which the tooth thickness at the end in the tooth width direction W is smaller than the tooth thickness at the center in the tooth width direction W. This makes it possible to make it difficult for the rotating pinion gear 31 to come into contact with the rack teeth 41 located in the narrow-pitch portion 45 near the end of the rack tooth 41 in the tooth width direction W. Therefore, the rack teeth 41 located in the narrow-pitch portion 45 can offset the ease of contact with the pinion gear 31 due to the narrow pitch with the difficulty of contact with the pinion gear 31 near the end of the rack tooth 41 in the tooth width direction W. Therefore, the difference between the maximum number and the minimum number of rack teeth 41 that simultaneously contact the pinion gear 31 can be reduced across the entire rack tooth arrangement range 44, and fluctuations in steering resistance during steering can be reduced without changing the sliding resistance between the rack bar 40 and a rack bush (not shown) by partially reducing the diameter of the rack bar 40 as in Patent Document 1. As a result, changes in steering resistance during steering can be suppressed without reducing the rigidity of the rack bar 40.

[0069] Furthermore, the tooth thickness changing portion 42 of the rack teeth 41 located in the narrow pitch portion 45 has a crowning 43 in which the tooth thickness decreases from the center to the ends in the tooth width direction W of the rack teeth 41. This makes it difficult for the rotating pinion gear 31 to come into contact with the rack teeth 41 located in the narrow pitch portion 45 near the ends in the tooth width direction W. As a result, the rack teeth 41 located in the narrow pitch portion 45 can offset the ease of contact with the pinion gear 31 due to the narrow pitch and the difficulty of contact with the pinion gear 31 near the ends in the tooth width direction W of the rack teeth 41 due to the crowning 43. Therefore, the difference between the maximum and minimum numbers of the rack teeth 41 that simultaneously come into contact with the pinion gear 31 can be reduced, thereby reducing fluctuations in steering resistance during steering. As a result, changes in steering resistance during steering can be suppressed without reducing the rigidity of the rack bar 40.

[0070] Furthermore, because the narrow pitch portions 45 are arranged at the center and both ends of the rack tooth arrangement range 44, the central narrow pitch portion 45 ensures a steering feel when traveling near straight ahead, and the narrow pitch portions 45 at both ends reduce stress on the rack teeth 41 when the steering angle is near the maximum steering angle, ensuring durability. Furthermore, because the wide pitch portions 46 are arranged between the narrow pitch portions 45 at the center and both ends in the longitudinal direction of the rack bar 40, the wide pitch portions 46 can increase responsiveness to steering at steering angles between straight ahead and the maximum steering angle, ensuring a steering feel when steering at steering angles larger than when traveling straight ahead. As a result, it is possible to improve both the steering feel when the vehicle is traveling and the durability of the rack bar 40.

[0071] Furthermore, since the number of rack teeth 41 that simultaneously contact the pinion gear 31 is within the range of two to four, it is possible to suppress changes in steering resistance during steering and to suppress slapping noise, and further to improve the steering feel. In other words, by having two or more teeth that simultaneously contact the pinion gear 31, it is possible to suppress slapping noise and improve the steering feel.

[0072] 8 is an explanatory diagram showing a state in which two rack teeth 41 are in contact with the gear 31a of the pinion gear 31. When two rack teeth 41 are in contact with the pinion gear 31 simultaneously, as shown in FIG. 8, the two rack teeth 41 contact one gear 31a of the pinion gear 31 from both sides in the tooth thickness direction of the gear 31a. Therefore, while the gear 31a of the rotating pinion gear 31 is positioned on the rack bar 40 side, the rack teeth 41 can be kept in contact with both sides of the gear 31a, thereby suppressing the hitting noise that occurs when the gear 31a of the pinion gear 31 and the rack teeth 41, which are spaced apart, come into contact with each other. Furthermore, by having the two rack teeth 41 in contact with both sides of the gear 31a of the pinion gear 31, play between the pinion gear 31 and the rack bar 40 can be reduced, thereby improving the steering feel during steering.

[0073] Furthermore, by limiting the number of teeth of the rack teeth 41 that simultaneously contact the pinion gear 31 to four or less, it is possible to reduce the difference between the maximum and minimum numbers of the rack teeth 41 that simultaneously contact the pinion gear 31, thereby reducing fluctuations in steering resistance during steering. As a result, it is possible to suppress changes in steering resistance during steering, suppress hitting noise, and improve steering feel.

[0074] [Modification] In the embodiment described above, the narrow pitch portions 45 are arranged in the center and at both ends of the rack tooth arrangement range 44, but the narrow pitch portions 45 may be arranged in other positions. Fig. 9 is a schematic diagram showing a modification of the steering device 1 according to the embodiment, in which the narrow pitch portion 45 is arranged in the center of the rack tooth arrangement range 44. For example, as shown in Fig. 9, the narrow pitch portion 45 may be arranged in the center of the rack tooth arrangement range 44, and the narrow pitch portions 45 may not be arranged at both ends of the rack tooth arrangement range 44. In this case, the wide pitch portions 46 are arranged over the entire area of ​​the rack tooth arrangement range 44 on both sides of the narrow pitch portion 45.

[0075] For example, if the load on the rack teeth 41 during steering is small because the vehicle on which the steering device 1 is mounted is relatively small and lightweight, the force acting between the rack teeth 41 and the pinion gear 31 is unlikely to become large even near the maximum steering angle. In such a case, since the stress on the rack teeth 41 is unlikely to become large even near the maximum steering angle, wide pitch portions 46 may be provided instead of narrow pitch portions 45 at both ends of the rack tooth arrangement range 44. In this way, if the load on the rack teeth 41 is small even near the maximum steering angle, by providing wide pitch portions 46 near both ends of the rack tooth arrangement range 44, it is possible to increase responsiveness when steering at large steering angles and improve the steering feel.

[0076] Furthermore, in the above-described embodiment, the rack teeth 41 located in the narrow pitch portion 45 have the tooth thickness changing portion 42 on one surface in the tooth thickness direction T, and the rack teeth 41 located in the wide pitch portion 46 do not have the tooth thickness changing portion 42, but the rack teeth 41 located in the narrow pitch portion 45 and the rack teeth 41 located in the wide pitch portion 46 may be formed in a form other than this.

[0077] FIG. 10 is an explanatory diagram showing a modified example of the steering device 1 according to the embodiment, in which the tooth thickness changing portion 42 is formed on one side of the rack tooth 41 located in the wide pitch portion 46. FIG. 11 is an explanatory diagram showing a modified example of the steering device 1 according to the embodiment, in which the tooth thickness changing portion 42 is formed on both sides of the rack tooth 41 located in the narrow pitch portion 45. For example, as shown in FIG. 10 , the rack tooth 41 located in the wide pitch portion 46 may have the tooth thickness changing portion 42 on one side in the tooth thickness direction T and the other side may be a flat portion 41 a. For example, as shown in FIG. 11 , the rack tooth 41 located in the narrow pitch portion 45 may have the tooth thickness changing portion 42 on both sides in the tooth thickness direction T. In other words, the rack tooth 41 located in the wide pitch portion 46 may have a crowning 43 as the tooth thickness changing portion 42 on one side in the tooth thickness direction T, and the rack tooth 41 located in the narrow pitch portion 45 may have the crowning 43 as the tooth thickness changing portion 42 on both sides in the tooth thickness direction T.

[0078] In this way, the tooth thickness changing portion 42 is formed on one side of the rack tooth 41 located in the wide pitch portion 46, and the tooth thickness changing portion 42 is formed on both sides of the rack tooth 41 located in the narrow pitch portion 45, thereby making it possible to reduce the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that simultaneously contact the pinion gear 31.

[0079] That is, the rack teeth 41 located in the narrow pitch portion 45 can offset the ease of contact with the pinion gear 31 due to the narrower pitch than the wide pitch portion 46, and the difficulty of contact with the pinion gear 31 due to the rack teeth 41 located in the wide pitch portion 46 having more surfaces on which the tooth thickness changing portions 42 are formed than the rack teeth 41 located in the wide pitch portion 46. In other words, the rack teeth 41 located in the wide pitch portion 46 can offset the difficulty of contact with the pinion gear 31 due to the wider pitch than the narrow pitch portion 45, and the ease of contact with the pinion gear 31 due to the rack teeth 41 located in the narrow pitch portion 45 having fewer surfaces on which the tooth thickness changing portions 42 are formed than the rack teeth 41 located in the narrow pitch portion 45.

[0080] This makes it possible to reduce the difference between the maximum and minimum numbers of rack teeth 41 that simultaneously contact the pinion gear 31 throughout the entire rack tooth arrangement range 44, thereby reducing fluctuations in steering resistance during steering. As a result, it is possible to suppress changes in steering resistance during steering without reducing the rigidity of the rack bar 40.

[0081] Furthermore, in the above-described embodiment, the tooth thickness changing portion 42 of the rack tooth 41 is formed by the crowning 43, but the tooth thickness changing portion 42 may be formed by something other than the crowning 43. The tooth thickness changing portion 42 may be, for example, a so-called end relief formed such that the tooth thickness of the rack tooth 41 near the center in the tooth width direction W is constant and the tooth thickness of the end portion in the tooth width direction W is smaller than the tooth thickness at the center in the tooth width direction W. The shape of the tooth thickness changing portion 42 is not limited as long as the tooth thickness of the rack tooth 41 at the end portion in the tooth width direction W is smaller than the tooth thickness at the center in the tooth width direction W.

[0082] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. The configurations described as the embodiments and modified examples may be combined as appropriate.

[0083] REFERENCE SIGNS LIST 1 Steering device 10 Rack housing 11 Pinion housing 12 Reducer housing 20 Steering wheel 21 First steering shaft 22 Second steering shaft 24 First bearing 25 Second bearing 26 First universal joint 27 Second universal joint 30 Pinion shaft 31 Pinion gear 31a Gear 32 Cylindrical surface 40 Rack bar 41 Rack teeth 41a Flat portion 42 Tooth thickness changing portion 43 Crowning 44 Rack tooth arrangement range 45 Narrow pitch portion 46 Wide pitch portion 47 Transition region 50 Worm reducer 51 Worm wheel 52 Worm shaft 53 Electric motor 60 Tie rod 65 Wheel 80 ECU 85 Power supply device

Claims

1. A steering device comprising a pinion gear having helical teeth, and a rack bar having a plurality of helical rack teeth meshing with the pinion gear, wherein the rack teeth have a wide pitch portion in which a plurality of the rack teeth are arranged at a predetermined pitch, and a narrow pitch portion in which the pitch of the plurality of the rack teeth is narrower than the pitch between the rack teeth located in the wide pitch portion, the rack teeth located in the wide pitch portion have a constant tooth thickness in the tooth width direction, and the rack teeth located in the narrow pitch portion have a tooth thickness change portion on one surface in the tooth thickness direction, where the tooth thickness at the end in the tooth width direction is smaller than the tooth thickness at the center in the tooth width direction.

2. A steering device comprising a pinion gear having helical teeth, and a rack bar having a plurality of helical rack teeth meshing with the pinion gear, wherein the rack teeth have a wide pitch portion in which a plurality of the rack teeth are arranged at a predetermined pitch, and a narrow pitch portion in which the pitch of the plurality of the rack teeth is narrower than the pitch between the rack teeth located in the wide pitch portion, the rack teeth located in the wide pitch portion have a tooth thickness change portion on one surface in the tooth thickness direction, where the tooth thickness at the end in the tooth width direction is smaller than the tooth thickness at the center in the tooth width direction, and the rack teeth located in the narrow pitch portion have the tooth thickness change portion on both surfaces in the tooth thickness direction.

3. The steering device according to claim 1 or 2, wherein the tooth thickness change portion is a crowning in which the tooth thickness at the center in the tooth width direction is the largest and the tooth thickness decreases toward the ends in the tooth width direction.

4. The steering device according to any one of claims 1 to 3, wherein the narrow pitch portions are arranged at the center and both ends in the longitudinal direction of the rack bar in a range where a plurality of the rack teeth are arranged, and the wide pitch portion is arranged between the center and the narrow pitch portions at both ends in the longitudinal direction of the rack bar.

5. The steering device according to any one of claims 1 to 3, wherein the narrow pitch portion is arranged at the center in the longitudinal direction of the rack bar in a range where a plurality of the rack teeth are arranged, and the wide pitch portions are arranged on both sides of the narrow pitch portion in the longitudinal direction of the rack bar.

6. The steering apparatus according to any one of claims 1 to 5, wherein the number of rack teeth that are in contact with the pinion gear simultaneously is in the range of 2 or more and 4 or less.

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