Steering device

Abstract

To provide a steering device capable of suppressing a change in steering resistance upon steering without reducing rigidity of a rack bar.SOLUTION: A steering device is provided with a pinion gear 31 having a helical gear and a rack bar 40 having a plurality of helical rack teeth 41 engaging with the pinion gear 31, wherein the rack teeth 41 include a wide pitch part 46 in which a plurality of rack teeth 41 are arranged at a prescribed pitch, and a narrow pitch part 45 in which a plurality of the rack teeth 41 are arranged at a narrower pitch than the pitch between the rack teeth 41 at the wide pitch part 46. A rack tooth 41 positioned at the wide pitch part 46 has a constant tooth thickness in a tooth width direction W, and a rack tooth 41 positioned at the narrow pitch part 45 has a tooth thickness change part 42 in which a tooth thickness at an end part in the tooth width direction W is smaller than a center tooth thickness in the tooth width direction W.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] A steering device has a pinion gear that rotates by a rotational torque when a steering wheel is steered, and a rack bar having rack teeth that mesh with the pinion gear. The steering device configured in this way can transmit the rotational torque input from the steering wheel from the pinion gear to the rack bar, and by linearly moving the rack bar, it is possible to change the direction of the steered wheels according to the steering angle of the steering wheel. Further, among conventional steering devices, there are some provided with a so-called variable gear ratio mechanism in which the pitch of the rack teeth provided on the rack bar is made different according to the position in the longitudinal direction of the rack bar.

[0003] For example, in the steering device described in Patent Document 1, the meshing portion composed of a plurality of rack teeth on the rack shaft has a narrow pitch portion and a wide pitch portion in which the pitches of the plurality of rack teeth are different. Further, in the steering device described in Patent Document 1 having such a narrow pitch portion and a wide pitch portion, a rack bush that supports the rack shaft is provided, and the sliding resistance between the rack shaft and the rack bush when the pinion tooth portion meshes with the narrow pitch portion is made smaller than the sliding resistance when the pinion tooth portion meshes with the wide pitch portion, thereby suppressing fluctuations in the steering reaction force due to the steering angle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, in Patent Document 1, in order to change the sliding resistance between the rack shaft and the rack bush, the diameter of the rack shaft is changed. That is, a portion of the rack shaft that is in sliding contact with the rack bush when the pinion tooth portion meshes with the narrow pitch portion is a small-diameter portion, and a portion of the rack shaft that is in sliding contact with the rack bush when the pinion tooth portion meshes with the wide pitch portion is a large-diameter portion. Thereby, when the pinion tooth portion meshes with the narrow pitch portion, since the small-diameter portion is in sliding contact with the rack bush, the sliding resistance can be made smaller than when the large-diameter portion is in sliding contact with the rack bush when the pinion tooth portion meshes with the wide pitch portion.

[0006] However, when the diameter of the rack bar is reduced, the support rigidity of the rack bar decreases, so the rigidity during steering decreases, which may lead to a decrease in the feeling during steering. For this reason, in a steering apparatus including a rack bar having pitches of a plurality of rack teeth, there is room for improvement from the viewpoint of ensuring the rigidity of the rack bar in suppressing fluctuations in steering resistance, which is a resistance to steering such as sliding resistance that varies with fluctuations in pitch.

[0007] The present disclosure has been made in view of the above, and an object thereof is to provide a steering apparatus capable of suppressing changes in steering resistance during steering without reducing the rigidity of the rack bar.

Means for Solving the Problems

[0008] The steering device of the present disclosure includes a pinion gear having helical teeth and a rack bar having a plurality of helical rack teeth meshing with the pinion gear. The rack teeth include 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 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.

[0009] According to this configuration, since the rack teeth located in the narrow pitch portion have the tooth thickness change portion 42, when the rotating pinion gear contacts the rack teeth located in the narrow pitch portion, it is difficult to make contact near the end in the tooth width direction of the rack teeth. 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 end in the tooth width direction of the rack teeth. Accordingly, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth that are simultaneously in contact with the pinion gear can be reduced, and without changing the sliding resistance between the rack bar and the rack bush by partially reducing the diameter of the rack bar, the variation in steering resistance during steering can be reduced. As a result, without reducing the rigidity of the rack bar, the change in steering resistance during steering can be suppressed.

[0010] The steering device of the present disclosure includes a pinion gear having helical teeth, and a rack bar having a plurality of helical rack teeth that mesh with the pinion gear. The rack teeth have a wide pitch portion in which the plurality of rack teeth are arranged at a predetermined pitch, and a narrow pitch portion in which 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 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. The rack teeth located in the narrow pitch portion have the tooth thickness change portion on both surfaces in the tooth thickness direction.

[0011] According to this configuration, by forming the tooth thickness change portion on one side of the rack teeth located in the wide pitch portion and on both sides of the rack teeth located in the narrow pitch portion, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth that are in contact with the pinion gear simultaneously can be reduced. Thereby, without changing the sliding resistance between the rack bar and the rack bush by partially reducing the diameter of the rack bar, the variation in the steering resistance during steering can be reduced. As a result, without reducing the rigidity of the rack bar 40, the change in the steering resistance during steering can be suppressed.

[0012] Desirably, 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 end in the tooth width direction.

[0013] According to this configuration, since the tooth thickness change portion is crowning, when the rotating pinion gear contacts the rack teeth located in the narrow pitch portion, it is difficult to make contact near the end in the tooth width direction. As a result, 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 end in the tooth width direction due to crowning. Therefore, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth that are simultaneously in contact with the pinion gear can be reduced, and the variation in steering resistance during steering can be reduced. As a result, without reducing the rigidity of the rack bar, the change in steering resistance during steering can be suppressed.

[0014] In a desirable form, the narrow pitch portions are arranged at the center and both ends in the range where a plurality of the rack teeth are arranged in the longitudinal direction of the rack bar, and the wide pitch portion is arranged between the center in the longitudinal direction of the rack bar and the narrow pitch portions at both ends.

[0015] According to this configuration, since the narrow pitch portions are arranged at the center and both ends in the range where the rack teeth are arranged, the steering feeling near straight-ahead driving is ensured by the narrow pitch portion at the center, and the stress of the rack teeth near the maximum steering angle can be reduced by the narrow pitch portions at both ends to ensure durability. Also, since the wide pitch portion is arranged between the center in the longitudinal direction of the rack bar and the narrow pitch portions at both ends, the responsiveness to steering at a steering angle between straight-ahead driving and the maximum steering angle can be enhanced by the wide pitch portion, and the steering feeling when steering at a steering angle larger than that during straight-ahead driving can be ensured. As a result, both the steering feeling during vehicle running and the durability of the rack bar can be improved.

[0016] In a desirable form, the narrow pitch portion is arranged at the center in the range where a plurality of the rack teeth are arranged in the longitudinal direction of the rack bar, and the wide pitch portions are arranged on both sides of the narrow pitch portion in the longitudinal direction of the rack bar.

[0017] According to this configuration, the narrow pitch portion is arranged in the center of the range where the rack teeth are arranged, and wide pitch portions are provided at both ends of the narrow pitch portion. Therefore, the responsiveness when steering at a large steering angle can be enhanced. As a result, the steering feeling can be improved.

[0018] As a desirable form, 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.

[0019] According to this configuration, since the number of rack teeth that are in contact with the pinion gear simultaneously is 2 or more, the knocking sound can be suppressed and the steering feeling can be improved. Further, since the number of rack teeth that are in contact with the pinion gear simultaneously is 4 or less, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth that are in contact with the pinion gear simultaneously can be reduced, and the variation in the steering resistance during steering can be reduced. As a result, the change in the steering resistance during steering can be suppressed, the knocking sound can be suppressed, and the steering feeling can be improved.

Advantages of the Invention

[0020] The steering apparatus according to the present disclosure has an effect that it is possible to suppress a change in the steering resistance during steering without reducing the rigidity of the rack bar.

Brief Description of the Drawings

[0021]

Fig. 1

Fig. 2

Fig. 3

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Fig. 8

Fig. 9

Fig. 10

Fig. 11

MODE FOR CARRYING OUT THE INVENTION

[0022] Hereinafter, the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited by the following mode for carrying out the invention (hereinafter referred to as the embodiment). In addition, the constituent elements in the following embodiment include those that can be easily assumed by those skilled in the art, substantially the same ones, and those within a so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiment can be combined as appropriate.

[0023] [Embodiment] FIG. 1 is a schematic diagram of a steering device 1 according to an embodiment. In the drawings, 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. Also, 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, tie rods 60, a rack housing 10, an ECU 80, and a power supply device 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 by the torque for steering 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, and the first steering shaft 21 rotates.

[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, and the second steering shaft 22 rotates.

[0027] The rack housing 10 is formed in a cylindrical shape. The rack housing 10 is provided with 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, and the pinion shaft 30 rotates. 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 by the pinion housing 11 via the first bearing 24 and the second bearing 25. The first bearing 24 supports the upper part of the pinion shaft 30. The second bearing 25 supports the lower part of the pinion shaft 30. Specifically, the first bearing 24 is provided on the cylindrical surface 32 on the upper side (D1 side, one side in the axial direction) of the pinion gear 31.

[0029] Inside the rack housing 10, a rack bar 40 is accommodated. The rack bar 40 is formed in a shaft-like shape extending in a predetermined direction, and is arranged with its longitudinal direction in the vehicle width direction of the vehicle. The rack bar 40 has a plurality of rack teeth 41 on its surface at a predetermined position 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 respectively arranged on both sides in the longitudinal direction of the rack bar 40 and are each connected to the rack bar 40. Further, on the tie rod 60, the portion on the opposite side of the portion connected to the rack bar 40 is connected to the wheel 65. Therefore, when the pinion shaft 30 rotates, a longitudinal force of the rack bar 40 is transmitted to the rack teeth 41 meshing with the pinion gear 31, and the rack bar 40 moves in the longitudinal direction, that is, in the vehicle width direction. As a result, the tie rod 60 moves in the vehicle width direction, the direction of the wheel 65 changes, and the traveling direction of the vehicle changes.

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

[0032] The worm speed 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 speed 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. Thereby, the electric motor 53 can apply an auxiliary steering torque to the pinion shaft 30, and the force required for steering the steering wheel 20 can be reduced.

[0033] The ECU 80 is connected to a power supply device 85 (for example, an in-vehicle 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 power value 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 on the electric motor 53. By the ECU 80 controlling the operation of the electric motor 53, as described above, an auxiliary steering torque can be applied from the electric motor 53 to the pinion shaft 30, and the force required for steering the steering wheel 20 can be reduced.

[0034] As shown in FIG. 1, the steering apparatus 1 according to the embodiment is a single-pinion type electric power steering apparatus in which an assist force is applied to the pinion shaft 30, but the steering apparatus 1 is not limited thereto. The steering apparatus 1 may be, for example, a column assist type in which an assist force is applied to the first steering shaft 21, or a dual-pinion type electric power steering apparatus including a second pinion gear (not shown) that meshes with the rack bar 40 at a position different from the pinion gear 31, and an assist force is applied to the second pinion gear. Further, it may be a rack assist type electric power steering apparatus of a type that applies an assist force to the rack bar 40 without passing through 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 included in the rack bar 40 shown in FIG. 1. The rack teeth 41 included in the rack bar 40 are arranged side by side in the longitudinal direction of the rack bar 40. Further, since the rack teeth 41 are formed by helical teeth, each rack tooth 41 is formed to be inclined with respect to the longitudinal direction of the rack bar 40. The plurality of rack teeth 41 arranged on the rack bar 40 in this way have pitches between the rack teeth 41 in the longitudinal direction of the rack bar 40 arranged at a plurality of pitches.

[0036] Specifically, the rack teeth 41 have a wide pitch portion 46 in which a plurality of rack teeth 41 are arranged at a predetermined pitch, and a narrow pitch portion 45 in which the pitch of 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 is relatively different between the rack teeth 41 located in the wide pitch portion 46 and the rack teeth 41 located in the narrow pitch portion 45, and the pitch of the 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 portion 45 is arranged at three positions, i.e., the center and both ends in the longitudinal direction of the rack bar 40, within the rack tooth arrangement range 44 where a plurality of rack teeth 41 are arranged in the longitudinal direction of the rack bar 40. The wide pitch portion 46 is arranged at two positions between the narrow pitch portions 45, i.e., between the narrow pitch portion 45 at the center and the narrow pitch portions 45 at both ends, within the rack tooth arrangement range 44. The narrow pitch portion 45 is arranged, for example, in a range of about ±10 mm centered on 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 end 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. When including these transition regions where the pitch gradually increases or decreases in the narrow pitch portion 45, the narrow pitch portion 45 is arranged in a range of about ±25 mm centered on the center of the rack tooth arrangement range 44 and in a range of about 25 mm from the end of the rack tooth arrangement range 44.

[0038] FIG. 3 is a detailed view of the rack teeth 41 arranged in the wide pitch portion 46 shown in FIG. 2. The rack teeth 41 of the rack bar 40 have a tooth thickness that decreases in terms of the thickness of the rack teeth 41 from the base end side to the tip end side of the rack teeth 41. Further, 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 are formed as flat portions 41a in which both side surfaces in the tooth thickness direction T are formed substantially flat along the tooth width direction W. For this reason, for the rack teeth 41 located in the wide pitch portion 46, at portions where the heights from the base end side are the same regardless of the position in the tooth width direction W, the tooth thicknesses in the tooth thickness direction T are the same.

[0039] FIG. 4 is a detailed view of the rack teeth 41 disposed in the narrow pitch portion 45 shown in FIG. 2. The rack teeth 41 located in the narrow pitch portion 45 have a tooth thickness change portion 42 on one surface in the tooth thickness direction T, where 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 the present embodiment, the tooth thickness change portion 42 is formed by so-called crowning 43 in which the tooth thickness at the center in the tooth width direction W is the largest and the tooth thickness decreases toward the ends in the tooth width direction W. Therefore, one surface of the rack teeth 41 located in the narrow pitch portion 45 is curved in a direction in which the tooth thickness decreases from the center position in the tooth width direction W toward both ends in the tooth width direction W in the tooth thickness direction T.

[0040] On the other hand, the tooth thickness change portion 42 is not formed on the surface opposite to the surface having the tooth thickness change portion 42 of the rack teeth 41 located in the narrow pitch portion 45, that is, crowning 43 is not applied. That is, the surface of the rack teeth 41 located in the narrow pitch portion 45 on the side where crowning 43 is not applied is a flat portion 41a formed substantially flat along the tooth width direction W. Therefore, the flat portion 41a, which is the surface opposite to the surface having the tooth thickness change portion 42 of the rack teeth 41 located in the narrow pitch portion 45, extends linearly in the tooth width direction W between portions having the same height from the proximal end side.

[0041] The crowning 43 on one surface in the tooth thickness direction T of the rack teeth 41 located in the narrow pitch portion 45 is applied to the same side surface in the longitudinal direction of the rack bar 40 for a plurality of rack teeth 41 located in the narrow pitch portion 45. That is, the crowning 43 is applied to the same side surface in the longitudinal direction of the rack bar 40 for the plurality of rack teeth 41 located in the central narrow pitch portion 45 and the plurality of rack teeth 41 located in the narrow pitch portions 45 at both ends in the rack tooth arrangement range 44.

[0042] Next, the operation of the steering device 1 will be described. When the steering wheel 20 is operated during the operation of a vehicle on which the steering device 1 is mounted, 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 a steering torque from the first steering shaft 21 to the second steering shaft 22 and then from the second steering shaft 22 to the pinion shaft 30.

[0043] The pinion shaft 30 has a pinion gear 31 that meshes with the rack teeth 41 of the rack bar 40, and the 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 plurality of rack teeth 41 are arranged. The rack bar 40 converts the steering torque transmitted from the pinion shaft 30 into a linear motion in the longitudinal direction of the rack bar 40 in this way. That is, the rack bar 40 moves in the vehicle width direction, which is the longitudinal direction of the rack bar 40 arranged in the vehicle.

[0044] Since tie rods 60 are connected to both ends of the rack bar 40, as the rack bar 40 moves in the vehicle width direction, the tie rods 60 connected to the rack bar 40 also operate. Since the tie rods 60 are connected to the wheels 65, the direction of the wheels 65 changes when the tie rods 60 operate. As a result, the vehicle on which the steering device 1 is mounted changes its traveling direction according to the operation of the steering wheel 20.

[0045] In addition, the steering device 1 according to the embodiment has an electric motor 53 that generates an auxiliary steering torque for assisting the driver's steering. The electric motor 53 generates an 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 to the ECU 80 as an electric signal, 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 an 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] That is, 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 is transmitted to the pinion shaft 30 via the worm wheel 51. Thereby, the electric motor 53 assists the rotation of the pinion shaft 30 that rotates 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 for steering the steering wheel 20 is reduced by the transmission of the auxiliary steering torque generated by the electric motor 53 to the pinion shaft 30.

[0047] In addition, the plurality of rack teeth 41 of the rack bar 40 have a narrow pitch portion 45 and a wide pitch portion 46, and the narrow pitch portion 45 is located at the center and both ends in the rack tooth arrangement range 44. That is, the narrow pitch portion 45 is located near the center and near both ends in the rotation range of the steering wheel 20 that rotates the pinion gear 31 meshing with the rack teeth 41. For this reason, the rack teeth 41 located in the narrow pitch portion 45 mesh with the pinion gear 31 near straight-ahead travel and near the maximum steering angle when the vehicle is running.

[0048] During straight-ahead driving while the vehicle is in motion, the steering wheel 20 rotates slightly according to the direction of road travel, road surface conditions, etc., without significant rotation, or rotates slightly during lane changes. In the vicinity of such straight-ahead driving, since the pinion gear 31 meshes with the rack teeth 41 of the narrow pitch portion 45, the amount of movement of the rack bar 40 in the longitudinal direction with respect to the rotation of the steering wheel 20, that is, the rotation of the pinion gear 31, becomes small. For this reason, in the vicinity of straight-ahead driving, the amount of change in the direction of the wheel 65 with respect to the rotation of the steering wheel 20 becomes small, making it easier to perform fine steering adjustments and ensuring the steering feeling in the vicinity of straight-ahead driving.

[0049] Also, near the maximum steering angle while the vehicle is in motion, since the direction of the wheel 65 changes significantly from the direction when going straight, when driving the vehicle in this state, a large force in the direction of returning the direction of the wheel 65 to the direction when going straight acts on the wheel 65 that is being steered from the road surface. The large force in the direction of returning the direction of the wheel 65 to the direction when going straight is transmitted from the wheel 65 to the rack bar 40 via the tie rod 60 and then transmitted from the rack teeth 41 to the pinion gear 31.

[0050] For this reason, near the maximum steering angle while the vehicle is in motion, a large force acts between the rack teeth 41 and the pinion gear 31, but the rack teeth 41 that mesh with the pinion gear 31 near the maximum steering angle among the rack teeth 41 arranged on the rack bar 40 are the rack teeth 41 located in the narrow pitch portion 45. Thus, near the maximum steering angle, since the rack teeth 41 and the pinion gear 31 mesh with the rack teeth 41 and the pinion gear 31 located in the narrow pitch portion 45, the number of teeth of the rack teeth 41 that come into contact with the pinion gear 31 simultaneously is larger compared to the case where the rack teeth 41 and the pinion gear 31 located in the wide pitch portion 46 mesh.

[0051] As a result, near the maximum steering angle, a large force acting between the rack teeth 41 and the pinion gear 31 can be received by a larger number of rack teeth 41 compared to the case where the rack teeth 41 located in the wide pitch portion 46 mesh with the pinion gear 31. Therefore, the stress of the rack teeth 41 near the maximum steering angle where a large force acts between the rack teeth 41 and the pinion gear 31 can be reduced, and durability can be ensured.

[0052] Also, at a steering angle between straight-ahead driving and the maximum steering angle during vehicle running, the pinion gear 31 meshes with the rack teeth 41 located in the wide pitch portion 46. In the wide pitch portion 46, since the pitch of the rack teeth 41 is wider than the pitch of the rack teeth 41 in the narrow pitch portion 45, the amount of movement of the rack bar 40 in the longitudinal direction with respect to the rotation of the steering wheel 20, that is, the rotation of the pinion gear 31, becomes larger compared to the state where the pinion gear 31 meshes with the rack teeth 41 located in the narrow pitch portion 45. For this reason, at a steering angle between straight-ahead driving and the maximum steering angle during vehicle running, the amount of change in the direction of the wheel 65 with respect to the rotation of the steering wheel 20 becomes larger, so the responsiveness to steering can be enhanced, and the steering feeling when steering at a larger steering angle than during straight-ahead driving can be ensured.

[0053] Also, 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 are in contact with the pinion gear 31 simultaneously is smaller compared to the case where the rack teeth 41 located in the narrow pitch portion 45 mesh with the pinion gear 31. However, at a steering angle 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 near the maximum steering angle. For this reason, at a steering angle smaller than near the maximum steering angle, even if the number of rack teeth 41 that are in contact with the pinion gear 31 simultaneously is small, the stress of the rack teeth 41 is less likely to increase, and durability is ensured.

[0054] In addition, in the present embodiment, the rack teeth 41 located in the wide pitch portion 46 do not have crowning 43, and the rack teeth 41 located in the narrow pitch portion 45 have crowning 43 on one surface in the tooth thickness direction T. Therefore, the number of teeth of the rack teeth 41 that are in contact with the pinion gear 31 simultaneously in the state where the pinion gear 31 and the rack teeth 41 are engaged can be made as uniform as possible over the entire area of the rack tooth arrangement range 44. That is, when the pinion gear 31 and the rack teeth 41 are engaged, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that are in contact with the pinion gear 31 simultaneously can be made as small as possible.

[0055] That is, since the pinion gear 31 has the side gear 31a (see FIG. 8), and the rack teeth 41 also serve as side teeth, when the side gear 31a of the pinion gear 31 and the rack teeth 41 come into contact, they come into contact gradually from the position near the end in the direction in which the side gear 31a and the rack teeth 41 are formed. For example, the rack teeth 41 gradually come into contact with the side gear 31a of the pinion gear 31 from the position near the end in the tooth width direction W, and the position of contact changes in the tooth width direction W according to the rotation of the pinion gear 31.

[0056] Also, the pitch between the rack teeth 41 located in the narrow pitch portion 45 is narrower than the pitch between the rack teeth 41 located in the wide pitch portion 46. Therefore, when the side gear 31a of the pinion gear 31 comes into contact with the rack teeth 41 due to the rotation of the pinion gear 31, 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, since the rack teeth 41 located in the narrow pitch portion 45 have crowning 43 on one surface in the tooth thickness direction T, the pinion gear 31 is less likely to come into contact with the surface of the rack teeth 41 located in the narrow pitch portion 45 where the crowning 43 is provided, near the end portion in the tooth width direction W. Also, when the pinion gear 31 that is in contact with the side where the crowning 43 is provided on the rack teeth 41 located in the narrow pitch portion 45 moves away from the rack teeth 41 as the pinion gear 31 rotates, it is likely to move away from near the end portion in the tooth width direction W.

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

[0059] Therefore, in the present embodiment, when the rotating pinion gear 31 meshes with the rack teeth 41, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that are in contact with the pinion gear 31 simultaneously becomes smaller throughout the rack tooth arrangement range 44.

[0060] Next, the transition of the number of teeth that are simultaneously in contact between the rack teeth 41 of the rack bar 40 and the pinion gear 31 when the pinion gear 31 rotates will be described. FIG. 5 is an explanatory diagram of the transition of the number of teeth of the rack teeth 41 that are simultaneously in contact with the rotating pinion gear 31 of the rack bar 40 without crowning 43. FIG. 5 is an explanatory diagram showing an example of the transition of the number of teeth of the rack teeth 41 that are simultaneously in contact with the pinion gear 31 when the contact portion between the rack teeth 41 of the rack bar 40 without crowning 43 and the pinion gear 31 moves from one end side to the other end side of the rack tooth arrangement range 44. Note that FIGS. 5 and FIGS. 6 and 7 described later are explanatory diagrams in a form in which a transition region 47, which is a portion 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 therebetween.

[0061] In the example shown in FIG. 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 simultaneously in contact with the pinion gear 31 changes between 3 and 5 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 simultaneously in contact with the pinion gear 31 changes between 2 and 3 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 simultaneously in contact with the pinion gear 31 changes between 3 and 4 by rotating the pinion gear 31. Therefore, in the example shown in FIG. 5, the number of teeth of the rack teeth 41 that are simultaneously in contact with the pinion gear 31 changes between 2 and 5 according to the position where the pinion gear 31 and the rack teeth 41 are in contact.

[0062] FIG. 6 is an explanatory diagram of the transition of the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 when the rack teeth 41 of the rack bar 40 with crowning 43 applied to 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 the transition of the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 when the portion where the rack teeth 41 of the rack bar 40 with crowning 43 applied to both sides of the rack teeth 41 and the pinion gear 31 are in contact moves from one end side to the other end side of the rack tooth arrangement range 44.

[0063] In the example shown in FIG. 6, when the rack teeth 41 located in the narrow pitch portion 45 are in contact with the pinion gear 31, the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 changes between 2 and 4 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 rack teeth 41 that are simultaneously in contact with the pinion gear 31 changes between 1 and 2 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 rack teeth 41 that are simultaneously in contact with the pinion gear 31 changes between 1 and 3 by rotating the pinion gear 31. Therefore, in the example shown in FIG. 6, the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 changes between 1 and 4 according to the position where the pinion gear 31 and the rack teeth 41 are in contact.

[0064] FIG. 7 is an explanatory diagram of the transition of the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 when the rack teeth 41 of the rack bar 40 with crowning 43 applied to 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 the transition of the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 when the portion where the rack teeth 41 of the rack bar 40 with crowning 43 applied to one side of the rack teeth 41 located in the narrow pitch portion 45 and the pinion gear 31 are in contact moves from one end side to the other end side of the rack tooth arrangement range 44.

[0065] In the example shown in FIG. 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 simultaneously in contact with the pinion gear 31 changes between 3 and 4 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 simultaneously in contact with the pinion gear 31 changes between 2 and 3 by rotating the pinion gear 31. Also, even 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 simultaneously in contact with the pinion gear 31 changes between 2 and 3 by rotating the pinion gear 31. For this reason, in the example shown in FIG. 7, the number of teeth of the rack teeth 41 that are simultaneously in contact with the pinion gear 31 changes between 2 and 4 according to the position where the pinion gear 31 and the rack teeth 41 are in contact.

[0066] As is clear from the examples shown in FIGS. 5, 6, and 7, when crowning 43 is applied to one side of the rack teeth 41 located in the narrow pitch portion 45, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that are simultaneously in contact with the pinion gear 31 is smaller than when crowning 43 is not applied to the rack teeth 41 or when crowning 43 is applied to both sides of the rack teeth 41. For this reason, when crowning 43 is applied to one side of the rack teeth 41 located in the narrow pitch portion 45, the fluctuation of the steering resistance during steering can be reduced more than when crowning 43 is not applied to the rack teeth 41 or when crowning 43 is applied to both sides of the rack teeth 41.

[0067] Also, as is clear from the examples shown in FIGS. 5 and 7, when crowning 43 is applied to one side of the rack teeth 41 located in the narrow pitch portion 45, the maximum number of rack teeth 41 that come into contact with the pinion gear 31 simultaneously is less than that in the case where crowning 43 is not applied to the rack teeth 41. For this reason, when crowning 43 is applied to one side of the rack teeth 41 located in the narrow pitch portion 45, the steering resistance during steering can be made smaller than in the case where crowning 43 is not applied to the rack teeth 41.

[0068] As described above, in the steering apparatus 1 according to the embodiment, the rack teeth 41 of the rack bar 40 have a wide pitch portion 46 and a narrow pitch portion 45, and the rack teeth 41 located in the narrow pitch portion 45 have a tooth thickness change portion 42 on one surface in the tooth thickness direction T, where 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. Thereby, when the rotating pinion gear 31 comes into contact with the rack teeth 41 located in the narrow pitch portion 45, it is possible to make it difficult to contact near the ends in the tooth width direction W of the rack teeth 41. For this reason, 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. Therefore, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that come into contact with the pinion gear 31 simultaneously can be made small throughout the rack tooth arrangement range 44, and 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, the variation in steering resistance during steering can be reduced. As a result, without reducing the rigidity of the rack bar 40, the change in steering resistance during steering can be suppressed.

[0069] In addition, the tooth thickness change portion 42 of the rack teeth 41 located in the narrow pitch portion 45 is a crowning 43 in which the tooth thickness decreases from the center toward the end in the tooth width direction W of the rack teeth 41. Therefore, when the rotating pinion gear 31 comes into contact with the rack teeth 41 located in the narrow pitch portion 45, it can be made difficult to contact near the end 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 end in the tooth width direction W of the rack teeth 41 due to the crowning 43. Therefore, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that are simultaneously in contact with the pinion gear 31 can be reduced, and the variation in steering resistance during steering can be reduced. As a result, without reducing the rigidity of the rack bar 40, the change in steering resistance during steering can be suppressed.

[0070] In addition, since the narrow pitch portions 45 are arranged at the center and both ends in the rack tooth arrangement range 44, the steering feeling near straight-ahead driving is ensured by the narrow pitch portion 45 at the center, and the stress of the rack teeth 41 near the maximum steering angle can be reduced by the narrow pitch portions 45 at both ends to ensure durability. Further, since the wide pitch portion 46 is arranged between the center in the longitudinal direction of the rack bar 40 and the narrow pitch portions 45 at both ends, the responsiveness to steering at a steering angle between straight-ahead driving and the maximum steering angle can be enhanced by the wide pitch portion 46, and the steering feeling when steering at a steering angle larger than that during straight-ahead driving can be ensured. As a result, both the steering feeling during vehicle running and the durability of the rack bar 40 can be improved.

[0071] In addition, since the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 is in the range of 2 or more and 4 or less, it is possible to suppress knocking while suppressing the change in steering resistance during steering, and further improve the steering feeling. That is, since the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 is 2 or more, knocking can be suppressed and the steering feeling can be improved.

[0072] FIG. 8 is an explanatory view 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 simultaneously in contact with the pinion gear 31, as shown in FIG. 8, the two rack teeth 41 are in contact with the gear 31a from both sides in the tooth thickness direction of one gear 31a of the pinion gear 31. Therefore, while the gear 31a of the rotating pinion gear 31 is positioned on the side of the rack bar 40, the rack teeth 41 can be continuously brought into contact with both surfaces of the gear 31a, and the impact noise generated when the separated gear 31a of the pinion gear 31 and the rack teeth 41 come into contact can be suppressed. Further, by bringing the two rack teeth 41 into contact with both surfaces of the gear 31a of the pinion gear 31, play between the pinion gear 31 and the rack bar 40 can be reduced, and the steering feeling during steering can be improved.

[0073] In addition, since the number of rack teeth 41 that are simultaneously in contact with the pinion gear 31 is 4 or less, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that are simultaneously in contact with the pinion gear 31 can be reduced, and fluctuations in steering resistance during steering can be reduced. As a result, changes in steering resistance during steering can be suppressed, impact noise can be suppressed, and the steering feeling can be improved.

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

[0075] For example, when the vehicle equipped with the steering device 1 is relatively small and lightweight, and the load on the rack teeth 41 during steering is small, the force acting between the rack teeth 41 and the pinion gear 31 is unlikely to increase even near the maximum steering angle. In such a case, since the stress on the rack teeth 41 is unlikely to increase even near the maximum steering angle, wide pitch portions 46 may be provided at both ends in the rack tooth arrangement range 44 without providing the narrow pitch portions 45. Thus, when the load on the rack teeth 41 is small even near the maximum steering angle, by making the areas near both ends in the rack tooth arrangement range 44 also wide pitch portions 46, it is possible to improve the responsiveness when steering at a large steering angle and improve the steering feeling.

[0076] Also, in the above-described embodiment, the rack teeth 41 located in the narrow pitch portion 45 have the tooth thickness change 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 change portion 42. However, 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 other forms.

[0077] FIG. 10 is an explanatory view showing a modified example of the steering device 1 according to the embodiment, and shows a form in which the tooth thickness change portion 42 is formed on one surface of the rack teeth 41 arranged in the wide pitch portion 46. FIG. 11 is an explanatory view showing a modified example of the steering device 1 according to the embodiment, and shows a form in which the tooth thickness change portion 42 is formed on both surfaces of the rack teeth 41 arranged in the narrow pitch portion 45. The rack teeth 41 located in the wide pitch portion 46 may have, for example, as shown in FIG. 10, the tooth thickness change portion 42 on one surface in the tooth thickness direction T, and the other surface may be a flat portion 41a. The rack teeth 41 located in the narrow pitch portion 45 may have, for example, as shown in FIG. 11, the tooth thickness change portions 42 on both surfaces in the tooth thickness direction T. That is, the rack teeth 41 located in the wide pitch portion 46 may have crowning 43 as the tooth thickness change portion 42 on one surface in the tooth thickness direction T, and the rack teeth 41 located in the narrow pitch portion 45 may have crowning 43 as the tooth thickness change portions 42 on both surfaces in the tooth thickness direction T.

[0078] In this way, by forming the tooth thickness change portion 42 on one side of the rack teeth 41 located in the wide pitch portion 46 and forming the tooth thickness change portion 42 on both sides of the rack teeth 41 located in the narrow pitch portion 45, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that come into contact with the pinion gear 31 simultaneously can be reduced.

[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 having more surfaces on which the tooth thickness change portion 42 is 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 having fewer surfaces on which the tooth thickness change portion 42 is formed than the rack teeth 41 located in the narrow pitch portion 45.

[0080] As a result, the difference between the maximum number of teeth and the minimum number of teeth of the rack teeth 41 that come into contact with the pinion gear 31 simultaneously can be reduced throughout the rack tooth arrangement range 44, and the variation in steering resistance during steering can be reduced. As a result, without reducing the rigidity of the rack bar 40, the change in steering resistance during steering can be suppressed.

[0081] Also, in the above-described embodiment, the tooth thickness change portion 42 of the rack teeth 41 is formed by crowning 43, but the tooth thickness change portion 42 may be formed by other means than crowning 43. The tooth thickness change portion 42 may be, for example, a so-called end relief in which the tooth thickness near the center in the tooth width direction W of the rack teeth 41 is constant and 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. As long as the tooth thickness at the end in the tooth width direction W of the rack teeth 41 is formed to be smaller than the tooth thickness at the center in the tooth width direction W, the form thereof is not limited.

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

Explanation of Signs

[0083] 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 part 42 Tooth thickness change part 43 Crowning 44 Rack tooth arrangement range 45 Narrow pitch part 46 Wide pitch part 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 pinion gear having helical teeth, A rack bar having a plurality of helical rack teeth meshing with the pinion gear, Comprising, The rack teeth have a wide pitch portion where a plurality of the rack teeth are arranged at a predetermined pitch, and a narrow pitch portion where the pitch of a 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, 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. A steering device.

2. A pinion gear having helical teeth, A rack bar having a plurality of helical rack teeth meshing with the pinion gear, Comprising, The rack teeth have a wide pitch portion where a plurality of the rack teeth are arranged at a predetermined pitch, and a narrow pitch portion where the pitch of a 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, The rack teeth located in the narrow pitch portion have the tooth thickness change portion on both surfaces in the tooth thickness direction. A steering device.

3. The steering device according to claim 1 or 2, wherein the tooth thickness change portion is a crowning where 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 narrow pitch portion is arranged at the center and both ends in the range where a plurality of the rack teeth are arranged in the longitudinal direction of the rack bar, The steering device according to claim 1 or 2, wherein the wide pitch portion is arranged between the center and both ends of the narrow pitch portions in the longitudinal direction of the rack bar.

5. The narrow pitch portion is arranged at the center in the range where a plurality of the rack teeth are arranged in the longitudinal direction of the rack bar, The steering device according to claim 1 or 2, wherein the wide pitch portion is arranged on both sides of the narrow pitch portion in the longitudinal direction of the rack bar.

6. The steering device according to claim 1 or 2, 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.

Images