Steering gear

Abstract

To provide a steering device which can achieve both of ensuring durability and weight saving of a rack housing.SOLUTION: A steering device comprises: a rack bar 30 having a large diameter part 31 and a small diameter part 41 which have maximum widths different from each other in a direction orthogonal to a longer direction; a rack housing 10 that has a large diameter housing part 11 in which a large diameter open hole 12 is formed, and a small diameter housing part 21 in which a small diameter open hole 22, which communicates with the large diameter open hole 12 and has a diameter smaller than the large diameter open hole 12, is formed, and that stores the rack bar 30; ball joints 50 located respectively at both ends of the rack bar 30; and a stopper ring 60 that has a modulus of longitudinal elasticity higher than that of the rack housing 10, is formed in a substantially toric shape, and is located at an end of the large diameter open hole 12 opposite to a side on which the small diameter open hole 22 is positioned. The large diameter open hole 12 stores the large diameter part 31 of the rack bar 30, and the small diameter open hole 22 stores the small diameter part 41 of the rack bar 30.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] A steering device includes a pinion gear that rotates due to the rotational torque generated when the steering wheel is steered, a rack bar with rack teeth that mesh with the pinion gear, a rack housing inside which the rack bar is located, and a ball joint located at the end of the rack bar. In the steering device, the pinion gear rotates due to the steering force of the driver, and the rack bar moves linearly in response to the rotation of the pinion gear, thereby moving the tires via tie rods and knuckle arms connected to the ball joint, thereby enabling steering. In addition, an electric power steering device, which is one example of a steering device, has an electric motor that generates an assist force that supplements the steering force, and the assist force generated by the electric motor is used to linearly move the rack bar, thereby assisting the steering force of the driver.

[0003] Among conventional steering devices equipped with a rack bar that moves linearly during steering, some have rack bar thicknesses that vary depending on the location in the longitudinal direction of the rack bar. For example, in the electric power steering device described in Patent Document 1, the diameter of the rack bar, or the width of the rack bar in a direction perpendicular to the direction in which the rack bar extends, is different between the portion of the rack bar where the rack teeth are formed and the portion other than the portion where the rack teeth are formed.

[0004] Furthermore, some conventional steering devices equipped with a rack bar are provided with a member that cushions the ball joint and the rack housing when the rack bar moves to the end position of its linear motion range. For example, in the steering device described in Patent Document 2, a stopper member and a cushioning member are provided on the ball joint, and the cushioning member and stop member are abutted against fixed members arranged near the end of the rack housing, thereby cushioning the ball joint and the rack housing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-27313 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-80147 Summary of the Invention [Problem to be solved by the invention]

[0006] When the thickness of the rack bar is varied depending on the position in the longitudinal direction of the rack bar, it is possible to vary the size of the rack housing depending on the thickness of the rack bar in order to prevent the rack housing from being formed to be unnecessarily large relative to the rack bar. For this reason, in Patent Document 1 as well, the diameter of the rack housing is larger in the wider portions of the rack bar than in the narrower portions of the rack bar.

[0007] On the other hand, it is desirable to make the maximum diameter of the rack housing as small as possible from the viewpoint of reducing the weight and size of the steering device, etc. Therefore, if the diameter of the rack housing is made to vary depending on the position in the longitudinal direction of the rack housing, the inner diameter will be larger in the larger diameter portion of the rack housing, while the outer diameter will be limited.

[0008] However, if the inner diameter of the large-diameter portion of the rack housing is increased while the outer diameter is limited, it becomes difficult to ensure the radial thickness of the members forming the rack housing, making it difficult to ensure the strength of the rack housing in the large-diameter portion of the rack housing. As a result, it becomes difficult to ensure the durability of the ball joint arranged at the end of the rack bar in the large-diameter portion of the rack housing when it abuts against the end of the rack housing. For this reason, in steering devices in which the diameter of the rack housing varies depending on the position in the longitudinal direction of the rack housing for the purpose of reducing weight and size, there is room for improvement in terms of the durability of the rack housing.

[0009] The present disclosure has been made in view of the above, and aims to provide a steering device that can achieve both weight reduction and durability of the rack housing. [Means for solving the problem]

[0010] The steering device of the present disclosure includes a rack bar having a large diameter portion and a small diameter portion that are different from each other in maximum width in a direction perpendicular to the longitudinal direction, a large diameter housing portion in which a large diameter through hole is formed, and a small diameter housing portion in which a small diameter through hole that is in communication with the large diameter through hole and has a diameter smaller than that of the large diameter through hole is formed, and the rack housing stores the rack bar in an internal space between the large diameter through hole and the small diameter through hole such that axial directions of the large diameter through hole and the small diameter through hole coincide with the longitudinal direction of the rack bar, ball joints that are respectively arranged at both ends of the rack bar, and a front and a stopper ring having a higher modulus of longitudinal elasticity than the rack housing, formed in a substantially circular ring shape, and disposed at the end of the large-diameter through-hole opposite to the side where the small-diameter through-hole is located, wherein the ball joint abuts against the rack housing or the stopper ring, and the ball joint abutting against the rack housing and the ball joint abutting against the stopper ring have the same shape at the abutment point, the large-diameter through-hole houses the large-diameter portion of the rack bar, and the small-diameter through-hole houses the small-diameter portion of the rack bar.

[0011] According to this configuration, by disposing a stopper ring at the end of the large-diameter through hole, when the rack bar is moved toward the small-diameter portion, the ball joint disposed at the end of the rack bar near the large-diameter portion abuts against the stopper ring, thereby restricting the movement of the rack bar. Therefore, the large-diameter through hole, which makes it difficult to ensure a sufficient area for the ball joint to abut against, allows the ball joint to abut against the stopper ring, which has a high Young's modulus, in the large-diameter housing portion of the rack housing, where stress is likely to be large due to the large diameter of the through hole. Therefore, the durability of the rack housing can be ensured when restricting the movement of the rack bar by abutting the ball joint against the rack housing. Furthermore, when ensuring the durability of the rack housing when abutting the ball joint, the stopper ring with a high Young's modulus is disposed without increasing the outer diameter of the large-diameter housing portion, thereby suppressing an increase in the weight of the rack housing. As a result, it is possible to achieve both a lightweight rack housing and ensure durability.

[0012] In a preferred embodiment, when the rack bar is moved in the direction where the large diameter portion is located, the ball joint arranged at the end of the rack bar on the small diameter portion side comes into contact with the position of the end of the small diameter through hole in the small diameter housing portion of the rack housing, thereby restricting movement of the rack bar in the direction where the large diameter portion is located, and when the rack bar is moved in the direction where the small diameter portion is located, the ball joint arranged at the end of the rack bar on the large diameter portion side comes into contact with the stopper ring, thereby restricting movement of the rack bar in the direction where the small diameter portion is located.

[0013] According to this configuration, in the small-diameter housing portion of the rack housing, where it is easy to ensure the thickness of the portion where the ball joint contacts, the portion where the ball joint contacts can be ensured without disposing a stopper ring, thereby reducing the weight of the rack housing. Also, in the large-diameter housing portion, where it is difficult to ensure the thickness of the portion where the ball joint contacts, the ball joint is abutted against the stopper ring, thereby reducing damage to the rack housing due to impact from the ball joint. As a result, it is possible to achieve both weight reduction and durability of the rack housing.

[0014] In the above steering device, the opposing area between the ball joint arranged on the large diameter side of the rack bar and the stopper ring when they are in contact with each other is smaller than the opposing area between the ball joint arranged on the small diameter side of the rack bar and the rack housing when they are in contact with each other at the end of the small diameter housing portion of the rack housing.

[0015] With this configuration, the opposing area between the ball joint and the stopper ring on the large diameter portion of the rack bar when they are in contact with each other is small, which tends to increase the surface pressure at the contact area, but the stopper ring with which the ball joint on the large diameter portion is in contact has a higher modulus of longitudinal elasticity than the rack housing. Therefore, the small opposing area with the ball joint ensures durability when the ball joint comes into contact with the large diameter housing portion of the rack housing, which tends to experience high surface pressure. As a result, the rack housing can be made both lightweight and durable.

[0016] In the above steering device, the shape of the portion of the ball joint that abuts against the stopper ring has a pair of opposite sides that are parallel to each other when viewed in the axial direction, and the inner diameter of the stopper ring is larger than the two-face width of the pair of opposite sides of the ball joint and smaller than the maximum width of the portion of the ball joint that abuts against the stopper ring in a direction perpendicular to the axial direction.

[0017] With this configuration, when the ball joint abuts against the stopper ring, localized stress is likely to occur in the stopper ring, but because the stopper ring has a higher modulus of longitudinal elasticity than the rack housing, strength can be ensured even if localized stress occurs in the stopper ring. This ensures the durability of the stopper ring, and makes it possible to achieve both weight reduction and durability of the rack housing.

[0018] In a preferred embodiment, a rack bush made of a resin material and supporting the rack bar is arranged in the large diameter through hole closer to the small diameter through hole than the stopper ring, and the rack bush is formed in a substantially cylindrical shape and is arranged at a distance in the axial direction from the stopper ring.

[0019] With this configuration, the rack bushing is disposed axially apart from the stopper ring, which prevents the force from the ball joint from being transmitted to the rack bushing when the ball joint abuts against the stopper ring. This prevents the rack bushing, which is made of a resin material and therefore has lower strength than the stopper ring, from being compressed in the axial direction and being damaged. As a result, the durability of the components disposed in the rack housing can be improved.

[0020] In a preferred embodiment, the rack bush has a stopper that protrudes radially outward on its outer peripheral surface, and the stopper fits into a groove formed on the inner peripheral surface of the large-diameter through hole, thereby restricting axial movement relative to the rack housing.

[0021] With this configuration, the axial movement of the rack bushing 70 is restricted by the movement stopper formed on the outer peripheral surface, preventing the rack bushing from moving toward the stopper ring. This prevents the force acting on the stopper ring from the ball joint from being transmitted from the stopper ring to the rack bushing, preventing the rack bushing from being compressed in the axial direction and being damaged. As a result, the durability of the components arranged in the rack housing can be improved.

[0022] Preferably, the stopper ring is press-fitted into the large-diameter housing portion.

[0023] With this configuration, the stopper ring is press-fit into the large-diameter housing portion, thereby reducing the clearance between the rack bar and the stopper ring. This increases the opposing area between the ball joint and the stopper ring, thereby reducing the surface pressure between the ball joint and the stopper ring. This ensures the durability of the stopper ring, and allows the rack housing to be both lightweight and durable.

[0024] In a preferred embodiment, the rack housing has an outer diameter of at least a part of the small diameter housing portion that is smaller than an outer diameter of the large diameter housing portion.

[0025] With this configuration, the outer diameter of at least a part of the small-diameter housing portion of the rack housing is smaller than the outer diameter of the large-diameter housing portion, which allows the weight of the small-diameter housing portion of the rack housing to be reduced, thereby reducing the weight of the rack housing.

[0026] In a preferred embodiment, the small diameter through-hole of the rack housing has a minimum diameter smaller than the maximum width of the large diameter portion of the rack bar.

[0027] With this configuration, the small diameter through hole of the rack housing has a minimum diameter smaller than the maximum width of the large diameter portion of the rack bar, which allows the small diameter housing portion of the rack housing to be made lighter, thereby reducing the weight of the rack housing. [Effects of the Invention]

[0028] The steering device according to the present disclosure has the effect of being able to achieve both weight reduction and durability of the rack housing. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic diagram for explaining a steering device according to an embodiment. [Figure 2] FIG. 2 is a perspective view of a main part of the steering device according to the embodiment. [Figure 3] FIG. 3 is a plan view of the rack bar shown in FIG. 2, showing the steering rack teeth from the front. [Figure 4] FIG. 4 is a plan view of the rack bar shown in FIG. 2, showing the assist rack teeth as viewed from the front. [Figure 5] 5 is a perspective view of the rack bar including the cross section AA of FIG. [Figure 6] FIG. 6 is a cross-sectional view of a rack housing and a rack bar of the steering device. [Figure 7] FIG. 7 is a detailed view of part B in FIG. [Figure 8] FIG. 8 is a detailed view of part C in FIG. [Figure 9] FIG. 9 is an explanatory diagram showing a comparison of the shapes of the stopper ring and the ball joint in the FF direction of FIG. [Figure 10] FIG. 10 is an explanatory diagram showing a state in which the movement of the rack bar is restricted when the rack bar moves in the direction in which the large diameter portion is located. [Figure 11] FIG. 11 is a detailed view of part D in FIG. [Figure 12]FIG. 12 is an explanatory diagram showing a state in which the movement of the rack bar is restricted when the rack bar moves in the direction in which the small diameter portion is located. [Figure 13] FIG. 13 is a detailed view of part E in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0030] 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.

[0031] [Embodiment] FIG. 1 is a schematic diagram for explaining a steering device 80 according to an embodiment. FIG. 2 is a perspective view of a main part of the steering device 80 according to the embodiment. Note that FIG. 2 omits the illustration of an electric motor 102 and a second pinion gear 92 in order to illustrate the rack bar 30. As shown in FIG. 1, the steering device 80 includes, in the order in which a force applied by an operator is transmitted, a steering wheel 81, a steering shaft 82, a universal joint 84, an intermediate shaft 85, a universal joint 86, a stub shaft 87, a steering gear 90, and a tie rod 93. The steering device 80 also includes a control device (hereinafter referred to as an ECU (Electronic Control Unit)) 100, a torque sensor 101, and an electric motor 102. A vehicle speed sensor 103 is provided in the vehicle and outputs a vehicle speed signal V to the ECU 100 via CAN (Controller Area Network) communication.

[0032] The steering shaft 82 is connected to the steering wheel 81 at one end and to a universal joint 84 at the other end.

[0033] Intermediate shaft 85 is connected at one end to universal joint 84 and at the other end to universal joint 86. Stub shaft 87 is connected at one end to universal joint 86 and at the other end to torque sensor 101. Torque sensor 101 is connected at one end to stub shaft 87 and at the other end to first pinion gear 91 of steering gear 90.

[0034] More specifically, first pinion gear 91 is a shaft-shaped member having a gear 91a (see FIG. 7) formed on the end opposite to the side connected to stub shaft 87, which gear 91a meshes with rack bar 30, which will be described later, and stub shaft 87 and first pinion gear 91 are connected via a torsion bar (not shown). One end of the torsion bar is connected to stub shaft 87, and the other end is connected to first pinion gear 91, and the torsion bar transmits rotational torque between stub shaft 87 and first pinion gear 91.

[0035] Torque sensor 101 is a torque detection device that detects torque acting on a shaft connected to torque sensor 101, and detects rotational torque transmitted between stub shaft 87 and first pinion gear 91 via a torsion bar. In other words, stub shaft 87 and first pinion gear 91, which are connected via a torsion bar, are shafts that are the detection target when torque is detected by torque sensor 101.

[0036] The steering gear 90 includes a first pinion gear 91, a rack bar 30, and a second pinion gear 92. The first pinion gear 91 is connected to the stub shaft 87 via a torsion bar. The rack bar 30 has steering rack teeth 44 (see FIG. 3) that mesh with a gear 91a (see FIG. 7) of the first pinion gear 91. The rack bar 30 also meshes with the second pinion gear 92 at a position different from that of the first pinion gear 91.

[0037] An electric motor 102 is connected to the second pinion gear 92 via a worm reduction gear 94 (see FIG. 6), and the second pinion gear 92 is rotated by a driving force transmitted from the electric motor 102. The electric motor 102 rotates the second pinion gear 92 via the worm reduction gear 94. The electric motor 102 is, for example, a brushless motor, but may also be a motor including brushes (sliders) and a commutator (commutator).

[0038] The steering gear 90 converts the rotational motion transmitted to the first pinion gear 91 and the second pinion gear 92 into linear motion by the rack bar 30 disposed inside the rack housing 10. The steering device 80 according to this embodiment is of a dual pinion assist type in which the rack bar 30 performs linear motion by the rotational motion transmitted from the first pinion gear 91 and the second pinion gear 92. The tie rod 93 is connected to the rack bar 30. In other words, the steering device 80 is a rack-and-pinion type electric power steering device.

[0039] The torque sensor 101 detects the steering force of the driver transmitted to the steering shaft 82 via the steering wheel 81 as a steering torque. The vehicle speed sensor 103 detects the traveling speed (vehicle speed) of the vehicle on which the steering device 80 is mounted. The electric motor 102, the torque sensor 101, and the vehicle speed sensor 103 are electrically connected to the ECU 100.

[0040] The ECU 100 controls the operation of the electric motor 102. The ECU 100 also acquires signals from a torque sensor 101 and a vehicle speed sensor 103. That is, the ECU 100 acquires a steering torque T from the torque sensor 101 and a vehicle speed signal V of the vehicle from the vehicle speed sensor 103. When an ignition switch 104 is in an on state, the ECU 100 is supplied with power from a power supply device (for example, an on-board battery) 105. The ECU 100 calculates an assist steering command value of an assist command based on the steering torque T and the vehicle speed signal V. The ECU 100 then adjusts the power value X to be supplied to the electric motor 102 based on the calculated assist steering command value. The ECU 100 acquires, as operation information Y, information on an induced voltage from the electric motor 102 or information output from a rotation detection device such as a resolver provided in the electric motor 102.

[0041] The steering force of the operator (driver) input to the steering wheel 81 is transmitted to the first pinion gear 91. The steering force transmitted to the first pinion gear 91 is transmitted to the tie rod 93 via the steering gear 90, displacing the wheels.

[0042] Furthermore, the steering force input by the operator to the steering wheel 81 is transmitted to a torque sensor 101 arranged in a steering force transmission path from the steering wheel 81 to the first pinion gear 91. At this time, the ECU 100 acquires the steering torque T from the torque sensor 101 and acquires the vehicle speed signal V from the vehicle speed sensor 103. Then, the ECU 100 controls the operation of the electric motor 102. The auxiliary steering torque generated by the electric motor 102 is transmitted to the second pinion gear 92.

[0043] The assist steering torque transmitted to the second pinion gear 92 is transmitted to the tie rod 93 via the steering gear 90, displacing the wheels. That is, the steering device 80 displaces the wheels using not only the steering force of the operator transmitted to the rack bar 30 via the first pinion gear 91, but also the assist steering torque of the electric motor 102 transmitted to the rack bar 30 via the second pinion gear 92. The steering device 80 according to this embodiment is a dual pinion type electric power steering device in which an assist force is applied to the second pinion gear 92 in this way.

[0044] 3 is a plan view of the rack bar 30 shown in FIG. 2 , showing the steering rack teeth 44 as viewed from the front. FIG. 4 is a plan view of the rack bar 30 shown in FIG. 2 , showing the assist rack teeth 34 as viewed from the front. The rack bar 30 has a large diameter portion 31 and a small diameter portion 41 that have different maximum widths in a direction perpendicular to the longitudinal direction of the rack bar 30. The large diameter portion 31 has a maximum width Wa in a direction perpendicular to the longitudinal direction of the rack bar 30 that is larger than the maximum width Wb of the small diameter portion 41 in a direction perpendicular to the longitudinal direction of the rack bar 30. The large diameter portion 31 and the small diameter portion 41 are connected to each other in the longitudinal direction of the rack bar 30. The large diameter portion 31 and the small diameter portion 41 are joined by, for example, friction welding. In this embodiment, the large diameter portion 31 and the small diameter portion 41 have approximately the same length in the longitudinal direction of the rack bar 30.

[0045] Steering rack teeth 44 that mesh with gear 91a (see FIG. 7) of first pinion gear 91 are formed on small diameter portion 41. In small diameter portion 41, steering rack teeth 44 are formed on small diameter round bar portion 42 that is a round bar. Therefore, the maximum width Wb of small diameter portion 41 in the direction perpendicular to the longitudinal direction of rack bar 30 is equal to the diameter of small diameter round bar portion 42.

[0046] Assist rack teeth 34 that mesh with the second pinion gear 92 are formed on the large diameter portion 31. The assist rack teeth 34 formed on the large diameter portion 31 are formed facing in a different direction from the steering rack teeth 44 formed on the small diameter portion 41. The large diameter portion 31 has a large diameter round bar portion 32 that is shaped like a round bar and has a larger diameter than the small diameter round bar portion 42, and an assist rack tooth forming portion 33 on which the assist rack teeth 34 are formed. The large diameter round bar portion 32 is arranged on both sides of the assist rack tooth forming portion 33 in the longitudinal direction of the rack bar 30. The assist rack tooth forming portion 33 is formed so that its maximum width Wa in a direction perpendicular to the axial direction of the large diameter round bar portion 32 is larger than the diameter of the large diameter round bar portion 32.

[0047] Figure 5 is a perspective view of the rack bar 30 including the cross section AA of Figure 4. The assist rack tooth forming portion 33 of the large diameter portion 31 of the rack bar 30 is formed by crushing the surface of the large diameter round bar portion 32 on which the assist rack teeth 34 are formed in a direction perpendicular to the axial direction of the large diameter round bar portion 32. The assist rack teeth 34 are formed on the surface of the large diameter round bar portion 32 that has been crushed into a flat shape in this way.

[0048] Furthermore, since the assist rack tooth forming portion 33 is formed by crushing the large diameter round bar portion 32 in only one direction, the surface of the assist rack tooth forming portion 33 opposite to the surface where the assist rack teeth 34 are formed is formed in a shape that is continuous with the large diameter round bar portions 32 located on both sides of the assist rack tooth forming portion 33. In other words, the back surface 35, which is the surface of the assist rack tooth forming portion 33 opposite to the surface where the assist rack teeth 34 are formed, is formed in an arc shape when viewed in the longitudinal direction of the rack bar 30, with a radius of curvature that is substantially the same as the radius of curvature of the outer peripheral surface of the large diameter round bar portion 32.

[0049] Furthermore, by compressing the large diameter round bar portion 32 in only one direction, the width of the assist rack tooth forming portion 33 in the direction in which the large diameter round bar portion 32 is compressed, i.e., in a direction perpendicular to both the normal direction of the surface on which the assist rack teeth 34 are formed and the longitudinal direction of the rack bar 30, is larger than the diameter of the large diameter round bar portion 32. As a result, the maximum width Wa of the assist rack tooth forming portion 33 in a direction perpendicular to the axial direction of the large diameter round bar portion 32 is larger than the diameter of the large diameter round bar portion 32. The maximum width Wa of the assist rack tooth forming portion 33 formed in this manner is the maximum width Wa of the large diameter portion 31 in the direction perpendicular to the longitudinal direction of the rack bar 30.

[0050] The assist rack teeth 34 are thus formed in the assist rack tooth forming portion 33 whose maximum width Wa is greater than the diameter of the large diameter round bar portion 32. This allows the length of the assist rack teeth 34 to be longer compared to when the assist rack teeth 34 are formed directly on the large diameter round bar portion 32. Furthermore, because the assist rack teeth 34 are thus formed in the assist rack tooth forming portion 33 of the large diameter portion 31, the length of the teeth is longer than the length of the steering rack teeth 44 formed on the small diameter portion 41.

[0051] 6 is a cross-sectional view of the rack housing 10 and rack bar 30 of the steering device 80. The rack bar 30 is stored in the rack housing 10. The rack housing 10 has a large diameter housing portion 11 in which a large diameter through hole 12 is formed, and a small diameter housing portion 21 in which a small diameter through hole 22 that communicates with the large diameter through hole 12 and has a diameter smaller than that of the large diameter through hole 12 is formed. The large diameter housing portion 11 and the small diameter housing portion 21 are each formed in a substantially cylindrical shape and are connected to each other in the axial direction.

[0052] The large diameter through holes 12 and the small diameter through holes 22 formed in the rack housing 10 are formed with a slight taper in diameter. Specifically, the large diameter through holes 12 and the small diameter through holes 22 have the smallest diameter at the portion where they are connected, and have a taper in which the diameters increase as they move away from each other in the axial direction. The large diameter through holes 12 and the small diameter through holes 22 also have different diameters at the portion where they are connected, so a step is formed at the connection portion between the large diameter through holes 12 and the small diameter through holes 22.

[0053] The minimum diameter of the large diameter through-hole 12 of the rack housing 10 formed in this manner is larger than the maximum width Wa of the large diameter portion 31 of the rack bar 30. In addition, the minimum diameter of the small diameter through-hole 22 of the rack housing 10 is larger than the maximum width Wb of the small diameter portion 41 of the rack bar 30.

[0054] The large diameter housing portion 11 and the small diameter housing portion 21 of the rack housing 10, in which the large diameter through-holes 12 and the small diameter through-holes 22 of different diameters are formed, also have different outer diameters, with most of the large diameter housing portion 11 having a larger outer diameter than the small diameter housing portion 21. In other words, in the rack housing 10, the outer diameter of at least a part of the small diameter housing portion 21 is smaller than the outer diameter of the large diameter housing portion 11.

[0055] The rack housing 10 stores the rack bar 30 in the internal space between the large diameter through hole 12 and the small diameter through hole 22, with the axial direction of the large diameter through hole 12 and the small diameter through hole 22 aligned with the longitudinal direction of the rack bar 30. When storing the rack bar 30 in the rack housing 10, the rack bar 30 is stored in an orientation such that the large diameter portion 31 of the rack bar 30 is positioned on the large diameter housing portion 11 side of the rack housing 10, and the small diameter portion 41 of the rack bar 30 is positioned on the small diameter housing portion 21 side of the rack housing 10. Therefore, the large diameter through hole 12 of the rack housing 10 mainly stores the large diameter portion 31 of the rack bar 30, and the small diameter through hole 22 of the rack housing 10 mainly stores the small diameter portion 41 of the rack bar 30.

[0056] The small diameter through-hole 22 of the rack housing 10 that houses the small diameter portion 41 of the rack bar 30 has a minimum diameter that is smaller than the maximum width Wa of the large diameter portion 31 of the rack bar 30. In other words, the maximum width Wa of the large diameter portion 31 of the rack bar 30 is larger than the minimum diameter of the small diameter through-hole 22 of the rack housing 10. Furthermore, the small diameter through-hole 22 of the rack housing 10 has a minimum diameter that is smaller than the diameter of the large diameter round bar portion 32 of the large diameter portion 31 of the rack bar 30.

[0057] A ball joint accommodating portion 15 is formed in the large diameter housing portion 11 of the rack housing 10 at an end opposite to the side where the small diameter housing portion 21 is located. The ball joint accommodating portion 15 formed in the large diameter housing portion 11 is formed in a substantially cylindrical shape with an inner diameter larger than the inner diameter of the large diameter through hole 12 and an outer diameter larger than the outer diameter of the portion of the large diameter housing portion 11 where the large diameter through hole 12 is formed. The ball joint accommodating portion 15 formed in this manner protrudes beyond the portion of the large diameter housing portion 11 where the large diameter through hole 12 is formed on the side opposite to the side where the small diameter housing portion 21 is located, and is oriented so that its axis coincides with the axis of the large diameter through hole 12.

[0058] Similarly, a ball joint accommodating portion 25 is formed in the small diameter housing portion 21 of the rack housing 10 at an end opposite to the side where the large diameter housing portion 11 is located. The ball joint accommodating portion 25 formed in the small diameter housing portion 21 is formed in a substantially cylindrical shape with an inner diameter larger than the inner diameter of the small diameter through hole 22 and an outer diameter larger than the outer diameter of the portion of the small diameter housing portion 21 where the small diameter through hole 22 is formed. The ball joint accommodating portion 25 formed in this way protrudes to the side opposite to the side where the large diameter housing portion 11 is located beyond the portion of the small diameter housing portion 21 where the small diameter through hole 22 is formed, and is oriented so that its axis coincides with the axis of the small diameter through hole 22.

[0059] A ball joint 50 is disposed at each end of the rack bar 30 stored in the rack housing 10. That is, a ball joint 50 is disposed at each end 36 of the large diameter portion 31 of the rack bar 30 and at each end 46 of the small diameter portion 41 of the rack bar 30. The ball joint 50 has a threaded portion 54 formed by a male thread, and a threaded hole 37 is formed in the end 36 of the large diameter portion 31 and a threaded hole 47 is formed in the end 46 of the small diameter portion 41. Therefore, by threading the threaded portion 54 of the ball joint 50 into the threaded hole 37 in the end 36 of the large diameter portion 31 and the threaded hole 47 in the end 46 of the small diameter portion 41, respectively, the ball joint 50 is disposed at each end 36 of the large diameter portion 31 and the end 46 of the small diameter portion 41 of the rack housing 10.

[0060] In this way, the ball joints 50 arranged at both ends of the rack bar 30 abut against the rack housing 10 or a stopper ring 60 (described later), and the ball joints 50 abutting against the rack housing 10 and the ball joints 50 abutting against the stopper ring 60 have the same shape at the abutment points. Specifically, the maximum width of the ball joints 50 in a direction perpendicular to the axial direction is larger than the diameter of the portion of the rack bar 30 where the ball joints 50 are arranged. In other words, the maximum width of the ball joints 50 arranged at the end 36 of the large diameter portion 31 of the rack bar 30 in a direction perpendicular to the axial direction is larger than the diameter of the end 36 of the large diameter portion 31 of the rack bar 30. Similarly, the maximum width of the ball joints 50 arranged at the end 46 of the small diameter portion 41 of the rack bar 30 in a direction perpendicular to the axial direction is larger than the diameter of the end 46 of the small diameter portion 41 of the rack bar 30.

[0061] Furthermore, the ball joint 50 disposed at the end 36 of the large diameter portion 31 of the rack bar 30 has a maximum width in a direction perpendicular to the axial direction that is larger than the inner diameter of a stopper ring 60 (described later) that is disposed at the end of the large diameter through hole 12 of the rack housing 10. Moreover, the ball joint 50 disposed at the end 46 of the small diameter portion 41 of the rack bar 30 has a maximum width in a direction perpendicular to the axial direction that is larger than the inner diameter of the small diameter through hole 22 of the rack housing 10.

[0062] Furthermore, ball joints 50 disposed at both ends of rack bar 30 have joint portions 51 formed on the side opposite to the side where threaded portions 54 of ball joints 50 are located. Joint portions 51 are formed in a recessed shape that is recessed from the part of ball joint 50 opposite to the side where threaded portions 54 are located. An end of a tie rod 93 (see FIG. 1) can fit into joint portion 51. This allows tie rod 93 to be connected to ball joints 50, and tie rod 93 is connected to rack bar 30 via ball joints 50.

[0063] Furthermore, a gear box 16 of a worm reduction gear 94 is provided in the large diameter housing portion 11 of the rack housing 10. A second pinion gear 92 (see FIG. 1 ), a worm wheel 95 that transmits the driving force generated by the electric motor 102 to the second pinion gear 92, and the like are arranged within the gear box 16. The second pinion gear 92 is arranged to mesh with assist rack teeth 34 formed on the assist rack tooth forming portion 33 of the large diameter portion 31 of the rack bar 30. As a result, the second pinion gear 92 can transmit the driving force generated by the electric motor 102 and transmitted via the worm wheel 95 to the assist rack teeth 34, and can transmit the driving force generated by the electric motor 102 to the rack bar 30.

[0064] 7 is a detailed view of portion B in FIG. 6. The rack housing 10 supports the first pinion gear 91 on the small diameter housing portion 21 side, with the first pinion gear 91 meshing with the steering rack teeth 44 formed on the small diameter portion 41 of the rack bar 30. A through hole 26 is formed in the small diameter housing portion 21 of the rack housing 10 at a position opposite to the side on which the steering rack teeth 44 of the rack bar 30 are formed. A pressing member 96, a spring 97, and a sealing member 98 are housed in the through hole 26. The pressing member 96 abuts against the rack bar 30 from the side opposite to the side on the rack bar 30 where the first pinion gear 91 is located. The sealing member 98 is disposed at the opening of the through hole 26 and seals the opening.

[0065] The spring 97 is made of a compression spring, and is disposed between the sealing member 98 and the pressing member 96 in a state in which it is compressed between the sealing member 98 and the pressing member 96. Therefore, the pressing member 96 is pressed against the rack bar 30 by the biasing force of the spring 97, and the surface of the rack bar 30 on which the steering rack teeth 44 are formed is pressed against the gear 91 a of the first pinion gear 91 by the biasing force of the pressing member 96. This maintains the rack bar 30 in a state in which the steering rack teeth 44 mesh with the gear 91 a of the first pinion gear 91.

[0066] 8 is a detailed view of portion C in FIG. 6. A stopper ring 60 is disposed in the large-diameter housing portion 11 of the rack housing 10 at the end 13 opposite the side of the large-diameter through-hole 12 where the small-diameter through-hole 22 is located. The stopper ring 60 is not disposed in the small-diameter housing portion 21 of the rack housing 10, but is disposed only in the large-diameter housing portion 11. The stopper ring 60 is formed in a substantially annular shape and has a higher modulus of longitudinal elasticity than the rack housing 10. For example, the rack housing 10 is made of aluminum or a magnesium alloy, and the stopper ring 60 is made of iron. As a result, the stopper ring 60 is formed of a material with a higher modulus of longitudinal elasticity than the material from which the rack housing 10 is formed.

[0067] The stopper ring 60, which is formed in an annular shape, has an inner diameter that is approximately the same as the diameter of the large-diameter through-hole 12. The stopper ring 60 is arranged in a direction such that its axial direction coincides with the axial direction of the large-diameter through-hole 12, and is in contact with the end portion 13 of the large-diameter housing portion 11 of the rack housing 10, where the large-diameter through-hole 12 forms an opening that opens toward the inside of the ball joint accommodating portion 15.

[0068] The stopper ring 60 is press-fit into the large diameter housing portion 11 of the rack housing 10. More specifically, the inner circumferential surface of the ball joint accommodating portion 15 formed in the large diameter housing portion 11 of the rack housing 10 has a fitting portion 15a, which is a portion whose inner diameter is approximately the same as the outer diameter of the stopper ring 60, located near the large diameter through hole 12. The stopper ring 60 is press-fit into the fitting portion 15a formed on the inner circumferential surface of the ball joint accommodating portion 15 of the large diameter housing portion 11, and is arranged by being in contact with the end portion 13 that forms the opening of the large diameter through hole 12.

[0069] The rack bar 30 stored in the rack housing 10 is capable of moving axially relative to the rack housing 10, and the stopper ring 60 is the portion that comes into contact with the ball joint 50, which is arranged at the end 36 on the large diameter portion 31 side of the rack bar 30, when the rack bar 30 moves axially. The stopper ring 60 is formed in an annular shape, whereas the portion of the ball joint 50 that comes into contact with the stopper ring 60 is formed in a shape that is different from a circle when the ball joint 50 is viewed in the axial direction.

[0070] Figure 9 is an explanatory diagram showing a comparison of the shapes of stopper ring 60 and ball joint 50 in the FF direction of Figure 6. In Figure 9, the shape of stopper ring 60 is shown by a solid line, and the shape of outer peripheral surface 52 of ball joint 50 is shown by a two-dot chain line. Because stopper ring 60 is formed in an annular shape, when viewed in the axial direction, both the inner peripheral surface and the outer peripheral surface are formed to be circular, as shown in Figure 9.

[0071] On the other hand, the portion of ball joint 50 that abuts against stopper ring 60, i.e., the surface of ball joint 50 that is attached to rack bar 30, is shaped to have a pair of opposite sides 53 that are parallel to each other when viewed in the axial direction. The pair of opposite sides 53 of ball joint 50 are portions that are held with a tool when attaching ball joint 50 to rack bar 30. In this way, the ball joint 50 has a pair of opposite sides 53, and the width across flats Jb of the pair of opposite sides 53 is smaller than the inner diameter Sb of the stopper ring 60. In other words, the inner diameter Sb of the stopper ring 60 is larger than the width across flats Jb of the pair of opposite sides 53 of ball joint 50.

[0072] The inner diameter Sb of the stopper ring 60 is smaller than the maximum width Ja, in the direction perpendicular to the axial direction, of the portion of the ball joint 50 that abuts against the stopper ring 60. The outer diameter Sa of the stopper ring 60 is larger than the maximum width Ja, in the direction perpendicular to the axial direction, of the portion of the ball joint 50 that abuts against the stopper ring 60. The inner diameter Sb of the stopper ring 60 is larger than the inner diameter of the small diameter through hole 22 formed in the small diameter housing portion 21 of the rack housing 10.

[0073] That is, both the outer and inner peripheral surfaces of the stopper ring 60 are formed in a circular shape to reduce processing costs. Meanwhile, the ball joint 50 has a pair of opposite sides 53 so that the ball joint 50 can be held with a tool when the ball joint 50 is attached to the rack bar 30 by tightening the threaded portion 54 of the ball joint 50 into the screw holes 37, 47 of the rack bar 30. The shapes of the stopper ring 60 and the ball joint 50 are determined by these constraints, and the width across flats Jb of the pair of opposite sides 53 of the ball joint 50 is smaller than the inner diameter Sb of the stopper ring 60. Furthermore, the maximum width Ja of the portion of the ball joint 50 that abuts against the stopper ring 60 in a direction perpendicular to the axial direction is larger than the inner diameter Sb of the stopper ring 60 and smaller than the outer diameter Sa of the stopper ring 60.

[0074] Furthermore, a rack bushing 70 that supports the rack bar 30 is disposed in the large diameter through hole 12 of the rack housing 10. The rack bushing 70 is made of a resin material and is formed in a substantially cylindrical shape. The rack bushing 70 is disposed in the large diameter through hole 12 at a position closer to the small diameter through hole 22 than the stopper ring 60, and is spaced apart from the stopper ring 60 in the axial direction.

[0075] More specifically, the rack bush 70 has a thickness that varies depending on the position in the circumferential direction, and has relatively thin portions, so that it can support the assist rack tooth forming portion 33 formed in the large diameter portion 31 of the rack bar 30. The rack bush 70 also has a movement stopper 72 that protrudes radially outward on the outer circumferential surface 71. The movement stopper 72 is formed around the entire circumference of the outer circumferential surface 71 of the rack bush 70.

[0076] Meanwhile, the large diameter through hole 12 of the rack housing 10 has a bushing arrangement portion 12a formed in the vicinity of the portion that opens to the inside of the ball joint accommodating portion 15. The bushing arrangement portion 12a has an inner diameter that is slightly larger than the rest of the large diameter through hole 12. The rack bushing 70 is arranged in the bushing arrangement portion 12a, which is formed in the large diameter through hole 12 with a slightly larger inner diameter.

[0077] A groove 14 recessed from the inner peripheral surface is formed on the inner peripheral surface of the bushing mounting portion 12a in the large diameter through hole 12. The groove 14 is formed around the entire circumference of the inner peripheral surface of the bushing mounting portion 12a. The rack bushing 70 placed in the bushing mounting portion 12a of the large diameter through hole 12 is placed in a state where a movement stopper 72 formed on an outer peripheral surface 71 is fitted into the groove 14 formed on the inner peripheral surface of the bushing mounting portion 12a. The movement of the rack bushing 70 in the axial direction relative to the rack housing 10 is restricted by the movement stopper 72 fitting into the groove 14 formed in the bushing mounting portion 12a in this manner.

[0078] In the rack housing 10, a rack bushing 75 (see FIG. 7) that supports the rack bar 30 is also disposed in the small diameter through hole 22. The rack bushing 75 disposed in the small diameter through hole 22 is also made of a resin material and is formed in a substantially cylindrical shape. Meanwhile, the small diameter through hole 22 of the rack housing 10 has a portion near the portion that opens to the inside of the ball joint accommodating portion 25 formed as a bushing arrangement portion 22a. The bushing arrangement portion 22a has an inner diameter that is slightly larger than the portion of the small diameter through hole 22 other than the bushing arrangement portion 22a. The rack bushing 75 disposed in the small diameter through hole 22 is disposed in the bushing arrangement portion 22a, which is formed in the small diameter through hole 22 with a slightly larger inner diameter.

[0079] Next, the operation of the steering device 80 will be described. When the steering wheel 81 is operated while driving a vehicle equipped with the steering device 80, the steering force applied to the steering wheel 81 is transmitted from the steering wheel 81 to the steering shaft 82. The steering force transmitted to the steering shaft 82 is transmitted as steering torque from the steering shaft 82 to the intermediate shaft 85, and from the intermediate shaft 85 via the stub shaft 87 to the first pinion gear 91. As a result, the steering gear 90 having the first pinion gear 91 converts the rotational motion transmitted from the first pinion gear 91 into linear motion of the rack bar 30, causing the tie rod 93 to operate.

[0080] The steering device 80 according to this embodiment also has an electric motor 102 that generates an auxiliary steering torque to assist the driver in steering. The electric motor 102 generates the auxiliary steering torque based on the steering torque detected by a torque sensor 101 that is disposed between the stub shaft 87 and the first pinion gear 91.

[0081] Torque sensor 101 detects the steering torque applied to stub shaft 87 based on the angle of relative rotation when stub shaft 87 and first pinion gear 91 rotate relative to each other. That is, because stub shaft 87 and first pinion gear 91 are connected via a torsion bar (not shown), when steering torque is applied to stub shaft 87, the steering torque is transmitted between stub shaft 87 and first pinion gear 91 via the torsion bar. At that time, the torsion bar twists slightly, causing relative rotation between stub shaft 87 and first pinion gear 91. Torque sensor 101 detects the relative rotation between stub shaft 87 and first pinion gear 91 caused by the slight twisting of the torsion bar, and transmits the detected rotation to ECU 100 as an electrical signal.

[0082] The ECU 100 operates the electric motor 102 based on the electrical signal transmitted from the torque sensor 101, causing the electric motor 102 to generate an assist steering torque. In other words, the electrical signal transmitted from the torque sensor 101 to the ECU 100 changes based on the steering torque T acting between the stub shaft 87 and the first pinion gear 91. Therefore, the ECU 100 uses the electrical signal transmitted from the torque sensor 101 as information that changes depending on the steering torque T acting on the stub shaft 87 and the first pinion gear 91, and adjusts the power value X supplied to the electric motor 102 based on the electrical signal transmitted from the torque sensor 101, causing the electric motor 102 to generate an assist steering torque.

[0083] That is, ECU 100 acquires a signal of steering torque T from torque sensor 101, acquires a vehicle speed signal V of the vehicle from vehicle speed sensor 103, and further acquires operation information Y of electric motor 102 from a rotation detection device provided in electric motor 102. Based on this operation information Y, steering torque T, and vehicle speed signal V, ECU 100 causes electric motor 102 to generate auxiliary steering torque. The auxiliary steering torque generated by electric motor 102 is transmitted to second pinion gear 92. Steering gear 90 having second pinion gear 92 converts the rotational motion transmitted from second pinion gear 92 into linear motion of rack bar 30. As a result, the steering force applied to steering wheel 81 by the driver is assisted by the auxiliary steering torque generated by electric motor 102.

[0084] More specifically, when the driver turns the steering wheel 81, the stub shaft 87 and the first pinion gear 91 rotate due to the transmission of steering force. When the first pinion gear 91 rotates, the steering torque of the first pinion gear 91 is transmitted from the first pinion gear 91 to the steering rack teeth 44 of the rack bar 30 that mesh with the first pinion gear 91. As a result, the rack bar 30 moves linearly in the axial direction while being supported by the rack housing 10.

[0085] Furthermore, the driving force generated by the electric motor 102 is transmitted to the second pinion gear 92 via the worm reduction gear 94, and the second pinion gear 92 is rotated by the driving force generated by the electric motor 102. When the second pinion gear 92 rotates, the auxiliary steering torque of the second pinion gear 92 is transmitted from the second pinion gear 92 to the assist rack teeth 34 of the rack bar 30 that meshes with the second pinion gear 92. As a result, the rack bar 30 performs linear motion while the linear motion caused by the steering torque from the first pinion gear 91 is assisted by the auxiliary steering torque from the second pinion gear 92.

[0086] The linear motion of the rack bar 30 is transmitted from the ball joints 50 arranged on both ends of the rack bar 30 to the tie rods 93 connected to the ball joints 50, and the direction of the wheels is changed in accordance with the movement of the tie rods 93.

[0087] When the driver turns the steering wheel 81 as described above to change the direction of the wheels, the rack bar 30 moves in a linear manner, but the linear movement of the rack bar 30 is restricted by the ball joints 50 arranged at both ends of the rack bar 30 coming into contact with members that restrict the movement of the ball joints 50.

[0088] 10 is an explanatory diagram showing a state in which movement of the rack bar 30 is restricted when it moves in the direction where the large diameter portion 31 is located. FIG. 11 is a detailed view of portion D in FIG. 10. When the rack bar 30 is linearly moved by steering torque or auxiliary steering torque to move the rack bar 30 in the direction where the large diameter portion 31 is located, if the rack bar 30 moves significantly, the ball joint 50 arranged at the end 46 of the rack bar 30 on the small diameter portion 41 side comes into contact with the rack housing 10. In other words, when the rack bar 30 is moved axially in the direction where the large diameter portion 31 is located, the ball joint 50 arranged at the end 46 of the rack bar 30 on the large diameter portion 31 side moves away from the rack housing 10, and the ball joint 50 arranged at the end 46 of the rack bar 30 on the small diameter portion 41 side moves closer to the rack housing 10.

[0089] For this reason, when the rack bar 30 is moved significantly in the direction in which the large diameter portion 31 is located, the abutment portion 55 of the ball joint 50 arranged at the end 46 on the small diameter portion 41 side of the rack bar 30 abuts against the position of the end 23 of the small diameter through hole 22 in the small diameter housing portion 21 of the rack housing 10. In the ball joint 50 arranged at the end 46 on the small diameter portion 41 side of the rack bar 30, the abutment portion 55 is located radially outward of the small diameter portion 41 of the rack bar 30 to which the ball joint 50 is attached, and is the portion that faces the side in the axial direction in which the small diameter through hole 22 is located. When the rack bar 30 is moved significantly in the direction where the large diameter portion 31 is located, the ball joint 50 arranged at the end 46 on the small diameter portion 41 side of the rack bar 30 enters inside the ball joint accommodating portion 25 on the small diameter housing portion 21 side of the rack housing 10, and the abutment portion 55 abuts against the position of the end 23 of the small diameter through hole 22 in the small diameter housing portion 21 of the rack housing 10.

[0090] More specifically, when the axial end of the small-diameter through-hole 22 that opens toward the ball joint 50 is defined as the opening of the small-diameter through-hole 22, the abutment portion 55 of the ball joint 50 abuts against the end 23, which is the portion located radially outward of the opening of the small-diameter through-hole 22 in the rack housing 10. This prevents the rack bar 30 from moving any further in the direction toward the large-diameter portion 31, restricting movement of the rack bar 30 in the direction toward the large-diameter portion 31. In other words, when the rack bar 30 is moved in the direction toward the large-diameter portion 31, the ball joint 50, which is located at the end 46 of the rack bar 30 on the small-diameter portion 41 side, abuts against the position of the end 23 of the small-diameter through-hole 22 in the small-diameter housing portion 21 of the rack housing 10, thereby restricting movement of the rack bar 30 in the direction toward the large-diameter portion 31.

[0091] Fig. 12 is an explanatory diagram showing a state in which movement of the rack bar 30 is restricted when it moves in the direction in which the small diameter portion 41 is located. Fig. 13 is a detailed view of part E in Fig. 12. When the rack bar 30 is moved in the direction in which the small diameter portion 41 is located by linearly moving the rack bar 30 using steering torque or auxiliary steering torque, if the rack bar 30 moves significantly, the ball joint 50 arranged at the end 36 of the rack bar 30 on the large diameter portion 31 side will come into contact with the stopper ring 60.

[0092] In other words, when the rack bar 30 is moved in the axial direction in the direction where the small diameter portion 41 is located, the ball joint 50 located at the end 46 of the rack bar 30 on the small diameter portion 41 side moves away from the rack housing 10, and the ball joint 50 located at the end 36 of the rack bar 30 on the large diameter portion 31 side moves closer to the rack housing 10.

[0093] For this reason, when the rack bar 30 is moved significantly in the direction in which the small diameter portion 41 is located, the ball joint 50, which is arranged at the end 36 of the rack bar 30 on the large diameter portion 31 side, abuts at the abutting portion 55 against the stopper ring 60, which is arranged in the large diameter housing portion 11 of the rack housing 10. In the ball joint 50 arranged at the end 36 of the rack bar 30 on the large diameter portion 31 side, the abutting portion 55 is located radially outward of the large diameter portion 31 of the rack bar 30 to which the ball joint 50 is attached, and is the portion that faces the side in the axial direction in which the large diameter through hole 12 is located. When the rack bar 30 is moved significantly in the direction in which the small diameter portion 41 is located, the ball joint 50 arranged at the end 36 of the rack bar 30 on the large diameter portion 31 side enters the ball joint accommodating portion 15 on the large diameter housing portion 11 side of the rack housing 10, and the abutting portion 55 abuts against the stopper ring 60, which is arranged in the large diameter housing portion 11 of the rack housing 10.

[0094] In other words, the inner diameter Sb (see FIG. 9) of the stopper ring 60 is smaller than the maximum width Ja (see FIG. 9) in the direction perpendicular to the axial direction of the abutment portion 55 of the ball joint 50 that abuts against the stopper ring 60, and the outer diameter Sa (see FIG. 9) of the stopper ring 60 is larger than the maximum width Ja. As a result, when the ball joint 50, which is arranged at the end 36 on the large diameter portion 31 side of the rack bar 30, abuts against the stopper ring 60, the rack bar 30 cannot move any further in the direction toward which the small diameter portion 41 is located. Therefore, movement of the rack bar 30 in the direction toward which the small diameter portion 41 is located is restricted. In other words, when the rack bar 30 is moved in the direction where the small diameter portion 41 is located, the ball joint 50 located at the end 36 of the rack bar 30 on the large diameter portion 31 side comes into contact with the stopper ring 60, thereby restricting the movement of the rack bar 30 in the direction where the small diameter portion 41 is located.

[0095] Furthermore, the inner diameter Sb of the stopper ring 60 arranged on the large diameter housing portion 11 side of the rack housing 10 is larger than the inner diameter of the small diameter through hole 22 formed in the small diameter housing portion 21 of the rack housing 10. Therefore, the opposing area between the ball joint 50 arranged on the large diameter portion 31 side of the rack bar 30 and the stopper ring 60 when they are in contact is smaller than the opposing area between the ball joint 50 and the rack housing 10 when the ball joint 50 arranged on the small diameter portion 41 side of the rack bar 30 is in contact with the end of the small diameter housing portion 21 of the rack housing 10.

[0096] In other words, the opposing area between ball joint 50, which is arranged on the large diameter portion 31 side of rack bar 30, and stopper ring 60 is smaller than the opposing area between ball joint 50, which is arranged on the small diameter portion 41 side of rack bar 30, and rack housing 10, because the shapes of ball joint 50 and stopper ring 60 are determined by the above-mentioned constraints. The iron stopper ring 60 restricts movement of rack bar 30 in a state in which the opposing area with ball joint 50 in this state when ball joint 50 is in contact is smaller than the opposing area with ball joint 50 in a state in which ball joint 50 on the small diameter portion 41 side of rack bar 30 is in contact with rack housing 10.

[0097] Furthermore, even if the rack bar 30 moves toward the small diameter portion 41 until the ball joint 50, which is arranged on the end 36 of the rack bar 30 on the large diameter portion 31 side, abuts against the stopper ring 60, the large diameter portion 31 of the rack bar 30 does not move to the position of the small diameter through-hole 22 of the rack housing 10. In other words, when the rack bar 30 moves to the side where the small diameter portion 41 is located, the ball joint 50 abuts against the stopper ring 60, restricting the movement of the rack bar 30, and therefore restricting the movement of the large diameter portion 31 of the rack bar 30 to the position of the small diameter through-hole 22 of the rack housing 10.

[0098] As described above, in the steering device 80 according to this embodiment, the rack housing 10 has a large diameter housing portion 11 in which the large diameter through hole 12 is formed and a small diameter housing portion 21 in which the small diameter through hole 22 is formed, and the stopper ring 60, which has a higher modulus of longitudinal elasticity than the rack housing 10, is disposed at the end of the large diameter through hole 12 opposite to the side where the small diameter through hole 22 is located. As a result, when the rack bar 30 is moved in the direction where the small diameter portion 41 is located, the ball joint 50, which is disposed at the end of the rack bar 30 on the large diameter portion 31 side, comes into contact with the stopper ring 60, thereby restricting movement of the rack bar 30 in the direction where the small diameter portion 41 is located.

[0099] Therefore, the large-diameter through-hole 12 has a large diameter, making it difficult to ensure the area of ​​the portion where the ball joint 50 abuts, and the large-diameter housing portion 11 of the rack housing 10 is prone to large stress. This allows the ball joint 50 to abut against the stopper ring 60, which has a high Young's modulus. Therefore, the durability of the rack housing 10 can be ensured when restricting the movement of the rack bar 30 by abutting the ball joint 50 against the rack housing 10. Furthermore, when ensuring the durability of the rack housing 10 when the ball joint 50 abuts against it, the durability is ensured by disposing the stopper ring 60, which has a high Young's modulus, without increasing the outer diameter of the large-diameter housing portion 11, and therefore an increase in the weight of the rack housing 10 can be suppressed. As a result, the rack housing 10 can be made both lightweight and durable.

[0100] Furthermore, when the rack bar 30 is moved in the direction toward the large diameter portion 31, the ball joint 50 abuts against the end 23 of the small diameter through hole 22 of the rack housing 10, thereby restricting the movement of the rack bar 30. As a result, on the small diameter housing portion 21 side of the rack housing 10, where it is easy to ensure the thickness of the portion where the ball joint 50 abuts, the portion where the ball joint 50 abuts can be secured without disposing a stopper ring 60, thereby reducing the weight of the rack housing 10. Furthermore, when the rack bar 30 is moved in the direction toward the small diameter portion 41, the ball joint 50 abuts against the stopper ring 60, thereby restricting the movement of the rack bar 30. As a result, on the large diameter housing portion 11 side, where it is difficult to ensure the thickness of the portion where the ball joint 50 abuts, the ball joint 50 abuts against the stopper ring 60, thereby suppressing damage to the rack housing 10 due to impact from the ball joint 50. As a result, it is possible to achieve both weight reduction and durability of the rack housing 10.

[0101] Furthermore, due to the geometric constraints of the ball joint 50 and the stopper ring 60 described above, the opposing area between the ball joint 50 and the stopper ring 60 when they are in contact is smaller than the opposing area between the ball joint 50 and the rack housing 10 when the ball joint 50 on the small diameter portion 41 is in contact with the end of the small diameter housing portion 21 of the rack housing 10. Therefore, the ball joint 50 on the large diameter portion 31 of the rack bar 30 is prone to high surface pressure at the contacting portion, but the stopper ring 60, with which the ball joint 50 on the large diameter portion 31 is in contact, has a higher modulus of longitudinal elasticity than the rack housing 10. Therefore, the small opposing area between the ball joint 50 and the stopper ring 60 ensures durability when the ball joint 50 abuts on the large diameter housing portion 11 of the rack housing 10, which is prone to high surface pressure. As a result, the rack housing 10 can be made both lightweight and durable.

[0102] Furthermore, the ball joint 50 has a pair of opposite sides 53 that are used when holding the ball joint 50 with a tool, and the inner diameter Sb of the stopper ring 60 is larger than the width across flats Jb of the pair of opposite sides 53 of the ball joint 50. Therefore, when the ball joint 50 abuts against the stopper ring 60, localized stress is more likely to occur compared to when the portion of the ball joint 50 that abuts against the stopper ring 60 is formed in a circular shape. In contrast, in this embodiment, the stopper ring 60 has a higher modulus of longitudinal elasticity than the rack housing 10, so that strength and durability can be ensured even if localized stress occurs in the stopper ring 60. As a result, the rack housing 10 can be made both lightweight and durable.

[0103] Furthermore, a rack bushing 70 made of a resin material and supporting the rack bar 30 is disposed in the large diameter through hole 12 closer to the small diameter through hole 22 than the stopper ring 60, and the rack bushing 70 is disposed axially away from the stopper ring 60. This prevents the force from the ball joint 50 from being transmitted to the rack bushing 70 when the ball joint 50 abuts against the stopper ring 60. This prevents the rack bushing 70, which is made of a resin material and therefore has lower strength than the stopper ring 60, from being compressed in the axial direction and being damaged. As a result, the durability of the members disposed in the rack housing 10 can be improved.

[0104] Furthermore, the rack bushing 70 has a movement stopper 72 on its outer peripheral surface 71, and the movement stopper 72 fits into the groove 14 formed in the large-diameter through-hole 12, thereby restricting axial movement of the rack bushing 70 relative to the rack housing 10, thereby preventing the rack bushing 70 from moving toward the stopper ring 60. This prevents the force acting on the stopper ring 60 from the ball joint 50 from being transmitted from the stopper ring 60 to the rack bushing 70, preventing the rack bushing 70 from being compressed in the axial direction and being damaged. As a result, the durability of the members arranged in the rack housing 10 can be improved.

[0105] Furthermore, because the stopper ring 60 is press-fit into the large-diameter housing portion 11, the clearance between the rack bar 30 and the stopper ring 60 can be reduced. This increases the opposing area between the ball joint 50 and the stopper ring 60, and reduces the surface pressure between the ball joint 50 and the stopper ring 60. This ensures the durability of the stopper ring 60. As a result, the rack housing 10 can be made lighter while ensuring its durability.

[0106] Furthermore, since the outer diameter of at least a portion of the small diameter housing portion 21 of the rack housing 10 is smaller than the outer diameter of the large diameter housing portion 11, it is possible to reduce the weight of the small diameter housing portion 21 of the rack housing 10. As a result, it is possible to reduce the weight of the rack housing 10.

[0107] Furthermore, since the small diameter through-hole 22 of the rack housing 10 has a minimum diameter smaller than the maximum width of the large diameter portion 31 of the rack bar 30, the weight of the small diameter housing portion 21 of the rack housing 10 can be reduced. As a result, the weight of the rack housing 10 can be reduced.

[0108] 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. [Explanation of symbols]

[0109] 10 Rack Housing 11 Large diameter housing part 12 Large diameter through hole 13, 23 End 14 Groove 15, 25 Ball joint housing 21 Small diameter housing part 22 Small diameter through hole 30 Rack Bar 31 Large diameter section 32 Large diameter round bar section 33 Assist rack tooth forming section 34 assist rack teeth 35 Back 36, 46 End 41 Small diameter section 42 Small diameter round bar section 44 steering rack teeth 50 ball joint 52 Outer surface 53 opposite side 60 Stopper Ring 70, 75 Luck Bush 72 Stopper 80 Steering Gear 81 Steering wheel 82 Steering shaft 84, 86 universal joint 85 Intermediate shaft 87 Stub shaft 90 Steering gear 91 1st pinion gear 92 2nd pinion gear 93 tie rod 94 Worm reducer 100 ECU 101 Torque sensor 102 electric motor 103 Vehicle speed sensor 104 Ignition switch 105 Power supply

Claims

1. a rack bar having a large diameter portion and a small diameter portion whose maximum widths in a direction perpendicular to the longitudinal direction are different from each other; a rack housing having a large diameter housing portion in which a large diameter through hole is formed, and a small diameter housing portion in which a small diameter through hole that is in communication with the large diameter through hole and has a diameter smaller than that of the large diameter through hole is formed, the rack housing storing the rack bar in an internal space between the large diameter through hole and the small diameter through hole such that the axial directions of the large diameter through hole and the small diameter through hole coincide with the longitudinal direction of the rack bar; Ball joints disposed on both ends of the rack bar; a stopper ring having a modulus of longitudinal elasticity higher than that of the rack housing, formed in a substantially annular shape, and disposed at an end of the large-diameter through hole opposite to a side where the small-diameter through hole is located; Equipped with the ball joint abuts against the rack housing or the stopper ring, and the ball joint abutting against the rack housing and the ball joint abutting against the stopper ring have the same shape at the abutment point; the large diameter through hole accommodates the large diameter portion of the rack bar; The small diameter through hole accommodates the small diameter portion of the rack bar in the steering device.

2. The rack bar and the rack housing are when the rack bar is moved in a direction toward the large diameter portion, the ball joint disposed at the end of the rack bar on the small diameter portion side comes into contact with the position of the end of the small diameter through hole in the small diameter housing portion of the rack housing, thereby restricting movement of the rack bar in the direction toward the large diameter portion, 2. The steering device according to claim 1, wherein, when the rack bar is moved in a direction in which the small diameter portion is located, the ball joint arranged at the end of the rack bar on the large diameter portion side comes into contact with the stopper ring, thereby restricting movement of the rack bar in the direction in which the small diameter portion is located.

3. The opposing area between the ball joint and the stopper ring when the ball joint and the stopper ring are in contact with each other is 3. The steering device according to claim 2, wherein the area of ​​the ball joint arranged on the small diameter portion side of the rack bar is smaller than the area of ​​the ball joint and the rack housing when the ball joint and the end of the small diameter housing portion of the rack housing are in contact with each other.

4. a portion of the ball joint that abuts against the stopper ring has a shape that has a pair of opposite sides that are parallel to each other when viewed in the axial direction; 4. The steering device according to claim 3, wherein an inner diameter of the stopper ring is larger than a width across two faces of the pair of opposite sides of the ball joint and smaller than a maximum width of a portion of the ball joint that abuts against the stopper ring in a direction perpendicular to the axial direction.

5. a rack bushing made of a resin material and supporting the rack bar is disposed in the large diameter through hole on the small diameter through hole side of the stopper ring; 5. The steering apparatus according to claim 1, wherein the rack bush is formed in a substantially cylindrical shape and is disposed spaced apart from the stopper ring in the axial direction.

6. 6. The steering device according to claim 5, wherein the rack bush has a stopper that protrudes radially outward on its outer peripheral surface, and the stopper fits into a groove formed on the inner peripheral surface of the large-diameter through hole, thereby restricting movement in the axial direction relative to the rack housing.

7. The steering device according to any one of claims 1 to 4, wherein the stopper ring is press-fitted into the large-diameter housing portion.

8. The steering device according to any one of claims 1 to 4, wherein the rack housing has an outer diameter of at least a part of the small diameter housing portion that is smaller than an outer diameter of the large diameter housing portion.

9. The steering device according to any one of claims 1 to 4, wherein the small diameter through hole of the rack housing has a minimum diameter smaller than the maximum width of the large diameter portion of the rack bar.

Images