Rack Assist Type Power Steering Apparatus

Abstract

The present invention provides a rack-driven power-assisted steering device comprising: a rack bar having an outer screw groove formed on its outer surface; a ball nut having an inner screw groove corresponding to the outer screw groove on its inner surface and a bearing coupled to one side of its outer surface; and a nut pulley having a belt coupling portion on its outer surface, a coupling end at one end of its inner surface that is coupled to the other outer surface of the ball nut to support the bearing, and an enlargement portion at the other end of its inner surface that is stepped at the coupling end and has an enlarged inner diameter.

Description

Technology Field

[0001] The embodiments relate to a rack-driven power assist steering system, and more specifically, to a rack-driven power assist steering system in which the nut pulley and bearing do not detach from, deform, or break from the ball nut even when continuous steering is performed while driving a vehicle, and the slip of the nut pulley caused by shocks transmitted from the road surface or overload during operation is prevented, thereby enabling accurate steering assistance force to be transmitted to the ball nut. Background Technology

[0002] A typical rack-driven power-assisted steering system is configured to include a steering system extending from the steering wheel to both wheels, and an auxiliary power mechanism that supplies steering assistance power to the steering system.

[0003] Such conventional rack-driven power-assisted steering systems consist of a motor controlled by an electronic control unit, a motor pulley fixed to the motor shaft, a ball nut connected to the rack bar via balls, a return tube connected to the ball nut through which balls circulate, a nut pulley connected to the outer surface of the ball nut, and a belt connected to the motor pulley and the nut pulley.

[0004] However, rack-driven power-assisted steering systems based on such conventional technology had a problem in which nut pulleys or bearings would become dislodged, deformed, or broken due to vibrations caused by continuous steering while driving and shocks transmitted from the road surface.

[0005] In addition, there was a problem in that slip of the nut pulley occurred due to shocks transmitted from the road surface or overload during operation, which reduced steering assistance and power transmission efficiency, making it impossible to transmit accurate steering assistance.

[0006] Accordingly, the embodiments are conceived from the background described above, and aim to provide a rack-driven power-assisted steering system in which the nut pulley and bearing do not become detached, deformed, or damaged from the ball nut even when continuous steering is performed while driving a vehicle, and the slip of the nut pulley caused by shocks transmitted from the road surface or excessive load during operation is prevented, thereby enabling accurate steering assistance force to be transmitted to the ball nut.

[0007] In one aspect, embodiments may provide a rack-driven power-assisted steering device comprising: a rack bar having an outer screw groove formed on its outer surface; a ball nut having an inner screw groove corresponding to the outer screw groove on its inner surface and a bearing coupled to one side of its outer surface; and a nut pulley having a belt coupling portion on its outer surface, a coupling end at one end of its inner surface that is coupled to the other outer surface of the ball nut to support the bearing, and an enlargement portion at the other end of its inner surface that is stepped at the coupling end and has an enlarged inner diameter.

[0008] According to these embodiments, a rack-driven power-assisted steering system can be provided in which the nut pulley and bearing do not become detached, deformed, or damaged from the ball nut even when continuous steering is performed while driving a vehicle, and slip of the nut pulley caused by shocks transmitted from the road surface or excessive load during operation is prevented, thereby enabling accurate steering assistance force to be transmitted to the ball nut. Brief explanation of the drawing

[0009] FIG. 1 is a schematic diagram showing a rack-driven power-assisted steering device according to the embodiments thereof. FIG. 2 is a perspective view showing a part of a rack-driven power-assisted steering device according to the embodiments thereof. FIGS. 3 and FIGS. 4 are exploded perspective views of FIG. 2. FIG. 5 is a perspective view showing a part of a rack-driven power-assisted steering device according to the embodiments thereof. FIGS. 6 and 7 are cross-sectional views showing a part of a rack-driven power-assisted steering device according to the embodiments thereof. FIG. 8 is an exploded perspective view showing a part of a rack-driven power-assisted steering device according to the embodiments thereof. FIGS. 9 and FIGS. 10 are cross-sectional views showing a part of a rack-driven power-assisted steering device according to the embodiments of the present invention. Specific details for implementing the invention

[0010] The embodiments described below will be explained in detail with reference to the exemplary drawings. In assigning reference numerals to the components of each drawing, the same components may have the same reference numeral as much as possible, even if they are shown in different drawings. Furthermore, in describing the embodiments, if it is determined that a detailed description of related known configurations or functions could obscure the essence of the technical concept, such detailed description may be omitted. Where terms such as "includes," "has," or "is made up" are used in this specification, other parts may be added unless "only" is used. Where a component is expressed in the singular, it may include a plural unless otherwise explicitly stated.

[0011] Additionally, terms such as first, second, A, B, (a), (b), etc., may be used to describe the components of the embodiments. These terms are used merely to distinguish the components from other components, and the nature, order, sequence, or number of the components are not limited by the terms.

[0012] In describing the positional relationship of components, where it is stated that two or more components are "connected," "combined," or "joined," it should be understood that while the two or more components may be directly "connected," "combined," or "joined," they may also be "connected," "combined," or "joined" with other components "intervened." Here, the other components may be included in one or more of the two or more components that are "connected," "combined," or "joined" with one another.

[0013] In describing the temporal flow relationship regarding components, methods of operation, or methods of production, for example, when the temporal or sequential relationship is described using "after," "following," "next," or "before," it may include cases where the relationship is not continuous unless "immediately" or "directly" is used.

[0014] Meanwhile, where numerical values ​​or corresponding information regarding a component (e.g., levels, etc.) are mentioned, even without separate explicit notation, the numerical values ​​or corresponding information may be interpreted as including a range of error that may occur due to various factors (e.g., process factors, internal or external shocks, noise, etc.).

[0015] FIG. 1 is a schematic diagram showing a rack-driven power-assisted steering device according to the embodiments of the present invention; FIG. 2 is a perspective view showing a part of the rack-driven power-assisted steering device according to the embodiments of the present invention; FIG. 3 and FIG. 4 are exploded perspective views of FIG. 2; FIG. 5 is a perspective view showing a part of the rack-driven power-assisted steering device according to the embodiments of the present invention; FIG. 6 and FIG. 7 are cross-sectional views showing a part of the rack-driven power-assisted steering device according to the embodiments of the present invention; FIG. 8 is an exploded perspective view showing a part of the rack-driven power-assisted steering device according to the embodiments of the present invention; FIG. 9 and FIG. 10 are cross-sectional views showing a part of the rack-driven power-assisted steering device according to the embodiments of the present invention.

[0016] As illustrated in these drawings, the rack-driven power-assisted steering device according to the embodiments comprises: a rack bar (120) having an outer screw groove (120a) formed on its outer surface; a ball nut (125) having an inner screw groove (127) corresponding to the outer screw groove (120a) on its inner surface and a bearing (140) coupled to one side of its outer surface; and a nut pulley (130) having a belt coupling part (131) on its outer surface, a coupling end (133) on one end of its inner surface that is coupled to the other outer surface of the ball nut (125) to support the bearing (140), and an enlargement part (135) on the other end of its inner surface that is stepped at the coupling end (133) and has an enlarged inner diameter.

[0017] The rack-driven power assist steering device according to the embodiments is configured such that a torque sensor (103) is coupled to one side of a steering shaft (102, 106) connected to a steering wheel (101), and an electric signal is sent to a motor (113) from the torque sensor (103), steering angle sensor (121), vehicle speed sensor (122), etc., which detects the operation of the steering wheel (101) by the driver, thereby steering both wheels (115) through a tie rod (119).

[0018] In a rack-driven power-assisted steering device, the upper steering shaft (102) is connected to the lower steering shaft (106) through a universal joint (104), and steering is achieved through a rack-pinion mechanism (116) consisting of a pinion (108) and a rack gear (112).

[0019] Here, the driving force of the motor (113) driven by the electronic control unit (111) is transmitted to the ball nut (125) through the motor (113) and the belt (155), and the rack bar (120) coupled to the ball nut (125) via the ball slides in the axial direction, and tie rods (119) are coupled to both sides of the rack bar (120), and the tie rods (119) are coupled to the knuckle arm (117) connected to the wheel (115) to steer the wheel (115).

[0020] And, the electrical signal generated from the torque sensor (103) is sent to the electronic control unit (111), and the electronic control unit (111) controls the motor (113) based on the electrical signal transmitted from the torque sensor (103) and the electrical signals transmitted from the steering angle sensor (121), vehicle speed sensor (122), etc., mounted on the vehicle.

[0021] A power transmission structure is provided on the inner surface of the ball nut (125) and the outer surface of the rack bar (120) to generate steering assistance force by sliding the rack bar (120) in the axial direction. This power transmission structure is composed of an outer screw groove (120a) formed spirally with a hemispherical or arc-shaped cross section on the outer surface of the rack bar (120), a ball (not shown) inserted therein, and an inner screw groove (127) formed spirally with a hemispherical or arc-shaped cross section on the inner surface of the ball nut (125) corresponding to the outer screw groove (120a).

[0022] A ball nut (125) having an inner screw groove (127) formed on its inner surface has several ball circulation holes (129) that penetrate the inner surface and the outer surface, spaced apart along the inner screw groove (127).

[0023] Accordingly, balls that move along the inner screw groove (127) can circulate inside the ball nut (125) through a circulation tube or end cap, etc., that is coupled to the ball circulation hole (129), and a bearing (140) supported by a rack housing (not shown) is coupled to one side to support the rotation of the ball nut (125).

[0024] A nut pulley (130) is provided on the outer side of the ball nut (125), and a belt coupling part (131) is provided on the outer surface of the nut pulley (130), so that when the belt rotates, the nut pulley (130) rotates the ball nut (125), thereby causing the rack bar (120) to move linearly to the left and right.

[0025] One end of the inner surface of the nut pulley (130) is provided with a connecting end (133) that is connected to the other outer surface of the ball nut (125) to support the bearing (140), and the other end of the inner surface is provided with an enlarged portion (135) that is stepped from the connecting end (133) and has an enlarged inner diameter.

[0026] A pulley screw portion (134) is formed on the inner surface of the connecting end (133), and a nut screw portion (128) is formed on the outer surface of the other side of the ball nut (125), so that the pulley screw portion (134) can be screw-coupled with the nut screw portion (128).

[0027] Additionally, the ball nut (125) has a caulking groove (124) formed on the outer surface of the other end to which the nut pulley (130) is coupled, so that it can be caulked and fixed to the end of the coupling end (133) of the nut pulley (130).

[0028] The end of the connecting end (133) of the nut pulley (130) may be formed at the same position in the axial direction as the end of the ball nut (125) or may be formed to protrude further in the axial direction than the end of the ball nut (125).

[0029] The caulking is fixed by applying pressure with a caulking tool to plastically deform the end of the connecting end (133) located opposite the circumferential direction of the caulking groove (124), that is, the end of the connecting end (133) located on the upper or lower side of the caulking groove (124) in the drawing, thereby filling the inside of the caulking groove (124) with the end of the connecting end (133).

[0030] Therefore, when the ball nut (125) and the nut pulley (130) are combined, they are fixed in the caulking groove (124), so that the nut pulley (130) does not slip from the ball nut (125), and the driving force transmitted through the belt (155) can be transmitted accurately.

[0031] Here, one or more caulking grooves (124) may be provided, and if two or more caulking grooves (124) are provided, they are arranged at equal intervals in the circumferential direction of the ball nut (125) to evenly distribute the positions where the nut pulley (130) is fixed, thereby distributing the load applied to the caulking portion.

[0032] In the present embodiments, two caulking grooves (124) are provided and arranged at equal intervals in the circumferential direction, and are shown as an example of being provided at positions facing each other in the radial direction.

[0033] Meanwhile, the connecting end (133) is formed to be stepped in the radial direction with the belt connecting part (131) and protrudes in the axial direction, thereby supporting one end of the inner ring of the bearing (140) in the axial direction.

[0034] A tool coupling portion (137) to which a tool is coupled is formed on the outer surface of the coupling end (133), so that when the nut pulley (130) is coupled to the ball nut (125), the fastening tool can be mounted on the tool coupling portion (137) to facilitate screw assembly.

[0035] Additionally, a support projection (126) is formed on the outer surface of the ball nut (125) to axially support the other end of the inner ring of the bearing (140), so that when the nut pulley (130) is screw-assembled to the ball nut (125), one end of the inner ring of the bearing (140) is supported by the coupling end (133) and the other end of the bearing (140) is supported by the support projection (126), allowing the bearing (140) to be coupled without slipping in the correct position.

[0036] Additionally, as shown in FIG. 7, a ball nut (125) has a circumferential fastening groove (128a) formed on the outer surface of the other end to which the nut pulley (130) is coupled, and a fastening member (150) can be coupled to and fixed in the fastening groove (128a).

[0037] Here, the fastening member (150) is formed in a ring shape with one side cut and is coupled to the fastening groove (128a) and supported at the end of the coupling end (133), thereby fixing the nut pulley (130) so that it does not move in the axial direction and preventing the screw from loosening.

[0038] Meanwhile, as shown in FIGS. 8 to 10, the inner surface of the connecting end (133) of the nut pulley (130) can be press-fitted to the outer surface of the ball nut (125).

[0039] As shown in FIG. 9, the ball nut (125) has a caulking groove (124) formed on the outer surface of the other end to which the nut pulley (130) is coupled, so that it can be caulked and fixed to the end of the coupling end (133) of the nut pulley (130).

[0040] Here, one or more caulking grooves (124) may be provided, and if two or more are provided, they are arranged at equal intervals in the circumferential direction of the ball nut (125).

[0041] Also, as shown in FIGS. 8 and 10, a circumferential fastening groove (128a) is formed on the outer surface of the other end to which the nut pulley (130) is coupled, and a fastening member (150) can be coupled to the fastening groove (128a).

[0042] Here, the fastening member (150) is formed in a ring shape with one side cut off as shown in FIG. 8 and is coupled to the fastening groove (128a) and supported at the end of the coupling end (133).

[0043] Therefore, the nut pulley (130) is fixed so that it does not move in the axial direction, and slipping of the nut pulley (130) is prevented.

[0044] Additionally, the connecting end (133) is formed to be stepped in the radial direction with the belt connecting part (131) and protrude in the axial direction to axially support one end of the inner ring of the bearing (140), and a supporting projection (126) may be formed on the outer surface of the ball nut (125) to axially support the other end of the inner ring of the bearing (140).

[0045] Accordingly, when the nut pulley (130) is press-fitted onto the ball nut (125), one end of the inner ring of the bearing (140) is supported by the connecting end (133) and the other end of the bearing (140) is supported by the supporting projection (126), so that the bearing (140) can be connected without slipping in the correct position.

[0046] According to these embodiments, a rack-driven power-assisted steering system can be provided in which the nut pulley and bearing do not become detached, deformed, or damaged from the ball nut even when continuous steering is performed while driving a vehicle, and slip of the nut pulley caused by shocks transmitted from the road surface or excessive load during operation is prevented, thereby enabling accurate steering assistance force to be transmitted to the ball nut.

[0047] The foregoing description is merely an illustrative explanation of the technical concept of the present disclosure, and those skilled in the art to which the present disclosure pertains may make various modifications and variations within the scope of the essential characteristics of the technical concept. Furthermore, since these embodiments are intended to explain, not limit, the scope of the technical concept is not limited by these embodiments. The scope of protection of the present disclosure shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present disclosure. Explanation of the symbols

[0048] 120: Rack bar 124: Caulking groove 125: Ball nut 126: Support projection 130: Nut pulley 131: Belt connection part 133: Connecting end 135: Enlarged part

Claims

Claim 1 A rack-driven power-assisted steering device comprising: a rack bar having an outer screw groove formed on its outer surface; a ball nut having an inner screw groove corresponding to the outer screw groove on its inner surface and a bearing coupled to one side of its outer surface; a nut pulley having a belt coupling portion on its outer surface, a coupling end portion coupled to the other outer surface of the ball nut at one end of its inner surface to support the bearing, and an enlargement portion formed with a stepped edge at the coupling end and an enlarged inner diameter at the other end of its inner surface; wherein a support projection formed protruding from the outer surface of the ball nut axially supports the other end of the inner ring of the bearing, and the one end of the inner ring of the bearing is supported by the coupling end. Claim 2 A rack-driven power-assisted steering device according to claim 1, characterized in that a pulley screw portion is formed on the inner surface of the coupling end and a nut screw portion is formed on the outer surface of the other side of the ball nut, so that the pulley screw portion is screw-coupled with the nut screw portion. Claim 3 A rack-driven power-assisted steering device according to claim 2, characterized in that the ball nut has a caulking groove formed on the outer circumference of the other end to which the nut pulley is coupled, and is caulked and fixed with the end of the coupling end of the nut pulley. Claim 4 A rack-driven power-assisted steering device according to claim 3, characterized in that one or more caulking grooves are provided, and when two or more are provided, they are arranged at equal intervals in the circumferential direction of the ball nut. Claim 5 A rack-driven power-assisted steering device according to claim 2, characterized in that the coupling end is formed to be stepped in the radial direction with the belt coupling end and protrudes in the axial direction to axially support one end of the bearing inner ring. Claim 6 A rack-driven power-assisted steering device according to claim 5, characterized in that a tool coupling portion to which a tool is coupled is formed on the outer surface of the coupling end portion. Claim 7 delete Claim 8 A rack-driven power-assisted steering device according to claim 2, characterized in that the ball nut has a circumferential fastening groove formed on the outer surface of the other end to which the nut pulley is coupled, and a fastening member is coupled to the fastening groove. Claim 9 A rack-driven power-assisted steering device according to claim 8, wherein the fastening member is formed in a ring shape with one side cut off and is coupled to the fastening groove and supported at the end of the coupling end. Claim 10 A rack-driven power-assisted steering device according to claim 1, characterized in that the inner surface of the connecting end of the nut pulley is press-fitted to the outer surface of the ball nut. Claim 11 A rack-driven power-assisted steering device according to claim 10, characterized in that the ball nut has a caulking groove formed on the outer circumference of the other end to which the nut pulley is coupled, and is caulked and fixed with the end of the coupling end of the nut pulley. Claim 12 A rack-driven power-assisted steering device according to claim 11, characterized in that one or more caulking grooves are provided, and when two or more are provided, they are arranged at equal intervals in the circumferential direction of the ball nut. Claim 13 A rack-driven power-assisted steering device according to claim 10, wherein the ball nut has a circumferential fastening groove formed on the outer surface of the other end to which the nut pulley is coupled, and a fastening member is coupled to the fastening groove. Claim 14 A rack-driven power-assisted steering device according to claim 13, wherein the fastening member is formed in a ring shape with one side cut off and is coupled to the fastening groove and supported at the end of the coupling end. Claim 15 A rack-driven power-assisted steering device according to claim 10, characterized in that the coupling end is formed to be stepped in the radial direction with the belt coupling end and protrudes in the axial direction to axially support one end of the bearing inner ring. Claim 16 delete

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