Motor driven power steering device

Abstract

An invention relating to an electric power steering device is disclosed. The disclosed electric power steering device comprises: a main housing portion; a motor portion having a motor case coupled to the main housing portion, a stator disposed inside the motor case, a rotor portion disposed inside the stator, and a rotating shaft coupled to the rotor portion; and a worm shaft portion disposed inside the main housing portion, directly coupled to the rotor portion, rotated in conjunction with the rotation of the rotor portion, and transmits power of the rotor portion to a steering shaft.

Description

Technology Field

[0001] The present invention relates to an electric power steering device, and more specifically, to an electric power steering device in which the number of parts is reduced and part costs are reduced. Background Technology

[0002] Generally, a Motor Driven Power Steering (MDPS) system is a device that assists steering power using motor power without using hydraulics. An MDPS system includes a motor that generates power under ECU control and a worm shaft that rotates through the motor.

[0003] However, since connecting parts such as couplers, rubber couplings, and bearings are required to connect the motor and the worm shaft, there is a problem of increased part costs. Therefore, there is a need to improve this.

[0004] The background technology for the present invention is disclosed in Korean Registered Patent Publication No. 10-2146410 (Title of Invention: Combined Structure of Worm Shaft and Motor Shaft of Electric Power Steering Device, Registration Date: August 13, 2020). The problem to be solved

[0005] The present invention was created out of the aforementioned necessity, and aims to provide an electric power steering device that reduces the number of parts and thereby lowers parts costs. means of solving the problem

[0006] To achieve the above-mentioned purpose, the electric power steering device of the present invention comprises: a main housing portion; a motor portion having a motor case coupled to the main housing portion, a stator disposed inside the motor case, a rotor portion disposed inside the stator, and a rotating shaft coupled to the rotor portion; and a worm shaft portion disposed inside the main housing portion, directly coupled to the rotor portion, rotated in conjunction with the rotation of the rotor portion, and transmits power of the rotor portion to a steering shaft.

[0007] In addition, the worm shaft portion is characterized by comprising: a worm shaft body disposed inside the main housing portion and having a worm gear formed along its outer surface; and a worm shaft coupling portion connected to the worm shaft body and coupled to the rotor portion.

[0008] In addition, the rotor portion comprises a plurality of rotor cores arranged adjacent to each other and having a plurality of machining holes formed in the circumferential direction, and the worm shaft coupling portion comprises a worm shaft coupling body formed integrally with the worm shaft body; and a plurality of coupling protrusions formed protruding to one side from the worm shaft coupling body and fitted into each of the plurality of machining holes.

[0009] In addition, the plurality of the above-mentioned coupling protrusions are formed circumferentially spaced apart on the worm shaft coupling body and are positioned to correspond to each of the plurality of processing holes.

[0010] In addition, the worm shaft body is characterized by comprising: a first worm shaft body in which the worm gear is formed along the outer surface; a second worm shaft body connected to the first worm shaft body and having a contact portion that contacts a first bearing; and a connecting portion that extends from one side of the second worm shaft body and is connected to the second worm shaft body. Effects of the invention

[0011] Since the worm shaft portion of the electric power steering device according to the present invention is directly connected to the motor portion, there is no need for separate connecting parts, which reduces the number of parts and thus has the effect of reducing parts costs.

[0012] In addition, since the worm shaft portion is directly connected to the motor portion, the number of parts can be further reduced and parts costs can be reduced as parts supporting rotation, such as bearings, are not required, and the overall length of the electric power steering device can be reduced, thereby reducing the overall size of the parts. Brief explanation of the drawing

[0013] FIG. 1 is a schematic perspective view of an electric power steering device according to one embodiment of the present invention. Figure 2 is an enlarged view of part A of Figure 1. FIG. 3 is a perspective view of a worm shaft, a rotor part of a motor part, and a rotating shaft of an electric power steering device according to one embodiment of the present invention. Figure 4 is a cross-sectional view of AA' of Figure 3. FIG. 5 is an exploded perspective view of the worm shaft, the rotor part of the motor part, and the rotation shaft of an electric power steering device according to one embodiment of the present invention. Figure 6 is a cross-sectional view of BB' of Figure 5. FIG. 7 is a perspective view of the worm shaft, the rotor part of the motor part, and the rotation axis of an electric power steering device according to one embodiment of the present invention, viewed from a different direction. Specific details for implementing the invention

[0014] Hereinafter, an electric power steering device according to an embodiment of the present invention will be described with reference to the attached drawings.

[0015] In this process, the thickness of lines or the size of components depicted in the drawings may be exaggerated for the sake of clarity and convenience of explanation. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intent or convention of the user or operator. Therefore, the definitions of these terms should be based on the content throughout this specification.

[0016] FIG. 1 is a schematic perspective view of an electric power steering device according to an embodiment of the present invention, FIG. 2 is an enlarged view of part A of FIG. 1, FIG. 3 is a perspective view of a worm shaft, a rotor part of a motor unit, and a rotation axis of an electric power steering device according to an embodiment of the present invention, FIG. 4 is a cross-sectional view AA' of FIG. 3, FIG. 5 is an exploded perspective view of a worm shaft, a rotor part of a motor unit, and a rotation axis of an electric power steering device according to an embodiment of the present invention, FIG. 6 is a cross-sectional view BB' of FIG. 5, and FIG. 7 is a perspective view of a worm shaft, a rotor part of a motor unit, and a rotation axis of an electric power steering device according to an embodiment of the present invention viewed from a different direction.

[0017] Referring to FIGS. 1 to 4, an electric power steering device (1) according to one embodiment of the present invention includes a main housing part (100), a motor part (200), and a worm shaft part (300). The main housing part (100) is coupled with a motor case (210) of the motor part (200), and a worm shaft part (300) is disposed inside.

[0018] The motor section (200) is coupled with the main housing section (100) and includes a motor case (210) and a motor (220). The motor case (210) is coupled with the main housing section (100).

[0019] The motor (220) is a device that generates steering assistance force, is controlled by an ECU (Electronic Control Unit), and includes a stator (221), a rotor (222), and a rotation shaft (223). The stator (221) is placed inside the motor case (210).

[0020] The rotor section (222) is positioned inside the stator (221) and includes a plurality of rotor cores (222a) positioned adjacent to each other. A central hole section (222b) is formed in the center of the rotor core (222a), and a plurality of machining holes (222c) are formed in the circumferential direction relative to the central hole section (222b).

[0021] The rotation shaft (223) is coupled to the central hole portion (222b) and is located inside the plurality of coupling protrusions (322) of the worm shaft portion (300). At this time, the rotor portion (222) is formed to surround the outside of the rotation shaft (223).

[0022] Specifically, when current is applied to the stator (221), the rotor (222) rotates due to the electrical interaction between the stator (221) and the rotor (222), and accordingly, the rotation axis (223) rotates in conjunction with the rotation of the rotor (222).

[0023] The worm shaft portion (300) is positioned inside the main housing portion (100) and is directly coupled to the rotor portion (222). It rotates in conjunction with the rotation of the rotor portion (222) and transmits the power of the rotor portion (222) to the steering shaft (S). The worm shaft portion (300) is coupled to the rotor portion (222) and can rotate by receiving power from the motor portion (200).

[0024] The worm shaft portion (300) meshes with a worm wheel (not shown) formed on the steering shaft (S) and transmits power from the motor portion (200) to the steering shaft (S). The steering shaft (S) is connected to a steering wheel (not shown), and the steering angle changes as the steering wheel rotates.

[0025] The worm shaft section (300) includes a worm shaft body (310) and a worm shaft coupling section (320). The worm shaft body (310) is positioned inside the main housing section (100), and a worm gear (311b) is formed along the outer surface. The worm shaft coupling section (320) is connected to the worm shaft body (310) and coupled to the rotor section (222).

[0026] Specifically, the worm shaft coupling part (320) includes a worm shaft coupling body (321) and a plurality of coupling protrusions (322). The worm shaft coupling body (321) is integrally extended from the worm shaft body (310).

[0027] A plurality of coupling protrusions (322) are formed to protrude from one side of the worm shaft coupling body (321) and are each fitted into a plurality of machining holes (222c). That is, the coupling protrusions (322) can be in close contact with the machining holes (222c). In addition, the cross-section of the coupling protrusions (322) and the cross-section of the machining holes (222c) may be the same. As a result, relative movement of the coupling protrusions (322) on the machining holes (222c) can be prevented. Consequently, it is possible to prevent the coupling protrusions (322) from moving with play on the rotor part (222) due to rotation and shaking of the rotor part (222).

[0028] A plurality of coupling protrusions (322) are formed on the worm shaft coupling body (321) at a circumferential spacing and are positioned to correspond to a plurality of machining holes (222c). At this time, the worm shaft coupling body (321) comes into contact with the rotation axis (223).

[0029] The worm shaft body (310) includes a first worm shaft body (311), a second worm shaft body (312), and a connecting part (313). A worm gear (311b) is formed along the outer surface of the first worm shaft body (311).

[0030] Specifically, the first worm shaft body (311) includes a first worm shaft body block (311a) and a worm gear (311b). The first worm shaft body block (311a) is connected to the second worm shaft body (312) described later, and a bearing coupling portion (311c) is formed at the end to which a second bearing (500) is coupled. The worm gear (311b) is formed along the outer surface of the first worm shaft body block (311a).

[0031] The second worm shaft body (312) is connected to the first worm shaft body (311) and has a contact portion (312b) that contacts the first bearing (400). Specifically, the second worm shaft body (312) includes a second worm shaft body block (312a) and a contact portion (312b). One end of the second worm shaft body block (312a) is connected to the first worm shaft body (311), and the other end is connected to a connecting portion (313). The contact portion (312b) is formed in a ring shape and extends outward from the second worm shaft body block (312a) and contacts one side of the first bearing (400). This prevents the first bearing (400) from being displaced from its proper position.

[0032] The connecting portion (313) is formed to extend to one side from the second worm shaft body (312) and is connected to the second worm shaft body (312). At this time, the radius of the connecting portion (313) may be smaller than the radius of the second worm shaft body block (312a) and the first worm shaft body block (311a).

[0033] In this way, compared to conventional technology that requires connecting parts such as a rubber coupling along with a coupler to connect the worm shaft part (300) and the motor part (200), the plurality of connecting protrusions (322) of the worm shaft part (300) are directly connected to the plurality of processing holes (222c) formed in the rotor part (222) provided in the motor part (200), so that separate connecting parts are not required, thereby reducing the number of parts and reducing the cost of parts.

[0034] Furthermore, in the present invention, as the gap (W) between the first bearing (400) and the stator (221) of the motor (220) is narrowed compared to the conventional technology, parts that support rotation, such as bearings, are not required, so the number of parts is further reduced and the cost of parts can be reduced, and the overall length of the electric power steering device (1) is reduced, so the size of the overall parts can be reduced.

[0035] Hereinafter, with reference to FIGS. 1 and FIGS. 2, we will examine the operation and effects of an electric power steering device according to an embodiment of the present invention.

[0036] When the motor (220) of the motor unit (200) is operated, the worm shaft unit (300) connected to the motor (220) is directly connected to the motor (220) and rotates by receiving power from the motor (220). At this time, the first bearing (400) supports the rotation of the worm shaft unit (300).

[0037] Specifically, when current is applied to the stator (221), the rotor (222) rotates due to the electrical interaction between the stator (221) and the rotor (222), and the rotation axis (223) rotates in conjunction with the rotation of the rotor (222).

[0038] At this time, the worm shaft portion (300) is directly connected to the rotor portion (222) and also comes into contact with the rotation axis (223), causing the worm shaft portion (300) to rotate. That is, a plurality of coupling protrusions (322) provided on the worm shaft portion (300) are each coupled to a plurality of machining holes (222c) of the rotor portion (222).

[0039] As a result, the worm shaft part (300) and the motor part (200) can be connected to each other without the need for separate connecting parts, so the number of parts is reduced and the cost of parts can be reduced.

[0040] Furthermore, as the gap (W) between the first bearing (400) and the stator (221) of the motor (220) becomes narrower than in conventional technology, parts that support rotation, such as bearings, are not required. In other words, the number of parts is further reduced, so the cost of parts can be reduced, and the overall length of the electric power steering device (1) is reduced, so the size of the overall parts can be reduced.

[0041] When the worm shaft part (300) rotates by receiving power from the motor (220), the rotational force of the worm shaft part (300) is transmitted through the steering shaft (S) to the steering wheel connected to the steering shaft (S) to operate the steering wheel.

[0042] Specifically, the worm shaft portion (300) meshes with a worm wheel (not shown) formed on the steering shaft (S), and the worm wheel rotates in conjunction with the rotation of the worm shaft portion (300). Accordingly, power from the motor portion (200) is transmitted to the steering shaft (S), and the steering wheel connected to the steering shaft (S) rotates, thereby changing the steering angle.

[0043] Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom.

[0044] Therefore, the true technical scope of protection of the present invention should be determined by the following claims. Explanation of the symbols

[0045] 1 : Electric power steering system 100 : Main housing section 200 : Motor section 210 : Motor case 220 : Motor 221: Stator 222: Rotor 222a: Rotor core 222b: Central hole section 222c : Machining hole 223 : Rotation axis 300 : Worm shaft section 310 : Worm shaft body 311: First worm shaft body 311a: First worm shaft body block 311b: Worm gear 311c: Bearing connection 312 : Second worm shaft body 312a : Second worm shaft body block 312b : Contact part 313 : Connection part 320: Worm shaft coupling part 321: Worm shaft coupling body 322 : Connecting projection 400 : First bearing 500 : 2nd bearing

Claims

Claim 1 An electric power steering device comprising: a main housing portion; a motor portion having a motor case coupled to the main housing portion, a stator disposed inside the motor case, a rotor portion disposed inside the stator, and a rotating shaft coupled to the rotor portion; and a worm shaft portion disposed inside the main housing portion, directly coupled to the rotor portion, rotated in conjunction with the rotation of the rotor portion, and transmits power of the rotor portion to a steering shaft; wherein the worm shaft portion comprises a worm shaft body disposed inside the main housing portion and having a worm gear formed along its outer surface, and the worm shaft body comprises: a first worm shaft body having the worm gear formed along its outer surface; a second worm shaft body block connected to the first worm shaft body; and a second worm shaft body extending outward from the second worm shaft body block, formed in a ring shape, and having a contact portion that contacts one side of a first bearing. Claim 2 An electric power steering device according to claim 1, characterized in that the worm shaft portion further comprises a worm shaft coupling portion connected to the worm shaft body and coupled to the rotor portion. Claim 3 An electric power steering device according to claim 2, wherein the rotor portion comprises a plurality of rotor cores arranged adjacently to each other and having a plurality of machining holes formed in the circumferential direction, and the worm shaft coupling portion comprises: a worm shaft coupling body formed integrally with the worm shaft body; and a plurality of coupling protrusions formed protruding to one side from the worm shaft coupling body and fitted into each of the plurality of machining holes. Claim 4 An electric power steering device according to claim 3, wherein a plurality of the coupling protrusions are formed circumferentially spaced apart on a worm shaft coupling body and are positioned to correspond to a plurality of machining holes, and the shape of the machining holes is formed to correspond to at least a part of the coupling protrusions. Claim 5 An electric power steering device according to claim 3, further comprising: a connecting part that is formed to extend to one side from the second worm shaft body and connected to the second worm shaft body.

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