Rear Wheel Steering Apparatus Resolving Assembly Complexity
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Solution Overview
Problem
Existing rear wheel steering apparatuses for vehicles face challenges in cost, weight reduction, and efficient assembly, particularly due to complex supporting structures and the need for press-fitting of metal ring gears, which increases costs and complicates manufacturing.
Innovation Solution
A rear wheel steering apparatus with a housing connected via connection members to the suspension mechanism, incorporating a planetary gear mechanism with a non-rotatable ring gear held by a cylindrical holding member and a lock portion, using synthetic resin for the ring gear and metal for other components, and a one-end-supported rod structure for simplified assembly and cost reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ring gear is made of metal and press-fitted to the housing, then torque transmission reliability is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The ring gear is made of resin material instead of metal, using a cheaper material that can be molded directly into the housing. This eliminates the need for expensive press-fitting processes while maintaining sufficient durability for the application.
Solution Approach 2:
The ring gear is formed integrally with the housing through mold co-molding, merging two previously separate components (housing and ring gear) into a single integrated structure. This eliminates the need for separate manufacturing and assembly processes.
2Ease of manufacture
If the ring gear is made of resin material, then manufacturing cost is reduced, but forming the ring gear integral with the housing becomes difficult
Solution Approach 1:
The housing and ring gear are molded together in a single integrated structure using mold co-molding technology. This allows the ring gear to be formed as an integral part of the housing without requiring separate assembly steps.
Solution Approach 2:
The housing serves multiple functions: it provides structural support for the actuator and simultaneously forms the ring gear of the planetary mechanism through integral molding. This multi-functionality reduces the number of parts and assembly steps.
3Stability of the object's composition
If a both-ends-supported structure is used for the rod, then structural stability is improved, but the supporting structure becomes complicated
Solution Approach 1:
One of the support points for the rod is removed, changing from a both-ends-supported structure to a one-end-supported structure. This simplifies the supporting structure while the remaining support is sufficiently reinforced to maintain stability.
4Productivity
If a one-end-supported structure is used for the rod, then assembly efficiency is improved, but structural strength may be insufficient
Solution Approach 1:
The single support point for the rod is designed with enhanced local strength through increased contact area and optimized structural features at the support location, compensating for the reduced support points while maintaining overall stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables reliable torque transmission, easy assembly, reduced costs, and weight, while maintaining structural integrity, addressing the inefficiencies and cost issues of previous designs.
Implementation Method 1
a planetary gear mechanism including a sun gear connected to an output shaft of the electric motor, a ring gear supported within the housing to be non-rotatable, a planetary gear meshing with the ring gear and the sun gear
Implementation Method 2
the planetary gear mechanism decelerating an output of the electric motor
Implementation Method 3
a linear motion mechanism including a nut member connected to the planetary gear mechanism and constituting the carrier, and a rod threadedly engaged with the nut member and connected to the second connection member, the linear motion mechanism converting a rotary motion of the nut member to a linear motion of the rod
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
A rear wheel steering apparatus for a vehicle includes a housing (1), an electric motor (3a), a planetary gear mechanism (30), a linear motion mechanism (3c) including a nut member (36) and a rod (2) threadedly engaged with the nut member, the housing including a cylindrical body (10) which includes a lock portion (14) provided at an inner surface of the cylindrical body, the housing including a connection cover (11), a cylindrical holding member (34) holding a ring gear (33) within the cylindrical body in a state where the ring gear is prevented from rotating, and a bearing (37), wherein the bearing and the cylindrical holding member are disposed and held between the lock portion and the connection cover, and the cylindrical holding member is held to be non-rotatable relative to the cylindrical body.