Sintered Gear Stepped Peripheral Design
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Solution Overview
Problem
Existing electric actuators using ball screw mechanisms face issues with gear tooth damage and deformation during manufacturing due to insufficient binding degree of powder in sintered alloy gears, leading to bowing and accuracy degradation.
Innovation Solution
A sintered gear design with spur teeth, a central hole, a boss, and a peripheral portion with a stepped configuration, where the peripheral portion has an axially larger thickness than the teeth, and a controlled clearance between the tooth and peripheral portion, along with lightening holes to maintain strength and rigidity while reducing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the peripheral portion has an axially large thickness than the teeth, then manufacturing accuracy is improved and tooth damage is prevented, but device complexity increases due to stepped configuration
Solution Approach 1:
The gear body is segmented into distinct portions with different axial thicknesses: a first peripheral portion with axially large thickness to prevent tooth damage, and a second peripheral portion with smaller thickness. This segmentation allows each region to fulfill its specific function while resolving the contradiction between manufacturing accuracy and structural simplicity.
Solution Approach 2:
Different regions of the gear are given different local qualities in terms of axial thickness. The first peripheral portion has axially large thickness specifically where tooth damage prevention is critical, while other regions maintain smaller thickness. This local differentiation optimizes manufacturing accuracy without unnecessarily complicating the entire gear structure.
2Weight of moving object
If lightening holes are formed between the peripheral portion and boss, then weight is reduced while strength and rigidity are maintained, but manufacturing complexity increases
Solution Approach 1:
The gear structure is segmented by forming lightening holes that divide the solid material into regions separated by voids. These holes are strategically positioned between the peripheral portion and boss, creating a lightweight structure that maintains structural integrity while reducing overall weight.
Solution Approach 2:
The gear incorporates a porous or hollow structure through lightening holes, transforming the solid gear body into a structure with controlled voids. This porous configuration reduces weight while maintaining the necessary strength and rigidity for gear operation.
3Reliability
If the clearance amount between tooth and peripheral portion is limited to 0.1-0.5mm, then tooth damage is prevented, but manufacturing tolerance requirements increase
Solution Approach 1:
The clearance amount between the tooth and peripheral portion is optimized to a specific parameter range of 0.1-0.5mm. This parameter change ensures sufficient space to prevent tooth damage during operation while establishing clear manufacturing tolerance boundaries that guide the manufacturing process.
Solution Approach 2:
The stepped configuration and lightening holes are designed in advance to pre-establish the optimal clearance of 0.1-0.5mm between the tooth and peripheral portion. This preliminary structural arrangement ensures that the desired clearance is achieved during manufacturing, preventing tooth damage before the gear enters service.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An object of the present invention is to provide a sintered gear having improved quality which can prevent the tooth damage and deformation such as bow of the teeth during manufacturing steps of the sintered gear and an electric actuator provided with such a sintered gear. According to the present invention, there is provided a gear formed of sintered alloy comprising spur teeth formed on a circumference of the gear; a central hole on the center of the gear; a boss formed around the central hole; and a peripheral portion formed radially inner side of the teeth, a thickness of a region between the boss and the peripheral portion being thinner than that of the boss characterized in that the peripheral portion is formed on at least one side of the gear and has an axially large thickness, and also provided an electric actuator comprising a housing; an electric motor mounted on the housing; a speed reduction mechanism for transmitting rotational force of the motor to a ball screw mechanism; and the ball screw mechanism being able to convert the rotational motion of the electric motor to the axial linear motion of a driving shaft and comprising a nut and a screw shaft, the nut being formed with a helical screw groove on its inner circumference, secured on its outer circumference an output gear forming part of the speed reduction mechanism and supported rotationally but axially immovably relative to the housing by a pair of supporting bearings mounted on the housing, and the screw shaft formed with a helical screw groove on the outer circumference corresponding to the helical screw groove of the nut, adapted to be inserted into the nut via a large number of balls, and supported not rotationally but axially movably relative to the housing characterized in that an end face of an inner ring of one supporting bearing of the pair of supporting bearings and a side surface of the boss are closely contacted each other, and that the output gear is configured by a gear defined in any one of claims 1∼5.