Planetary Transmission Assembly for Compact Impact Wrenches
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Solution Overview
Problem
Impact wrenches require compact designs that are easy to control and operate in narrow spaces while maintaining high performance and efficiency.
Innovation Solution
The impact wrench incorporates a transmission assembly with a main shaft and planetary gears, a rear cover with an inner ring gear, and a sliding contact design to enhance compactness and control, along with a brushless inner rotor motor for efficient power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the impact wrench is designed to be compact for narrow space operation, then the ease of operation in narrow spaces is improved, but the device complexity increases due to the need for efficient power transmission in limited space
Solution Approach 1:
The patent employs a planetary gear transmission assembly where planet gears are nested around a central sun gear, and the entire transmission assembly is integrated within the motor housing. This nested configuration allows multiple gear stages to be compacted into a small volume, enabling the impact wrench to operate in narrow spaces while maintaining the necessary torque multiplication and transmission complexity.
2Productivity
If the transmission assembly uses planetary gears with sliding contact, then the productivity and power transmission efficiency are improved, but the wear and material durability challenges increase
Solution Approach 1:
The patent specifies that the rear cover material hardness is greater than or equal to 20 HRC, and the contact region is carburized to enhance surface hardness and wear resistance. These parameter changes in material properties allow the sliding contact between the rear cover and main shaft to maintain high productivity through efficient power transmission while mitigating wear and ensuring long-term reliability of the transmission assembly.
3Power
If the gear outer diameter is greater than the rotor shaft diameter for effective power transmission, then the power transmission capability is improved, but the volume of the motor housing increases
Solution Approach 1:
The patent utilizes the radial dimension by positioning the planet gears around the central sun gear, allowing the gear outer diameter to be greater than the rotor shaft diameter for effective power transmission. The planetary arrangement distributes the load across multiple gear contacts in the radial direction, enabling high power transmission capability while keeping the axial length and overall housing volume compact, thus resolving the contradiction between power transmission capability and housing volume.
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 design allows for a compact and easily controllable impact wrench that maintains high torque and impact frequency, suitable for narrow spaces and improved user control, and efficiency.
Implementation Method 1
an electric motor accommodated in the housing and including a stator assembly and a rotor assembly, where the rotor assembly includes a rotor shaft
Implementation Method 2
The transmission assembly includes a main shaft disposed in the extension direction of the rotor shaft and including multiple planetary shafts, where multiple planet gears are disposed around the multiple planetary shafts
Implementation Method 3
When the multiple planet gears rotate in the inner ring gear, the rear cover is in sliding contact with the main shaft
Data Source
AI summary
An impact wrench includes a housing, an electric motor, an anvil, a grip, an impact assembly, and a transmission assembly, where the transmission assembly is disposed between the electric motor and the impact assembly. The transmission assembly includes a main shaft disposed in the extension direction of the rotor shaft and including multiple planetary shafts, where multiple planet gears are disposed around the multiple planetary shafts, respectively, and a gear extends into the main shaft and drives the multiple planet gears; and a rear cover surrounding at least part of the main shaft from the rear to the front, where the rear cover is formed with an inner ring gear, and the inner ring gear meshes with the multiple planet gears. When the multiple planet gears rotate in the inner ring gear, the rear cover is in sliding contact with the main shaft.