Strain Wave Gear Grease Heating for Cold Start Torque Control
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Solution Overview
Problem
Strain wave gearing devices struggle to start in low temperature environments due to high viscosity grease, leading to increased rotational torque and inability to start with low capacity motors, especially at temperatures below -30°C or -55°C, where the grease's plasticity and viscosity hinder effective lubrication and operation.
Innovation Solution
A strain wave gearing device with a flexible externally toothed gear and a grease temperature control mechanism, featuring a heater that contacts the inner peripheral surface of the externally toothed gear over its entire circumference, allowing precise temperature control of the grease portion surrounding the wave generator to reduce starting torque and ensure reliable operation in extreme cold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grease is used for lubrication in low temperature environments, then lubrication is provided to the strain wave gearing device, but the viscosity and plasticity of the grease increase, causing rotational torque to suddenly increase and preventing the device from starting with a low capacity motor
Solution Approach 1:
The patent applies parameter changes by heating the grease to alter its physical properties. Specifically, the grease temperature is raised from extremely low temperatures (e.g., -55°C or lower) to a higher temperature range, which reduces the grease's viscosity and plasticity. This parameter change enables the grease to provide adequate lubrication while maintaining acceptable starting torque levels, allowing the strain wave gearing device to start reliably with low capacity motors in extremely cold environments.
Solution Approach 2:
The patent implements preliminary action by heating the grease before the strain wave gearing device attempts to start. The grease temperature control mechanism pre-heats the grease to reduce its viscosity and plasticity prior to the starting moment, ensuring that the rotational torque remains within acceptable limits when the motor starts. This preliminary heating action prevents the high starting torque problem that would otherwise occur in extremely low temperature environments.
2Force
If a heater is used to heat the grease in extremely low temperature environments, then the starting torque is reduced and the device can start, but the grease near the heater may be overheated to a temperature higher than room temperature, resulting in insufficient lubrication performance
Solution Approach 1:
The patent applies local quality by positioning the heater to heat only specific portions of the grease where needed, rather than heating all grease uniformly. The grease temperature control mechanism is designed to provide localized heating to the grease in critical areas, maintaining appropriate temperature gradients that reduce starting torque while preventing overheating in other regions. This selective heating approach ensures sufficient lubrication performance is maintained throughout the strain wave gearing device.
Solution Approach 2:
The patent implements feedback through the grease temperature control mechanism, which monitors and regulates the grease temperature to prevent overheating. The mechanism adjusts the heating input based on the actual grease temperature, ensuring that the grease near the heater does not exceed optimal temperature ranges. This feedback control maintains the balance between reducing starting torque and preserving adequate lubrication performance.
3Force
If the amount of heat input is increased to heat the grease inside the wave generator, then the grease temperature rises and starting torque decreases, but it takes more time to heat the grease and the device complexity increases
Solution Approach 1:
The patent applies partial action by heating only the necessary portions of the grease rather than attempting to heat all grease uniformly to high temperatures. The heater is positioned and controlled to provide sufficient heating to reduce starting torque in critical areas without applying excessive heat input that would require longer heating times. This partial heating approach achieves the desired torque reduction more quickly and efficiently.
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 the strain wave gearing device to start reliably in low temperature environments by reducing the viscosity and plasticity of the grease, allowing operation with a low capacity motor, while minimizing heat input to prevent overheating and maintain sufficient lubrication performance.
Implementation Method 1
heating the grease portion covering an outer peripheral side portion of the wave generator... reduce the viscosity and plasticity of the grease
Data Source
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AI summary
A strain wave gearing device (1) has a grease temperature control mechanism (15) for controlling the grease temperature of a portion of grease (16a), of the grease (16) filled inside an externally toothed gear (6) of the strain wave gearing device, the portion of the grease being disposed on the outer peripheral side portion of a wave generator (7). The grease temperature control mechanism (15) has a circular heater (17) facing the outer peripheral side portion of the wave generator (7) over the entire circumference from a direction of a device central axis line (1a). By controlling the grease temperature of a specified portion inside the externally toothed gear (6), it is possible to reliably start the strain wave gearing device even in an extremely low temperature environment where the grease solidifies.