Electric Working Machine Motor Current Control
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Solution Overview
Problem
Electric working machines face challenges in enhancing drive capability of the output shaft without enlarging the machine, as large gears required for improved drive capability increase the device's size.
Innovation Solution
Incorporating a controller that limits motor current to a specified upper limit value, preventing excessive torque from being applied to the transmitting device, even when the motor generates more torque than the device can handle, and allowing the motor to be energized with currents higher than the allowable value to improve drive capability without enlarging the machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large gears are used in the transmitting device to improve drive capability, then the drive capability of the output shaft is improved, but the transmitting device and electric working machine become enlarged
Solution Approach 1:
The patent applies dynamics by making the upper limit current value variable rather than fixed. The controller adjusts the upper limit current value based on operating conditions (such as motor speed, load, temperature), allowing the system to dynamically optimize between drive capability and protecting the transmitting device. This resolves the contradiction by enabling high current (and thus high drive capability) only when conditions permit, while preventing damage under other conditions.
2Power
If the motor is energized with current larger than the allowable current value, then the drive capability is improved, but torque exceeding the allowable torque is applied to the transmitting device
Solution Approach 1:
The patent implements feedback control by continuously monitoring motor current and comparing it against the dynamically determined upper limit current value. The controller adjusts the current supplied to the motor based on this comparison, ensuring that the current (and resulting torque) never exceeds safe limits for the transmitting device while maximizing drive capability when within safe operating parameters.
Solution Approach 2:
The patent changes the parameter of upper limit current value from a fixed constant to a variable parameter that adjusts based on operating conditions. This allows the system to permit higher currents (improving drive capability) when conditions such as motor speed or load are favorable, while automatically reducing the limit when conditions approach dangerous thresholds, thus protecting the transmitting device.
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
This solution effectively protects the transmitting device from damage by limiting torque and allows for improved drive capability of the output shaft without increasing the machine's size, ensuring the motor current remains within safe limits.
Implementation Method 1
a motor (4), a transmitting device (30), a drive device (40), and a controller (46). The transmitting device (30) is configured to transmit rotation of the motor (4) to an output shaft (7)
Implementation Method 2
The detector is configured to detect a value of motor current flowing in the motor via the drive device
Data Source
AI summary
An electric working machine according to one aspect of the present disclosure includes an output shaft, a motor, a transmitting device, a drive device, a controller, and a current path. The transmitting device has transmittable allowable torque and transmits rotation of the motor to the output shaft. The drive device energizes the motor with electric supply from a battery in accordance with a command from outside the electric working machine. The current path is configured to be able to energize the motor with a current value larger than an allowable current value required to limit torque generated in the transmitting device due to rotation of the motor to the allowable torque or smaller.