Clutch Mechanisms of Diesel Generators

The clutch mechanism is a critical component in diesel generators, responsible for transmitting the torque from the starter motor's armature to the flywheel ring gear to crank the internal combustion engine, and automatically disengaging the motor from the engine once startup is complete to protect the starter motor from damage. There are two primary types of clutch mechanisms used in such systems: spring-type and friction plate-type, each tailored to different power requirements of internal combustion engines. This article will elaborate on the structure, working principles, and application scenarios of these two clutch mechanisms.

1. Spring-Type Clutch Mechanism

The spring-type clutch mechanism is relatively simple in structure and is mounted on the starter motor's armature shaft. The right end of the drive gear is fitted into a connecting sleeve, and two sector blocks are installed in the corresponding grooves on the right end of the gear, extending into the annular groove on the left end of the splined sleeve. This configuration allows the gear and the sleeve to move axially together while enabling relative sliding between them. In its free state, the inner diameter of the clutch spring is smaller than the diameter of the corresponding outer circular surfaces of the gear and the sleeve. During installation, the spring is tightly fitted over these outer surfaces.

When the starter motor is activated, it drives the splined sleeve to rotate, causing the clutch spring to contract. Due to the tight grip of the clutch spring on the outer circular surfaces, the torque from the starter motor is transmitted to the drive gear through frictional force, which then drives the flywheel ring gear to rotate and crank the engine. Once the engine starts successfully and runs independently, the flywheel ring gear will drive the drive gear to rotate at a speed higher than that of the splined sleeve. This relative rotation causes the clutch spring to expand, loosening its grip on the outer surfaces and thus automatically disengaging the drive gear from the splined sleeve, preventing the starter motor from being driven at an excessively high speed and damaged.

The spring-type clutch mechanism is primarily used in the starting systems of medium and small power internal combustion engines. Its advantages include a simple structure, low manufacturing cost, and reliable operation under relatively low torque conditions. However, its torque transmission capacity is limited by the frictional force of the spring, making it unsuitable for high-power engine starting requirements.

2. Friction Plate-Type Clutch Mechanism

The friction plate-type clutch mechanism is more complex in structure and is designed to meet the higher torque transmission requirements of large-power internal combustion engines. The internal spline hub of the clutch mechanism is mounted on the external splined sleeve on the right side. Driven plates and driving plates are arranged alternately, and an elastic washer, a pressure ring, and an adjusting washer are installed on the splined sleeve, secured by a nut. The right end of the drive gear is provided with guide grooves, into which corresponding components are installed to prevent loosening of parts when the drive gear is in operation.

During engine startup, when the splined sleeve rotates clockwise, the internal spline hub moves leftward on the splined sleeve, pressing against the friction plates. This action clamps the driving plates and driven plates together, engaging the clutch mechanism. The torque from the starter motor is then transmitted to the drive gear through the frictional force between the friction plates, driving the flywheel ring gear to crank the engine.

After the engine starts successfully, the flywheel ring gear drives the drive gear to rotate at a speed higher than that of the splined sleeve. This relative rotation causes the internal spline hub to move rightward on the splined sleeve, releasing the pressure on the friction plates. As a result, the friction plates are loosened, and the clutch mechanism disengages, separating the starter motor from the engine to protect the motor from overspeed damage.

The maximum frictional torque that the friction plate-type clutch mechanism can transmit can be adjusted using the adjusting washer. By changing the thickness of the adjusting washer, the gap between the end of the internal spline hub and the elastic washer is altered, which in turn controls the deformation amount of the elastic washer. A larger deformation of the elastic washer results in a greater pressing force on the friction plates, increasing the maximum frictional torque that can be transmitted, and vice versa. This adjustability allows the friction plate-type clutch mechanism to be adapted to different torque requirements of large-power internal combustion engines, making it the preferred choice for high-power diesel generator starting systems.

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