Classification by Elasticity
Drive shafts can be categorized differently based on their key component, the universal joint. Based on whether the universal joint exhibits significant elasticity in the direction of torsion, they can be divided into rigid universal joint drive shafts and flexible universal joint drive shafts.
1. Rigid universal joint: Power is transmitted through a hinged connection between components.
2. Flexible universal joint: Power is transmitted through elastic components and provides a cushioning and vibration reduction function.
Classification by Angular Velocity
Rigid universal joints can be further divided into unequal velocity joints (such as cross-axis universal joints), quasi-constant velocity joints (such as duplex universal joints and tripod universal joints), and constant velocity joints (such as ball and fork universal joints). Constant velocity refers to whether the driven shaft rotates at the same angular velocity as the driving shaft. Of course, the average rotational speeds of the driving and driven shafts are equal.
1. Constant Velocity Joint:
A universal joint in which the angular velocities of the driving and driven shafts remain equal even when the angle between them changes is called a constant velocity joint or constant angular velocity joint. They are primarily used in wheel drive systems such as steering drive axles and disconnecting drive axles, and are primarily used for power transmission in passenger cars.
2. Unequal Velocity Joint:
A universal joint in which the angular velocities of the driving and driven shafts remain unequal even when the angle between them changes is called an unequal velocity joint, also known as a cross-axis joint. Cross-axis rigid joint drive shafts are commonly used in automotive drivetrains and have a long history. Rear-wheel drive cars often use cross-axis joint drive shafts, although some high-end cars also use constant velocity ball joints. Front-wheel drive cars often use constant velocity joints-constant velocity joints are also a type of drive shaft, just with a different name. The term "drive shaft" generally refers to a cross-axis rigid joint drive shaft. Cross-shaft rigid universal joints are primarily used to transmit angular changes. They typically consist of a flanged yoke, a cross-shaft with needle roller bearing assembly, a universal joint yoke or sliding yoke, an intermediate connecting yoke or splined shaft yoke, and an axial retainer for the needle roller bearing. The flanged yoke is a fork-shaped component with a flange. It is typically forged from medium-carbon steel or medium-carbon alloy steel, but can also be sand-cast from ductile iron or precision-cast from medium-carbon steel or medium-carbon high-quality alloy steel. The flanged yoke typically has a flat flange, but some may have a trapezoidal toothed end flange. The cross-shaft with needle roller bearing assembly typically includes four needle roller bearings, a cross-shaft, and a grease nipple. The needle roller bearing typically consists of several needle rollers, a bearing cup, and a multi-edge rubber oil seal (some with a frame). Some needle roller bearings also include a circular washer with an oil groove. Made of nylon, copper, or other materials, it primarily reduces axial play in the universal joint and improves the dynamic balance of the drive shaft. The universal joint fork is a fork-shaped component, typically forged from medium-carbon steel or medium-carbon alloy steel, though some precision castings are also available. The axial retaining elements of a needle roller bearing are typically circlips (internal and external snap-fit type) for the bore (or shaft), bearing pressure plates, locking plates, bolts, and more.