What is a CV Joint?
A constant velocity (CV) joint is a mechanical component used in automotive applications to transmit torque from the transmission to the drive wheels while allowing for changes in the angle between the input and output shafts. It ensures constant rotational speed is maintained, even when the shafts are not in a straight line. Key features of CV joints include:
- Ability to transmit torque at a constant velocity, even with angular displacement between shafts
- Plunging capability, allowing for axial movement of the shafts
- Commonly used in front-wheel-drive and independent suspension systems
Types of CV Joints
The two main types of CV joints are:
- Fixed CV Joints: These allow for angular displacement between the shafts but no axial movement beyond normal tolerances. Examples include the tripod joint and the Rzeppa joint.
- Plunging CV Joints: These permit both angular and axial displacement between the shafts. Examples include the double offset joint and tripod plunging joint.
How Does a CV Joint Work?
CV Joint Structure and Components
A CV joint consists of the following key components:
- Outer race/housing
- Inner race/trunnion
- Roller assemblies with inner and outer rings
- Cage to hold the roller assemblies in place
Operating Principle
The outer race is connected to the drive shaft, while the inner race is connected to the driven shaft. The roller assemblies are positioned between the inner and outer races, allowing them to pivot and slide as the angle between the shafts changes. This unique design enables constant velocity rotation by:
- Allowing axial movement of the roller assemblies along the tracks of the outer race
- Maintaining constant contact between the roller assemblies and the inner/outer races
A Step-by-step Guide to Installing a CV Joint
Preparation
- Ensure the CV joint components are compatible and undamaged
- Clean the components thoroughly to remove any dirt or debris
- Apply the recommended grease to the internal components
Disassembly (if replacing an existing CV joint)
- Use a specialized CV joint removal tool to separate the joint from the axle without damaging the components
- For remanufactured joints, inspect and optimize machining parameters of key components like the housing, inner race, and cage for proper fit and durability
Assembly Process
- Align the window holes of the cage with the grooves of the inner race and insert balls to create a sub-assembly
- Insert the sub-assembly into the outer race, ensuring the balls engage with the outer grooves to phase-position all components
- For fixed joints, use a holder with spherical surfaces to aid in aligning and inserting the balls into the pockets
- Ovalize the outer race if needed to allow insertion of the inner race while minimizing deformation
- Install any seals, boots, or clamps to contain the grease and prevent contamination
Installation
- Mount the assembled CV joint onto the vehicle axle, ensuring proper fit and alignment
- Torque any fasteners to specified values
- Refill the joint with fresh grease through the grease fittings
Testing and Adjustment
- Check for smooth rotation and plunging motion of the joint through its full range of angles
- Adjust the joint position if needed based on vibration analysis or feedback from instrumented joints
- Verify proper sealing by checking for grease leaks
By following this comprehensive process, ensuring precision assembly, and using high-quality components optimized for remanufacturing, a durable and smoothly operating CV joint installation can be achieved to meet the demands of modern vehicles.
Applications of CV Joint
CV joints are widely used in automotive applications where a constant rotational velocity is required for power transmission through an angle. Some key applications include:
- Front-wheel drive vehicles: Two CV joints per axle are used in the front suspension.
- Rear-wheel drive vehicles: CV joints are used on propeller shafts and driveshafts.
- All-wheel drive and four-wheel drive vehicles: CV joints transmit torque from the powertrain to the final drive components.
Application Cases
| Product/Project | Technical Outcomes | Application Scenarios |
|---|---|---|
| GKN Automotive eDrive Technology | Utilises a compact and lightweight design, enabling a high torque density of up to 3,500 Nm per tonne. This results in a power-dense system suitable for electric vehicles. | Electric and hybrid vehicles, providing efficient power transmission from the electric motor to the wheels. |
| Schaeffler Torque Vectoring System | Employs active differential technology to distribute torque between the rear wheels, improving traction and handling. This enhances vehicle dynamics and stability during cornering. | High-performance vehicles, sports cars, and luxury sedans, enabling enhanced driving dynamics and agility. |
| BorgWarner DualTronic Transmission | Combines a dual-clutch transmission with an integrated electric motor, enabling pure electric driving, hybrid operation, and engine-powered driving modes. This offers improved fuel efficiency and reduced emissions. | Hybrid and plug-in hybrid electric vehicles, providing a seamless transition between electric and combustion engine power sources. |
| Dana TwinSpider Technology | Incorporates two CV joints in a single compact unit, reducing weight and packaging space requirements. This technology enables a more efficient and lightweight driveline design. | Compact and lightweight vehicle architectures, such as electric and hybrid vehicles, where space and weight optimisation are crucial. |
| NTN-SNR Outrunner Motor | Integrates a high-efficiency electric motor with a constant velocity joint, enabling direct power transmission to the wheels. This results in a compact and lightweight electric drivetrain solution. | Electric vehicles, particularly in urban and last-mile delivery applications, where space and efficiency are critical factors. |
Latest Innovations of CV Joint
Novel CV Joint Designs
- Angled offset ball-type CV joint with symmetrical outer and inner race centers, increasing maximum joint angle to 49° and reducing ball-race contact pressure to 15 kPa
- CV joint with divided outer race groove (curved, inclined, curved) and divided inner race groove (curved, inclined, curved) for increased joint angle without size increase
- Direct pinion mount CV joint assemblies integrating gear/pinion components for cost-effective and lightweight design
Improved Durability and Performance
- Reduced ball diameter and optimized ball-race contact force distribution for enhanced durability
- Use of spiral/tilted tracks in inner/outer races for smoother operation under high loads
- The thicker cage ends near the joint opening for higher operating angles
- Larger ball sizes for increased torque capacity
- Irregular circumferential groove pitches for better joint assembly
Compact and Lightweight Designs
- Compact CV joint allowing high joint angles without increasing outer ring size/weight
- Lightweight direct pinion mount designs eliminating auxiliary components
- Cage offset angle, ball/groove diameter ratios optimized for compactness and strength
Emerging Manufacturing Techniques
- Injection clinching joining for hybrid polymer-metal staked joints in multi-material structures
- Vacuum-tight threaded junctions for reliable heterogeneous material joints
- Electromagnetic activation of magneto-sensitive adhesives for optimized bonding
Technical Challenges
| Novel CV Joint Designs | Developing innovative constant velocity (CV) joint designs that increase the maximum joint angle, reduce contact pressure, and integrate gear components for cost-effective and lightweight construction. |
| Improved Durability and Performance | Enhancing the durability and performance of CV joints through optimised ball-race contact force distribution, spiral/tilted track grooves, thicker cage ends, larger ball sizes, and irregular groove pitches for smoother operation under high loads. |
| Autonomous Navigation and Positioning | Developing high-precision autonomous navigation and positioning technologies to enable agricultural robots to accurately navigate to the operation area and track the operation route. |
| Multifunctional Agricultural Robot Integration | Integrating multiple agricultural operations (such as tillage, sowing, fertilisation, spraying, harvesting, etc.) into a single automated robotic system to achieve efficient integrated operations. |
| Real-time and Response Speed | Reducing latency to enhance user experience in virtual reality applications. |
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