Tolerance ring

Last updated

A tolerance ring is a radially sprung ring that is press fitted between two mating components to act as a frictional fastener. [1] They are flexible shims designed to fix two cylindrical parts together. [2] The wavelike protrusions that run around the circumference of the ring generate a retention force to provide an optimal fit between the two mating components without the need for adhesive or excessive assembly force, simplifying the process for manufacturers. [3] They allow for any misalignment caused by thermal expansion or excessive vibration. [1] Tolerance rings can be used as bearing mounts and as a means of dealing with torque transfer, torque overload protection and axial slip between mating components. [1] [4] They are often used to isolate undesirable vibration in engines and electric motors, for noise-free mechanism operation in passenger vehicles and domestic appliances, where noise reduction has become a major trend in recent years. [3] [4] Modifications to tolerance rings can be made to tune the dynamic stiffness and, therefore, the frequencies that can be isolated. [4]

Contents

Tolerance rings can be used to eliminate noise completely, simply by taking up clearance between mating components, which could otherwise lead to rattling in the system as the parts are not completely constrained. [3]

Automotive use

Tolerance rings are used in a number of mechanisms throughout the automotive powertrain and steering systems, as well as the car interior and exterior. [5] Their torque limiting and overload capabilities allow them to be used as simple clutch devices in several applications, such as the automatic tailgate motor [6] and the collapsible steering column. They are also used by automotive manufacturers to mount bearings in hinges and gears in the power train. [5]

Their lightweight properties have also made tolerance rings attractive to automotive manufacturers as they seek to enhance car performance [5] while complying with government requirements for reductions in carbon emissions. In the European Union, regulations on car emissions have been introduced by the European Commission, restricting the amount of carbon dioxide (CO2) emissions that a car can emit. [7] Since 2015, EU law requires that new cars do not emit more than 130 grams per kilometer of carbon dioxide (CO2). If that limit is breached then manufacturers can face fines. From 2021 the new mandatory emission target will be a fleet average of 95 grams per kilometer. [8] China is beginning to introduce legislation to create a National Standard, based on carbon emission reduction regulations already in effect in Europe. [9] [10] The U.S. Environmental Protection Agency (EPA) requires automotive companies to average carbon dioxide (CO2) tailpipe emissions at 101 grams per kilometer (163 grams/mile) by model year 2025. [11] [12] These regulations require car manufacturers to reduce the weight of their engines and vehicles to enhance fuel efficiency. [5] According to the EPA estimations, every 10 per cent drop in car mass decreases fuel use between 5 and 10 per cent. [13]

In most modern Electric Power Steering (EPS) systems, the motor housing is a part of the rack casting which is usually made from lightweight materials, such as aluminum alloys. [14] The stators are traditionally press fitted into the housing. Tolerance rings can be used instead of press fitting. With their wavelike protrusions, tolerance rings generate a retention force when compressed between the housing and the stator. These protrusions act as springs and allow the mating components to expand and contract at different rates while still providing the required retention force. [15] Tolerance rings also make sure that there is a constant thermal bridge between the stator and the housing, allowing heat to be dissipated away from the stator. Cooler operating temperatures result in higher efficiency and an extended life of the motor. [16]

Tolerance rings are used as an electric motor stator mount in electric power steering (EPS) to protect the system from torque overload in the event of back-driven shocks through the steering system. They do this by allowing the drive shaft to slip inside the gear so the gear teeth are not damaged, which strengthens the longevity of the EPS system. [6]

The collapsible steering column has been designed to protect the driver from injuries caused by striking the steering system in a crash. Consisting of two interlocking shafts, the collapsible steering column absorbs energy by collapsing inwards or breaking upon impact. [17] To secure the shaft and housing of the steering column in place during normal driving conditions, a tolerance ring is fitted between the two parts. The tolerance ring is designed to axially slip at a predetermined torque level, enabling the shaft to slide inside its housing in a crash, absorbing impact energy to protect the driver. [18]

According to the European Union Commission Directive 95/56/EC (1995), all vehicles are mandated to be fitted with anti-theft security devices. The regulation requires that a steering lock must be able to withstand forces of 100Nm applied to the steering wheel without failing. It also requires that cars exported to European markets be fitted with security devices. [19] The Chinese directive GB15740-2006 [20] obliges Chinese car producers to incorporate anti-theft mechanisms in their vehicles. [20] In a steering lock, a tolerance ring's wavelike protrusions maintain a retention force between the steering shaft and lock column. This allows the inner shaft to move freely within the housing when the steering lock is applied, while securing the two parts in place during normal car operation. [21]

In a tailgate motor, the tolerance ring protects the motor and gearing from excessive force, acting as a clutch. If the trunk is subjected to a force opposite to the motion (i.e. when someone is manually opening the trunk when it is automatically closing), the tolerance ring will allow the components to slip against each other, at certain torque levels. This protects the other components in the trunk mechanism. [6]

To ensure the armrest stays in place when it is stowed away by the passenger and does not fall down when the car travels over rough terrain, a tolerance ring is used at the pivot. Its wavelike protrusions generate sufficient torque to hold it in place and to allow for the correct adjustment feel. [6]

Tolerance rings are used in a number of mechanisms in domestic and industrial air conditioning (AC) systems. AC manufacturers use them as stator and bearing mounts.

Air conditioning

Tolerance rings are used to secure the stator within the frame. It acts as a cushion when the AC motor is in operation to absorb vibration for noise-free AC performance.

Tolerance rings are also used in the top frame structure of AC systems to secure the top of the rotor, replacing spot welding. They absorb vibration from the rotor and crankshaft in the AC motor when the compressor is running at high speed, ensuring the AC pump operates as efficiently as possible over its life cycle and reducing noise.

Computing

Tolerance rings are used in hard disk drives (HDD) to mount disks or bearing cartridges into the drives. The waves on their outer surface allow them to absorb excess vibration to reduce torque ripple effect and resonance to improve the HDD’s performance. The tolerance rings also ensure fast and easy assembly by eliminating the need for adhesive.

Related Research Articles

<span class="mw-page-title-main">Differential (mechanical device)</span> Type of simple planetary gear train

A differential is a gear train with three drive shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles, to allow the wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analog computers.

<span class="mw-page-title-main">Steering</span> System of components that allows vehicles to follow the desired course

Steering is a system of components, linkages, and other parts that allows a driver to control the direction of a vehicle.

Automotive engineering, along with aerospace engineering and naval architecture, is a branch of vehicle engineering, incorporating elements of mechanical, electrical, electronic, software, and safety engineering as applied to the design, manufacture and operation of motorcycles, automobiles, and trucks and their respective engineering subsystems. It also includes modification of vehicles. Manufacturing domain deals with the creation and assembling the whole parts of automobiles is also included in it. The automotive engineering field is research intensive and involves direct application of mathematical models and formulas. The study of automotive engineering is to design, develop, fabricate, and test vehicles or vehicle components from the concept stage to production stage. Production, development, and manufacturing are the three major functions in this field.

<span class="mw-page-title-main">Manual transmission</span> Motor vehicle manual gearbox; stick shift

A manual transmission (MT), also known as manual gearbox, standard transmission, or stick shift, is a multi-speed motor vehicle transmission system, where gear changes require the driver to manually select the gears by operating a gear stick and clutch.

<span class="mw-page-title-main">Front-engine, front-wheel-drive layout</span> Term used in automotive technology

In automotive design, a front-engine, front-wheel-drive (FWD) layout, or FF layout, places both the internal combustion engine and driven roadwheels at the front of the vehicle.

<span class="mw-page-title-main">Constant-velocity joint</span> Mechanisms for smoothly transmitting rotation through a bend in a drive shaft

A constant-velocity joint is a mechanical coupling which allows the shafts to rotate freely as the angle between the two shafts moves within a certain range.

<span class="mw-page-title-main">Drive shaft</span> Mechanical component for transmitting torque and rotation

A drive shaft, driveshaft, driving shaft, tailshaft, propeller shaft, or Cardan shaft is a component for transmitting mechanical power and torque and rotation, usually used to connect other components of a drivetrain that cannot be connected directly because of distance or the need to allow for relative movement between them.

Torsional vibration is angular vibration of an object—commonly a shaft along its axis of rotation. Torsional vibration is often a concern in power transmission systems using rotating shafts or couplings where it can cause failures if not controlled. A second effect of torsional vibrations applies to passenger cars. Torsional vibrations can lead to seat vibrations or noise at certain speeds. Both reduce the comfort.

<span class="mw-page-title-main">Drive by wire</span> Automotive technology

Drive by wire or DbW technology in the automotive industry is the use of electrical or electro-mechanical systems for performing vehicle functions traditionally achieved by mechanical linkages. Common examples include power steering, electronic throttle control and brake-by-wire. These technologies replace the traditional mechanical control systems with electronic control systems using electromechanical actuators and human–machine interfaces such as pedal and steering feel emulators. Components such as the steering column, intermediate shafts, pumps, hoses, belts, coolers and vacuum servos and master cylinders are eliminated from the vehicle. This is similar to the fly-by-wire systems used widely in the aviation industry. Safety standards for drive-by-wire are specified by the ISO 26262 standard level D.

Power steering is a system for reducing a driver's effort to turn a steering wheel of a motor vehicle, by using a power source to assist steering.

Torque steer is the unintended influence of engine torque on the steering, especially in front-wheel-drive vehicles. For example, during heavy acceleration, the steering may pull to one side, which may be disturbing to the driver. The effect is manifested either as a tugging sensation in the steering wheel, or a veering of the vehicle from the intended path. Torque steer is directly related to differences in the forces in the contact patches of the left and right drive wheels. The effect becomes more evident when high torques are applied to the drive wheels because of a high overall reduction ratio between the engine and wheels, high engine torque, or some combination of the two. Torque steer is distinct from steering kickback.

<span class="mw-page-title-main">Rover KV6 engine</span> Motor vehicle engine

The KV6 automotive petrol engine has a 24-valve quad-cam V6 configuration, and a pressurising variable-length intake manifold to add hot spots throughout the rev range. Variants exist in 2.0 to 2.5 litres capacities. These were built initially by Rover Group, then by Powertrain Ltd. KIA manufactured KV6 in Korea under licence. Production moved from the UK to China in 2005, re-designated NV6.

Hybrid vehicle drivetrains transmit power to the driving wheels for hybrid vehicles. A hybrid vehicle has multiple forms of motive power.

<span class="mw-page-title-main">Tire balance</span>

Tire balance, also called tire unbalance or tire imbalance, describes the distribution of mass within an automobile tire or the entire wheel on which it is mounted.

<span class="mw-page-title-main">Steering column</span>

The automotive steering column is a device intended primarily for connecting the steering wheel to the steering mechanism.

Hydraulic hybrid vehicles (HHVs) use a pressurized fluid power source, along with a conventional internal combustion engine (ICE), to achieve better fuel economy and reductions in harmful emissions. They capture and reuse 70–80% of the vehicle's braking/decelerating energy compared to 55% for electric hybrids. For trucks and buses, this can also be less expensive than electric systems, due to the price of batteries required for the latter. Hydraulic hybrid vehicle systems can also weigh less than electric systems, due to the high weight of the batteries. This can lead to a lower impact on payload capacity, especially for heavy vehicle classes.

<span class="mw-page-title-main">Nexteer Automotive</span>

Nexteer Automotive is a global motion control technology company. It is a publicly traded company owned about one-third by its shareholders and about two-thirds by Pacific Century Motors, which in turn is 51% owned by AVIC Automotive. Nexteer's global headquarters is in Auburn Hills, Michigan, United States.

<span class="mw-page-title-main">Drivetrain</span> Group of components that deliver power to the driving wheels

A drivetrain is the group of components that deliver mechanical power from the prime mover to the driven components. In automotive engineering, the drivetrain is the components of a motor vehicle that deliver power to the drive wheels. This excludes the engine or motor that generates the power. In marine applications, the drive shaft will drive a propeller, thruster, or waterjet rather than a drive axle, while the actual engine might be similar to an automotive engine. Other machinery, equipment and vehicles may also use a drivetrain to deliver power from the engine(s) to the driven components.

A composite bearing is a bearing made from a combination of materials such as a resin reinforced with fibre and this may also include friction reducing lubricants and ingredients.

This glossary of automotive terms is a list of definitions of terms and concepts related to automobiles, including their parts, operation, and manufacture, as well as automotive engineering, auto repair, and the automotive industry in general. For more specific terminology regarding the design and classification of various automobile styles, see Glossary of automotive design; for terms related to transportation by road, see Glossary of road transport terms; for competitive auto racing, see Glossary of motorsport terms.

References

  1. 1 2 3 "An Introduction to Tolerance Rings and Their Applications". www.machinebuilding.net. Retrieved 2017-02-11.
  2. ↑ "Tolerance Rings Do Double Duty as Shims or Slip Clutches". machinedesign.com. Retrieved 2017-02-11.
  3. 1 2 3 "Tolerance Rings Cut Vibrations in Fractional-Horsepower Motors". machinedesign.com. Retrieved 2017-02-11.
  4. 1 2 3 "Sssssh! Reducing noise and vibration in electric motors with tolerance rings". industrialproductspurchase.com. Retrieved 2017-02-11.
  5. 1 2 3 4 Robertson, Edward. "Emissions mission". Engine Technology International. Retrieved 2017-02-11.
  6. 1 2 3 4 "How optimising small parts gives big gains". Auto Car Professional. Retrieved 2017-02-11.
  7. ↑ "Road transport: Reducing CO2 emissions from vehicles - Climate Action - European Commission". Climate Action - European Commission. 2016-11-23. Retrieved 2017-02-11.
  8. ↑ "Reducing CO2 emissions from passenger cars - Climate Action". Climate Action - European Commission. 2016-11-23. Retrieved 2017-02-11.
  9. ↑ "China: Light-duty: Emissions". transportpolicy.net. Retrieved 2017-02-11.
  10. ↑ "China accelerates tougher vehicle emission standards, starting sooner". Green Car Reports. Retrieved 2017-02-21.
  11. ↑ "Vehicles and Engines" (PDF). www.epa.gov. Environmental Protection Agency. Retrieved 2017-02-11.
  12. ↑ "EPA and NHTSA Propose to Extend the National Program to Reduce Greenhouse Gases and Improve Fuel Economy for Cars and Trucks". National Service Center for Environmental Publications. Environmental Protection Agency. 2011.
  13. ↑ "SmartWay" (PDF). www.epa.gov. Environmental Protection Agency. Retrieved 2017-02-11.
  14. ↑ "Applications - Chassis & Suspension - Steering System" (PDF). The Aluminium Automotive Manual. 2011.
  15. ↑ "Tolerance Rings take the strain". The Engineer. Retrieved 2017-02-11.
  16. ↑ "motorsanddrives.com - Motor Temperature Ratings". Motors and Drives. The Cowern Papers. Retrieved 2017-02-11.
  17. ↑ "Why do we use collapsible steering columns? - Car Safety Systems". sites.google.com. Retrieved 2017-02-11.
  18. ↑ "Collapsible Steering Column Relies on Tolerance Rings". Machine Design. Retrieved 2017-02-21.
  19. ↑ "EUR-Lex - 31995L0056 - EN - EUR-Lex". eur-lex.europa.eu. Retrieved 2017-02-16.
  20. 1 2 "GB 15740-2006 English version, GB 15740-2006 Protective devices against unauthorized use of motor vehicles (English) - Code of China". www.codeofchina.com. Retrieved 2017-02-11.
  21. ↑ Morling, Rachael. "Steering the way to vehicle security with tolerance rings - Design Solutions". Connecting Industry. Retrieved 2017-02-11.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.