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Energy efficiency has now gone beyond an environmental concern and has become a necessity for competitiveness. From the automobile industry to industrial machines and electronic devices, the performance of the entire system depends on the energy consumption and loss of each element, even down to mechanical systems. When properly designed, helical torsion springs can minimize energy loss by reducing friction, hysteresis, and parasitic load. Here are the four main ways in which helical torsion springs are engineered for energy loss reduction in mechanical systems.
1. Direct Torque Transfer Without Friction Losses
Most mechanical systems, whether used to translate linear motion to rotation via a cam, linkage or gears, involve many transitions. Each of these transitions involves a friction loss; even an efficient mechanical system will still lose about 3-5% of its energy with each interface. If there are multiple components in an assembly, the total energy loss could be 20-30%.
Helical torsion springs transfer the rotational energy through the spring body and directly to its arms, with no intermediate components. If one leg is anchored to a frame and the other is attached to a rotating member, the spring simply takes advantage of the elastic property of the wire to store and return the energy. There is no slipping, no gears and no linkage involved. In other words, there is no energy loss from friction. If the application of interest requires energy saving components like electric actuators for vehicles, solar powered actuators and similar, each link has to be as efficient as possible and direct torque path offered by helical torsion springs are indeed one of the best methods available for providing rotational return force.
2. Optimized Coil Geometry Reduces Internal Friction
Mechanical systems don't just lose energy through friction with neighboring components; the spring itself can also generate internal friction. Each of the spring's coils can slip and rub against the other. This converts stored mechanical energy into heat. This reduces the amount of energy that can be stored and returned by the spring when its load is removed.
At Hongsheng Spring, we engineer helical torsion springs with a pitch and clearance that prevent coils from rubbing each other during the springs operation. If large rotational displacement are involved (over 180 degrees), an optimized or stepped pitch may be used to maintain clearance throughout the windup. In well-designed helical torsion springs energy return efficiencies of 85-92% are achievable compared to the 60-70% that may be observed with springs where the coils come into contact.
3. Precision Material Selection for Constant Elasticity
There is also loss of energy from hysteresis in the spring itself; the difference between the loading and unloading characteristics results in a residual energy return that, like friction, leads to a loss of energy. Different spring materials behave differently and so yield different levels of hysteresis.
In helical torsion springs, choice of spring wire material significantly effects the energy return. Music wire offers high fatigue properties but moderate hysteresis. Stainless steel is a cheaper option that does not have high enough corrosion resistance but has moderate levels of hysteresis. If a truly low-loss spring is required for a high-precision application like a measuring device or a satellite actuator, the best materials are likely chrome silicon or chrome vanadium alloys. The hysteresis loss will be negligible (less than 5%) if a material such as these is specified and correctly heat treated. Stress relief heat treating the spring removes stresses and therefore the tendency of the material to "deform" slightly, decreasing hysteresis and improving efficiency.
4. Reduced Mass and Parasitic Loads
A final source of energy loss in mechanical systems is that of kinetic energy-a heavier system will require more force (and hence energy) to achieve the same levels of angular displacement, or it will move with more momentum than necessary. If the weight of the spring is increased substantially above what is strictly required by the system then this adds another layer to energy loss due to unwanted momentum.
Helical torsion springs can be made extremely efficient by having a minimal diameter for their power output and compact form. At Hongsheng Spring we use FEA analysis to determine the most efficient diameter wire and coil number required for each system, minimizing unnecessary mass. For the lightweight energy sensitive applications such as an electric actuator for a car door handle or the spring used to operate an electric vehicle charging port, weight is critical, and minimizing the mass will yield significant power savings and improve the life of your batteries. For systems that operate continuously or over millions of cycles, saving just a few watts by utilizing the light mass of the helical torsion spring will be worth many kilowatt hours saved over the life of the product.
Summary
Hongsheng Spring designs helical torsion springs in an optimized manner to reduce energy loss. This is done in four primary ways: direct torque transfer eliminates friction between the spring and the system, by providing a simple linkage with no gears; coil geometry is optimized to prevent inner-coil friction; carefully selected materials that reduce hysteresis; and lightweight springs with optimized form reduce unwanted kinetic energy losses. Hongsheng Spring products include helical torsion springs for automotive systems, electric vehicles, industrial machines and precision instruments, and we welcome inquiries to discuss these energy efficient springs and how they can benefit your application.