Abstract
Automotive engines in recent years have had to meet more rigorous customer
needs and societal demands for lower fuel consumption, cleaner emissions, smaller size,
lighter weight and quieter operation, among other things. Owing to improvements in
computer hardware and computer-aided engineering tools, vehicle manufacturers have
focused attention on optimization calculations as a means of meeting various requirements
involving trade-offs. This paper describes a shape optimization method [1] and a newly
developed parametric optimization method for optimizing the number and locations of bolts.
First, shape optimization was applied to a noise and vibration (NV) performance study in the
development process for powertrain parts, including a new engine and transmission. Though
NV study results depend largely on the skill, know-how, knowledge and experience of
engineers in this process, a shape optimization method makes it possible to reduce the
influence of these factors. In addition, it can shorten the design period and also satisfy other
performance requirements, in addition to powertrain NV performance. Shape optimization
methods can be broadly classified as non-parametric and parametric techniques. Because each
method has different features, these techniques are used selectively according to the design
phase and the characteristics and shapes of the target parts.
Second, when engineers study the number and locations of bolts from an NV point of view, a
trial-and-error approach is usually adopted in the early stage of design to achieve the NV
target (e.g., eigenvalue). With the aim of reducing inefficiency in this stage of the design
process, a method of optimizing the number and locations of bolts was newly developed. An
automatic analysis system was integrated with a finite element method (FEM) application, in
which the concept of Modal Assurance Criterion (MAC) was introduced as an automatic and
quantitative mode tracking method in the modal analysis. By applying this approach to the
development of powertrain NV performance, compatibility was achieved with the part
weights and other aspects that usually involve trade-offs.
Keywords - Optimization, powertrain, NV, clamping bolt, CAO