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Abstract : Vol.40No.3(2005.9)
Special Issue：Basic Analysis Towards Further Development
of Continuously Variable Transmissions
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Review
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| P.1 |
Basic
Analysis Towards Further Development of Continuously Variable
Transmissions (Overview) |
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Various types of transmissions,
representing a wide range of opinions, have been proposed
worldwide. The CVT (Continuously Variable Transmission),
which made its first appearance about 20 years ago as
an ideal transmission, has also required considerable
development in order to be ready for competitive dominance.
This paper discusses the role of the CVT in the automotive
power train, outlines areas requiring future technical
development, and provides an overview of the research
activity in our laboratories.
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Research Reports
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| P.6 |
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Ichiro Tarutani, Hirofumi Tani, Yuji
Nagasawa
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Although the analysis of the load distribution and
slip velocity in a Metal V-belt CVT is important for
the evaluation and improvement of its performance, it
is difficult to develop a simulation model for analyzing
power transmission by a CVT belt because of the belt's
complex structure.
In this paper, we report the development of a simulation
model that can predict fundamental characteristics of
a Metal V-belt CVT with useful accuracy within a reasonable
amount of calculation time. The model uses a combination
of load analysis based on equilibrium equations and
slip velocity analysis based on the evaluation of the
pulley displacement by FEA.
The major concerns in the calculation are the load
distributions in the belt, including ring tension, element
compression, and pulley clamping force, since these
are the most important performance indexes in the design
stage of a CVT. We confirmed the validity of the calculated
results by performing a basic experimental analysis
of the pulley clamping force.
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| P.14 |
Friction
Characteristics Analysis for Clamping Force Setup in Metal
V-belt Type CVTs |
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Hiroyuki Nishizawa, Hiroyuki Yamaguchi,
Hideyuki Suzuki
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Lowering the belt clamping force from the current setting
value is effective for increasing the transfer efficiency
in a metal V-belt type CVT (Continuously Variable Transmission).
However, setting the clamping force too low will cause
macro slip (large belt slip). Setting of the clamping
force to the proper level therefore requires a detailed
understanding of the friction characteristics between
the belt and the pulley (belt friction characteristics)
and requires that the macro slip threshold be clearly
defined. In this paper, we propose a friction expression
model for a metal V-belt type CVT and use this model
to clarify the state of power transmission in the vicinity
of the macro slip limit.
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| P.21 |
Measurement
and Estimation Technologies for the Experimental Analysis
of Metal V-belt Type CVTs |
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Hiroyuki Yamaguchi, Hirofumi Tani,
Kisaburo Hayakawa
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This
paper outlines measurement and estimation technologies
necessary for solving metal V-belt CVT issues. These technologies
examine the detailed behavior of the working belt. The
test apparatus consists of a low inertia dynamo with high
response that can reproduce the transitional characteristic
similar to engines. To analyze power transmission characteristics,
we construct a measurement technology that clarifies the
transitional characteristic and transmission performance
around the marginal torque of the belt. In addition, we
construct estimation technologies as a substitute for
the measurements of working belt behavior, which is difficult
to measure in an actual system. In this paper, we discuss
cases of a special experimental technology for metal V-belt
type CVTs.
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| P.30 |
Traction
Drive System and its Characteristics as Power Transmission |
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Shuzou Sanda, Kisaburo Hayakawa
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Improvement in efficiency and durability
is necessary for developing a traction drive continuously
variable transmission (t-CVT). The traction coefficient
at the power transmitting contacts of the t-CVT, which
is the dominant factor in efficiency and durability,
must be predicted with a high degree of accuracy and
must be controlled in the design of a compact and efficient
t-CVT. This report presents a new method of predicting
the traction coefficient with sufficient accuracy.
In the prediction, a rheological model
of the fluid film is simplified by separating a contact
ellipse into three characteristic regimes in which only
one of the elastic, plastic, or viscous effect is dominant
in each regime. This simplification makes it possible
to obtain shear stress more easily than is possible
with a direct numerical solution of a visco-elasto-plastic
equation. A technique has also been developed to presume
rheological properties from experimental traction curves
with spin motion included, which is a condition corresponding
to t-CVT contact.
With this method, the maximum traction
coefficient can be predicted within 10% accuracy, which
makes the optimum control of the normal force of the
power transmitting contact of a t-CVT possible.
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