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Research Papers

Systematic Design of Six-Speed Automatic Transmissions With an Eight-Link Two-DOF Ravigneaux Gear Mechanism

[+] Author and Article Information
Cheng-Ho Hsu, Ruei-Hong Huang

Department of Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan 80424, Republic of China

J. Mech. Des 131(1), 011004 (Dec 11, 2008) (8 pages) doi:10.1115/1.3013346 History: Received March 29, 2008; Revised July 24, 2008; Published December 11, 2008

The purpose of this paper is to present an efficient methodology for the design of six-speed Ravigneaux-type automatic transmissions based on the concepts of basic gear ratios and speed ratio equations. First, the speed ratio equations of an eight-link two-degree-of-freedom Ravigneaux gear mechanism are derived, which are functions of basic gear ratios. Next, the ranges of the derived speed ratio equations are estimated and classified into three groups to synthesize all possible clutching sequences. Then, a planar-graph representation is proposed to arrange the desired clutches for each possible clutching sequence into the Ravigneaux gear mechanism. Finally, the number of teeth of all gears is synthesized from assigning three desired speed ratios by the analytic method presented by Hsu. The result of this paper shows that the eight-link two-degree-of-freedom Ravigneaux gear mechanism could reach six forward speeds at most, and only a particular set of speed ratios is practical for use.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Borg–Warner four-speed automatic transmission

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Figure 2

Ravigneaux gear mechanisms

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Figure 3

The included angle (α) of planet gears 6 and 7 shown in Fig. 2

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Figure 4

Borg–Warner four-speed automatic transmission and its graph

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Figure 5

Clutches C1, C2, C4, B2, B3, and B4 are arranged into the Ravigneaux gear mechanism in Fig. 2

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Figure 6

Clutches C1, C3, C4, B2, B3, and B4 are arranged into the Ravigneaux gear mechanism (Fig. 2)

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Figure 7

Clutches C1, C2, C3, C4, B2, B3, and B4 are arranged into the Ravigneaux gear mechanism (Fig. 2)

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Figure 8

(a) and (b) are the arrangements of diamond vertices C2, C3, and B1, in which B1 cannot be formed

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Figure 9

Three-view drawings of the solution space for the clutching sequence (R1,54, R1,52, R1,53, C1C4, R4,53, R4,52, R3,54)

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Figure 10

The configuration of the six-speed automatic transmission and the associated clutching sequence table.

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