# Patent Analysis and Structural Synthesis of Epicyclic Gear Trains Used in Automatic Transmissions
## 5 Method to Obtain New Configuration of EGTs
### Basic Graphs from Existing Products and Patents  
Basic graphs can be obtained from existing products and patents through the transformation method. In this way, the probability of obtaining novel configurations similar in structure and performance to existing ones is increased. A lot of preparatory work is needed. The EGTs used in existing AT products and AT patents need to be investigated and be stored in an AT database as completely as possible. These EGTs are not only applied to obtain basic graphs for the synthesis process, but also to detect whether the EGTs obtained by synthesis process have been used before. After the preparatory work, the process of synthesizing new EGTs can be conducted.  
(1) Determine the task object. For example, novel six-link one-DOF EGTs with one main shaft are expected to be obtained. There should be one multiple joint, five revolute pairs and four gear pairs according to structural characteristics (5) and (7).  
(2) Choose a basic graph of EGTs used in existing AT products or patents based on the task object. The DBGs for the expected EGTs should contain seven vertices, six solid lines and four dash lines, DOF of which is two according to equation (5). The DBGs shown in Table 2 meet the conditions. Take the EGT used in the Ravigneaux planetary mechanism as an example and the corresponding basic graph is obtained as shown in Figure 8.  
(3) Choose the solid lines that are not incident with hollow vertices. According to the structural characteristic (11), there are 6 solid lines that are incident with the hollow vertex, which means that they can be transformed into dash lines.  
(4) Obtain DBGs by transforming solid lines into dash lines. Four of the 6 solid lines should be transformed into dash lines. Then, there should be 15 (i.e., \(C_{6}^{4}\)) DBGs as shown in Figure 9.  
Figure 8: The basic graph of EGT used in the Ravigneaux planetary mechanism.  
(5) Eliminate the DBGs violating the structural characteristics. DBGs (1), (11), (13) and (15) violate the structural characteristic (8), because vertices representing planet gears are incident with dash lines only. On the other hand, DBGs (4), (5), (10), (12) and (14) violate the structural characteristic (9), because the vertices representing planet gears are adjacent with each other by solid lines. Therefore, they should be excluded.  
(6) Detect the isomorphism of DBGs. DBGs (6) and (8) are isomorphic with each other, so are DBGs (7) and (9). So, DBGs (6) and (7) are retained only. The retained DBGs are shown in Table 15.  
(7) Detect whether the retained DBGs have been used in the existing AT products or patents. If not, the DBGs are novel and can be used for innovation of ATs.  
The second obtained DBG in Table 15 is the Ravigneaux planetary mechanism, and it is also found in the AT patent registered by Aisin and Toyota companies [78]. In this patent, the AT consists of the Ravigneaux planetary mechanism, a planetary row with double planet gears, 4 clutches, 2 brakes and 1 one-way clutch (OWC). Through the separation and combination of clutches and brakes, it can achieve 8 forward gears and 2 reverse gears. It should be indicated that the patented AT has been applied in LS460 vehicles, named AA80E. The other three DBGs are not found in the AT database established in the patent survey. They are new configurations and new AT products may be obtained by adding several clutches and installing some gear rows. It is found that the third obtained DBG contains a loop  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**DBG** & **Functional Diagram** & **DBG** & **Functional Diagram** \\ \hline
**6** & **3** & **4** & **5** \\
**7** & **6** & **4** & **5** \\ \hline \hline \end{tabular}
\end{table}
Table 15: DBGs obtained from the basic graph and the corresponding functional diagram.  
Figure 9: The 2-DOF DBGs obtained from the basic graph shown in Figure 8.  
formed by dash lines only. According to structural characteristic (10), it also can be used for ATs in some specific situations.