Synchromesh automatic transmission

1. A synchromesh automatic transmission comprising:

a plurality of shift forks for changing a shift stage;

a plurality of shift lugs which are provided to drive said each shift fork and are aligned in a row;

a shift finger which is engaged with one of said plurality of shift lugs and displaces a corresponding shift fork to a shift position; and

a selector shaft which is elongated along the row of the shift lugs, supports the shift finger so as to be displaced in a selection direction and enables the shift finger to be selectively engaged with one of said plurality of shift lugs,

wherein the synchromesh automatic transmission further comprises:

a lug lock portion which is engaged with the shift lug separately from the shift finger and enables the shift fork to be controlled so as to be located at a neutral position;

a shift selector mechanism which achieves a target shift stage by engaging the shift finger with the shift lug of the shift fork corresponding to the target shift stage and displacing this shift fork in a shift direction; and

an interlock mechanism which controls a shift fork that is different from the target shift stage so as to be located at a neutral position by displacing the lug lock portion following movement of the shift finger in a selection direction and engaging this lug lock portion with the shift lug of the shift fork that is different from the target shift stage.

2. The synchromesh automatic transmission according to claim 1 ,

wherein the lug lock portion is arranged on an interlock shaft that is elongated substantially in parallel with the selector shaft.

3. The synchromesh automatic transmission according to claim 1 ,

wherein the interlock mechanism engages the lug lock portion with the shift lugs of all shift forks other than the target shift stage.

4. The synchromesh automatic transmission according to claim 1 , further comprising:

a twin clutch transmission mechanism having driving gears of respective shift stages arranged on a plurality of input shafts that enable to selectively input power from an engine while dividing the shift stages into predetermined shift stage groups,

wherein the interlock mechanism allows the lug lock portion to be engaged with a shift lug of a shift fork that belongs to the same group as the target shift stage but is different from the target shift stage.

5. The synchromesh automatic transmission according to claim 4 , further comprising:

a twin clutch transmission mechanism having driving gears of respective shift stages arranged on a plurality of input shafts that enable to selectively input power from an engine while dividing the shift stages into predetermined shift stage groups,

wherein the interlock mechanism allows the lug lock portion to be engaged with the shift lugs of all shift forks that belong to the same group as the target shift stage and are other than the target shift stage.

6. The synchromesh automatic transmission according to claim 1 ,

wherein the shift lugs have lug members having groove portions and these lug members are aligned in series with their groove portions facing each other, and

the lug lock portion includes a tabular piece body which stops within the groove portion of the shift lug of the shift fork that is different from the target shift stage when the shift finger is arranged on the shift lug of the target shift stage and a taper face which is formed on end faces on the opposite sides in the selection direction of this piece body and returns the shift lug to the neutral position when the shift lug is made in a shift state.

7. The synchromesh automatic transmission according to claim 4 ,

wherein the shift lugs have lug members having groove portions and these lug members are aligned in series with their groove portions facing each other, and

the lug lock portion includes a tabular piece body which stops within the groove portion of the shift lug of the shift fork that is different from the target shift stage when the shift finger is arranged on the shift lug of the target shift stage and a taper face which is formed on end faces on the opposite sides in the selection direction of this piece body and returns the shift lug to the neutral position when the shift lug is made in a shift state.

8. The synchromesh automatic transmission according to claim 1 ,

wherein the shift lugs have lug members having groove portions and these lug members are aligned in series with their groove portions facing each other, and

the lug lock portion includes a piece body which stops within the groove portion of the shift lug of the shift fork that is different from the target shift stage when the shift finger is arranged on the shift lug of the target shift stage and a conically-shaped face which is formed on end faces on the opposite sides in the selection direction of this piece body and returns the shift lug to the neutral position when the shift lug is made in a shift state.

9. The synchromesh automatic transmission according to claim 4 ,

wherein the shift lugs have lug members having groove portions and these lug members are aligned in series with their groove portions facing each other, and

the lug lock portion includes a piece body which stops within the groove portion of the shift lug of the shift fork that is different from the target shift stage when the shift finger is arranged on the shift lug of the target shift stage and a conically-shaped face which is formed on end faces on the opposite sides in the selection direction of this piece body and returns the shift lug to the neutral position when the shift lug is made in a shift state.