Variable valve unit for vee shape engine

1. A variable valve unit for a V-type engine, comprising:

a camshaft attached to each of a pair of banks, and formed with a cam;

a rocker arm mechanism opening and closing at least one of an intake valve and an exhaust valve, and driven by the cam formed in the camshaft, and adapted to change a phase of the intake valve or the exhaust valve while displacing a position driven by the cam to a circumferential direction of the camshaft; and

an inversion mechanism inverting a rotating direction of a camshaft of one bank with respect to a rotating direction of a camshaft of the other bank, inversion mechanism being provided only at one end portion of the other bank.

2. A variable valve unit for a V-type engine according to claim 1 , wherein

said each bank is provided with a cylinder,

said one and the other bank are mutually offset, and thereby, arranged in a state of being shifted,

the inversion mechanism is provided in an offset space, which is formed at a bank end by offsetting the banks.

3. A variable valve unit for a V-type engine according to claim 2 , wherein

the rocker arm mechanism includes:

a rocker shaft attached to the banks, and arranged in parallel with the camshaft;

a first arm driving any one of the intake valve and the exhaust valve, and swingably supported by the rocker shaft;

a second arm swingable with the rocker shaft side as the fulcrum, and abutting against the cam to be driven via the cam;

a support shaft arranged in the vicinity of the rocker shaft;

a third arm swingably supported by the support shaft, receiving a displacement of the second arm, and further, varying the cam in accordance with a position change of the second arm generated by movement of the fulcrum of the second arm to drive the first arm; and

a variable mechanism displacing the fulcrum of the rocker shaft side of the second arm, and thereby, displacing a position of the second arm driven via the cam to a circumferential direction of the camshaft.

4. A variable valve unit for a V-type engine according to claim 1 , wherein the inversion mechanism is a planetary gear mechanism coaxially attached to the camshaft of said one bank.

5. A variable valve unit for a V-type engine according to claim 4 , wherein the planetary gear mechanism includes a ring gear that receives a rotation of a crankshaft, a sun gear connected the camshaft of said one bank, and a carrier fixed to a cylinder head.

6. A variable valve unit for a V-type engine, comprising:

a camshaft attached to each of a pair of banks, and formed with a cam;

a rocker arm mechanism opening and closing at least one of an intake valve and an exhaust valve, and driven by the cam formed in the camshaft, and adapted to change a phase of the intake valve or the exhaust valve while displacing a position driven by the cam to a circumferential direction of the camshaft; and

an inversion mechanism inverting a rotating direction of a camshaft of one bank with respect to a rotating direction of a camshaft of the other bank,

wherein

the rocker arm mechanism includes:

a rocker shaft attached to the banks, and arranged in parallel with the camshaft;

a first arm driving any one of the intake valve and the exhaust valve, and swingably supported by the rocker shaft;

a second arm swingable with the rocker shaft side as the fulcrum, and abutting against the cam to be driven via the cam;

a support shaft arranged in the vicinity of the rocker shaft;

a third arm swingably supported by the support shaft, receiving a displacement of the second arm, and further, varying a cam in accordance with a position change of the second arm generated by movement of the fulcrum of the second arm to drive the first arm; and

a variable mechanism displacing the fulcrum of the rocker shaft side of the second arm, and thereby, displacing a position of the second arm driven via the cam to a circumferential direction of the camshaft.

7. A variable valve unit for a V-type engine, comprising:

a camshaft attached to each of a pair of banks, and formed with a cam;

a rocker arm mechanism opening and closing at least one of an intake valve and an exhaust valve, and driven by the cam formed in the camshaft, and adapted to change a phase of the intake valve or the exhaust valve while displacing a position driven by the cam to a circumferential direction of the camshaft; and

an inversion mechanism inverting a rotating direction of a camshaft of one bank with respect to a rotating direction of a camshaft of the other bank,

wherein

the inversion mechanism is provided between a cam sprocket attached to the camshaft and a cam nearest to the cam sprocket.

8. A variable valve unit for a V-type engine comprising:

a camshaft attached to intake and exhaust sides of a pair of banks;

a rocker arm mechanism driven by the cam formed in the camshaft, and opening and closing at least one of an intake valve and an exhaust valve, and adapted to change a phase of the intake valve or the exhaust valve while displacing a position driven by the cam to a circumferential direction of the camshaft;

a first sprocket attached to a first camshaft of one bank;

a second sprocket attached to a second camshaft of said one bank;

a third sprocket attached to a third camshaft of an other bank;

a fourth camshaft mounted in said other bank;

a belt that directly transmits rotation of a crankshaft only to said first sprocket, said second sprocket, and said third sprocket; and

an inversion mechanism attached to the fourth camshaft and connected to the third sprocket, such that only the fourth camshaft rotates in a direction reverse to a rotating direction of the first camshaft, the second camshaft, and the third camshaft.

9. A variable valve unit for a V-type engine according to claim 8 , wherein the inversion mechanism includes a first gear attached to the third sprocket, and a second gear attached to the fourth camshaft and in direct engagement with the first gear.