Secondary air introduction device

1. A secondary air introduction device configured to supply air into an exhaust passage of an engine to combust unburned gas contained in exhaust gas, the secondary air introduction device comprising:

an air introduction passage configured to introduce air into the exhaust passage;

a secondary air valve configured to be attached to a cylinder head of the engine and to control opening and closing of the air introduction passage; and

a bracket configured to attach the secondary air valve to the cylinder head, wherein

the secondary air valve is configured to be attached to an outer lateral surface of the cylinder head on one side in an axial direction of a crankshaft,

the secondary air valve includes an air introduction inlet formed in a position opposite to the outer lateral surface of the cylinder head in the axial direction of the crankshaft,

the secondary air valve includes an air inlet part which is disposed in a position opposite to the outer lateral surface of the cylinder head in the axial direction of the crankshaft,

the bracket includes a support part configured to support a pipe constituting an upstream part of the air introduction passage, the upstream part being located upstream of the secondary air valve,

a grip member is attached to the support part of the bracket, and

the upstream part includes: a downstream end coupled to the air inlet part of the secondary air valve and an intermediate part which is supported to the support part of the bracket with use of the grip member.

2. The secondary air introduction device as claimed in claim 1 , wherein

the secondary air valve includes an elastic valve body having a plate shape, and

the secondary air valve is arranged such that a thickness direction of the valve body corresponds to the axial direction of the crankshaft.

3. The secondary air introduction device as claimed in claim 1 , wherein the secondary air valve is disposed on one side in the axial direction of the crankshaft with respect to a power transmission member configured to transmit power to a valve mechanism of the engine, and an exhaust port of the engine is provided on the other side with respect to the power transmission member.

4. The secondary air introduction device as claimed in claim 1 , wherein an exhaust pipe of the engine extends on the other side of the cylinder head in the axial direction of the crankshaft.

5. The secondary air introduction device as claimed in claim 1 , wherein the secondary air valve is configured to be attached to the cylinder head through a plug member configured to close a passage defined inside the cylinder head.

6. The secondary air introduction device as claimed in claim 1 , wherein a pipe constituting a downstream part of the air introduction passage and connecting the secondary air valve with the exhaust passage is made of a metal material.

7. The secondary air introduction device as claimed in claim 1 , wherein a pipe constituting a downstream part of the air introduction passage and connecting the secondary air valve with the exhaust passage extends in the axial direction of the crankshaft in an area lower than a top part of a cylinder head cover.

8. The secondary air introduction device as claimed in claim 1 , wherein the grip member is detachably attached to a through-hole defined in the support part.