Reverse rotation preventing mechanism for diesel engine
The invention prevents reverse rotation of a diesel engine which is possible to occur when the engine is started. A camshaft 13 is driven by a crankshaft 5 through power transmission means, and cams 14, 21 and 22 are provided on camshaft 13 so as to drive a fuel injection pump 12 , an intake valve and an exhaust valve, respectively. In fuel injection pump cam 14 , middle stage portion 53 is radially larger than minimum radius portion 51 and is disposed at a predetermined angle R 3 on the back side in the rotation direction of the fuel injection pump cam from maximum radius portion 52.
1. A reverse rotation preventing mechanism for a diesel engine comprising:
a camshaft driven by a crankshaft through power transmission means;
an intake cam provided on the camshaft so as to drive an intake valve;
an exhaust cam provided on the camshaft so as to drive an exhaust valve; and
a single fuel injection pump cam provided on the camshaft so as to drive a fuel injection pump, wherein the single fuel injection pump cam is shaped so as to include a rotatably integral maximum radius portion, minimum radius portion, and middle stage portion, and wherein the middle stage portion is radially larger than the minimum radius portion and is disposed in a predetermined angle range on the back side in the rotation direction of the single fuel injection pump cam from the maximum radius portion.
2. The reverse rotation preventing mechanism for a diesel engine according to claim 1 , wherein the height of the middle stage portion substantially corresponds to a lifted position of a plunger of the fuel injection pump when injection of the fuel injection pump driven by the cam is completed at the engine start.
3. The reverse rotation preventing mechanism for a diesel engine according to claim 1 , wherein the height of the middle stage portion is determined so that the middle stage portion is prevented from interfering with a rotation locus of an end of a connecting rod.
4. The reverse rotation preventing mechanism for a diesel engine according to claim 1 , wherein a boundary position between the middle stage portion and a radius-reduced portion where the radius is reduced to the minimum radius portion is disposed adjacent to a position for starting the opening process of the intake valve.
5. The reverse rotation preventing mechanism for a diesel engine according to claim 1 , wherein a boundary position between a portion where the radius is gradually reduced from the maximum radius portion and the middle stage portion is disposed adjacent to a position for starting the opening process of the exhaust valve.
6. The reverse rotation preventing mechanism for a diesel engine according to claim 1 , wherein the single fuel injection pump cam includes a single maximum radius portion.
7. The reverse rotation preventing mechanism for a diesel engine according to claim 1 , wherein the predetermined angle range corresponds to a profile of the exhaust cam for an opening period of the exhaust valve from its opening until its closing.