Eliminate the resonance noise of excavator parts

When the two CAT950B loaders started from the beginning after overhauling the connecting rod bushes of the engine, the engine oscillated severely. During one of them, the air filter and muffler were shaken off, and the damping block was cracked.

This model is equipped with a CAT3304 engine. Since it only has 4 cylinders, a double balance device is installed in order to balance the inertia force generated by the crank and connecting rod mechanism due to the large work interval. When installation is required, it is necessary to strictly ensure that all the marks on the timing gear and the balance crankshaft gear are aligned one by one. Only in this way can the inertial force of the engine be balanced. Ensure the smooth operation of the engine. According to the machine structure and repair process, the fault is caused by the imbalance of the inertia force of the crank connecting rod mechanism of the engine. That is, during maintenance, the oil pump was dismantled, and the timing gear chamber cover was not opened to remove the marks one by one (the marks cannot be seen) and then they were reinstalled. As a result, the dual balance shafts could not have a balancing effect, causing the engine oscillation.

The oil pump gear is the central gear between the crankshaft gear and the balance shaft gear. After opening the timing gear chamber cover, after aligning the marks on the timing gear and balance shaft gear and installing it, the problem was resolved when testing the machine. But if it is necessary to remove the timing gear cover and re-align the marks just to check the crankshaft bush or the oil pump, the workload is really too great. We have explored a simple method, which is introduced as follows:

(1) Find the tightening top dead center of cylinder I: pierce the timing bolt into the hole on the flywheel housing and press it toward the flywheel. Roll the crankshaft counterclockwise until the timing bolt pierces the hole on the flywheel and presses against the flywheel. Roll the crankshaft counterclockwise until the timing bolt pierces the hole in the flywheel to stop rolling. Remove the valve cover and check the two valves of cylinder I. If the piston of cylinder I is at the top dead center position of the contraction stroke, both valves should be closed. At this moment, the rocker arm can be moved up and down by hand. If the rocker arm cannot be moved, remove the timing bolt from the flywheel and roll the crankshaft 3600 counterclockwise. And install the timing bolt, which is the top dead center of the compression stroke of the I cylinder (if the timing bolt pierces the flywheel, remove the timing cover of the high-pressure fuel pump, and the timing pin can be pierced into the cam groove of the fuel injection pump. It can be determined that the I cylinder is at the top dead center of the contraction stroke at this moment).

(2) At the bottom of the engine crankcase, there is a bolt hole at each end of a large central tile. Roll the balance shaft by hand. When the concave part of the shaft is aligned with the bolt hole, screw in the bolt to resist the concave surface of the balance shaft. , So that the balance shaft cannot roll.

(3) After positioning the crankshaft and balance shaft, install the oil pump without alignment marks. Finally, remove the bolts that position the balance shaft.

After this installation, both engines work smoothly and the vibration is eliminated.