How does the car measure and adjust the main fit clearance of the Copeland DJ piston?

1. Copeland DJ piston skirt size and cylinder clearance. The size of the piston skirt refers to the largest diameter of the main and secondary thrust surfaces of the piston skirt. The difference between the inner diameter of the cylinder and the size of the skirt is the cylinder matching clearance, which is an extremely important matching clearance for the engine. If there is a slight difference, it can be Failures such as pulling the cylinder occur. The skirt size is carefully measured with an inner micrometer according to the operating standards. When the position of the skirt size measurement is not clear, the micrometer can be used to measure point by point along the main and secondary thrust surfaces of the skirt from top to bottom, and the Z largest diameter value is the skirt. size. Common aluminum pistons are equipped with cast iron cylinder liners. The standard measurement room temperature is 20 °C. For every 10 °C rise (decrease), the matching cylinder clearance can be increased (decreased) by about 0.01 mm as appropriate.

2. Copeland DJ piston ring opening clearance must be checked with a caliper when the car is repairing and replacing the piston ring. For the worn cylinder, when checking the opening clearance, the ring should be placed near the bottom dead center with the smallest wear to prevent the opening teeth from being killed and pulling the cylinder. To check whether the opening clearance exceeds the practical limit value, the ring should be placed near the top dead center for measurement. Through the process of grinding the cylinder bore, check the opening clearance is not limited by position.

3. The side clearance and backlash of the Copeland DJ piston ring are measured with a caliper. If the side clearance is too small, it is easy to cause the snap ring and cylinder pull; if the side clearance is too large, it is easy to leak air and oil, and in severe cases, the piston ring and the ring bank will be broken. When replacing a new piston ring, it should be measured whether the side clearance is too small; if the piston ring is in use, it should be checked whether the side clearance exceeds the allowable operating limit, especially the first ring. The top dead center of the first ring of the cylinder is easy to wear into a step, if the step needs to be flattened, otherwise the side gap of the first ring will increase sharply. The piston ring will also pull the cylinder without backlash in the ring groove. Press the ring into the bottom of the ring groove, the outer surface of the ring should be lower than the outer surface of the ring land, otherwise the ring cannot be installed into the groove.