What is the function of the cylinder head
The cylinder head is used to close the cylinder and form the combustion chamber. Side-valve engine cylinder head, cast with water jacket, water inlet hole, water outlet hole, spark plug hole, bolt hole, combustion chamber, etc. The overhead valve engine cylinder head, in addition to the cooling water jacket, also has valve gear, intake and exhaust passages, etc.
Main function: cylinder head In internal combustion engines, it is a valve mechanism, which is mainly used to close the upper part of the cylinder to form the combustion chamber. It also serves as a support for the camshaft, rocker arm shaft and intake and exhaust pipes. It is mainly used to suck air into the inside of the cylinder, and the spark plug mixes the combustible The gas is ignited, driving the piston to do work, and the exhaust gas is discharged from the exhaust pipe.
The structure of the cylinder head
The cylinder head is a box-shaped part with a complex structure. It is processed with intake and exhaust valve seat holes, valve guide holes, spark plug mounting holes (gasoline engines) or injector mounting holes. Also cast in the cylinder head are a water jacket, intake and exhaust passages, and a combustion chamber or part of the combustion chamber. If the camshaft is installed on the cylinder head, the cylinder head is also machined with cam bearing holes or cam bearing seats and their lubricating oil passages.
The cylinder head of a water-cooled engine has three structural forms: integral, segmented and single. In a multi-cylinder engine, if all cylinders share one cylinder head, the cylinder head is called an integral cylinder head; if there is one head for every two cylinders or one head for three cylinders, the cylinder head is a segmented cylinder head; if there is one head for every three cylinders, the cylinder head is called a segmented cylinder head; The cylinder head is a single cylinder head. Air-cooled engines have single-piece cylinder heads.
How to disassemble and assemble the cylinder head
1. Remove all pipelines and wiring connected to the cylinder head, and mark them if necessary to prevent confusion. .
2. After the engine cools down naturally, drain the coolant.
3. For engines with overhead camshafts, when disassembling the camshaft, loosen the camshaft fixing screws in the order of “from both sides to the middle” to prevent the camshaft from bending and deforming.
4. When disassembling the cylinder head bolts, you must wait until the engine is completely cooled before proceeding. When disassembling, follow the principle of “evenly loosening diagonally from both sides to the middle” to prevent the cylinder head from warping and deforming. .
5. Remove the old cylinder gasket and clean the sealing surface of the cylinder head and cylinder block. This work requires special patience and meticulousness. It is necessary to completely remove the old sealant, carbon deposits and corrosion products from the joint surface of the cylinder head and cylinder block, and blow them clean with compressed air.
Inspection of cylinder head
1. Inspection of surface roughness
The surface and surface roughness of the automobile parts to be inspectedPut the samples together under a magnifying glass of 5 to 10 times and observe them. Pay attention to judging and comparing the surface conditions of the two. If the texture and condition of the inspected surface are the same as those of the sample, then the inspected surface will be the same as the standard sample. have the same surface roughness grade.
2. Detection of cylinder head flatness
(1) Knife-shaped flat ruler method
Choose a length of 1000mm. The knife edge of a knife-shaped flat ruler with an accuracy of level 0 is placed along the direction of measurement, against the lower plane of the cylinder head being inspected (cylinder head is inverted). Use a thickness gauge to measure the edge of the knife edge along the direction of measurement, at intervals of 50 mm, against the surface being inspected. The gap between the lower plane of the cylinder head. The maximum value in the measurement data is the flatness error over the entire length of the cylinder head; the maximum value of the gap difference between two adjacent places is the flatness error of the cylinder head within the range of 50mm*50mm
(2) Flat magnetic table base method
Place three adjustable supports on the flat plate. Turn the cylinder head to be inspected upside down, and the three adjustable supports respectively support the upper plane of the cylinder head. A1, A2, and A3. Use a magnetic dial indicator to make the lower plane of the cylinder head at A1, A2, and A3 the same height as the flat plate plane, and adjust the pointer of the magnetic dial indicator to zero. Then adjust the magnetic dial indicator along a respectively. Record the height difference between the lower plane of the cylinder head and the zero position of the dial indicator every 50mm in the six directions of , b, c, d, e and f (note: when it is higher than zero, it is recorded as ” “, and when it is lower than zero, it is recorded as “―”).
When calculating the flatness error, the maximum value of the height difference between two adjacent points in the same direction is the flatness error within the range of 50mm*50mm; the high point and the low point in the same direction The value of the point height difference is the error of flatness over the entire length.
(3) Measurement by flatness tester
The flatness tester consists of an I-shaped ruler 2 and a percent Table 3, composed of meter base 4 and fastening bolts.
During inspection, keep the base of the meter base close to and slide along the upper plane of the I-shaped ruler, and the dial indicator rod moves on the surface to be measured. , the maximum value of the runout is the flatness error in the direction being measured. Transform the I-shaped ruler into different directions, and the maximum value of the measured flatness error is the flatness error of the entire plane.
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