Maintenance And Skills Of Engineering Machinery Engines

1. Measurement of cylinder liner wear

The general process of measuring engine cylinder liners is: select measuring tools according to the nominal size of the cylinder liner, that is, micrometer and cylinder gauge (including the plunger of the cylinder gauge); install and adjust the measuring tools, that is, first adjust the micrometer to the nominal size of the cylinder liner, then clamp the measuring rod and plunger of the cylinder gauge with the dial gauge installed between the anvil and measuring rod of the micrometer, adjust the extension length of the plunger of the cylinder gauge, and when the small needle of the dial gauge has a preload of about 1.5-2.0 grids, lock the plunger lock nut, and adjust the large dial of the dial gauge to zero;

Determine the measuring position and direction of the cylinder sleeve; measure and record and process the data, and finally propose repair ideas. With this method, when installing and adjusting the measuring tool, due to the small area of ​​the anvil and the end face of the measuring rod of the micrometer, the slightest carelessness or very slight interference and shaking will cause the plunger and the measuring rod of the cylinder gauge to come out of the anvil and the end face of the micrometer, causing the adjustment to fail and have to be readjusted. Therefore, the adjustment work is time-consuming and laborious, with extremely low efficiency, and the operator gives people a feeling of “unskilled business and clumsy movements”, which not only affects the progress and smoothness of the inspection, but also affects the operator’s professional image.

In view of this situation, the author believes that the operation can be improved as follows: when installing and adjusting the measuring tool, first adjust the dry micrometer to the nominal size of the cylinder sleeve, then directly insert the cylinder gauge with the dial indicator and the initial plug rod installed into the minimum wear of the measured cylinder sleeve, adjust the extension length of the cylinder gauge plug rod, so that the small needle of the dial indicator of the cylinder gauge has a pre-pressure of about 1.5-2.0 grids and lock the plug rod lock nut of the cylinder gauge, and finally insert the measuring rod and plug rod of the cylinder gauge between the anvil and measuring rod of the micrometer and adjust the large dial of the dial indicator to zero.

This adjustment method changes the adjustment of the cylinder gauge from being completely clamped on the micrometer to being partially clamped on the micrometer, while the other part of the adjustment is performed in the cylinder liner whose area is infinitely large relative to the anvil and the end surface area of ​​the micrometer, thereby effectively shortening the adjustment time of the cylinder gauge on the micrometer, avoiding the time-consuming and labor-intensive problems of the above-mentioned traditional adjustment methods, and significantly improving the anti-interference and operability of the gauge adjustment work.

2. Measurement of the clearance between the cylinder liner and the piston It is generally believed that there are at least three methods for measuring the clearance between the engine cylinder liner and the piston:

(1) The traditional method is to measure the inner diameter of the cylinder liner and the outer diameter of the piston skirt respectively, and the difference is the clearance between the engine cylinder liner and the piston.

(2) First, use a micrometer to measure the outer diameter of the piston skirt directly. Then, install the cylinder gauge with the dial indicator and the plunger installed between the anvil and the measuring rod of the micrometer. Adjust the extension length of the plunger of the cylinder gauge. When the small needle of the dial indicator has a preload of about 1.5-2 grids, tighten the plunger lock nut and adjust the large dial of the dial indicator to zero. Finally, extend the cylinder gauge into the cylinder sleeve. The value of the large needle of the dial indicator lower than “zero” (considering the reading of the small needle) is the matching clearance between the piston and the cylinder sleeve.

(3) First, use a micrometer to measure the outer diameter of the piston skirt and turn the micrometer stop screw to the locking position. Then, insert the cylinder gauge with the dial gauge and the plunger installed directly into the corresponding cylinder sleeve. Adjust the extension length of the plunger of the cylinder gauge so that the small needle of the dial gauge has a preload of about 1 grid and lock the plunger lock nut. At the same time, adjust the large dial of the dial gauge to zero. Finally, clamp the adjusted measuring rod and plunger of the cylinder gauge between the anvil and measuring rod of the micrometer. At this time, the value of the large needle of the dial gauge higher than “zero” (considering the reading of the small needle) is the matching clearance between the piston and the cylinder sleeve.

From the above measurement methods, it can be seen that the first and second methods also have the problem that the cylinder gauge is completely adjusted on the micrometer and the operability is very poor. The third measurement method is similar to the operation skills when measuring the cylinder sleeve, and is very worthy of being adopted by operators. Similarly, this operation technique can also be used to measure the clearance between the crankshaft journal and the crankshaft bearing.

3. On-machine treatment of broken cylinder head bolts

When on-machine treatment of broken cylinder head bolts, if you are not careful, the metal debris generated during the treatment process can easily fall into the cylinder or oil hole, causing extreme abrasive wear during subsequent use, thus seriously affecting the service life of the engine. To prevent this from happening, when removing the broken head bolts on the cylinder head, you can first use green shell paper or ordinary cardboard to make a shield in the style of the cylinder gasket. When making it, dip the cylinder gasket in a little waste oil and print it on the cardboard, then use a hollow gun that is suitable for the size of the cylinder head bolt to shoot out the hole on the cardboard (the rest of the positions such as the cylinder mouth position, water hole and oil hole position are not shot), and finally trim the edge of the cardboard with scissors. When in use, place the shield plate on top of the cylinder body, let the cylinder head bolts pass through the holes of the shield plate corresponding to each other, so that the shield plate is in contact with the upper surface of the cylinder body; then, remove the broken head bolts according to the general disassembly method; finally, use a brush to carefully clean the metal chips on the shield plate and then remove the shield plate.