Core tip: the adjustment of the valve clearance of the Cummins B&C series engine: in normal use, in order to determine whether the valve clearance is normal, the thickness gauge can be inserted in the valve gap (for example, when the value is 0.30mm, 0.35mm). At this time, the gauge should not be inserted; then the thickness of the number one is used. Rules should be inserted into the valve clearance smoothly.
There is a certain valve clearance between the rear end of the valve rod of the B&C series engine of Cummins and its transmission parts to prevent the engine from working normally because of heat expansion and contraction. If the valve gap is too large in the work, the exhaust will not be smooth, which not only affects the engine's dynamic performance but also increases the noise (valve abnormal noise). If the valve clearance is too small, the valve will be shut down, the engine can not work normally, and it may cause the erosion and damage of the working face of the air distribution mechanism. Taking Cummins 6CTA8.3-C engine as an example, the adjustment method of valve clearance is described as follows.
Examination of 1. valve clearance
When the 6CTA8.3-C type engine is cold, the intake valve clearance should be 0.30mm and the exhaust valve clearance should be 0.61mm.
According to the regulations, the engine's valve clearance must be checked and adjusted after reaching 1 3800km or 1000h. In normal use, in order to determine whether the valve clearance is normal, the thickness gauge can be inserted in the valve gap with a specified value of one number (for example, when the value is 0.30mm, 0.35mm). At this time, the gauge should not be inserted; then the thickness gauge of one number should be inserted into the valve clearance smoothly. If the above requirements are met, the valve clearance is normal. Otherwise, the valve clearance must be adjusted if the valve clearance does not meet the requirements.
Before checking valve clearance, first, remove the engine parts that affect the valve cover plate (such as high pressure pipe, exhaust pipe, crankcase ventilation pipe, AFC tube, etc.), then remove the fixed screw of the valve cover and carefully take off the valve cover.
2. valve clearance adjustment
To facilitate the adjustment of the valve clearance, the Cummins engine has a timing pin 2 (see Figure 1, which is under the injection pump), and at the same time there is a small hole on the engine camshaft gear, called the timing alignment hole of the camshaft gear; when the crankshaft is slowly rotated, the timing pin is aligned with the timing alignment hole, and the timing pin is pressed down. It is possible to enter the hole in this state. At this point, the first cylinder is located at the top stop point of the compression stroke.
When adjusting the valve clearance, the first cylinder should be at the top stop point of the compression stroke. The specific methods of operation are as follows:
The wheel gear (special tool, which can also be replaced by the connecting gear of the starting motor to the flywheel), is inserted into the flywheel shell to connect the flywheel gear; the wheel gear is slowly rotated by the hand to hold the engine timing pin, and when the timing pin enters the positive alignment hole on the camshaft gear, the I cylinder is at the stop point on the compression stroke. Set (see Figure 2). At this time, the inlet and exhaust doors of the I cylinder are closed, that is, the clearance of the valve can be adjusted, while the VI cylinder inlet and the exhaust valve are in the open state, and the valve can not be adjusted. According to the working principle of the valve train, the opening and closing sequence of intake and exhaust valves of each cylinder has certain rules. Therefore, according to the working order of the cylinder and the opening and closing of the inlet and exhaust valves of each cylinder, the valve clearance of the half number of valves can be checked and adjusted when the cylinder is located at the stop point on the compression stroke. Then, the crankshaft is rotated for one week, and the VI cylinder is located at the stop point of the compression stroke, and the valve clearance of the remaining valve can be adjusted.
When adjusting, first release the screw fixed nut to adjust the valve, insert the thickness gauge into the end of the valve rod and the valve rocker arm. One hand is screwed with the screwdriver to adjust the screw, and the one hand pulls the gauge slightly. When the thickness of the gauge is slightly resisted, the table clearance has been adjusted correctly. At this time, the thick gauge is inserted into the center of the valve clearance, so that the adjusting screw remains unchanged, and the fastening nut is tightened to lock the adjusting screw. After locking the screws, the gauge should be re measured with the thick gauge, because the adjusting screws may be unintentionally rotated when the nut is locked, so that the valve clearance is changed. If the valve clearance changes, it should be readjusted until it is correct.
After adjusting the valve clearance, cylinder head cover and other components should be installed, and the engine should be started for inspection. If the valve has abnormal sound, the valve clearance should be checked and adjusted again.
3. precautions for valve adjustment
The engine timing pin is mainly used to adjust the stop point on the compression stroke of the cylinder. After adjusting the stop point on the compression stroke of the I cylinder, the timing must be pulled out to ensure that the timing pin is removed from the camshaft gear so as to avoid damage to the timing pin.
(2) before adjusting the gap between the valves, the maintenance manual should be consulted first to find out the required value of the valve clearance to be adjusted to the engine. At the same time, it should be noted that the clearance value given is the state value of the heat engine when the cooler is returned to ensure that the adjustment is correct.
There is a certain valve clearance between the rear end of the valve rod of the B&C series engine of Cummins and its transmission parts to prevent the engine from working normally because of heat expansion and contraction. If the valve gap is too large in the work, the exhaust will not be smooth, which not only affects the engine's dynamic performance but also increases the noise (valve abnormal noise). If the valve clearance is too small, the valve will be shut down, the engine can not work normally, and it may cause the erosion and damage of the working face of the air distribution mechanism. Taking Cummins 6CTA8.3-C engine as an example, the adjustment method of valve clearance is described as follows.
Examination of 1. valve clearance
When the 6CTA8.3-C type engine is cold, the intake valve clearance should be 0.30mm and the exhaust valve clearance should be 0.61mm.
According to the regulations, the engine's valve clearance must be checked and adjusted after reaching 1 3800km or 1000h. In normal use, in order to determine whether the valve clearance is normal, the thickness gauge can be inserted in the valve gap with a specified value of one number (for example, when the value is 0.30mm, 0.35mm). At this time, the gauge should not be inserted; then the thickness gauge of one number should be inserted into the valve clearance smoothly. If the above requirements are met, the valve clearance is normal. Otherwise, the valve clearance must be adjusted if the valve clearance does not meet the requirements.
Before checking valve clearance, first, remove the engine parts that affect the valve cover plate (such as high pressure pipe, exhaust pipe, crankcase ventilation pipe, AFC tube, etc.), then remove the fixed screw of the valve cover and carefully take off the valve cover.
2. valve clearance adjustment
To facilitate the adjustment of the valve clearance, the Cummins engine has a timing pin 2 (see Figure 1, which is under the injection pump), and at the same time there is a small hole on the engine camshaft gear, called the timing alignment hole of the camshaft gear; when the crankshaft is slowly rotated, the timing pin is aligned with the timing alignment hole, and the timing pin is pressed down. It is possible to enter the hole in this state. At this point, the first cylinder is located at the top stop point of the compression stroke.
When adjusting the valve clearance, the first cylinder should be at the top stop point of the compression stroke. The specific methods of operation are as follows:
The wheel gear (special tool, which can also be replaced by the connecting gear of the starting motor to the flywheel), is inserted into the flywheel shell to connect the flywheel gear; the wheel gear is slowly rotated by the hand to hold the engine timing pin, and when the timing pin enters the positive alignment hole on the camshaft gear, the I cylinder is at the stop point on the compression stroke. Set (see Figure 2). At this time, the inlet and exhaust doors of the I cylinder are closed, that is, the clearance of the valve can be adjusted, while the VI cylinder inlet and the exhaust valve are in the open state, and the valve can not be adjusted. According to the working principle of the valve train, the opening and closing sequence of intake and exhaust valves of each cylinder has certain rules. Therefore, according to the working order of the cylinder and the opening and closing of the inlet and exhaust valves of each cylinder, the valve clearance of the half number of valves can be checked and adjusted when the cylinder is located at the stop point on the compression stroke. Then, the crankshaft is rotated for one week, and the VI cylinder is located at the stop point of the compression stroke, and the valve clearance of the remaining valve can be adjusted.
When adjusting, first release the screw fixed nut to adjust the valve, insert the thickness gauge into the end of the valve rod and the valve rocker arm. One hand is screwed with the screwdriver to adjust the screw, and the one hand pulls the gauge slightly. When the thickness of the gauge is slightly resisted, the table clearance has been adjusted correctly. At this time, the thick gauge is inserted into the center of the valve clearance, so that the adjusting screw remains unchanged, and the fastening nut is tightened to lock the adjusting screw. After locking the screws, the gauge should be re measured with the thick gauge, because the adjusting screws may be unintentionally rotated when the nut is locked, so that the valve clearance is changed. If the valve clearance changes, it should be readjusted until it is correct.
After adjusting the valve clearance, cylinder head cover and other components should be installed, and the engine should be started for inspection. If the valve has abnormal sound, the valve clearance should be checked and adjusted again.
3. precautions for valve adjustment
The engine timing pin is mainly used to adjust the stop point on the compression stroke of the cylinder. After adjusting the stop point on the compression stroke of the I cylinder, the timing must be pulled out to ensure that the timing pin is removed from the camshaft gear so as to avoid damage to the timing pin.
(2) before adjusting the gap between the valves, the maintenance manual should be consulted first to find out the required value of the valve clearance to be adjusted to the engine. At the same time, it should be noted that the clearance value given is the state value of the heat engine when the cooler is returned to ensure that the adjustment is correct.
