The function of the timing belt is to link up and down. The upper connection is the timing wheel of the engine cylinder head, and the lower connection is the crankshaft timing wheel; the timing wheel is connected to the camshaft. This camshaft has a cam and its contact point It is a small rocker arm. The rocker arm generates pressure through the power brought by the timing belt, and plays the role of jacking; the role of jacking up the intake valve is to let the atomized gasoline enter the cylinder, and the exhaust valve is to let Exhaust gas is discharged out of the cylinder block; when the camshaft is recessed (note: not a raised area) and contacts the small rocker arm at the same time, the intake and exhaust valves are closed at this time, the compression ratio is generated, the distributor is ignited, and internal combustion Start and generate motivation!
Taking a four-cylinder vehicle as an example, his ignition sequence is 4, 1, 2, 3, or 3, 4, 1, 2, or 2, 3, 4, 1; let’s start with one cylinder;
The intake valve and exhaust valve of one cylinder are closed to produce internal combustion;
At this time, the intake valve of the second cylinder almost closes immediately, and the exhaust valve is closed;
At this time, the intake valve of the three-cylinder is almost fully opened to suck in gasoline, and the exhaust valve is closed;
The four-cylinder completes the internal combustion at this time. The intake valve is closed and the exhaust valve is fully opened to exhaust!
The function of the timing belt is when the engine is running, the piston stroke (up and down movement) and the valve opening and closing (time) sequence of ignition (time). Under the action of the “timing” connection, it must be kept “synchronized” at all times. Running.
Regular replacement
The timing belt is a consumable product, and once the timing belt is broken, the camshaft will of course not run according to the timing. At this time, it is very likely that the valve and the piston will collide and cause serious damage. Therefore, the timing belt must be based on the original factory. The designated mileage or time is replaced.
During the working process of the automobile engine, the four processes of intake, compression, explosion, and exhaust occur continuously in the cylinder, and the timing of each step must be matched with the movement state and position of the piston, so that the intake and exhaust can be combined with each other. The piston lifts are coordinated with each other, and the timing belt acts as a "bridge" in the engine, and transmits power to the corresponding parts under the drive of the crankshaft. Many high-end cars use metal chains instead of belts to ensure the stability of the timing system. Since the breakage of the timing belt of the vehicle will cause damage to the internal valve of the engine, which is more harmful, the general manufacturer stipulates a replacement cycle for the timing belt.
Timing belts are rubber parts. As the engine working time increases, timing belts and timing belt accessories, such as timing belt tensioners, timing belt tensioners, and water pumps, will wear out or wear out. Therefore, for all engines equipped with timing belts, manufacturers will have strict requirements to replace the timing belts and accessories regularly within a specified period. The replacement period varies with the structure of the engine. Generally, when the vehicle is driven to 6 It should be replaced when it reaches 10,000 to 100,000 kilometers, and the specific replacement cycle should be based on the vehicle's maintenance manual.
Timing belts are generally considered for replacement at 80,000 kilometers. Even if you have a timing belt in your car, once it breaks, you cannot replace it yourself. Therefore, when the total travel distance reaches 80,000, it is recommended to consider replacing it. The timing belt is behind the radiator fan.
history
Timing belts first appeared in the 1960s and are used in most 4-cylinder cars, and are increasingly used in V6 engines. The timing belt was originally applied to the cam overhead engine, compared with the traditional timing chain, the timing belt.
Regular maintenance
Nowadays, as cars become more advanced, the workload of maintenance will gradually decrease. As a result, car owners often think that their vehicles basically do not need repairs. And each automobile manufacturer clearly stipulates the regular inspection and replacement cycle of the timing belt. As a professional maintenance technician, you should explain this to the car owner: as a content of regular maintenance and comprehensive inspection, the maintenance of the timing belt It should be added to the routine maintenance program. If you ignore this point, fail to check regularly and replace the faulty timing belt in time, it may lead to serious consequences.
The headlines are not the same as the drive belts of the attachments, they are easy to see and easy to check. The timing belt is often hidden behind a cover and can only be accessed according to the layout of the engine and engine compartment. However, in most cases, the cover on the timing belt, at least the upper half of the cover, can be removed or removed so that you can carefully inspect and replace the belt. During the inspection, if you do not see a well-maintained and properly tensioned belt, you should replace it in time.
rupture
When the timing belt ruptures, if the belt is bitten, the valve stops open and the engine stops running; if the engine is idling when it ruptures, it means that there is a gap between the piston at the top of the stroke and the open valve. In the two cases of rupture, only the timing belt itself is damaged. However, if the engine is designed with "interference fit", the piston and valve occupy the same space, and there is no gap between them, then other components will soon be damaged, such as the valve being bent and the piston being punched. These failures will cause customers to spend more, but also face the trouble of not being able to use the car for a long time. Therefore, customers should be made aware of the importance of regular inspections and timely replacement of timing belts. At the same time, users should also know that it is much cheaper to replace the timing belt during routine maintenance than to drag it into a repair shop for overhaul in the future.
Increased income, busy employees, and a deeper understanding of regular maintenance by customers will benefit you greatly. Some repair shops neglect the maintenance opportunities provided by the regular maintenance of timing belts. As the operator of a repair shop, you should remember: the vehicle is in your shop, and you have the opportunity to repair it and satisfy customers. This is a good opportunity for you to make money. However, if the belt is damaged while the vehicle is driving, the vehicle will be towed to other repair shops nearby. This means that you not only lose customers and the opportunity to repair the vehicle, but also lose the possibility of making money.
an examination
If the timing belt is not broken, it does not mean that it is ok. As the belt gets older and older, its stretch will inevitably exceed the range that the tensioning device can compensate, resulting in timing sprocket slippage. The wear of gear teeth and the adhesion of lubricating oil can also cause slippage. During the inspection, if the belt has reduced hardness, abrasion, fiber breakage, or cracks or cracks, it indicates that the belt has been damaged and cannot be used continuously. Next, check for sprocket failure. A damaged sprocket can "burn" the belt material and increase the wear of the belt teeth. The failure of the sprocket may also cause the valve mechanism to produce greater resistance to the timing belt.
Pros and cons
The transmission parts of the timing system are divided into two types: timing chain and timing belt. Many people are concerned about which type of transmission is better.
Timing belts have been used in engines for a long time. The technology is mature, the cost is low, and the noise is low, but it needs regular inspection and maintenance. Generally, it needs to be replaced for 50,000 to 100,000 kilometers. The timing chain has significant advantages such as compact structure, high transmission power, high reliability and wear resistance, and lifetime maintenance-free, but compared to traditional timing belts, its noise is generally slightly higher.
But nothing is absolute. With the advancement of technology, tooth-shaped mute chains are used in some cars, and the noise is even lower than that of timing belts. It is believed that the widespread use of this timing chain will bring more convenience to the majority of car users.
Toothed mute chain
Common timing chains are mainly divided into sleeve roller chains and toothed chains. Among them, the roller chain is affected by its innate structure, the rotation noise will be more obvious than the timing belt, and the transmission resistance and inertia will be correspondingly larger.
What we usually call the "silent chain" adopts a tooth-shaped structure design, which makes the teeth softer during transmission, has less impact, and runs more smoothly. In addition, there is no chain roller structure that produces noise, so it can perform at the noise level. The upper is better than the traditional timing belt.
