what is it for and signs of malfunction
An overrunning clutch, or as it is also called, an inertial generator pulley, is a small device thanks to which the service life of a good timing belt has been increased from 10-30 thousand kilometers to one hundred thousand. In today's article on Vodi.su, we will try to deal with the question of why the overrunning clutch of the generator is needed, what purpose it performs in the engine.
Purpose of the overrunning clutch of the generator
If you have ever seen a car generator, you have paid attention to its pulley - a round piece in the form of a metal or plastic cylinder, on which the timing belt is put on. A simple pulley is a one-piece piece that is simply screwed onto the generator rotor and rotates with it. Well, we recently wrote on Vodi.su about the timing belt, which transmits the rotation of the crankshaft to the generator and camshafts.
But in any mechanical working system there is such a thing as inertia. How is it shown? The belt slips when the rotation of the crankshaft stops or its mode changes, for example, when the speed is increased or decreased. In addition, the motor cannot run linearly and stably. Even if you are driving at a constant speed, the crankshaft makes two or four revolutions in all cylinders during a complete intake and exhaust cycle. That is, if we remove the operation of the engine and show it in a very slow mode, then we will see that it works as if in jerks.
If we add to this an increase in the number of various consumers of electricity, it becomes clear that we need a more powerful, and accordingly more massive generator, which will have even more inertia. Because of this, very strong loads fall on the timing belt, because, slipping on the pulley, it stretches. And since the belts are made of special reinforced rubber, which generally should not stretch, over time the belt simply breaks. And what its breakage leads to, we described on our Internet portal.
The inertia pulley or overrunning clutch is designed specifically to absorb this inertia. In principle, this is its main purpose. By extending the life of the belt, it thereby extends the life of other units that were previously affected by slippage. If you give the numbers, then the load on the belt is reduced from 1300 to 800 Nm, due to which the amplitude of the tensioners is reduced from 8 mm to two millimeters.
How is the overrunning clutch arranged?
It is arranged to disgrace simply. The expression "outrageously" is used by various bloggers to show that there is nothing special about the inertial pulley. Nevertheless, engineers from the well-known company INA, which is one of the world leaders in the production of plain and rolling bearings, guessed before its creation only in the 90s.
The clutch consists of two clips - external and internal. The outer one is connected directly to the generator armature shaft. The outer one acts as a pulley. Between the cages there is a needle bearing, but in addition to conventional rollers, it also includes locking elements with a rectangular or square section. Thanks to these locking elements, the coupling can only rotate in one direction.
The outer and inner races can rotate synchronously with the generator rotor if the vehicle is moving steadily. If the driver decides to change the driving mode, for example, to slow down, due to inertia, the outer clip continues to rotate a little faster, due to which the inertial moment is absorbed.
Signs of clutch failure and its replacement
In some ways, the principle of operation of the overrunning clutch can be compared with the anti-lock brake system (ABS): the wheels do not block, but scroll a little, and therefore the inertia is extinguished more efficiently. But this is where the problem lies, since the load falls on the locking elements of the inertial pulley. Therefore, the resource of its work on average does not exceed 100 thousand kilometers.
It is worth saying that if the clutch jams, it will simply work like a regular generator pulley. That is, there is nothing wrong with this, except that the life of the belt will decrease. Signs of clutch failure:
- a metallic rattle that cannot be confused with anything;
- there are peculiar vibrations at low speeds;
- at high speeds the belt starts to whistle.
Please note that if the clutch is broken, inertial loads increase on all other units that drive the timing belt.
It is not difficult to replace it, for this you just need to buy the same one, but a new one and install it instead of the old one. The problem is that to dismantle it, a special set of keys is required, which not every motorist has. In addition, you will have to remove and, possibly, change the timing belt itself. Therefore, we recommend that you contact the service station, where everything will be done correctly and they will give a guarantee.
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