Structure and correct installation method of timing belt tensioner

The tensioning pulley is an important component in the timing system. Its function includes providing the required tensioning force for the timing belt, avoiding tooth skipping of the timing belt, and compensating the elongation of the timing belt after wear and aging, so as to ensure that the belt is in the best working state.

Structure and performance requirements of tensioning wheel

The shape and structure of the tensioning wheel used in the timing system will be different with different engine models. Take ina long arm tensioner as an example. The tensioner is mainly composed of base, tensioner arm, torsion spring, pulley, bearing, shaft sleeve, bolt and other accessories (Fig. 1). The tensioning wheel can automatically adjust the tensioning force through the torsion spring, which belongs to an advanced self-adjusting tensioning wheel.

High quality tensioning wheel should have the characteristics of stable tensioning force, low vibration, low noise and long service life, which puts forward higher requirements for manufacturing technology and materials. The bearing quality directly affects the performance of the tensioner. Ina tensioner uses eco bearing specially designed for belt transmission. The steel ball of this bearing is larger than that of ordinary standard bearing and can bear greater load. An assembly groove is also designed on the bearing to facilitate the assembly of the plastic pulley. Labyrinth seal ring can effectively inhibit grease leakage and intrusion of impurities, especially suitable for high-speed working conditions. Most of the grease used by ina is specially developed by grease manufacturers and only provides ina with high-quality grease. In addition, the pa66gb40 and PA66GF25 plastics used in ina tensioning wheel not only have good wear resistance, but also can withstand the high temperature of 150 ℃, but also have lighter weight, which is conducive to improving the fuel economy of the engine.

Installation specification for tensioning wheel of common vehicle models

Proper tension is required for the timing belt to work. If the tension is too large, it is easy to produce indole sound and shorten the life of the belt. If the tension is too small, the belt is easy to vibrate, resulting in wrinkling or damage, and tooth skipping in serious cases. Therefore, when replacing the tensioning wheel, pay special attention to the adjustment of tensioning force and operate in strict accordance with the requirements of the maintenance manual. Different types of tensioning wheels, such as eccentric shaft sleeve adjustment type, torsion spring preload type and hydraulic self-adjusting type, have different adjustment methods of tensioning force. Next, take three common engine series as examples to briefly introduce the operation steps of tensioning wheel installation.

1 Buick Chevrolet engine tensioner

Applicable models: Buick Kaiyue 1.6 / Kaiyue hrv1.6; Chevrolet Avio 1.4/avio 1.6/lefeng 1.4/lefeng 1.6. Engine model: f16d3d / L95 / L91. Original part No.: 96350550.

(1) Installation steps

① Loosen 3 fixing bolts of water pump and remove the belt. Replace the timing belt and tensioner, and tighten the tensioner bolt (torque 28 ~ 34nm).

② Check the belt position to ensure that the belt is tight between the tension-free pulleys and that the belt is aligned with the teeth.

③ Hold the water pump body with a 42mm wrench, and then cover the 42mm wrench with a wrench to rotate the water pump and adjust the pointer position of the tensioning wheel (Fig. 2). The first adjustment: turn the water pump clockwise to make the tension wheel pointer exceed the C position; Second adjustment: turn the water pump counterclockwise to turn the tensioner pointer back to position B; The third adjustment: turn the water pump clockwise to align the pointers of the two tensioning wheels, that is, adjust to position C (nominal working position of the tensioning wheel). It should be noted that this repeated adjustment and final alignment is to eliminate the stress of the belt and keep the whole belt under uniform stress.

④ Tighten the fixing bolts of the water pump (torque 8nm), turn the crankshaft clockwise for 2 turns, and check whether the marks on the crankshaft, camshaft and tensioning pulley are still in the specified position, and whether the belt between the tension-free pulley is tight. If any of the marks are not aligned, the entire installation process must be repeated.

(2) Precautions

① Ensure that the tensioning wheel is replaced when the engine is cold.

② In addition to supplying a single tensioning wheel, ina also supplies a timing package to facilitate the replacement of the entire timing system.

2 tensioning wheel of SAIC series engine (Fig. 3)

Applicable model: Roewe 750; Freelander: mg7l / zs180 / zt160 / zt180 / zt190; Rover45/75/800。 Engine model: 20v6, 2.5v6 (kv6, 25k4). Original part No.: LHB 101630, 710000162.

(1) Installation steps

① Install the tensioning wheel on the engine with the engine mounting bolt (torque 49nm), and ensure that the contact surface of the hydraulic shock absorber is in contact with the shock absorber ejector rod.

② Install the timing belt counterclockwise from the crankshaft end. Insert a long handle Allen wrench into the Allen eccentric hole of the eccentric, and use another 8mm Allen wrench to loosen the fixing bolt of the tensioner until the tensioner can rotate.

③ Slowly turn the Allen wrench inserted into the Allen eccentric hole counterclockwise. When the main support contacts the hydraulic shock absorber and pushes it, the timing belt is tensioned.

④ Adjust the tensioning wheel until the stop pin on the shock absorber becomes loose. Pay attention not to turn the tensioning wheel out of the central area during tightening, otherwise it may cause failure.

⑤ Tighten the fixing bolt of the tensioning wheel (torque 10 N · m), and ensure that the tensioning wheel does not rotate. Wait for 2min. After the hydraulic shock absorber returns to its position, confirm again that the stop pin is loose, otherwise steps ② ~ ⑤ must be repeated.

⑥ Tighten the fixing bolts of the tensioning wheel (torque 40 ~ 50nm), and ensure that the tensioning wheel does not rotate. Check again whether the stop pin is loose, otherwise steps ② ~ ⑥ must be repeated.

⑦ Remove the damper stop pin.

(2) Precautions

① The tensioning pulley shall be adjusted when the timing belt is in the "free state", which means that the locking device of camshaft has been fixed; Camshaft bolts have been loosened; The crankshaft timing pin has been fixed; The hydraulic shock absorber is compressed; The 1.5mm stop pin remains in place.

② In addition to supplying a single tensioning wheel, ina also supplies a timing package (Figure 4) to facilitate the replacement of the entire timing system.

3. Tensioning wheel of Volkswagen Jetta 1.9 diesel engine

Engine model: ea188. Original part No.: 038109243n.

(1) Installation steps

① Rotate the crankshaft to TDC and check whether the timing marks of camshaft, crankshaft and oil pump are aligned. After confirmation, remove the timing belt, tensioner and idler.

② Install a new timing belt, tensioner and idler. First, clean the mounting surface of the tensioner on the engine block. When installing the timing belt, do not use any tools (such as screwdriver), otherwise it is easy to damage the timing belt. Do not grease the belt. The fixing plate of the tensioning wheel must be correctly installed on the corresponding timing cover hole. During the whole assembly process, be careful not to damage the fixing plate of the tensioning wheel. Tighten the fixing bolts of the tensioning wheel until the tensioning wheel is completely installed on the engine block. At the same time, ensure that the tensioning wheel can rotate easily.

③ Adjust the tension. Use the special tool to turn the tensioning wheel counterclockwise to adjust the alignment between the convex point and the groove (Fig. 5).

④ Use a torque wrench to tighten the fixing bolt of the tensioning wheel (torque 23nm), and ensure that the relative position of the tensioning wheel does not change during tightening.

⑤ Remove all installation and fixing tools and turn the crankshaft clockwise for 2 turns. Check that the boss and groove on the tensioning wheel are still aligned. If the relative position between the convex point on the tensioning wheel and the groove is offset, steps ③ ~ ⑤ must be repeated.

（2) Precautions

① In any case, the engine crankshaft must be turned clockwise. For example, when aligning the top dead center, if the anchor has passed the top dead center and the crankshaft cannot be rotated back, it must be rotated again and then return to the top dead center.

② Under no circumstances should the engine crankshaft with the timing belt removed be turned.

③ In order to ensure the good matching of timing belt, tensioner and idler, ina timing kit is recommended.