Hydraulic tensioner construction
The tensioner is installed on the loose side of the timing system, which mainly supports the guide plate of the timing system and eliminates the vibration caused by the speed fluctuation of the crankshaft and the polygon effect of itself. The typical structure is shown in Figure 2, which mainly includes five parts: shell, check valve, plunger, plunger spring and filler. The oil is filled into the low pressure chamber from the oil inlet, and flows into the high pressure chamber composed of the plunger and the shell through the check valve to establish the pressure. The oil in the high pressure chamber can leak out through the damping oil tank and the plunger gap, resulting in a large damping force to ensure the smooth operation of the system.
Background knowledge 2: Damping characteristics of hydraulic tensioner
When a harmonic displacement excitation is applied to the plunger of the tensioner in Figure 2, the plunger will generate damping forces of different sizes to offset the influence of the external excitation on the system. It is an effective method to study the characteristics of the tensioner to extract the force and displacement data of the plunger and draw the damping characteristic curve as shown in Figure 3.
The damping characteristic curve can reflect a lot of information. For example, the enclosed area of the curve represents the damping energy consumed by the tensioner during a periodic movement. The larger the enclosed area, the stronger the vibration absorption capacity; Another example: the slope of the curve of the compression section and the reset section represents the sensitivity of the tensioner loading and unloading. The faster the loading and unloading, the less the invalid travel of the tensioner, and the more beneficial it is to maintain the stability of the system under the small displacement of the plunger.
Background knowledge 3: Relationship between plunger force and loose edge force of chain
The loose edge force of the chain is the decomposition of the tension force of the tensioner plunger along the tangential direction of the tensioner guide plate. As the tensioner guide plate rotates, the tangential direction changes simultaneously. According to the layout of the timing system, the corresponding relationship between the plunger force and the loose edge force under different guide plate positions can be approximately solved, as shown in Figure 5. As can be seen in Figure 6, the loose edge force and the plunger force change trend in the working section is basically the same.
Although the tight side force can not be directly obtained by the plunger force, according to engineering experience, the maximum tight side force is about 1.1 to 1.5 times the maximum loose side force, which makes it possible for engineers to indirectly predict the maximum chain force of the system by studying the plunger force.
