The dynamic characteristics of the gear system mainly include gear strength, connection reliability, lubrication characteristics, etc. Among them, the gear strength is mainly evaluated by the dynamic inter-tooth force, the connection reliability is mainly evaluated by the radial force of the bushing, and the lubrication characteristics are mainly evaluated by the oil film thickness of the bushing. The basic parameters of the gear remain unchanged, and the effects of backlash, fuel injection pump load and tooth width on the dynamic characteristics of the gear system are studied; Taking the gear on the transmission chain of the fuel injection pump as an example, considering the parameters such as the mass and rotational inertia of different gears, the dynamic inter-tooth force of the crankshaft gear-camshaft gear, the radial force of the fuel injection pump idler gear and the change of the bushing oil film thickness of the camshaft gear and the fuel injection pump idler gear at each speed are analyzed.
When designing the gear system, the backlash is usually 0.1~0.3mm. Considering the influence of machining, assembly, thermal deformation and other factors, the backlash may fluctuate within a certain range. Considering the influence of various errors, the backlash is selected as 0, 0.1, 0.2, 0.3 and 0.4mm to evaluate the impact of backlash on the dynamic characteristics of the gear, The inter-tooth force at the driving side, the inter-tooth force at the back side and the radial force of the bushing of the gear system with different backlash are shown in Figures 1 to 3.
It can be seen from Figures 1 to 3 that the tooth side clearance is 0, 0 １、０. ２、０. ３、０. At 4mm, the maximum inter-tooth force at the driving side is 17756 ７、１８ １０３. ７、１７ ９６９. ９、１９ ６７５. ２、２０ ９２２. 9N, the maximum back interdental force is 12677 ５、１２ ４８８. ０、１２ １６７. ７、１１ ９４３. ６、１２ ２８７. 4N, the maximum radial force of bushing is 9232 ７、９ ７８２. ７、９ ４７５. ２、９ １６８. １、８ ８６４. ４ Ｎ； Within the design range of the backlash, the influence of the backlash on the inter-tooth force of the engine is mainly reflected in the inter-tooth force on the drive side. On the whole, the peak value of the inter-tooth force on the drive side increases with the increase of the backlash, but when the backlash changes little, the peak value of the inter-tooth force on the drive side does not change significantly, and every change of the backlash is 0 1mm, the peak value of the force between the teeth on the driving side changes from 1% to 2%; The local peak values corresponding to different crankshaft angles do not meet the above rules. Some of the peak values of the inter-tooth force on the drive side increase with the increase of the gap, and some of the peak values decrease with the increase of the gap. The peak values of the inter-tooth force on the drive side corresponding to each crankshaft angle in the case of small gap are small, and the peak values corresponding to each crankshaft angle in the case of large gap are increased, and the inter-tooth force in the whole cycle is more uneven, which is not conducive to reducing engine noise; The influence of the backlash on the back side inter-tooth force is very small, but considering the influence of the speed fluctuation, load and other factors on the dynamic knocking of the gear, it is not excluded that the variation of the backlash will have a significant impact on the back side dynamic inter-tooth force in other models, which needs to be analyzed in combination with specific models and boundary conditions; In this model, the effect of the increase of the backlash on the radial force of the bushing is not obvious.
Tooth side clearance is 0 and 0 respectively １、０. ２、０. ３、０. At 4mm, the oil film thickness of camshaft gear bushing and injection pump idler gear bushing are shown in Fig. 4 and Fig. 5.
It can be seen from Figure 4 and Figure 5 that at low speed, within the design range of the tooth side clearance, the influence of the change of the tooth side clearance on the oil film thickness of the bushing is very small and can be ignored, but near the rated speed, the oil film thickness of the bushing fluctuates greatly, which should be noted in the actual situation.
To sum up, the influence of the backlash on the dynamic characteristics of gears is mainly reflected in the dynamic inter-tooth force, which has little impact on the dynamic characteristics of other gears as a whole. When the gear strength margin is large, the requirements on the accuracy of the backlash can be appropriately relaxed, but considering the impact of vibration and noise, the backlash should be reduced as much as possible.