A Calculation Method for Whole Cycle Camshaft Torque of Rotary High-pressure Fuel Pump
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摘要: 为提高高压共轨系统常用的转子式高压供油泵峰值扭矩的计算准确性,提出一种凸轮轴全周期扭矩计算方法。计算包含柱塞的液压力、摩擦力、弹簧力和惯性力,根据座圈所受的合力方向,在偏心轮坐标系中确定座圈与偏心轮接触点的位置,并通过坐标变换,得到凸轮轴坐标系下该接触点的坐标,进而计算出不同转角下的凸轮轴扭矩。当只考虑柱塞所受的液压力时,该方法与常用的流量倒推法计算结果相同。计算结果表明,高压供油泵的峰值扭矩可按流量倒推法结果的1.3倍计算;当理论排量和供油压力一定时,峰值扭矩随柱塞直径的增大小幅增大、随着柱塞个数的增多而降低,但柱塞数超过3时,数量增多对峰值扭矩降低的效果减弱。Abstract: In order to improve the peak torque computation accuracy of the rotary high-pressure fuel pump commonly used in a common rail system, a calculation method for whole cycle camshaft torque was proposed. The hydraulic pressure, friction force, spring force and inertia force effected on a plunger were calculated. According to the direction of resultant force on the triangular ring, the location of contact point between the triangular ring and the eccentric wheel was confirmed with the eccentric wheel coordinate system. Through coordinate transformation, the coordinates of contact points in the camshaft coordinate system were obtained, and then the camshaft torque at any rotation angle was worked out. When only the hydraulic pressure acted on the plunger is taken into account, the calculation result is the same as the backward flow induction as is the common case. The results show that the peak torque of the high-pressure fuel pump can be regarded as 1.3 times the flow backward induction. When the theoretical fuel delivery and the fuel pressure are constant, the peak torque increases slightly with the increase of the plunger diameter and decreases with the increase of the number of plungers. But the effect of the increased quantity of peak torque reduction is reduced when the number of plunge pistons exceeds 3.
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表 1 Bosch CP3.3型高压供油泵凸轮轴扭矩计算参数
参数名称 数值 最高供油压力 p 160 MPa 柱塞直径 D 7.5 mm 柱塞运动件质量 m 0.045 kg 偏心轮偏心距(半柱塞升程)e 4.1 mm 偏心轮半径 R 15 mm 柱塞弹簧刚度 k 8.2 N/mm 柱塞弹簧预紧力 F0 55 N 泵转速 n 3800 r/min 泵体滑动轴承半径 Rz 12.5 mm 输油泵供油压力 0.5 MPa 输油泵供油量 5 L/min 表 2 忽略柱塞部分所受力的凸轮轴扭矩计算结果
忽略的力 峰值扭矩计算值/
(N·m)减小百分比/
(基值33.05 N·m)柱塞弹簧弹力FS 33.00 0.15% 柱塞惯性力FI 33.04 0.03% 摩擦力FT 28.98 12.31% 表 3 不同柱塞直径和偏心距下的凸轮轴扭矩
柱塞直径/
mm偏心距/
mm最大扭矩/
(N·m)最小扭矩/
(N·m)平均扭矩/
(N·m)6.5 5.4591 34.8473 27.8300 31.6030 6.7 5.1381 34.9448 27.9213 31.6971 6.9 4.8445 35.0455 28.0148 31.7940 7.1 4.5754 35.1503 28.1114 31.8944 7.3 4.3282 35.2594 28.2113 31.9987 7.5 4.1 35.3681 28.3108 32.1026 7.7 3.8902 35.4875 28.4188 32.2162 7.9 3.6957 35.6067 28.5266 32.3295 8.1 3.5154 35.7291 28.6370 32.4457 8.3 3.3481 35.8561 28.7511 32.5661 8.5 3.1924 35.9858 28.8674 32.6890 表 4 不同柱塞个数下的柱塞直径和升程的计算值
柱塞个数 1 2 3 4 5 6 柱塞直径/mm 9.8 8.4 7.5 7.6 6.2 6 偏心距/mm 7.2 4.9 4.1 3 3.6 3.2 表 5 不同柱塞个数下凸轮轴合力最大、最小及峰峰值
柱塞个数 最大合力/N 最小合力/N 合力峰峰值/N 1 12107 0 12107 2 8895.2 8895.2 0 3 8048 7091.2 956.8 4 11086 11086 0 5 8559.7 8270.2 289.5 6 9681.4 9681.4 0 表 6 不同柱塞个数下凸轮轴扭矩最大、最小及峰峰值
柱塞个数 最大扭矩/
(N·m)最小扭矩/
(N·m)扭矩峰峰值/
(N·m)1 87.17 0 87.17 2 43.59 3.48 40.11 3 33.00 26.26 6.74 4 33.26 23.52 9.74 5 30.82 28.32 2.5 6 30.98 27.39 3.59 -
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