2.1 轉向阻力矩計算
2.1 calculation of steering resistance torque
液壓轉向系統(tǒng)匹配設計，先應計算轉向阻力矩。一般地，轉向阻力矩分為原地轉向阻力矩和行駛轉向阻力矩，考慮到原地轉向阻力矩是行駛轉向阻力矩的2～3倍，自上料攪拌車轉向系統(tǒng)應按滿足實現(xiàn)原地轉向力矩要求進行設計。影響汽車轉向阻力矩的因素有汽車前軸負荷、輪胎與地面之間的摩擦系數(shù)、輪胎氣壓等。目前常用的經驗計算公式：
In the matching design of hydraulic steering system, the steering resistance moment should be calculated first. Generally, the steering resistance moment is divided into in-situ steering resistance moment and driving steering resistance moment. Considering that the in-situ steering resistance moment is 2 ~ 3 times of the driving steering resistance moment, the steering system of the self loading mixer shall be designed to meet the requirements of in-situ steering torque. The factors that affect the steering resistance moment of automobile include the load of automobile front axle, the friction coefficient between tire and ground, tire pressure and so on. Currently commonly used empirical calculation formula:
式中：Mr1——轉向阻力矩，N·m；
Where: MR1 - steering resistance moment, n · m;
f ——輪胎與地面摩擦系數(shù)，取 0.7；
F - friction coefficient between tire and ground, taken as 0.7;
G1——車輛轉向軸軸荷，N；
G1 -- axle load of vehicle steering axle, N;
P——車輛輪胎胎壓，kPa。
P -- tire pressure of vehicle tire, kPa.
自上料攪拌車單軸軸荷 75000N，正常工作胎壓550kPa，代入數(shù)值可得 Mr1= 6462N·m。
Since the maximum single axle load of the charging mixer is 75000n and the normal working tire pressure is 550kpa, the value can be substituted to get MR1 = 6462n · M.
2.2 轉向油缸選型及校核
2.2 steering cylinder selection and verification
轉向系統(tǒng)設計需要考慮兩種情況，種情況，轉向油缸隨車橋確定，且受結構限制不能隨意改變，此刻應計算轉向橋載荷，通過調整整機質心，使轉向橋載荷在合適的范圍內，同時對轉向油缸進行校核計算。第二種情況，轉向橋所受載荷已確定，需要對轉向油缸進行選型設計，使之符合轉向要求。目前自上料攪拌車選用林德10t 車橋，油缸性能參數(shù)已經確定，先需要對油缸進行校核，參數(shù)見表 1。
Two situations need to be considered in the design of the steering system. In the first case, the steering cylinder is determined with the axle and cannot be changed arbitrarily due to structural constraints. At this time, the steering axle load should be calculated, the steering axle load should be within the appropriate range by adjusting the mass center of the whole machine, and the steering cylinder should be checked and calculated at the same time. In the second case, the load on the steering axle has been determined, and the steering cylinder needs to be selected and designed to meet the Steering requirements. At present, Linde 10t axle is selected for the self loading mixer, and the performance parameters of the oil cylinder have been determined. First, the oil cylinder needs to be checked, and the parameters are shown in Table 1.
轉向油缸推力為
The maximum thrust of steering cylinder is
代入數(shù)值，可得 Fmax=76302N
By substituting the value, Fmax = 76302n can be obtained
自上料攪拌車車橋轉向油缸的轉向作用力臂隨轉向角的關系曲線如圖3 所示。車橋轉向角為 32°，由圖可知更小力臂 Rmin＝125mm。
The relationship curve between the steering action arm of the axle steering cylinder of the self loading mixer and the steering angle is shown in Fig. 3. The maximum steering angle of the axle is 32 °. It can be seen from the figure that the minimum force arm Rmin = 125mm.
根據(jù)轉矩公式：Fmax =Mr2 / (Rmin η)
According to the torque formula: Fmax = MR2 / (Rmin) η)
式中：Rmin——更小力臂，mm；
Where: Rmin - minimum force arm, mm;
η——轉向機械效率，取 0.8；
η—— Steering mechanical efficiency, taken as 0.8;
Mr2 ——轉向力矩，N·m。
MR2 -- steering torque, n · M.
代入數(shù)值，可得 Mr2=7630.2N·m
By substituting the value, we can get MR2 = 7630.2n · M
根據(jù)計算結果 Mr2＞Mr1，滿足使用要求。
According to the calculation results, MR2 ＞ MR1, it meets the use requirements.
2.3 轉向器排量的確定
2.3 determination of displacement of steering gear
當轉向輪從一個極限位置到另一個極限位置，方向盤轉過的圈數(shù)n，既要滿足行駛工況，防止車輪轉向過大導致車身穩(wěn)定性差，又要滿足有較少的作業(yè)循環(huán)，提高操作便利性。一般設計中，n=3～5 圈。
When the steering wheel moves from one limit position to another, the number of turns n of the steering wheel should not only meet the driving conditions and prevent the poor stability of the vehicle body caused by excessive steering of the wheel, but also meet the requirements of less work cycles and improve the convenience of operation. In general design, n = 3 ~ 5 cycles.
轉向油缸全行程油液體積：V=SA
Full stroke oil volume of steering cylinder: v = SA
式中：S——活塞行程，mm；
Where: s -- piston stroke, mm;
A——油壓作用面積，mm2。
A - oil pressure action area, mm2.
代入數(shù)值，得出 V=858mL
Substitute the value to obtain v = 858ml
先選取 n=4，則轉向器排量為V/n=858/4=214，對照轉向器廠家樣本，選用排量為 200mL/r 型號的轉向器。
If n = 4 is selected first, the displacement of the steering gear is v / N = 858 / 4 = 214. Compared with the sample of the steering gear manufacturer, the steering gear with a displacement of 200ml / R is selected.
2.4 齒輪泵排量的確定
2.4 determination of gear pump displacement
轉向系統(tǒng)流量：Q=qn
Steering system flow: q = QN
式中：q——轉向器排量，mL/r；
Where: Q -- displacement of steering gear, ml / R;
n——方向盤轉速，取 0.8r/s。
N -- steering wheel speed, taken as 0.8r/s.
代入數(shù)值，得出 Q=160mL/s
Substitute the value to get q = 160ml / s
按照發(fā)動機怠速狀態(tài)下分析，齒輪泵排量
The displacement of the gear pump is analyzed according to the idle state of the engine
qc=60Q/(ndη)
qc=60Q/(nd η)
式中：nd——發(fā)動機怠速轉速，取750r/min；
Where: Nd -- engine idle speed, taken as 750r / min;
η——轉向泵效率，取 0.95。
η—— Steering pump efficiency, taken as 0.95.
代入數(shù)值，得出 qc=13.5mL/r
Substitute the value to get QC = 13.5ml/r
現(xiàn)選用齒輪泵排量為 16mL/r，滿足使用要求。
The displacement of gear pump is 16ml / R, which meets the use requirements.
3 結束語
3 conclusion
全液壓四輪轉向系統(tǒng)具有布置方便、轉向靈活的特點，目前在輪式挖掘機上有普遍應用。本文從液壓轉向原理著手，對四輪液壓轉向在自上料攪拌車上的應用做了詳細介紹，并通過計算分析，對轉向油缸的強度、排量進行校核，確定轉向器及齒輪泵的排量，為液壓轉向系統(tǒng)設計提供一種參考。
Full hydraulic four-wheel steering system has the characteristics of convenient layout and flexible steering. At present, it is widely used in wheel excavator. Starting from the principle of hydraulic steering, this paper introduces in detail the application of four-wheel hydraulic steering in self loading mixer truck, checks the strength and displacement of steering cylinder through calculation and analysis, and determines the displacement of steering gear and gear pump, so as to provide a reference for the design of hydraulic steering system.
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