Created on：2021-04-07 15:44

# Performance parameters of gear pump

Performance parameters of gear pump

If the cycloidal gear pump wants to be high pressure, it needs to use the end clearance compensation structure, and its working pressure can reach 16MPa.

2.1.4 performance parameters

The main performance of gear pump is pressure, displacement, speed, efficiency and life.

(1) The maximum pressure of small and medium displacement gear pump with good axial clearance and radial clearance compensation measures is more than 25MPa, and the newly launched internal gear pump even reaches 40MPa. The rated pressure of large displacement gear pump is 16 ~ 20MPa.

(2) Estimation and range of displacement the displacement of hydraulic gear pump is the main specification parameter of the pump, which mainly depends on the geometric parameters such as the number of teeth Z, modulus, tooth width b, etc. the approximate calculation formula of displacement of gear pump with various structures is shown in the table below. The displacement range of hydraulic gear pump products is very wide, from 0.05 to 800 ml / R, but the commonly used displacement is 2.5 to 250 ml / R.

Approximate calculation formula for displacement of gear pump with various structures

 Type of pump 排量（ml/r）近似计算式 说明 渐开线标准齿形（压力角a=20°，齿顶高系数f=1）的外齿轮泵 V=2πKzm2B×10-3(此式在假设齿间工作容积和轮齿有效体积相等条件下导出) z-齿数，z=z1=z3；m-模数，mm；B-齿宽，mm；K-考虑到轮齿实际集合形状差异的修正系数。z=620时，取K=1.1390.004z 渐开线标准齿形（压力角a=20°，齿顶高系数f=1）的内齿轮泵 V=πBm2(4z1-z1/z2-0.75) ×10-3 z1、z2-主动齿轮及齿圈的齿数；B-齿宽，mm；m-模数，mm 一齿差摆线针轮齿环泵 V=2πeBDe(z2-0.125) ×10-3 e-啮合副的偏心距，mm；B-齿宽，mm；De-针齿齿顶圆直径，mm；z2-外转子齿数

(3) The speed of micro gear pump is high, up to 20000 R / min. the rated speed of gear pump commonly used in engineering is 2000 ~ 2500 R / min. The lower speed limit of gear pump is usually 300 ~ 500r / min. It can be seen from formula (1-10) that when the pump speed is too low, because the output flow is too small, the proportion of leakage flow increases, so that the volumetric efficiency of the hydraulic pump drops to a very low level, it is difficult to form good lubrication and cooling conditions, resulting in rapid heating and damage. Therefore, the minimum speed of the pump is generally specified by the manufacturer.

(4) Efficiency the typical efficiency characteristic curves of gear pumps with various structures are shown in Fig. U. It can be seen that the performance of the gear pump with clearance compensation measures is obviously better than that of the fixed clearance type, and the performance of the internal gear pump is better than that of the external gear pump.

(5) The service life of the low pressure gear pump is 3000 ~ 5000h, the service life of the high pressure external gear pump is only a few hundred hours under the rated pressure, and the service life of the high pressure internal gear pump is 2000 ~ 3000h.

(6) Main structural parameters the main structural parameters of gear pump are tooth width b, gear modulus m and tooth number 2.

When the tooth width B is larger, the total efficiency of the gear pump is higher, but when the pump pressure is higher, the load on the gear shaft and bearing is too large. The module m of gear directly affects the structural parameters of pump, such as pressure, displacement, pulsation, noise and tooth width B. Increasing the modulus and reducing the number of teeth are helpful to reduce the volume of the pump, but too few teeth will increase the flow and pressure pulsation of the pump.

The number of teeth of gear is generally z = 6 ~ 30, low-pressure gear pump generally requires small flow pulsation, so it is mostly z = 13 ~ 20; high-pressure gear pump requires large root strength, so the modulus is large, and the number of teeth is small, generally z = 6 ~ 14. In order to avoid undercutting and weaken the root strength, it is necessary to modify the tooth profile.

The relationship between tooth width B and modulus m of gear is b = km, K is the tooth width coefficient, the value range of low pressure gear pump K is 6 ~ 10, and the value range of high pressure gear pump K is 3 ~ 6. The higher the working pressure is, the smaller the K should be.

The module m of the gear mainly depends on the flow rate of the pump. The module range of the medium and low pressure gear pump with the flow rate q = 4 ~ 125L / min is m = 1.5 ~ 5mm. The larger the flow rate is, the larger the module is.

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