Excavator Main Pump Pilot/Gear Pump Overview
Posted on 08/07/2024
Features: simple and compact structure, small size, light weight, wide speed range, good self-priming performance, insensitive to oil contamination, not easy to bite, easy to process and manufacture, low cost.
Low volumetric efficiency, large flow pulsation and noise. Since the radial balance force of the gear shaft increases the load on the bearing, the pressure increase is limited.
CAT320C Gear Pump
Daewoo-150W Gear Pump
DOOSAN-140V/A Gear Pump
1. External gear pump
1. Displacement and flow
Displacement formula
q0＝2πm2zb（cm3/rev）
Where: m——gear module (cm)
z——number of teeth
b——tooth width (cm)
Assuming the gear speed is n and the volumetric efficiency is ηv, the gear pump flow Q0 is
Q0＝nq0＝2πnm2zbηv（cm3/rev）
2. Structural problems of gear pumps
1) Influence of gear parameters on flow characteristics The number of teeth, tooth width and module of the gear all affect the flow of the hydraulic pump, but increasing the number of teeth will make the structure of the hydraulic pump bulky, and increasing the tooth width will increase the radial unbalanced force of the gear. Increasing the modulus is the most effective way to increase the flow rate of the hydraulic pump. In addition, the instantaneous flow rate of the gear pump is uneven. The more teeth there are, the smaller the flow rate pulsation is, and the fewer teeth there are, the larger the flow rate pulsation is. Gear forms include spur gears, helical gears and herringbone gears. Helical gears move smoothly, but axial force will occur. Herringbone gears move smoothly and have no axial force, but are more difficult to process.
2) Oil trapping problem The oil trapping problem is serious, and a unloading groove needs to be opened.
3) Radial force imbalance problem Due to the different inlet and outlet oil pressures, the pressure distributed on the outer diameter of the gear and the inner cavity of the pump body is unbalanced. To solve this problem, a pressure balance groove can be opened, but this makes the high-pressure oil chamber close to the low-pressure oil chamber, increasing leakage. In addition, the method of reducing the diameter of the oil pressure port can be used to reduce the area where the pressure oil acts on the gear, which can also reduce the radial unbalanced force.
4) Speed problem The speed cannot be too high or too low. If the speed is too high, the oil cannot fill the entire working oil chamber under the action of centrifugal force, and the resistance to oil absorption is increased, which is prone to cavitation. Generally, the maximum circumferential speed does not exceed 5~6 m/s. If the speed is too low, the volumetric efficiency will be relatively reduced. The minimum circumferential speed can be calculated according to the following formula
vmin = 0.17p/(m/s)
Where: p——hydraulic pump working pressure (kgf/cm2)
0E50——relative viscosity of oil at 50℃
HITACHI-EX200-1 Gear Pump
HYUNDAI-150W Gear Pump
KAWASAKI-K3V112 Gear Pump
2. Wedge-type internal meshing gear pump
1. Flow calculation
Displacement calculation
q0 = πm2b[2z＋(1－i)(1－1/12·π2cos2α0)] (cm3/rev)
Where: b——tooth width (cm)
m——gear module (cm)
z——number of teeth on the driving pinion shaft
i——ratio of the number of teeth on the driving pinion shaft to the number of teeth on the driven gear
α0——Gear pressure angle
When the pressure angle α0 is 20°, the above formula is
q0＝πm2b[2z＋0.274(1－i)]（cm3/rev）
The flow rate is calculated as follows
Q0＝πnηvm2b[2z＋(1－i)(1－1/12·π2cos2α0)]（cm3/rev）
KAYABA-SERIES Gear Pump
KOMATSU-PC50 Gear Pump
Kobelco SK120-SK200-SK300-EX200B Gear Pump
3. Cycloidal rotor pump
1. Flow calculation
Displacement calculation
q0＝πb(D12－D22)（cm3/rev）
Where: b——Rotor width (cm)
D1——Inner rotor long diameter (cm)
D2——Inner rotor short diameter (cm)
Flow calculation
Q0＝nπηvb(D12－D22)（cm3/rev）
UCHIDA-A10V43 Gear Pump
VOLVO-EC360 Gear Pump
Tags: Hydraulic Pumps Supplier, Gear Pump, Pilot Pump, Piston Pump, Gear Pump Supplier, Pilot Pump Manufacturer, Hydraulic Pump Parts Supplier