As the core component of electric vehicle, drive motor requires high reliability, high power density, wide efficiency range, wide speed regulation range and strong overload capacity. As a precision part, the bearing itself is the key core of the drive motor. High reliability motors need high-performance bearings to ensure.
Brief introduction of main design concepts of bearings
In the traditional design, the mathematical model is established, the objective function and constraint conditions of bearing design are established, and the traditional coefficient value method and traditional component structure are used to design, that is, the details of the internal design structure of the bearing are obtained. Because of its special performance, the drive motor bearing needs to break through the traditional thinking in the design concept. It is different from the ordinary bearing in the aspects of bearing structure design, coefficient value, material selection, heat treatment requirements and component structure form.
Selection of bearing materials
Due to the requirements of high performance and high reliability of drive motor bearings, the selection of materials is also different from that of ordinary bearings.
01 Selection of high quality bearing steel
In recent years, due to the improvement of steel smelting technology, the oxygen content is greatly reduced and the service life of bearings is doubled. According to the traditional bearing life calculation method, 6004 bearing: cr=9400n, c0r=5000n, PR as the maximum 2150n, speed as the maximum 7000rpm, l10= (9400/2150) 3=83.57 (million revolutions), then lh=199h. If the bearing life requirement is 160000 km, and the speed is 100km/h, it takes 1600 hours. Generally, the experimental life is 3 ~ 8 times of the theoretical value, while the actual experimental results have reached more than 10 times. Due to the requirements of high reliability of the drive motor, high-quality bearing steel should be selected for the selection of raw materials of the ferrule, because its oxygen content and the control of non-metallic inclusions are more strict, which plays an important role in ensuring the service life of the bearing.
02 Selection of lubricating grease
Grease is one of the keys that affect the life of bearings. The lubricating grease is composed of base oil, thickener and additives. The selection of lubricating grease should be based on the working conditions of the bearing.
(1) Base oil. The high speed of bearings requires high DN value lubricating grease, and the selection of DN value should generally be more than 700000. Low base oil viscosity can reduce friction heat and bearing temperature rise, and can reduce low temperature starting torque of bearings, so as to reduce energy consumption, but too low base oil viscosity will reduce the high temperature resistance, bearing capacity and anti stripping capacity of lubricating grease. Therefore, finding a suitable base oil viscosity value through repeated tests is one aspect of selecting the appropriate grease to deal with the high and low temperature resistance of the drive motor. The low temperature limit of the drive motor bearing is generally -40 ℃ ~ -50 ℃, but the high temperature ambient temperature is not too high, which is generally about 90 ℃. Therefore, the maximum temperature of the bearing can be inferred. Therefore, grease with good viscosity temperature performance and low temperature performance should be selected.
(2) Thickener. The good shear resistance and oil separation ability of lubricating grease are conducive to the performance of high-speed lubricating grease, which depends on the performance and structure of thickener. When the bearing runs at high speed, the thickener fiber structure is severely sheared and damaged, and the lubricating grease is sheared and diluted. Therefore, a harder and high oil rate lubricating grease should be selected.
(3) Additives. The characteristics of rapid acceleration and deceleration of the bearing make the grease subject to more impact and agitation, which has a negative impact on the service life of the grease. Therefore, it is required that the grease should have high activity additives, and extreme pressure additives can be selected. Although the radial load on the bearing is not large, it can provide longer service life for the grease to a certain extent because it can optimize the bearing capacity of the moving surface.
It was suggested that electric corrosion is also a form of bearing failure, but this failure is rare in the drive motor bearing at present, but the response to this failure is to choose conductive materials from grease additives, but there is a risk of noise increase after actual addition. The choice of lubricating grease is finally verified by experiments.
03 Sealing material
At present, there are both sealing rubber rings and dust covers, most of which are dust covers. Non-contact seals do not have high requirements for grease leakage, and the working condition of clean surrounding environment is applicable. On the other hand, the choice of rubber ring material has also become the key. Considering the wear resistance of rubber ring material and the compatibility of grease, of course, on the premise of meeting the performance, we should also consider the cost.
04 Cage material
At present, the driving motor speed of passenger cars is generally 11000 ~ 14000rpm at home, while it has reached 16000 ~ 20000rpm abroad. At present, there are both steel and nylon cages on the market. Steel wave cages have high strength and good adaptability to high and low temperatures. However, it is undeniable that its high friction coefficient with the steel ball is not conducive to the operation of the bearing at a higher speed. Due to its superior self-lubricating performance and low friction coefficient with steel ball, nylon cage is more suitable for the design of high-speed operation. Ordinary PA66 or PA46 have corresponding temperature resistance limit, but at present, the ambient temperature of drive motor bearing is also within its application range. Otherwise, other higher temperature resistant materials should be considered. Therefore, the selection of cage materials should be based on the specific working conditions.
05 Nine common lubrication methods for bearings
(1) Manual lubricating oil
When it is found that the lubricating oil of the bearing is insufficient, it is the most original method to supply oil with an oiler in time. This method is difficult to maintain a certain amount of fuel, and there is a great risk of forgetting to refuel due to negligence. It is usually only used in light load, low-speed or intermittent sports. It is best to set a dust cover or ball valve on the oil filler hole, and use felt, cotton, wool, etc. as the filtering device.
(2) Drip lubrication
Roughly a certain amount of lubricating oil is supplied from the container through holes, needles, valves, etc., and the most classic is the oil drip cup. The amount of oil dripping varies significantly with the viscosity of lubricating oil, bearing clearance and the position of oil supply hole. It is used for light load and medium load bearings with peripheral speed less than 4 ~ 5m / s.
(3) Oil ring lubrication
It can only be used for the lubrication method of horizontal shaft. The lubricating oil in the oil pool is brought into the bearing by the ring which is hung on the shaft and can rotate. Suitable for medium and high speed bearings with shaft diameter greater than 50mm. The oil ring should preferably be seamless. When the width diameter ratio of the bearing is less than 2, only one oil ring can be used, otherwise two oil rings are required.
(4) Oil rope lubrication
The lubricating oil in the oil cup is led into the bearing by the capillary action and siphon action of the oil rope, which is used for light load and medium load bearings with peripheral speed less than 4 ~ 5m / s. The oil rope also has the function of filtration.
(5) Oil pad lubrication
Use the capillary action of the oil pad to apply the lubricating oil in the oil pool to the surface of the shaft diameter. This method can keep the friction surface clean, but the dust will also block the pores and cause insufficient oil supply. The oil supply of oil pad lubrication is usually only 1/20 of that of oil lubrication.
(6) Oil bath lubrication
The lubrication method of immersing a part of the bearing in lubricating oil. It is suitable for the lubrication of low and medium speed bearings. A part of the bearing is immersed in the groove, and the lubricating oil is carried by the rotating bearing parts, and then flows back to the oil groove. The oil level should be slightly lower than the center of the lowest rolling element.
(7) Splash lubrication
The lubricating oil splashed by the tapping of the rotating parts in the oil tank is supplied to the bearing, which is suitable for bearings with higher speed.
(8) Spray lubrication
The lubrication method of atomizing and spraying lubricating oil on the friction surface is suitable for high-speed bearings.
(9) Pressure oil supply lubrication supplies oil to the bearing by the pressure of the lubrication pump, and recovers the lubricating oil from the bearing to the oil pool for recycling. It is the most stable lubrication method with the largest amount of oil supply, which is suitable for high-speed, heavy-duty and important sliding bearings.
More about UNIM HVAC System Bearing:
HVAC bearings are a basic, yet vital piece of the HVAC system, expected to keep everything in your device moving along as planned to the extent that this would be possible. They limit friction when the fans are blowing, just as potential noise pollution. Very much like some other mechanical part, the affordable HVAC Bearings price in your HVAC can be presented to a lot of mileage over the long term, which implies they may ultimately quit filling in as they ought to. Luckily, at HVAC Parts Direct, we have a wide assortment of the new course for you to browse for repairs.
Affordable HVAC Bearings prices are a part that can be found in various areas within your HVAC. The more a bearing is presented to ordinary use, the faster it will start to wear out. In a perfect world, a bearing would keep going however long the heater does, yet once in a while, they don't. Helpless upkeep can lessen the bearing and HVAC life expectancy.
2022-08-01
