German PERMA bearings PERMA models PERMA prices

PERMA bearings are precision mechanical components that convert sliding friction between the rotating shaft and the bearing housing into rolling friction, thereby reducing frictional losses. Rolling bearings generally consist of four parts: inner ring, outer ring, rolling elements, and cage. The inner ring fits with the shaft and rotates with it; the outer ring fits with the bearing housing to provide support; the rolling elements are evenly distributed between the inner and outer rings by means of the cage, and their shape, size, and quantity directly affect the performance and service life of the rolling bearing; the cage ensures uniform distribution of the rolling elements, guides their rotation, and provides lubrication.

PERMA bearing classification

1) Combined type: Combined needle roller bearings are bearing units composed of radial needle roller bearings and thrust bearing components. They feature a compact structure, small volume, and high rotational accuracy, capable of bearing high radial loads while simultaneously accepting certain axial loads. The product offers diverse structural forms, wide adaptability, and ease of installation. Combined needle roller bearings are widely used in various mechanical equipment such as machine tools, metallurgical machinery, textile machinery, and printing machinery, enabling highly compact and agile mechanical system designs. [2) Thrust type: Thrust bearings consist of thrust cage assemblies with needle rollers, cylindrical rollers, or balls, and thrust washers. Needle rollers and cylindrical rollers are retained and guided by the thrust cage. When used with DF thrust bearing washers of different series, many different combinations can be provided for the bearing configuration. The use of high-precision cylindrical rollers (needle rollers) increases the contact length, allowing the bearing to achieve high load capacity and high rigidity in a very small space. Another advantage is that if the surfaces of adjacent parts are suitable as raceways, the washers can be omitted, resulting in a compact design. The cylindrical surfaces of the needle rollers and cylindrical rollers used in DF thrust needle roller bearings and thrust cylindrical roller bearings are profiled, which reduces edge stress and improves service life.

PERMA bearing installation

Installation of full-complement needle roller bearings is typically performed using an auxiliary sleeve. In this process, the auxiliary roller or auxiliary sleeve supports the needle rollers to prevent them from falling out. The shaft journal uses its own chamfer to lift the needle rollers. As the needle roller bearing moves slowly inward on the shaft journal, the auxiliary roller or auxiliary sleeve gradually withdraws until it reaches the working position. The outer diameter of the auxiliary roller or auxiliary sleeve should be 0.1―0.3mm smaller than the shaft diameter. During installation, first apply grease to the inner surface of the bearing outer ring, place the needle rollers against the inner surface (leaving a gap when inserting the last needle roller), then push the auxiliary roller or auxiliary sleeve, replacing the shaft journal or bearing inner ring, into the outer ring bore. Align its end face with the installation shaft end face or the end face of the bearing inner ring already installed on the shaft, and then apply pressure using a press or hand hammer. Needle roller bearings can also be installed by applying a thin layer of lubricating oil to the outer diameter of the auxiliary sleeve, inserting it into the bearing outer ring to form an annular hole with the outer ring, and then installing the needle rollers into the annular hole. After installing the needle rollers, push out the auxiliary sleeve with the working shaft. For needle roller bearings without an inner or outer ring, during installation, first apply a thin layer of grease to the rolling surface of the shaft or housing bore, and place the needle rollers sequentially against the grease at the installation site. A gap should be left when placing the last needle roller; the gap size should be approximately 0.5mm along the circumference of the needle roller bearing. Do not forcibly squeeze in the last needle roller or install one fewer needle roller, as forced insertion may jam the bearing preventing rotation, while too few rollers create excessive gap, causing the needle rollers to skew and break during operation. For needle roller bearings with only a stamped outer ring, since the outer ring wall is very thin, do not install by striking with a hand hammer; instead, use a press for insertion. Striking with a hand hammer applies uneven pressure, which can easily cause local deformation of the needle roller bearing outer ring.

PERMA bearing usage instructions

1) Disassembly and assembly of bearings: Clean the bearings thoroughly before installation. During installation, use special tools to press the bearing in evenly and straightly. Do not strike with a hand hammer; striking directly on the bearing is strictly prohibited. If the fit between the bearing ring and the housing bore is loose, repair the housing bore or replace the bearing. Do not resort to makeshift measures such as knurling the bearing mating surface or inserting copper shims. When removing the bearing, use an appropriate puller to extract it; do not strike the bearing with chisels, hand hammers, or similar tools. 2) Bearing lubrication: The common lubricants for rolling bearings are lubricating oil and grease. When the circumferential speed of the shaft is less than 4-5m/s, or in automotive applications where lubricating oil cannot be used, grease lubrication is adopted. The advantages of grease lubrication include simple sealing structure, minimal grease loss, low sensitivity to temperature, and long service life per application. Two points must be observed when using grease: First, select the appropriate grade of grease according to the vehicle manual. For example, sodium-based grease is not suitable for automotive water pump bearings due to its poor water resistance. Second, add an appropriate amount of grease into the bearing; generally, filling 1/2-l/3 of the bearing cavity is advisable. Excessive grease is not only useless but also increases operating resistance, causing heating. Special attention should be paid to automotive wheel hub bearings; "hub-empty lubrication" is recommended, meaning only a moderate layer of grease should be applied to the bearing. Otherwise, it will not only cause waste and poor heat dissipation but also lead to grease overflow due to heating, which may affect braking performance. The advantages of lubricating oil lubrication include low frictional resistance and heat dissipation capability; it is mainly used for high-speed bearings and those operating in higher ambient temperatures. Select the grade of lubricating oil according to the vehicle manual and replace it promptly according to the maintenance schedule. After draining the old oil, clean the mechanism before adding new oil. Fill the oil to the specified mark or level with the filler port (depending on the specific vehicle structure and requirements); do not overfill.

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