During the operation of the rack and pinion, in order to reduce the friction system of the rack and pinion, it needs to be lubricated. Rack and pinion lubrication mainly has two purposes, one is to promote the sliding between the tooth surfaces, that is, to reduce the friction coefficient of the tooth surface; the other is to suppress the high temperature of the tooth surface due to friction. In order to meet the above two situations, it is necessary to select the appropriate lubrication method and lubricating oil to avoid mechanical failure caused by poor lubrication. Today, I will introduce the lubrication methods and functions of the rack and pinion.

Gear and rack lubrication

Gear lubrication can be roughly divided into the following three types:

(1) Grease lubrication method

(2) Splash lubrication method (oil bath lubrication)

(3) Forced lubrication method (circulating oil injection lubrication)

The lubrication method needs to be properly selected according to the usage conditions of the gear. The selected benchmark is mainly based on the peripheral speed (m/s) and the number of revolutions (rpm) of the gear.

Generally, when the lubrication method is classified according to the peripheral speed, grease lubrication should be used at low speed, oil bath lubrication should be used at medium speed, and forced lubrication should be used at high speed. However, this is just a general principle. Occasionally, at relatively high turnover speeds, grease lubrication is still used for maintenance, etc. reasons.

For low-speed and light-load gears, grease can be used. However, regular re-grease is required, especially when used in open structures. Lubricating oil deteriorates and the amount of oil decreases after prolonged use. Regular inspection, exchange and replenishment are necessary. The failure of oil and the use of inappropriate lubricating oil are the causes of tooth surface damage such as sintering and gluing of the tooth surface. For gears used at high speed and heavy load, worm gears and staggered shaft helical gears that are prone to wear, it is necessary to pay great attention to the selection of the type, amount and lubrication method of lubricating oil. Especially the choice of lubricating oil is very important.

Below, the three lubrication methods are briefly explained.

(1) Grease lubrication method

The grease lubrication method is mainly used in relatively low-speed open and closed gearbox transmissions.

Regarding the grease lubrication method, there are various issues to be aware of. The following three points are mainly introduced here.

   1. Choose the appropriate consistency of grease

   Especially in sealed gear boxes, to keep the grease flowing continuously in the lubricated parts, it is necessary to choose a high-fluidity grease.

   2. Not suitable for high-load, continuous operation occasions

   Because the cooling effect of lubricating oil is far less than that of lubricating oil, the problem of temperature rise will occur under the condition of high load and continuous operation.

   3. Appropriate use of grease

   Too little grease will not achieve the purpose of lubrication, on the contrary, in a sealed gearbox, too much grease will cause excessive stirring loss.

(2) Splash lubrication method (oil bath type)

The splash lubrication method uses the gear box as the oil tank, immerses the gear in the lubricating oil to a certain depth, and relies on the oil splashed when the gear rotates to lubricate the gear and bearing parts. When using oil bath lubrication in low-speed gearbox, the peripheral speed should be above 3m/s.

   There are a number of issues to be aware of when using splash lubrication (oil bath). The oil level regulations and the maximum oil temperature of the gearbox are explained here.

   1. The height of the oil surface

    The greater the amount of lubricating oil used, the greater the stirring loss. On the contrary, if the amount of oil is too small, the expected lubricating and cooling effects cannot be achieved.

    After the gear starts to rotate, the oil level is lower than when the gear is stationary. If the height difference is too large, it is necessary to take measures to improve it. For example, increasing the oil quantity at standstill or installing an oil pan, etc.

    2. The extreme temperature of the gearbox

    The temperature in the gearbox increases with the friction loss of gears and bearings and the stirring loss of lubricating oil. A rise in temperature can cause various adverse effects. For example:

      Lubricating oil viscosity drops

      Deterioration of lubricating oil

      Deformation of gearboxes, gears, shafts, etc.

      Backlash reduction

  Recently, with the advancement of production technology, high-performance lubricants have been increasing. As a general reference, the limit temperature is around 80°C to 90°C.

  When the temperature exceeds this limit, it is necessary to take measures to enhance the heat release of the gearbox to achieve the purpose of cooling the gearbox. For example, install cooling fins in the gearbox, or install fans on the shaft to supply air.

 (3) Forced lubrication method

The forced lubrication method is to use the oil pump to directly lubricate the meshing part. According to the method of oiling, it is divided into three types: drip type, spray type and spray type.

The three methods are briefly explained below.

    drop

    The lubricating oil is directly injected into the meshing part using the guide tube.

    jet

    The lubricating oil is sprayed directly to the meshing part using the fuel injection nozzle.

    spray

    The lubricating oil is converted into a mist by compressed air and sprayed into the meshing part of the gear teeth. This lubrication method is especially commonly used in high-speed transmissions.

  The forced lubrication method is mainly used in special high-speed and large-scale gear devices because it requires a series of supporting devices such as oil tanks, oil pumps, filters, and piping.

  The forced lubrication method can send an appropriate amount of lubricating oil that has been filtered, cooled and has a suitable viscosity to the meshing part, which is the best gear lubrication method.