Spline connection. Keyed and splined connections

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

A spline connection is a connection between a female and a male surface (shaft-hole). Splines and grooves are used, which, as a rule, are arranged in a radial order at the engagement site. This connection has sufficient strength and ensures the alignment of the shaft and the hole. The main advantage is that the part can move in the axial direction.

Spline connection: classification

As you understand, there are several ways to secure two parts with a slot. Under certain circumstances, different methods are used. There are involute spline connections. They differ from straight-sided ones in the shape of the tooth (lateral surface) and depressions. They have several undeniable advantages, such as high torque transmission (Nm) and high centering accuracy under considerable load. If we talk about straight-sided connections, then the main advantages are ease of manufacture andcheapness. There are also triangular slots, but they are used less frequently. Most often at the junction of fixed parts with a small torque. Quite often they find their application in thin-walled bushings. In them, the use of other types of connections is not considered acceptable for a number of technological reasons.

Keyed and splined connections

In some cases, a pulley or gear must be mounted on the shafts. If a large torque transmission is also needed, then keyed as well as involute spline connections are used. As for the dowels, prismatic ones are widely used, due to the ease of installation. The main issue is that sometimes it is necessary to make it possible to move the part in the axial direction. In this case, a clearance fit is used, and the key is attached to the shaft with screws. If you need to create a reliable connection in a lightly loaded place, then a segmented key, which has a small length, is well suited. The main difference between splines is that they use more teeth and smaller lugs. Connections are of 3 types: easy-detachable, tight-detachable and fixed. Every year, the methods of processing parts allow us to achieve ever better results from a technological point of view. These are high centering accuracy, interchangeability of failed spare parts and more.

How were problems with the cardan shaft solved?

Now let's look at the effectiveness of splines. ATIn this case, the slot serves to change the length of the shaft, which is required to ensure the alignment of the units, during the installation of which inaccuracies were made. Lubrication is supplied to the support bearing and the spline itself using an oiler. The most commonly used solidol. Since the length of the cardan shaft is such that in many cases the lubricant does not reach all the working friction units, it is quite advisable to reduce the channels through which oil or other liquid flows. You can use transparent inserts. They will make it possible to visually control and timely supply of lubricant to the friction unit. In order for the sliding fork to serve as long as possible, a brass insert is used, which is tucked into the spline connection. Of course, this can significantly reduce the wear of the part. In principle, the spline joint of the propeller shaft is reliable and easy to maintain, but it is not without drawbacks.

Centering Methods

There are several ways to center a straight-sided spline. One of them is outside diameter. To do this, the shaft is milled and then ground along the outer diameter. By the way, this is the cheapest and most efficient centering method. The sleeve is pulled mechanically. This method is used when the bore surface of the sleeve has not been heat treated or thermally improved. If we talk about expensive methods, then this is centering on the inner diameter. The fact is that the shaft is milled and then polished along the side surfaces. The method is used only for preliminary heat treatment of the shaft and bushing. To get evendistributed load on each spline, use centering on the sides. The bore and shaft are thermally improved. Most often, this centering is used for connections with high torque and considerable load.

A few important points

As noted above, keyed and splined connections are used in order to prevent two parts from turning relative to each other. Before installing the part on the shaft, it is checked for strength, which allows you to choose the optimal technical characteristics, such as material, dimensions, weight. If we talk about the percentage prevalence of splines, then straight-sided ones occupy about 80%, and only 10% remain for involute and triangular ones. Depending on the workload of the connection, a series of products is selected, which can be light, medium or heavy. It is important to pay attention to the presence of lubrication in the connection, especially if it is movable. The absence of mineral oil or hard material will result in the coefficient of friction increasing several times. And this is an increased wear of the connection and a decrease in the efficiency of the whole assembly. The supply of oil or grease is carried out by centralized automatic stations (if the number of nodes is more than 50 pieces) or mechanically.

Conclusion

An important point is the restoration of keyed and splined connections. Of course, sometimes it is easier to replace, but when this is not possible, then extensions are used. If ain simple words, then by welding they restore the original state of the product. Most often, arc welding is used, followed by grinding (with high wear). Sometimes it happens that the designation of spline connections does not allow for repairs. This happens when they are easily detachable and not intended for regrinding. To prevent the node from failing, it is necessary to exclude any beating in the connection. This can be ensured in several ways, for example, by installing special gaskets. That, in principle, is all that can be said about what a spline connection is and why it is needed.