Splined connection. Key and spline joints

Splined connection is the connection of the female and male surfaces (shaft-hole). Slots and grooves are used, which, as a rule, are located radially in the place of engagement. This joint 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.

Splined connection: classification

As you understand, there are several ways to fix two parts with a slot. In different conditions, different methods are used. There are involute splines. From the right-handed, they differ in the shape of the tooth (lateral surface) and depressions. They have several undeniable advantages, such as the transmission of a large torque (Nm) and high accuracy of centering under a considerable load. If we talk about pryamobochnyh connections, the main advantages are the simplicity of manufacture and cheapness. There are also triangular splines, but they are used less often. Most often in the junction of fixed parts with a small torque. Quite often they find their application in thin-walled sleeves. In them, the use of other types of connections is not considered permissible for a number of technological reasons.

Key and spline joints

In some cases, a pulley or pinion is required on the shafts. If you need more and transmission of a large torque, then keyed, as well as involute splined connections. As for the keys, the prismatic ones are widely used, which is due to the ease of installation. The main question is that sometimes it is necessary to make it possible to move the part in the axial direction. In this case, use a landing with a gap, and the key is attached to the shaft with screws. If it is necessary to create a reliable connection in a low-loaded area, the segment key, which is short in length, is well suited. The main difference between the splines is that a larger number of teeth and smaller protrusions are used. Connections are of 3 types: easy-detachable, tug-detachable and fixed. Every year, the methods of processing parts allow you to achieve all the best results from a technological point of view. This high accuracy of centering, the interchangeability of failed parts and more.

How was the cardan shaft problem solved?

Now let's look at the effectiveness of splined joints. In this case, the slot serves to change the length of the shaft, which is required to ensure the alignment of the units, the installation of which were inaccurate. In the support bearing and the actual slot, the lubricant is supplied by the lubricator. The most commonly used is solidol. Since the length of the PTO shaft is such that in many cases the lubricant does not reach all working friction units, it is quite advisable to reduce the channels through which oil or other liquid enters. You can use transparent inserts. They will make it possible to visually control and timely supply lubricant to the friction unit. To use the sliding fork as long as possible, use a brass insert that is threaded into the splined connection. Of course, this allows you to significantly reduce the wear of the part. In principle, the splined joint of the propeller shaft is reliable and easy to maintain, but it is not without flaws.

Methods of centering

There are several ways to align a straight slotted spline to the center. One of them is the outer diameter. To do this, the shaft is milled, and then grinded by the outer diameter. By the way, this is the cheapest and most effective method of centering. The bushing extends mechanically. This method is used when the surface of the bushing hole has not undergone heat treatment or thermal improvement. If to speak about expensive methods, then this is centering on the inner diameter. The fact that the shaft is milled, and then polished on the side surfaces. The method is used only for preliminary heat treatment of the shaft and bushing. To obtain an evenly distributed load on each slot, centering is used on the sides. The hole and the shaft are improved thermally. Most often, this centering is used for connections with high torque and considerable load.

A few important points

As already noted above, key and spline joints are used to exclude the rotation of the two parts 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 the splines, then the right-wing ones occupy about 80%, while for evolvent and triangular, only 10% remain. Depending on the congestion 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 lubricant in the joint, especially if it is mobile. The absence of mineral oil or solid material will result in several times increasing the coefficient of friction. And this - increased wear of the connection and a decrease in the efficiency of the whole unit. The supply of oil or solidol 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 joints. Of course, sometimes it's easier to perform a replacement, but when this is not possible, then use the build-up. If in simple words, then with the help of welding restore the initial state of the product. The most commonly used arc surfacing with subsequent grinding (with high wear). Sometimes it happens that the designation of slotted joints does not allow repairs. This happens when they are easily detachable and not intended for re-sharpening. In order for the node not to fail, it is necessary to exclude any beating in the connection. This can be done in several ways, for example by installing special gaskets. Here, in principle, and everything that can be said about what a splined connection is and for what it is needed.