Cardan shaft: what is it?
The transmission of the car performs an important function - it transmits the rotation of the crankshaft to the wheels.
The main elements of the transmission:
- clutch - we talked about it on Vodi.su, it connects and disconnects the gearbox and the crankshaft flywheel;
- gearbox - allows you to transform the uniform rotation of the crankshaft into a certain driving mode;
- cardan or cardan gear - used on cars with rear or all-wheel drive, serves to transfer momentum to the drive axle;
- differential - distributes the moment of movement between the drive wheels;
- gearbox - to increase or decrease torque, provides a constant angular speed.
If we take an ordinary manual gearbox, we will see three shafts in its composition:
- primary or leading - connects the gearbox to the flywheel through the clutch;
- secondary - rigidly connected to the cardan, it is it that is designed to transfer the torque to the cardan, and from it already to the drive wheels;
- intermediate - transfers rotation from the primary shaft to the secondary.
The purpose of the driveline
Any driver who drove a rear-wheel drive or all-wheel drive car, and even more so on a GAZon or ZIL-130, saw a cardan shaft - a long hollow pipe consisting of two segments - a longer and a shorter one, they are connected to each other by an intermediate support and a cross, forming hinge. In the front and rear of the cardan, you can see flanges for a rigid connection with the rear axle and the output shaft coming out of the gearbox.
The main task of the cardan is not only to transfer rotation from the gearbox to the rear axle gearbox, but also to ensure that this work is transmitted with variable alignment of the articulated units, or, in simple articulate language, a rigid connection of the drive wheels with the output shaft of the gearbox is provided , while not hindering the independent movement of the wheels and suspension relative to the body.
Also, the device of the car is such, especially when it comes to trucks, that the box is located higher in relation to the surface than the rear axle gearbox. Accordingly, it is necessary to transmit the moment of movement at a certain angle, and thanks to the articulated device of the cardan, this is quite possible. Moreover, while driving, the car frame can be slightly deformed - literally by millimeters, but the cardan device allows you to ignore these minor changes.
It is also worth saying that the cardan gear is used not only in all-wheel drive and rear-wheel drive cars, it is also installed on front-wheel drive ones. True, here it is called differently - SHRUS - hinges of equal angular velocities. CV joints connect the gearbox differential to the front wheel hubs.
Generally speaking, the principle of cardan transmission is used for other purposes:
- lower and upper cardan steering;
- for connecting the junction box with the drive axle gearbox - on off-road vehicles with a plug-in all-wheel drive, such as UAZ-469;
- for engine power take-off - the power take-off shaft coming from the tractor gearbox is used to set in motion various agricultural equipment through a cardan, for example, potato diggers or planters, disc harrows, seeders, and so on.
Устройство
As already mentioned above, the cardan shaft consists of two hollow pipes articulated with a swivel joint. In the front part there is a spline roller that engages with the gearbox output shaft by means of an adapter.
At the junction of the two parts of the cardan, each of them has a fork, and they are interconnected using a cross. Each end of the cross has a needle bearing. Forks are put on these bearings and thanks to them, the transfer of rotation is possible from one shaft to another when an angle is formed from 15 to 35 degrees, depending on the device. Well, in the back, the cardan is screwed to the gearbox using a flange, which is mounted on four bolts.
An important role is played by the intermediate support, inside which there is a ball bearing. The support is screwed to the bottom of the car, and the bearing allows the shaft to rotate freely.
As we can see, the device is quite simple, based on the hinge principle. However, engineers need to make precise calculations so that all suspension elements work in a balanced and coordinated manner.
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