EA036872B1 - Friction connection of drive shaft and pulley - Google Patents

Abstract

The invention relates to machine building, in particular to connection of mutually rotating parts. Frictional connection of a drive shaft with a pulley includes a bushing in the form of a compressed cylindrical spring with a zero distance between coils, the spring arranged between surfaces of the shaft and the pulley opening, a thrust washer, a dish washer and a nut.

Description

State of the art

It is known the frictional connection of a jointly rotating drive shaft and a pulley using a cylindrical bushing having an internal axial cylindrical hole that allows this element to be put on the drive shaft with an interference fit and in the same way to fix the pulley (see, for example, the book by D.N. Reshetov Machine Details, p. 81 and further M .: Mechanical Engineering, 1989). The disadvantages of such a connection include the technological complexity of its implementation.

A friction joint is known in the form of a hollow cylinder and an impeller placed in it with a granular or powdery substance between the blades, and the blades are made rotatable in one direction from the radial position on axes parallel to the axis of the cylinder, so that the connection can work only when rotating in one direction (see. ed.St SU 25138 IPC F16D 37/00, 1932). The disadvantage of such a connection is low reliability in case of short-term torque overloads due to the loss of the bearing capacity of the connection.

Known friction connection of a drive shaft with a pulley, including a tapered bushing cut along a guide with an internal axial cylindrical hole allowing this element to be put on the drive shaft and with an outer tapered wall on which the pulley is put on with fixing bolts fixing its position. See, for example, (http://www.skf.com/portal/skf ru / home / products? Maincatalogue = l & lang = ru & newlink = 1162), or motionproducts.ru> upload / iblock / fad / .... pdf. To place the tapered bushing between the surfaces of the drive shaft and the pulley bore, it is necessary to make the bore of the pulley corresponding to the tapered bushing, which complicates its manufacture.

Disclosure of invention

The technical result that can be achieved with the help of the present invention is reduced to increasing the efficiency of connecting the shaft to the pulley.

The technical result is achieved using a frictional connection of the drive shaft with a pulley, including a bushing made in the form of a compressed cylindrical spring with a zero distance between the turns, placed between the surfaces of the shaft and the pulley hole, a thrust washer, a washer and a nut, and the length of the spring exceeds the length of the shaft contact and a pulley in the range of 0.25-0.5 of the coil thickness, the inner diameter of the spring being equal to the diameter of the drive shaft, and the outer one equal to the diameter of the pulley bore.

The frictional connection of the drive shaft with the pulley works, as is known, due to the frictional forces organized between the surface of the shaft and the surface of the hole of the pulley put on it. Usually, an intermediate element is installed between these two surfaces - the bushing and friction forces are organized between the surfaces of the bushing, shaft and pulley. In the proposed invention, it is proposed to use a coil spring with zero distance between the turns as such an intermediate element. The inner diameter of the spring is equal to the diameter of the drive shaft, and the outer diameter of the spring is equal to the diameter of the pulley bore. The spring can be screwed onto the shaft until it stops and the pulley can be screwed onto it from the outside until the same stop.

In this case, the length of the spring should be slightly greater than the length of the shaft section interacting with the pulley. Longitudinal compression of the spring leads to the elimination of gaps between the coils and the occurrence of force contact between the coils of the spring along the spiral line of their contact. In this case, contact stresses of local compression arise in the coils of the spring, which leads to deformation of the cross section of the coils, when the initially circular cross section of the coil tends to transform into an elliptical section due to the compression forces. Thus, the pressure of the spring coils appears on the one hand on the drive shaft, and on the other, on the surface of the hole in the pulley, which leads to the appearance of friction forces. Thus, the greater the compression of the spring, the greater the deformation of the cross-sections of the spring coils and, accordingly, the increase in friction forces connecting the drive shaft and the pulley into a single system. Longitudinal compression of the spring can be done through the Belleville washer by tightening the nut on the drive axle or otherwise. It should also be noted that the installation of the spring must be consistent with the direction of rotation of the shaft, meaning the direction of twisting of the coils of the spring, so that when the shaft rotates, inertial twisting of the spring occurs, which will increase the magnitude of contact stresses and, accordingly, the friction force. Taking into account possible imperfections in the manufacture of the spring, we believe that the length of the spring should exceed the contact length in the interval 0.25-0.5 of the coil thickness.

The resulting value of the frictional torque can be determined empirically as a result of tests or theoretically by solving the contact problem of the theory of elasticity, taking into account the physical and mechanical properties of the structural materials used.

Brief Description of Drawings

FIG. 1 shows a diagram of a frictional connection.

FIG. 2 shows a diagram of the deformation of the section of the sleeve.

- 1 036872

Implementation of the invention

The frictional connection of the drive shaft 1 with the pulley 2 includes a sleeve 3, made in the form of a compressed cylindrical spring with a zero distance between the turns, located between the surfaces of the shaft 1 and the hole of the pulley 2 with zero clearance, a thrust washer 4, a washer 5 and a nut 6.

The connection is carried out as follows. A thrust washer 4 is installed on the drive shaft 1 and a sleeve 3 is put on (screwed on), the length of which exceeds the length of the contact between the shaft and the pulley in the range 0.25-0.5 of the coil thickness, and the inner diameter of the spring is equal to the diameter of the drive shaft 1, and the outer one is equal to the diameter pulley holes 2. Pulley 2 and Belleville washer are installed in the same way on sleeve 3. By tightening nut 6 with a torque wrench, sleeve 3 is compressed and the initially circular cross-section of the loop 7 is deformed to an elliptical shape 8, accompanied by pressure of the loops on the mating surfaces with the appearance of the required forces friction, ensuring the joint rotation of the shaft 1 and the pulley 2. The required amount of torque when compressed by the nut 6 of the sleeve 3 can be determined empirically. For inertial twisting, the installation of the sleeve 3 is consistent with the direction of rotation of the shaft, that is, the direction of twisting of the sleeve made in the form of a compressed cylindrical spring with a zero distance between the turns, and the rotation of the shaft must be opposite.

The proposed invention in comparison with other known technical solutions has the following advantages:

increases the efficiency of connecting the shaft to the pulley;

provides the ability to quickly disassemble the connection.

Claims (1)

CLAIM Frictional connection of the drive shaft with a pulley, including a bushing made in the form of a compressed cylindrical spring with a zero distance between the turns, placed between the surfaces of the shaft and the pulley hole, a thrust washer, a washer and a nut, characterized in that the length of the spring exceeds the length of the contact between the shaft and the pulley in the range of 0.25-0.5 of the coil thickness, the inner diameter of the spring being equal to the diameter of the drive shaft, and the outer one being equal to the diameter of the pulley bore.