1. Development and application of wedge overrunning clutch

Overrunning clutch is one of the basic components of mechanical transmission. It is a kind of clutch with self clutch function by using the speed change or rotation direction change of driving and driven parts. It is widely used. Roller type overrunning clutch has a long history. According to literature reports, it was loaded into German drp2804 with the title of "reversing motor" in 1878 In the 47h5 patent, it is used on the reversing mechanism. In the following hundred years, the roller overrunning clutch has been continuously developed and improved, the structural types have increased, and the application is also more common.

Wedge overrunning clutch is a new type of clutch developed after roller overrunning clutch. Since its inception, it has been widely used in mechanical transmission with large bearing capacity, reliable self-locking, light reverse release, compact structure and convenient operation. First of all, the United States has been developed, popularized and applied in automobiles and aircraft. For example, the United States uses it on Boeing 707 aircraft, f4-c bombers and m102-105 light howitzers. It has also been widely used in Japan and Germany.

In recent years, with the development of new products and the need of localization of imported products, the wedge overrunning clutch has developed rapidly, and its structure, performance and reliability are becoming more and more perfect. Moreover, the type and specification of the clutch are more complete, and the product quality is gradually improved. The wedge overrunning clutch produced by Luoyang best precision machinery manufacturing Co., Ltd. can not only meet the needs of domestic scientific research and production, but also replace the overrunning clutch introduced from corrugated paper production lines and oxygen free copper production lines in Japan, the United States, Italy and other countries, with good application effect.

The wedge overrunning clutch is often matched with the ball screw pair or other components. As an anti reversal mechanism, it can also be used alone. It is used as a clutch with self clutch function for accurate positioning between the driving shaft and the driven shaft, transmitting torque or cutting off torque. Therefore, it is called backstop or one-way bearing. It is widely used in packaging machinery, printing machinery, food machinery, light industrial machinery, agricultural machinery, metallurgy and mining, petrochemical industry, machine tools, automobiles, weapons, aviation, power stations and other mechanical equipment.

2. Characteristics of wedge overrunning clutch

Wedge overrunning clutch is to place wedge tightening elements (wedges) between the inner ring and the outer ring (raceway), so that when it rotates, it can transmit torque in one and has relative idling performance in the other. Only when the inner and outer rings turn in the same direction and rotate at the same speed can the torque be transmitted, otherwise it is relative sliding. This sliding state without transmitting torque is called transcendence.

1) The shape of the raceway there are two types of raceway for the wedge overrunning clutch: the raceways of the inner and outer rings are round and the inner ring is processed into several concave grooves.

(1) The inner ring is round. The inner and outer rings of the clutch are smooth cylindrical surfaces. In order to ensure no slip during operation, the wedge angle of the wedge shall not exceed the * * * small friction angle between the wedge and the inner and outer rings. In design, generally 3 ° - 4 ° can be taken. In practice, when the wedge angle starts, the wedge angle is about 2 ° - 2.5 °. When the inner and outer rings are subjected to elastic deformation, the wedge angle increases accordingly.

(2) The inner ring has a concave circular groove. The wedge has the same radius as the inner ring circular arc groove, so that they are in surface contact, which improves the stress state and improves the bearing capacity and service life of the wedge. However, the number of wedges is reduced due to the influence of structure.

2) The shape of the wedge block the shape of the wedge block used in the overrunning clutch is mostly special-shaped, such as fist shape, shoe shape, etc. when designing the clutch, different shapes of wedge blocks can be selected according to the function requirements.

3) Wedge and roller overrunning clutches have their own characteristics due to the different wedge tightening elements placed between the inner and outer rings.

3. Selection and calculation of wedge overrunning clutch

In order to ensure the reliable operation of the clutch, the comprehensive function of the clutch in the transmission system is usually defined when designing and selecting the clutch, and the variety and type of the clutch are selected from the overall design of the transmission system. The selection of specifications is mainly based on the calculated torque.

1) The main parameter of the clutch is the nominal torque. When selecting the clutch, the transmission torque shall comply with the following relationship: T

2) Clutch calculation torque the clutch calculation torque is calculated according to the power, working speed, reserve coefficient and related factors of the transmission system. Tc= β Where Tc - calculated torque, n · m; β— Reserve coefficient (generally 1.2-3.2); T - Theoretical torque, n · M. Reserve coefficient β  The value is related to the performance of prime mover and working machine, the structural type of clutch and other factors. Generally, the working conditions are good and the load is light, β  The value is taken as the small value; Poor working conditions and heavy load, β  Value takes the larger value.

4. Structure form and application scope of wedge overrunning clutch

The wedge overrunning clutch can be divided into contact type, non-contact type and two-way type according to the standard of gb10043-1988 clutch classification. The first two types are actually one-way type. Table 2 lists the structural forms and application scope of various types of wedge overrunning clutches.