What Is a Pressure Angle?

The pressure angle refers to the acute angle between the direction of the force and the direction of movement without calculating friction. As shown in the figure, is the acute angle between the force F acting on point C and the speed direction of point C, then the angle is the pressure angle when the plane mechanism is driven, that is, the angle between F and F _t The pressure angle is an important index for judging the dynamic performance of the mechanism.

The pressure angle is the angle between the direction line of the driving force received by the follower and the speed direction line of the force acting point without considering the influence of the friction force in each kinematic pair and the gravity and inertial force of the component. It is an important index for judging transmission performance. The pressure angle is mostly expressed by , which is more common in the planar link mechanism and the gear transmission mechanism.

Pressure angle in a planar linkage

in

Whether in plane transmission or gear transmission, the pressure angle can be used as a criterion for judging the force transmission performance of the transmission mechanism. The smaller the pressure angle, the greater the force component in the speed direction, that is, the greater the transmission force, the more the mechanism The better the transmission performance. The larger the pressure angle, the smaller the actual useful work. It can only increase the friction torque, but it is inevitable. In mechanical design, the pressure angle is constantly changing during the operation of the mechanism, so the maximum pressure angle is generally not more than 50 degrees. When the pressure angle is close to 90 degrees, the mechanism will self-lock and cannot operate.