Do you know the basic parameters of gears?

　　Gear refers to a mechanical element with gears on the rim that continuously meshes to transmit movement and power.Gears are used in many machines, but all machines that need to run are likely to have gears. Many people don't know the knowledge of gears. Do you know the basic parameters of gears?

　　Modulus z: The index circle of the gear is the basis for designing and calculating the size of each part of the gear, and the circumference of the gear index circle=πd=zp, so the diameter of the index circle d=zp/π, because in the above formula π is an irrational number, which is not convenient for the positioning of the index circle as a reference.In order to facilitate calculation, manufacturing and inspection, the ratio p/π is now artificially specified as some simple numerical value, and this ratio is called a module, expressed in m, that is, let its unit be mm.Therefore, the modulus m is a basic parameter that determines the size of the gear.A gear with the same number of teeth has a larger module, and its size is also larger.In order to facilitate manufacturing, inspection and interchangeability, the modulus value of the gear has been standardized.

　　Diameter of the index circle d: A circle must be specified as the reference circle for the size calculation in the gear calculation. Definition: The diameter is the circle of the product of the modulus multiplied by the number of teeth.Actually, it does not exist in the gear, it is just a circle by definition.Its diameter and radius are represented by d and r respectively, and the value is only related to the product of the modulus and the number of teeth, and the modulus is the end face modulus.It has nothing to do with the displacement coefficient.

　　In the standard gear, the circle where the groove width and the tooth thickness are equal (without considering the side clearance) is the index circle.The standard gear transmission coincides with the pitch circle.However, if it is a shifted gear, the tooth space and tooth thickness on the index circle will no longer be equal.If it is a shift gear drive, the index circle of the high shift gear drive still coincides with the pitch circle.However, the angular displacement gear drive separates the index circle from the pitch circle.

　　Pressure angle α-at the tangent point P of the two gear pitch circles, the common normal line of the two tooth profile curves (ie the force direction of the tooth profile) and the common tangent line of the two pitch circles (ie the instantaneous direction of movement at point P) The acute angle of the clamp is called the pressure angle, also called the engagement angle.For a single gear, it is the tooth profile angle.The pressure angle of a standard gear is generally 20".

　　Gears with small pressure angles have a smaller load-carrying capacity; while gears with large pressure angles have higher load-bearing capacity, the load on the bearing increases when the transmission torque is the same, so it is only used in special cases.