# Basic knowledge of gear (2)

1. What is a standard gear?

Answer: m, α, h * a, c * are standard values, and S = e = P / 2.

1. What are the characteristics of the rack?

Answer: (1) each straight-line circle section parallel to the tooth top line is equal, its modulus and pressure angle are all standard values.

(2) The straight line with the width equal to the tooth thickness of the parallel tooth top line is called the center line, which is the reference line to determine the rack size.

1. What is theoretical meshing line, actual meshing line and tooth profile working section?

Answer: theoretical meshing line: the internal common tangent line on the same side of the two base circles, theoretically the locus of the meshing points of the tooth profile, two tangent points

Is the engagement limit point.

Actual meshing line: the line segment between the intersection of the top circle of two teeth and the theoretical meshing line.

Working section of tooth profile: the part of tooth profile engaged in gear transmission.

L4. What are the correct Meshing Conditions and continuous meshing transmission conditions of involute spur gears?

Answer: correct engagement condition: M1 = M2 = m α 1 = α 2 = α

Conditions for continuous meshing: ε α = b1b2 / Pb ≥ 1

1. What is the essence of coincidence degree? What is the degree of coincidence related to?

Answer: the magnitude of coincidence indicates the logarithm of meshing on the meshing line at the same time during the transmission of a pair of gears. The magnitude of coincidence degree is an important index of the bearing capacity and the stability of gears. The magnitude of coincidence degree has nothing to do with M. it increases with the increase of Z1 and Z2. The larger α′, the smaller ε α. The larger α′, the larger α′, the smaller ε α.

1. What is the standard installation center distance of standard gear. What are the features of standard installation?

Answer: the center distance of the standard gear installed according to the non tooth side clearance is called the standard installation center distance of the standard gear, and the center distance of the standard gear installed according to the standard top clearance is also called the standard installation center distance.

In standard installation, a = a ′, r = R ′, a = R1 + R2

1. What is non-standard installation center distance? What are the features of non-standard installation?

Answer: a pair of meshing transmission gears, the installation of which pitch circle does not coincide with graduation circle is called non-standard installation, and the center distance is called non-standard installation center distance.

Characteristic R ≠ R ′, a ≠ a ′, a ′ = R1 ′ + R ′ 2 = (R1 + R2) cos α / cos α′, i.e., a ′≠ a α ′ ≠ α R1 ′ ≠ R1 R2 ′ ≠ R2 C ≠ C

There is tooth side clearance, resulting in impact, the degree of coincidence decreases, and the stability is poor.

1. What are the characteristics of gear rack meshing transmission?

Answer: (1) the position of the meshing line does not change due to the change of the relative position between the gear and the rack. It is always a fixed line tangent to the base circle and perpendicular to the linear profile of the rack.

(2) R = R ′ α′ = α = rack angle

1. What are the characteristics of standard rack and pinion machining?

Answer: the graduation circle of the wheel blank is tangent to the center line of the rack tool, and the number of teeth of the gear to be processed is determined by the moving speed of the tool and the angular speed of the wheel blank to ensure that V tool = R ω.

1. What is undercutting phenomenon of involute profile? What is the reason?

Answer: the phenomenon of undercutting is called undercutting when the finished involute profile is cut off by generating method.

Cause: the intersection of the tooth top line and the meshing line of the cutter exceeds the meshing limit point of the gear to be cut, and the tooth top line of the cutter exceeds

The reason of over meshing limit point is that the number of teeth is too small, the pressure angle is too small, and the coefficient of tooth top height is too large.

Scroll to Top