Single error detection of automobile gear parts

1. Diameter jump of ring gear

The diameter jump of the ring gear of the automobile gear is the value of the difference between the highest point and the lowest point of each tooth groove measured by the dial gauge when the gear rotates along the central axis. It contains two kinds of eccentricity, one is ring gear swing, the other is end side runout.

Another common method to check the diameter jump of the ring gear is to use a dial indicator to measure the change of the radius of the tooth root circle in the rotating parts. This type of inspection requires simultaneous machining of the tooth root surface and tooth side. If the hob also processes the tooth top at the same time, the circular runout of the tooth top can also be detected instead of the radial runout of the ring gear.

2. Pitch error

The biggest difference between the pitch error of automobile gears is the accumulated error between any two consecutive adjacent teeth at the pitch circle position. Generally, the operation of automobile gears rotates along the driving direction, and the deviation in one direction can be detected. If the automobile gears require forward rotation and reverse rotation, they must be inspected in both directions.

3. Total cumulative error

The cumulative error of automobile gear is the algebraic sum of the maximum cumulative error of circumferential pitch error. Unless otherwise specified, check the maximum error between any two teeth of all teeth whose accumulated error is 360 degrees of the whole part.

The measured circumferential pitch and cumulative error usually provide the most accurate results by optical means. Through this method, the relative error of tooth to tooth that deviates from the true pitch circle is determined. Therefore, the pitch circle and total cumulative deviation test results are obtained directly from the instrument without using the algebraic method shown above.

For low-speed gears and medium speed gears, the total accumulated error is usually not important, unless the gear is used for timing mechanism, and it is necessary to make accurate guidance for automotive gears and other products. Even under the best measurement environment, the determination of cumulative error is a time-consuming work. Usually, it is only used as a spot check to determine whether it meets the gear tolerance range.

4. Tooth profile error

The tooth profile error of automobile gear is the highest and lowest reading measured by the plane rotation of the side head of the dial indicator along the real involute curve and the contact tooth profile of automobile gear. All measurement results are in the same manufacturing plane, or transformed into a rotating plane. Involute measuring equipment can be used for tooth profile error inspection.

The tooth profile inspection must measure the effective (meshing) part of the tooth profile design. It is difficult to measure the tooth profile at the tooth root, but it is rarely necessary to check the root of the automobile gear because it exceeds the meshing part of the automobile gear. Tooth top modification, chamfer or other modification must also be considered within the measurement range of tooth profile deviation.

The actual tooth profile of an automobile gear can only be determined by the matching gear. If the paired gear parameters are available, the parameters of the driving gear can be calculated with the paired parameters.

5. Tooth direction error

The tooth direction error of helical gear is expressed as the unit circumferential tooth error of the whole surface width of automobile gear. It is possible to measure the maximum deviation of the tooth width position parallel to the rotating shaft through a pressure probe. The measurement result is the error of the transformation of the helix in the rotation plane of the part.

The term “spur gear” applies only to spur gears, not helical gears. In fact, for spur gears, the standard for evaluating tooth direction is the same as that for helical gears. The tolerance range is determined according to the standards of tooth width and accuracy grade.

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