1. Field of Invention
The present invention relates to the backlash between two gears engaged with each other and, more particularly, to an apparatus and method for measuring the backlash between two gears engaged with each other.
2. Related Prior Art
A gear reducer includes gears engaged with one another between an input end and an output end. The gears can be arranged as a planetary gear train for example. The gears are made with various numbers of teeth. A high speed at the input end is converted to a low speed at the output end. The ratio of the speed at the output end over the speed at the input end is the gear ratio of the gear reducer. There is a clearance between any two gears engaged with each other and this gap is referred to as the “backlash.” The backlash reflects the precision of the gears and is an important parameter considered in the quality control over the gears.
The backlash of the gears of a gear reducer is measured manually most of the time. The gear reducer is held in position on a table by a clamp before the backlash is measured manually with a measuring instrument.
The measuring instrument can be a micrometer that includes a circular scale and an indicator. The unit used in the circular scale is 1° that is too large for precise measurement. Moreover, the observation of the indicator against the circular scale is vulnerable to errors.
The measuring instrument can be a photosensitive coupling device (or “charge-coupled device”, abbreviated as “CCD”) that detects light and converts images to digital signals. However, the detection of light is vulnerable to errors. Hence, the precision of measurement is often low.
Taiwanese Patent Application Publication No. 201541064 discloses a method and apparatus for measuring a gear reducer. The apparatus includes a worktable 11, a positioning unit, a rotating unit 3 an operation interface 17. A gear reducer 2 is inserted in a cavity 12 made in the worktable 11. A clamp 13 is used for holding the gear reducer 2 in the cavity 12. Under the control of the operation interface 17, the positioning unit is connected to a first axle 22 of the gear reducer 2 to prevent the first axle 22 from rotation, and the rotating unit 3 is connected to a second axle 22 of the gear reducer 2 to spin the second axle 22 before the backlash of the gear reducer is measured. The measurement of backlash is however not precise because the first axle 22 is prevented from rotation by the positioning unit. Moreover, the teeth of the gears of the gear reducer are vulnerable to breakage.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.