Automatic transmission valve ports

Valve bodies of automatic transmissions are complex parts with multiple cylindrical valve ports. Examples of vale body components are shown in Figure 1.

(a) (b)

Figures 1. Component of valve body of an automatic transmission

(a) top, (b) bottom

The valve ports in these valve bodies range in diameter from about 5 mm to 25 mm and in length from about 20 to over 100 mm. The diameter of a valve port can change in discrete increments along its length and the valve ports are intersected by multiple slots that segment each valve port into short cylindrical segments or journals. The journal surfaces are diamond turned and are highly reflective. Defects in the valve ports can consist of pores, chatter, delamination, metal flakes and other machining defects.

Graphs of valve port surface finish display circumferential angles from 0 to 360 degrees along one axis, depth into the cylinder in mm along the second horizontal axis and relative detected laser intensity along the vertical axis. Examples of these graphs are shown below. Figure 2 shows a valve port with acceptable surface finish, Figure 3 shows a valve port with excessive porosity and Figure 4 shows a valve port with both chatter and porosity. The signal intensity values are inverted to emphasize the defects,

Figure 2. Acceptable surface finish

Figure 3. Excessive porosity

Figure 4. Example of chatter

These graphs are three dimensional and can be rotated by the observer to obtain the best view of the component surface finish.