# Pattern Classification and Gear Design of Spatial Noncircular
## 3 Principle and Classification Design of Spatial Noncircular Gear CVT  
### Principle of Each CVT Pattern  
The principles of the five CVT patterns are described in detail later. The phase switching mechanism and transmission selection mechanism are applicable to the five patterns, so only class A was taken as an example to explain them. (1) Class A: NG-PBGT  
Figure 3 shows the transmission principle of class A. This mechanism includes four parts. The first part is the phase switching mechanism, which is composed of a rotating end, a fixed end, an outer shaft, and an inner shaft. The outer shaft is connected with the fixed end and the noncircular gear 1 at the same time, and the inner shaft is connected with the rotating end and the noncircular gears 3 at the same time. Step 1, by rotating the rotating end, there is a required phase angle between noncircular gears 1 and 3. Step 2, connect the rotating end with the fixed end to synchronize the rotation speed of noncircular gears 1 and 3. In steps 1 and 2, the phase angle was switched. The second part is the noncircular gear pair, which is responsible for generating the required variable transmission ratio. The third part is the differential mechanism, which is composed of a planetary level gear train. It is responsible for integrating the variable transmission ratios of the driven noncircular gears 2 and 4 to achieve a constant speed output within a certain range of input rotation angle. The fourth part is the transmission selection mechanism, which is composed of a clutch and a ring gear. The outer ring of the clutch is connected to the inside of the ring gear, and the outside of the ring gear is connected to the output end. The clutch only transmits one-way rotational motion. When the inner ring of the clutch rotates in one direction, the roller was driven to roll to the narrow side of the wedge groove to be clamped with the outer ring of the clutch, thereby  
Figure 3: Transmission principle of class A.  
driving the outer ring of the clutch to rotate. When the inner ring of the clutch rotates in reverse, the roller rolls to the wide edge of the wedge groove and is in a relaxed state with the outer ring of the clutch, resulting in the outer ring of the clutch not rotating. This branch does not transfer rotation at this time. By integrating the transmission ratios of multiple branches, the constant speed output with the input rotation angle in the range of 0 to 360\({}^{\circ}\) was realized. The CVT can be realized by continuously changing the phase angle. In brief, the rotation speed transmission process of class A is as follows. Step 1, the input rotation speed was transmitted to the noncircular gears 1 and 3 with a certain phase angle. Step 2, the planetary bevel gear train composed of the bevel gears 5, 6, and 7 integrated the variable rotation speeds of noncircular gears 2 and 4. Step 3, the bevel gear 7 outputted a constant rotation speed within a certain input rotation angle. The planet carrier \(H\) is connected to the noncircular gear 2, and the bevel gear 5 is connected to the noncircular gear 4. (2) Class B: NG-PCGT  
Figure 4 is the transmission principle of class B, and the transmission process is as follows. Step 1, the input rotation speed was transmitted to the noncircular gears 1 and 3 with a certain phase angle. Step 2, the planetary cylindrical gear train composed of the ring gear 5, planetary gear 6, and center gear 7 integrated the variable rotation speeds of noncircular gears 2 and 4. Step 3, the planetary carrier \(H\) outputted a constant rotation speed within a certain input rotation angle. The ring gear 5 is connected to the noncircular gear 4, and the center gear 7 is connected to the noncircular gear 2. (3) Class C: CFG-BG-PCGT  
Figure 5 is the transmission principle of class C. The transmission process is as follows. Step 1, the input rotation speed was transmitted to the curve face gears 1 and 3 with a certain phase angle.