Rotary shaft assembly with nested shaft

1. A rotary shaft assembly for a door, the rotary shaft assembly, together with the door, disposed in a fluid passage through which a fluid flows, the rotary shaft assembly comprising:

an outer shaft defining a first passage therein; and

a nested shaft defining a second passage therein, located inside the outer shaft, and rotatably supported within the first passage of the outer shaft, wherein

the outer shaft has an outer opening formed on a circumferential wall of the outer shaft,

the nested shaft has:

a nested opening formed on a circumferential wall of the nested shaft; and

an open end at one longitudinal side of the nested shaft along a longitudinal direction of the nested shaft,

the nested shaft and the outer shaft are configure to be rotatable with respect to each other about a common axis such that a relative rotation angle between the outer shaft and the nested shaft varies between a first angle and a second angle,

when the relative rotation angle is the first angle, (i) the nested opening overlaps with the outer opening and takes the fluid into the second passage from the fluid passage through the outer opening and (ii) the open end discharges the fluid from the second passage, and

when the relative rotation angle is the second angle, the outer opening and the nested opening are offset from each other and block a flow of the fluid from the fluid passage to the second passage.

2. The rotary shaft assembly of claim 1 , further comprising:

an actuator configured to vary the relative rotation angle between the outer shaft and the nested shaft.

3. The rotary shaft assembly of claim 2 , wherein

the actuator is coupled to the outer shaft and is configured to rotate the outer shaft.

4. The rotary shaft assembly of claim 2 , wherein

the actuator is coupled to the nested shaft and is configured to rotate the nested shaft.

5. The rotary shaft assembly of claim 1 , wherein

the nested shaft includes another open end at another longitudinal side of the nested shaft along the longitudinal direction, and

when the relative rotation angle is the first angle, each of the open end and the other open end discharges the fluid from the second passage.

6. The rotary shaft assembly of claim 1 , wherein

an outer engagement portion is disposed on the circumferential wall of the outer shaft,

a nested engagement portion is disposed on the circumferential wall of the nested shaft, and

the outer engagement portion and the nested engagement portion are configured to be engaged to an actuator.

7. An HVAC system for a vehicle, comprising:

a blower configured to blow air in an airflow direction;

an evaporator disposed downstream of the blower in the airflow direction;

a heater disposed downstream of the evaporator in the airflow direction; and

the rotary shaft assembly of claim 1 , wherein

the fluid passage is defined in the HVAC system and allows the air, as the fluid, to flow therethrough, and

the rotary shaft assembly is coupled with the door and moves the door to change the airflow direction.

8. The HVAC system of claim 7 , wherein

the door is a slide door coupled to gear teeth disposed about the rotary shaft assembly.

9. The HVAC system of claim 7 , wherein

the door is a rotary door directly attached to the rotary shaft assembly.

10. The rotary shaft assembly of claim 1 , wherein

the fluid passage is defined in an HVAC system for a vehicle and allows air, as the fluid, to flow therethrough,

the door is located in the fluid passage and change an airflow direction of the air, and

when the relative rotation angle is the first angle, (i) the nested shaft takes the air into the second passage through the outer opening and the nested opening and (ii) the open end discharges the air from the second passage to an outside of the HVAC system.