REVERSIBLE COOLING FAN FOR VEHICLE AND METHOD FOR CONTROLLING DIRECTION OF ROTATION

1 . An apparatus for heating a passenger compartment of a vehicle, the vehicle having an engine room defining a ram airflow path, an engine located in the engine room, and a cooling pack located in the ram airflow path for dissipating waste heat generated by the engine, the apparatus comprising:

a heater configured to provide heated air to the passenger compartment, the heater in thermal communication with the engine to transfer waste heat from the engine to the passenger compartment;

a sensor configured to detect one or more operating conditions of the vehicle;

a fan positioned in the ram airflow path, the fan responsive to a control signal to operate in at least two modes relative to the ram airflow path; and

a controller responsive to the sensor and configured to generate the control signal to operate the fan in a first mode when the detected one or more operating conditions are in a first state and to operate the fan in a second mode when the detected one or more operating conditions are in a second state.

2 . The apparatus of claim 1 , wherein the first mode is the operation of the fan at a first speed and the second mode is the operation of the fan at a second speed.

3 . The apparatus of claim 2 , wherein the operating conditions include a passenger compartment heat demand and a heater heat capacity;

wherein the first state includes the heat capacity being greater than the heat demand by a threshold value; and

wherein the first speed is greater than the second speed.

4 . The apparatus of claim 1 , wherein the first mode is the operation of the fan in a forward direction in which the fan moves air in a direction of the ram airflow path, and the second mode is the operation of the fan in a reverse direction in which the fan moves air in an opposite direction of the ram airflow path.

5 . The apparatus of claim 4 , wherein the one or more operating conditions of the vehicle include a detected temperature of at least one of ambient air, the engine room, the heater, and the engine; and

wherein the first state includes the detected temperature being greater than a threshold temperature and the second state includes the detected temperature being less than or equal to the threshold temperature.

6 . The apparatus of claim 5 , wherein the threshold temperature is a predetermined constant.

7 . The apparatus of claim 5 , wherein the operating conditions include a passenger compartment heat demand; and

wherein the threshold temperature is computed based on heat demand.

8 . The apparatus of claim 1 , wherein the operating conditions include a heater heat capacity; and

wherein the first state includes the beat capacity being less than a threshold value.

9 . The apparatus of claim 8 , wherein the operating conditions further include a passenger compartment heat demand; and

wherein the threshold value is computed based on heat demand.

10 . The apparatus of claim 4 , wherein the fan is responsive to the control signal to operate at a plurality of speeds in at least one of the forward direction and reverse direction; and

wherein the controller is further configured to generate the control signal to operate the fan at a selected one of the plurality of speeds based on the detected operating conditions.

11 . The apparatus of claim 1 , wherein the operating conditions include a heater heat capacity and a passenger compartment heat demand; and

wherein the first state includes heat capacity being greater than heat demand by a threshold value, and the second state includes heat capacity being less than or equal to heat demand by the threshold value.

12 . The apparatus of claim 11 , wherein the threshold value is zero or greater.

13 . The apparatus of claim 4 , wherein the fan is positioned adjacent the cooling pack to reduce ram airflow over the cooling pack when the fan operates in the reverse direction.

14 . An apparatus for heating a passenger compartment of a vehicle, the vehicle having an engine room defining a ram airflow path and an engine located in the engine room, the apparatus comprising:

a sensor configured to detect one or more operating conditions of the vehicle;

a heater configured to provide heated air to the passenger compartment, the heater thermally coupled to the engine;

a cooling pack in the ram airflow path and thermally coupled to the engine, the cooling pack including at least one of a radiator and a condenser;

a fan positioned in the ram airflow path adjacent the cooling pack, the fan responsive to a control signal to operate in a forward direction in which the fan moves air in a direction of the ram airflow path, and a reverse direction in which the fan moves air in an opposite direction of the ram airflow path; and

a controller responsive to the sensor and configured to generate the control signal to operate the fan in the forward direction when the detected one or more operating conditions are in a first state, and to operate the fan in the reverse direction when the detected one or more operating conditions are in a second state.

15 . The apparatus of claim 14 , wherein the operating conditions include a detected temperature of at least one of ambient air, the engine room, the heater and the engine.

16 . The apparatus of claim 15 , wherein the first state includes the detected temperature being greater than a threshold temperature and the second state includes the detected temperature being less than or equal to the threshold temperature.

17 . The apparatus of claim 14 , wherein the operating conditions include a heater heat capacity; and

wherein the first state includes the heat capacity being less than a threshold value.

18 . The apparatus of claim 17 , wherein the threshold value is a predetermined constant.

19 . The apparatus of claim 17 , wherein the operating conditions further include a passenger compartment heat demand; and

wherein the threshold value is computed based on the heat demand.

20 . The apparatus of claim 14 , wherein the operating conditions include a heater heat capacity and a passenger compartment heat demand;

wherein the first state includes the heat capacity being greater than the heat demand; and

wherein the second state includes the heat capacity being less than or equal to the heat demand.

21 . A method for heating the passenger compartment of a vehicle having an engine room defining a ram airflow path, a fan located in the ram airflow path, an engine, and a heater configured to heat the passenger compartment using waste heat of the engine, the method comprising:

detecting one or more operating conditions of the vehicle including at least one of a passenger compartment heat demand and a heater heat capacity;

driving the fan in a forward direction when the detected operating conditions are in a first state;

driving the fan in a reverse direction when the detected operating conditions are in a second state.

22 . The method of claim 21 , wherein the first state includes the heat capacity being greater than the heat demand by a threshold value that is zero or greater.

23 . The method of claim 21 , further comprising:

turning the fan off when the detected operating conditions are in a third state.

24 . The method of claim 21 , further comprising:

driving the fan in a forward direction after the detected operating conditions have been in the second state for a predetermined amount of time.

25 . The method of claim 21 , further comprising varying a rotational speed of the fan based on the detected operating conditions.