System and method for operating a lubrication system with mechanical control

1 . A lubrication system for a vehicle, comprising:

a heat exchanger having an inlet and an outlet;

a gearbox lubrication circuit fluidly connecting a gearbox between the inlet and the outlet of the heat exchanger;

a stator lubrication circuit fluidly connecting a stator between the inlet and the outlet of the heat exchanger;

a rotor lubrication circuit fluidly connecting a rotor between the inlet and the outlet of the heat exchanger, wherein the rotor lubrication circuit includes a rotor circuit mechanical valve located upstream of an inlet to the rotor and downstream of the outlet of the heat exchanger and the rotor circuit mechanical valve is configured to move from a closed position to an open position when a pressure immediately upstream of the rotor circuit mechanical valve reaches a rotor circuit mechanical valve cracking pressure; and

a heat exchanger bypass passage configured to bypass the inlet to the heat exchanger and connect with the rotor lubrication circuit downstream of the outlet of the heat exchanger, wherein the heat exchanger bypass passage includes a bypass mechanical valve upstream of the rotor circuit mechanical valve and the bypass mechanical valve includes a cracking pressure to move from an open position to a closed position that is greater than the cracking pressure of the rotor circuit mechanical valve.

2 . The lubrication system of claim 1 , wherein the rotor circuit mechanical valve includes one of a spring actuated ball valve or a spring actuated pressure relief valve.

3 . The lubrication system of claim 1 , wherein the rotor circuit mechanical valve includes an off-axis ball valve configured to move from the closed position to an open position allowing lubricant to flow to the rotor when a pressure in the rotor lubrication circuit exceeds the rotor circuit mechanical valve cracking pressure.

4 . The lubrication system of claim 1 , wherein the rotor circuit mechanical valve includes an off-axis ball valve configured to move from an open position to a closed position when a centrifugal force on a ball in the off-axis ball valve caused by rotation of the rotor is greater than the pressure immediately upstream of the rotor circuit mechanical valve.

5 . The lubrication system of claim 1 , wherein the rotor lubrication circuit includes a floating ball valve upstream of the rotor circuit mechanical valve and the bypass connection.

6 . The lubrication system of claim 5 , wherein the floating ball valve includes a floating ball valve cracking pressure that is less than bypass closing pressure of the bypass mechanical valve.

7 . The lubrication system of claim 1 , wherein the gearbox lubrication circuit, the stator lubrication circuit, and the rotor lubrication circuit are connected fluidly in parallel with an auxiliary lubrication circuit between the outlet of the heat exchanger and a sump.

8 . The lubrication system of claim 1 , wherein the stator lubrication circuit includes a stator orifice having a stator lubrication circuit maximum flow rate, the gearbox lubrication circuit includes a gearbox orifice having a gearbox lubrication circuit maximum flow rate, and the rotor lubrication circuit includes a rotor orifice having a rotor lubrication circuit maximum flow rate.

9 . The lubrication system of claim 8 , wherein the rotor orifice is located downstream of the rotor circuit mechanical valve.

10 . The lubrication system of claim 1 , including an electrically driven pump having a variable output flowrate configured to direct lubricant from the gearbox lubrication circuit, the stator lubrication circuit, and the rotor lubrication circuit to an output of the electrically driven pump.

11 . A method of operating a lubrication system, the method comprising:

directing a lubricant from an outlet of a heat exchanger to a stator lubrication circuit;

directing the lubricant from the outlet of the heat exchanger to a gearbox lubrication circuit;

selectively directing the lubricant to a rotor lubrication circuit, wherein the rotor lubrication circuit includes a rotor circuit mechanical valve upstream of a rotor and is configured to block a flow of the lubricant to the rotor when a pressure of the lubricant immediately upstream of the rotor circuit mechanical valve is less than a cracking pressure of the rotor circuit mechanical valve and the rotor circuit mechanical valve is configured open when the pressure of the lubricant immediately upstream of the rotor circuit mechanical valve is greater than the cracking pressure of the rotor circuit mechanical valve; and

bypassing lubricant around the heat exchanger with a heat exchanger bypass passage forming a connection to the rotor lubrication circuit, wherein the heat exchanger bypass passage includes a bypass mechanical valve located upstream of the rotor circuit mechanical valve and the bypass mechanical valve includes a cracking pressure to move from an open position to a closed position that is greater than the cracking pressure of the rotor circuit mechanical valve.

12 . The method of claim 11 , including directing the lubricant through the lubrication system with an electrically driven pump having variable output flowrate.

13 . The method of claim 11 , including opening a floating ball valve located downstream of an outlet of the heat exchanger and upstream of the connection with the heat exchanger bypass passage at the cracking pressure of the bypass mechanical valve.

14 . The method of claim 11 , wherein the rotor circuit mechanical valve includes one of a spring actuated ball valve or a spring actuated pressure relief valve.

15 . The method of claim 11 , wherein the rotor circuit mechanical valve includes an off-axis ball valve configured to move from the closed position to an open position allowing lubricant to flow to the rotor when a pressure in the rotor lubrication circuit exceeds the rotor circuit mechanical valve cracking pressure.

16 . A vehicle comprising:

a passenger compartment;

a plurality of wheels supporting the passenger compartment;

a traction motor having a rotor and a stator with the rotor configured to drive at least one of the plurality of wheels through a gearbox; and

a lubrication system including:

a heat exchanger having an inlet and an outlet;

a gearbox lubrication circuit fluidly connecting a gearbox between the inlet and the outlet of the heat exchanger;

a stator lubrication circuit fluidly connecting a stator between the inlet and the outlet of the heat exchanger;

a rotor lubrication circuit fluidly connecting a rotor between the inlet and the outlet of the heat exchanger, wherein the rotor lubrication circuit includes a rotor circuit mechanical valve located upstream of an inlet to the rotor and downstream of the outlet of the heat exchanger and the rotor circuit mechanical valve is configured to move from a closed position to an open position when a pressure immediately upstream of the rotor circuit mechanical valve reaches a rotor circuit mechanical valve cracking pressure; and

a heat exchanger bypass passage configured to bypass the inlet to the heat exchanger and connect with the rotor lubrication circuit downstream of the outlet of the heat exchanger, wherein the heat exchanger bypass passage includes a bypass mechanical valve upstream of the rotor circuit mechanical valve and the bypass mechanical valve includes a cracking pressure to move from an open position to a closed position that is greater than the cracking pressure of the rotor circuit mechanical valve.

17 . The vehicle of claim 16 , wherein the rotor circuit mechanical valve includes an off-axis ball valve configured to move from the closed position to an open position allowing lubricant to flow to the rotor when a pressure in the rotor lubrication circuit exceeds the rotor circuit mechanical valve cracking pressure.

18 . The vehicle of claim 16 , wherein the rotor lubrication circuit includes a floating ball valve upstream of the rotor circuit mechanical valve and the bypass connection and the floating ball valve includes a floating ball valve cracking pressure that is less than a bypass closing pressure of the bypass mechanical valve.

19 . The vehicle of claim 16 , wherein the gearbox lubrication circuit, the stator lubrication circuit, and the rotor lubrication circuit are connected fluidly in parallel with an auxiliary lubrication circuit between the outlet of the heat exchanger and a sump.

20 . The vehicle of claim 16 , wherein the stator lubrication circuit includes a stator orifice having a stator lubrication circuit maximum flow rate, the gearbox lubrication circuit includes a gearbox orifice having a gearbox lubrication circuit maximum flow rate, and the rotor lubrication circuit includes a rotor orifice having a rotor lubrication circuit maximum flow rate.