A system for lubricating transmission components with hydraulic fluid includes a pump and a motor coupled to the pump. The pump has an inlet port that receives hydraulic fluid and an outlet port from which hydraulic fluid is pumped to the transmission components. A pump pressure is regulated by adjusting a motor torque of the motor, and the motor torque is set by commands based on a look-up table or a formula.
1. A system for lubricating transmission components with hydraulic fluid comprising:
a pump with an inlet port that receives hydraulic fluid and an outlet port from which hydraulic fluid is pumped to the transmission components; and
a motor coupled to the pump, a controller that commands the operation of said pump and said motor, operation of said controller including a target pump pressure of the pump being regulated by a command motor torque, and the command motor torque being set by varying a pump speed determined from one of a series of 3-D look-up tables that characterizes the pump pressure, the command motor torque, and the pump speed as a function of temperature,
wherein a flow rate of the hydraulic fluid is based on the pump speed and a pump displacement, the pump pressure being determined from the flow rate and without the use of a pressure sensor, and wherein the pump pressure is provided as feedback to determine a desired pump speed.
2. The system of claim 1 wherein the pump speed is provided as feedback to determine a desired pump torque.
3. The system of claim 1 wherein the motor is coupled to the pump with a shaft.
4. The system of claim 1 wherein the motor includes a rotor that is an integrated component of the pump.
5. The system of claim 1 wherein the pump pressure is determined by the relationship
Δ
p
=
T
p
-
T
c
-
C
d
D
μ
n
1
+
C
f
·
2
π
D
where
T p =pump torque
T c =constant frictional torque
C d =coefficient of viscous drag
C f =coefficient of friction
D=pump displacement
μ=fluid viscosity
Δp=pump pressure rise
n=pump speed.
6. A method for providing hydraulic fluid to components of a transmission, the method comprising:
a first step of regulating a pressure in a pump, the pump being in communication with the components to pump the hydraulic fluid to the components;
a second step of adjusting a torque of a motor coupled to the pump to regulate the pump pressure, wherein the motor torque is set by commands based on a look-up table; wherein inputs to the look-up table are a pump speed and a target pressure and
a third step of adjusting the torque of the motor by a controller, wherein the torque is set by commands based on a formula wherein a flow rate of the hydraulic fluid is based on the pump speed and a pump displacement, the pump pressure being determined from the flow rate and without the use of a pressure sensor, and wherein the pump pressure is provided as feedback to determine a desired pump speed.
7. The method of claim 6 further comprising a fourth step of deciding whether to maintain a pump speed with the current torque level.
8. The method of claim 7 further comprising a fifth step of adjusting the pump speed.
9. The method of claim 8 wherein the pump pressure is provided as feedback and together with the torque command to adjust the pump speed.
10. The method of claim 8 wherein the pump speed is provided as feedback to the look-up table to adjust the pump torque.
11. The method of claim 8 wherein the pump speed is provided as feedback to the formula to adjust the pump torque.
12. The method of claim 6 wherein the pump pressure is determined by the relationship
Δ
p
=
T
p
-
T
c
-
C
d
D
μ
n
1
+
C
f
·
2
π
D
where
T p =pump torque
T c =constant frictional torque
C d =coefficient of viscous drag
C f =coefficient of friction
D=pump displacement
μ=fluid viscosity
Δp=pump pressure rise
n=pump speed.