BUS VOLTAGE STABILIZATION IN POWERTRAIN HAVING ELECTRIC STARTER SYSTEM WITH POLYPHASE BRUSHLESS STARTER MOTOR

• US 20190323472A1
• Filed: 04/24/2018
• Published: 10/24/2019
• Est. Priority Date: 04/24/2018
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Hao, Lei, Namuduri, Chandra S., Gopalakrishnan, Suresh
• Granted Patent: US 10,544,772 B2
• Time in Patent Office: Days
• CPC Class Codes: F02N 11/08 Circuits or control means specially adapted for starting of engines
• CPC Class Codes: F02N 11/0851 characterised by means for controlling the engagement or disengagement between engine and starter, e.g. meshing of pinion and engine gear
• CPC Class Codes: F02N 15/046 of the planetary type
• CPC Class Codes: F02N 15/06 the toothed gears being moved by axial displacement
• CPC Class Codes: F02N 2011/0896 Inverters for electric machines, e.g. starter-generators
• CPC Class Codes: F02N 2200/042 Starter torque
• CPC Class Codes: F02N 2200/043 Starter voltage
• CPC Class Codes: F02N 2200/044 Starter current
• CPC Class Codes: F02N 2200/063 Battery voltage
• CPC Class Codes: F02N 2250/02 Battery voltage drop at start, e.g. drops causing ECU reset
• CPC Class Codes: F02N 2300/102 Control of the starter motor speed; Control of the engine speed during cranking
• CPC Class Codes: F02N 2300/104 Control of the starter motor torque
• CPC Class Codes: F02N 2300/106 Control of starter current
• CPC Class Codes: F02N 2300/2008 using a model
• CPC Class Codes: H02P 29/032 Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
• CPC Class Codes: H02P 6/08 Arrangements for controlling the speed or torque of a single motor H02P6/10, H02P6/28 take precedence

Abstract

An electric starter system is usable with an engine and a power inverter module (PIM), e.g., of a powertrain. The starter system includes a polyphase/AC brushless starter motor connected to the PIM via an AC voltage bus and selectively connected to the engine during a requested engine start event. A sensor on the DC voltage bus outputs a signal indicative of a voltage level of the DC voltage bus. The controller executes a method using voltage stabilization logic having a proportional-integral (PI) torque control loop. Logic execution in response to the requested engine starting event causes the controller to control the starter motor, when the bus voltage exceeds a calibrated minimum voltage, using a starting torque determined via the control loop. The commanded starting torque limits inrush current to the starter motor such that the DC voltage bus remains above the minimum voltage.

Claims

1. An electric starter system for use with an internal combustion engine, a direct current (DC) voltage bus, an alternating current (AC) voltage bus, and a power inverter module (PIM) electrically connected to the DC voltage bus and the AC voltage bus, the electric starter system comprising:

a polyphase/AC brushless starter motor that is electrically connected to the AC voltage bus, the starter motor being selectively connectable to the engine in response to a requested engine start event;

an electrical sensor connected to the DC voltage bus and configured to output a signal indicative of a voltage level of the DC voltage bus; and

a controller in communication with the electrical sensor and programmed with voltage stabilization logic, the voltage stabilization logic including a proportional-integral (PI) torque control loop;

wherein execution of the voltage stabilization logic in response to the requested engine start event, when the voltage level of the DC voltage bus is less than a calibrated minimum voltage, causes the controller to determine a required starting torque of the starter motor using the PI torque control loop, and further causes the controller to transmit a torque command to the starter motor to cause the starter motor to transmit the required starting torque to the engine, the required starting torque having a value that limits an inrush current to the starter motor such that the voltage level of the DC voltage bus remains above the calibrated minimum voltage.

2. The electric starter system of claim 1, wherein the starter motor includes a rotor and the engine includes a flywheel, the electric starter system further comprising:

a solenoid coupled to the rotor; and

a pinion gear coupled to the solenoid;

wherein the solenoid is configured to translate the pinion gear into meshed engagement with the flywheel in response to the requested engine start event.

3. The electric starter system of claim 1, wherein a maximum voltage level of the DC voltage bus is 13V, and wherein the calibrated minimum voltage is between 8V and 9V.

4. The electric starter system of claim 1, wherein the controller is further configured to limit a current level of the DC voltage bus to about 500 A such that the bus voltage is maintained above the calibrated minimum voltage.

5. The electric starter system of claim 1, wherein the controller is further configured to generate or command pulse width modulation of the PIM and the starter motor to achieve the adjusted requested torque.

6. The electric starter system of claim 1, wherein the controller uses a pair of torque-speed models for the starter motor and a reference/hypothetical brush-type starter motor, the torque-speed models receiving a present speed of the starter motor and outputting a corresponding maximum torque capability for the starter motor and the reference/hypothetical brush-type starter motor, and torque limiter block that limits the torque command between the corresponding maximum torque capacity of the starter motor and the reference/hypothetical brush-type starter motor.

7. A method for stabilizing voltage on a direct current (DC) voltage bus in a system having an internal combustion engine, a power inverter module (PIM) electrically connected to an alternating current (AC) and a direct current (DC) voltage bus of the powertrain, a polyphase/AC brushless starter motor electrically connected to the PIM via the AC voltage bus and selectively coupled to the engine during a requested engine start event, and a controller programmed with voltage stabilization logic that includes a proportional-integral (PI) torque control loop, the method comprising:

responsive to the requested engine start event, determining the voltage level of the DC voltage bus using an electrical sensor;

comparing the voltage level to a calibrated minimum voltage using the controller;

responsive to the voltage level being less than the calibrated minimum voltage;

determining, using the PI torque control loop, a motor torque of the starter motor; and

transmitting the motor torque to the starter motor as a commanded starting torque to thereby crank and start the engine;

wherein the commanded starting torque has a value that limits inrush current to the starter motor, such that the voltage level of the DC voltage bus remains above the calibrated minimum voltage.

8. The method of claim 7, the powertrain further including a transmission coupled to the engine, a drive axle coupled to the transmission, and a load coupled to the drive axle, the method further comprising:

transferring torque from the engine to the load through the transmission and drive axle.

9. The method of claim 8, wherein the load is a set of drive wheels of a motor vehicle.

10. The method of claim 9, wherein the engine includes a flywheel and the powertrain further includes a solenoid coupled to the rotor and a pinion gear coupled to the solenoid, the method further comprising:

translating the pinion gear into engagement with the flywheel via the solenoid during the requested engine start event.

11. The method of claim 9, wherein a maximum voltage level of the DC voltage bus is 13V, and wherein the calibrated minimum voltage is between 8V and 9V.

12. The method of claim 9, further comprising:

limiting, via the controller, a current level of the DC voltage bus to about 500 A such that the bus voltage is maintained above the calibrated minimum voltage.

13. The method of claim 9, further comprising:

generating or commanding pulse width modulation of the PIM and the starter motor to achieve the adjusted requested torque.

14. The method of claim 9, wherein the controller is programmed with a pair of torque-speed models for the brushless starter motor and a reference/hypothetical brush-type starter motor, the method further comprising:

receiving a present speed of the starter motor via the controller; and

outputting a corresponding maximum torque capability for the starter motor and the reference/hypothetical brush-type starter motor using the torque-speed models; and

limiting the torque command, via a torque limiter block of the controller, between the corresponding maximum torque capacity of the starter motor and the reference/hypothetical brush-type starter motor.

15. A powertrain comprising:

an internal combustion engine;

a transmission connected to the engine;

a direct current (DC) voltage bus;

an alternating current (AC) voltage bus;

a power inverter module (PIM) electrically connected to the AC voltage bus and the DC voltage bus;

a polyphase/AC brushless starter motor electrically connected to the PIM via the AC voltage bus, wherein the starter motor is selectively coupled to the engine in response to a requested engine start event;

an electrical sensor connected to the DC voltage bus and configured to output a signal indicative of a voltage level of the DC voltage bus; and

a controller in communication with the electrical sensor and programmed with voltage stabilization logic that includes a proportional-integral (PI) torque control loop, wherein execution of the voltage stabilization logic in response to the requested engine start event, when the voltage level of the DC voltage bus is less than a calibrated minimum voltage, causes the controller to determine a starting torque of the starter motor using the PI torque control loop, and to transmit the required starting torque to the starter motor as a torque command to thereby crank and start the engine;

wherein the starting torque has a value that limits inrush current to the starter motor such that the voltage level of the DC voltage bus remains above the calibrated minimum voltage.

16. The powertrain of claim 15, further comprising:

a drive axle coupled to the transmission, and a load coupled to the drive axle, with the torque from the engine being transferred to the load through the transmission and the drive axle.

17. The powertrain of claim 16, wherein the load is a set of drive wheels of a motor vehicle.

18. The powertrain of claim 15, wherein the starter motor includes a rotor and the engine includes a flywheel, the powertrain further comprising:

a solenoid coupled to the rotor; and

a pinion gear coupled to the solenoid;

wherein the solenoid is configured to translate the pinion gear into meshed engagement with the flywheel in response to the requested engine start event.