Control Device and Control Method for Variable Valve Timing Mechanism

Patent metadata

Field	Value
Publication number	US-2021340887-A1
Application number	US-201917284211-A
Country	US
Kind code	A1
Filing date	Nov 13, 2019
Priority date	Nov 14, 2018
Publication date	Nov 4, 2021
Grant date	—

Abstract

A control device and a control method for a variable valve timing mechanism are provided so as to improve the accuracy of cam phase angle interpolation without using a motor rotation angle sensor. The control device for the variable valve timing mechanism includes a controller configured to detect a phase angle of a cam based on a cam signal and control the phase angle of the cam by using an electric motor. The controller is configured such that a motor torque estimation unit calculates a motor torque from a motor current based on motor characteristics, a motor rotation-angle estimation unit calculates a motor rotation angle at least based on the motor torque and an engine operating state, and a conversion unit and a feedback control unit interpolate the cam phase angle of the variable valve timing mechanism from the motor rotation angle.

First claim

1 .- 20 . (canceled)

21 . A control device for a variable valve timing mechanism configured to detect a phase angle of a cam based on a cam signal and control the phase angle of the cam by using an electric motor,
the control device comprising a controller configured to calculate a motor torque from a motor current based on motor characteristics, calculate a motor rotation angle at least based on the motor torque and an engine operating state, and interpolate a cam phase angle of the variable valve timing mechanism from the motor rotation angle, wherein the controller calculates the motor rotation angle by using an engine speed, an engine rotation angle, and an engine oil temperature in the calculation of the motor rotation angle.

22 . The control device for a variable valve timing mechanism according to claim 21 , wherein the controller calibrates an interpolated value to a detected value when the phase angle of the cam is detected based on the cam signal.

23 . The control device for a variable valve timing mechanism according to claim 21 , wherein the motor rotation angle is calculated by the controller based on an equation of motion in consideration of factors relevant to phase angle conversion.

24 . The control device for a variable valve timing mechanism according to claim 21 , wherein the controller calculates the motor torque based on torque-current characteristics of a DC motor.

25 . The control device for a variable valve timing mechanism according to claim 21 , wherein the controller corrects the calculation of the motor torque based on at least one of a power supply voltage, a driving duty, and a motor temperature.

26 . The control device for a variable valve timing mechanism according to claim 21 , wherein the motor current is determined by using a sensor detected value or is estimated from a manipulated variable of the electric motor.

27 . The control device for a variable valve timing mechanism according to claim 21 , wherein the controller performs phase angle interpolation at a transient of phase angle control using the electric motor, whereas the controller does not perform phase angle interpolation in a steady state.

28 . The control device for a variable valve timing mechanism according to claim 21 , wherein the controller performs phase angle interpolation when an engine speed is at most a predetermined value, whereas the controller does not perform phase angle interpolation when the engine speed is higher than the predetermined value.

29 . The control device for a variable valve timing mechanism according to claim 21 , wherein the controller learns characteristics of a motor torque and a motor rotation angle that are output relative to the input motor current.

30 . The control device for a variable valve timing mechanism according to claim 21 , wherein the controller has a function of learning characteristics of motor current detection relative to a manipulated variable of the electric motor.

31 . The control device for a variable valve timing mechanism according to claim 21 , wherein the controller corrects the calculation of at least one of the motor torque and the motor rotation angle according to a difference between an interpolated value and a detected value when the phase angle is calibrated.

32 . A control method for a variable valve timing mechanism configured to detect a phase angle of a cam based on a cam signal and control the phase angle of the cam by using an electric motor, the control method comprising:
calculating a motor torque from a motor current based on motor characteristics; calculating a motor rotation angle at least based on the motor torque and an engine operating state; interpolating a cam phase angle of the variable valve timing mechanism from the motor rotation angle; and correcting the calculation of the motor rotation angle by using an engine speed, an engine rotation angle, and an engine oil temperature.

33 . The control method for a variable valve timing mechanism according to claim 32 , wherein an interpolated value is calibrated to a detected value when the phase angle of the cam is detected based on the cam signal.

34 . The control method for a variable valve timing mechanism according to claim 32 , wherein the motor rotation angle is calculated based on an equation of motion in consideration of factors relevant to phase angle conversion.

35 . The control method for a variable valve timing mechanism according to claim 32 , wherein the motor torque is calculated based on torque-current characteristics of a DC motor.

36 . The control method for a variable valve timing mechanism according to claim 32 , wherein the calculation of the motor torque is corrected based on at least one of a power supply voltage, a driving duty, and a motor temperature.

37 . The control method for a variable valve timing mechanism according to claim 32 , further comprising determining whether phase angle control using the electric motor is in a transient state, wherein phase angle interpolation is performed at a transient of the phase angle control, whereas phase angle interpolation is not performed in a steady state.

38 . The control method for a variable valve timing mechanism according to claim 32 , further comprising determining whether an engine speed is at most a predetermined value,
wherein phase angle interpolation is performed when the engine speed is at most the predetermined value, whereas phase angle interpolation is not performed when the engine speed is higher than the predetermined value.

Assignees

• Hitachi Astemo Ltd

Inventors

• Kosuda Masaki
• Shimizu Hirokazu
• Matsuo Nobuhiko

Classifications

• F01L1/352 Primary

  using bevel or epicyclic gear · CPC title

• Y02T10/12

  Improving ICE efficiencies · CPC title

• F01L2800/05

  Timing control under consideration of oil condition · CPC title

• F01L2201/00

  Electronic control systems; Apparatus or methods therefor · CPC title

• F01L2820/032

  Electric motors · CPC title