Throttle upstream pressure estimating apparatus and cylinder charged air quantity calculating apparatus for internal combustion engine

A throttle upstream pressure estimating apparatus for an internal combustion engine comprising:

• intake air pressure detecting means for detecting an intake air pressure Pm, which represents a pressure downstream of a throttle valve provided in an intake passage of the internal combustion engine;
• and
• throttle upstream pressure estimating means for repeatedly calculating a throttle upstream pressure, which represents a pressure upstream of the throttle valve, at a predetermined time intervals by using an equation of an intake system model which models behaviors of an intake air during a period where a change in the throttle upstream pressure and a change in a throttle opening degree cause a change in the intake air pressure Pm so as to cause a change in an actual cylinder charged air quantity,
• wherein the throttle upstream pressure estimating means substitutes a previous throttle upstream pressure Pthrup(i−1) for a part of a plurality of throttle upstream pressures included in the equation of the intake system model to calculate a present throttle upstream pressure Pthrup(i), and
• wherein the equation of the intake system model is represented by the following Equation:
• Gin
• =
• μ
• ·
• A
• ⁢
• Pthrup
• ⁡
• (
• i
• -
• 1
• )
• R
• ·
• T
• ·
• f
• ⁡
• (
• Pm
• ⁢
• /
• ⁢
• Pthrup
• ⁡
• (
• i
• )
• )
• Gin:
• throttled air quantity [kg/sec]
• μ:
• flow coefficient
• A:
• effective cross-sectional area of throttle opening [m2]
• Pthrup(i−1):
• Previous throttle upstream pressure [Pa]
• Pthrup(i):
• Present throttle upstream pressure [Pa]
• Pm:
• intake air pressure [Pa]
• R:
• gas constant
• T:
• intake air temperature [K]
• f(Pm/Pthrup(i)):
• physical value determined based on Pm/Pthrup(i)
• A=πr2(1−cos2θ)
• r:
• radius of throttle valve [m]
• θ:
• throttle opening degree.