JPWO2021192927A5 - - Google Patents

Claims (4)

a throttle valve (81) provided in an intake passage (6) through which intake air to a combustion chamber (38) of the internal combustion engine (3) passes, and controlled to an arbitrary degree of opening to control the amount of intake air;
Passage cross section of the main passage (6A) of the intake passage (6) which is provided downstream from the throttle valve (81) and divided into a main passage (6A) and a tumble passage (6B) along the passage direction. An intake system for an internal combustion engine for a straddle-type vehicle, comprising a tumble control valve (71) that opens and closes to control the supply of intake air to the main passage (6A),
The intake passage (6) has a partition wall (65) that bisects the interior in the direction of the passage,
The cross section of the tumble passage (6B) on the side of the downstream end (6Bb) is defined in a circular cross section by the partition wall (65) having an arc shape up to the downstream end (6Bb), and the cross section of the upstream end (6Ba) is The linear partition wall (65) defines a semicircular shape with a maximum diameter larger than the diameter of the circular cross section,
The cross-sectional area of the cross section of the upstream end (6Ba) is larger than the cross-sectional area of the cross section of the downstream end (6Bb),
When viewed in the direction of the cylinder axis (X), the imaginary line (I) extended from the center of the downstream end (6b) of the intake passage (6) does not point toward the center (O) of the cylinder, and the tumble passage (6B) is: An intake system for an internal combustion engine for a saddle-ride type vehicle, characterized in that a center extension imaginary line (U) of a downstream end (6Bb) is curved so as to point toward a cylinder center (O). The cross section of the tumble passage (6B) is gradually deformed and continuous along the passage direction from the semicircular cross section at the upstream end (6Ba) to the circular cross section at the downstream end (6Bb). 2. An intake system for an internal combustion engine for a saddle type vehicle according to claim 1, wherein The saddle type according to claim 1 or claim 2, wherein the tumble passage (6B) has a circular cross section for a predetermined length from the downstream end (6Bb) side to the downstream end. An intake system for an internal combustion engine for a vehicle. 4. A tumble valve plate (71b) of said tumble control valve (71) is formed in a semicircular shape that blocks the entire cross section of said main passage (6A). 1. The intake device for an internal combustion engine for a straddle-type vehicle according to item 1.