Waste-gate valve device
To provide a waste-gate valve device with a good flow-rate controllability. A waste-gate valve device 1 includes: a turbine housing 3 provide with a waste-gate channel 2 through which exhaust gas bypasses a turbine; and a waste-gate valve 4 to open and close an outlet of the waste-gate channel 2 . The waste-gate valve 4 includes a valve body 7 to open and close the outlet of the waste-gate channel 2 , and a protrusion 8 to be housed in the waste-gate channel 2 when the valve body 7 closes the outlet of the waste-gate channel 2 . The waste-gate channel 2 ensures a maximum flow rate of exhaust gas at a time when the waste-gate valve is fully open. An area ratio of a flow-path cross-sectional area A 1 of the waste-gate channel 2 to a flow-path cross-sectional area A 2 of a merging portion is not more than 0.2, the merging portion being a part at which exhaust gas having passed through the turbine merges. A widened portion 2 A at which the flow-path cross-sectional area increases is disposed on the outlet of the waste-gate channel.
1. A waste-gate valve device, comprising:
a turbine housing comprising a waste-gate channel through which exhaust gas bypasses a turbine and a merging section where exhaust gas having flowed through the waste-gas channel merges with exhaust gas having passed through the turbine; and
a waste-gate valve configured to open and close an outlet of the waste-gate channel, the waste-gate valve comprising
a valve body configured to open and close the outlet of the waste-gate channel, and
a protruding member configured to be housed in the waste-gate channel when the valve body closes the outlet of the waste-gate channel,
wherein the waste-gate channel has a first flow-path diameter (D 1 ) at an input of the waste-gas channel and the merging section of the turbine housing has a second flow-path diameter (D 2 ),
wherein the waste-gate channel ensures a maximum flow rate of exhaust gas at a time when the waste-gate valve is fully open,
wherein a flow-path cross-sectional area ratio of the waste-gate channel to the merging section of the turbine housing is not more than 0.2,
wherein the waste-gate channel has a third flow-path diameter (D 3 ) which is greater than the first flow-path diameter at the outlet of the waste-gate channel, where the flow-path diameter of the waste-gate channel increases forming a curve in cross section and having a flow-path cross sectional area which increases from the input of the waste-gas channel to the merging section of the turbine housing, and
wherein the protruding member includes
a first protrusion that receives, when the waste-gate valve is opened, a pressure of exhaust gas flowing through the waste-gate channel by partially blocking the flow-path of the outlet of the waste-gate channel in a region close to a shaft supporting the waste-gate valve when the waste-gate valve is opened, and
a second protrusion that reduces, when the waste-gate value is being opened, the flow of exhaust gas flowing through the waste-gate channel by partially blocking the flow-path of the outlet of the waste-gate channel in a region remote from the shaft when the waste-gate valve is opened.
2. The waste-gate valve device according to claim 1 , wherein the first flow-path diameter (D 1 ) of the waste-gate channel satisfies a following expression 1, with respect to a relationship to the second flow-path diameter (D 2 )
D 1 ≤0.469× D 2 −0.5 (Expression 1).
3. The waste-gate valve device according to claim 1 , wherein the third flow-path diameter (D 3 ) satisfies a following expression 2, with respect to a relationship to the first flow-path diameter (D 1 )
D 3 ≥1.049 D 1 (Expression 2).
4. The waste-gate valve device according to claim 1 , wherein the first protrusion is formed in the region close to the shaft, and the second protrusion is formed in the region remote from the shaft.
5. The waste-gate valve device according to claim 1 , wherein the first protrusion is formed in an arc shape which forms a recess between the first protrusion and the second portion.
6. The waste-gate valve device according to claim 1 , wherein the protruding member further includes a recess which receives exhaust gas flowing through the waste-gate channel.
7. The waste-gate valve device according to claim 1 , wherein a base portion of the protruding member includes an expanded portion which expands along an inner periphery of the curve formed by the increase of the flow-path diameter of the waste-gate channel.
8. The waste-gate valve device according to claim 1 , wherein the valve body has a rim portion disposed on a seating side of the valve body and formed into a shape of a curved surface.
9. The waste-gate valve device according to claim 1 , wherein the valve body comprises
an end portion for opening and closing the waste-gate channel,
a base portion, and
an elastic-deformation portion disposed between the end portion and the base portion and configured to warp the end portion.
10. The waste-gate valve device according to claim 1 , further comprising:
a drive shaft to which the waste-gate valve is fixed; and
a bush supporting the drive shaft,
wherein a tapered surface is formed on an inner peripheral surface of the bush.
11. The waste-gate valve device according to claim 1 , further comprising:
a drive shaft comprising an end to which the waste-gate valve is fixed;
a bush supporting the drive shaft;
a lever pin disposed on another end of the drive shaft; and
an actuator comprising a rod coupled to the lever pin,
wherein the lever pin and the actuator are disposed so that a pressure direction applied to the waste-gate valve coincides with an operational direction of the actuator.