JP2013007268A - Air intake device of internal combustion engine with supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fresh air containing EGR gas from blowing onto an air flowmeter 12 when a recirculation valve 17 is opened.SOLUTION: A compressor 5 of a turbo supercharger 3 is located between an air flowmeter 12 and a throttle valve 13. An EGR passage 21 is connected to an intake passage 10 at the upstream of the compressor 5. A volume chamber 31 is connected to the intake passage 10 so that the fresh air containing EGR gas is prevented from blowing onto the air flowmeter 12 even at the maximum supercharging pressure. When the recirculation valve 17 is opened and the gas flows backward, a part of the gas is received in the volume chamber 31, thereby preventing contamination of the air flowmeter 12 without increasing the length of the intake passage 10.

Description

  The present invention relates to an intake device for an internal combustion engine with a supercharger provided with a recirculation valve, and more particularly to an intake device for an internal combustion engine with a supercharger of a type in which EGR gas is introduced from upstream of a compressor.

  As disclosed in Patent Document 1, in an intake device for an internal combustion engine equipped with a supercharger, particularly a turbocharger, when the throttle valve is suddenly closed from a supercharged state, the compressor downstream to the compressor upstream A configuration having a recirculation valve for releasing the supercharging pressure is known. Further, as an exhaust gas recirculation (EGR) device, a configuration in which EGR gas taken out from an exhaust system is introduced into fresh air upstream of a compressor as in Patent Document 1 is also known.

JP 2007-278110 A

  As described above, in the configuration in which the recirculation valve that releases the supercharging pressure from the downstream of the compressor to the upstream of the compressor is combined with the internal combustion engine with a supercharger that introduces EGR gas freshly on the upstream side of the compressor. When the recirculation valve is opened under the operating conditions in which exhaust gas recirculation is performed, fresh air containing EGR gas flows backward in the intake passage through the recirculation valve. Therefore, there arises a problem that the air flow meter is fouled by the EGR gas component.

  In the intake device for an internal combustion engine with a supercharger according to the present invention, the compressor of the supercharger is located between the air flow meter and the throttle valve, and when the throttle valve is closed, the pressure downstream of the compressor is released upstream of the compressor. The recirculation passage and the recirculation valve are provided, and an EGR passage for introducing EGR gas into the intake system is connected upstream of the compressor.

  A volume chamber into which intake air flowing back from the recirculation passage side can flow is connected to a section from the air flow meter of the intake passage to the junction of the recirculation passage.

  That is, when the recirculation valve is opened, the reverse flow of the gas is caused by the recirculation of the gas (fresh air including EGR gas) supercharged at the high pressure that existed in the intake passage from the compressor to the throttle valve. This is caused by expansion as the valve opens. Since the pressure upstream of the compressor is almost atmospheric pressure, basically, the higher the supercharging pressure, the larger the amount of gas flowing backward, which is the intake passage volume from the air flow meter to the confluence of the EGR passage (this part is Before the recirculation valve is opened, the gas containing EGR gas reaches the air flow meter if it exceeds the fresh air not containing EGR gas. Therefore, if the intake passage volume from the air flow meter to the confluence of the EGR passage is sufficiently large, gas containing EGR gas does not reach the air flow meter. The volume chamber substantially becomes a part of the intake passage volume, and temporarily stores a part of the gas including the backflowed EGR gas. Thereby, it is suppressed that the gas containing EGR gas reaches | attains an air flow meter, and the contamination can be prevented.

  According to the present invention, contamination of the air flow meter due to EGR gas when the recirculation valve is opened during exhaust gas recirculation is prevented without extremely increasing the length of the intake passage from the compressor to the air flow meter. Therefore, it is possible to avoid a reduction in the accuracy of measuring the amount of intake air and the restrictions on the layout associated with increasing the length of the intake passage from the compressor to the air flow meter.

BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing which showed one Example of the intake device of the internal combustion engine which concerns on this invention with the exhaust system of the internal combustion engine. The principal part enlarged view which shows the Example of the volume chamber provided with the cover member. The functional block diagram which shows control of a cover member.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing the overall structure of an intake and exhaust system of an internal combustion engine 1 equipped with an intake device according to the present invention. A turbocharger is provided in an exhaust passage 2 of the internal combustion engine 1 which is a gasoline engine. 3 is disposed, and a catalytic converter 6 using, for example, a three-way catalyst is disposed downstream thereof. An exhaust silencer (not shown) is provided further downstream of the exhaust passage 2, and the exhaust passage 2 is opened to the outside through the exhaust silencer. The exhaust turbine 4 includes a known waste gate valve 7 for supercharging pressure control. The internal combustion engine 1 has, for example, a direct injection type structure, and includes a fuel injection valve (not shown) for injecting fuel into the cylinder for each cylinder.

  In the intake passage 10 of the internal combustion engine 1, an air cleaner 11, an air flow meter 12, and a throttle valve 13 are arranged in this order from the upstream side, and the compressor 5 of the turbocharger 3 is connected to the air flow meter 12 and the throttle. It is arranged between the valve 13. As a result, the intake passage 10 includes a compressor upstream passage portion 10a upstream from the compressor 5, a compressor downstream passage portion 10b between the compressor 5 and the throttle valve 13, and a throttle between the throttle valve 13 and each cylinder. It can be roughly divided into a downstream passage portion 10c. In this embodiment, for example, a water-cooled or oil-cooled intercooler 14 is interposed in the throttle downstream passage portion 10c, and the downstream side of the intercooler 14 branches into each cylinder as an intake manifold. ing. The intercooler 14 may be an air-cooled type.

  The intake passage 10 is further provided with a recirculation passage 16 communicating between the upstream side and the downstream side of the compressor 5, and a recirculation valve 17 is provided in the recirculation passage 16. It has been. The recirculation valve 17 includes, for example, a mechanical actuator that operates in response to a pressure difference across the throttle valve 13 or an electrical actuator that operates in response to a control signal from a control unit (not shown). For example, when the throttle valve 13 is closed, the recirculation passage 16 is opened based on the pressure increase in the compressor downstream passage portion 10b, and the pressure in the compressor downstream passage portion 10b is circulated so that the intake air circulates. Is released to the compressor upstream passage portion 10a. The recirculation passage 16 connects the position of the compressor downstream passage portion 10b near the compressor 5 and the position of the compressor upstream passage portion 10a near the compressor 5.

  Further, the EGR passage 21 constituting the exhaust gas recirculation device branches off from the downstream side of the catalytic converter 6 in the exhaust passage 2, and the tip thereof is connected to the compressor upstream side passage portion 10 a of the intake passage 10 at the junction 22. . The junction 22 is located relatively downstream of the compressor upstream passage portion 10 a, that is, at a position close to the compressor 5, but is located upstream of the junction 20 with the recirculation passage 16. The EGR passage 21 is provided with a water-cooled or oil-cooled EGR gas cooler 23 for cooling the EGR gas, and an exhaust gas for controlling the exhaust gas recirculation amount downstream of the EGR passage 21 so as to follow the target exhaust gas recirculation rate. A reflux control valve 24 is interposed.

  In the configuration as described above, EGR gas is introduced to the upstream side of the compressor 5 through the exhaust gas recirculation control valve 24 under predetermined operating conditions in which exhaust gas recirculation including both the supercharging region and the non-supercharging region is to be performed. The The fresh air containing the EGR gas is pressurized by the compressor 5 in the supercharging region, and is supplied to each cylinder of the internal combustion engine 1 through the throttle valve 13 and the intercooler 14. In such a supercharging region, for example, when the throttle valve 13 is suddenly closed in accordance with the driver's accelerator pedal operation, the recirculation valve 17 is opened in conjunction with this, and the high pressure in the compressor downstream passage portion 10b is increased. The new air that has become is released to the compressor upstream passage portion 10a. Thereby, even if the compressor 5 continues to rotate due to the inertia of the rotor, the discharged fresh air circulates through the recirculation passage 16, and generation of abnormal noise due to the surge of the compressor 5 is avoided.

  By the way, when the recirculation valve 17 is opened in accordance with the closing operation of the throttle valve 13 as described above under the condition where the exhaust gas is recirculated, the EGR in the compressor downstream side passage portion 10b at a relatively high pressure is used. The fresh air containing gas expands through the recirculation valve 17 and flows back through the compressor upstream side passage portion 10a. When the fresh air containing the backflowed EGR gas reaches the air flow meter 12, the air flow meter 12 is contaminated by the EGR gas component, which is not preferable.

  Therefore, in the present embodiment, a volume chamber 31 for temporarily receiving the backflowed gas is connected to the compressor upstream side passage portion 10a of the intake passage 10. The volume chamber 31 has an inlet 32 at one end and an outlet 33 at the other end, and the outlet 33 is connected to a position relatively upstream as viewed in the normal flow direction of the intake passage 10. The inlet 32 is connected to a relatively downstream position. That is, when the gas flows backward due to the opening operation of the recirculation valve 17, the gas flowing backward from the compressor 5 flows in from the inlet 32, and the gas (air) that has existed in the volume chamber 31 until then flows into the outlet. It is comprised so that it may be extruded from 33. The intake passage 10 has a relatively small radius of curvature so that the portion immediately upstream of the junction 22 with the EGR passage 21 is turned approximately 90 ° so that the gas can easily flow into the inlet 32 during reverse flow. It is formed as a curved portion 34, and the inlet 32 is connected to the outer peripheral side of the curved portion 34 so as to follow the direction of flow from the compressor 5 side toward the curved portion 34, that is, the straight direction from the compressor 5 side during reverse flow. ing. Further, the outlet 33 joins the intake passage 10 at an acute angle so that intake air flowing through the intake passage 10 from the air flow meter 12 side during normal times does not easily enter. In other words, the directing direction of the outlet 33 is inclined with respect to the intake passage 10 so that the flow of gas flowing out from the outlet 33 is directed downstream of the intake passage 10.

Next, the volume of the volume chamber 31 and the passage cross-sectional area of the inlet 32 will be described. In the following, the intake passage volume from the air flow meter 12 to the junction 22 with the EGR passage 21 is V ₁ (m ³ ), the cross-sectional area of the passage is S ₁ (m ² ), and the volume of the volume chamber 31 is V ₂ (m ³ ), the passage cross-sectional area of the inlet 32 is S ₂ (m ² ), and the intake passage volume of the compressor downstream passage portion 10b (from the compressor 5 to the throttle valve 13) that causes the backflow is V ₃ (m ³ ) The pressure upstream of the compressor is P ₁ (kPa), the maximum supercharging pressure is P _b (kPa) under the operating conditions where EGR is introduced, and the recirculation valve 17 is opened when the recirculation valve 17 is opened. 17 intake passage 10 the volume of blown back blowback gas upstream V ₄ through (m ^3), the specific heat ratio of the fresh air containing EGR gas present in the compressor downstream passage portion in 10b kappa, compressor 5 on The gas temperature at the side T ₁ (° K), the gas temperature at the compressor downstream passage portion in 10b in the maximum boost pressure _{P b T 3 (° K)} , to the compressor 5 upstream through the recirculation valve 17 The gas temperature when released is T ₄ (° K), and the efficiency of the compressor 5 is η _comp (%).

In the present embodiment, the intake passage volume V ₁ from the air flow meter 12 to the confluence point 22 with the EGR passage 21 and the volume described above so that the fresh air containing EGR gas does not reach the air flow meter 12 at the time of reverse flow. The sum V _total with the chamber volume V ₂ is set to be larger than the maximum blow-back gas volume V ₄ obtained based on the maximum supercharging pressure P _b under the operating conditions in which EGR is introduced.

That is, the relationship is as shown in the following equation (1). The right side of the equation (1) corresponds to the blow-back gas volume V ₄ at the maximum supercharging pressure P _b .

Alternatively, this relationship is that the gas temperature T ₃ (° K) in the compressor downstream side passage portion 10 _{b at the} maximum supercharging pressure P _b and the gas temperature when released to the compressor 5 upstream through the recirculation valve 17. Using T ₄ (° K), it can also be expressed as the following equation (2).

The gas temperature T ₃ can be obtained from the following equation (3) based on the compressor efficiency η _comp (%) of the compressor 5.

However, T ₃ ′ is a theoretical adiabatic compression temperature (° K) when the compressor 5 compresses from the pressure P ₁ upstream of the compressor 5 to the maximum supercharging pressure P _b .

The gas temperature T ₄ can be obtained from the following equation (4).

The first term on the right side of the above equation (1) basically indicates that the gas at the supercharging pressure P _b is expanded to the upstream pressure P ₁ and passes through the recirculation valve 17 to the compressor upstream side passage portion 10a. The second term is a correction term accompanying a change in gas temperature. During the reverse flow, the gas existing in the compressor upstream side passage portion 10a (particularly the section from the air flow meter 12 to the confluence 22 of the EGR passage 21) first flows through the air flow meter 12 in the reverse direction. Since the partial gas and the gas in the volume chamber 31 are fresh air that does not contain EGR gas, they do not cause fouling. Therefore, here, the expansion of the gas (volume V ₃ , pressure P _b ) existing in the compressor downstream passage portion 10b when the recirculation valve 17 is opened is a subject of consideration.

That is, from the general expression of the adiabatic change of gas, the gas pressure is P (kPa), the volume is V (m ³ ), the temperature is T (° K), the specific heat ratio is κ, and the state before the change is subscript α. If the state after change is represented by the subscript β, from the relationship of “P × V ^κ = constant”,
P _α × V _α ^κ = P _β × V _β ^κ
Therefore, the following equation (5) is obtained.

From the relationship of “T × V ^κ-1 = constant”,
T _α × V _α ^κ-1 = T _β × V _β ^κ-1
T _β = T _α × (V _α / V _β ) ^κ-1
From the above equation (5), the following equation (6) is obtained.

On the other hand, the surplus gas amount when the gas having the volume V ₃ of the supercharging pressure P _b existing in the compressor downstream-side passage portion 10b expands to the pressure P ₁ is the _first value on the right side of the above-described equation (1). As in item 1, V ₃ × {(P _b −P ₁ ) / P ₁ }, which is the volume at the temperature T ₃ of the supercharging condition, and therefore the recirculation valve 17 is opened. After that, the volume of the gas at the temperature T ₄ becomes (T ₄ / T ₃ ) times.

That is, the volume V ₄ of the surplus gas (blow-back gas) overflowing through the recirculation valve 17 is as shown on the right side of the above equation (2):
_{V 4 = V 3 × {(} P b -P 1) / P 1} × (T 4 / T 3)
It becomes.

Here, from the above equation (6), the gas temperature T ₄ is

  So if you substitute this,

  It becomes.

Accordingly, in order to prevent the backflowed gas from reaching the air flow meter 12, the volume V _total of the passage to the air flow meter 12 needs to exceed the blown-back gas volume V ₄ , which is described above (1 ) Expression relationship is required.

That is, since the blow-back gas volume V ₄ is determined according to the supercharging pressure P _b at that time, the blow-back gas volume V ₄ should exceed the blow-back gas volume V ₄ corresponding to the maximum supercharging pressure P _b under the operating conditions in which EGR is introduced. If the passage volume V _total is set to, the air flow meter 12 will not be polluted with EGR gas.

As described above, the gas temperature T ₃ can be obtained from the above equation (3) based on the compressor efficiency η _comp of the compressor 5.

That is, assuming that the gas temperature upstream of the compressor 5 is T ₁ and the temperature after theoretical adiabatic compression when compressed by the compressor 5 from the pressure P ₁ to the maximum boost pressure P _b is T ₃ ′, the temperature from the above equation (6) T ₃ ′ is expressed by the following equation (9).

Here, the pressure ratio is π _c (= P _b / P ₁ ), the difference between the theoretical adiabatic compression temperature T ₃ ′ and the gas temperature T ₁ is ΔT (= T ₃ ′ −T ₁ ), and the compressor efficiency is η _comp (%), The gas temperature rise due to compression is
ΔT / (η _comp / 100)
So,
The gas temperature T ₃ after compression is

  It becomes.

Also, the gas temperature T ₄ can be expressed as in equation (4) using the pressure ratio π _c from the relationship in equation (6) above.

The coefficient on the right side of the above equation (1) is about 0.67 when the maximum supercharging pressure P _b is 180 kPa, the compressor upstream pressure P ₁ is 100 kPa, and the specific heat ratio κ is 1.4. Therefore, simply, if the volume V ₂ of the volume chamber 31 is set so that the volume V _total becomes “0.65 × V ₃ ”, the air flow meter 12 can be substantially prevented from being contaminated by backflow. Is possible.

On the other hand, the passage sectional area S ₁ of the intake passage 10 from the air flow meter 12 to the junction point 22 with the EGR passage 21 and the passage sectional area S ₂ of the inlet 32 of the volume chamber 31 are expressed by the following equation (10). It is desirable to satisfy the relationship.

That is, the gas that has flowed back is diverted according to both the passage cross-sectional areas S ₁ and S ₂ , and in order that the gas flowing through the intake passage 10 of the passage cross-sectional area S ₁ does not reach the air flow meter 12,
V ₁ > V ₄ × {S ₁ / (S ₁ + S ₂ )}
Is necessary, and therefore
S ₁ <S ₂ × {V ₁ / (V ₄ −V ₁ )}
It becomes.

On the other hand, in order not to overflow the volume chamber 31,
V ₂ > V ₄ × {S ₂ / (S ₁ + S ₂ )}
Is necessary, and therefore
S ₁ > S ₂ × {(V ₄ −V ₂ ) / V ₂ }
It becomes.

Therefore, when these two restrictions are put together, the relationship of the above equation (10) is obtained. If this relationship is satisfied, the volume chamber 31 does not overflow and the gas diverted to the intake passage 10 side enters the air flow meter 12. Not reach. The passage sectional area of the outlet 33 is set to be equal to or larger than the passage sectional area S ₂ of the inlet 32.

  As described above, according to the above-described embodiment, the addition of the volume chamber 31 to the intake system can prevent the air flow meter 12 from being contaminated by the backflow of the gas including the EGR gas when the recirculation valve 17 is opened. In particular, it is not necessary to increase the length of the intake passage 10 (particularly, the compressor upstream passage portion 10a), the layout in the engine room of the vehicle is not restricted, and the air flow meter 12 caused by the passage length is not affected. A decrease in intake air amount measurement accuracy (deterioration of responsiveness) can be avoided.

  By appropriately setting the dimensions of the respective parts of the volume chamber 31, the volume chamber 31 can simultaneously function as a resonator for intake noise, and intake noise can be reduced.

  Next, FIG. 2 shows an embodiment in which a lid member 41 for opening and closing the inlet 32 is provided at the inlet 32 of the volume chamber 31. The lid member 41 is configured, for example, in a flap shape whose one end is rotatably supported on the side wall of the intake passage 10 and opens to the inside of the inlet 32. In this way, by providing the lid member 41 that closes the inlet 32 except during the reverse flow, the volume chamber 31 is substantially separated from the intake passage 10 at the normal time, and the influence on the normal intake flow is minimized. It will be a thing.

  The lid member 41 needs to be opened by some means at the time of backflow. For example, in one embodiment, the flap-shaped lid member 41 is biased in the closing direction by a spring member, and the lid member at the time of backflow. 41 is configured to open by the force received from the gas.

  In the second embodiment, the lid member 41 is mechanically linked to the recirculation valve 17 via a link member or the like so that the lid member 41 opens in conjunction with the opening operation of the recirculation valve 17. Composed.

  Further, in the third embodiment, the lid member 41 is provided with an actuator that operates in response to an electrical signal such as a solenoid, and is linked to the opening operation of the recirculation valve 17 in response to a control signal from the control unit. Configured to open with.

In this case, the lid member 41 may be configured to be opened when the recirculation valve 17 is opened. However, the volume V ₄ of the blow-back gas described above is calculated and calculated based on the supercharging pressure at that time. The lid member 41 may be configured to open only when it is determined that the blown-back gas volume V ₄ exceeds the intake passage volume V ₁ described above.

FIG. 3 shows such control as a functional block diagram. The intake air amount of the block 101 is detected by the air flow meter 12, the compressor inlet side pressure (P ₁ ) of the block 102, and the compressor outlet of the block 103. The side pressure (P _b ) and the compressor inlet side temperature (T ₁ ) of the block 104 are detected by sensors (not shown). A block 105 is a compressor efficiency map, and the compressor efficiency (η _comp ) is output from the intake air amount (that is, the flow rate of the compressor 5) and the pressure ratio. Then, in block 106, the blown-back gas volume (V ₄ ) corresponding to the right side of the above-described equation (2) is obtained, and in block 107, the blow-back gas volume (V ₄ ) is determined as a predetermined intake passage volume (V ₁ ). When it is determined that the intake passage volume (V ₁ ) is exceeded, an open command signal is output to the actuator of the lid member 41.

  In the above embodiment, an example in which the turbocharger 3 in which the compressor 5 and the exhaust turbine 4 are directly connected on the same axis as the supercharger has been described. However, the present invention is applied to such a turbocharger. The present invention is not limited, and any type of supercharger can be similarly applied as long as it has a recirculation valve.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 3 ... Turbocharger 5 ... Compressor 10 ... Intake passage 12 ... Air flow meter 13 ... Throttle valve 17 ... Recirculation valve 21 ... EGR passage 31 ... Volume chamber 32 ... Inlet 33 ... Outlet 34 ... Curve part

Claims (5)

The supercharger compressor is located between the air flow meter and the throttle valve, and has a recirculation passage and a recirculation valve for releasing the pressure downstream of the compressor upstream of the compressor when the throttle valve is closed, and EGR In the intake system for an internal combustion engine with a supercharger in which an EGR passage for introducing gas into the intake system is connected upstream of the compressor,
With a supercharger, a volume chamber into which intake air that flows backward from the recirculation passage side can flow is connected to a section from the air flow meter of the intake passage to the junction of the recirculation passage. An intake device for an internal combustion engine. The volume chamber includes an inlet connected to a position relatively downstream of the intake passage, and an outlet connected to a position relatively upstream of the intake passage.
A curved portion is provided on the compressor upstream side of the intake passage, and the inlet is connected to the curved portion so as to follow a flow direction from the compressor side toward the curved portion at the time of reverse flow. The intake device for a supercharged internal combustion engine according to claim 1. The intake passage volume from the air flow meter to the confluence of the EGR passage is V ₁ , the volume chamber volume is V ₂ , the intake passage volume from the compressor to the throttle valve is V ₃ , and When the volume of the gas blown back by the expansion of the gas of the volume V ₃ when the circulation valve is opened is V ₄ , the passage sectional area S ₂ of the inlet of the volume chamber and the passage of the intake passage in the section sectional area S ₁ is an intake device for supercharged internal combustion engine according to claim 1 or 2, characterized in that it is set to equation the following relationship.

  The intake device for an internal combustion engine with a supercharger according to any one of claims 1 to 3, further comprising a lid member that opens at the inlet of the volume chamber when the recirculation flows from the recirculation passage side. The sum of the intake passage volume (V ₁ ) from the air flow meter to the confluence of the EGR passage and the volume (V ₂ ) of the volume chamber is the maximum supercharging pressure (P 5. The intake device for an internal combustion engine with a supercharger according to claim 1, wherein the intake device is set to be larger than a maximum blown-back gas volume (V ₄ ) obtained based on _b ).

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