JPS6233098Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an exhaust gas recirculation system for a supercharged engine, and in particular, the invention relates to an exhaust gas recirculation system for a supercharged engine. In a device in which a passage is opened to the intake passage downstream of the supercharger and the fuel supply device, and a pressure regulating device is provided to obtain a constant exhaust recirculation rate with respect to the amount of intake air, the fuel from the pressure regulating device is Regarding measures to prevent leakage.

Conventionally, in engines equipped with a supercharger for supercharging intake air, a recirculation control valve that uses intake negative pressure as its operating source has been installed in the exhaust recirculation passage for recirculating exhaust gas from the exhaust passage to the intake passage. , a negative pressure passage for introducing intake negative pressure into the recirculation control valve is opened in the intake passage downstream of the supercharger and fuel supply device, and the intake negative pressure in the negative pressure passage is discharged from the exhaust passage. By providing a pressure regulator that adjusts the pressure by controlling dilution with the atmosphere according to the pressure, and controlling the operation of the recirculation control valve according to the exhaust pressure, a constant exhaust recirculation rate can be maintained with respect to the exhaust pressure, that is, the amount of intake air. However, it is well known that exhaust gas is recirculated to effectively reduce NOx in the exhaust gas.

However, in such an exhaust gas recirculation system for a supercharged engine, the negative pressure passage opens downstream of the supercharger and the fuel supply device in the intake passage, and the pressure adjustment device is located in the middle of the negative pressure passage. Since the air-fuel mixture in the intake passage is controlled to be released to the atmosphere by leaks into the atmosphere from the pressure regulator through the negative pressure passage,
There was a problem with fuel leaking.

Therefore, conventionally, in order to prevent such fuel leakage, as disclosed in Japanese Patent Application Laid-Open No. 56-115844, the atmospheric side of the pressure regulator is connected to the fuel supply device on the downstream side of the supercharger in the intake passage. One that opens on the upstream side has been proposed. In other words, in the device disclosed in JP-A-56-115844, since supercharging pressure also acts on the atmospheric side of the pressure regulator during supercharging, this supercharging pressure is not balanced with the supercharging pressure acting on the negative pressure passage. This prevents the flow of air-fuel mixture from the intake passage to the pressure regulating device, thereby preventing fuel from leaking from the pressure regulating device.

However, in the above proposal, in a non-supercharging area such as an exhaust gas recirculation area, the atmospheric side of the pressure regulating device communicates with the downstream side of the turbocharger in the intake passage, so the turbocharger becomes an intake resistance. A negative pressure of 30 mmAq is generated, which upsets the balance with the exhaust pressure (40 to 50 mmAq). As a result, in order to properly control the pressure regulator, it is necessary to prepare separate pressure regulators with different settings for engines equipped with a supercharger and those without. There is a problem that versatility is restricted.

Therefore, the present invention was developed in view of this point, and uses a check valve to only allow air to flow from the pressure regulator to the intake passage, thereby preventing air-fuel mixture from leaking from the pressure regulator. By doing so, the purpose is to prevent fuel leakage from the pressure regulating device when using a supercharger, without being restricted in the versatility of the pressure regulating device for engines equipped with a supercharger and engines not equipped with a supercharger. It is something to do.

To achieve this objective, the configuration of the present invention includes a supercharger for supercharging intake air and a fuel supply device for supplying fuel to the intake passage, while returning exhaust gas from the exhaust passage to the intake passage. A recirculation control valve whose operation source is intake negative pressure is installed in the exhaust recirculation passage for
A negative pressure passage for introducing intake negative pressure into the recirculation control valve is opened to the intake passage downstream from the supercharger and fuel supply device, and the intake negative pressure in the negative pressure passage is converted into exhaust pressure in the exhaust passage. In an exhaust gas recirculation system for a supercharged engine that is equipped with a pressure regulator that adjusts the pressure by controlling dilution with the atmosphere, the air from the pressure regulator to the intake passage is placed in a passage between the pressure regulator and the intake passage. This device is equipped with a check valve that only allows the flow of air, thereby preventing the air-fuel mixture in the intake passage from flowing out from the pressure regulating device to the atmosphere during supercharging.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

The figure shows an example in which the present invention is applied to an engine equipped with a turbo supercharger, where 1 is an engine, 2 is an intake passage for supplying intake air to the engine 1, and 3 is an intake passage for discharging exhaust gas from the engine 1. The exhaust passage 4 is a throttle valve that is disposed in the intake passage 2 and controls the amount of air taken into the engine 1.

5 is a turbine 5a disposed in the exhaust passage 3;
and a blower 5b disposed upstream of the throttle valve 4 in the intake passage 2 and connected to the turbine 5a via a connecting shaft 5c, and the turbine 5a is rotated by the exhaust flow. The blower 5b is rotationally driven by the rotation of the turbine 5a, and supercharges the engine 1 with intake air through the intake passage 2.

Further, 6 is a fuel injection valve disposed upstream of the throttle valve 4 of the intake passage 2 and downstream of the blower 5b of the turbocharger 5, and 7 is a fuel injection control circuit for controlling the fuel injection amount of the fuel injection valve 6. , 8 is an air flow sensor for detecting the amount of intake air upstream of the blower 5b in the intake passage 2, and the detection signal of the air flow sensor 8 is input to the fuel injection control circuit 7, so that the amount of intake air is A fuel injection type fuel supply device 9 is configured to inject and supply the corresponding fuel to the intake passage 2.

On the other hand, 10 is an exhaust gas recirculation passage for recirculating a part of the exhaust gas from the exhaust system to the intake system. It opens into the exhaust passage 3, and the exhaust gas recirculation port 10b at the other end opens downstream from the throttle valve 4 of the intake passage 2, that is, downstream from the blower 5b of the turbocharger 5 and the fuel supply device 9 (fuel injection valve 6). There is. A recirculation control valve 11 is provided in the middle of the exhaust gas recirculation passage 10 to control the amount of exhaust gas recirculation by controlling the opening and closing of the exhaust gas recirculation passage 10 .

The recirculation control valve 11 is operated and controlled using intake negative pressure as an operation source, and has a shaft-shaped valve body 11 that opens and closes a valve seat 10c provided in the exhaust recirculation passage 10.
a, a housing 11b that slidably passes through and holds the valve body 11a, and a diaphragm 1 that connects and supports the other end (the upper end in the figure) of the valve body 11a.
1c, and an atmospheric pressure chamber 11d on the valve body 11a side (lower side) and a negative pressure chamber 11e on the opposite side (upper side), which are defined vertically in the figure by the diaphragm 11c.
and a spring 11f that is compressed in the negative pressure chamber 11e and urges the valve body 11a in the valve closing direction. Blower 5b and fuel supply device 9
It communicates with a negative pressure outlet 13 that opens immediately upstream of the fully closed position of the throttle valve 4 of the intake passage 2 in the intake passage 2 further downstream, and when the engine 1 is running except when idling, the intake negative pressure that acts on the negative pressure outlet 13 is When pressure is introduced into the negative pressure chamber 11e through the negative pressure passage 12, this intake negative pressure biases the diaphragm 11c upward in the figure against the biasing force of the spring 11f, thereby causing the valve body 11a to The opening operation is performed to open the exhaust gas recirculation passage 10 and perform exhaust gas recirculation.

Further, an atmosphere release passage 14 is branched from the middle of the negative pressure passage 12, and an atmosphere release port 14a at the other end of the atmosphere release passage 14 is provided with a pressure adjustment valve for controlling the operation of the recirculation control valve 11 according to the exhaust pressure. A device 15 is provided. The pressure regulating device 15 includes a valve body 15a that opens and closes the atmosphere opening port 14a, and a valve body 15a.
a diaphragm 15b that supports the diaphragm 15b, an exhaust pressure chamber 15c and an atmospheric pressure chamber 15d defined by the diaphragm 15b, and a spring that is compressed within the atmospheric pressure chamber 15d and biases the valve body 15a in the valve opening direction. 1
5e, and the exhaust pressure chamber 15c has an exhaust pressure passage 16.
The exhaust gas recirculation passage 10 is connected to the upstream side of the recirculation control valve 11 via the atmospheric pressure chamber 15d.
The atmosphere opening port 14a faces the atmospheric pressure chamber 1, and the atmospheric pressure chamber 1
5d is a communication path 18 with a filter member 17 interposed therebetween.
It is communicated with the atmosphere through. When the pressure (exhaust pressure) on the upstream side of the recirculation control valve 11 in the exhaust gas recirculation passage 10 increases, the diaphragm 15b is biased upward in the figure against the biasing force of the spring 15e due to the increase in pressure in the exhaust pressure chamber 15c. By closing the atmosphere opening port 14a with the valve body 15a, the intake negative pressure is directly introduced into the negative pressure chamber 11e of the recirculation control valve 11 without being diluted with the atmosphere, and the recirculation control valve 11 is opened and the exhaust gas is recirculated. will be held. As a result, the pressure (exhaust pressure) on the upstream side of the recirculation control valve 11
is lowered, and this pressure drop causes the diaphragm 15 to
b is biased downward by the urging force of the spring 15e and the atmosphere opening port 14a is opened by the valve body 15a, thereby reducing the negative pressure chamber 11e of the recirculation control valve 11.
The intake negative pressure acting on the filter member 17 is diluted with the atmosphere flowing in from the atmosphere opening 14a. As a result, the reflux control valve 11 closes and the pressure (exhaust pressure) on the upstream side of the reflux control valve 11 rises again. This operation is repeated to maintain the exhaust pressure almost constant, and Therefore, the exhaust gas recirculation rate is controlled to be substantially constant with respect to the exhaust pressure, that is, the amount of air taken into the engine 1.

As a feature of the present invention, a ball valve is provided in the middle of the atmosphere opening passage 14 to allow only the flow of air (atmosphere) from the atmospheric pressure chamber 15d of the pressure regulator 15 to the negative pressure passage 12 and the intake passage 2. A check valve 19 made of the following is provided.

Note that 20 is an annular space formed between the valve body 11a and the housing 11b of the reflux control valve 11, and the annular space 20 is connected to the valve through a communication passage 21 formed in the valve body 11a. It is configured to communicate with the exhaust gas recirculation passage 10 upstream of the recirculation control valve 11 when the body 11a is closed, and when the exhaust gas is not recirculated due to the closing operation of the recirculation control valve 11, it is connected to the annular space 20 through the communication passage 21. By introducing the exhaust pressure, it is balanced with the supercharging pressure acting on the downstream side of the recirculation control valve 11 in the exhaust recirculation passage 10, and thus the air-fuel mixture in the intake passage 2 is prevented from leaking from between the valve body 11a and the housing 11b. I'm trying to prevent it from coming out. Further, the atmospheric pressure chamber 11d of the recirculation control valve 11 is communicated with the exhaust passage 3 downstream of the turbine 5a of the turbocharger 5 via a communication passage 22, and the exhaust gas introduced into the annular space 20 is communicated with the valve body. Even if it leaks into the atmospheric pressure chamber 11d from between the housing 11a and the housing 11b,
A catalytic device (not shown) provided in the exhaust passage 3 enables purification.

Therefore, in the above embodiment, during supercharging by the operation of the turbo supercharger 5, the reflux control valve 11 is closed.
A negative pressure passage 12 for introducing intake negative pressure into the intake passage 2 is connected to the fuel supply device 9 downstream of the blower 5b of the turbocharger 5 in the intake passage 2 via a negative pressure outlet 13.
(Fuel injection valve 6) Since it opens downstream, the supercharging pressure (positive pressure) from the turbo supercharger 5 is transferred to the negative pressure outlet 1.
3 to the negative pressure passage 12, whereby the air-fuel mixture in the intake passage 2 flows from the negative pressure passage 12 to the atmosphere opening passage 14 to the atmospheric pressure chamber 1 of the pressure regulating device 15.
5d, but the atmosphere opening passage 14
When the check valve 19 provided in
It is possible to reliably prevent fuel leakage from the fuel to the atmosphere.

On the other hand, during exhaust gas recirculation, the check valve 19 opens due to the differential pressure between the intake negative pressure and the atmospheric pressure and allows air to flow from the pressure regulator 15 to the negative pressure passage 12. The atmosphere (air) for diluting the intake negative pressure freely flows into the negative pressure chamber 11e of the reflux control valve 11 through the atmosphere opening passage 14, and therefore the reflux control valve 1 is controlled by the pressure regulator 15.
1 operation control (exhaust recirculation control at a constant exhaust recirculation rate with respect to the intake air amount) can be performed accurately without any trouble, and therefore the pressure regulator 15 does not require an engine equipped with a supercharger. It is possible to ensure versatility with respect to engines.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but also includes various other modifications. For example, in the above embodiment, the blower 5b of the turbocharger 5 is connected to the fuel supply device 9 in the intake passage 2.
(The fuel injection valve 6) is provided upstream, but the positional relationship between the two does not matter. Further, although the negative pressure passage 12 is opened immediately upstream of the fully closed position of the throttle valve 4 in the intake passage 2, it may be always located downstream of the throttle valve 4. In short, it is applicable to the intake passage 2 downstream of the blower 5b of the turbocharger 5 and the fuel supply device 9, where the negative pressure passage 12 is opened at a position downstream of the throttle valve 4 at least in a specific operating range. be.

Furthermore, the present invention is applicable not only to the engine 1 equipped with the turbo supercharger 5 as in the above embodiment, but also to various types of supercharged engines, and for fuel injection type fuel as in the above embodiment. In addition to the supply device 9, it is also applicable to a vaporizer type device.

Further, in the above embodiment, the check valve 19 is interposed in the atmosphere opening passage 14, but the check valve 19 may be located in the middle of the passage from the pressure regulator 15 to the intake passage 2, and the same effect and effect as in the above embodiment can be achieved. can be played.

As explained above, according to the present invention, a negative pressure passage for introducing intake negative pressure to the recirculation control valve is opened to the intake passage downstream of the supercharger and the fuel supply device, and the recirculation control valve is discharged. In an exhaust gas recirculation system for a supercharged engine that is equipped with a pressure regulator that controls operation according to pressure, only air flows from the pressure regulator to the intake passage in a passage between the pressure regulator and the intake passage. By providing a check valve that allows this, it is possible to ensure good control accuracy and versatility of the pressure regulating device, while reliably preventing fuel leakage from the pressure regulating device of the supercharger to the atmosphere. It is effective.

[Brief explanation of the drawing]

The drawing is an overall schematic diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Engine, 2... Intake passage, 3... Exhaust passage, 4... Throttle valve, 5... Turbo supercharger, 5a... Turbine, 5b... Blower, 9...
...Fuel supply device, 10...Exhaust recirculation passage, 11...
... Reflux control valve, 12 ... Negative pressure passage, 13 ... Negative pressure outlet, 14 ... Atmospheric release passage, 15 ... Pressure regulator, 15a ... Valve body, 15b ... Diaphragm, 15c ... Exhaust pressure Chamber, 15d...Atmospheric pressure chamber, 1
5e...Spring, 16...Exhaust pressure passage, 19...
…non-return valve.

Claims (1)

[Scope of utility model registration request] The engine is equipped with a supercharger for supercharging intake air and a fuel supply device for supplying fuel to the intake passage, while using intake negative pressure as an operating source in the exhaust recirculation passage for recirculating exhaust gas from the exhaust passage to the intake passage. A negative pressure passage for introducing intake negative pressure into the recirculation control valve is opened in the intake passage downstream from the supercharger and fuel supply device, and the intake air in the negative pressure passage is In an exhaust gas recirculation system for a supercharged engine that is equipped with a pressure regulator that adjusts the pressure by diluting negative pressure with the atmosphere according to the exhaust pressure in the exhaust passage, the passage between the pressure regulator and the intake passage is An exhaust gas recirculation device for a supercharged engine, characterized by being provided with a check valve that only allows air to flow from a pressure regulator to an intake passage.