JPH04259653A - Rust preventive device for egr valve - Google Patents

Abstract

PURPOSE:To eliminate EGR clog of an engine using alcohol as main fuel resulting from rust generation by preventing the condensed water in the exhaust gas from attaching to an EGR valve or EGR passages. CONSTITUTION:A vacuum switching valve 35 interlocking with the ignition key of engine is installed on a pipeline 22 leading from an EGR port 28, which opens upstream of a throttle valve 5 in the suction passage 4, to a negative pressure working chamber 13 of an EGR valve 8. When the engine is stopped. the pipeline 22 is switched to the one 36, and the EGR valve is opened forcedly with the suction line negative pressure remaining in a surge tank 2, and then the condensed water attached to the EGR valve 8 and parts associate with it is sucked out to the suction passage.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an exhaust gas recirculation (abbreviated as EGR) system suitable for internal combustion engines using alcohol fuel, and in particular to an EGR system in an EGR system.
This invention relates to an EGR valve rust prevention device that suppresses the occurrence of rust in valves, EGR passages, etc.

0002

[Prior Art] Japanese Utility Model Application Publication No. 1-145973 describes EGR in an internal combustion engine using alcohol as the main fuel.
As an example of the system is described, gasoline engine Attempts are being made to install an EGR system similar to that of the above.

0003

[Problem to be solved by the invention] When alcohol is burned, it produces more water than gasoline, so in engines that use alcohol as the main fuel installed in FFVs, a large amount of water is contained in the recirculated exhaust gas. The moisture in the EGR
As a result of condensation and adhesion to parts such as valves and EGR passages,
Rust is likely to occur in those parts, and the rust causes EGR
This may cause so-called "EGR clogging" in which the passage is closed, and the necessary amount of EGR may not be secured, resulting in a reduction in the exhaust gas purification performance of the engine. The present invention addresses this problem and F
The problem to be solved by the invention is to provide a means for preventing condensed water from adhering to and remaining on the EGR valve etc. even in engines for FVs.

0004

[Means for Solving the Problems] As a means for solving the above-mentioned problems, the present invention provides a method for recirculating a part of exhaust gas from the exhaust passage to the downstream side of the throttle valve in the intake passage. An EGR passage that connects the intake passage on the downstream side of the throttle valve, an EGR port that opens to the intake passage on the upstream side of the throttle valve, and an EGR port that is provided in the middle of the EGR passage and that is connected to the intake negative pressure taken out at the EGR port. Based on the above, an EGR valve includes a valve body that controls the amount of exhaust gas to be recirculated, a pipe line that transmits intake negative pressure from the EGR port to a negative pressure working chamber of the EGR valve, and a pipe that transmits the intake negative pressure. The negative pressure operating chamber of the EGR valve is connected to the intake air on the upstream side of the throttle valve when the engine shifts from a running state to a stopped state in conjunction with an ignition key of the engine. At the same time, the EGR port that opens into the passage is shut off, and is communicated with the intake passage on the downstream side of the throttle valve, so that the intake negative pressure on the downstream side of the throttle valve is transferred to the negative pressure working chamber of the EGR valve. The present invention provides an EGR valve rust prevention device for an EGR system, characterized in that a vacuum switching valve is provided to forcefully open the EGR valve.

[0005]

[Operation] When the ignition key is ON and the engine is running, the EGR port is connected to the negative pressure operating chamber of the EGR valve by a pipe, and the EGR valve is activated depending on the intake negative pressure upstream of the throttle valve. The opening degree changes and E
Exhaust gas is recirculated from the GR passage to the intake passage downstream of the throttle valve at a substantially constant EGR rate.

[0006]
When the engine is stopped, the vacuum switching valve is activated in conjunction with the ignition key being turned OFF.
Switch the conduit to the negative pressure working chamber of the EGR valve from the EGR port to the intake passage downstream of the throttle valve. As a result, strong negative intake pressure acts on the intake passage downstream of the throttle valve while the engine rotates due to inertia until it completely stops, or remains in the intake passage for a while even after the engine has stopped. Intake negative pressure acts on the negative pressure working chamber and EG
The R valve is forcibly opened, and the condensed water that has accumulated in the valve chamber of the EGR valve, the EGR passage, etc. is sucked out into the intake passage by the intake negative pressure and is removed from the EGR system. Therefore, occurrence of rust due to condensed water and "EGR clogging" are prevented.

[0007]

Embodiment An embodiment of the EGR system of the present invention is shown in FIG. In the figure, 1 shows a part of the intake manifold that is connected to the intake valve of the engine (not shown), and the upstream side of the intake manifold is connected to the air intake part of an air cleaner or the like (not shown) via the surge tank 2 and the throttle body 3. . The throttle body 3 is provided with a throttle valve 5 that controls opening and closing of the intake passage 4 . Reference numeral 6 designates a part of an exhaust manifold connected to an exhaust valve of an engine (not shown), and an EGR passage 7 that connects it to the surge tank 2 of the intake passage 4 has an EGR valve that controls the amount of exhaust gas recirculated.
A valve 8 is provided.

The EGR valve 8 is a negative pressure operated type, and a valve body 10 attached to a diaphragm 9 is connected to a valve seat opening 12 of an EGR valve chamber 11 that constitutes a part of the EGR passage 7.
The diaphragm 9 is arranged to open and close, and one space of the diaphragm 9 is a negative pressure working chamber 13, and a compression spring 14 provided therein urges the valve body 10 toward the valve seat opening 12. The valve is closed. Exhaust manifold 6
and the EGR passage 7 between the valve seat 12 of the EGR valve chamber 11
An exhaust pressure chamber 16 is formed by a throttle 15 .

An EGR vacuum modulator 17 is provided to adjust the control negative pressure that controls opening and closing of the EGR valve 8, and its internal space is divided into a lower exhaust pressure chamber 19 and an upper pressure regulating chamber 20 by a diaphragm 18. The exhaust pressure chamber 19 is communicated with the exhaust pressure chamber 16 through a conduit 21. The pressure regulating chamber 20 opens into the intake passage 4 on the upstream side of the throttle valve 5 through a conduit 22 .

The opening provided in the wall of the intake passage 4 will be referred to as a pressure regulating port 23. The diaphragm 18 is provided with a valve element 24, and a negative pressure pipe 26 having a valve seat opening 25 that is opened and closed by the valve element 24 passes through the EGR vacuum modulator 17, and one end of the negative pressure pipe 26 is connected to the pipe line 2.
7, the intake passage 4 is connected to an EGR port 28 which opens slightly downstream of the pressure regulating port 23 on the upstream side of the throttle valve 5, and the other end of the negative pressure pipe 26 is connected to the pipe line 2.
9 communicates with the thermovalve 30. Pressure control chamber 2
0 is provided with a compression spring 31, which biases the valve body 24 in a direction to separate it from the valve seat opening 25. The pressure regulating chamber 20 communicates with the atmosphere via a throttle and an air filter 32 (not shown).

The thermovalve 30 is installed in the cooling water sleeve 33 of the engine, and opens when the temperature of the cooling water exceeds a predetermined value.
When the temperature is lower than that, the valve closes. Therefore,
When the cooling water temperature is above a predetermined temperature, the pipe line 29 extending from the EGR vacuum modulator 17 is communicated with the negative pressure operating chamber 13 of the EGR valve 8 through the pipe line 34.

The above configuration is substantially the same as the EGR system that the present applicant has conventionally implemented in gasoline engines. A pressure regulating port 23 and an EGR port 28 that open on the upstream side of the throttle valve 5 in the passage 4, and an EGR
A vacuum switching valve 35, which will be described in detail later, is provided in the pipe line 22 and the pipe line 27 that communicate with the vacuum modulator 17, and the vacuum switching valve 35 and the surge tank 2 are connected to the pipe line 3.
It has a special configuration in which it communicates through 6.

The structure and operation mode of the vacuum switching valve 35 are shown in an enlarged manner in FIGS. 2 and 3, and the operation state peculiar to the present invention corresponding to FIG. 3 is shown in FIG.
is shown for the entire EGR system. The vacuum switching valve 35 in the illustrated embodiment is
It consists of a cylindrical valve body 37, a spool-shaped valve body 38 that slides within the cylindrical valve body 37, and an actuator 39 that operates the valve body 38. As mentioned above, the EG is connected to one side of the wall surface of the valve body 37 by a part 27a of the pipe line 27.
A port 40 that communicates with the R port 28 and a port 4 that communicates with the pressure regulation port 23 through a portion 22a of the conduit 22.
1 is opened, and a part 2 of the conduit 27 is opened on the other side.
7b to the negative pressure line 26 of the EGR vacuum modulator 17 and a portion 22 of the line 22.
A port 43 communicating with the pressure regulation chamber 20 of the EGR vacuum modulator 17 is opened by b. A port 45 is opened on one end surface 44 of the valve body 37 and is connected to the pipe line 3.
6.

The actuator 39 provided on the other end surface 46 of the valve body 37 of the vacuum switching valve 35 electromagnetically engages the spool-shaped valve body 38.
It has a solenoid coil that operates the engine, and is electrically energized in conjunction with the engine's ignition key (not shown). That is, FIG. 2 shows an ON state in which the engine is driven, and FIG. 3 shows an OFF state in which the engine is stopped. When the spool-shaped valve body 38 is in the key ON state (Fig. 2),
It includes a passage 47 that communicates between ports 41 and 43, and a passage 48 that also communicates between ports 40 and 42, and when the key is OFF (FIG. 3), the above communication is cut off, and instead, ports 42 and 42 communicate with each other. 43 and a passageway 49 communicating with port 45.

When the alcohol fuel internal combustion engine equipped with the EGR system of the illustrated embodiment is operated, the intake passage 4
A fuel tank (not shown) is inserted into the intake air taken into each cylinder of the internal combustion engine through the throttle body 3, surge tank 2, and intake manifold 1 that constitute the engine, in the middle of the intake passage 4, or in the combustion chamber of the engine. Alcohol fuel (methanol and ethanol) mixed with a predetermined amount of gasoline is injected from the engine, mixes with intake air, is compressed and ignited in the combustion chamber of the engine, and burns to drive the internal combustion engine. Internal combustion engines that use alcohol fuel generally emit fewer nitrogen oxides than engines that use only gasoline, but depending on operating conditions, the proportion of alcohol fuel can be reduced.
If the proportion of gasoline is increased by that amount, the amount of nitrogen oxide emissions will be too large to be ignored, so EG
R creates a need to reduce emissions.

As mentioned above, assuming that the vacuum switching valve 35 and the pipe line 36 are not provided in the EGR system shown in FIG. Since the configuration is substantially the same as the EGR system in
In the illustrated embodiment, in the normal operating state of the internal combustion engine with the ignition key turned on, the actuator 39 of the vacuum switching valve 35 pushes down the spool-shaped valve body 38, as shown in FIG. In a state where it is in close contact with one end surface 44, the conventional E
It operates in the same way as the GR system.

That is, the passage 47 of the spool-shaped valve body 38 connects the pressure regulation port 23 of the throttle body 3 and the pressure regulation chamber 20 of the EGR vacuum modulator 17 by communicating the pipe line 22a and the pipe line 22b. In addition, the passage 48 is
The pipe line 27a and the pipe line 27b are communicated to connect the EGR port 28 of the throttle body 3 and the negative pressure pipe 26 of the EGR vacuum modulator 17, thereby completing a normal EGR system. At this time, communication between the surge tank 2 and the vacuum switching valve 35 is cut off, so the negative pressure in the surge tank 2 does not affect the normal operation of the EGR system.

As is well known, in a normal EGR system, the difference between the pressure in the valve chamber 11 of the EGR valve 8 and the pressure in the exhaust pressure chamber 16 communicating with the exhaust manifold 6 via the throttle 15 is determined. By maintaining the EGR rate substantially constant, the EGR rate is maintained substantially constant. However, during idling when the throttle valve 5 is fully closed, the intake negative pressure does not substantially act on the EGR port 28 and the pressure regulating port 23 provided in the throttle body 3, and the EGR vacuum modulator 1
Since the pressure regulating chamber 20 in the EGR valve 7 as well as the negative pressure operating chamber 13 of the EGR valve 8 have a pressure close to atmospheric pressure, the valve body 10 closes the valve seat opening 12 by the compression spring 14, and the EGR valve 8 closes the valve seat opening 12.
The R passage 7 is closed and the EGR operation is stopped. Furthermore, when the engine is not sufficiently warmed up, the thermovalve 30, which operates depending on the cooling water temperature, is not opened and the EG
Since intake negative pressure is not supplied to the negative pressure operating chamber 13 of the R valve 8, the EGR action is also stopped.

When the throttle valve 5 opens slightly and negative intake pressure acts on the EGR port 28, the thermovalve 30 is open in the warm-up state when the engine cooling water temperature is higher than a predetermined value, so the intake air is Negative pressure is provided by pipe 27, E
Negative pressure pipe 26 and pipe line 2 of GR vacuum modulator 17
9, thermo valve 30, the negative pressure working chamber 13 of the EGR valve 8 is supplied through the pipe 34, and the compression spring 14
The diaphragm 9 is moved against this, and the valve body 10 is opened by an amount corresponding to the magnitude of the intake negative pressure. The magnitude of this intake negative pressure is not the intake negative pressure of the EGR port 28 itself, but the intake negative pressure that enters the pressure regulation chamber 20 of the EGR vacuum modulator 17 from the pressure regulation port 23, although small, and the intake negative pressure that passes through the throttle from the air filter 32. The opening degree at which the diaphragm 18 opens the valve seat port 25 is determined by the balance of the exhaust pressure entering the exhaust pressure chamber 19 from the pipe line 21 with respect to the pressure in the pressure regulating chamber 20 formed from the entering atmospheric pressure. The intake negative pressure of the EGR port 28 becomes a value that is somewhat weakened. Therefore, the exhaust gas from the exhaust manifold 6 enters the EGR passage 7 through the valve seat opening 12, which is opened by an amount corresponding to the intake negative pressure in the negative pressure working chamber 13 of the EGR valve 8.
It mixes with the intake air in the surge tank 2 and is supplied again to the combustion chamber of the engine, lowering the combustion temperature and reducing the amount of nitrogen oxide emissions.

When the throttle valve 5 opens further and approaches high-load operation, the intake negative pressure at the pressure regulation port 23 also increases, so the pressure in the pressure regulation chamber 20 of the EGR vacuum modulator 17 decreases, and the diaphragm 18 closes the valve. Since the body 24 approaches the valve seat opening 25 against the compression spring 31 and tries to close it, the intake negative pressure of the EGR port 28 is applied almost as is to the negative pressure operating chamber 13 of the EGR valve 8, and the EGR The valve body 10 of the valve 8 widens the valve seat opening 12, and a large amount of exhaust gas flows from the exhaust manifold 6 through the EGR passage 7 into the surge tank 2, thereby performing high-rate EGR. In this way, exhaust gas recirculation is performed at a flow rate roughly proportional to the intake flow rate, and a substantially constant EGR rate is achieved.

In the embodiment of FIG. 1, EGR port 2
A vacuum switching valve 35 that operates in conjunction with the ignition key is inserted in the middle of the pipe line 27 and pipe line 22 for transmitting negative intake pressure from the pressure adjustment port 23 and the EGR vacuum modulator 17. Since the intake negative pressure of the surge tank 2 downstream of the throttle valve 5 can be selectively supplied to the EGR vacuum modulator 17, when the ignition key is turned OFF to stop the engine, the vacuum switching valve 35 operates as shown in FIG. The state changes to the state shown in FIG. This can be done, for example, by configuring the spool-shaped valve body 38 to be pulled up to the position shown in FIG. 3 by an internal compression spring (not shown) when the electromagnetic bias of the actuator 39 is released. Can be done.

In the state shown in FIG. 3, the spool-shaped valve body 38 blocks the communication of the pipe line 22a and the pipe line 27a with the EGR vacuum modulator 17, and acts on the EGR port 28 and the pressure regulation port 23 upstream of the throttle valve 5. (However, since the throttle valve 5 closes rapidly when the internal combustion engine is stopped, the intake negative pressure virtually disappears at its upstream position.) , the suction negative pressure in the surge tank 2, which increases rapidly when the throttle valve 5 closes, is transferred to the conduit 36 and the vacuum switching valve 35.
through the port 45, the space 50, and the passage 49 of the conduit 22b.
and the pipe line 27b, and furthermore, the negative pressure pipe 26 of the EGR vacuum modulator 17, the pipe line 29, and the thermovalve 3.
0, it is applied to the negative pressure working chamber 13 of the EGR valve 8 via the conduit 34, and the valve body 10 is instantaneously fully opened. FIG. 4 shows this state.

[0023] Even if the ignition key is turned off,
It takes a considerable amount of time for the crankshaft to stop, and negative intake pressure remains downstream of the throttle valve 5 for some time after the crankshaft stops, so the above-mentioned special operation is not performed during this time. When this occurs, a large amount of exhaust gas flows from the exhaust manifold 6 through the valve body 10 of the EGR valve 8 to the EGR passage 7, and then passes through the surge tank 2 and intake manifold 1 and is sucked into the combustion chamber of the engine again. , until then the valve chamber 11 of the EGR valve 8
The condensed water accumulated in the engine and EGR passage 7 is carried away by this large amount of strong exhaust gas flow to the surge tank 2, intake manifold 1, and further to the combustion chamber of the engine.
It does not remain in the GR valve chamber 11, EGR passage 7, etc. Therefore, the EGR passage 7 and EGR valve 8 are affected by condensed water.
etc. will not rust and block the passage with foreign matter, or corrode and become unusable.

[0024] Conveniently, since the above-mentioned special operation is performed when the engine is stopped, by turning the ignition key OFF, fuel injection to the engine is also stopped at the same time, and the engine is stopped due to inertia. When the exhaust gas scavenges the EGR valve chamber 11, EGR passage 7, etc. as described above while the engine continues to rotate, and while the intake negative pressure remains even after the rotation stops, most of the exhaust gas Since it is only air and the amount of fuel, combustion gas, moisture, etc. contained in it is small, the purging effect of condensed water by exhaust gas at this time is extremely high. There is.

After the ignition key is turned OFF and the condensed water is purged by the operation described above, when the rotation of the engine due to inertia also stops, the throttle valve 5
The negative pressure operating chamber 13 of the EGR valve 8 gradually approaches atmospheric pressure due to air entering the surge tank 2 through the gap between the two and air flowing from the air filter 32 of the EGR vacuum modulator 17, and the valve body 10 of the EGR valve 8 gradually approaches atmospheric pressure. The valve seat opening 12 is closed and the above operation is completed. When the engine is started again, the vacuum switching valve 35 is switched to the position shown in FIG. 3 by turning the ignition key ON.
The state changes from the state shown in FIG. 2 to the state shown in FIG. 2, which has the same configuration as a normal EGR system, and the EGR effect is fully exhibited.

The throttle body 3 of the illustrated embodiment is EG
In addition to the R port 28, a pressure regulating port 23 is provided, and accordingly, the vacuum switching valve 35 is connected to the passage 4.
In addition to 9, it has two passages 47 and 48, and
The EGR vacuum modulator 17 also has a corresponding configuration, but the present invention is not limited to such a structure, and even if there is only one port for taking out the intake negative pressure, the EGR port 28, the EGR vacuum modulator 17 and the negative pressure of the EGR valve 8 Pressure working chamber 1
The present invention can be applied by providing a vacuum switching valve 35 having a passage 48 and a passage 49 in the middle of a conduit connecting the two.

[0027]

[Effects of the Invention] By carrying out the present invention, even when the exhaust gas contains a large amount of moisture, such as in an engine that uses alcohol fuel for FFV, the EGR system can be prevented from rusting due to condensed water. There is no need to worry about "EGR clogging." Therefore, normal operation of the EGR system is ensured, and exhaust purification performance does not deteriorate, the catalyst does not deteriorate, and drivability does not deteriorate.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view showing the structure and one operating state of an embodiment of a vacuum switching valve, which is a main part of the present invention.

FIG. 3 is a sectional view showing another operating state similar to FIG. 2;

FIG. 4 is an overall configuration diagram showing another operating state similar to FIG. 1;

[Explanation of symbols]

1...Intake manifold 5...Throttle valve 6...Exhaust manifold 7...EGR passage 8...EGR valve 10... Valve body 13... Negative pressure working chamber 17...EGR vacuum modulator 21, 22, 27, 36...Pipe line 28...EGR port 35...Vacuum switching valve 38...Spool-shaped valve body

Claims (1)

[Claims] 1. In order to recirculate a portion of exhaust gas from the exhaust passage to the downstream side of the throttle valve in the intake passage, an EGR passage connecting the exhaust passage and an intake passage downstream of the throttle valve; an EGR port that opens into the intake passage on the upstream side of the valve;
an EGR valve that is provided in the middle of the R passage and includes a valve body that controls the amount of exhaust gas to be recirculated based on the intake negative pressure taken out at the EGR port;
A conduit for transmitting intake negative pressure from the GR port to the negative pressure working chamber of the EGR valve, and a conduit for transmitting the intake negative pressure are provided in the middle of the pipe, and the engine is operated in conjunction with the ignition key of the engine. When moving from the EG to the stop state, the EG
The negative pressure working chamber of the R valve is shut off from the EGR port that opens into the intake passage on the upstream side of the throttle valve, and at the same time it is communicated with the intake passage on the downstream side of the throttle valve, so that the EGR valve EGR valve rust prevention in an EGR system, characterized in that a vacuum switching valve is provided to forcefully open the EGR valve by applying the intake negative pressure on the downstream side of the throttle valve to the negative pressure operating chamber. Device.