JP2001280143A - Exhaust gas scavenging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent exhaust gas from reversely flowing in an intake passage when an engine is stopped, and prevent starting failure caused by exhaust gas which is stagnated in the intake passage. SOLUTION: A scavenging air generating means is disposed so as to generate air for scavenging the intake passage of the engine, a scavenging air supplying passage is disposed so as to supply scavenging air generated by the scavenging air generating means to the intake passage, and a control means for controlling the scavenging air generating means is disposed so as to supply scavenging air to the intake passage when an ignition switch of the engine is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas scavenging device, and more particularly to a device for preventing exhaust gas from flowing back into an intake passage when an engine is stopped, thereby preventing a starting failure due to exhaust gas remaining in the intake passage. Exhaust gas scavenging device.

[0002]

2. Description of the Related Art Some engines mounted on vehicles and the like are provided with an injector as a measure against problems such as harmful exhaust components and fuel consumption rate. FIG. 8 shows such an engine. 8, 202 is an engine, 204 is a piston, 206 is a combustion chamber, 208 is an intake port, 210 is an exhaust port, 212 is an intake valve, 2
14 is an exhaust valve.

[0003] The engine 202 includes an air cleaner 21.
An intake passage 218 communicating from the intake port 208 to the intake port 208 is provided, and a throttle valve 220 is provided in the intake passage 218. Further, the engine 202 has an exhaust passage 222 communicating with the exhaust port 210. Engine 202
Is provided with an injector 224 for injecting and supplying fuel. The injector 224 is provided in the intake passage 218 so as to face the combustion chamber 206.

As such an engine, Japanese Utility Model Laid-Open No.
There is one disclosed in Japanese Patent No. 6152. An engine having an air assist injector that promotes atomization of fuel by using an air jet is disclosed in this publication. A pressurized pump is provided in an air passage for assist air that supplies assist air to the air assist injector. And a valve and an orifice that are opened when the pressurizing pump is stopped are provided in a bypass passage that bypasses the pressurizing pump.

Further, as a device for supplying auxiliary air to an engine, there is one disclosed in Japanese Patent Application Laid-Open No. 6-221176. This publication discloses that in a high-load region including a full throttle opening region in a low-speed region of a rotary engine, replacement air is supplied to replace exhaust gas in an exhaust working chamber with fresh air, and exhaust gas to an intake working chamber is provided. Gas is prevented from being carried in, while port air is supplied in the low load range to improve combustion stability.

[0006]

Incidentally, in an engine having an intake / exhaust valve, there are times when the open states of the intake / exhaust valves overlap during operation. At the position where the valve timings of the open state of the intake and exhaust valves overlap, the exhaust port, the combustion chamber, and the intake port communicate with each other.

However, if the valve timing of the intake / exhaust valves is stopped at the overlap position when the engine is stopped, the exhaust port, the combustion chamber, and the intake port are in communication. Due to the pressure difference, the exhaust gas flows backward to the intake port side, and the exhaust gas including the intake passage is filled with the exhaust gas.

For this reason, the engine has a disadvantage that the oxygen concentration in the engine is reduced due to the exhaust gas stagnating in the intake system, and the oxygen in the intake air to be sucked into the combustion chamber at the next start is insufficient, resulting in poor starting. is there.

[0009]

In order to eliminate the above-mentioned disadvantages, the present invention provides scavenging air generating means for generating scavenging air for scavenging an intake passage of an engine. A scavenging air supply passage for supplying scavenging air generated by the means to the intake passage; and controlling the scavenging air generating means to supply the scavenging air to the intake passage when an ignition switch of the engine is turned off. A control means is provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The exhaust gas scavenging device of the present invention
A scavenging air generating means and a scavenging air supply passage are provided, and the control means controls the scavenging air generating means so as to supply scavenging air to the intake passage when an ignition switch of the engine is turned off, so that the air intake and the scavenging air are supplied. Even if the engine stops and the exhaust gas flows back to the intake port when the valve timing of the exhaust valve overlaps, the scavenging air can prevent the exhaust gas from flowing back to the intake port. Exhaust gas can be prevented from being filled.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention. In FIG. 4, 2 is an engine, 4 is a cylinder block, 6 is a cylinder head, 8 is a head cover, 1
0 is a piston, 12 is a combustion chamber, 14 is an intake port, 16
Is an exhaust port, 18 is an intake valve, and 20 is an exhaust valve.

The engine 2 has an intake passage 24 communicating from the air cleaner 22 to the intake port 14 as an intake system, and a throttle valve 26 provided in the intake passage 24. The engine 2 has an exhaust port 16 as an exhaust system.
An exhaust passage 28 communicating with the exhaust passage 28 is provided, and a catalytic converter 30 is provided in the middle of the exhaust passage 28. In addition, Engine 2
Is a ventilation system, and the inside of the head cover 8 and the air cleaner 22
And a first blow-by gas passage 32 communicating with the intake passage 24 in the head cover 8 and the downstream side of the throttle valve 26.
And a second blow-by gas passage 34 communicating the
A V-valve 36 is provided.

The engine 2 has an air assist injector 38 in the intake passage 24 so as to be directed toward the combustion chamber 12. The air assist injector 38 is provided in communication with a fuel tank 42 through a fuel supply passage 40. A fuel pump 44 for supplying fuel to the fuel supply passage 40 is provided in the fuel tank 42. The fuel tank 42 is provided in communication with a canister 48 through an evaporation passage 46. The canister 48 is provided in communication with the intake passage 24 on the upstream side of the throttle valve 26 through a purge passage 50.

The air assist injector 38 includes:
The other end of an air passage 52 for the assist air having one end opened upstream of the throttle valve 26 is provided in communication therewith. An air assist control valve 54 for controlling the assist air supplied to the air assist injector 38 is provided in the middle of the assist air air passage 52.

Further, the engine 2 is provided with a bypass passage 56 that connects the intake passage 24 on the upstream side and the downstream side of the throttle valve 26. An idle control valve 58 for controlling the engine speed during idling is provided in the middle of the bypass passage 56.

The engine 2 is provided with a pressure sensor 60 for detecting the intake pressure on the downstream side of the throttle valve 26, and a throttle sensor 6 for detecting the opening degree of the throttle valve 26.
2, a water temperature sensor 64 for detecting the temperature of the cooling water, an O2 sensor 66 for detecting the oxygen concentration of the exhaust gas, and a crank angle sensor 68 for detecting the crank angle and the engine speed.

The air assist injector 38, the fuel pump 44, the air assist control valve 52, and the idle control valve 58
The pressure sensor 60, the throttle sensor 62, the water temperature sensor 64, the O2 sensor 66, and the crank angle sensor 68 are provided so as to be connected to control means 72 constituting an exhaust gas scavenging device 70. The control means 72 includes a main switch 74,
A battery 78 is connected via a fuse 76. The control means 72 controls a fuel injection amount, an assist air amount, an ignition timing, a bypass air amount, and the like based on a signal input from the pressure sensor 60 or the like.

The engine 2 is provided with an exhaust gas scavenging device 70 as shown in FIG. Exhaust gas scavenging device 7
0 is a scavenging air generating means 80 such as a pump or a blower for generating scavenging air for scavenging the intake passage 26 of the engine 2.
And a scavenging air supply passage 82 for supplying scavenging air generated by the scavenging air generating means 80 to the intake passage 26.
Is provided.

The scavenging air supply passage 82 is used for supplying auxiliary air to the intake passage 24, for an auxiliary air supply passage already provided in the engine 2, for example, for assist air for supplying assist air to the air assist injector 38. It is provided connected to the air passage 52. In a portion where the air passage 52 for assist air and the air supply passage 82 for scavenging are connected,
A switching valve 84 is provided.

Thus, the air passage 52 for the assist air is provided.
Is divided into an upstream assist air air passage 52-U upstream of the switching valve 84 and a downstream assist air air passage 52-L downstream of the switching valve 84. Switching valve 8
4 selectively communicates the upstream assist air air passage 52-U and the scavenging air supply passage 82 with respect to the downstream assist air air passage 52-L, and supplies auxiliary air to the intake passage 24. And either scavenging air or
The switching operation is performed by the control means 72.

The scavenging air generator 80 and the switching valve 84 are connected to the controller 72. Control means 72
Is provided with an ignition switch 86 of the engine 2 connected thereto. The control means 72 controls the scavenging air generation means 80 so as to supply scavenging air to the intake passage 26 when the ignition switch 86 of the engine 2 is turned off.

At this time, when the ignition switch 86 of the engine 2 is turned off, the control means 72 controls the air assist injector 38 and the air so as to supply scavenging air from the air assist injector 38 to the intake passage 24 for a predetermined scavenging time Taa. The assist control valve 54 is turned on, the fuel pump 44 is turned off, the scavenging air generating means 80 is turned on, and the scavenging air supply passage 82 communicates with the downstream assist air air passage 52-L. The switching operation of the switching valve 84 is performed.

Next, the operation of the first embodiment will be described.

As shown in FIG. 1, when the control is started by the control means 72, the exhaust gas scavenging device 70 (2)
00), it is determined whether or not the ignition switch 86 is off (202). If this determination (202) is NO, air assist control for normal operation is performed (204),
The process returns to the judgment (202).

In the air assist control (204) of the normal operation, the switching valve 84 is switched so that the upstream assist air air passage 52-U communicates with the downstream assist air air passage 52-L. The air assist control valve 54 is turned on to supply assist air from the intake passage 24 upstream of the throttle valve 26 to the air assist injector 38.

Thus, during normal operation, fuel and assist air are mixed by the air assist injector 38 and injected into the intake port 14.

If the judgment (202) is YES, as shown in FIG. 2, the scavenging air generating means 80 is turned on (206), and the scavenging air is supplied to the downstream assist air passage 52-L. The switching valve 8 communicates with the supply passage 82.
4 is switched (208), the on-operation of the air assist control valve 54 and the air assist injector 38 is maintained so as to supply scavenging air from the scavenging air generating means 80 to the air assist injector 38 (210), and fuel The fuel pump 44 is turned off so as to stop the supply (21).
2).

Thus, when the ignition switch 86 is turned off, the scavenging air is injected from the air assist injector 38 to the intake port 14.

Next, it is determined whether the scavenging time Taa has elapsed (214). If this determination (214) is NO, this determination is repeated. This judgment (214) is YE
In the case of S, the switching valve 84 is switched so that the upstream assist air air passage 52-U communicates with the downstream assist air air passage 52-L, and the scavenging operation is performed to stop the supply of the assist air. The air generating means 80 is turned off, the air assist control valve 54 is turned off, and the injection of the scavenging air from the air assist injector 38 is stopped and ended (216).

As shown in FIG. 2, when the ignition switch 86 of the engine 2 is turned off, the exhaust gas scavenging device 70 supplies scavenging air from the air assist injector 38 to the intake passage 26 by the control means 72, as shown in FIG. Scavenging air generating means 8 so as to supply only scavenging time Taa
0 is turned on, and the switching valve 84 is switched so that the scavenging air supply passage 82 communicates with the downstream assist air air passage 52-L.

As a result, the exhaust gas scavenging device 70 stops the engine 2 at the position where the valve timings of the intake and exhaust valves 18 and 20 overlap, and the exhaust gas is discharged to the intake port 1.
The air assist injector 38
The backflow of exhaust gas can be prevented by the scavenging air injected from the exhaust gas, and the exhaust system including the intake passage 24 can be prevented from being filled with the exhaust gas.

Therefore, the exhaust gas scavenging device 70
It is possible to avoid a decrease in oxygen concentration due to exhaust gas staying in the intake passage 24 when the engine 2 is stopped, to reliably start the engine 2 at the next start, and to prevent poor starting due to exhaust gas. it can.

The exhaust gas scavenging device 70 utilizes the assist air air passage 52, which is an existing auxiliary air supply passage in the engine 2, to supply the assist air to the intake passage 24. Since the scavenging air supply passage 82 is connected to the air air passage 52 and provided, it is possible to cope with a small change on the engine 2 side, and the assist air air passage 52 is opened toward the combustion chamber 14. Connected to the air-assist injector 38, the scavenging air can be injected toward the combustion chamber 12, the backflow of exhaust gas can be effectively prevented, and the exhaust gas is effectively directed to the combustion chamber 14 side. Can be scavenged.

FIGS. 5 to 7 show a second embodiment. As shown in FIG. 7, the exhaust gas scavenging device 70 of the second embodiment is provided with scavenging air generating means 80 for generating scavenging air for scavenging the intake passage 14 of the engine 2. The generated scavenging air is supplied to the intake passage 14.
The scavenging air supply passage 82 is connected to the assist air air passage 52 which is an auxiliary air supply passage already provided in the engine 2. In a portion where the assist air air passage 52 and the scavenging air supply passage 82 are connected, an upstream assist air air passage 52-U and a scavenging air supply passage are provided with respect to the downstream assist air air passage 52-L. A switching valve 84 for selectively communicating with the valve 82 is provided.

The scavenging air generator 80 and the switching valve 84 are connected to the controller 72. Control means 72
Is connected to a crank angle sensor 68 of the engine 2 and an ignition switch 86. Control means 72
When the rotation of the engine 2 is stopped after the ignition switch 86 of the engine 2 is turned off and the engine rotation speed detected by the crank angle sensor 68 is zero, the intake passage 2
Scavenging air generating means 80 so as to supply scavenging air to
Control.

At this time, after the ignition switch 86 of the engine 2 is turned off,
When the rotation of the fuel pump 4 is stopped, the air assist injector 38 and the air assist control valve 54 are turned on so that the scavenging air is supplied from the air assist injector 38 to the intake passage 24 for a predetermined scavenging time Taa.
4 to turn off the scavenging air generating means 80 and to switch the scavenging air supply passage 82 to the downstream assist air air passage 52-L.
Is switched.

Next, the operation of the second embodiment will be described.

As shown in FIG. 5, when the control is started by the control means 72 as shown in FIG.
00), it is determined whether or not the ignition switch 86 is off (302). When the determination (302) is NO, the air assist control of the normal operation is performed (304),
The process returns to the judgment (302).

In the air assist control (304) in the normal operation, the switching valve 84 is switched so that the upstream assist air air passage 52-U communicates with the downstream assist air air passage 52-L. The air assist control valve 54 is turned on to supply assist air from the intake passage 24 upstream of the throttle valve 26 to the air assist injector 38.

Thus, during normal operation, fuel and assist air are mixed by the air assist injector 38 and injected into the intake port 14.

If the judgment (302) is YES, it is judged whether or not the engine speed detected by the crank angle sensor 68 is zero (306). This judgment (30
If 6) is NO, this determination is repeated.

If the determination (306) is YES, the scavenging air generating means 80 is turned on (308), and the scavenging air supply passage 82 communicates with the downstream assist air air passage 52-L. The switching valve 84 is operated to switch (3
10) The on-operation of the air assist control valve 54 and the air assist injector 38 is maintained so that the scavenging air is supplied from the scavenging air generating means 80 to the air assist injector 38 (312), and the fuel supply is stopped to stop the fuel supply. The pump 44 is turned off (314).

Thus, when the engine 2 is stopped after the ignition switch 86 is turned off, the scavenging air is injected from the air assist injector 38 to the intake port 14.

Next, it is determined whether the scavenging time Taa has elapsed (316). If this determination (316) is NO, this determination is repeated. This judgment (316) is YE
In the case of S, the switching valve 84 is switched so that the upstream assist air air passage 52-U communicates with the downstream assist air air passage 52-L, and the scavenging operation is performed to stop the supply of the assist air. The air generating means 80 is turned off, the air assist control valve 54 is turned off, and the injection of the scavenging air from the air assist injector 38 is stopped and ended (318).

As described above, the exhaust gas scavenging device 70 controls the scavenging air from the air assist injector 38 into the intake passage 24 by the control means 72 after the ignition switch 86 of the engine 2 is turned off and the engine 2 stops rotating. The switching valve 84 is switched to turn on the scavenging air generating means 80 and supply the scavenging air supply passage 82 to the downstream assist air air passage 52-L so as to supply the gas for the predetermined scavenging time Taa. Operate.

As a result, the exhaust gas scavenging device 70 stops the engine 2 at the position where the valve timings of the intake and exhaust valves 18 and 20 overlap, and the exhaust gas is exhausted to the intake port 1.
The air assist injector 38
The backflow of exhaust gas can be prevented by the scavenging air injected from the exhaust gas, and the exhaust system including the intake passage 24 can be prevented from being filled with the exhaust gas.

Therefore, the exhaust gas scavenging device 70
It is possible to avoid a decrease in the oxygen concentration of the air present in the intake passage 24 when the engine 2 is stopped, to reliably start the engine 2 at the next start, and to prevent poor starting due to exhaust gas. .

Further, the exhaust gas scavenging device 70 can cope with a small change on the engine 2 side by providing the scavenging air supply passage 82 connected to the existing assist air air passage 52 in the engine 2. The scavenging air can be injected toward the combustion chamber 12 from the air-assist injector 38 that opens toward the combustion chamber 14, and the backflow of the exhaust gas can be effectively prevented. The side can be effectively scavenged.

Further, in the exhaust gas scavenging device 70, since the scavenging air is supplied after the rotation of the engine 2 is stopped, the scavenging air supplied to the rotation of the engine 2 affects the scavenging air. Therefore, the generation of vibrations and the like can be prevented, and the scavenging air is supplied after the rotation of the engine 2 is stopped, compared to when the ignition key 86 of the first embodiment is turned off. The amount of scavenging air can be reduced, and scavenging air generating means 8
0 can be reduced in size.

In the above-described embodiment, the scavenging air is supplied when the ignition key 86 is turned off or when the rotation of the engine 2 is stopped after the ignition key 86 is turned off. Generating means 80
Is turned on to accumulate scavenging air in an accumulating means (not shown). When the ignition key 86 is turned off or when the rotation of the engine 2 is stopped after the ignition key 86 is turned off, the scavenging air is supplied from the accumulating means in a predetermined manner. The scavenging air can be quickly supplied to the intake passage 24 by supplying only the scavenging time of the scavenging air or by supplying all of the accumulated scavenging air. Since the generating means 80 is not driven, it is possible to prevent the generation of operation noise and to prevent discomfort to the driver.

Further, a cam angle sensor (not shown) for detecting a cam angle of the engine 2 is connected to the control means 72 and provided.
When the ignition key 86 is turned off or when the rotation of the engine 2 is stopped after the ignition key 86 is turned off, it is determined whether or not the valve timings of the intake / exhaust valves 18 and 20 overlap based on the cam angles detected by the cam sensors. By supplying scavenging air when it is determined that the valve timings of the intake / exhaust valves 18 and 20 overlap, the chance of driving the scavenging air generating means 80 is reduced to reduce the operating noise. Generation can be reduced, and backflow of exhaust gas to the intake port 14 side can be reliably prevented.

Further, by forcibly closing the intake / exhaust valves 18 and 20 when the ignition key 86 is turned off, backflow of exhaust gas to the intake port 14 side can be prevented, and the cam angle can be reduced. Controlling the load applied to the engine 2 (for example, an air conditioner compressor) so that the engine 2 stops rotating at a position where the valve timing of the intake / exhaust valves 18 and 20 does not overlap according to the cam angle detected by the sensor Can also.

[0053]

As described above, the exhaust gas scavenging device according to the present invention is capable of scavenging even if the engine stops at the position where the valve timing of the intake and exhaust valves overlaps and exhaust gas flows back to the intake port side. The backflow of the exhaust gas can be prevented by the air, and the exhaust gas can be prevented from being filled in the intake system including the intake passage.

Therefore, this exhaust gas scavenging device can avoid a decrease in the oxygen concentration of the air present in the intake passage when the engine is stopped, and can surely start the engine at the next start, so that the exhaust gas can be exhausted. Starting failure due to gas can be prevented.

[Brief description of the drawings]

FIG. 1 is a flowchart of control of an exhaust gas scavenging device according to a first embodiment of the present invention.

FIG. 2 is a timing chart of control.

FIG. 3 is a cross-sectional view of an engine including an exhaust gas scavenging device.

FIG. 4 is a schematic configuration diagram of an engine including an exhaust gas scavenging device.

FIG. 5 is a flowchart of control of the exhaust gas scavenging device according to the second embodiment.

FIG. 6 is a timing chart of control.

FIG. 7 is a sectional view of an engine provided with an exhaust gas scavenging device.

FIG. 8 is a cross-sectional view of an engine provided with an air assist injector showing a conventional example.

[Explanation of symbols]

 2 Engine 12 Combustion chamber 14 Intake port 16 Exhaust port 18 Intake valve 20 Exhaust valve 38 Air assist injector 52 Assist air air passage 54 Air assist control valve 70 Exhaust gas scavenging device 72 Control means 80 Scavenging air generating means 82 Scavenging air Supply passage 84 Switching valve 86 Ignition switch

Claims (4)

[Claims] 1. A scavenging air supply passage for providing scavenging air generating means for generating scavenging air for scavenging an intake passage of an engine, and for supplying scavenging air generated by the scavenging air generating means to the intake passage. And a control means for controlling the scavenging air generating means so as to supply scavenging air to the intake passage when an ignition switch of the engine is turned off. 2. A scavenging air supply passage for providing scavenging air generating means for generating scavenging air for scavenging an intake passage of an engine, and supplying scavenging air generated by the scavenging air generating means to the intake passage. And control means for controlling the scavenging air generating means so as to supply scavenging air to the intake passage when the rotation of the engine is stopped after the ignition switch of the engine is turned off. Exhaust gas scavenging device. 3. The engine has an auxiliary air supply passage for supplying auxiliary air to an intake passage, and the scavenging air supply passage is connected to the auxiliary air supply passage. And a switching valve that is switched by the control means so as to supply either the auxiliary air or the scavenging air to the intake passage at a portion connected to the scavenging air supply passage. The exhaust gas scavenging device according to claim 1 or 2, 4. The assist air supply passage according to claim 3, wherein the auxiliary air supply passage is directed to a combustion chamber of an engine and supplies assist air to an air assist injector provided in an intake passage. An exhaust gas scavenging device as described.