Patent Application
20060037310
This application is based upon and claims benefit of priority of Japanese Patent Application No. 2004-240955 filed on Aug. 20, 2004, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an airflow control valve for opening or closing an air passage communicating with an exhaust gas passage in an internal combustion engine, and more particularly to an airflow control valve for controlling an amount of secondary air supplied from an air pump to an exhaust pipe.
2. Description of Related Art
Examples of an airflow control valve for supplying secondary air to a three-way catalyzer in an exhaust pipe for raising temperature of the three-way catalyzer when an engine is being started are disclosed in JP-A-2002-272080 and JP-A-2002-260919. The airflow control valve disclosed therein includes an electromagnetic valve and a one-way valve. An essential portion of the airflow control valve is shown in
As shown in
Air pressurized by an air pump (not shown) is introduced into the valve housing 104, and the introduced air is supplied to a three-way catalyzer (not shown) in an exhaust pipe through an air passage shown with white arrows when the valve 106 opens the opening 105. The one-way valve 103 is opened by the air passing through the air passage and is closed by exhaust gas (shown with dotted arrows in
In the conventional airflow control valve, however, following problems are involved. When the valve 106 is closed, exhaust gas is blown back due to pulsating pressure of the engine and enters into the outlet casing 110 as shown with dotted arrows in
An exhaust gas control valve is conventionally used in an exhaust gas re-circulation system. In this system, part of the exhaust gas is introduced into an air-intake pipe of an engine to reduce an amount of nitrogen-oxides formulated in combustion by lowering a combustion temperature. The re-circulating exhaust gas is supplied to the intake pipe through the exhaust gas control valve. The exhaust gas control valve is composed of a housing forming an exhaust gas passage therein, a valve for closing or opening the exhaust gas passage, and a coil spring biasing the valve in the closing direction. The valve is driven by a motor actuator in the opening direction.
Small particles contained in the exhaust gas adhere to the valve and the valve seat in the exhaust gas control valve, forming deposits around the valve. To reduce an amount of deposits accumulated around the valve, an exhaust gas recirculation valve having a side hole in the passage for accumulating the deposits therein is proposed in JP-A-2002-339811. However, the small particles in the exhaust gas once entered into the side hole are highly possible to bounce out into the passage. Therefore, much effect cannot be expected for the proposed side hole.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved airflow control valve, in which an amount of deposits accumulating on a control valve and a one-way valve is reduced.
The airflow control valve has an air passage and an electromagnetically driven valve disposed in the air passage. The air passage is divided into two passages by the valve, i.e., an upstream passage having an inlet port and a downstream passage having an outlet port. Secondary air compressed by an air pump is introduced into the upstream passage through the inlet port and supplied from the downstream passage to an exhaust pipe of an internal combustion engine through the outlet port. An amount of air supplied to the exhaust pipe is controlled by opening or closing the valve. The outlet port is open to the exhaust pipe, and exhaust gas is blown back into the downstream passage.
A barrier facing the outlet port from which the exhaust gas enters into the airflow control valve is disposed in the downstream passage to reduce an amount of the exhaust gas directly hitting the valve. Thus, an amount of deposits accumulating on and around the valve due to foreign particles contained in the exhaust gas is reduced. The barrier may be made in a form of a dead end space having a small opening facing the outlet port. The exhaust gas entering into the airflow control valve stagnates in the dead end space, and some foreign particles are kept therein. To prevent the foreign particles once kept in the dead end space from bouncing out of the dead end space toward the valve, bent portions may be made at the opening of the dead end space. An interfering wall directly facing the outlet port may be made in the downstream passage to form a stagnating space between the interfering wall and the outlet port.
Preferably, one-way valve for preventing the exhaust gas from entering into the upstream passage while permitting the secondary air to flow therethrough is disposed immediately downstream of the valve. The valve is prevented from being directly hit by the exhaust gas blown back from the exhaust pipe. The one-way valve is also protected from being directly hit by a large amount of the exhaust gas by the barrier, the dead end space or the interfering wall disposed in the downstream passage.
The airflow control valve may be used as a valve for controlling an amount of exhaust gas to be re-circulated from an exhaust pipe into an intake pipe of an engine. In this case, the exhaust gas is introduced from the outlet port, and the inlet port is connected to the intake pipe of the engine.
According to the present invention, an amount of exhaust gas directly hitting the valve and the one-way valve is reduced and an amount of deposits accumulating on and around the valve and the one-way valve is reduced. Accordingly, the airflow control valve can be operated without being hindered by accumulation of deposits. Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.
A first embodiment of the present invention will be described with reference to
As shown in
The electromagnetic valve 1 includes the poppet-type valve 2, a solenoid actuator 4 for driving the valve 2 in the opening direction and a coil spring 5 for biasing the valve 2 in the closing direction. The valve 2 is formed in a disc shape having a resilient rubber ring disposed around its outer periphery. The valve 2 is connected to a valve shaft 21 that is reciprocated in the vertical direction. The valve 2 is seated on a valve seat 23 formed on a valve sheet frame 22 of the valve housing 3 to close an opening 13. When the valve 2 is driven, the valve 2 is lifted from the valve seat 23 to open the opening 13. The valve shaft 21 is slidably inserted into a sleeve 25, and a seal rubber 24 is disposed to close a small sliding gap between the sleeve 25 and the valve shaft 21 to thereby prevent small particles from entering into the sliding gap.
The valve housing 3 is made of aluminum by die-casting, and includes a inner space for accommodating the solenoid actuator 4 and a connecting pipe 26 having an inlet port 10 for introducing the secondary air supplied from the air pump. The outlet casing 9 is also made of aluminum by die-casting, and includes air passages 16, 17, an outlet port 18 to be connected to the exhaust pipe and a dead end space 19 (described later in detail). An upper end of the outlet casing 9 is connected to a flange 39 formed at a lower end of the valve housing 3, and a one-way valve 6 is positioned at the upper end portion of the outlet casing 9. A circular seal rubber 37 is disposed between the valve housing 3 and the outlet casing 9 for hermetically seal the connecting portion. The air passage formed in the valve housing 3 and the outlet casing 9 is separated by the valve 2 into an upstream passage 11, 12 and a downstream passage 14, 16, 17.
The solenoid actuator 4 for driving the valve 2 is composed of a solenoid coil 28 wound around a coil bobbin 27, a pair of terminals 29 for supplying electric power to the solenoid coil 28, a housing cover 30 supporting the terminals 29, a cylindrical yoke 31, a cylindrical stator core 32 connected to the yoke 31 forming a space for accommodating the solenoid coil 28 therebetween, and a moving core 33 connected to the valve shaft 21. The coil bobbin 27 is made of a resin material such as polybutylene terephthalate (PBT) and fixedly positioned in a cylindrical space between the yoke 31 and the stator core 32.
Upon supplying electric power to the solenoid coil 28 from the terminals 29, the moving core 33 connected to the valve shaft 21 is driven downward by magnetic field generated in the yoke 31 and the stator core 32 thereby to open the valve 12 against the biasing force of the coil spring 5. The terminals 29 are connected to the ECU through a wire harness, and the operation of the electromagnetic valve 1 is controlled by the ECU.
At the bottom end of the stator core 32, a flange portion forming the air passage 12 is provided, and at a center portion of the stator core 32, a thin wall portion 35 is formed to provide a high magnetic resistance in the magnetic circuit. The moving core 33 moves downward to open the valve 2 when the magnetic field is generated by the solenoid coil 28. The valve shaft 21 is inserted into a center hole of the moving core 33 and a center hole of a washer 36 so that a step formed on the valve shaft 21 abuts the bottom end of the moving core 33, and the upper end of the valve shaft 21 is staked to fixedly connect the valve shaft 21 to the moving core 33. The coil spring 5 is disposed outside of the sleeve 25, and its upper end is connected to the bottom of the moving core 33 and its lower end is connected to a flange portion of the sleeve 25, so that a biasing force of the coil spring 5 is given to the valve 2 in the closing direction.
The one-way valve 6 is a valve for preventing the exhaust gas blown back from the exhaust pipe from entering into the valve housing 3 while allowing the secondary air to flow therethrough. The one-way valve 6 is composed of a metal plate 41 that has plural openings 15, a reed valve 7 for opening or closing the openings 15, and a reed valve stopper 8 for limiting the reed valve 7 at its maximum open position. The metal plate 41 is made of a metallic material such as aluminum and includes plural openings 15 formed in a mesh-like shape. The reed valve 7 is made of a metallic material such as a spring plate. One end of the reed valve 7 is supported on the metal plate 41 with screws 42 or the like, and the other end of the reed valve 7 is shaped in double tongues or triple tongues. On the surface of the mesh-like openings 15 of the metal plate 41, a rubber seal is formed by baking. The reed stopper 8 is made of a metallic material. One end of the reed stopper 8 is connected to the metal plate 41, and the other end thereof is a free end having double or triple tongues.
Now, the structure of the outlet casing 9 having the dead end space 19 will be described in detail. The exhaust gas may be blown back from the exhaust pipe into the air passage 16, 17 through the outlet 18 due to a pressure pulsation generated in the exhaust pipe. The exhaust gas includes small particles consisting of unburned gas, carbon particles or the like. These small particles accumulate on the reed valve 7 forming deposits thereon. When the deposits are formed on the reed valve 7, the reed valve 7 may become impossible to close to prevent the exhaust gas from entering into the valve housing 3. To decrease the amount of exhaust gas hitting the reed valve 7, barrier 51 is formed so that a passage surface 52 of the barrier 51 faces the outlet 18.
A dead end space 19 is formed inside of the barrier 51. One end of the dead end space 19 is an opening 54 facing the outlet 18, and the other end thereof is closed with a hermetic plug 53. A center line of the head end space 19 is substantially directed to a center line of the outlet port 18. The dead end space 19 is positioned in the downstream passage, i.e., downstream of the valve 2 and the one-way valve 6. The dead end space 19 functions as a stagnating space in which the blown back exhaust gas stagnates, thereby reducing an amount of the exhaust gas directly hitting the reed valve 7. The dead end space 19 is positioned at a far most position from the electromagnetic valve 1 to suppress a temperature rise due to the exhaust gas in a space around the electromagnetic valve 1.
The barrier 51 includes a bent portion 55 for preventing foreign particles once entered into the dead end space 19 from bouncing out again into the air passage 16. The bent portion 55 is bent downwardly so that the opening 54 becomes narrower than an inside space of the dead end space 19. A curved surface 57 is formed above the dead end space 19. The curved surface 57 facilitates a smooth flow of the secondary air flowing out through the plural openings 15 of the metal plate 41.
Now, operation of the airflow control valve described above will be explained. A three-way catalyzer for converting CO, HC and NOx contained in the exhaust gas into harmless components is installed in an exhaust pipe of an automobile. To realize a good conversion reaction in the three-way catalyzer, it is required to keep air-fuel mixture supplied to an internal combustion engine at a stoichiometric ratio (15:1) and to raise the exhaust gas temperature above a certain level, e.g., 350° C. When the exhaust gas temperature is low, e.g., when the engine is being started, secondary air is supplied from an air pump to the three-way catalyzer to raise its temperature. By supplying air to the three-way catalyzer, the catalyzer is activated by heat generated by burning hydrocarbons contained in the exhaust gas.
The secondary air is supplied from the air pump to the three-way catalyzer through the airflow control valve. When the secondary air is required, the valve 2 is opened under the control of the ECU, and the secondary air is sent through the upstream passage 11, 12, the opening 13, the passage 14, the opening 15 and the downstream passage 16, 17, as shown with white arrows in
When the valve 2 is closed, the blown back exhaust gas enters into the air passage 16, 17. Particles contained in the exhaust gas form deposits on and around the reed valve 7 of the one-way valve 6. When a certain amount of the deposits is accumulated on and around the reed valve 7, the reed valve 7 becomes unable to close. If the one-way valve 6 does not function as a one-way valve, the exhaust gas entered the air passage 16 further proceeds to the air passage 14 through the opening 15 of the one-way valve 6. If this happens, it is highly possible that deposits are formed on and around the valve 2, making the valve 2 unable to work properly. If the valve 2 does not work properly, a sufficient amount of the secondary air will not be supplied to the three-way catalyzer.
In order to avoid the trouble mentioned above, the dead end space 19 is formed in the outlet casing 9 according to the present invention. As shown in
Thus, formation of the deposits on and around the one-way valve 6 and the valve 2 is suppressed, thereby securing proper operation of the airflow control valve. Further, since the dead end space 19 is formed at the position far from the valve 2, a temperature rise in the electromagnetic valve 1 due to the exhaust gas is suppressed. Since the curved surface 57 is formed above the dead end space 19, the secondary air smoothly flows through the air passage 16, 17 when the valve 2 is opened. The foreign particles accumulated in the dead end space 19 when the valve 2 is closed are sucked back again into the exhaust pipe together with the secondary air when the valve 2 is opened. Accordingly, it is not necessary to provide a dead end space 19 with a large size or to provide additional means for scavenging the dead end space 19.
A second embodiment of the present invention will be described with reference to
The exhaust gas blown back from the exhaust pipe and entering into the outlet casing 9 from the outlet port 18 hits the passage surface 52a. An amount of exhaust gas directly hitting the one-way valve 6 is reduced, and the exhaust gas stagnates in the stagnating space 59. Foreign particles included in the exhaust gas form deposits in the stagnating space 59 or accumulates therein. Thus, an amount of deposits formed on and around the reed valve 7 is reduced. In this manner, the barrier 51a in the second embodiment functions similarly to the barrier 51 in the first embodiment.
A third embodiment of the present invention is shown in
A fourth embodiment of the present invention will be described with reference to
As shown in
The interfering wall 61 could be an obstacle to the secondary airflow supplied from the air pump through the valve 2. To avoid the interfering wall 61 from becoming an obstacle to the secondary airflow, as shown in
The outlet casing 9 in the fourth embodiment may be further modified to a form shown in
The exhaust gas entering into the air passage 17 from the outlet port 18 hits the passage wall 72 and stagnates in the stagnating space 74. Foreign particles in the exhaust gas are accumulated or deposited in the stagnating space 74. An amount of the exhaust gas directly hitting the one-way valve 6 is reduced, and an amount of foreign particles deposited on and around the reed valve 7 is reduced. The secondary air supplied from the air pump through the valve 2 is smoothly led to the outlet port 18 along the inclined passage walls 75.
The present invention is not limited to the embodiments described above, but it may be variously modified. The barrier and/or the stagnating space for the exhaust gas according to the present invention may be applied to various valves such as a swirl control valve, an intake-air control valve in a swirl control valve, a tumble control valve, an intake-air control valve in a tumble control valve, or a throttle valve for controlling amount of intake-air. The present invention may be applied also to an exhaust gas re-circulating valve for supplying a certain amount of exhaust gas into an air-intake pipe of an internal combustion engine.
While the present invention has been shown and described with reference to the foregoing preferred embodiments, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-240955 | Aug 2004 | JP | national |
