Controlling secondary air injection in engine exhaust

Abstract

A solenoid operated valve suitable for controlling flow of air for injection into the exhaust of an engine, the poppet is connected to the solenoid armature in a lost-motion connection. Upon energization, the armature achieves momentum during the lost-motion movement and imports an impulse to the poppet to ensure movement in the event of any tendency of the poppet to stick. A one-way valve prevents exhaust back pressure from opening the poppet.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to the controlling of injection of air into the exhaust stream of an internal combustion engine particularly for the purpose of reducing emissions in motor vehicle engine applications.

[0002] Heretofore, it has been the practice in controlling such air injection to utilize an engine driven air pump with its outlet connected to the inlet of the diaphragm operated valve actuated in response to an engine inlet manifold vacuum signal. Failures of this type of valve to open have been experienced at high elevations with reduced atmospheric pressure and at high engine loads with reduced engine manifold vacuum,. This has resulted in insufficient air being injected into the exhaust stream in increased engine emissions when the engine is operating under heavily loaded conditions.

[0003] It has been suggested to utilize an electrically operated valve in place of a pressure responsive diaphragm operated valve. However, electrically operated valves, particularly of the solenoid operated type have been found to have insufficient force, when operated on the low voltage vehicles power supply, to open the valve in the event the valve obturator or poppet sticks due to buildup on the valve seat of residue from products of combustion.

[0004] It has thus been desired to find a way or means of electrically operating a valve for controlling flow of secondary air for injection into the exhaust of an internal combustion engine which is not subject to sticking when operated by a relatively low powered electric actuator and which is relatively low in manufacturing cost so as to remain competitive in high volume mass production motor vehicle applications.

BRIEF SUMMARY OF THE INVENTION

[0005] The present invention provides an electrically operated valve for controlling flow of pressurized air for injection into the exhaust system of an engine which is able to overcome the pressure forces of the engine exhaust acting on the poppet with a relatively low powered electrical actuator. The electrically operated actuator has an operating member connected to the valve obturator or poppet in a manner which permits lost motion during initial energization of the actuator such that the operating rod acquires sufficient momentum with a relatively low electrical current actuating force to actuate the poppet with an impulse sufficient to overcome the pressure forces of the exhaust back pressure acting on the obturator and any residue tending to hold the poppet closed. A one-way valve is disposed in the outlet of the valve assembly to prevent exhaust backflow to the source of pressurized air.

[0006] The present invention thus provides an electrically operated valve capable of operating on a relatively low voltage low current power supply and which provides for positive opening of the valve obturator in order to prevent sticking on the valve seat and is particularly suitable for controlling flow of pressurized air to an engine exhaust system where the valve obturator and valve seat are exposed to the products combustion which can form residue and buildup on the seat and obturator in prolonged service.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a cross-section of the valve assembly taken through the center line of the valve operating rod; and,

[0008] FIG. 2 is an enlarged view of a portion of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0009] Referring to FIG. 1, the valve assembly of the present invention is indicated generally at 10 and has a valve body 12 provided with an inlet fitting 14 which has inlet passage 16 therein. In a vehicle internal combustion engine application of the present invention, valve 10 is connected via a conduit 18 to the outlet of an air pump 20 typically connected to and driven by a vehicle engine 22. The valve body 12 has an outlet portion 24 which has a one-way valve indicated generally at 26 communicating with an outlet passage 28 and with a flow passage 30 provided in the valve body 12. Outlet portion 24 in the illustrated embodiment is a separate member attached to body 12, but it will be understood that portion 24 may, alternatively, integrally formed with body 12.

[0010] Outlet passage 28 is formed in a fitting 32 which is provided on an outlet cover member 34 disposed over the one-way valve 26 and secured to the body portion 24.

[0011] In the motor vehicle engine application of the invention valve assembly 10 shown in FIG. 1, the outlet fitting 32 is connected to a conduit 36 which is connected to an inlet fitting 38 provided on the exhaust manifold 40 of the engine.

[0012] Valve body 12 has a valving chamber 42 formed which communicates with inlet passage 16 through valve seat 44 and also with the flow passage 30. A valve obturator or poppet 46 is disposed in the chamber 42 and configured to contact and seal on the valve seat 44. An operating member or rod 48 has one end thereof connected to the obturator 46; and, the operating rod extends through the upper portion 50 of the valve body 12 and exteriorly thereof and is slidably supported therein by a suitable bearing 52.

[0013] A flexible seal 54 of the bellows type is disposed over the rod and prevents flow of fluid through the bearing 52, yet permits axial movement of the rod in the bearing. A spring 56 is disposed in the chamber 42 and is operative to urge the obturator 46 in a direction for seating against valve seat 44.

[0014] An electrical operator in the form of a solenoid, indicated generally at 58, is attached to the upper portion of the body 50 and retained thereon by a cap or cover 60 secured to the upper portion of the body 50 by any suitable expedient as for example a threaded connection as denoted by reference numeral 62. The solenoid assembly 58 includes an annular pole piece or flux collector 64 over which is received bobbin 66 upon which is wound a coil 68 typically of“magnet” wire. An armature of magnetically permeable material is disposed slidably within the pole piece 64 and is operative for movement upon electrical energization of the coil 68. The coil 68 is surrounded by a flux collector 70 in the form of a pole frame which completes the flux loop about the coil in conjunction with the pole piece 64; and, another pole piece 72 disposed at the upper end of the pole frame 70 as denoted by reference numeral 72.

[0015] Referring to FIG. 2, a portion of the armature 74 is shown with the upper end of the operating rod 48 received in sliding arrangement in a bore 76 formed in the armature. The upper end of the rod 48 has a radially outwardly extending flange 78 formed thereon, the underside of which is spaced from the bottom 80 of a counter bore formed in the armature so as to provide a limited lost motion movement of the armature with respect to the undersurface of the flange 28 by an amount denoted by the reference character“d” and the dashed line in FIG. 2.

[0016] It will be understood, that upon energization of the coil, the armature 74 moves in an upward direction through the distance“d” as shown by the dashed lines in FIG. 2 and attains a velocity and momentum with respect to the undersurface of the flange 78 and contacts flange 78 with an impulse. This impulse results in providing adequate force to overcome any“sticking” and therefore ensures raising of the obturator 46 from the valve seat 44 to open the valve.

[0017] The position of the obturator or poppet 46 with respect to the valve seat 44 is thereafter determined by the number of ampere turns of the coil in a manner well known in the art. It will be understood that the number of ampere turns of the coil at the available level of excitation current is sufficient to overcome the bias of the spring 56.

[0018] The present invention thus enables the valve of the present invention to open with a minimum number of ampere turns of coil excitation and yet is capable of overcoming any“sticking” of the poppet or obturator to the valve seat which may be caused by combustion residue deposited on the valve seat or the poppet.

[0019] Referring again to FIG. 1, the one-way valve 26 is shown in solid outline in the open position; however, it will be understood that in the coil deenergized state of the valve, the valve member 76 will be moved to the position shown in dashed outline under the force of the back pressure of the exhaust from the engine, thereby closing the outlet of the valve from communication with the valve outlet passage 28.

[0020] Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.

Claims

1. An electrically operated valve assembly for controlling air injection into the exhaust stream of an internal combustion engine comprising:

(a) valve body structure including an inlet port adapted for connection to a source of pressurized air, a valving chamber having a valve seat communicating with the inlet and an outlet port adapted for connection to the exhaust stream;

(b) a one-way valve disposed to permit flow from the valving chamber to the outlet port and prevent flow from the outlet port to the valving chamber;

(c) a valve obturator disposed for movement between a closed position preventing and an open position permitting flow over said valve seat to the outlet port;

(d) an actuator operatively connected to effect the movement of the obturator, the actuator having a portion thereof extending externally of said valving chamber;

(e) a solenoid having an armature moveable upon electrical energization thereof, with the armature operative to effect the movement of the obturator, wherein the armature is disposed for a predetermined limited lost motion movement with respect to the actuator.

2. The valve assembly defined in claim 1, wherein the armature strikes the actuator with an impulse at the end of the limited lost-motion movement.

3. The valve assembly defined in claim 1, wherein the actuator comprises a rod-like member extending through the armature and the obturator.

4. The valve assembly defined in claim 1, wherein the actuator member comprises a rod-like member extending through the armature with one end of the rod-like member enlarged, wherein the amount of the lost-motion movement is determined by the distance between the enlarged end of the rod-like member and the armature when the solenoid is deenergized.

5. The valve assembly defined in claim 4, wherein the actuator has one end extending through the armature and an opposite end extending through the obturator.

6. A method of controlling air injection into the exhaust stream of an engine comprising:

(a) providing a valve body and disposing a valve obturator on a valve seat formed in the body;

(b) connecting an inlet side of the valve seat to an air pump and connecting an outlet side of the valve seat to the exhaust stream;

(c) disposing a one-way valve between the outlet side of the valve seat and the engine exhaust stream and preventing exhaust flow therethrough;

(d) connecting the armature of a solenoid operator to the valve obturator and effecting movement of the obturator upon electrical energization of the solenoid and providing a predetermined limited lost-motion between the solenoid armature and the obturator.

7. The method defined in claim 6, wherein the step of connecting the armature to the obturator includes passing a rod-like member through the armature and connecting an end thereof to the obturator.

8. The method defined in claim 6, wherein the step of connecting the armature to the obturator includes enlarging one end of a rod-like member and passing the remainder through the armature and connecting the end opposite the enlarged end to the obturator.

9. The method defined in claim 6, wherein the step of providing limited lost motion includes disposing the enlarged end of the rod-like member for limited lost motion with respect to the armature.