Integrity confirmation of evaporative emission control system against leakage
First Claim
1. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke wherein said means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke comprises mechanical spring means to which energy is imparted during an intake stroke and which releases energy during a compression stroke.
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Accused Products
Abstract
An on-board diagnostic system for an evaporative emission control system of an internal combustion engine powered vehicle employs a positive displacement reciprocating pump to create in evaporative emission space a pressure that differs significantly from ambient atmospheric pressure. The pump is powered by using engine intake manifold vacuum to force an intake stroke during which both an internal spring is increasingly compressed and a charge of ambient atmospheric air is created in an air pumping chamber space. Vacuum is then removed, and the spring relaxes to force a compression stroke wherein a portion of the air charge is forced into the evaporative emission space. The rate at which the pump reciprocates to alternately execute intake and compression strokes indicates the pressure and flow through a leak in the evaporative emission space. Detection of this rate serves as a measurement of leakage for the purpose of distinguishing integrity of the evaporative emission space from non-integrity.
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Citations
33 Claims
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1. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke wherein said means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke comprises mechanical spring means to which energy is imparted during an intake stroke and which releases energy during a compression stroke.
- 2. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke, and characterized further in that said positive displacement reciprocating pump comprises a housing that is divided by a movable wall into an air pumping chamber space and a vacuum chamber space, inlet means including a one-way valve communicating an inlet of said air pumping chamber space to atmosphere such that air can enter, but not exit, said air pumping chamber space via said inlet means, outlet means including a second one-way valve communicating an outlet of said air pumping chamber space to said evaporative emission space such that air can exit, but not enter, said air pumping chamber space via said outlet means, said pump further comprising a mechanical spring that acts on said movable wall in a sense urging said movable wall to compress air in said air pumping chamber space, and means for repeatedly causing said vacuum chamber space to be alternately communicated to intake manifold vacuum and to atmosphere such that during communication of said vacuum chamber space to intake manifold vacuum, said movable wall executes an intake stroke against force exerted thereon by said mechanical spring to draw air from atmosphere into said air pumping chamber space through said inlet means, and during communication of said vacuum chamber space to atmosphere, said mechanical spring forces said movable wall to execute a compression stroke to force some of the air from said air pumping chamber space through said outlet means into said evaporative emission space.
- 7. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke, and characterized further in that a sensor means is disposed to sense the execution of predetermined travel of said mechanism along a compression stroke, and in that means responsive to said sensor means causes said mechanism to execute an intake stroke upon said sensor means sensing such execution of predetermined travel of said mechanism along said compression stroke.
- 12. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in Cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured Charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the Compression stroke, and characterized further in that said mechanism comprises a movable member that executes intake and compression strokes and in that said pump comprises a limit stop disposed for coaction with said movable member to define a final limit for an intake stroke, by means for causing said movable member to occupy the final limit of an intake stroke for an amount of time that is slightly more than sufficient to assure that a measured charge volume of air at atmosphere pressure will be created before the execution of an ensuing compression stroke, and in that a sensor means is disposed to sense execution of predetermined travel of said movable member along a compression stroke, and in that means responsive to said sensor means causes said movable member to execute an intake stroke upon said sensor means sensing execution of predetermined travel of said movable member along a compression stroke from a final limit of an intake stroke.
- 14. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of Said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke, and characterized further in that said positive displacement reciprocating pump comprises a housing that is divided by a movable wall into an air pumping chamber space and a vacuum chamber space, inlet means including a one-way valve communicating an inlet of said air pumping chamber space to atmosphere such that air can enter, but not exit, said air pumping chamber space via said inlet means, outlet means including a second one-way valve communicating an outlet of said air pumping chamber space to said evaporative emission space such that air can exit, but not enter, said air pumping chamber space via said outlet means, and said valve means comprises a vent valve having a vent valve inlet in fluid communication with said outlet means at a location between said evaporative emission space and the one-way valve of said outlet means and a vent valve outlet in fluid communication with said inlet means at a location between atmosphere and the one-way valve of said inlet means.
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16. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion Chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume Of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke, and characterized further in that said valve means comprises a vent valve that is integrally associated with said pump by being disposed to selectively open and close a passage extending between an inlet port of said pump and an outlet port of said pump.
- 17. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for Storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a Collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected Until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication Of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission Space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke, and characterized further in that said positive displacement reciprocating pump comprises a housing that is divided by a movable wall into an air pumping chamber space and a vacuum chamber space, a one-way valve through which said inlet port communicates with said air pumping chamber space such that air can enter, but not exit, said air pumping chamber space via said inlet port, a second one-way valve through which said outlet port communicates with said air pumping chamber space such that air can exit, but not enter, said air pumping chamber space via said outlet port, said pump further comprising a mechanical spring that acts on said movable wall in a sense urging said movable wall to compress air in said air pumping chamber space, means for repeatedly causing said vacuum chamber space to be alternately communicated to intake manifold vacuum and to atmosphere such that during communication of said vacuum chamber space to intake manifold vacuum, said movable wall executes an intake stroke against force exerted thereon by said mechanical spring to draw air from atmosphere into said air pumping chamber space through said inlet port and first one-way valve, and during communication of said vacuum chamber space to atmosphere, said mechanical spring forces said movable wall to execute a compression stroke to force some of the air from said air pumping chamber space through said second one-way valve and said outlet port into said evaporative emission space, and said vacuum chamber space is in communication with a vacuum actuator for operating said vent valve such that when vacuum is delivered to said vacuum chamber space, it is also conveyed to said vacuum actuator to cause said vent valve to close.
- 19. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with headspace of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said Vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission space against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, by creating in said evaporative emission space a pressure that is significantly different from ambient atmospheric pressure, characterized in that said pump means is powered by vacuum that is derived from engine intake manifold vacuum and that is selectively communicated to said pump means by an selectively operable, electrically operated valve.
- 22. A method for distinguishing between integrity and non-integrity of an evaporative emission control system of an internal combustion engine powered automotive vehicle having a fuel tank for storing volatile liquid fuel for the engine, said evaporative emission control system comprising a collection canister that in cooperative combination with headspace of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, and valve means via which said evaporative emission space is selectively communicated to atmosphere, said method characterized by closing both said valve means and said canister purge valve, and while they are closed, creating in said evaporative emission space by means of a reciprocating pump a pressure that is significantly different from atmospheric pressure, measuring the duration between reciprocations of said pump, and utilizing such measured duration to distinguish between integrity and non-integrity of said evaporative emission control system.
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24. A method for distinguishing between integrity and non-integrity of an evaporative emission control system of an internal combustion engine powered automotive vehicle having a fuel tank for storing volatile liquid fuel for the engine, said evaporative emission control system comprising a collection canister that in cooperative combination with headspace of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, and valve means via which said evaporative emission space is selectively communicated to atmosphere, said method characterized by closing both said valve means and said canister purge valve, and while they are closed, creating in said evaporative emission space pressure that is significantly different from atmospheric pressure under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, wherein the step of creating pressure in said evaporative emission space that is significantly different from atmospheric pressure comprises operating a pump that comprises a vacuum chamber space, an air pumping chamber space, a movable wall separating said vacuum chamber space from said air pumping chamber space, and mechanical spring means that acts on said movable wall, by communicating vacuum derived from engine intake manifold vacuum to said vacuum chamber space to draw vacuum in said vacuum chamber space that causes said movable wall to execute an intake stroke that causes a measured charge of atmospheric air to be drawn in said air pumping chamber space and energy to be imparted to said mechanical spring means, and then venting the vacuum in said vacuum chamber space to allow said mechanical spring means to release energy and cause said movable wall to execute a compression stroke that compresses said measured charge of atmospheric air in said air pumping chamber space and forces a portion thereof into said evaporative emission space.
- 25. A pump for use in distinguishing between integrity and nonintegrity of an evaporative emission control system of an internal combustion engine powered automotive vehicle, said pump comprising a housing having inlet means for communication with atmosphere and outlet means for communication with evaporative emission space of said evaporative emission control system, a movable wall that separates an air pumping chamber space of said housing from a vacuum chamber space of said housing, said inlet means including a one-way valve communicating an inlet of said air pumping chamber space to atmosphere such that air can enter, but not exit, said air pumping chamber space via said inlet means, outlet means including a second one-way valve communicating an outlet of said air pumping chamber space to such evaporative emission space such that air can exit, but not enter, said air pumping chamber space via said outlet means, said pump further comprising a mechanical spring that acts on said movable wall in a sense urging said movable wall to compress air in said air pumping chamber space, and means for alternately communicating said vacuum chamber space to engine intake manifold vacuum and to atmosphere such that when said vacuum chamber space is communicated to intake manifold vacuum, said movable wall executes an intake stroke against force exerted thereon by said mechanical spring to draw air from atmosphere into said air pumping chamber space through said inlet means, and when said vacuum chamber space is communicated to atmosphere, said mechanical spring forces said movable wall to execute a compression stroke to force some of the air from said air pumping chamber space through said outlet means into said evaporative emission space, and sensor means disposed to sense when said movable wall is substantially at one limit of its reciprocation.
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28. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion to create pressure in said evaporative emission space that, in the absence of a gross leak, is substantially different from ambient atmospheric pressure, and sensor means associated with said mechanism to provide both a signal that is used both in controlling the reciprocation of said mechanism and for distinguishing between integrity and non-integrity of said evaporative emission control system.
- 29. A method for distinguishing between integrity and non-integrity of an evaporative emission control system of an internal combustion engine powered automotive vehicle having a fuel tank for storing volatile liquid fuel for the engine, said evaporative emission control system comprising a collection canister that in cooperative combination with headspace of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged to the engine through a canister purge valve, and valve means via which said evaporative emission space is selectively communicated to atmosphere, said method characterized by closing both said valve means and said canister purge valve, and while they are closed, creating in said evaporative emission space pressure that is significantly different from atmospheric pressure under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, wherein the step of creating pressure in said evaporative emission space that is significantly different from atmospheric pressure comprises operating a pump that comprises a mechanical spring means and a movable wall that is operable to expand and contract the volume of an air pumping chamber space, said operating step comprising causing said movable wall to execute an intake stroke that expands said air pumping chamber space and causes a measured charge of atmospheric air to be drawn in said air pumping chamber space and energy to be stored in said mechanical spring means, and after the intake stroke, allowing said mechanical spring means to contract said air pumping chamber space by releasing energy stored in said mechanical spring means to move said movable wall along a compression stroke that compresses said measured charge volume of air to pressure greater than atmospheric pressure and forces a portion thereof into said evaporative emission space.
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31. For use in an automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a canister purge valve, a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged to said engine by said canister purge valve, and vent valve means via which said evaporative emission space is selectively communicated to atmosphere;
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a pump for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said vent valve means, and said canister purge valve, said pump being a positive displacement reciprocating pump comprising; a mechanism that, while said vent valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said engine, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during an intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on a compression stroke, wherein said means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on a compression stroke comprises mechanical spring means to which energy is imparted during an intake stroke and which releases energy during a compression stroke. - View Dependent Claims (32)
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Specification