MXPA97005057A - Leak detection pump with integrate seal - Google Patents

Abstract

An on-board diagnostic system for an evaporative emission control system of a vehicle driven by an internal combustion engine employs a reciprocating positive displacement pump to create a pressure in the evaporation emission space that differs significantly from the atmospheric pressure of the environment. The pump is driven using engine intake manifold vacuum to force an intake time during which an internal spring is subjected to increasing pressure and a charge of atmospheric air from the environment is created in an air pumping chamber space . The vacuum is then removed, and the spring is relaxed to force a compression time where a portion of the air charge is forced into the evaporation emission space. The speed at which the pump reciprocates to alternately run the intake and compression times indicates the pressure and flow through a leak in the evaporation emission space. The detection of this velocity serves as a leakage measurement for the purpose of distinguishing the integrity from the non-integrity of the evaporation emission space. The described pump has a novel arrangement of its internal valve system that reduces the number of parts required compared to a previous pump

Description

LEAK DETECTION PUMP WITH COMPREHENSIVE BREATH SEAL FIELD OF THE INVENTION This invention relates to evaporation emission control systems for the fuel systems of motor vehicles driven by an internal combustion engine, particularly to devices for confirming the integrity of an evaporation emission control system against leaks.

BACKGROUND A typical evaporative emission control system in a modern automotive vehicle comprises a vapor collection box that collects the volatile fuel vapors generated in the headspace of the fuel tank by volatilizing the li fuel in the tank. During the conditions leading to the purge, the evaporation emission space which is cooperatively defined by the head space of the tank and the head is bled to the intake manifold of the engine by means of a box purge system comprising a valve of box purge solenoid connected between the box and the intake manifold of the engine and operated by an engine management computer. The purge solenoid valve of the box is opened by a signal from the engine management computer in an amount that allows the vacuum of the intake manifold to extract the volatile vapors from the box for the drag with the fuel mixture passing into the space of the combustion chamber of the engine at a speed compatible with the operation of the engine to provide both stable vehicle maneuverability and an acceptable level of discharge emissions. United States government regulations ree that certain automotive vehicles of the future driven by internal combustion engines that run on volatile fuels such as gasoline have their evaporation emission control systems eped with the on-board diagnostic capability to determine if it is present a leak in the evaporation emission space. It has so far been proposed to make such a determination by temporarily creating a pressure condition in the evaporation emission space that is substantially different from the ambient atmospheric pressure, and then monitoring a change in that substantially different pressure that is indicative of a leak. Commonly owned US Patent No. 5,146,902"Positive Pressure Canister Purge System Integrity Confirmation" describes a system and method for making such determination by pressurizing the evaporation emission space by creating some positive pressure therein ( with respect to atmospheric pressure of the environment) and then monitoring a decrease in that pressure indicative of a leak. Confirmation of the leakage integrity by subjecting the evaporation emission space to positive pressure offers certain benefits over the confirmation of leak integrity by subjecting it to negative pressure, as mentioned in the patent referenced. Commonly owned patent WO-A-94/15090 describes an arrangement and a technique for measuring the effective orifice size of relatively small leaks of the evaporation emission space once the pressure has been brought substantially to a predetermined amount which is substantially different from the atmospheric pressure of the environment. In general terms, this involves the use of a reciprocal movement pump to create such a pressure magnitude in the evaporation emission space and a switch that responds to the reciprocal movement of the pump mechanism. More specifically, the pump comprises a movable wall which moves reciprocally during a cycle comprising an intake time and a compression time to create such a pressure quantity in the evaporation intake space. At an intake time, an atmospheric air charge is drawn into an air pump chamber space of the pump. In a consistent compression time, the movable wall is pushed by a mechanical spring to pressurize an air load in such a way that a portion of the compressed air charge is forced into the evaporation emission space. In a subsequent intake time, another atmospheric air charge is created. At the beginning of the integrity confirmation procedure, the pump rapidly moves reciprocally, seeking to develop pressure to a predetermined level. If a large leak is present, the pump will be unable to pressurize the evaporation emission space at the predetermined level, and therefore will keep moving rapidly reciprocally. Therefore, to continue the rapid reciprocal movement of the pump beyond a time by which it should be substantially reached, the predetermined pressure will indicate the presence of a large leak, and therefore it can be considered that the emission control system of Evaporation lacks integrity. The pressure that the pump strives to achieve is essentially fixed by its mechanical spring mentioned above. In the absence of a large leak, the pressure will develop to the predetermined level, and the speed of reciprocal movement will decrease correspondingly. For a theoretical zero leakage condition, the reciprocal movement will cease at a point where the spring is unable to force more air into the evaporation emission space. Leakage smaller than a large leak is detected in a way that is capable of measuring the size of the effective leak hole, and consequently the exposure is able to distinguish between very small leaks that can be considered acceptable and somehow larger leaks that, although considered smaller than a large leak, can nevertheless be considered unacceptable. The ability to provide some measure of the effective hole size of the leak that is less than a large leak, rather than just distinguishing between integrity and non-integrity, can be considered important for certain automotive vehicles, and in this regard the exposure it is especially advantageous since the means by which the measurement is obtained are achieved by an integral component of the pump, rather than by a separate pressure sensor. The means for obtaining the measurement comprise a switch which, as an integral component of the pump, is placed to detect the reciprocal movement of the pump mechanism. Such a switch can be for example a reed switch, an optical switch, or a Hall detector. The switch is used both to cause the pump mechanism to move reciprocally at the end of a compression time and to be an indicator of how fast air is being pumped into the evaporation emission space. Because the speed of reciprocal movement of the pump will begin to decrease as the pressure begins to develop, the detection of the speed of the operation of the switch can be used first to determine whether a large leak is present or not. As explained in the above, a large leak is indicated by the failure of the speed of the operation of the switch that decreases below a certain frequency within a certain amount of time. In the absence of a large leak, the frequency of the switch operation provides a measure of the leak that can be used to distinguish between integrity and non-integrity of the evaporation emission space even if the leakage is determined to be less than big leak Once the pressure of the evaporation emission space at the determined pressure has been substantially developed, the indication of the switch of a reciprocal movement speed of the pump less than a certain frequency will indicate the integrity of the evaporation emission space while the indication of a higher frequency will indicate non-integrity.

The pump is also used to perform flow confirmation confirming the absence of blockage in the purge flow lines.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to further improvements in the organization and arrangement of the pump. The invention retains advantages of the previous pump: by allowing integrity confirmation to be performed while the engine is running; by allowing integrity confirmation to be made over a wide range of filling of the fuel tank between full and empty so that the procedure for the most part is independent of the size of the tank and the level of filling; by providing a method that is largely independent of the particular type of volatile fuel that is being used; and by providing reliable, cost-effective means in accordance with on-board diagnostic requirements to ensure leak integrity of an evaporative emission control system. Additionally, the invention provides the pump with a novel internal valve system for selectively communicating the space of the air pumping chamber, a first orifice leading to the evaporation emission space, and a second orifice leading to the atmosphere. This novel arrangement employs fewer parts, and consequently offers the opportunity for improved manufacturing economy and reliability during use. The invention, in its most general aspect, refers to the displacement of the reciprocating pump for use in performing a test on a portion of a fuel system of a motor vehicle driven by an internal combustion engine that consumes fuel for the purpose of to distinguish between the integrity and non-integrity of such portion of the fuel system, under conditions that lead to obtain a reliable distinction between such integrity and non-integrity, against the leakage of such portion of the fuel system, such portion of the fuel system comprising a fuel tank, an evaporative emission space defined cooperatively by a head space of the fuel tank and a steam collection box for temporarily collecting the fuel vapors generated by the volatilization of fuel from the fuel tank, a box purge valve to periodically purge comb vapors ustible collected from the box to an intake manifold of the engine for entrainment with flow of fuel-air mixture of fuel into the space of the combustion chamber of the engine and the subsequent combustion in the space of the combustion chamber to propel the vehicle , and valve means comprising a vent valve - through which the evaporation emission space communicates selectively to the atmosphere; the reciprocating positive displacement pump having a wall housing comprising an air pumping chamber space having movable wall, a non-movable wall separating such an air pumping chamber space from a wall housing containing such breather valve, the housing further comprising a first hole adapted to communicate the interior of the housing to the evaporation emission space and a second hole adapted to communicate the interior of the housing to the atmosphere, the pump also comprising a mechanical spring that acts on the movable wall in a direction that urges the movable wall to contract the volume of the space of the air pumping chamber, the pump further comprising a first one-way valve means arranged to allow air to pass through the second hole from the atmosphere and that enters, but does not leave, the space of air pumping chamber, a second One-way valve means arranged to allow air to escape, but not enter, the air pumping chamber space and pass through said first orifice to the evaporation emission space, the effective means while the valve means are closed, to avoid communication of the evaporation emission space to the atmosphere, and while the purge valve of the box is closed, avoid communication of the evaporation emission space to the manifold of intake, to repeatedly cause the movable wall to execute an intake time that expands the volume of the space of the air pump chamber against the force exerted thereon by the mechanical spring, by testing the opening of the first valve means of a only felt in the process, so that the air fills the space of the air pumping chamber to create a measured volume of air charge at a given pressure, and that imparts energy to such a spring for the subsequent execution of a time of compression that shrinks the volume of the space of the air pumping chamber extracting energy from the spring to compress the volume of measured air load at a pressure greater than that given pressure, causing the opening of the second one-way valve means in the process, such that a portion of air in the space of the air-pumping chamber is forced into the emission space of evaporation during a compression time, the first and second holes having respective points of communication with the interior of the housing, one of the first and second one-way valve means being arranged, both when the vent valve is open and when the The vent valve is closed, in operative association with a first set of one or more holes in the non-movable wall through which one of the first and second one-way valve means controls the passage of air between the space of the air pumping chamber and one of the first and second orifices, and the other of the first and second one-way valve means being arranged, when the The vent valve is closed, in operative association with a second set of one or more holes in the non-movable wall through which the other of the first and second one-way valve means controls the air passage between the space of the air pumping chamber and the other of the first and second orifices, characterized in that: the other of the first and second one-way valve means is arranged in such a way that when the vent valve is open, the other first and second valve One-way valve means is disposed outside of the operative association with the second set of one or more holes such that the air is able to pass both inwardly and outwardly from the space of the air-pumping chamber through of the second games of one or more holes. The foregoing, together with the additional aspects, advantages and benefits of the invention, will now be seen in the description and the subsequent claims which should be considered in conjunction with the accompanying drawings. The drawings describe a currently preferred embodiment of the invention in accordance with the best mode considered at this time to carry out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a general schematic diagram of an evaporation emission control system that modalizes the principles of the present invention, including the relevant portions of an automobile. Figure 2 is a longitudinal cross-sectional view through one of the components of Figure 1, by itself. Figure 3 is a fragmentary view of a portion of Figure 2 showing a different operative position from Figure 2. Figure 4 is a graph diagram useful to appreciate certain principles of the present invention.

DESCRIPTION OF THE PREFERRED MODALITY The Figure shows an evaporation emission control system (EEC) for a motor vehicle driven by an internal combustion engine comprising, in association with the vehicle engine 12, the fuel tank 14 and the engine management computer 16 , a conventional steam collection box 18 (carbon box), a box purge solenoid valve 20 (CPS), and a leak detection pump 24 (LDP). The head space of the fuel tank 14 is placed in fluid communication with an inlet opening of the box 18 by means of a conduit 26 in such a way as to cooperatively define an evaporation emission space within which the fuel vapors generated by the volatilization of the fuel in the tank is temporarily confined and collected until it is bled to an intake manifold 28 of the engine 12. A second conduit 30 connects via the fluid an outlet orifice of the box 18 with an inlet opening of the valve 20 of the tank. CPS, while a third conduit 32 fluidly connects an outlet orifice of the CPS valve 20 with the intake manifold 28. A fourth conduit 34 fluidly connects a vent hole in the case 18 with a first orifice 46 in the LDP 24. The LDP 24 also has a second orifice 44 that communicates directly with the atmosphere. The engine management computer 16 receives an input number (engine parameters) relevant to the control of the engine and its associated systems, including the 10 EEC system. An electrical output port of the computer controls the 20 CPS valve via an electrical connection 36, and another leak detection pump 24 via an electrical connection 40. The LDP 24 has a vacuum inlet orifice 48 which communicates via a conduit 50 with an intake manifold 28, and an electrical outlet in which it provides a signal to the computer 16 via an electrical connection 54. Although the engine is running , operation of LDP 24 is occasionally directed by computer 16 as part of an occasional diagnostic procedure to confirm the integrity of the 10 EEC system against leakage. During the success of the diagnostic procedure, the computer 16 orders that the CPS valve 20 be closed. Occasionally when the engine is running others when the diagnostic procedure is performed, the LDP 24 does not work and the computer 16 selectively operates the 20 CPS valve such that the 20 CPS valve is opened under conductive conditions to purge and close under non-conductive conditions for the purge. Therefore, during these times of operation of the motor vehicle, the function of the purge of the box is carried out in the usual way for the particular vehicle and the engine whenever the diagnostic procedure is not being carried out. When the diagnostic procedure is being carried out, the evaporation emission space is closed in such a way that it can be pressurized by the LDP 24. Attention is now directed to the details of the LDP 24 with reference to Figure 2. The LDP 24 comprises a housing 56 composed of various assembled parts, these parts preferably being of suitable fuel resistant plastic. In the interior of the housing, a movable wall 58 divides the housing 56 into a space 60 of the vacuum chamber and a space 62 of the air pump chamber. The movable wall 58 comprises a general circular diaphragm 64 that is flexible, but essentially non-stretchable, and having an outer peripheral margin captured in a sealed form between two of the housing parts. The generally circular base 66 of an insert 68 is held in assembly against a central region of a diaphragm face 64 and is towards the chamber space 60. A cylindrical arrow 70 projects centrally from the base 66 in a cylindrical sleeve 72 formed in one of the housing portions. A mechanical spring 74 in the form of a coil of helical metal is disposed in the space 60 of the chamber in an outwardly circumferential relationship by jumping to the arrow 70, and its axial ends are seated in the respective seats formed in the base 66 and that portion of the hopper sleeve 72 of the housing. The spring 74 acts to push the movable wall 58 axially into the chamber space 62 while the coercion of the arrow 70 with the sleeve 72 serves to restrict the movement of the central region of the movable wall to a straight line movement. along the imaginary axis 75. The position illustrated by Figure 2 shows the spring 74 forcing a central portion of a face of the diaphragm 58 that is towards the chamber space 62 against a detent 76 and this represents the position that the mechanism assumes when the LDP is not being operated . The ports 44 and 46 communicate selectively with each other and with the chamber space 62 by the valve arrangements comprising two one-way umbrella valves 84, 86, and a plunger valve 88. The housing 56 comprises a housing 90 of walls directly below, and spaced apart from the chamber space 62 by a wall 92 which is perpendicular to the axis 75. The housing 90 can be considered to comprise a generally circular side wall 94 extending down from the wall 92 and an end wall 96 in some way dome-shaped forming the lower part of the housing. The hole 44 intercepts the side of the dome of the wall 96 in such a way that it opens into the interior of the housing 90. The hole 46 passes through the side wall 94 and continues until it intercepts a circular wall 98 that extends downwardly. from the wall 92 coaxial with the shaft 75, but which resides radially inward of the side wall 94 and also stops shortly before the end wall 96. The orifice 46 opens to the space surrounded by the wall 98 and has no communication with the interior of the housing 90 along that portion of its length that is between the walls 94 and 98. A portion of the wall 92 that is radially disposed outwardly of the wall 98 relative to the shaft 75 provides a mounting for the valve 84 that allows air to pass from the hole 44, through the interior of the housing 90 between the walls 94 and 98 and to the chamber space 62 through the one or more through holes 87 in the wall 92, but not the opposite direction. Figure 2 shows the normally closed condition of the sunshade-type valve 84, the center of which is retained in a retained manner on the wall 92, and the outer peripheral margin of which is sealed against the wall 92 in a separate relation outwardly with respect to one or more than 87 holes in the wall, closing the flow to these holes.

The plunger valve 88 is the vent valve of the evaporation emon system, and serves two purposes: one, comprises a head 100 for selectively detaching from and seating on the lower end in some open manner of the wall 98 that constitutes a valve seat, in such a way that it allows and prevents the atmospheric wind of the evaporation emon space from passing through the vent hole of the box; and two, comprises a rod 102 that provides a mounting for the one-way valve 86. The assembly comprises providing the rod 102 with a circular groove 104 that seats, and locates axially and radially, the valve 86 to be coaxial with respect to the rod. The valve 86 has a central passage hole 106 allowing it to be fixed on the rod 102 and to settle in the slot 104 in the manner shown and described. The detent 76 is provided as the upper axial end of a cylindrical sleeve 108 that is integrally formed with, and extends coaxially to the shaft 75 through, the wall 92 between the space circumferentially joined by the wall 98 and the chamber space 62. . It provides axial guidance for the travel of the plunger valve 88 allowing for a narrow sliding fit with the upper end of the rod 102. A second spiral helical spring 110 acting against the head 100 imparts a negative axial biasing force upwardly on the valve 88. of plunger causing the rounded upper end of the rod 102 to be held against the center of the movable wall 58 in the condition illustrated by Figure 2. The force exerted by the spring 110 is however insufficient with respect to the opposite force of the spring 74 for uncoupling the center portion of the movable wall 58 from the detent 76 in the condition of Figure 2; instead of the force of the spring 110 being selected to ensure that when the central region of the movable wall 58 is displaced upward more than a certain distance from the retainer 76, the spring 110 forces the contemporary closure of the open lower end of the wall 98 by the valve head 100 and the positioning of the valve 86 over the central region of the wall 92 which is circumferentially joined by the wall 98. The fragmentary view of Figure 3 shows the condition in which such displacement towards from wall 58 has occurred. The shapes of both the dome 96 and the head 100 provide the settlements for the respective ends of the spring 110. The head 100 is essentially a circular flange radially overlapping the opening at the lower end of the wall 98. To close that end in a sufficiently sealed, an annular seal 112 is on the face of the head 100 for sealing the circular rim of the wall 98. The central region of the wall 92 which is joined by the wall 98 is normally thickened, but contains a groove annular 114 which is axially open towards the valve 86 and one or more through holes 116 extending axially from the slot to the chamber space 62. The outer circular margin of the valve 86 radially overlaps the I.D. of the wall 98 such that in the position of Figure 3, the valve closes the chamber space 62 of the space surrounded by the wall 98. A solenoid valve 118 is positioned above the housing 56, as shown in the Figure 2. the valve 118 is like that described in commonly owned patent WO-A-94/15090 and comprises a solenoid which is connected through the connection 40 to the computer 16. In addition, the vacuum inlet orifice 48, the valve 18 comprises an atmospheric orifice (not shown) for communication with the ambient atmosphere and an exit orifice communicating with the chamber space 60 by means of an internal passage that is schematically represented at 117. In the position illustrated by Figure 2, the atmospheric orifice of valve 118 communicates to chamber space 60, which results in the latter being an atmospheric pressure. When the adenoid of the valve 118 is energized, the atmospheric orifice closes and the vacuum inlet orifice 48 opens, thereby communicating the vacuum inlet orifice 48 to the chamber space 60. The LDP has two additional components, namely a permanent magnet 124 and a tongue switch 126. The two are mounted on the outside of the housing wall on opposite sides from where the closed end of the sleeve 72 protrudes. The arrow 70 is a ferromagnetic material, and in the position of Figure 2, is positioned below the magnet and the reed switch where it does not interfere with the action of the magnet on the reed switch. However, as the arrow 70 moves upwardly within the sleeve 72, a point will be reached where sufficient magnetic flux from the magnet 124 derives, that the tab switch 126 does not remain further under the influence of the magnet, and therefore both the reed switch changes from one state to another. Assuming that the tongue switch changes from open to closed at such an exchange point, opening for the positions of arrow 70 below the point of the switch and closing for the positions of arrow 70 below the point of the switch. This switch point is however significantly below the upper limit of the travel of the arrow, such limit being defined in its particular mode by the tapering of the upper end of the arrow 70 with the closed end wall of the sleeve 72. For all travel upward of the arrow 70 above the switch point, the tab switch 126 remains closed. When the arrow 70 again travels down, the tongue switch 126 will change to open when the arrow reaches the point of change. The tongue switch 126 is connected to an output terminal 52 in such a way that the state of the tongue switch can be monitored by the computer 16 through the connection 54. Having described Figure 2 with sufficient detail, it can now be explained the operation of the invention. First, computer 16 orders that the CPS valve 20 be closed. It then energizes the valve 118 causing the intake manifold vacuum to be supplied through the valve 118 to the vacuum chamber space 60. For typical magnitudes of the intake manifold vacuum that exist when the engine is running, the area of the movable wall 58 is sufficiently large compared to the force exerted by the spring 74 such that the movable wall 58 is displaced upwardly. , thereby reducing the volume of the space 60 of the vacuum chamber in the process while simultaneously increasing the volume of the space 62 of the air pump chamber. The upward displacement of the movable wall 58 is limited by any suitable taper means and in this particular embodiment, as already mentioned, is by tapering the end of the arrow 70 with the closed end wall of the sleeve 72. The movement of the wall 58 away from the retainer 76 allows the spring 110 to concurrently push the rising plunger valve 88 in such a way that after an initial upward displacement of the wall 58, the head 100 of the plunger valve 88 closes the open end of the plunger valve 88. wall 98 and valve 86 is placed on wall 92 to function as a one-way valve to allow outward flow of chamber space 62, but not inwardly. The closing of the plunger valves of the open bottom end of the wall 93 closes the atmospheric vent to the vent hole of the box. As the volume of the space 62 of the air pumping chamber increases during upward movement of the movable wall 58, a certain pressure differential is created through the one-way valve 84 resulting in the opening of the valve at a relatively small pressure differential to allow atmospheric air to pass through orifice 44 into chamber space 62. When a sufficient amount of ambient atmospheric air has been drawn into the chamber space 62 to reduce the pressure differential through the valve 84 to a level that is insufficient to keep the valve open, the valve closes. At this time, the space 62 of the air pumping chamber contains an air charge that is substantially at ambient atmospheric pressure, i.e. a lower drop to atmospheric pressure through the valve 84. Under typical operating conditions , the time required for the atmospheric air to be created in the space 62 of the air pump chamber is well defined. This information is contained in the computer 16 and is used by the computer to determine the energization of the valve 118 after a time that is sufficiently long, but not appreciably long, to ensure that for all anticipated operating conditions, the space 62 of the chamber will be charged substantially at atmospheric pressure with the movable wall 58 in its upper travel position. The conclusion of the activation of the solenoid valve 118 by the computer 16 immediately causes the space 60 of the vacuum chamber to vent to the atmosphere. The pressure in the space 60 of the chamber now rapidly returns to the ambient atmospheric pressure, causing the net force acting on the movable wall 58 to be essentially uniquely that of the spring 74.

The force of the spring now moves the movable wall 58 downward compressing the air in the chamber space 62. When the air charge has been compressed sufficiently to create a certain pressure differential through the one-way valve 86, the latter opens. The continued displacement of the movable wall 58 by the spring 74 forces some compressed air into the space 62 of the chamber through the orifice 46 and in the evaporation emission space through the box vent hole. The spring 110 is strong enough to withstand the force of the compressed air such that the plunger valve 88 continues to prevent atmospheric venting of the box vent hole. When the movable wall 58 has moved down to r. point where the arrow 70 stops keeping the tongue switch 126 closed, the latter one opens. The opening of the switch is immediately detected by the computer 16 which immediately activates the solenoid of the valve 118 once again. Activation of the valve solenoid 118 now causes the manifold vacuum to be applied once more to the chamber space 60, reversing the movement of the movable wall 58 from the bottom up. The downward movement of the movable wall 58 between the position in which the arrow 70 tapers the closed end wall of the sleeve 72 and the position in which the tongue switch 126 changes from closed to open represents a compression time where a load of air in the space 62 of the chamber is compressed and a portion of the compressed load is pumped into the evaporation emission space. The upward movement of the movable wall 58 from a position in which the tongue switch 126 changes from open to closed to a position where the end of the arrow 62 tapers the closed end of the sleeve 70 represents an intake time. It is to be noted that the switch 126 will open before the movable wall 58 abuts the rounded end of the piston valve stem, and in this way it is ensured that the movable wall does not assume a position which on the one hand, prevents it from being taken at the intake time when the movable wall is intended to continue to move reciprocally after a compression time, and on the other hand, moves the plunger valve from the position of Figure 3. At the beginning of a diagnostic procedure , the pressure in the evaporation emission space will somehow be close to the atmospheric pressure, and therefore the time required for the spring 74 to force a portion of the charge from the space 62 of the chamber in the space Evaporation emission will be relatively short. This means that the movable wall 58 will execute a relatively fast compression time once the vacuum chamber 60 has been vented to the atmosphere by the valve 118. If a large leak is present in the evaporation emission space, the LDP 24 will be unable to develop pressure substantially at a predetermined level that is used in the procedure once the possibility of a large leak has been eliminated. Therefore, a continuous reciprocal rapid movement of the movable wall 58 for a period of time which is predetermined as sufficient to cause pressure to develop in the evaporation emission space substantially at the level at which a subsequent part of the process is performed, It will indicate the existence of a large leak, and the process can be completed at this juncture. Therefore, the frequency at which the switch 126 operates is used in the first case to determine whether or not a large leak is present, such a large leakage being indicated by the continued rapid activation of the switch during such predetermined period of time. If a large leak is not present, the pressure in the evaporation emission space will develop substantially to a predetermined amount, or objective level, which is essentially a function solely of the spring 74. In the theoretical case of an evaporation emission space whose leak is zero, a point will be reached where the spring 74 is unable to provide sufficient force to force the air compressed in the evaporation emission space. Consequently, switch 126 will cease to change when this occurs. If, once the target pressure has been substantially reached, there are some minor leaks than a large leak, the pump 24 will operate to maintain the pressure in the evaporation emission space by filling losses due to leakage. A speed at which the pump moves reciprocally is related to the size of the leak in such a way the larger the leak, the faster it will move reciprocally in the pump and the smaller the leak, the reciprocally it will move reciprocally. slower. The reciprocal movement speed is detected by the computer 16 by monitoring the speed at which the switch 126 changes. The operating speed of the switch can provide a fairly accurate measurement of the effective hole size of the leak. A leak that is greater than a predefined effective orifice size can be considered unacceptable while a smaller leak can be considered acceptable. In this form, the integrity of the evaporation emission space can either be confirmed or considered, even for relatively small effective orifice sizes. At the end of the process, computer 16 closes LDP 24 and allows the 20 CPS valve to reopen with a subsequent command.

The lack of integrity may be due to one or more reasons.- For example, there may be leakage from the fuel tank 14, the case 18, or any of the conduits 26, 30 and 34. Likewise, the failure of the valve 20 CPS to close completely during the procedure will also be a cause of leakage and can be detected. Although the mass of air that is pumped into the space of emission of evaporation to some extent will be an inverse function of the pressure in that space, the LDP can be considered a positive displacement pump due to the fact that it moves reciprocally for quite a while. well defined Figure 4 is a typical graph diagram illustrating how the present invention can provide a leak measurement. The horizontal axis represents a regime of effective leakage diameters, and the vertical axis represents a regime of pulse durations. In the case of the pumps that have been described, the duration of the pulse is defined as the time between the consecutive actions of the switch tongue 126 from open to closed, but it can be defined in other forms that are substantially equiva to this form or they provide substantially the same information. The chart diagram contains four graphs each of which represents the duration of the test as a function of the leakage diameter of a particular combination of three test conditions, such three conditions being the fuel level in the tank, the location of a Leak hole intentionally created, and the duration of the test. As can be seen, the four graphs coincide approximately each, proving that there is a definite relationship for the invention to provide a reasonably accurate leakage measurement, even for sizes that have quite small effective orifice diameters. This measurement capability allows the engine management computer, or any other on-board data record, to load the results of individual tests and create a test record that can be useful for various purposes. The computer's memory can be used as indicator means to load the test results. The car can also contain red indicators that attract the attention of the driver to the test results, such means indicators being a screen in the instrument panel. If a diagnostic process indicates that the evaporation emission system has integrity, it may be considered unnecessary for the test result to be automatically exposed to the driver; in other words, the automatic exposure of a test result can be given to the driver only in the case of an indication of non-integrity. A test result can be given in the form of an actual measurement and, or a simple indication of integrity or non-integrity. Because of the ability of the LDP to provide measurements of the size of the effective leak hole, it can be used to measure the performance of the CPS valve 20 and the flow through the system at the end of the diagnostic procedure that has been described herein. One way to accomplish this is that the computer 16 supplies a signal by rearranging a certain opening of the CPS valve 20, thus creating what a leak intentionally introduced means. If the CPS valve responds successfully, the LDP will reciprocate at a rate that substantially corresponds to the amount of the CPS valve opening that has been ordered. If there is a discrepancy, it will be detected by the computer, and an appropriate indication can be given. If no discrepancy is detected, that is an indication that the CPS valve and the system are functioning properly. Although the presently preferred embodiment of the invention has been illustrated and described, it will be appreciated that the principles are applicable to other embodiments that fall within the scope of the following claims. An example of such an embodiment may comprise an electrical actuator for striking the movable wall. Indeed, any particular embodiment of the invention for particular use is designed in accordance with the calculations and engineering techniques established, using materials suitable for the purpose.

Claims (18)

1. A reciprocating positive displacement pump for use in testing a portion of a fuel system of a motor vehicle powered by an internal combustion engine that consumes fuel in order to distinguish between the integrity and non-integrity of such a vehicle. portion of the fuel system, under conditions that lead to a reliable distinction between such integrity and non-integrity, against the leakage of such portion of the fuel system, such portion of the fuel system comprising a fuel tank, an emission space Cooperatively defined evaporation by a head space of the fuel tank and a vapcr collection box to temporarily collect the fuel vapors generated by the volatilization of fuel from the fuel tank, a box purge valve to periodically purge the vapors from fuel collected from the box to a multiple motor intake manifold for entrainment with fuel-air fuel mixture flow into the space of the combustion chamber of the engine and subsequent combustion in the space of the combustion chamber for driving the vehicle, and valve means comprising a vent valve through which the evaporation emission space communicates selectively to the atmosphere; the reciprocating positive displacement pump having a wall housing comprising an air pumping chamber space having movable wall, a non-movable wall separating such an air pumping chamber space from a wall housing containing such breather valve, the housing further comprising a first orifice adapted to communicate the interior of the housing to the evaporation emission space and a second orifice adapted to communicate the interior of the housing to the atmosphere, the pump further comprising a mechanical spring acting on the movable wall in a direction that urges the movable wall to contract the volume of the space of the air pumping chamber, the pump further comprising a first one-way valve means arranged to allow air to pass through the second hole from the atmosphere and that enters, but does not leave, the space of air pumping chamber, a second One-way valve means arranged to allow air to escape, but not enter, the air pumping chamber space and pass through said first orifice to the evaporation emission space, the effective means while the Valve means are closed, to avoid communication of the evaporation emission space to the atmosphere, and while the purge valve of the box is closed, avoid communication of the evaporation emission space to the intake manifold, to repeatedly cause the movable wall executes an intake time which expands the volume of the space of the air pumping chamber against the force exerted thereon by the mechanical spring, testing the opening of the first one-way valve means in the process, so that the air fills the space of the air pumping chamber to create a measured volume of air charge at a given pressure, and that imparts energy to such a spring for the subsequent execution of a compression time that contracts the volume of the space of the air pumping chamber by extracting energy from the spring to compress the measured load volume of air at a pressure greater than that given pressure, causing the opening of the second one-way valve means in the process, such that a portion of air in the space of the air pump chamber is forced into the evaporation emission space during a compression time, the first and second orifices which they have respective points of communication with the interior of the housing, one of the first and second one-way valve means being arranged, both when the vent valve is open and when the vent valve is closed, in operative association with a first set of one or more holes in the non-movable wall through which one of the first and second valve means a only direction controls the passage of air between the space of the air pump chamber and one of the first and second orifices, and the other of the first and second one-way valve means being arranged, when the vent valve is closed, in operative association with a second set of one or more holes in the non-movable wall through which the other of the first and second one-way valve means controls the air passage between the space of the air pump chamber and the other of the first and second orifices, characterized in that: the other of the first and second one-way valve means is arranged in such a way that when the breather valve ro is open, the other first and second one-way valve means is arranged outside of the operative association with the second set of one or more holes such that the air is able to pass both in and out of space of the air pumping chamber through the second sets of one or more holes.

2. The pump according to claim 1, further characterized in that the housing comprises a vacuum chamber space that is divided by the movable wall of the air pumping chamber space and because the pump comprises means for repeatedly causing the space of the The vacuum chamber is communicated alternately to the manifold of the intake manifold and to the atmosphere in such a way that during the communication of the vacuum chamber space to the vacuum of the intake manifold, such movable wall executes an intake time, and during the communication From the vacuum chamber space to the atmosphere, the mechanical spring forces the movable wall to execute a compression time.

3. The pump according to claim 2, further characterized in that the spring is placed in the vacuum chamber space, and in that the housing comprises a limit stop positioned within the vacuum chamber space to define a limit for the end of the vacuum chamber. an admission time of the movable wall.

4. The pump according to claim 3, further characterized in that the guiding means guides a central region of the movable wall for a straight line movement as it executes the intake and compression times, and because the detector means placed close to the guide means for detecting the position of the central region of the movable wall along the direction of such straight line movement.

5. The pump according to claim 1, further characterized in that in the first and second one-way valve means is the first one-way valve means and the other of the first and second one-way valve means is the second one-way valve means.

6. The pump according to claim 1, further characterized in that in the second one-way valve means ur.3 portion of the vent valve is mounted.

7. The pump according to claim 6, further characterized in that the vent valve comprises a head and a rod extending from the head, the wall housing comprising a seat on which the vent valve head sits when the valve The vent valve is closed and from which the vent valve head is disengaged when the vent valve is opened, and because the second one-way valve means is mounted on the vent valve stem.

8. The pump according to claim 7, further characterized in that in the second one-way valve means comprises a sunshade valve element that is mounted coaxially on the vent valve stem.

9. The pump according to claim 8, further characterized in that the elastic biased means resiliently biases the vent valve in a direction toward seating on the seat, and the vent valve stem is positioned to be actuated by the movable wall and the mechanical spring when the pump is not being operated in such a way that the vent valve is forced to be opened by the force of the mechanical spring acting on the vent valve being greater than the force of the biased elastic means biasing the valve of vent.

10. A fuel system of a motor vehicle characterized in that it comprises a pump according to claim 1, and that includes a fuel tank, an evaporation emission space, a box purge valve and valve means.

11. The fuel system of an automotive vehicle according to claim 10, further characterized in that the housing comprises a vacuum chamber space that is divided by the movable wall of the air pumping chamber space and in that the pump comprises means for causing repeatedly that the space of the vacuum chamber is communicated alternately to the manifold of intake manifold and to the atmosphere in such a way that during the communication of the vacuum chamber space to the vacuum of the intake manifold, such movable wall executes a time of admission, and during the communication of the vacuum chamber space to the atmosphere, the mechanical spring forces the movable wall to execute a compression time.

12. The fuel system of an automotive vehicle according to claim 11, further characterized in that the spring is placed in the vacuum chamber space, and in that the housing comprises a limit stop positioned within the vacuum chamber space to define a limit for the end of an admission time of the movable wall.

13. The fuel system of an automotive vehicle according to claim 12, further characterized in that the guiding means guides a central region of the movable wall for a straight line movement as it executes the intake and compression times, and because the sensor means positioned next to the guiding means for detecting the position of the central region of the movable wall along the direction of such straight line movement.

14. The fuel system of an automotive vehicle according to claim 10, further characterized in that in the first and second one-way valve means is the first one-way valve means and the other of the first and second valve means One-way valve is the second one-way valve means.

15. The fuel system of an automotive vehicle according to claim 10, further characterized in that a portion of the vent valve is mounted in the second one-way valve means.

16. The fuel system of an automotive vehicle according to claim 15, further characterized in that the vent valve comprises a head and a rod extending from the head, the wall housing comprising a seat on which the valve head The vent valve is seated when the vent valve is closed and from which the vent valve head is disengaged when the vent valve is opened, and because the second one-way valve means is mounted on the valve stem of the vent valve. vent.

17. The fuel system of an automotive vehicle according to claim 16, further characterized in that in the second one-way valve means comprises a parasol valve element that is mounted coaxially on the vent valve stem.

18. The fuel system of an automotive vehicle according to claim 17, further characterized in that the elastic biased means resiliently biases the vent valve in a direction toward seating on the seat, and the vent valve stem is positioned to be operated by the movable wall and the mechanical spring when the pump is not being operated in such a way that the vent valve is forced to be opened by the force of the mechanical spring acting on the vent valve being greater than the force of the means slanted elastic biasing the vent valve.