Patent Grant
7373799
The present invention relates generally to vehicle fuel systems and more particularly to diagnosing conditions in vehicle fuel tanks.
Vacuum/pressure sensors are commonly used in vehicle fuel tanks to monitor tank vacuum levels. When a vacuum/pressure sensor fails to operate properly, the sensor may indicate a constant vacuum level, even while vacuum is actually being increased (i.e., pressure is being reduced) in the tank. If a vacuum/pressure sensor fails to operate and its failure is not detected, the fuel tank can become damaged when excessive vacuum is applied. On the other hand, a properly operating vacuum sensor may register a constant vacuum level when a leak in the tank is sufficiently large to prevent vacuum in the tank from increasing.
The present invention, in one embodiment, is directed to a method of determining whether a vacuum/pressure sensor in a vehicle fuel tank correctly indicates a vacuum level in the tank. An input from the sensor is obtained. The tank is sealed for a predetermined time period. After the time period, another input is obtained from the sensor and the sensor inputs are compared.
In another configuration, the invention is directed to a method of determining whether a vacuum/pressure sensor in a vehicle fuel tank correctly indicates a vacuum level in the tank. The method includes determining a target vacuum level to be reached in the tank. A first value is obtained from the sensor. It is determined whether the first value indicates that the target vacuum level is being reached. Based on the determining, the following steps are performed. A second value is obtained from the sensor. The tank is sealed for a predetermined time period. After the time period, a third value is obtained from the sensor and the second and third values are compared.
In another configuration, a system for determining whether a vacuum/pressure sensor in a vehicle fuel tank correctly indicates a vacuum level in the tank includes a control module that determines a target vacuum level to be reached in the tank. The control module obtains a first indication from the sensor and determines whether the first indication indicates that the target vacuum level is being reached. Based on the determination, the control module obtains a second indication from the sensor and seals the tank for a predetermined time. After the predetermined time, the control module obtains a third indication from the sensor and compares the second indication with the third indication.
In yet another configuration, a diagnostic system in a vehicle includes a vacuum/pressure sensor in a fuel tank of the vehicle. A control module obtains an indication from the sensor and seals the tank for a predetermined time. After the predetermined time, the control module obtains another indication from the sensor and compares the sensor indications to determine whether the sensor correctly indicates a vacuum level in the tank.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of various embodiments of the present invention is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module and/or device refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality.
Referring now to
The engine 22 includes a plurality of cylinders 52 that receive fuel from the fuel injectors 32 to drive a crankshaft 58. Vapor from the fuel tank 26 is collected in a charcoal storage canister 60. The canister 60 may be vented to air through a vent valve 62. The canister 60 may be purged through a purge valve 64. When vapor is purged from the canister 60, it is delivered to the intake manifold 34 and burned in the engine cylinders 52. The control module 42 controls operation of the vent valve 62, purge valve 64, fuel injectors 32 and ignition system 54. A catalytic converter 68 receives exhaust from the engine 22 through an exhaust manifold 70. An exhaust sensor 72 senses exhaust in the manifold 70 and delivers a signal to the control module 42.
The fuel tank 26 is shown in greater detail in
In one configuration of the present invention, the control module 42 monitors operation of the pressure/vacuum sensor 120 during operation of the vehicle 20. A target vacuum level in the tank 26 is determined and a plurality of values are obtained from the sensor 120. If the values received from the sensor 120 during vehicle operation indicate a steady value and/or indicate that the target vacuum level is not being reached, the control module 42 performs further diagnostics as further described below.
Implementations of the foregoing method may be further explained with reference to a graph indicated generally by reference number 200 in
When a small leak is present in the tank 26 and the sensor 120 is operating properly, the sensor 120 produces values indicated by a curve 228. The target vacuum level 216 can be reached at time 220 when vacuum is applied to the tank 26 in the presence of a small leak. When the tank 26 is sealed at the time 220, however, the tank vacuum level decreases gradually over time, at a rate faster than in the absence of a leak.
When a large leak is present in the tank 26 and the sensor 120 is operating properly, the sensor 120 produces values indicated by a curve 232. The target vacuum level 216 cannot be reached when vacuum is applied to the tank 26 in the presence of a large leak. For example, a vacuum indicated by point 234 is a maximum vacuum that can be reached in the tank 26. When the tank is sealed at time 220, the tank vacuum level decreases rapidly relative to the small leak curve 228. Thus the term “large leak”, as used herein, refers to a leak that prevents a target vacuum from being reached. A “small leak”, as used herein, refers to a leak that does not prevent a target vacuum from being reached.
When the pressure/vacuum sensor 120 begins to fail, it may, for example, sense a particular pressure/vacuum and then “get stuck”, i.e., become unable to indicate other values. Referring to
A flow diagram of an exemplary method of determining whether the vacuum/pressure sensor 120 correctly indicates a vacuum level in the tank 26 is indicated generally in
In step 308, the control module 42 obtains a plurality of pressure/vacuum indications from the vacuum sensor 120 over an applicable time period. An “applicable time period” may be, for example, one or more ignition cycles of the engine 22, all or part of a time period associated with achieving the particular target vacuum level, and/or other or additional time period(s) over which the sensor 120 indications would be sufficient to indicate whether the target vacuum level is being reached.
In step 312, the control module 42 determines whether the values obtained from the sensor 120 are stable, that is, whether they indicate a steady value. If in step 312 it is determined that the sensor 120 values do not indicate a steady value, control passes to step 316. It should be understood that the term “steady value” in the present context refers to an essentially steady value, subject to any variation that might be appropriately included in the sensor 120 value when evaluating a possible stuck sensor.
If in step 312 the sensor 120 values indicate that a vacuum in the tank 26 has reached a steady value, then in step 320 the control module 42 stores a fault indication in its memory and issues a warning of a possible large leak or a failing vacuum/pressure sensor. After the warning is issued in step 320, control passes to step 330.
In step 316, the control module 42 determines whether the values obtained from the sensor 120 indicate that the target vacuum level is being reached or has been reached. If the target vacuum level is being or has been reached, control exits from the method 300. If in step 316 it is determined that the target vacuum level is not being reached, then in step 320 the control module 42 stores a fault indication in its memory and causes a warning message to be displayed. Control then passes to step 330.
In step 330, the control module 42 seals the fuel tank 26 and sets a timer (not shown) for a predetermined time. The time period over which the tank 26 remains sealed is sufficiently long to allow a vacuum level in the tank 26 to decrease to a low level in the event of a large leak in the tank 26. A “low” level includes a level (such as that indicated by line 232 in
In step 342, the control module 42 obtains a subsequent indication from the vacuum/pressure sensor 120. In step 346, the subsequent sensor indication is compared with the value previously indicated by the sensor 120 in step 334. If the subsequent indication is essentially equal to the previous sensor value, then in step 350 the control module 42 indicates that the sensor 120 is failing. If the subsequent sensor value indicates that a vacuum level in the tank 26 has reached a low level compared to the previous sensor value, then in step 354 the control module 42 indicates that a large leak is present in the tank 26.
Implementations of the foregoing method and system can be used to detect a failing pressure/vacuum sensor, which previously was not possible to detect during vehicle operation. Because a failing sensor can be detected sooner than previously possible, excessive vacuum in a fuel tank can be prevented. Replacing a sensor is less expensive than replacing a damaged fuel tank, and so repair costs are reduced.
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and the following claims.
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| Number | Date | Country | |
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| 20060081035 A1 | Apr 2006 | US |
