摘要:
A leak detection method for an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of a fuel system of an automotive vehicle. During a leak detection test, a vent valve closes, and a purge valve, that selectively communicates the evaporative emission space with the engine intake manifold, opens to cause vacuum to be drawn in the evaporative emission space. A vacuum regulator valve regulates evaporative emission space vacuum to a defined vacuum. Subsequently, the purge valve closes. Loss of vacuum, indicative of leakage, is signaled by a pressure sensor. An algorithm detects a substantially constant rate of vacuum loss and then measures the amount of loss over a defined time interval. That measurement is then compensated for volume of the evaporative emission space and rate of fuel volatilization to arrive at a value forming a basis for making a leakage determination.
摘要:
An on-board diagnostic system for an evaporative emission control system of an internal combustion engine powered vehicle employs a leak detection module that is fluid connected in a vent passage for the evaporative emission space. The leak detection module contains an electric motor driven impeller, a solenoid operated valve assembly that is selectively operable to three positions, and a pressure-responsive switch whose switching characteristic possesses hysteresis corresponding to an upper regulating limit and a lower regulating limit. The valve assembly operates to allow the prime mover to pump gaseous fluid with respect to the evaporative emission space to attain a test pressure in the evaporative emission space corresponding to the upper regulating limit, to close the evaporative emission space and prevent the prime mover from pumping gaseous fluid with respect to the evaporative emission space upon initially attaining the upper regulating limit test pressure within the evaporative emission space, and which allows the prime mover to pump gaseous fluid with respect to the evaporative emission space at a pre-defined volumetric flow rate to rebuild pressure in the evaporative emission space to the upper regulating limit when the pressure has changed to the lower regulating limit due to a leak in the evaporative emission space.
摘要:
A module for an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of a fuel system of an automotive vehicle. The module has a housing that includes a first port for communicating the housing to the evaporative emission space and a second port for communicating the housing to atmosphere. The housing contains a particulate filter through which the second port communicates with two parallel flow branches that extend within the housing to the first port. One branch contains a vacuum regulator valve, and the other, a solenoid-operated vent valve. During a leak detection test, the vent valve is operated closed, and a purge valve, that selectively communicates the evaporative emission space with the engine intake manifold, is operated open to cause vacuum to be drawn in the evaporative emission space. The vacuum regulator valve regulates evaporative emission space vacuum to a defined vacuum. Subsequently, the purge valve is operated closed. Leakage is evidenced by loss of vacuum, and a pressure sensor signals vacuum loss.
摘要:
A leak detection system for detecting leakage from a portion of a vapor confinement space which is upstream of an inlet of a canister purge valve relative to an engine. During a test, an electric-motor-operated air pump pumps atmospheric air through a flowpath providing communication between the pump and the vapor confinement space. A flowmeter has a thermistor in the flowpath. The thermistor has a predetermined temperature vs. electric current characteristic that enables it to provide a signal correlated to flow of air through the flowpath. An electric circuit supplies and measures the electric current drawn by the thermistor to create a signal representative of the pumped airflow. The test is conducted in accordance with an algorithm that pre-heats the thermistor to a stable state before the pump is turned on. The pump is then turned on to create a predefined superatmospheric target pressure in the vapor confinement space. Once the target pressure is reached, the airflow measured by the flowmeter provides a leakage measurement. The pump is then shut off and the vapor space vented to atmosphere through the flowmeter and pump. The thermistor current draw is once again measured to detect any drift in its characteristic.
摘要:
The purge valve embodies a solenoid that has a linear force vs. current characteristic acting on the armature. Effects of hysteresis are minimized by certain constructional features and the manner of operating the valve by an associated control circuit.
摘要:
A method and sensor or sensor subsystem permit improved evaporative leak detection in an automotive fuel system. The sensor or sensor subsystem computes temperature-compensated pressure values, thereby eliminating or reducing false positive or other adverse results triggered by temperature changes in the fuel tank. The temperature-compensated pressure measurement is then available for drawing an inference regarding the existence of a leak with reduced or eliminated false detection arising as a result of temperature fluctuations.
摘要:
A leak detection monitor (22; 222) for an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of a fuel system of an automotive vehicle. One embodiment (22) utilizes engine intake system vacuum to vent the evaporative emission space to atmosphere when the engine is running; another (222), an electromagnet actuator (270, 280). Venting ceases when the engine is shut off. Changes in vapor pressure in the evaporative emission space are monitored over time by electric devices (74; 282) after the engine has been shut off to distinguish between a gross leak, a small leak smaller than a gross leak, and a leak that is at most smaller than a small leak.
摘要:
A method of calibrating an integrated pressure management apparatus having a chamber with an interior volume varying in response to fluid pressure in the chamber. A diaphragm partially defining the chamber is displaceable between first and second configurations in response to fluid pressure variations around a certain pressure level. A resilient element applies a force biasing the diaphragm a first configuration and a switch is actuated by the diaphragm in the second configuration. The method includes connecting the chamber to a pressure source at a known pressure level, and adjusting resilient element such that the switch is actuated at the known pressure level.
摘要:
A diaphragm for an integrated pressure management system manages pressure and detects leaks in a fuel system. The integrated pressure management system also performs a leak diagnostic for the headspace in a fuel tank, a canister that collects volatile fuel vapors from the headspace, a purge valve, and all associated hoses and connections.
摘要:
A module for an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of a fuel system of an automotive vehicle. Interior space of the module's enclosure is communicated to atmosphere. A pump is disposed within space and has an inlet communicated to the interior space and a flow passage at its outlet to allow the pump to create pressure in the evaporative emission space suitable for performance of a leak test. A vent valve is disposed within space and is selectively operable to vent and not vent the flow passage to space. An electromagnet actuator has a single electric coil that operates both the pump and the vent valve by cantilever-mounted armatures responsive to electric control current in the coil having a first current component for controlling the pump and a second current component for controlling the vent valve.