초록 ▼

A fuel injection system for automotive diesel engine is provided which is equipped with a fuel pressure sensor working to measure the pressure of fuel in an accumulator and a pressure-reducing valve working to drain the fuel from the accumulator. The system is designed to ensure enhanced reliability

A fuel injection system for automotive diesel engine is provided which is equipped with a fuel pressure sensor working to measure the pressure of fuel in an accumulator and a pressure-reducing valve working to drain the fuel from the accumulator. The system is designed to ensure enhanced reliability of diagnosis of the pressure-reducing valve. The system works to make a temporal diagnosis of the pressure-reducing valve based on the behavior of the pressure in the accumulator upon opening of the pressure-reducing valve after an ignition switch is turned off. After elapse of a given period of time, when it is determined that a value of the pressure in the accumulator, as measured by the fuel pressure sensor, lies near the atmospheric pressure, the system determines that the fuel pressure sensor is operating properly and fixes the temporal diagnosis of the pressure-reducing valve ultimately.

대표청구항 ▼

What is claimed is: 1. A fuel injection system for an internal combustion engine comprising: an accumulator storing therein fuel under a given pressure which is to be injected into an engine; a fuel pump working to pressurize and supply the fuel to said accumulator; a fuel injector working to injec

What is claimed is: 1. A fuel injection system for an internal combustion engine comprising: an accumulator storing therein fuel under a given pressure which is to be injected into an engine; a fuel pump working to pressurize and supply the fuel to said accumulator; a fuel injector working to inject the fuel in said accumulator into the engine; a fuel pressure sensor working to measure a pressure of the fuel in said accumulator to output a signal indicative thereof; a pressure-reducing valve working to drain the fuel from said accumulator to a fuel tank to decrease the pressure of the fuel in said accumulator; and a controller working to monitor the signal outputted from said fuel pressure sensor to control the pressure in said accumulator, said controller including a first diagnostic circuit and a second diagnostic circuit, the first diagnostic circuit working to diagnose said fuel pressure sensor, the second diagnostic circuit working to monitor a behavior of the pressure in said accumulator, as measured by said fuel pressure sensor when activating said pressure-reducing valve to diagnose said pressure-reducing valve, when a first condition in which the monitored behavior of the pressure in said accumulator is different from a behavior of the pressure in said accumulator, as expected when said pressure-reducing valve is operating properly, and a second condition in which said first diagnostic circuit has diagnosed that said fuel pressure sensor is operating properly are both met, said second diagnostic circuit determining that said pressure-reducing valve is failing in operation thereof; and wherein the second diagnostic circuit works to open said pressure-reducing valve upon turning off of an ignition switch of a vehicle in which the engine is mounted and diagnose whether said pressure-reducing valve is operating properly or not based on the behavior of the pressure in said accumulator arising from opening of said pressure-reducing valve and a result of diagnosis of said fuel pressure sensor made by the first diagnostic circuit. 2. A fuel injection system as set forth in claim 1, wherein the first diagnostic circuit works to compare a value of the pressure in said accumulator, as measured by said fuel pressure sensor after elapse of a given period of time following the turning off of the ignition switch, with an atmospheric pressure to diagnose whether said fuel pressure sensor is operating properly or not, and wherein said second diagnostic circuit also works to make a temporal diagnosis of said pressure-reducing valve based on the behavior of the pressure in said accumulator arising from the opening of said pressure-reducing valve, when a condition in which the temporal diagnosis that said fuel pressure sensor is operating properly is made and the second condition are both met, said second diagnostic circuit determining that said pressure-reducing valve is failing in operation thereof. 3. A fuel injection system as set forth in claim 2, wherein said controller is designed to sample a temperature of a coolant of the engine, and wherein said first diagnostic circuit works to extend the given period of time as the temperature of the coolant decreases. 4. A fuel injection system as set forth in claim 2, wherein said controller is designed to sample a temperature of the fuel, and wherein said first diagnostic circuit works to extend the given period of time as the temperature of the fuel decreases. 5. A fuel injection system as set forth in claim 2, wherein the second diagnostic circuit works to use a given criterion for making the temporal diagnosis that said pressure-reducing valve is failing in operation thereof and vary the given criterion as a function of the pressure in said accumulator. 6. A fuel injection system as set forth in claim 2, wherein said controller is designed to sample a temperature of a coolant of the engine, and wherein the second diagnostic circuit works to use a given criterion for making the temporal diagnosis that said pressure-reducing valve is failing in operation thereof and vary the given criterion as a function of the temperature of the coolant. 7. A fuel injection system as set forth in claim 2, wherein said controller is designed to sample a temperature of the fuel, and wherein the second diagnostic circuit works to use a given criterion for making the temporal diagnosis that said pressure-reducing valve is failing in operation thereof and vary the given criterion as a function of the temperature of the fuel. 8. A fuel injection system as set forth in claim 2, wherein after the turning off of the ignition switch, said second diagnostic circuit works to make the temporal diagnosis of said pressure-reducing valve before the elapse of the given period of time after when the value of the pressure in said accumulator, as measured by said fuel pressure sensor, is sampled by the first diagnostic circuit for diagnosing said fuel pressure sensor, and wherein when the condition in which the temporal diagnosis that said fuel pressure sensor is operating properly is made and the second condition are both met, said second diagnostic circuit determines that said pressure-reducing valve is failing in operation thereof after the first diagnostic circuit diagnoses whether said fuel pressure sensor is operating properly or not. 9. A fuel injection system as set forth in claim 8, wherein when the second diagnostic has made the temporal diagnosis that said pressure-reducing valve is failing in operation thereof, the first diagnostic circuit works to extend the given period of time to be longer than that when the second diagnostic has made the temporal diagnosis that said pressure-reducing valve is operating properly. 10. A method for fuel injection in an internal combustion engine, said method comprising: pressurizing and supplying fuel to an accumulator where it is stored under a given pressure for injection into an engine; injecting fuel from said accumulator into the engine; measuring pressure of the fuel in said accumulator and outputting a signal indicative thereof; draining fuel from said accumulator to a fuel tank via a pressure-reducing valve to decrease the pressure of fuel in said accumulator; and monitoring the output fuel pressurization to control the pressure in said accumulator; diagnosing a fuel pressure sensor used in said measuring step; monitoring a behavior of the pressure in said accumulator, as measured by said fuel pressure sensor when activating said pressure-reducing valve to diagnose said pressure-reducing valve when a first condition in which the monitored behavior of the pressure in said accumulator is different from a behavior of the pressure in said accumulator, as expected when said pressure-reducing valve is operating properly, and a second condition in which said diagnosing step has determined that said fuel pressure sensor is operating properly are both met, determining that said pressure-reducing valve is failing in operation; and wherein said pressure-reducing valve is opened upon turning off of an ignition switch of a vehicle in which the engine is mounted and diagnosing whether said pressure-reducing valve is operating properly or not based on behavior of the pressure in said accumulator arising from opening of said pressure-reducing valve and a result of diagnosis of said fuel pressure sensor. 11. A method as in claim 10 wherein: a value of the pressure in said accumulator, as measured by said fuel pressure sensor after elapse of a given period of time following the turning off of the ignition switch, is compared with an atmospheric pressure to diagnose whether said fuel pressure sensor is operating properly or not, and a temporal diagnosis of said pressure reducing valve is made based on the behavior of the pressure in said accumulator arising from the opening of said pressure-reducing valve, when a condition in which the temporal diagnosis that said fuel pressure sensor is operating properly is made and the second condition are both met, determining that said pressure-reducing valve is failing in operation thereof. 12. A method as in claim 11 wherein a temperature of a coolant of the engine is sampled, and wherein the given period of time is extended as the temperature of the coolant decreases. 13. A method as in claim 11 wherein a temperature of the fuel is sampled, and wherein the given period of time is extended as the temperature of the fuel decreases. 14. A method as in claim 11 wherein given criterion is used for making the temporal diagnosis that said pressure-reducing valve is failing in operation thereof and the given criterion is varied as a function of the pressure in said accumulator. 15. A method as in claim 11 wherein a temperature of a coolant of the engine is sampled and wherein a given criterion is used for making the temporal diagnosis that said pressure-reducing valve is failing in operation thereof and the given criterion is varied as a function of the temperature of the coolant. 16. A method as in claim 11 wherein a temperature of the fuel is sampled, and wherein a given criterion is used for making the temporal diagnosis that said pressure-reducing valve is failing in operation thereof and the given criterion is varied as a function of the temperature of the fuel. 17. A method as in claim 11 wherein after the turning off of the ignition switch, the temporal diagnosis of said pressure-reducing valve is made before the elapse of the given period of time after which the value of the pressure in said accumulator, as measured by said fuel pressure sensor, is sampled for diagnosing said fuel pressure sensor, and wherein when the condition in which the temporal diagnosis that said fuel pressure sensor is operating properly is made and the second condition are both met, it is determined that said pressure-reducing valve is failing in operation thereof after it has been diagnosed whether said fuel pressure sensor is operating properly or not. 18. A method as in claim 17 wherein when the temporal diagnosis that said pressure-reducing valve is failing in operation thereof has been made, the given period of time is extended to be longer than that when the temporal diagnosis has been made that said pressure-reducing valve is operating properly.