LPG fuel composition estimation method and system

• US 6,766,269 B2
• Filed: 12/30/2002
• Issued: 07/20/2004
• Est. Priority Date: 05/20/2002
• Status: Expired due to Fees

• Current Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Inventors: Lee, Woo-Jik
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US10/331,226
• Publication Number:
  US 20030216883A1
• Time in Patent Office: 568 Days
• Field of Search: 732/041.1, 73/20, 73/42.2, 732/042.4, 732/04, 123/526, 123/527, 123/478, 123/301, 123/27.GE, 702/136
• US Class Current: 702/136
• CPC Class Codes: F02B 2275/16 Indirect injection
• CPC Class Codes: F02D 19/022 to adjust the fuel pressure, temperature or composition
• CPC Class Codes: F02D 19/024 by controlling fuel injectors
• CPC Class Codes: F02D 19/027 Determining the fuel pressure, temperature or volume flow, the fuel tank fill level or a valve position
• CPC Class Codes: F02D 19/029 Determining density, viscosity, concentration or composition
• CPC Class Codes: F02D 2200/0611 Fuel type, fuel composition or fuel quality
• CPC Class Codes: F02D 41/0027 the fuel being gaseous non-electrical control F02D19/02
• CPC Class Codes: F02M 21/0212 comprising at least 3 C-Atoms, e.g. liquefied petroleum gas [LPG], propane or butane
• CPC Class Codes: F02M 69/044 for injecting into the intake conduit downstream of an air throttle valve
• CPC Class Codes: G01N 33/225 Gaseous fuels, e.g. natural gas
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

A Liquefied Petroleum Gas (LPG) fuel composition estimation method is provided that determines an LPG fuel composition from saturation vapor pressure data and an estimated fuel temperature and fuel pressure inside the fuel tank. A Liquefied Petroleum Gas Injection (LPI) System that employs the method is provided that employs the method of the invention.

Claims

1. A liquefied petroleum gas (LPG) fuel composition estimation method for an LPG injection (LPI) system, comprising:

detecting a fuel pressure inside a fuel supply line, a fuel temperature inside the fuel supply line, a coolant temperature, and an intake air temperature at an ignition-on state;

determining whether predetermined conditions exist between the detected temperatures;

detecting the fuel temperature and the fuel pressure inside the fuel supply line at predetermined intervals;

determining a fuel temperature and a fuel pressure inside a fuel tank based on the detected fuel temperature and fuel pressure inside the fuel supply line, if it is determined that the predetermined conditions exist; and

determining an LPG fuel composition from saturation vapor pressure data based on the determined fuel temperature and fuel pressure inside the fuel tank.

2. The LPG composition estimation method of claim 1, wherein the predetermined conditions comprise:

a first temperature difference between the fuel temperature inside the fuel supply line and the coolant temperature at the ignition-on state is less than a first predetermined value;

a second temperature difference between the fuel temperature inside the fuel supply line and the intake air temperature at the ignition-on state is less than a second predetermined value; and

a third temperature difference between the coolant temperature and the intake air temperature is less than a third predetermined value.

3. The LPG composition estimation method of claim 1, wherein the determining a fuel temperature and a fuel pressure inside a fuel tank comprises:

calculating an average fuel pressure of a predetermined number of detected fuel pressures in the fuel supply line;

determining whether predetermined estimation conditions exist for an estimation of a fuel pressure and a fuel temperature inside the fuel tank; and

setting the fuel temperature inside the fuel tank as the fuel temperature inside the fuel supply line, and setting the fuel pressure inside the fuel tank as a pressure difference between the average fuel pressure and a pressure regulator control pressure, if it is determined that the predetermined estimation conditions exist.

4. The LPG fuel composition estimation method of claim 3, wherein if a difference between a current fuel temperature inside the fuel supply line and the fuel temperature inside the fuel supply line at the ignition-on state is not less than a predetermined value, it is determined that the predetermined estimation conditions do not exist.

5. The LPG fuel composition estimation method of claim 3, wherein if a difference between a current fuel temperature inside the fuel supply line and the fuel temperature inside the fuel supply line at the ignition-on state is not less than a predetermined value, a fuel pump speed is not lower than a predetermined speed, or a difference between the calculated average pressure and a calculated average pressure from a previous routine is not less than a predetermined average pressure value, it is determined that the predetermined estimation conditions do not exist.

6. An LPG composition estimation system for an LPI system, comprising:

a fuel tank for storing LPG fuel;

a fuel pump disposed inside the fuel tank, the fuel pump pressurizing the LPG fuel;

an injector connected to the fuel pump via a fuel supply line;

a pressure regulator disposed in a fuel return line connecting the injector and the fuel tank;

a detecting unit for detecting one or more engine operating parameters and generating corresponding signals; and

a control unit receiving the signals of the detecting unit and estimating an LPG fuel composition, the control unit being programmed to execute a method comprising;

detecting a fuel pressure inside a fuel supply line, a fuel temperature inside the fuel supply line, a coolant temperature, and an intake air temperature at an ignition-on state;

determining whether predetermined conditions fall within differences between the detected temperatures;

detecting the fuel temperature and the fuel pressure inside the fuel supply line at intervals;

determining a fuel temperature and a fuel pressure inside a fuel tank based on the detected fuel temperature and fuel pressure inside the fuel supply line; and

determining an LPG fuel composition from saturation vapor pressure data based on the determined fuel temperature and fuel pressure inside the fuel tank.

7. The LPG composition estimation system of claim 6, wherein the detecting unit comprises:

an ignition detector detecting whether a current state is an ignition-on state, an engine-operating state, or an engine-off state;

a fuel pressure detector for detecting a fuel pressure inside a fuel supply line;

a fuel temperature detector for detecting a fuel temperature inside the fuel supply line;

a coolant temperature detector for detecting a temperature of coolant;

an intake air temperature detector for detecting a temperature of intake air; and

a fuel pump speed detector for detecting a speed of the fuel pump.

8. The LPG fuel composition estimation system of claim 6, wherein the predetermined conditions comprise:

a first temperature difference between the fuel temperature inside the fuel supply line and the coolant temperature at the ignition-on state is less than a first predetermined value;

a second temperature difference between the fuel temperature inside the fuel supply line and the intake air temperature at the ignition-on state is less than a second predetermined value; and

a third temperature difference between the coolant temperature and the intake air temperature is less than a third predetermined value.

9. The LPG fuel composition estimation system of claim 6, wherein the determining a fuel temperature and a fuel pressure inside a fuel tank comprises:

calculating an average fuel pressure of a predetermined number of detected fuel pressures in the fuel supply line;

determining whether predetermined estimation conditions exist for an estimation of a fuel pressure and a fuel temperature inside the fuel tank; and

setting the fuel temperature inside the fuel tank as the fuel temperature inside the fuel supply line, and setting the fuel pressure inside the fuel tank as a pressure difference between the average fuel pressure and a pressure regulator control pressure, if it is determined that the predetermined estimation conditions exist.

10. The LPG fuel composition estimation system of claim 9, wherein if a difference between a current fuel temperature inside the fuel supply line and the fuel temperature inside the fuel supply line at the ignition-on state is not less than a predetermined value, it is determined that the predetermined estimation conditions do not exist.

11. The LPG fuel composition estimation system of claim 9, wherein if a difference between a current fuel temperature inside the fuel supply line and the fuel temperature inside the fuel supply line at the ignition-on state is not less than a predetermined value, a fuel pump speed is not lower than a predetermined speed, or a difference between the calculated average pressure and a calculated average pressure from a previous routine is not less than a predetermined average pressure value, it is determined that the predetermined estimation conditions do not exist.