GB2397137A

GB2397137A - A control for an internal combustion engine

Info

Publication number: GB2397137A
Application number: GB0300344A
Authority: GB
Inventors: Andy Wicks
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2003-01-08
Filing date: 2003-01-08
Publication date: 2004-07-14
Anticipated expiration: 2023-01-08
Also published as: GB2397137B; GB0300344D0

Abstract

An internal combustion engine (11) has an air inlet manifold (15) supplying air to combustion chambers (22), fuel injectors (12) supplying fuel to said chambers (22) and an ECU (16) controlling the operation of the engine, the ECU (16) being connected to a plurality of engine condition sensors (17-19). In a method of controlling the engine (11), the ECU (16) is pre-programmed with parameters relating to the dynamic air pressure proximate to each injector (12) and the mass air flow past each injector (12). The ECU (16) monitors the engine condition sensors, ascertains the dynamic air pressure and air mass flow at each injector (12) and, depending upon the sensed conditions, calculates the timing and period of fuel injection pulses and sends control signals to the fuel injectors.

Description

A control for an Internal Combustion Engine

Field

This invention relates to a method of control of an internal combustion engine for a vehicle, and in particular to the control of fuel injectors. s

Background of the Invention

Fuel injectors may be operated to inject fuel into respective inlet ports of combustion chambers of internal combustion engines. The amount of fuel injected and the timing of the fuel injection is typically controlled by a pre-programmed electronic engine control unit (ECU). Conventionally the ECU is connected to a plurality of engine condition sensors and is pre-programmed with various parameters and algorithms which enable the ECU to control the fuel injection. These parameters typically include the static air pressure in the inlet manifold which is used as a reference when inferring or measuring the "delta injection pressure" (that is the pressure difference from the fuel inlet to fuel outlet of the injector).

Furthermore, the mass air flow to the engine is assumed to be equally divided between the combustion chambers and in some engines the design of the inlet manifold and inlet port may lead to cylinder-to-cylinder differences in air charge mass or velocity.

The above assumptions and choice of parameters take no account of inlet port differences and therefore will not provide for an optimum air/fuel ratio for each respective combustion chamber.

Object of the present Invention The present invention provides an improved control for the air/fuel ratio into each cylinder.

Statement of Invention

According to one aspect of the present invention there is provided a method of control of a motor vehicle internal combustion engine having at least one air inlet manifold supplying air to the engine combustion chambers, fuel injectors supplying fuel to said chambers, and an electronic engine control unit (ECU) controlling the operation of the engine and being connected to a plurality of engine condition sensors, wherein the ECU is pre-programmed with parameters relating to the dynamic air pressure at the tip of each injector and parameters relating to the mass air flow past each injector, monitors the engine condition sensors, ascertains the dynamic air pressure and air mass flow proximate each injector, preferably at the tip thereof, and, depending upon the sensed conditions, calculates the timing and period of the injection pulses for the respective injectors and sends control signals to the fuel injectors.

Modelling the actual air flow past each injector provides an improved control of the fueVair ratio for each individual combustion chamber.

The engine condition sensors may include, but are not limited to, sensors which monitor engine position, engine speed, manifold static pressure, mass air flow into the manifold, engine temperature, air temperature, camshaft position (inlet and exhaust), inlet manifold tuning valves, EGR amount, variable cam timing (VCT) position, etc..

The ECU ascertains the dynamic air pressure and air mass flow at the tips of the respective injectors.

The ECU then models transient airflow behaviour to predict real time airflow based on sensed engine conditions and pre-programmed information in the form of algorithms and look-up tables which reference engine position, engine speed, manifold static pressure, mass air flow into the manifold, engine temperature, air temperature, camshaft position (inlet and exhaust), inlet manifold tuning valves, EGR amount, VCT position, etc The timing and period for the fuel injection are then determined in steps, comprising: calculating the optimum end of injection time for each cylinder based on pre-programmed information based on algorithms and lookup tables referencing engine speed, engine load, VCT position, and engine temperature, calculating the pulse width for each cylinder based on preprogrammed information based on algorithms and look-up tables referencing fuel rail pressure, delta injection pressure, and mass of fuel required, and hence calculating the start of the injection time for each cylinder.

The control signals to the fuel injectors may be adjusted in line with transient conditions.

According to a further aspect of the invention there is provided an internal combustion engine having at least one air inlet manifold supplying air to the engine combustion chambers, fuel injectors supplying fuel to said chambers and an electronic engine control unit (ECU) controlling the operation of the engine and being connected to a plurality of engine condition sensors, wherein the ECU is pre-programmed with parameters relating to the dynamic air pressure proximate to each injector and parameters relating to the mass air flow past each injector, the ECU being operable to monitor the engine condition sensors, to model the dynamic air pressure and air mass flow at each injector depending upon the sensed conditions, to calculate the timing and period of the injection pulses for the respective injectors and to send control signals to said fuel injectors.

Description of the Drawings

The invention will be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a schematic drawing of an internal combustion engine, including an engine control unit, according to the present invention; Fig. 2 is a schematic drawing of an inlet port for a combustion chamber of the engine shown in Fig. 1; and Fig. 3 is a flow diagram showing the steps taken by the engine control unit shown in Fig. 1.

Detailed Description of the Invention

With reference to Fig.l and Fig 2, there is shown an internal combustion engine 11 of a vehicle, in particular a motor car, having a plurality of combustion chambers 22, in this example four combustion chambers, but may be any desired number of combustion chambers for example, six, eight or twelve arranged in any suitable configuration e.g. inline, or V formation. Each chamber 22 has an inlet port 23 for delivery of fuel to the combustion chamber 22 with at least one inlet valve 24 located in the inlet port to control the fuel supply into the combustion chamber 22. Fuel is supplied under pressure to a plurality of fuel injectors 12, in this example one per combustion chamber 22, via a fuel rail 13 in which the fuel pressure is controlled by a fuel pressure regulator 14. Each injector 12 extends into the respective inlet port 23 such that its injector tip 25 is located within the inlet port 23. s

Air is supplied to the combustion chambers via an inlet manifold 15 which ducts air to the inlet ports 23. Air flows through the inlet ports 23 past the fuel injector tips 25 and into the combustion chambers 22 during the induction portion of the engine cycle.

The operation of the engine 11 is controlled by a programmable electronic control unit (ECU) 16 which is connected to a plurality of vehicle operating condition sensors and engine condition sensors represented by sensors 17-19. The sensors 17-19 may include, but are not limited to, those which sense the following:- engine speed, engine position, engine torque load, manifold static pressure, mass air flow into the manifold, air temperature, engine temperature, camshaft position (inlet and exhaust), inlet manifold tuning valves, EGR amount, VCT position, torque demand, and gear position. The ECU is connected to the fuel injectors 12, either directly, as shown, or through a fuel injection control module, to control the operation thereof. The ECU 16 can determine the optimum end of injection time, the injection period or pulse width, and hence the start of the injection time for each cylinder.

The air flow past each injector 12 and into each cylinder is modelled and the engine ECU 16 is pre-programmed with information relating to the dynamic air pressure proximate to the tip of each injector, and parameters relating to the mass air flow past each injector. It may also be necessary to model the air velocity at each injector tip 25 and store this information on the ECU 16 if the design of the inlet manifold 15 causes marked cylinder to cylinder differences in performance.

With reference now Fig.3 the ECU controls the fuel injection to each combustion chamber through a series of operations shown as a flow chart.

The ECU 16, in step 1, first models the air flow in the inlet port of each combustion chamber 22 for engine steady state conditions based on sensed engine conditions and pre-programmed information in the form of algorithms and look-up tables which reference engine position, engine speed, inlet manifold static pressure, mass air flow into the manifold 15, engine S temperature, air temperature, camshaft position (inlet and exhaust), inlet manifold tuning valves, EGR amount, VCT position, etc..

In step 2, the ECU 16 then models the transient air flow behaviour to predict real time air flow and determines if a transient condition is occurring.

In step 3, the ECU 16 then calculates the optimum end of injection time based on pre programmed look-up tables and algorithms which reference engine speed, engine load, VCT position, engine temperature, etc. In step 4, the optimum end of injection time is then modified for each individual combustion chamber 22 based on the air flow behaviour for each cylinder as determined earlier in step 2.

The injector pulse width for each cylinder is calculated at step S based on look-up tables and algorithms which reference Fuel rail pressure, delta injection pressure and fuel required, and hence the start of injection time in step 6, which is based upon the calculated injection time and pulse width.

In step 7, the ECU 16 outputs control signals to the fuel injectors 12, or a control module therefor, for correct operation of the injector. The pulse width can be modified in step 7, if a transient condition is sensed as occurring in step 2.

Claims

Claims 1. A method of control of a motor vehicle internal combustion

engine having at least one air inlet manifold supplying air to the engine combustion chambers, fuel injectors supplying fuel to said chambers, and an electronic engine control unit (ECU) controlling the operation of the engine and being connected to a plurality of engine condition sensors, wherein the ECU is pre-programmed with parameters relating to the dynamic air pressure proximate to each injector and parameters relating to the mass air flow past each injector, monitors the engine condition sensors, ascertains the dynamic air pressure and air mass flow at each injector and, depending upon the sensed conditions, calculates the timing and period of the injection pulses for the respective injectors, and sends control signals to the fuel injectors.
2. A method as claimed in Claim 1, wherein the ECU ascertains the dynamic air pressure and - air mass flow at the tips of the respective injectors.
3. A method as claimed in Claim 1 or Claim 2 wherein the ECU is programmed to model the air flow in the inlet port of each combustion chamber for "steady engine state" conditions based on sensed engine conditions and pre-programmed information.
4. A method as claimed in any one of Claims 1 to 3, wherein the ECU models transient airflow behaviour to predict real time airflow based on sensed engine conditions and pre- programmed information.
S. A method as claimed in any one of Claims 1 to 4, wherein the timing and period for fuel injection is determined by calculating the optimum end of injection time for each cylinder based on pre-programmed information, and then calculating the pulse width for each cylinder based on pre-programmed information, and hence the start of the injection time for each cylinder.
6. A method as claimed in Claim 4 or Claim 5 when dependent on Claim 4, wherein the control signals to the fuel injectors may be adjusted in line with transient conditions.
7. A method of controlling a motor vehicle internal combustion engine substantially as described herein.
8. An internal combustion engine having at least one air inlet manifold supplying air to the engine combustion chambers, fuel injectors supplying fuel to said chambers and an electronic engine control unit (ECU) controlling the operation of the engine and being connected to a plurality of engine condition sensors, wherein the ECU is pre-programmed with parameters relating to the dynamic air pressure proximate to each injector and I S parameters relating to the mass air flow past each injector, the ECU being operable to monitor the engine condition sensors, to model the dynamic air pressure and air mass flow at each injector depending upon the sensed conditions, to calculate the timing and period of the injection pulses for the respective injectors and to send control signals to said fuel injectors.