Method for limiting the volumetric efficiency of a power engine during engine start-up in order to reduce emissions

Abstract

Procedure, comprehensive: Determine whether a power engine (102, 206) is started, based on at least one input received from an ignition system and a speed of the power engine; Generating a signal indicating whether the power engine (102, 206) is being started; and selectively adjusting a throttle valve (112) of the engine (102, 206) to a fully closed position when the signal indicates that the engine (102, 206) is being started; characterized by Determining the quantity of airflow entering a cylinder (118) of the engine (102, 206); and Control of a fuel injection device (125) based on the determined quantity of airflow to supply fuel to the cylinder (118) at a desired rate, which is determined based on the quantity of airflow entering the cylinder (118) and a target air / fuel ratio.

Description

AREA

[0001] The present disclosure relates to internal combustion engines and a method according to the preamble of claim 1 for limiting the volumetric efficiency of an engine during engine start-up in order to reduce emissions, as is known, for example, from DE 10 2008 042 514 A1. Further prior art is disclosed in DE 10 2009 023 413 B4. BACKGROUND

[0002] Internal combustion engines burn an air-fuel mixture in cylinders to drive pistons, producing drive torque. Airflow into the engine is regulated by a throttle valve. More precisely, the throttle valve sets the throttle range, which increases or decreases the airflow into the engine. As the throttle range increases, the airflow into the engine increases. A fuel control system sets the rate at which fuel is injected to provide a desired air / fuel mixture to the cylinders and / or achieve a desired torque output. Increasing the amount of air and fuel delivered to the cylinders increases the engine's torque output.

[0003] In spark-ignition engines, a spark ignites the combustion of an air / fuel mixture supplied to the cylinders. In compression-ignition engines, compression within the cylinders combusts the air / fuel mixture supplied to the cylinders. Ignition timing and airflow can be the primary mechanisms for adjusting the torque output of spark-ignition engines, while fuel flow can be the primary mechanism for adjusting the torque output of compression-ignition engines.

[0004] The invention is based on the objective of reducing the exhaust emissions of a power engine during a cold start. SUMMARY

[0005] This problem is solved by a method having the features of claim 1.

[0006] Further applications of the present disclosure will become clear from the detailed description provided below. It should be understood that the detailed description and specific examples are for illustrative purposes only. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present revelation is better understood with the help of the detailed description and accompanying drawings, in which: Fig. 1 a functional block diagram of a power machine system according to the principles of the present disclosure; Fig. 2 a perspective view of a throttle valve of the engine system of Fig. 1 is; Fig. 3 a functional block diagram of a control system in accordance with the principles of the present disclosure; and Fig. 4 is a flowchart of a method for limiting a volumetric efficiency of a power engine during the starting of the power engine according to the principles of the present disclosure.

[0008] Reference symbols can be reused in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0009] An exhaust system typically contains a catalytic converter that reduces emissions produced by an engine. A catalytic converter reduces emissions most effectively when it reaches operating temperature. When an engine is started after being switched off for a period of time, known as a cold start, the temperature of the catalytic converter is typically lower than its operating temperature. Therefore, the catalytic converter cannot reach operating temperature until the engine has been running for a while. During this period, the majority of emissions that pass through the exhaust system and into the environment can occur.

[0010] A method based on the principles of present experience limits the volumetric efficiency of an engine when the engine is started, in order to reduce the amount of air drawn into each cylinder of the engine. Volumetric efficiency is a ratio (or percentage) of the actual amount of air entering a cylinder during intake to the potential (or geometric) capacity of the cylinder under static conditions. The method can limit the volumetric efficiency of the engine by completely closing a throttle valve and / or limiting the opening duration of one or more intake valves.

[0011] Reducing the amount of air drawn into each cylinder of the engine reduces the amount of fuel that must be delivered to each cylinder to achieve a stoichiometric ratio. Reducing the amount of fuel delivered to each cylinder reduces the amount of emissions produced by the engine. Reducing the amount of emissions emitted by the engine reduces the amount of emissions that pass through the engine's exhaust system and into the environment, particularly when the amount of emissions leaving the engine is reduced during a cold start.

[0012] With reference to now Fig. Figure 1 shows an exemplary implementation of the power machine system 1, comprising a power machine 102 that burns an air / fuel mixture to generate drive torque for a vehicle based on driver input from a driver input module 104. The driver input can be based on the position of an accelerator pedal. The driver input can also be based on a vehicle speed control system, which can be an adaptive speed control system that varies the vehicle speed to maintain a predetermined following distance.

[0013] Air is drawn into the engine 102 via an intake system 108. The intake system 108 includes an intake manifold 110 and a throttle valve 112. For illustrative purposes only, the throttle valve 112 can be a valve flap with a rotatable flap. An engine control module (ECM) 114 controls a throttle actuator module 116, which regulates the opening of the throttle valve 112 to control the amount of air drawn into the intake manifold 110. The throttle actuator module 116 can actuate the throttle valve 112 between a fully open position (e.g., a position in which the throttle valve 112 is 100 percent open) and a fully closed position (e.g., a position in which the throttle valve 112 is 0 percent open).

[0014] Air from the intake manifold 110 is drawn into the cylinders of the engine 102. While the engine 102 can have multiple cylinders, a single representative cylinder 118 is shown for illustrative purposes. By way of example only, the engine 102 can have 2, 3, 4, 5, 6, 8, 10, and / or 12 cylinders. The ECM 114 can instruct a cylinder actuator module 120 to selectively shut down some of the cylinders, which can improve fuel economy under certain engine operating conditions.

[0015] The engine 102 can operate using a four-stroke cycle. The four strokes, described below, are designated as the intake stroke, the compression stroke, the combustion or power stroke, and the exhaust stroke. During each revolution of the crankshaft (not shown), two of the four strokes take place in cylinder 118. Therefore, two crankshaft revolutions are necessary for cylinder 118 to experience all four strokes.

[0016] During the intake stroke, air is drawn from the intake manifold 110 into cylinder 118 through an intake valve 122. The ECM 114 controls a fuel actuator module 124, which regulates a fuel injection device 125 to achieve a desired air / fuel ratio. Fuel can be injected into the intake manifold 110 at a central location or at multiple locations, such as near the intake valve 122 of each cylinder. The fuel injection device 125 can inject fuel directly into cylinder 118 (as shown) or into a mixing chamber associated with cylinder 118. The fuel actuator module 124 can stop fuel injection in cylinders that are shut down.

[0017] The injected fuel mixes with air, creating an air / fuel mixture in cylinder 118. During the compression stroke, a piston (not shown) in cylinder 118 compresses the air / fuel mixture. The engine 102 can be a compression-ignition engine, in which case the compression in cylinder 118 ignites the air / fuel mixture. Alternatively, the engine 102 can be a spark-ignition engine, in which case a spark actuator module 126 excites a spark plug 128 in cylinder 118 based on a signal from the ECM 114, which ignites the air / fuel mixture. The ignition timing of the spark plug can be set relative to the time when the piston is at its highest position, known as top dead center (TDC).

[0018] The ignition spark actuator module 126 can be controlled by an ignition timing signal, which determines how far before or after top dead center (TDC) the spark should be generated. Since the piston position is directly related to the crankshaft rotation, the operation of the ignition spark actuator module 126 can be synchronized with the crankshaft angle. In some implementations, the ignition spark actuator module 126 can stop the supply of sparks to deactivated cylinders.

[0019] The generation of the ignition spark can be referred to as an ignition event. The ignition spark actuator module 126 can vary the ignition timing of the spark for each ignition event. The ignition spark actuator module 126 can even vary the ignition timing for the next ignition event if the ignition timing signal is changed between the last ignition event and the next one. In various implementations, the engine 102 can have multiple cylinders, and the ignition spark actuator module 126 can vary the ignition timing relative to top dead center (TDC) for all cylinders in the engine 102 by the same amount.

[0020] During the combustion stroke, the combustion of the air / fuel mixture drives the piston downwards, thereby driving the crankshaft. The combustion stroke can be defined as the time between when the piston reaches top dead center (TDC) and when the piston returns to bottom dead center (BDC). During the exhaust stroke, the piston begins to move upwards from BDC, expelling the byproducts of combustion through an exhaust valve 130. The byproducts of combustion are then expelled from the vehicle via an exhaust system 134.

[0021] The intake valve 122 can be controlled by an intake camshaft 140, while the exhaust valve 130 can be controlled by an exhaust camshaft 142. In various implementations, multiple intake camshafts (including intake camshaft 140) can control multiple intake valves (including intake valve 122) for cylinder 118 and / or can control the intake valves (including intake valve 122) of multiple cylinder banks (including cylinder 118). Similarly, multiple exhaust camshafts (including exhaust camshaft 142) can control multiple exhaust valves for cylinder 118 and / or can control exhaust valves (including exhaust valve 130) for multiple cylinder banks (including cylinder 118).

[0022] The cylinder actuator module 120 can shut down cylinder 118 by disabling the opening of the intake valve 122 and / or the exhaust valve 130. In various other implementations, the intake valve 122 and / or the exhaust valve 130 can be controlled by devices other than camshafts, such as electromagnetic and / or hydraulic actuators.

[0023] The time at which the intake valve 122 is open relative to piston top dead center (TDC) can be varied by an intake cam phaser 148. The time at which the exhaust valve 130 is open relative to piston TDC can be varied by an exhaust cam phaser 150. A valve actuator module 158 can control the intake cam phaser 148 and the exhaust cam phaser 150 based on signals from the ECM 114. If implemented, variable valve lift actuators and / or other valve actuators can also be controlled by the valve actuator module 158.

[0024] The power engine system 100 can have a charging device that supplies pressurized air to the intake manifold 110. For example, shows Fig. 1. A turbocharger with a hot turbine 160-1, driven by hot exhaust gases flowing through the exhaust system 134. The turbocharger also includes a cold air compressor 160-2, driven by the turbine 160-1, which compresses air leading to the throttle valve 112. In some implementations, a mechanical supercharger (not shown), driven by the crankshaft, can compress air from the throttle valve 112 and supply the compressed air to the intake manifold 110.

[0025] A boost pressure control valve 162 can allow exhaust gas to bypass the turbine 160-1, thereby reducing the turbocharger's boost pressure (the amount of intake air compression). The ECM 114 can control the turbocharger via a boost actuator module 164. The boost actuator module 164 can modulate the turbocharger's boost pressure by controlling the position of the boost pressure control valve 162. In various implementations, multiple turbochargers can be controlled by the boost actuator module 164. The turbocharger can have a variable geometry that can be controlled by the boost actuator module 164.

[0026] An intercooler (not shown) can dissipate some of the heat contained in the compressed air charge, which is generated when the air is compressed. The compressed air charge may also contain absorbed heat from components of the exhaust system 134. Although shown separately for illustrative purposes, the turbine 160-1 and the compressor 160-2 can be attached to each other, bringing intake air into close proximity with hot exhaust gas.

[0027] The power unit system 100 can include an exhaust gas recirculation (EGR) valve 170, which selectively redirects exhaust gas back to the intake manifold 110. The EGR valve 170 can be positioned upstream of the turbine 160-1 of the turbocharger. The EGR valve 170 can be controlled by an EGR actuator module 172.

[0028] The ECM 114 can start and / or stop the engine 102 based on an input received from an ignition system 174. The ignition system 174 may include a key or a button. The ECM 114 can start the engine 102 when a driver turns the key from an off position to an on (or running) position, or when the driver presses the button. The ECM 114 can stop the engine 102 when a driver turns the key from the on position to the off position, or when the driver presses the button while the engine 102 is running.

[0029] The engine system 100 can measure the crankshaft position using a crankshaft position sensor 180 (CKP). The engine coolant temperature can be measured using an engine coolant temperature sensor 182 (ECT). The ECT sensor 182 can be located in the engine 102 or at other points where the coolant circulates, such as a radiator (not shown).

[0030] The pressure in the intake manifold 110 can be measured using a manifold absolute pressure (MAP) sensor 184. In various implementations, a vacuum in the engine, which is the difference between ambient air pressure and the pressure in the intake manifold 110, can also be measured. The mass flow rate of air flowing into the intake manifold 110 can be measured using a mass airflow (MAF) sensor 186. In various implementations, the MAF sensor 186 can be located in a housing that also contains the throttle valve 112.

[0031] The throttle actuator module 116 can monitor the position of the throttle valve 112 using one or more throttle position sensors (TPS). The TPS sensors 190 can provide the throttle valve position to the throttle actuator module 116, which can then provide the throttle valve position to the ECM 114. Alternatively, the TPS sensors 190 can provide the throttle valve position directly to the ECM 114. The ambient temperature of the air drawn into the power unit 102 can be measured using an intake air temperature sensor 192. The ECM 114 can use signals from the sensors to make control decisions for the power unit system 100.

[0032] Referring to Fig. Figure 2 shows an exemplary implementation of the throttle valve 112 comprising a cylindrical body 202, a rotatable flap 204, an electric motor 206, a stop 208, and a spring 210. The motor 206 rotates the flap 204 to adjust the throttle valve 112 between the fully open and fully closed positions. In the fully open position, the flap 204 can be arranged in a plane perpendicular to an opening surface 212 of the throttle valve 112, allowing airflow through the opening surface 212. In the fully closed position, the flap 204 can be arranged in a plane parallel to the opening surface 212 of the throttle valve 112, preventing airflow through the opening surface 212 and being fully seated against the body 202 and / or the stop 208.

[0033] Motor 206 rotates the throttle valve 204 in direction 214 from the fully open position to the fully closed position. The stop 208 can prevent motor 206 from rotating the throttle valve 204 past the fully closed position. Spring 210 can hold the throttle valve 112 at a predetermined opening percentage (e.g., from 7 to 10 percent open) when spring 210 is in a relaxed state (e.g., when the engine 102 is off and / or idling). Motor 206 can compress spring 210 when it rotates the throttle valve 204 to the fully closed position. In the example shown, spring 210 is positioned between the throttle valve 204 and stop 208, so that spring 210 is compressed between the throttle valve 204 and stop 208. In other examples, the spring 210 may be located in a different position in the throttle valve 112.

[0034] Referring to Fig. Figure 3 shows an exemplary implementation of the ECM 114 comprising an engine speed module 302, an engine starter module 304, a throttle control module 306, an intake air flow module 308, a fuel control module 310, and a valve control module 312. The engine speed module 302 determines the engine speed. The engine speed module 302 can determine the engine speed based on an input received from the CKP sensor 180. The engine speed module 302 can determine the engine speed based on the amount of crankshaft rotation between tooth detections and the corresponding period. The engine speed module 302 outputs the engine speed.

[0035] The engine starter module 304 detects whether the engine 102 is being started and generates a signal indicating this. The engine starter module 304 can detect that the engine 102 begins to start when the ignition system 174 is switched from off to on (or is running). The engine starter module 304 can detect that the engine 102 switches from starting to running when the engine speed is greater than or equal to a predetermined speed (e.g., from 400 revolutions per minute (rpm) to 700 rpm).

[0036] The throttle control module 306 sends instructions to the throttle actuator module 116 to adjust the position of the throttle valve 112. The throttle control module 306 can adjust the throttle valve 112 to a fully closed position when the engine 102 is started. The throttle control module 306 can only adjust the throttle valve 112 to the fully closed position during engine start-up if the engine coolant temperature, as measured by the ECT sensor 182, is below a predetermined temperature (e.g., 30 degrees Celsius (°C)).

[0037] The valve control module 312 sends instructions to the valve actuator module 158 to set the timing, lift, and / or opening duration of the intake valve 122 and / or the exhaust valve 130. The valve control module 312 can limit the opening duration of the intake valve 122 when the engine 102 is started. For example, the valve control module 312 can open the intake valve 122 for an initial duration while the engine 102 is running, and open the intake valve 122 for a second duration, shorter than the initial duration, when the engine 102 is started. The valve control module 312 can limit the opening duration of the intake valve 122 during engine start-up only if the engine coolant temperature is lower than the predetermined temperature. The valve control module 312 outputs the opening duration of the intake valve 122.

[0038] The intake air flow module 308 determines the amount of intake air entering each cylinder of the engine 102. The intake air flow module 308 can determine the intake air volume based on the manifold pressure from the MAP sensor 184, the throttle position from the TPS sensor 190, the target throttle position, and / or the opening duration of the intake valve 122. For example, the intake air flow module 308 can determine the amount of intake air flowing through the throttle valve 112 based on the throttle valve position and the engine vacuum. The intake air flow module 308 can then determine the amount of air flowing into each cylinder of the engine 102 based on the amount of intake air flowing through the throttle valve 112, the number of cylinders in the engine 102, and / or the opening duration of the intake valve 122.

[0039] The fuel control module 310 sends instructions to the fuel actuator module 124 to adjust the amount of fuel delivered to each of the cylinders of the engine 102. The fuel control module 310 can send instructions to the fuel actuator module 124 to deliver fuel to each cylinder at a desired rate. The fuel control module 310 can determine the target rate at which fuel is delivered to a cylinder based on the amount of air entering the cylinder. The fuel control module 310 can adjust the target rate to achieve a target air / fuel ratio, such as a stoichiometric air / fuel ratio.

[0040] Now, referring to Fig.4 begins a method for limiting the volumetric efficiency of a power engine during engine start-up at 402. At 404, the method determines whether the engine is being started. The method can determine that the engine begins starting when an ignition system of the engine is switched from off to on (or running). The method can determine that the engine transitions from starting to running when the engine speed is greater than or equal to a predetermined speed (e.g., from 400 rpm to 700 rpm). If the engine is being started, the method continues at 406. Otherwise, the method continues at 408.

[0041] In version 406, the procedure sets the throttle valve to a fully closed position (e.g., 0 percent open). In various implementations, in addition to or instead of setting the throttle valve to the fully closed position, the procedure can decrease the opening duration of an intake valve for one or more (e.g., all) cylinders of the engine when the engine is started. For example, the procedure can open the intake valve for an initial duration while the engine is running and open the intake valve for a second duration, which is shorter than the initial duration, when the engine is started.

[0042] In 408, the method holds a throttle valve of the engine at a predetermined position (e.g., from 7 to 10 percent open). In one example, the throttle valve has a rotatable flap, an electric motor, and a spring. The motor can adjust the flap between the predetermined position and a fully open position (e.g., 100 percent open) when the engine 102 is running. The spring can maintain the flap in the predetermined position when the spring is in a relaxed state (e.g., when the engine is off and / or when the engine is idling).

[0043] At 410, the method determines the amount of intake air entering each cylinder of the engine. The method can determine the intake air volume based on the pressure in an intake manifold, the position of a throttle valve, and / or the opening duration of the intake valve. For example, the method can determine the amount of intake air flowing through the throttle valve based on the throttle valve position and the engine vacuum. The method can then determine the amount of air flowing into each cylinder of the engine based on the amount of intake air flowing through the throttle, the number of cylinders in the engine, and / or the opening duration of the intake valve.

[0044] In the 412, the method sets the amount of fuel delivered to each cylinder in the engine based on the amount of intake air entering each cylinder. The method can deliver fuel to each cylinder at a desired rate. The method can determine the desired rate at which fuel is delivered to a cylinder based on the amount of air entering the cylinder. The method can adjust the desired rate to achieve a desired air / fuel ratio, such as a stoichiometric air / fuel ratio.

[0045] At 414, the procedure determines whether the engine speed is greater than the predetermined speed. If the engine speed is greater than the predetermined speed, the procedure determines that the engine is running and proceeds to 416. Otherwise, the procedure proceeds to 406. At 416, the procedure adjusts the throttle valve based on a driver input (e.g., an accelerator pedal position, a cruise control setting). For example, the procedure can determine a driver torque request based on the driver input and adjust the throttle valve to a position that meets the driver torque request when fuel is delivered to each cylinder of the engine at a rate that achieves the desired air / fuel ratio.

[0046] The broad teachings of revelation can be implemented in a variety of forms. In its use herein, the phrase "at least one of A, B, and C" should be interpreted as meaning a logical (A or B or C) using a non-exclusive logical "or". It should be understood that one or more steps in a procedure may be performed in a different order (or simultaneously) without altering the principles of the present revelation.

[0047] In this application, including the definitions below, the term "module" may be substituted for the term "circuit". The term "module" as used herein may include an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field-programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; memory (shared, dedicated, or group) that stores code executed by a processor; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, as in a system-on-a-chip, affecting, part of, or comprising it.

[0048] The term "code," as used above, can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, and / or objects. The term "shared processor" includes a single processor that executes some or all of the code from multiple modules. The term "group processor" includes a processor that, in combination with additional processors, executes some or all of the code from one or more modules. The term "shared memory" includes a single memory that stores some or all of the code from multiple modules. The term "group memory" includes memory that, in combination with other memories, stores some or all of the code from one or more modules. The term "memory" can be a subset of the term "computer-readable medium."The term "computer-readable medium" does not include volatile electrical and electromagnetic signals that propagate through a medium and can therefore be considered concrete and non-volatile. Non-restrictive examples of non-volatile concrete computer-readable media include non-volatile storage, volatile storage, magnetic storage, and optical storage.

[0049] The method described in this application can be implemented partially or completely by one or more computer programs executed by one or more processors. The computer programs contain instructions executable by a processor, stored on at least one non-volatile, tangible, computer-readable medium. The computer programs may also contain and / or rely on stored data.

Claims

[1] Procedure, encompassing: Determine whether a power engine (102, 206) is started, based on at least one input received from an ignition system and a speed of the power engine; Generating a signal indicating whether the power engine (102, 206) is being started; and selectively adjusting a throttle valve (112) of the engine (102, 206) to a fully closed position when the signal indicates that the engine (102, 206) is being started; characterized by Determining the quantity of airflow entering a cylinder (118) of the engine (102, 206); and Control of a fuel injection device (125) based on the determined quantity of airflow to supply fuel to the cylinder (118) at a desired rate, which is determined based on the quantity of airflow entering the cylinder (118) and a target air / fuel ratio. [2] Method according to claim 1, further comprising: Opening an intake valve (122) for a first duration when the engine (102, 206) is started; and Opening the intake valve (122) for a second duration when the engine (102, 206) is running, the first duration being shorter than the second duration. [3] Method according to claim 1, further comprising adjusting the throttle valve (112) to the fully closed position while the engine (102, 206) is being started when an engine coolant temperature is less than a predetermined temperature. [4] Method according to claim 1, further comprising determining that the engine (102, 206) begins to start when the ignition system is switched from off to on. [5] Method according to claim 1, further comprising determining that the power machine (102, 206) is running when the speed of the power machine is greater than a predetermined speed. [6] Method according to claim 1, further comprising determining the engine speed based on a crankshaft position. [7] Method according to claim 1, wherein the amount of airflow entering a cylinder (118) of the engine (102, 206) is determined on the basis of an air pressure in an intake manifold (119) of the engine (102, 206). [8] Method according to claim 1, further comprising direct injection of fuel into the cylinder (118).

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