Method for controlling the operation of a two-stroke spark ignition internal combustion engine

• US 10,641,195 B2
• Filed: 07/20/2017
• Issued: 05/05/2020
• Est. Priority Date: 08/01/2016
• Status: Active Grant

• Current Assignee: EMAK SPA (YAMA SPA)
• Original Assignee: EMAK SPA (YAMA SPA)
• Inventors: Barbolini, Gianluca, Gagliardi, Vincenzo, Grisendi, Alessandro
• Primary Examiner(s): Solis, Erick R
• Application Number:
  US16/321,874
• Publication Number:
  US 20190178185A1
• Time in Patent Office: 1,020 Days
• Field of Search: 123198 DC, 123329, 123334, 123335, 701104
• CPC Class Codes: F02B 2075/025 two
• CPC Class Codes: F02D 2009/0208 for small engines
• CPC Class Codes: F02D 2009/0238 Increasing ignition delay
• CPC Class Codes: F02D 2700/09 Other ways of controlling
• CPC Class Codes: F02D 35/021 using an ionic current sensor
• CPC Class Codes: F02D 41/123 the fuel injection being cut-off
• CPC Class Codes: F02P 11/025 Shortening the ignition when the engine is stopped to prevent damage to the coil F02P3/0556
• CPC Class Codes: F02P 2017/125 Measuring ionisation of combustion gas, e.g. by using ignition circuits
• CPC Class Codes: F02P 5/1504 with particular means during a transient phase, e.g. acceleration, deceleration, gear change during starting F02P5/1506
• CPC Class Codes: F02P 5/1506 with particular means during starting
• CPC Class Codes: F02P 5/1508 with particular means during idling
• CPC Class Codes: F02P 9/005 by weakening or suppression of sparks to limit the engine speed
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for controlling the operation of a spark ignition internal combustion engine is described. The engine includes: a combustion chamber, an intake duct for placing the combustion chamber in communication with the external, a throttle valve arranged inside the intake duct, a carburetor for introducing fuel into the intake duct to form an air/fuel mixture to be intaken into the combustion chamber, and a spark plug arranged inside the combustion chamber to generate a spark for igniting the combustion of the air/fuel mixture. The method includes: monitoring the opening degree of the throttle valve; monitoring the speed of the engine, preventing the spark plug from generating the spark, if the opening degree of the throttle valve drops below a first opening degree threshold value and the speed of the engine is greater than a first engine speed threshold value.

Claims

1. A method for controlling the operation of a spark ignition internal combustion engine (100), wherein the engine (100) comprises:

a combustion chamber (115),

an intake duct (155) configured to place the combustion chamber (115) in communication with the external,

a throttle valve (165) arranged in the intake duct (155),

a carburetor (170) configured to introduce fuel into the intake duct (155) to form an air and fuel mixture intended to be intaken into the combustion chamber (115), and

a spark plug (235) arranged inside the combustion chamber (115) to generate a spark for ignition of the combustion of the air and fuel mixture,

the method comprises the steps of;

monitoring the opening degree (G) of the throttle valve (165),

monitoring the speed (V) of the engine (100),

preventing the spark plug (235) from generating the spark, if the opening degree (G) of the throttle valve (165) drops below a first opening degree threshold value (GM) and the speed (V) of the engine (100) is greater than a first engine speed threshold value (VF);

adjusting the instant when the spark plug (235) triggers the spark depending on the opening degree (G) of the throttle valve (165) and the speed (V) of the engine (100), if the opening degree (G) of the throttle valve (165) is comprised between a second and a third opening degree threshold value (GA, GC), wherein said second threshold value (GA) is below said third opening degree threshold value (GC).

2. The method according to claim 1, further comprising the step of maintaining the speed (V) of the engine (100) at a pre-set target value, if the speed (V) of the engine (100) drops below the first engine speed threshold value (VF).

3. The method according to claim 2, wherein the speed (V) of the engine (100) is maintained at the pre-set target value by adjusting the ratio between air and fuel in the mixture formed by the carburetor (170).

4. The method according to claim 3, wherein the ratio between air and fuel in the mixture is adjusted by a control system configured to minimize a difference between the speed (V) of the engine (100) and the pre-set target value.

5. The method according to claim 1, wherein the instant when the spark plug (235) generates the spark may be provided in output from a calibration map which receives the speed (V) of the engine (100) and the opening (G) of the throttle valve (165) in input.

6. The method according to claim 1, further comprising the steps of monitoring the ionization current in the combustion chamber (115) and using the ionization current to adjust the ratio between air and fuel in the mixture formed by the carburetor (170), if the opening degree (G) of the throttle valve (165) exceeds said third opening degree threshold value (GC).

7. The method according to claim 6, wherein the adjustment of the ratio between air and fuel comprises:

running the engine (100) with an air/fuel ratio equivalent to a predetermined initial value;

creating, for the initial air/fuel ratio value, a first curve representing the ionization current depending on the angular position of an engine crankshaft (125);

calculating a value equivalent to the integral of the first curve in a pre-set angular interval of the crankshaft (125);

modifying the engine air/fuel ratio bringing it to a second value different from the initial value;

for the second air/fuel ratio value, creating a second curve representing the ionization current depending on the angular position of the crankshaft (125);

calculating a value equivalent to the integral of the second curve in an angular interval of the crankshaft (125) equal to the previous one;

calculating a difference between the value of the integral of the second curve and the value of the integral of the first curve;

acting on the carburation by varying the initial value of the air/fuel ratio if the difference reveals an absolute value greater than a pre-set threshold value.

8. The method according to claim 1, further comprising the steps of reducing the engine speed, if the engine speed (V) exceeds a second engine speed threshold value (VH) that is greater than the first engine speed threshold value (VF).

9. A spark ignition internal combustion engine (100) comprising:

a combustion chamber (115),

an intake duct (155) configured to place the combustion chamber (115) in communication with the external,

a throttle valve (165) arranged in the intake duct (155),

a carburetor (170) configured to introduce fuel into the intake duct (155) to form an air and fuel mixture intended to be intaken into the combustion chamber (115),

a spark plug (235) arranged inside the combustion chamber (115) to generate a spark suitable to ignite the combustion of the air and fuel mixture, and

an electronic unit (240) configured to monitor the opening degree (G) of the throttle valve (165), monitor the speed (V) of the engine (100) and prevent the spark plug (235) from generating the spark, if the opening degree (G) of the throttle valve (165) drops below a first opening degree threshold value (GM) and the speed (V) of the engine (100) is greater than a first engine speed threshold value (VF) and adjust the instant when the spark plug (235) triggers the spark depending on the opening degree (G) of the throttle valve (165) and the speed (V) of the engine (100), if the opening degree (G) of the throttle valve (165) is comprised between a second and a third opening degree threshold value (GA, GC), wherein said second threshold value (GA) is below said third opening degree threshold value (GC).