Start control device

Abstract

To provide a start control device capable of securing excellent startability even when ethanol concentration in fuel is high and an outside air temperature and an intake air temperature of an internal combustion engine are low.SOLUTION: A start control device (30) applied to an internal combustion engine (E) driven by combustion of fuel containing ethanol includes: ethanol concentration determination means (31) for determining ethanol concentration in the fuel; and ignition timing change means (33) for changing ignition timing when starting the internal combustion engine (E) according to the ethanol concentration, wherein if the ethanol concentration determination means (31) determines that the ethanol concentration exceeds a threshold value when starting the internal combustion engine (E), the ignition timing change means (33) applies ignition timing that is more advanced than ignition timing applied after the internal combustion engine (E) is started, until the internal combustion engine (E) is started.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a starting control device, and more particularly to a starting control device that is applied to an internal combustion engine that is driven by burning fuel containing ethanol. [Background technology]

[0002] Conventionally, in a start control device for an internal combustion engine, a configuration is known in which, when cranking the crankshaft to start the internal combustion engine, an ignition timing different from the ignition timing applied after start-up is applied in order to improve startability.

[0003] Patent Document 1 discloses a start control device that advances ignition timing in accordance with the temperature of the cooling water of an internal combustion engine when the internal combustion engine is started. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-214125 Summary of the Invention [Problem to be solved by the invention]

[0005] It is known that internal combustion engines that are powered by burning fuel containing ethanol suffer from poor startability when the ethanol concentration in the fuel exceeds a predetermined threshold and when the outside air temperature and the intake air temperature of the internal combustion engine are low. However, Patent Document 1 does not consider a start control device that is suitable for internal combustion engines that are powered by burning fuel containing ethanol.

[0006] The object of the present invention is to solve the problems of the conventional technology described above and to provide a starting control device that can ensure good starting performance even when the ethanol concentration in the fuel is high and the outside air temperature and the intake air temperature of the internal combustion engine are low. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a start control device (30) applied to an internal combustion engine (E) that is driven by burning fuel containing ethanol, the start control device (30) comprising: an ethanol concentration determination means (31) that determines the ethanol concentration in the fuel; and an ignition timing change means (33) that changes the ignition timing when starting the internal combustion engine (E) in accordance with the ethanol concentration. A first feature of the ignition timing change means (33) is that, when starting the internal combustion engine (E), if the ethanol concentration determination means (31) determines that the ethanol concentration exceeds a threshold value, the ignition timing change means (33) applies an ignition timing that is more advanced than the ignition timing applied after the start of the internal combustion engine (E) until the internal combustion engine (E) starts.

[0008] A second feature of the present invention is that it includes an intake air temperature sensor (10) that detects the intake air temperature, and the ignition timing change means (33) does not advance the ignition timing when the intake air temperature exceeds the threshold value, even if the ethanol concentration determination means (31) determines that the ethanol concentration exceeds the threshold value when starting the internal combustion engine (E).

[0009] A third feature of the ignition timing change means (33) is that when starting the internal combustion engine (E), the ignition timing change means (33) advances the ignition timing of the 360° ignition, which is performed every 360° rotation of the crankshaft (3) of the internal combustion engine (E), and when stroke determination of the internal combustion engine (E) is completed, the ignition timing change means (33) advances the first ignition timing of the 360° ignition, which is closer to the fuel injection timing (F), which is performed every 720° rotation of the crankshaft (3) of the internal combustion engine (E), from the ignition timing applied after the start of the internal combustion engine (E), and sets the ignition timing of the 360° ignition, which is farther from the fuel injection timing (F), to a second ignition timing that is retarded from the first ignition timing.

[0010] Furthermore, a fourth feature is that the advance amount of the ignition timing is within 35° from the compression top dead center of the internal combustion engine (E). [Effects of the Invention]

[0011] According to a first feature, a start control device (30) applied to an internal combustion engine (E) that is driven by burning fuel containing ethanol includes an ethanol concentration determination means (31) that determines the ethanol concentration in the fuel, and an ignition timing change means (33) that changes the ignition timing when starting the internal combustion engine (E) in accordance with the ethanol concentration. When starting the internal combustion engine (E), if the ethanol concentration determination means (31) determines that the ethanol concentration exceeds a threshold value, the ignition timing change means (33) applies an ignition timing that is more advanced than the ignition timing that will be applied after the start of the internal combustion engine (E) until the internal combustion engine (E) starts. Therefore, when the ethanol concentration in the fuel is high and it is expected that the startability of the internal combustion engine will decrease, the startability can be improved by applying an ignition timing that is more advanced than the ignition timing that will be applied after the start of the internal combustion engine. In a reciprocating engine that repeats intake, compression, explosion, and exhaust strokes, with normal ignition timing applied after startup, the piston begins to move down and the temperature inside the cylinder starts to drop before the combustion caused by the initial explosion at startup has fully spread. However, by performing ignition with advanced ignition timing, the combustion caused by the initial explosion can be fully spread before the temperature inside the cylinder begins to drop.

[0012] According to a second feature, an intake air temperature sensor (10) that detects an intake air temperature is provided, and when starting the internal combustion engine (E), even if the ethanol concentration determination means (31) determines that the ethanol concentration exceeds a threshold value, the ignition timing change means (33) does not advance the ignition timing if the intake air temperature exceeds the threshold value. Therefore, even if the ethanol concentration in the fuel is high, if sufficient startability can be expected because the intake air temperature is high, by not advancing the ignition timing, it becomes possible to perform appropriate ignition according to the state of the fuel.

[0013] According to a third feature, the ignition timing change means (33) advances the ignition timing of the 360° ignition, which is performed every time the crankshaft (3) of the internal combustion engine (E) rotates 360°, when starting the internal combustion engine (E), and, after stroke determination of the internal combustion engine (E) is completed, advances the first ignition timing of the 360° ignition, which is closer to the fuel injection timing (F) which is performed every 720° of the crankshaft (3) of the internal combustion engine (E), from the ignition timing applied after the start of the internal combustion engine (E). At the same time, the ignition timing of the 360° ignition on the side farther from the fuel injection timing (F) is set to a second ignition timing that is retarded from the first ignition timing, so that once stroke determination is completed, the 360° ignition on the side closer to the fuel injection timing is executed at the first ignition timing, and the 360° ignition on the side farther from the fuel injection timing is executed at the second ignition timing that is closer than the first ignition timing, thereby making it possible to narrow the interval from the arrival of the second ignition timing to the arrival of the first ignition timing. This promotes an increase in the in-cylinder temperature and improves startability.

[0014] According to the fourth feature, the advance amount of the ignition timing is within 35° from the compression top dead center of the internal combustion engine (E). Therefore, the advance amount is large, and it is possible to suppress the input of a force in the reverse rotation direction to the crankshaft due to the explosion pressure during the explosion stroke. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram showing a starting control device and its peripheral configuration according to an embodiment of the present invention; [Figure 2] 3 is a timing chart showing the combustion cycle and ignition timing of the engine. [Figure 3] 3 is a flowchart showing the procedure of a startability improvement control 1 according to the present embodiment. [Figure 4] 4 is a flowchart showing the procedure of startability improvement control 2 according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] A preferred embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory diagram showing a starting control device 30 and its peripheral configuration according to one embodiment of the present invention. The starting control device 30 is configured to improve the startability of an engine E that runs on a fuel mixture of gasoline and ethanol. A cylinder head 8 housing an intake valve (IN) and an exhaust valve (EX) is attached to the top of a cylinder 7 of the engine E, which is a four-stroke, single-cylinder internal combustion engine. A crank pulse rotor 4 that rotates synchronously with the crankshaft 3 is attached to the crankshaft 3. The crank pulse rotor 4 has a total of 15 reluctors 5 arranged at 20-degree intervals, excluding one toothless portion H. A magnetic pickup-type pulse generator 1 outputs a pulse signal to the starting control device 30, which serves as a control unit, each time it detects the passage of a reluctor 5.

[0017] An air cleaner box 9 that filters the intake air is attached to one end of an intake pipe 19. An intake air temperature sensor 10 and an atmospheric pressure sensor 11 are provided in the air cleaner box 9. An air flow sensor 12 that measures the amount of intake air, a butterfly-type throttle valve 13 driven by an actuator 14, a throttle valve opening sensor 16 that detects the rotation angle of the throttle valve 13, and a PB (intake pressure) sensor 17 that detects the intake pressure are attached to the intake pipe 19. An ignition device 20 is provided above the combustion chamber, and a fuel injection valve 18 is disposed in the intake pipe 19 downstream of the throttle valve 13. An oxygen sensor 21 is attached to an exhaust pipe 22.

[0018] The start control device 30 receives output signals from an oxygen sensor 21 that detects the oxygen concentration in the exhaust gas of the engine E and a starter switch 25 that starts the engine E. After the ignition switch is operated to turn on the vehicle power, the starter switch 25 is operated, and the starter motor 26 starts cranking the crankshaft 3.

[0019] The start control device 30 includes an ethanol concentration determination means 31 that estimates the ethanol concentration of the fuel in four stages from the oxygen concentration of the exhaust gas based on the output signal of the oxygen sensor 23, a stroke discrimination means 32 that determines whether the stroke of the combustion cycle is on the front or back when the engine E is started, an ignition timing change means 33 that changes the ignition timing in accordance with various conditions, an ignition device control means 34 that controls the drive of the ignition device 20 at a predetermined ignition timing, and a fuel injection device control means 35 that controls the drive of the fuel injection valve 18 at a predetermined injection timing.

[0020] The start control device 30 of this embodiment is configured to improve startability by changing the ignition timing to a timing different from normal when it is determined that startability has decreased because the ethanol concentration of the fuel is higher than a predetermined value and the intake air temperature is lower than a predetermined value when starting the engine E.

[0021] In addition, in addition to the above-mentioned ignition timing change control, the start control device 30 operates the fuel heating means 18a, which warms the fuel supplied to the fuel injection valve 18, thereby further improving the startability of the engine E.

[0022] FIG. 2 is a timing chart showing the combustion cycle and ignition timing of engine E. The combustion cycle of engine E consists of four strokes: compression, combustion, exhaust, and intake. Each stroke is determined based on the crank pulse output from pulse generator 1. Specifically, when the crank pulse detects missing tooth portion H of reluctor 5, the position from which a predetermined number of crank pulses are detected is determined as the reference position of crank pulse rotor 4, and one rotation of crankshaft 3 is divided into 16 crank stages according to the arrangement of reluctor 5. Then, based on the fluctuation state of the intake air pressure detected by the PB sensor between stages 15 and 1, a front / back determination is made to determine whether the crankshaft 3 is in the first or second rotation of one cycle (720 degrees). One cycle is divided into 32 stages, completing the stroke determination.

[0023] The engine E according to this embodiment is configured to perform ignition between stages 1 to 5 after stroke determination is complete. Here, since stroke determination is not complete when the engine E is started, the ignition device 20 is configured to perform ignition twice in one cycle between stages 1 to 5, i.e., "ignition every 360°," in order to increase the chance of initial combustion and improve startability. In contrast, in a conventional start control device, if stroke determination is completed between the start of cranking and the start of the engine E, the engine is configured to switch from "ignition every 360°" to "ignition every 720°," which may result in insufficient improvement in startability due to ignition every 360°.

[0024] The start control device 30 according to this embodiment is characterized in that when starting the engine E, if it is determined that the ethanol concentration of the fuel is higher than a predetermined value and the intake air temperature is lower than a predetermined value, thereby reducing the startability, it continues ignition every 360° even if stroke determination is completed during cranking.

[0025] 3 is a flowchart showing the procedure of the startability improvement control 1 according to this embodiment. In step S1, the engine E is in a stopped state. In step S2, it is determined whether the ignition switch is turned on, and if the determination is affirmative, the process proceeds to step S3. In step S3, it is determined whether the starter switch 25 is turned on, and if the determination is affirmative, the process proceeds to step S4. If the determinations in steps S1 and S2 are negative, the process returns to the determinations in steps S1 and S2, respectively.

[0026] In step S4, it is determined whether the ethanol concentration exceeds a threshold value (for example, 90%), and if the determination is affirmative, the process proceeds to step S5. In step S5, it is determined whether the intake air temperature is equal to or lower than a threshold value (for example, 5°C), and if the determination is affirmative, it is determined that the startability of the engine E is in a deteriorated state, and the process proceeds to step S6.

[0027] In step S6, it is determined whether the crankshaft 3 is cranking, in other words, whether the rotation speed of the crankshaft 3 is equal to or lower than a predetermined value (for example, 1000 rpm) that is lower than the idling rotation speed, and if the determination is affirmative, the process proceeds to step S7, where ignition every 360° is continued. On the other hand, if the determination is negative in step S6, that is, if it is determined that the engine E has started, the process proceeds to step S10, where ignition every 360° is switched to ignition every 720°.

[0028] Then, in step S8, it is determined whether or not the engine E has started, and if the determination is affirmative, the process proceeds to step S9, where switching to normal ignition every 720° is performed, and the series of controls is terminated. If the determination is negative in step S8, the process returns to the determination in step S8.

[0029] On the other hand, if a negative determination is made in step S4 or step S5, it is determined that the conditions under which the startability of the engine E is reduced are not met, and the process proceeds to step S11, where it is determined whether the stroke determination is incomplete. If a positive determination is made in step S11, the process proceeds to step S12, where ignition every 360° is continued. If a negative determination is made in step S11, the process proceeds to step S13, where ignition every 360° is switched to ignition every 720°.

[0030] As described above, the start control device 30 according to this embodiment is equipped with an ethanol concentration determination means 31 that determines the ethanol concentration in the fuel, and an ignition timing change means 33 that changes the ignition timing when starting the engine E depending on the ethanol concentration. If the ethanol concentration is determined to exceed a threshold value when starting the engine E, the ignition timing change means 33 continues ignition every 360° until the engine E starts. Therefore, when the ethanol concentration in the fuel is high and it is expected that the startability of the engine E will decrease, it is possible to improve the startability by continuing ignition every 360°.

[0031] Furthermore, when starting engine E, if the intake temperature exceeds the threshold value even if it is determined that the ethanol concentration exceeds the threshold value, the ignition timing change means 33 switches from ignition every 360° to ignition every 720° after stroke determination of engine E is completed. Therefore, even if the ethanol concentration in the fuel is high, if sufficient startability can be expected due to the high intake temperature, by switching from ignition every 360° to ignition every 720°, it is possible to reduce the load on the ignition device 20 and suppress power consumption.

[0032] Referring to FIG. 2, the start control device 30 according to this embodiment is configured to use the ignition timing change means 33 to apply ignition timing B, which is more advanced than ignition timing A applied after engine E is started, when executing 360° ignition before starting the engine E. In a reciprocating engine that repeats an intake stroke, compression stroke, power stroke, and exhaust stroke, normal ignition timing A applied after starting causes the piston to start moving down and the in-cylinder temperature to drop before the initial combustion at start-up has fully spread. However, by executing ignition at ignition timing B, which is advanced from the 360° ignition, it is possible to fully spread the initial combustion before the in-cylinder temperature begins to drop. This improves the startability of the engine E. The ignition timing applied in the 360° ignition can be, for example, 27° BTDC.

[0033] Furthermore, when executing ignition every 720° before starting the engine E, the start control device 30 is configured to use the ignition timing change means 33 to apply ignition timing B that is advanced from ignition timing A that is applied after starting the engine E, and on the other hand, when executing ignition every 360°, to apply ignition timing D that is retarded from ignition timing C for ignition every 720°. In this way, by bringing the ignition timing for ignition every 360° closer to the ignition timing for ignition every 720°, it is possible to promote an increase in the in-cylinder temperature and improve startability.

[0034] 4 is a flowchart showing the procedure of the startability improvement control 2 according to this embodiment. In step S20, the engine E is in a stopped state. In step S21, it is determined whether the ignition switch has been turned on, and if a positive determination is made, the process proceeds to step S22. In step S22, it is determined whether the starter switch 25 has been turned on, and if a positive determination is made, the process proceeds to step S23. If a negative determination is made in steps S21 and S22, the process returns to the determination in steps S21 and S22, respectively.

[0035] In step S23, it is determined whether the ethanol concentration exceeds a threshold value (for example, 90%), and if the determination is affirmative, the process proceeds to step S24. In step S24, it is determined whether the intake air temperature is equal to or lower than a threshold value (for example, 5°C), and if the determination is affirmative, it is determined that the startability of the engine E is in a deteriorated state, and the process proceeds to step S25.

[0036] In step S25, ignition is performed every 360° by advancing the ignition timing from the fixed ignition. In the following step S26, it is determined whether or not engine E has started, and if a positive determination is made, the process proceeds to step S27. Then, in step S27, ignition is switched to normal ignition, which applies the optimal ignition timing depending on the rotation speed of engine E, etc., and the series of controls ends. On the other hand, if a negative determination is made in step S23 or step S24, it is determined that the startability of engine E is not impaired, and the process proceeds to step S28, where fixed ignition is performed, and once engine E has started, ignition is switched to normal ignition. If a negative determination is made in step S27, the process returns to the determination in step S27.

[0037] As described above, according to the start control device 30 of this embodiment, if the ignition timing change means 33 determines that the ethanol concentration exceeds a threshold when starting the engine E, it applies ignition timing that is more advanced than the ignition timing that will be applied after the start of the engine E until the engine E starts. Therefore, when the ethanol concentration in the fuel is high and it is expected that the startability of the engine E will be reduced, it is possible to improve the startability by applying ignition timing that is more advanced than the ignition timing that will be applied after the start of the engine E. In a reciprocating engine that repeats an intake stroke, compression stroke, power stroke, and exhaust stroke, with normal ignition timing that is applied after start, the piston begins to move down and the in-cylinder temperature begins to drop before the combustion caused by the initial combustion at start-up has fully spread. However, by executing ignition with advanced ignition timing, it is possible to fully spread the combustion caused by the initial combustion before the in-cylinder temperature begins to drop.

[0038] Furthermore, even if the ignition timing change means 33 determines that the ethanol concentration exceeds a threshold when starting the engine E, if the intake air temperature exceeds the threshold, the ignition timing is not advanced. Therefore, even if the ethanol concentration in the fuel is high, if sufficient startability can be expected due to the high intake air temperature, the ignition timing is not advanced, thereby making it possible to reduce the load on the ignition device.

[0039] Furthermore, the ignition timing change means 33 advances the ignition timing of the 360° ignitions when starting the engine E. After stroke determination of the engine E is completed, the ignition timing change means 33 advances the first ignition timing of the 360° ignitions closer to the fuel injection timing F, which occurs every 720° of rotation of the crankshaft 3, from the ignition timing applied after starting the engine E, and sets the ignition timing of the 360° ignitions further from the fuel injection timing F to a second ignition timing that is retarded from the first ignition timing. This shortens the interval between the arrival of the second ignition timing and the arrival of the first ignition timing. This promotes an increase in in-cylinder temperature and improves startability. The amount of advance of the ignition timing is set to within 35° of the compression top dead center (BTDC) of the engine E. This large advance amount can suppress a force applied to the crankshaft 3 in the reverse rotation direction due to the explosion pressure during the explosion stroke.

[0040] The number and configuration of the engine cylinders, the threshold values ​​for the ethanol concentration and intake air temperature, the degree by which the ignition timing is advanced or retarded, and the like are not limited to those described in the above embodiment and can be modified in various ways. For example, the determination based on the intake air temperature may be replaced with a determination based on the outside air temperature. The ethanol concentration of the fuel may also be determined by an ethanol concentration sensor. The start control device according to the present invention can be applied to internal combustion engines as drive sources for various vehicles, such as motorcycles, three-wheeled vehicles, and four-wheeled vehicles. [Explanation of symbols]

[0041] E... engine (internal combustion engine), 3... crankshaft, 18a... fuel heating means, 30... start control device, 31... ethanol concentration determination means, 33... ignition timing change means, 10... intake air temperature sensor, A... ignition timing applied after engine start, B... ignition timing applied every 360°, F... fuel injection timing

Claims

1. A start control device (30) applied to an internal combustion engine (E) that is driven by burning fuel containing ethanol, an ethanol concentration determination means (31) for determining the ethanol concentration in the fuel; an ignition timing change means (33) for changing the ignition timing when starting the internal combustion engine (E) in accordance with the ethanol concentration, When the ethanol concentration determination means (31) determines that the ethanol concentration exceeds a threshold value when starting the internal combustion engine (E), the ignition timing change means (33) applies an ignition timing that is more advanced than the ignition timing that is applied after the start of the internal combustion engine (E) until the internal combustion engine (E) starts, The ignition timing change means (33) When starting the internal combustion engine (E), the ignition timing of ignition every 360°, in which ignition is performed every 360° of the crankshaft (3) of the internal combustion engine (E), is advanced; When stroke determination of the internal combustion engine (E) is completed, a first ignition timing of the ignition every 360° that is closer to a fuel injection timing (F) that is performed every 720° rotation of a crankshaft (3) of the internal combustion engine (E) is advanced from an ignition timing that is applied after starting of the internal combustion engine (E), and an ignition timing of the ignition every 360° that is farther from the fuel injection timing (F) is set to a second ignition timing that is retarded from the first ignition timing.

2. An intake air temperature sensor (10) is provided for detecting an intake air temperature, 2. The start control device according to claim 1, wherein, when starting the internal combustion engine, even if the ethanol concentration determination means determines that the ethanol concentration exceeds a threshold value, if the intake air temperature exceeds a threshold value, the ignition timing change means does not advance the ignition timing.

3. 3. A start control device according to claim 1, wherein the amount of advance of the ignition timing is within 35 degrees from the compression top dead center of the internal combustion engine (E).

Images