Engine, control device and method thereof

Abstract

To suppress variation in air-fuel mixture concentration in a combustion chamber at the time of starting an engine.SOLUTION: An engine includes: an engine body that has a cylinder, a piston reciprocating in the cylinder, a crank shaft rotating by interlocking with the reciprocating of the piston, and a valve train that performs intake action into the cylinder and exhaust action by interlocking with the reciprocating of the piston; a fuel injection valve that injects a fuel; an ignition device that ignites the fuel in the cylinder; and a control device for controlling the fuel injection valve and the ignition device, which executes a stand-by processing of maintaining a state of stopping fuel injection since a starting is determined until it is determined that the exhaust action by the valve train is executed when a predetermined stand-by condition is satisfied, controls the fuel injection valve to inject a fuel, and control the ignition device to execute a start combustion processing for igniting the fuel in the cylinder when the stand-by processing is finished.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] This disclosure relates to techniques for starting an engine. [Background technology]

[0002] Patent Document 1 discloses performing control to adjust the opening of the throttle valve when the engine is started. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-044621 A Summary of the Invention [Problem to be solved by the invention]

[0004] When starting the engine, the mixture concentration of air and fuel in the combustion chamber may vary depending on the fuel remaining in the combustion chamber.

[0005] Therefore, an object of the present disclosure is to suppress variations in the mixture concentration in the combustion chamber when the engine is started. [Means for solving the problem]

[0006] In order to solve the above problems, the engine comprises an engine body having a cylinder, a piston that reciprocates within the cylinder, a crankshaft that rotates in conjunction with the reciprocating movement of the piston, and a valve mechanism that performs intake and exhaust operations into the cylinder in conjunction with the reciprocating movement of the piston, a fuel injection valve that injects fuel, an ignition device that ignites the fuel in the cylinder, and a control device that controls the fuel injection valve and the ignition device, and when a predetermined standby condition is satisfied, executes a standby process that maintains a state in which fuel injection is stopped from determining that starting has begun until it determines that an exhaust operation has been performed by the valve mechanism, and when the standby process is terminated, executes a startup combustion process that controls the fuel injection valve to inject fuel and controls the ignition device to ignite the fuel in the cylinder.

[0007] According to this engine, fuel injection is stopped during the standby process after the start of the engine. As a result, during the standby process, unburned gas remaining in the cylinder is discharged by the exhaust operation of the valve mechanism caused by the reciprocating movement of the piston. When the start combustion process is subsequently performed, fuel combustion is performed with the remaining unburned gas in the cylinder discharged. By discharging the unburned gas remaining before the start in this manner, the influence of the remaining unburned gas can be suppressed, and the variation in the mixture concentration in the combustion chamber at the time of engine start can be suppressed.

[0008] In addition, the engine control device is an engine control device that controls the fuel injection valve and ignition device in the engine, and executes: (a) a standby process that maintains a stopped state of fuel injection from when it is determined that the start of startup has begun until it is determined that an exhaust operation has been performed by the valve mechanism, when a predetermined standby condition is satisfied; and (b) a startup combustion process that controls the fuel injection valve to inject fuel and controls the ignition device to ignite the fuel in the cylinder, when the standby process is terminated.

[0009] According to this engine control device, fuel injection is stopped during the standby process after the start of the engine. As a result, during the standby process, unburned gas remaining in the cylinder is discharged by the exhaust operation of the valve mechanism caused by the reciprocating movement of the piston. When the start combustion process is subsequently performed, fuel combustion is performed with the unburned gas remaining in the cylinder discharged. By discharging the unburned gas remaining before start in this manner, the influence of the remaining unburned gas in the engine to be controlled can be suppressed, and the variation in the mixture concentration in the combustion chamber at the time of engine start can be suppressed.

[0010] In addition, the engine control method is an engine control method that controls a fuel injection valve and an ignition device in the engine, and includes: (a) a process for maintaining a stopped state of fuel injection from when it is determined that the start of starting has begun until it is determined that an exhaust operation has been performed by the valve mechanism, when a predetermined standby condition is satisfied; and (b) a process for controlling the fuel injection valve to inject fuel and controlling the ignition device to ignite the fuel in the cylinder, when the process (a) is completed.

[0011] According to this engine control method, fuel injection is stopped during the standby process after the start of the engine. As a result, during the standby process, unburned gas remaining in the cylinder is exhausted by the exhaust operation of the valve mechanism caused by the reciprocating movement of the piston. When the start combustion process is subsequently performed, fuel combustion is performed with the unburned gas remaining in the cylinder exhausted. By exhausting the unburned gas remaining before start in this manner, the influence of the remaining unburned gas in the engine to be controlled can be suppressed, and the variation in the mixture concentration in the combustion chamber at the time of engine start can be suppressed. Effect of the Invention

[0012] It is possible to suppress variations in the mixture concentration in the combustion chamber when the engine is started. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing an engine according to an embodiment; [Diagram 2] FIG. 2 is a block diagram showing the electrical configuration of the engine. [Diagram 3] 5 is a flowchart showing an example of a process performed by a control device. [Figure 4] 5 is a timing chart showing the processing timing of each part of the engine when standby processing is performed. [Diagram 5] 10A to 10C are explanatory diagrams showing the operation of movable parts of the engine when standby processing is performed; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An engine, its control device, and method according to an embodiment will be described below. Fig. 1 is a schematic diagram showing an engine 20 according to an embodiment. The engine 20 is a machine that obtains power by burning fuel. The engine 20 may be used as a power source for a vehicle, or may be used as a power source for a mechanical device. The vehicle may be a straddle-type vehicle such as a motorcycle, a three-wheeled vehicle, an ATV (All Terrain Vehicle), or a personal watercraft, or may be a vehicle such as a large riding lawnmower.

[0015] The engine 20 includes an engine body 30 , a fuel injection valve 50 , an ignition device 52 , and a control device 60 .

[0016] The engine body 30 is a mechanical structure that generates mechanical energy by combustion gas. The fuel injection valve 50 is a valve that supplies fuel to the engine body 30. The ignition device 52 is a device for igniting fuel in the engine body 30. The control device 60 controls the fuel injection timing by the fuel injection valve 50, the ignition timing by the ignition device 52, etc., according to the engine cycle.

[0017] The engine 20 is started by igniting the fuel supplied from the fuel injection valve 50 to the engine body 30 by the ignition device 52. However, depending on the starting environment of the engine 20, the mixture concentration may deviate from the range suitable for combustion due to the influence of residual unburned gas in the engine body 30. In such a starting environment, fuel injection by the fuel injection valve 50 is stopped from when the start of the engine 20 is determined until the exhaust operation is determined to be performed. This eliminates the influence of the residual unburned gas, and the mixture concentration in the engine body 30 is reset to be as lean as possible. After this, fuel is supplied from the fuel injection valve 50 to the engine body 30, and the fuel is ignited by the ignition device 52. Therefore, the fuel is ignited at a mixture concentration suitable for combustion, and the engine is started well.

[0018] A more specific example will be described. The engine body 30 includes a cylinder 33, a piston , a crankshaft 40, and a valve mechanism .

[0019] The cylinder 33 is a cylindrical part formed in the main body 32 which is the base of the engine main body 30. The main body 32 is a part that forms a combustion chamber, a space in which the piston 34 moves, a space in which the crankshaft rotates, and the like. For example, the main body 32 is constructed by combining, in order from top to bottom, a cylinder head, a cylinder block, a crankcase, and an oil pan. The cylinder 33 is formed in the cylinder block. The cylinder 33 is a part that forms a cylindrical space in which the piston 34 moves, and forms a combustion chamber. By combining the cylinder head on the cylinder block, the upper opening of the cylinder 33 is closed by the cylinder head. By combining the crankcase below the cylinder block, a space in which the crankshaft 40 rotates is formed on the opposite side of the cylinder head with respect to the cylinder 33. The oil circulating in the engine 20 is stored in the oil pan combined below the crankcase. The number of the cylinders 33 is not particularly limited, and may be one cylinder, two cylinders, or a greater number of cylinders.

[0020] The piston 34 is a member arranged reciprocally within the cylinder 33, with one end space and the other end space separated from each other within the cylinder 33. The movement of the piston 34 within the cylinder 33 enables compression, expansion, intake, and exhaust within the space within the cylinder 33.

[0021] The crankshaft 40 is rotatably disposed in a space on the opposite side of the cylinder head with respect to the cylinder 33. The rotation axis of the crankshaft 40 is set to be perpendicular to the reciprocating direction of the piston 34. The crankshaft 40 includes a shaft 40a, a crank arm 40b, and a crank pin 40c, and is rotatably supported by the main body 32. The rotation axis of the crankshaft 40 coincides with the central axis of the shaft 40a. The crank pin 40c is supported by the crank arm 40b at a position offset from the rotation axis of the shaft 40a. As the crankshaft 40 rotates, the crank pin 40c rotates around the rotation axis of the crankshaft 40. The piston 34 and the crank pin 40c are connected by a connecting rod 38. The reciprocating motion of the piston 34 is transmitted to the crankshaft 40 as a rotational motion via the connecting rod 38. The rotational motion of the crankshaft 40 is also transmitted to the piston 34 as a reciprocating motion via the connecting rod 38. That is, the crankshaft 40 can rotate in conjunction with the reciprocating movement of the piston 34. The crank arms 40b and the crank pins 40c are provided in accordance with the number of cylinders.

[0022] The valve mechanism 46 performs intake and exhaust operations into the cylinder 33 in conjunction with the reciprocating movement of the piston 34. The valve mechanism 46 includes, for example, an intake valve 47, an exhaust valve 48, and a valve opening / closing unit 49 that opens and closes the valves 47, 48. The intake valve 47 and the exhaust valve 48 are provided in a portion that closes the upper opening of the cylinder 33, for example, in the cylinder head.

[0023] More specifically, an intake port is formed in a portion of the cylinder head that closes the upper opening of the cylinder 33, and an intake valve 47 is provided in the intake port. The intake port is connected to an outside air intake port via an intake port 47P or the like. Outside air is taken into the cylinder 33 from the intake port 47P through the intake port. The intake valve 47 is supported so as to be displaceable between a closed position that closes the intake port and an open position that opens it. Depending on the opening and closing positions of the intake valve 47, a state in which outside air is taken into the cylinder 33 and a state in which the intake is suppressed are switched. The intake port 47P is provided with an intake amount adjustment device 47V including a throttle valve 47Va that is controlled to open and close depending on the operation of the throttle, etc. The throttle valve 47Va is, for example, a butterfly valve. The amount of intake into the cylinder 33 can be adjusted depending on the opening and closing degree of the throttle valve 47Va.

[0024] In addition, an exhaust port is formed in a portion of the cylinder head that closes the upper opening of the cylinder 33, and an exhaust valve 48 is provided in the exhaust port. The exhaust port is connected to an external exhaust port via an exhaust port 48P or the like. Gas in the cylinder 33 is exhausted from the exhaust port through the exhaust port 48P or the like. The exhaust valve 48 is supported so as to be displaceable between a closed position that closes the exhaust port and a closed position that opens it. Depending on the opening and closing positions of the exhaust valve 48, the state is switched between a state in which the gas in the cylinder 33 is exhausted to the outside and a state in which the exhaust is suppressed. Note that there may be one or more intake ports and intake valves for one cylinder 33. Similarly, there may be one or more exhaust ports and exhaust valves for one cylinder 33.

[0025] The valve opening / closing unit 49 includes, for example, a camshaft 49a, a rotation transmission mechanism 49b, and the like. The camshaft 49a is rotatably supported on the opposite side of the cylinder 33 with respect to the intake valve 47 and the exhaust valve 48. The camshaft 49a has cam portions corresponding to the intake valve 47 and the exhaust valve 48. For example, the rotation of the camshaft 49a causes the intake valve 47 and the exhaust valve 48, which are biased toward the open position by a spring or the like, to reciprocate between the open position and the closed position. The rotation transmission mechanism 49b includes at least one of a chain, a gear, and the like, and transmits the rotational motion of the crankshaft 40 as a force to rotate the camshaft 49a. That is, the crankshaft 40 rotates in conjunction with the reciprocating movement of the piston 34, and the rotation of the crankshaft 40 is transmitted to the camshaft 49a by the rotation transmission mechanism 49b, causing the camshaft 49a to rotate. The rotation of the camshaft 49a moves the intake valve 47 and the exhaust valve 48 between an open position and a closed position, thereby performing the intake operation and the exhaust operation into the cylinder 33 in conjunction with the reciprocating movement of the piston 34.

[0026] As described above, the number of cylinders 33 is arbitrary, and the cam portions corresponding to the intake valves 47 and exhaust valves 48 are provided according to the number of cylinders. In the cylinders 33, the opening and closing timing of the intake valves 47 and exhaust valves 48 relative to the reciprocating movement of the pistons 34 (rotation of the crankshaft 40) can be set by adjusting the transmission speed ratio (gear ratio, etc.) in the rotation transmission mechanism.

[0027] The fuel injection valve 50 is connected to a fuel tank that stores fuel, and injects fuel to supply the fuel into the cylinder 33. The fuel may be injected into the intake port 47P, or may be directly injected into the cylinder 33. FIG. 1 shows an example in which the fuel injection valve 50 is provided in the intake port 47P at a position where the fuel is injected downstream of the throttle valve 47Va. The fuel injected from the fuel injection valve 50 is mixed with outside air passing through the intake port 47P and is supplied into the cylinder 33. The fuel is, for example, gasoline.

[0028] Ignition device 52 is a device that supplies ignition energy for igniting fuel in cylinder 33. For example, ignition device 52 ignites fuel in cylinder 33 at a predetermined ignition timing by a voltage supplied from a high-voltage circuit. Ignition device 52 is provided in a portion of main body 32 that closes an upper opening of cylinder 33, for example, in an engine head.

[0029] The control device 60 controls the fuel injection valve 50 and the ignition device 52. The control device 60 may be configured by a computer that operates by receiving power supply from a battery provided in the engine 20. When a predetermined standby condition is satisfied, the control device 60 executes a standby process for maintaining a state in which fuel injection by the fuel injection valve 50 is stopped after determining that the start has begun, until determining that the exhaust operation by the valve mechanism 46 has been performed. In addition, when the control device 60 ends this standby process, it executes a startup combustion process for controlling the fuel injection valve 50 to inject fuel and controlling the ignition device 52 to ignite the fuel in the cylinder 33.

[0030] The engine 20 is equipped with an operating unit such as a switch for starting the engine 20, a starter motor, and a rotation detection device for detecting the rotation of the crankshaft 40.

[0031] Here, the engine 20 includes a power switch 21 and a start switch 22 as operation units. The power switch 21 and the start switch 22 are provided on a housing that houses the engine 20, or on an operation panel for operating the engine 20. The power switch 21 and the start switch 22 are configured as a push switch, a rotary switch, a touch switch, or the like. When the power switch 21 is turned on, electricity is supplied to the control device 60, etc., and the engine 20 is in a state where it can be started. When the start switch 22 is turned on, the engine 20 is started, and the reciprocating movement of the piston 34 and the rotation of the crankshaft 40 due to the combustion of fuel continue. The power on / off operation for the engine 20 and the start operation for the engine 20 may be received by an operation on a mobile terminal device such as a mobile phone or a portable key.

[0032] The starter motor 24 is an electric motor that rotates the crankshaft 40 when the engine 20 is started. The starter motor 24 rotates by receiving power supply from a separately provided battery. When the engine is started, the rotational motion of the starter motor 24 is transmitted to the crankshaft 40 via a starter one-way clutch or the like. When the engine 20 starts by the combustion of fuel in the cylinders 33, the power transmission path from the crankshaft 40 to the starter motor 24 is cut off by the starter one-way clutch. As a result, the crankshaft 40 rotates and the engine 20 can continue to operate regardless of whether the starter motor 24 is rotating or stopped.

[0033] The starter motor 24 may be omitted, and instead, when starting the engine 20, the crankshaft may be rotated by force such as the user's foot operating a kick pedal or hand operating a starting handle.

[0034] The rotation detector 26 is a sensor that detects the rotation of the crankshaft 40. For example, the rotation detector 26 may detect the rotation of the rotor 40R that rotates integrally with the crankshaft 40. More specifically, for example, the rotation detector 26 may be a magnetic sensor. In this case, one or more magnetic protrusions 40Ra may be provided on a part of the outer periphery of the rotor 40R, and the rotation of the crankshaft 40 may be detected according to a change in a magnetic field accompanying the rotation of the crankshaft 40. The rotation detector 26 may detect the rotation angle (crank angle) of the crankshaft 40. For example, a plurality of protrusions 40Ra may be provided around the rotor 40R at a certain angle, and the rotation angle of the crankshaft 40 may be detected by detecting each of the protrusions 40Ra.

[0035] The rotation detection device 26 does not have to be a magnetic sensor, and may be an eddy current displacement sensor or an optical sensor. The rotation detection device 26 may be any device that can directly or indirectly detect the rotation of the crankshaft 40, and therefore may indirectly detect the rotation of the crankshaft 40 by detecting the rotation of the starter motor 24, the camshaft 49a, which move synchronously with the crankshaft 40, and shafts in the rotational motion transmission mechanism between them and the crankshaft 40.

[0036] The engine 20 may include a water temperature sensor 27 as an example of a temperature detection unit that detects the temperature of the engine 20 before fuel is burned in the cylinders 33 (see FIG. 2). The water temperature sensor 27 is a temperature sensor that detects the temperature of the coolant of the engine 20. The water temperature sensor is provided somewhere along the flow of the coolant. Since the temperature of the coolant changes depending on the temperature of the engine 20, the temperature of the engine 20 is detected by detecting the temperature of the coolant. It is not essential that the temperature detection unit is the water temperature sensor 27, and the temperature detection unit may be an oil temperature sensor 28. The oil temperature sensor 28 is a temperature sensor that detects the temperature of the engine oil circulating through the engine 20. The oil temperature sensor 28 is provided, for example, at a position that detects the temperature of the engine oil stored in an oil pan.

[0037] 2 is a block diagram showing the electrical configuration of the engine 20. As shown in the figure, the water temperature sensor 27, the rotation detector 26, the power switch 21, and the start switch 22 are connected to the control device 60, and detection signals or operation signals therefrom are provided to the control device 60. In addition, the ignition device 52, the fuel injection valve 50, and the air supply amount regulator 47V are connected to the control device 60, and the control device 60 adjusts the ignition timing by the ignition device 52, the fuel injection timing by the fuel injection valve 50, and the intake amount by the air supply amount regulator 47V. The starter motor 24 may be turned on and off by the start switch 22 via the control device 60, or may be turned on and off directly by the start switch 22.

[0038] The control device 60 is configured by a computer including a processor 62 such as a CPU (Central Processing Unit), a storage unit 63, and the like. The storage unit 63 is configured by a non-volatile storage device such as an HDD (hard disk drive) or an SSD (solid-state drive). The storage unit 63 stores a program 63a, a standby condition setting condition 63b, and the like. The processor 62 performs processing according to the pre-stored program 63a, thereby performing a control process of the engine 20, which will be described later, in particular, a process related to starting the engine 20. That is, the program 63a is a program for causing the control device 60, which is a computer, to perform a process related to a control method for the engine 20. The standby condition setting condition 63b specifies a standby condition for performing the standby process. The standby condition in the standby condition setting condition 63b may be a condition set based on a temperature related to the engine 20 before combustion. For example, a first threshold temperature assuming a hot start may be set as the standby condition, and the standby condition may be set to be satisfied when the detected temperature related to the engine 20 exceeds or is equal to or higher than the first threshold temperature. Also, for example, a second threshold temperature assuming a constant temperature environment lower than normal temperature may be set as the standby condition, and the standby condition may be satisfied when the detected temperature of the engine 20 is lower than or equal to the second threshold temperature. More specifically, a value of 40 degrees Celsius to 60 degrees Celsius (for example, 50 degrees Celsius) may be set as the first threshold temperature, and a value of 10 degrees Celsius to -10 degrees Celsius (for example, 0 degrees Celsius) may be set as the second threshold temperature. The processor 62 may determine whether the standby condition is satisfied by, for example, comparing the temperature based on the water temperature sensor 27 with a temperature set in the standby condition setting condition. In the standby condition setting condition 63b, an exhaust operation completion condition may be associated with the standby condition. The exhaust operation completion condition is a condition for completing the exhaust operation after the exhaust operation without fuel injection is started. The exhaust operation completion condition may be defined, for example, by the rotation speed of the crankshaft 40, or may be defined by time. More specifically, the exhaust operation completion condition may be defined by the number of revolutions after the rotation detector 26 detects the rotation of the crankshaft 40 after the engine 20 has started to start.

[0039] FIG. 3 is a flowchart showing an example of processing by the control device 60.

[0040] When the power switch 21 is turned on, the control device 60 starts up and executes the process of step S1. The process of step S1 is a process for determining whether or not a predetermined standby condition is satisfied. In this embodiment, in step S1, it is determined whether or not the standby condition is a hot start, as an example of the standby condition. A hot start is a start under a temperature condition higher than the temperature at which the engine 20 is left in a normal temperature environment. A hot start is, for example, a case in which the engine 20 is restarted before being sufficiently cooled after being stopped. The determination in step S1 is made, for example, by comparing the temperature of the engine 20 before combustion with a first threshold temperature defined in the standby condition setting condition 63b. The temperature of the engine 20 before combustion is, for example, the temperature of the coolant detected by the water temperature sensor 27. If the temperature of the coolant exceeds or is equal to or higher than the first threshold temperature, it is determined that the hot start is occurring.

[0041] The temperature of the engine 20 before combustion is the temperature of a portion related to the temperature inside the cylinder 33, for example, a portion having a temperature that shows a positive correlation with the temperature inside the cylinder 33. Such a temperature of the engine 20 before combustion does not need to be the temperature of the coolant. As the temperature of the engine 20 before combustion, for example, the temperature of any portion of the main body 32 of the engine 20 may be detected, the temperature of the engine oil circulated in the engine 20 may be detected, or the intake air temperature in the air cleaner chamber may be detected. The first threshold temperature, the second threshold temperature, etc. are set to temperatures corresponding to the respective detection portions of the cylinders 33 in the engine 20.

[0042] If it is determined that the engine is a hot start, the process proceeds to step S2, where an exhaust operation completion condition for a hot start is set. The exhaust operation completion condition is, for example, specified by a condition for the case where the temperature exceeds or is equal to or higher than the first threshold temperature in the standby condition setting condition 63b, and the control device 60 may set the exhaust operation execution completion condition by referring to the standby condition setting condition 63b. For example, the exhaust operation completion condition may be specified as the crankshaft 40 rotating N times. N may be one rotation, two rotations, or three or more rotations. Assuming that the engine 20 is a four-stroke engine, as described later, N may be two or more. The set condition is temporarily stored in the storage unit.

[0043] If it is determined in step S1 that the start is not a hot start, the process proceeds to step S11. The process of step S11 is a process of determining whether or not another predetermined standby condition is satisfied. In this embodiment, in step S11, it is determined whether or not the start is a low temperature start, as an example of the standby condition. The low temperature start is a start under a temperature condition lower than the temperature at which the engine 20 is left in a normal temperature environment. The low temperature start is, for example, a case in which the engine 20 is started in a state in which the engine 20 is exposed to a severe cold environment. The low temperature start may be a start in an extremely cold environment. In this connection, the extremely cold environment refers to an environment in which the temperature is so low that the engine start is not stable with the fuel injection amount at room temperature. It also refers to an environment in which the temperature is so low that adjustment of the fuel injection amount or the intake amount is necessary. In such an environment, fuel that is not vaporized is likely to accumulate in the cylinder, and the mixture concentration is likely to vary. The determination in step S11 is made, for example, by comparing the temperature of the engine 20 before combustion with the second threshold temperature specified in the standby condition setting condition 63b, similar to step S1. The temperature of the engine 20 before combustion may be the temperature of the engine oil detected by the water temperature sensor 27, as described above, or it may be the temperature of another part related to the temperature inside the cylinder 33.

[0044] If it is determined that the engine is a cold start, the process proceeds to step S12, where an exhaust operation completion condition for a cold start is set. The exhaust operation completion condition is defined by the rotation speed of the crankshaft 40 in the standby condition setting condition 63b, as in step S2, and may be set by referring to the standby condition setting condition 63b. In this case, the rotation speed may be the same as the rotation speed defined as the exhaust operation completion condition for a hot start, or may be different. The set condition is temporarily stored in the memory unit.

[0045] After step S2 and after step S12, the process proceeds to step S3. That is, steps S2 and S12 are performed when a predetermined waiting condition is satisfied, and in this case, the processes from step S3 onward are executed. In step S3, it is determined whether the start switch 22 has been turned on. The process of step S3 is repeated until the start switch 22 is turned on, and when the start switch 22 is turned on, the process proceeds to step S4. When the start switch 22 is turned on, a rotation start signal is given to the starter motor 24, and the starter motor 24 rotates. The rotation of the starter motor 24 rotates the crankshaft 40, and the piston 34 reciprocates in conjunction with the rotation.

[0046] In step S4, the control device 60 detects the presence or absence of rotation of the crankshaft 40 based on the output from the rotation detection device 26. If the presence of the initial rotation of the crankshaft 40 is detected, it is determined that starting has begun, and the process proceeds to step S5.

[0047] In step S5, the control device 60 adds 1 to the count variable indicating the number of revolutions of the crankshaft 40 (increment process), and then proceeds to step S6.

[0048] In step S6, the control device 60 causes the ignition device 52 to perform an ignition operation. The ignition operation is an operation of igniting fuel in the cylinder 33 during the combustion stroke of the engine 20. For example, the control device 60 causes the ignition device 52 to perform the ignition operation at a timing synchronized with the rotation angle of the crankshaft 40 detected by the rotation detection device 26.

[0049] In the next step S7, it is determined whether or not the exhaust operation completion condition is satisfied. For example, when the exhaust operation completion condition is determined by the rotation speed of the crankshaft 40, the count variable incremented in step S5 is compared with the exhaust operation completion determination condition set for hot start or low temperature start in step S2 or step S12 to determine whether or not the exhaust operation completion condition is satisfied. That is, the timing at which the exhaust operation ends is determined based on the detection result of the rotation detection device 26. For example, when the exhaust operation completion condition is set as two rotations of the crankshaft 40, it may be determined that the exhaust operation completion condition is satisfied when the rotation speed of the crankshaft 40 becomes two or more (when the number of detections of the protrusion 40Ra of the rotor 40R becomes three or more). That is, when the crankshaft 40 rotates at a rotation speed or more set as the exhaust operation completion condition, it is found that the piston 34 has reciprocated a predetermined number of times or more in association with the rotation of the crankshaft 40. If the piston 34 has reciprocated a predetermined number of times, it can be determined that the exhaust operation by the valve mechanism 46 has been completed. Therefore, it is determined whether or not the exhaust operation completion condition is satisfied based on the rotation speed of the crankshaft 40. If it is determined in step S7 that the exhaust operation completion condition is not satisfied, the process returns to step S4, and the processes of steps S4, S5, and S6 are repeated. Therefore, the count variable is incremented every time the crankshaft 40 rotates. If it is determined in step S7 that the exhaust operation completion condition is satisfied, the process proceeds to step S8.

[0050] The processes of steps S4, S5, and S6 are repeated until it is determined in step S7 that the exhaust operation completion condition is satisfied. During this process, the control device 60 maintains a state in which fuel injection by the fuel injection valve 50 is stopped. This series of processes is an example of a standby process in which the fuel injection is maintained in a stopped state from when the start-up start is determined by detecting the initial rotation of the crankshaft 40 until it is determined that the crankshaft 40 has rotated the number of times specified in the exhaust operation completion condition and the exhaust operation by the valve mechanism 46 has been performed. In this embodiment, an ignition operation is performed in the standby process (see step S6). However, the process of step S6 may be omitted and the ignition operation may be stopped in the standby process.

[0051] In step S8, the control device 60 causes the fuel injection valve 50 and the ignition device 52 to execute the startup combustion process. That is, the control device 60 injects fuel from the fuel injection valve 50 in the intake stroke where the piston 34 moves toward the bottom dead center in accordance with the crank angle of the crankshaft 40 to supply the fuel into the cylinder 33, and ignites the fuel in the cylinder 33 by the ignition device 52 in the early stage of the combustion stroke where the piston 34 is located near the top dead center. In this way, the engine 20 is started.

[0052] Thereafter, the process proceeds to step S9, where engine control is executed to repeat fuel injection by the fuel injection valve 50 and ignition by the ignition device 52 in accordance with the crank angle.

[0053] In this embodiment, if it is determined in step S1 that the start is not hot and if it is determined in step S2 that the start is not cold, it is determined that the predetermined standby condition is not satisfied. In this case, the start combustion process is executed without going through the standby process after the start start is determined, and the process from step S21 onwards is executed.

[0054] First, in step S21, the simulated standby process completion condition is set. The simulated standby process completion condition is, for example, specified in the standby condition setting condition 63b as a condition for the case where the temperature is less than or equal to the first threshold temperature and exceeds or equal to the second threshold temperature (that is, the case where the start is neither hot nor cold), and the control device 60 may set the simulated standby process completion condition by referring to the standby condition setting condition 63b. The simulated standby process completion condition may be set as a condition that is shorter than the period during which the standby process is to be executed. For example, the simulated standby process completion condition may be specified as the crankshaft 40 making N revolutions, similar to the exhaust operation completion condition. The number of revolutions in this case may be less than the number of revolutions specified as the exhaust operation completion condition. This allows the number of revolutions N of the crankshaft to be minimized in a situation where the mixture concentration is relatively unlikely to vary. This reduces the possibility of the crankshaft not rotating undesirably, thereby reducing the loss of the rider's feeling. For example, if the exhaust operation completion condition is defined as two rotations of the crankshaft 40, the simulated standby process completion condition may be defined as one rotation of the crankshaft 40. The set condition is temporarily stored in the storage unit.

[0055] In the next step S22, it is determined whether the start switch 22 has been turned on. The process of step S22 is repeated until the start switch 22 is turned on, and when the start switch 22 is turned on, the process proceeds to step S23. When the start switch 22 is turned on, a rotation start signal is provided to the starter motor 24, and the starter motor 24 rotates.

[0056] In steps S23 to S25, the same processes as in steps S4 to S6 above are executed.

[0057] In step S26 after step S25, it is determined whether the simulated standby process completion condition is satisfied. For example, if the simulated standby process completion condition is determined by the rotation speed of the crankshaft 40, the count variable incremented in step S24 is compared with the simulated standby process completion condition set in step S21 to determine whether the simulated standby process completion condition is satisfied. For example, if the simulated standby process completion condition is set to one rotation of the crankshaft 40, it may be determined that the simulated standby process completion condition is satisfied when the rotation speed of the crankshaft 40 becomes one rotation or more (when the number of detections of the protrusion 40Ra of the rotor 40R becomes two or more). If it is determined in step S26 that the simulated standby process completion condition is not satisfied, the process returns to step S23, and the processes of steps S23, S24, and S25 are repeated. If it is determined in step S26 that the simulated standby process completion condition is satisfied, the process proceeds to step S8, and the start combustion process is executed. The processes of steps S23, S24, and S25 are repeated until it is determined in step S26 that the simulated standby process completion condition is satisfied. During this process, the control device 60 maintains a state in which fuel injection by the fuel injection valve 50 is stopped. This series of processes is an example of the simulated standby process.

[0058] The above-mentioned simulated standby process may be omitted. In this case, if it is determined that NO is returned in step S11 (that is, if it is determined that the standby condition is not satisfied), the process may proceed to step S8 and the startup combustion process may be executed.

[0059] FIG. 4 is a timing chart showing the processing timing of each part of the engine 20 when the standby process is performed.

[0060] 4, when the power switch 21 is turned on, the control device 60 and the like are energized and become capable of control operations. After that, when the start switch 22 is turned on, the starter motor 24 rotates, and the rotation of the starter motor 24 rotates the crankshaft 40.

[0061] Thereafter, the rotation of crankshaft 40 caused by the rotational drive of starter motor 24 is detected by rotation detection device 26. In this case, the rotation of crankshaft 40 may be detected with a delay after the rotational drive of starter motor 24. For example, if rotation detection device 26 is a magnetic sensor that detects the rotation of crankshaft 40 by a change in a magnetic field, when crankshaft 40 exceeds a certain rotational speed, the magnetic field may change to an extent that can be detected by rotation detection device 26. In such a case, after start of rotation of crankshaft 40 by starter motor 24, the rotation of crankshaft 40 may be detected by rotation detection device 26 only after the rotational speed of crankshaft 40 reaches a rotational speed exceeding a detection limit.

[0062] When rotation of the crankshaft 40 is detected, a standby condition control flag is set in the control device 60, and standby processing (see steps S4 to S7) is executed. During this processing, an injection cut command is output to stop fuel injection from the fuel injection valve 50. As a result, fuel injection from the fuel injection valve 50 is stopped during standby processing. Note that, when an ignition operation by the ignition device 52 is to be performed during standby processing (see step S6), the ignition cut command during standby processing is not output. When an ignition operation by the ignition device 52 is to be stopped during standby processing, an ignition cut command during standby processing is output (see dashed double-dashed line).

[0063] Next, the rotation detection device 26 detects the rotation of the crankshaft 40, and when it is determined that the rotation speed exceeds the rotation speed specified as the exhaust operation completion condition (for example, two rotations, or three rotations in terms of the rotation detection number), it is determined that the exhaust operation (standby processing operation) is completed.

[0064] When the exhaust operation (standby processing operation) is completed, the standby condition control flag is cleared and the injection cut command is turned off. If an ignition cut command has been output during the exhaust operation, it is also turned off. If the start switch 22 is subsequently kept in the on state, the starter motor 24 continues to rotate, and the crankshaft 40 continues to rotate by the starter motor 24. After the exhaust operation is completed, the start combustion process is executed, fuel is injected from the fuel injection valve 50, and an ignition operation is performed by the ignition device 52. This ignites the fuel in the cylinder 33, and the engine 20 ignites. After the engine ignition, the on operation of the start switch 22 is released and the rotation of the starter motor 24 is stopped. With the start of the engine 20, the crankshaft 40 continues to rotate at idling speed.

[0065] 5 is an explanatory diagram showing the operation of the movable parts of the engine 20 when the standby process is performed. In FIG. 5, the operation is depicted assuming that the engine is a four-stroke engine.

[0066] In (a) of FIG. 5, the piston 34 moves from the top dead center to the bottom dead center. In this state, the intake valve 47 is open and the exhaust valve 48 is closed. Therefore, outside air can flow into the cylinder 33 through the intake port. In (b) of FIG. 5, the piston 34 moves from the bottom dead center to the top dead center. In this state, both the intake valve 47 and the exhaust valve 48 are closed, and the gas in the cylinder 33 is compressed. In (c) of FIG. 5, the piston 34 is located near the top dead center. In this state, both the intake valve 47 and the exhaust valve 48 are closed, and the gas in the cylinder 33 is in the most compressed state. In (d) of FIG. 5, the piston 34 moves from the bottom dead center to the top dead center. In this state, the intake valve 47 is closed and the exhaust valve 48 is open. Therefore, the gas in the cylinder 33 is discharged to the outside through the exhaust port.

[0067] In the start-up combustion process and the normal operation control process of the engine 20 (see steps S8 and S9), fuel is injected from the fuel injector 50 in the process shown in FIG. 5(a) (intake stroke). In the next process shown in FIG. 5(b), the mixture containing the fuel is compressed in the cylinder 33 (compression stroke). In the next process shown in FIG. 5(c), the fuel contained in the mixture in the cylinder 33 is ignited by the ignition device 52, which causes the gas in the cylinder 33 to expand and push the piston 34 toward the bottom dead center (ignition and expansion stroke). In the subsequent process shown in FIG. 5(d), the gas after combustion in the cylinder 33 is discharged by the piston 34. In this way, the stroke of making the piston 34 reciprocate twice (making the crankshaft 40 rotate twice) is repeated in the above order as one cycle.

[0068] In the exhaust operation performed by the standby process, the piston 34 reciprocates due to the rotation of the crankshaft 40, and the intake valve 47 and the exhaust valve 48 of the valve mechanism 46 operate in conjunction with the rotation of the crankshaft 40. Different from the above, in the step shown in Fig. 5(a), the injection of fuel from the fuel injection valve 50 is stopped. Therefore, an intake operation is performed accompanied by the introduction of fresh outside air into the cylinder 33.

[0069] In addition, the control device 60 may control the supply air amount regulator 47V in the standby process so as to increase the intake passage area in the intake port 47P compared to before the standby process. For example, the intake passage area in the intake port 47P is adjusted by the opening degree of the throttle valve 47Va of the supply air amount regulator 47V. If the throttle valve 47Va is in a state in which the intake port 47P is most closed before the standby process, the throttle valve 47Va may be opened more than the closed state in the standby process so that outside air can easily flow through the intake port 47P. The opening degree of the throttle valve 47Va in the standby process may be equal to the opening degree during idling, or may be an opening degree between the opening degree during idling and the fully open state. The amount of intake air from the intake port 47P in the standby process may be adjusted by an idle speed control valve. The idle speed control valve is a valve that adjusts the flow rate in the bypass flow passage of the intake port 47P, and may be understood as a component of the intake air amount regulator. It should be noted that the area of ​​the intake passage needs to be increased at least during the stroke in which air is taken in (see FIG. 5(a)).

[0070] In the next step shown in Fig. 5(b), the gas in the cylinder 33 is compressed, and in the next step shown in Fig. 5(c), the piston 34 reaches near the top dead center. When the ignition operation is performed by the ignition device 52 in the step shown in Fig. 5(c), as described above, fresh outside air is taken into the cylinder 33, so ignition is difficult. However, if fuel remains in the cylinder 33, the remaining fuel may be ignited. This ignition ignites the engine 20, and normal engine operation control may be performed subsequently.

[0071] 5(d), the piston 34 moves toward the top dead center due to the rotation of the crankshaft 40. This causes an exhaust operation, and even if unburned gas remains in the cylinder 33, the remaining unburned gas is exhausted to the outside through the exhaust port.

[0072] When the standby process is performed for a period including the intake operation (see FIG. 5(a)) and the exhaust operation (see FIG. 5(d)), the remaining fuel in the cylinders 33 is easily discharged. Assuming a four-stroke engine, two revolutions of the crankshaft 40 will perform all the cycles (a), (b), (c), and (d) described above, regardless of the number and position of the cylinders, and fresh outside air will be introduced into the cylinders 33 and gas in the cylinders 33 will be discharged. For this reason, the condition for determining that the exhaust process is complete may be set to be that the crankshaft 40 has made a predetermined number of revolutions or more, two or more revolutions. In this way, by determining the completion of the exhaust operation based on the rotation speed of the crankshaft 40, the timing of the completion of the exhaust operation can be determined more accurately than when the completion of the exhaust operation is determined based on the elapsed time or the like.

[0073] According to the engine 20, its control device 60, and the method configured as described above, fuel injection is stopped during the standby process (exhaust operation) from the start of starting. Therefore, during the standby process, unburned gas remaining in the cylinder 33 is discharged by the exhaust operation (operation of opening the exhaust valve 48) of the valve mechanism 46 linked to the reciprocation of the piston 34. During the subsequent start combustion process, fuel is supplied to the cylinder 33 with the remaining unburned gas in the cylinder 33 once discharged. Therefore, by suppressing the influence of the remaining unburned gas, it is possible to suppress the variation in the mixture concentration in the cylinder 33 at the start of the engine 20. Furthermore, it is possible to prevent poor combustion due to the influence of the remaining unburned gas, and to prevent a decrease in startability.

[0074] In addition, when the standby conditions serving as the criterion for determining whether or not to perform standby processing are set based on the temperature of the engine 20 before combustion, the standby conditions are set according to the temperature that affects the mixture concentration due to the residual unburned gas in the cylinder 33, and appropriate exhaust of the residual unburned gas is achieved.

[0075] That is, if residual unburned gas due to blow-by gas or the like remains in the cylinder 33 before combustion, even if further fuel is supplied to the cylinder 33 to ignite it, the mixture concentration becomes too rich, and ignition may not be successful. When the engine 20 is hot started, the fuel in the cylinder 33 is likely to volatilize, which is likely to affect the mixture concentration in the cylinder 33. Therefore, whether or not to perform standby processing is determined based on the temperature of the engine 20 before combustion, and standby processing is performed particularly when it is determined that the engine is hot started. This eliminates the influence of the residual unburned gas that is likely to be affected when the engine is hot started, and allows the engine 20 to start smoothly.

[0076] Furthermore, if ignition fails during a low-temperature start, excess fuel may remain in the cylinder 33, which may lead to a so-called plug fouling state. Therefore, whether or not to perform standby processing is determined based on the temperature of the engine 20 before combustion, and standby processing is performed particularly when it is determined that a low-temperature start is being performed. As a result, when a low-temperature start is performed, the excess fuel is temporarily discharged, allowing the engine 20 to start smoothly.

[0077] Note that the standby process may be performed only when it is determined that the engine is in a hot start or a cold start. The period during which the standby process is performed (such as the number of revolutions of the crankshaft 40, the elapsed time, etc.) may be different when it is determined that the engine is in a hot start and when it is determined that the engine is in a cold start. Furthermore, in the case of a hot start or a cold start, the period during which the standby process is performed (which may be determined by the number of revolutions of the crankshaft 40, the elapsed time, etc.) may be different depending on the temperature of the engine 20 before combustion. For example, temperatures higher than room temperature may be divided into three stages, and the period during which the standby process is performed may be different so that the higher the temperature is, the longer the period for which the standby process is performed depending on each stage.

[0078] Furthermore, when executing the standby process, the control device 60 causes the ignition device 52 to perform an ignition operation. If ignition is performed during the standby process, there is a possibility that the engine 20 will be started promptly.

[0079] When the standby condition is not satisfied, the control device 60 may execute the startup combustion process without going through the standby process after determining the start of startup. This allows the engine 20 to be started quickly in a state where standby is not required.

[0080] If the standby condition is not satisfied, the control device 60 may execute a simulated standby process in which fuel injection is kept stopped for a period shorter than the standby process, and execute the start combustion process after the simulated standby process is completed. In this case, even if the standby condition is not satisfied, the start combustion process is executed after the simulated standby process is executed. Therefore, the variation in the time required to start the engine 20 can be suppressed depending on whether or not the standby process is executed.

[0081] Furthermore, the control device 60 executes standby processing at least during the period when the intake operation (see FIG. 5(a)) and the exhaust operation (see FIG. 5(d)) are performed. As a result, fresh outside air is introduced into the cylinder 33 and gas is exhausted from the cylinder 33, so that the amount of unburned gas remaining in the cylinder 33 is further reduced.

[0082] Furthermore, when executing the standby process, the control device 60 controls the intake air amount regulator 47V to increase the intake passage area compared to before the standby process. This increases the amount of intake air led to the cylinder 33. By introducing a large amount of fresh outside air, the amount of unburned gas remaining in the cylinder 33 can be further reduced.

[0083] The control device 60 determines the timing at which the exhaust operation ends based on the detection results of the rotation detection device 26, which detects the rotation of the crankshaft 40, so that the control device 60 can accurately estimate the timing at which the exhaust operation is completed, and fuel injection before the exhaust ends is suppressed.

[0084] In the above embodiment, the completion of the exhaust operation is determined based on the rotation speed of the crankshaft 40 after the crankshaft 40 starts to rotate, but the completion of the exhaust operation may be determined based on other criteria. For example, the time after the rotation of the crankshaft 40 is detected may be compared with a predetermined reference elapsed time, and if the reference elapsed time is exceeded, the exhaust operation may be determined to be completed. The reference elapsed time may be set to a time that is assumed to be appropriate for the exhaust operation to be performed after the crankshaft 40 starts to rotate.

[0085] The predetermined standby condition may be determined based on a condition other than the temperature of the engine 20. For example, the time elapsed since the last engine stop may be compared with a predetermined threshold time elapsed, and it may be determined that the standby condition is satisfied if the elapsed time does not exceed the predetermined threshold time. In addition, a condition that assumes that fuel remains in the intake port 47P and the cylinder 33 from various states of the engine 20 may be set as the standby condition. For example, the standby condition may be set by combining the temperature of each part of the engine 20, the time elapsed since the last engine stop, and the like. The standby condition may be set empirically, experimentally, or inferentially in consideration of the volume per cylinder 33, the displacement, the number of cylinders, the fuel injection capacity of the fuel injection valve 50, the fuel injection capacity relative to the volume of the cylinder 33, and the like.

[0086] The predetermined standby condition may be set as a condition that can be satisfied under all conditions, regardless of the temperature of the engine 20. In this case, if the start switch 22 is turned on, the standby process (exhaust process) is executed in all cases, regardless of the temperature of the engine 20. In this case, it is easy to align the timing at which the engine 20 starts after the start switch 22 is turned on.

[0087] The configurations described in the above embodiment and modifications can be combined as appropriate as long as they are not mutually inconsistent.

[0088] The present specification and drawings disclose the following aspects.

[0089] A first aspect is an engine comprising: an engine body having a cylinder, a piston that reciprocates within the cylinder, a crankshaft that rotates in conjunction with the reciprocating movement of the piston, and a valve mechanism that performs intake and exhaust operations into the cylinder in conjunction with the reciprocating movement of the piston; a fuel injection valve that injects fuel, an ignition device that ignites the fuel in the cylinder, and a control device that controls the fuel injection valve and the ignition device, and when a predetermined standby condition is satisfied, executes a standby process that maintains a state in which fuel injection is stopped from determining that a start has begun until it determines that an exhaust operation has been performed by the valve mechanism, and when the standby process is terminated, executes a startup combustion process that controls the fuel injection valve to inject fuel and controls the ignition device to ignite the fuel in the cylinder.

[0090] According to this engine, fuel injection is stopped during the standby process after the start of the engine. As a result, during the standby process, unburned gas remaining in the cylinder is discharged by the exhaust operation of the valve mechanism caused by the reciprocating movement of the piston. When the start combustion process is subsequently performed, fuel combustion is performed with the remaining unburned gas in the cylinder discharged. By discharging the unburned gas remaining before the engine start in this manner, the influence of the remaining unburned gas can be suppressed, and the variation in the mixture concentration in the combustion chamber at the time of engine start can be suppressed. This can prevent poor combustion due to the influence of the remaining unburned gas, for example, and prevent deterioration of startability.

[0091] In a second aspect, the engine according to the first aspect is configured such that the standby condition is set based on a temperature of the engine before combustion. In this case, the standby condition is set according to a temperature that affects a mixture concentration due to residual fuel in a cylinder, and the residual fuel is appropriately exhausted.

[0092] In a third aspect, in the engine according to the first or second aspect, the control device performs an ignition operation when executing the standby process. In this case, by allowing ignition in the standby state, it is possible to achieve a quick engine start.

[0093] In a fourth aspect, in the engine according to any one of the first to third aspects, the control device executes the start combustion process without going through the standby process after determining the start of the engine when the standby condition is not satisfied. In this case, the engine can be started quickly in a situation where standby is not required.

[0094] In a fifth aspect, in the engine according to any one of the first to fourth aspects, when the standby condition is not satisfied, the control device executes a simulated standby process in which fuel injection is kept stopped for a period shorter than the period during which the standby process is executed after determining the start start, and executes the start combustion process when the simulated standby process ends. This makes it possible to suppress variation in the time required for start-up depending on whether or not the standby process is executed.

[0095] A sixth aspect is the engine according to any one of the first to fifth aspects, wherein the control device executes the standby process at least during a period during which the intake operation and the exhaust operation are performed. In this case, the intake operation is performed during the standby process, thereby further reducing unburned gas remaining in the cylinder.

[0096] A seventh aspect is the engine according to any one of the first to sixth aspects, further including an intake amount adjustment device that adjusts the amount of intake air into the cylinder, and when executing the standby process, the control device increases an intake passage area compared to before the standby process, thereby increasing the amount of intake air led to the cylinder and further reducing unburned gas remaining in the cylinder.

[0097] An eighth aspect is the engine according to any one of the first to seventh aspects, further including a rotation detection device that detects the rotation of the crankshaft, and the control device determines the timing at which the exhaust operation ends based on the detection result of the rotation detection device. In this case, the control device can accurately estimate the timing at which the intake operation ends, and can suppress fuel injection before the exhaust ends.

[0098] A ninth aspect is an engine control device that controls a fuel injection valve and an ignition device in an engine, and executes: (a) a standby process that maintains a stopped state of fuel injection from when a predetermined standby condition is satisfied, determining that the start-up has begun, until it is determined that an exhaust operation has been performed by a valve mechanism; and (b) a startup combustion process that controls the fuel injection valve to inject fuel and controls the ignition device to ignite the fuel in the cylinder, when the standby process is terminated.

[0099] According to this engine control device, fuel injection is stopped during the standby process after the start of the engine. As a result, during the standby process, unburned gas remaining in the cylinder is discharged by the exhaust operation of the valve mechanism caused by the reciprocating movement of the piston. When the start combustion process is subsequently performed, fuel combustion is performed with the remaining unburned gas in the cylinder discharged. By discharging the unburned gas remaining before the start in this manner, the influence of the remaining unburned gas can be suppressed, and the variation in the mixture concentration in the combustion chamber at the start of the engine can be suppressed. This can prevent, for example, poor combustion due to the influence of the remaining unburned gas, and prevent a decrease in startability.

[0100] A tenth aspect is an engine control method for controlling a fuel injection valve and an ignition device in an engine, comprising: (a) a process for maintaining a stopped state of fuel injection from when a predetermined standby condition is satisfied, determining that the start of starting has begun, until when it is determined that an exhaust operation has been performed by a valve mechanism; and (b) a process for controlling the fuel injection valve to inject fuel and controlling the ignition device to ignite the fuel in the cylinder, when the process (a) is completed.

[0101] According to this engine control method, fuel injection is stopped during the standby process after the start of the engine. As a result, during the standby process, unburned gas remaining in the cylinder is discharged by the exhaust operation of the valve mechanism caused by the reciprocating movement of the piston. When the start combustion process is subsequently performed, fuel combustion is performed with the remaining unburned gas in the cylinder discharged. By discharging the unburned gas remaining before the engine start in this manner, the influence of the remaining unburned gas can be suppressed, and the variation in the mixture concentration in the combustion chamber at the time of engine start can be suppressed. This can prevent poor combustion due to the influence of the remaining unburned gas, for example, and prevent a decrease in startability.

[0102] The above description is illustrative in all respects, and the present invention is not limited thereto. It is understood that countless variations not illustrated can be assumed without departing from the scope of the present invention. [Explanation of symbols]

[0103] 20 Engine 26 Rotation detection device 27 Water temperature sensor 28 Oil temperature sensor 33 cylinders 34 Piston 40 Crankshaft 46 Valve train 47 Intake valve 47V air supply adjustment device 48 Exhaust valve 50 Fuel Injector 52 Ignition system 60 Control device

Claims

1. an engine body having a cylinder, a piston that reciprocates in the cylinder, a crankshaft that rotates in conjunction with the reciprocating movement of the piston, and a valve mechanism that performs an intake operation and an exhaust operation into the cylinder in conjunction with the reciprocating movement of the piston; A fuel injection valve that injects fuel; an ignition device that ignites fuel in the cylinder; a control device for controlling the fuel injection valve and the ignition device, which, when a predetermined standby condition is satisfied, executes a standby process for maintaining a state in which fuel injection is stopped from when it is determined that a start has begun until it is determined that an exhaust operation has been performed by the valve mechanism, and, when it ends the standby process, executes a startup combustion process for controlling the fuel injection valve to inject fuel and controlling the ignition device to ignite the fuel in the cylinder; Equipped with The control device includes: When the standby condition is not satisfied, a simulated standby process is executed to maintain a state in which fuel injection is stopped for a period that exceeds an ignition timing that is set in synchronization with a rotation angle of the crankshaft after the start of the engine is determined and is shorter than a period in which the standby process is executed; When the simulated standby process is completed, the startup combustion process is executed. The standby condition is set based on a temperature associated with the engine before combustion, and is a condition that is satisfied when the temperature associated with the engine before combustion is within a hot start temperature range.

2. an engine body having a cylinder, a piston that reciprocates in the cylinder, a crankshaft that rotates in conjunction with the reciprocating movement of the piston, and a valve mechanism that performs an intake operation and an exhaust operation into the cylinder in conjunction with the reciprocating movement of the piston; A fuel injection valve that injects fuel; an ignition device that ignites fuel in the cylinder; a control device for controlling the fuel injection valve and the ignition device, which, when a predetermined standby condition is satisfied, executes a standby process for maintaining a state in which fuel injection is stopped from when it is determined that a start has begun until it is determined that an exhaust operation has been performed by the valve mechanism, and, when it ends the standby process, executes a startup combustion process for controlling the fuel injection valve to inject fuel and controlling the ignition device to ignite the fuel in the cylinder; Equipped with The control device includes: When the standby condition is not satisfied, a simulated standby process is executed to maintain a state in which fuel injection is stopped for a period that exceeds an ignition timing that is set in synchronization with a rotation angle of the crankshaft after the start of the engine is determined and is shorter than a period in which the standby process is executed; When the simulated standby process is completed, the startup combustion process is executed. The control device causes an ignition operation to be performed when the standby process is performed, The standby condition is set based on a temperature associated with the engine before combustion, and is a condition that is satisfied when the temperature associated with the engine before combustion is either within a hot start temperature range or within a cold start range in which the fuel injection amount and the intake air amount are adjusted compared to a normal temperature state.

3. 3. An engine according to claim 1 or claim 2, The control device executes the standby process at least during a period during which the intake operation and the exhaust operation are performed.

4. An engine according to any one of claims 1 to 3, The engine further includes an intake amount adjusting device for adjusting the amount of intake air into the cylinder, When executing the standby process, the control device increases an intake passage area compared to before the standby process.

5. An engine according to any one of claims 1 to 4, Further comprising a rotation detection device for detecting the rotation of the crankshaft, The control device determines a timing to end the exhaust operation based on a detection result of the rotation detection device.

6. An engine control device that controls a fuel injection valve and an ignition device in an engine, (a) a standby process for maintaining a state in which fuel injection is stopped after it is determined that the engine has started and until it is determined that an exhaust operation by the valve mechanism has been performed, when a predetermined standby condition is satisfied; (b) a start combustion process for controlling the fuel injection valve to inject fuel and controlling the ignition device to ignite the fuel in the cylinder when the standby process is completed; Run Furthermore, when the standby condition is not satisfied, a simulated standby process is executed in which fuel injection is kept stopped for a period that exceeds an ignition timing set in synchronization with a rotation angle of the crankshaft after the start of the start is determined and is shorter than a period during which the standby process is executed, and when the simulated standby process is terminated, the startup combustion process is executed. Here, the standby condition is set based on a temperature associated with the engine before combustion, and is a condition that is satisfied when the temperature associated with the engine before combustion is within a hot start temperature range.

7. A method for controlling a fuel injection valve and an ignition device in an engine, comprising: (a) when a predetermined standby condition is satisfied, a process of maintaining a state in which fuel injection is stopped from when it is determined that the engine has started to start until it is determined that an exhaust operation by the valve train has been performed; (b) when the process (a) is completed, a process of controlling the fuel injection valve to inject fuel and controlling the ignition device to ignite the fuel in the cylinder; Equipped with Furthermore, if the standby condition is not satisfied, in the process (a), a process (c) is executed to maintain the fuel injection stopped state for a period that exceeds an ignition timing set in synchronization with a rotation angle of the crankshaft after the start of the start is determined and is shorter than a period for maintaining the fuel injection stopped state, and when the process (c) is completed, a startup combustion process is executed; Here, the standby condition is set based on a temperature associated with the engine before combustion, and is a condition that is satisfied when the temperature associated with the engine before combustion is within a hot start temperature range.

Images