Internal combustion engine starting system
The starting system for internal combustion engines optimizes the use of the starting motor by controlling its rotational speed during restarts, ensuring smooth engine operation and reducing power consumption, addressing the issue of increased fuel consumption in existing systems.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HONDA MOTOR CO LTD
- Filing Date
- 2025-11-14
- Publication Date
- 2026-06-11
Smart Images
Figure JP2025039968_11062026_PF_FP_ABST
Abstract
Description
Starting System for Internal Combustion Engine 【0001】 The present invention relates to a starting system for an internal combustion engine. 【0002】 Conventionally, a technique for starting an internal combustion engine using a starting motor that rotates a crankshaft is known (see, for example, Patent Document 1). Patent Document 1 discloses a technique for smoothly restarting from an idling stop by continuing cranking with a starting motor at a rotational speed at which a decomp operates during an idling stop. 【0003】 Japanese Patent Application Laid-Open No. 2018-016269 【0004】 However, in the technique described in Patent Document 1, since motoring is always performed during the idling stop period, power consumption increases and the load on the battery increases. Therefore, the technique described in Patent Document 1 has a problem that there is concern about the influence on fuel consumption. The present invention has been made in view of the above circumstances, and an object thereof is to provide a starting system for an internal combustion engine that can easily restart smoothly while suppressing the use of a starting motor and can easily improve fuel consumption. 【0005】 This specification includes all the contents of Japanese Patent Application No. 2024-213975 filed on December 6, 2024. A starting system for an internal combustion engine includes an internal combustion engine, a starting motor that rotates a crankshaft of the internal combustion engine, a control device that controls the internal combustion engine and the starting motor, and a decomp mechanism that reduces the compression pressure in a cylinder of the internal combustion engine. In the restart from the idling stop state of the internal combustion engine, the starting motor is rotated with a predetermined first rotational speed that does not exceed the crank rotational speed at which the operation of the decomp mechanism stops as a target value, and when the crank rotational speed at a predetermined crank phase in the combustion stroke does not exceed a predetermined threshold value, the target value of the starting motor is not changed. 【0006】 It is possible to provide a starting system for an internal combustion engine that can easily restart smoothly while suppressing the use of a starting motor and can easily improve fuel consumption. 【0007】 Figure 1 is a side view of a saddle-type vehicle according to an embodiment of the present invention. Figure 2 is a cross-sectional view showing the area around the engine's exhaust port. Figure 3 is a block diagram showing the control device provided in the saddle-type vehicle along with its surrounding configuration. Figure 4 is a flowchart showing an example of the detection acquisition process of the control device. Figure 5 is a flowchart showing an example of the ISG control process during normal startup of the control device. Figure 6 is a flowchart showing an example of the idling stop control process of the control device. Figure 7 is a flowchart showing an example of the ISG control process during restart of the control device. Figure 8 is a diagram showing the ISG timing chart when restarting from a crank speed Ne of 0 and the relationship between the ISG timing chart and the time change of crank speed accompanying the operation of the ISG. 【0008】 Embodiments of the present invention will be described below with reference to the drawings. In the description, directions such as front, back, left, right, and up and down refer to directions relative to the vehicle body unless otherwise specified. In each figure, the symbol FR indicates the front of the vehicle body, the symbol UP indicates the top of the vehicle body, and the symbol LH indicates the left side of the vehicle body. 【0009】 [Embodiment] Figure 1 is a side view of a saddle-type vehicle 10 according to an embodiment of the present invention. The saddle-type vehicle 10 is a vehicle comprising a body frame 11, a power unit 12 supported by the body frame 11, a front fork 14 that supports the front wheel 13 in a steerable manner, a swing arm 16 that supports the rear wheel 15, and a seat 17 for the rider. The saddle-type vehicle 10 is a vehicle in which the rider sits by straddling the seat 17. The seat 17 is provided above the rear of the body frame 11. 【0010】 The vehicle frame 11 comprises a head pipe 18 located at the front end of the vehicle frame 11, a front frame 19 located behind the head pipe 18, and a rear frame 20 located behind the front frame 19. The front end of the front frame 19 is connected to the head pipe 18. The seat 17 is supported by the rear frame 20. 【0011】The front fork 14 is supported by a head pipe 18 so that it can be steered left and right. The front wheel 13 is supported by an axle 13a provided at the lower end of the front fork 14. The steering handle 21, which is held by the rider, is attached to the upper end of the front fork 14. 【0012】 The swingarm 16 is supported by a pivot shaft 22 which is supported by the vehicle frame 11. The pivot shaft 22 is an axis that extends horizontally in the vehicle width direction. The pivot shaft 22 is inserted through the front end of the swingarm 16. The swingarm 16 swings up and down around the pivot shaft 22. The rear wheel 15 is supported by an axle 15a provided at the rear end of the swingarm 16. 【0013】 The power unit 12 is positioned between the front wheel 13 and the rear wheel 15 and is supported by the vehicle frame 11. The power unit 12 is an internal combustion engine. The power unit 12 comprises a crankcase 23 and a cylinder section 24 that houses a reciprocating piston. An exhaust device 25 is connected to the exhaust port of the cylinder section 24. The output of the power unit 12 is transmitted to the rear wheel 15 by a drive force transmission member that connects the power unit 12 to the rear wheel 15. 【0014】 The saddle-type vehicle 10 also includes a front fender 26 that covers the front wheel 13 from above, a rear fender 27 that covers the rear wheel 15 from above, a step 28 on which the rider places their feet, and a fuel tank 29 that stores the fuel used by the power unit 12. The front fender 26 is attached to the front fork 14. The rear fender 27 and step 28 are located below the seat 17. The fuel tank 29 is supported by the vehicle frame 11. 【0015】A throttle grip 31 (see Figure 3) is rotatably mounted on the right side of the handle 21. The throttle grip 31 is operated by the driver (occupant). The throttle grip 31 is a throttle control device for adjusting the opening degree of the throttle valve 32 (see Figure 3). In this embodiment, the throttle grip 31 and the throttle valve 32 are physically connected by a mechanical wire. However, a throttle-by-wire system may be adopted in which the throttle grip 31 and the throttle valve 32 are not physically connected, and the throttle is controlled by converting the driver's throttle operation (accelerator operation) into an electrical signal. 【0016】 The saddle-type vehicle 10 of this embodiment is a scooter-type saddle-type vehicle equipped with a seat 17 on which the driver sits by straddling it. The power unit 12 of the saddle-type vehicle 10 of this embodiment is a unit swing power unit supported at the rear of the vehicle frame 11. The power unit 12 has a crankcase 23, a cylinder section 24, and a swing arm 16 integrated into one unit. The crankcase 23 and the cylinder section 24 constitute the engine (internal combustion engine) 40. 【0017】 In this embodiment, the engine 40 is a single-cylinder, four-stroke, SOHC engine. The engine 40 is configured as a horizontal engine in which the cylinder section (cylinder) 24 protrudes horizontally forward from the crankcase 23. The cylinder section 24 comprises, in order from the crankcase 23 side, a cylinder block 37, a cylinder head 38, and a cylinder head cover 39. The engine 40 is provided with a throttle valve 32 (see Figure 3) for adjusting the intake air volume, a fuel injector 33 (see Figure 3) for injecting fuel, and an ignition device 34 (see Figure 3) for igniting the air-fuel mixture in the combustion chamber of the cylinder section 24. 【0018】In the power unit 12 of this embodiment, a continuously variable transmission 41 (see Figure 3) and a centrifugal clutch 42 (see Figure 3) are provided in the drive transmission path between the engine 40 and the rear wheel 15. The continuously variable transmission 41 of this embodiment is a transmission that combines a belt and two variable diameter pulleys. The continuously variable transmission 41 receives driving force input from the crankshaft 23a (see Figure 1) that extends from the crankcase 23 in the left-right direction and outputs the driving force to the centrifugal clutch 42. The centrifugal clutch 42 transmits and disconnects the driving force output from the continuously variable transmission 41 to the rear wheel 15. The centrifugal clutch 42 enters a transmission state due to the action of centrifugal force when the rotational speed of the output shaft of the continuously variable transmission 41 increases, and enters a transmission disconnection state when the rotational speed of the output shaft of the continuously variable transmission 41 is low. 【0019】 In the power unit 12 of this embodiment, an ISG (Integrated Starter Generator) 43, which is an example of a starting motor, is positioned on the side opposite the continuously variable transmission 41 in the vehicle width direction. The ISG 43 is connected to the crankshaft 23a. The ISG 43 functions as a starter to start the engine 40, and also functions as an alternator that is driven by the engine 40 to generate electricity. 【0020】 Figure 2 is a cross-sectional view showing the area around the exhaust port 24a of the engine 40. The exhaust port 24a of the cylinder head 38 is closed by an exhaust valve 51, which can be opened and closed. The shaft portion 51a of the exhaust valve 51 is slidably supported on the cylinder head 38. A spring retainer 51b is supported on the outer end of the shaft portion 51a of the exhaust valve 51. A valve spring 52 is positioned between the spring retainer 51b and the spring seat 24b of the cylinder head 38. The valve spring 52 biases the spring retainer 51b and the spring seat 24b to separate from each other. The valve spring 52 biases the exhaust valve 51 to a position that closes the exhaust port 24a. 【0021】One end 53b of the rocker arm 53 abuts against the shaft 51a of the exhaust valve 51. The rocker arm 53 is supported so as to be able to swing with its longitudinal midpoint as the pivot point 53a. The one end 53b of the rocker arm 53 is biased by a valve spring 52 via the exhaust valve 51. 【0022】 The other end 53c of the rocker arm 53 is in contact with the camshaft 54. More specifically, the other end 53c of the rocker arm 53 is in contact with the cam profile surface 54a of the camshaft 54. Therefore, when the camshaft 54 rotates, the other end 53c of the rocker arm 53 is maintained in contact with the cam profile surface 54a by the biasing force of the valve spring 52. As a result, the rocker arm 53 swings against the biasing force of the valve spring 52 according to the cam shape of the cam profile surface 54a, the exhaust valve 51 is opened and closed, and the combustion chamber and the exhaust port 24a are connected. 【0023】 Here, the camshaft 54 rotates together with the crankshaft 23a via a power transmission member (not shown) stretched between it and the crankshaft 23a, driving an intake valve and an exhaust valve 51 (not shown) to perform intake and exhaust according to a four-cycle process. Therefore, the exhaust valve 51 is opened and closed as appropriate according to the intake stroke, compression stroke, combustion stroke, and exhaust stroke. 【0024】 In this embodiment, a decompression mechanism 60 is provided that opens the exhaust valve 51 when the engine 40 is started to reduce the reaction force during the compression stroke. The decompression mechanism 60 in this embodiment is a centrifugal automatic decompression mechanism. 【0025】 The decompression mechanism 60 is provided on the camshaft 54. The decompression mechanism 60 has a decompression arm 61 that is positioned to cover the circumference of the camshaft 54. The decompression arm 61 is pivotably supported by a pivot shaft 61a in the middle of its longitudinal direction. A return spring 62 is positioned between one end 61b of the decompression arm 61 and the camshaft 54 to bias the decompression arm 61. The return spring 62 biases one end 61b of the decompression arm away from the camshaft 54. As a result, the other end 61c of the decompression arm 61 is biased toward the camshaft 54. 【0026】 An operating pin 61d is supported at the other end 61c of the decompression arm 61. A decompression cam 63 engages with the operating pin 61d. 【0027】 The decompression cam 63 is approximately semicircular in shape. The decompression cam 63 is rotatably supported with respect to the pivot center 63a. The decompression cam 63 has a guide groove 63b that engages with the operating pin 61d. The decompression cam 63 rotates with respect to the pivot center 63a as the operating pin 61d moves relative to the decompression cam 63 within the guide groove 63b, guided by the operating pin 61d. 【0028】 The decompression mechanism 60 configured in this way enters a decompression state when the engine 40 is started and the rotational speed of the rotating camshaft 54 is below a predetermined rotational speed. That is, the centrifugal force generated on the decompression arm 61 is smaller than the biasing force of the return spring 62, and the amount of oscillation of the decompression arm 61 is small. At this time, the decompression cam 63 is in a state where it protrudes outward from the cam profile surface 54a. Therefore, regardless of the shape of the cam profile surface 54a, the rocker arm 53 contacts the protruding decompression cam 63 and is pushed up and oscillates. As a result, even when the engine 40 is in the compression stroke, the exhaust valve 51 is opened, and the function of reducing the reaction force during the compression stroke of the engine 40 is activated, improving the starting performance of the engine 40. 【0029】 On the other hand, when the rotational speed of the engine 40 increases and the rotational speed of the camshaft 54 exceeds a predetermined rotational speed, the decompression arm 61 swings away from the camshaft 54 due to centrifugal force, against the biasing force of the return spring 62. As a result, the operating pin 61d moves within the guide groove 63b of the decompression cam 63, causing the decompression cam 63 to rotate around the pivot center 63a, and the rocker arm 53 no longer contacts the decompression cam 63. Therefore, the rocker arm 53 operates in accordance with the shape of the outer circumferential surface of the original cam profile surface 54a. In other words, the decompression mechanism 60 becomes non-operating. 【0030】Thus, the operating state of the decompression mechanism 60 changes according to the rotational speed of the engine 40. The upper limit rotational speed of the engine 40 at which the decompression mechanism 60 reliably reduces the reaction force during the compression stroke of the engine 40 is called the decompression operating speed. The decompression operating speed is, for example, 900 rpm. 【0031】 Figure 3 is a block diagram showing the control device 100 of the saddle-type vehicle 10 along with its surrounding configuration. The saddle-type vehicle 10 is equipped with the control device 100. The control device 100 is an ECU (Electronic Control Unit). The control device 100 is a computer device that includes a control unit 110, a memory unit 120, a communication interface circuit 130, and the like. 【0032】 The control unit 110 is composed of a CPU (Central Processing Unit) or a microcontroller, and controls each part of the control device 100 by executing a program. Alternatively, the control unit 110 may be a System-on-a-chip (SoC) that integrates the control unit 110 and the storage unit 120. 【0033】 The storage unit 120 includes memory such as ROM (Read Only Memory) and RAM (Random Access Memory). The storage unit 120 stores the control program executed by the control unit 110. The storage unit 120 also stores data and processing result data processed by the control unit 110 when the computer program is executed. 【0034】 The control device 100 is connected to signal input elements such as a throttle operation sensor 141, a crank angle sensor 142, a vehicle speed sensor 143, and a starter switch 144. 【0035】 The throttle operation sensor 141 detects the driver's operation on the throttle grip 31. The throttle operation sensor 141 may also be a sensor provided on the throttle grip 31 that detects the amount of rotation of the throttle grip 31. Alternatively, the throttle operation sensor may be a sensor provided on the throttle valve 32 that detects the throttle opening. 【0036】The crank angle sensor 142 detects the amount of rotation of the crankshaft 23a of the engine 40. Based on the detection result of the crank angle sensor 142, the crank phase of the crankshaft 23a and the rotational speed of the crankshaft 23a, i.e., the crank rotational speed Ne, can be determined. Here, the engine 40 is a four-stroke engine, and the crankshaft 23a rotates twice during its four strokes, so the crank phase takes a value in the range of 0 to 720 degrees, and the compression top dead center is 0 degrees. The unit of the crank rotational speed Ne is rpm. 【0037】 The vehicle speed sensor 143 is a sensor that detects the vehicle speed of the saddle-type vehicle 10, and is, for example, a sensor that detects the amount of rotation of the front wheel 13. 【0038】 The starter switch 144 is a switch used by the driver to instruct the starter to start the engine 40. When the power switch (not shown) is ON, the control device 100 accepts the starter switch 144 being turned ON by the driver as a start operation and starts the engine 40. The starter switch 144 may be provided together with the power switch, in which case the power switch may have selectable positions such as ACC ON (power ON), Ignition ON (start operation), and OFF (power OFF). 【0039】 The control device 100 is connected to signal output elements such as the ISG 43, fuel injection device 33, ignition device 34, and alarm device 151. 【0040】 The alarm device 151 is a device that notifies the driver of various information about the saddle-type vehicle 10. The alarm device 151 comprises at least one of a display device and an audio output device. Specifically, the alarm device 151 consists of a meter panel, indicators, speakers, etc. The alarm device 151 notifies the driver of an abnormality by display and at least one of audio. The alarm device 151 is controlled by the control unit 110. 【0041】The control device 100 realizes various functional configurations by the control unit 110 executing the control program stored in the storage unit 120. The control device 100 of the present embodiment controls the engine 40, the ISG 43, etc. based on signals from the throttle operation sensor 141, the crank angle sensor 142, the vehicle speed sensor 143, the start switch 144, etc. 【0042】 Figure 4 is a flowchart showing an example of the detection acquisition process of the control device 100. The detection acquisition process shown in Figure 4 is started when, for example, ignition on or engine start (power unit start) of the straddle-type vehicle 10 is detected, and is repeatedly executed at a predetermined cycle (for example, several msec). In this process, various state data are updated based on the detection results of the sensors 141 to 144. 【0043】 In step ST11, the control device 100 acquires the detection results of the sensors 141 to 144. 【0044】 In step ST12, the control device 100 updates each state data stored in the storage unit 120 based on the detection results of the sensors 141 to 144. Examples of the types of state data to be updated include the throttle state (for example, closed state or open state) based on the detection result of the throttle operation sensor 141, the crank angle and the crank rotation speed Ne based on the detection result of the crank angle sensor 142, the vehicle speed based on the detection result of the vehicle speed sensor 143, and the start operation of the driver based on the detection result of the start switch 144. 【0045】 In the present embodiment, in the combustion stroke, the crank rotation speed Ne at the crank phase where the angular velocity of the crankshaft 23a is maximum is updated. Specifically, it is updated every time the crank rotation speed Ne at a crank phase of 150 degrees is acquired. 【0046】 Figure 5 is a flowchart showing an example of the control process of the ISG 43 during normal start of the control device 100. The control process of the ISG 43 during normal start shown in Figure 5 is started when the power supply of the straddle-type vehicle 10 is turned on. 【0047】In step ST31, the control device 100 determines whether the status switch 144 has been turned on. When the control device 100 determines that the status switch 144 has been turned on (step ST31; YES), the process proceeds to step ST32. When the control device 100 determines that the status switch 144 has not been turned on, that is, remains OFF (step ST31; NO), the process of step ST31 is repeated. 【0048】 In step ST32, the control device 100 sets the operation target value of the ISG43 to the initial rotation speed N0. The initial rotation speed N0 is set in advance. The initial rotation speed N0 is set to a crank rotation speed Ne that is greater than the decompression operation rotation speed. Specifically, the initial rotation speed N0 is set to, for example, 1000 rpm. 【0049】 In step ST33, the control device 100 starts energizing the ISG43 and controls the ISG43 so as to achieve the operation target value. In step ST34, the control device 100 acquires the crank rotation speed Ne in the combustion stroke. In the present embodiment, the control device 100 acquires the crank rotation speed Ne when the crank phase is 150 degrees from the data stored in the storage unit 120. In the subsequent processes, when the control device 100 acquires the crank rotation speed Ne in the combustion stroke, similarly, the crank rotation speed Ne when the crank phase is 150 degrees is acquired. 【0050】 In step ST35, the control device 100 determines whether the crank rotation speed Ne has reached the initial rotation speed N0. When the control device 100 determines that the crank rotation speed Ne has reached the initial rotation speed N0 (step ST35; YES), the process proceeds to step ST36. When the control device 100 determines that the crank rotation speed Ne has not reached the initial rotation speed N0 (step ST35; NO), the process returns to step ST34. 【0051】In step ST36, the control device 100 terminates the power supply to the ISG 43. In step ST37, the control device 100 switches the ISG 43 to power generation mode, that is, it uses the ISG 43 as a generator. When the control device 100 finishes the process in step ST37, it terminates the control process of the ISG 43 during normal startup as shown in Figure 5. 【0052】 Figure 6 is a flowchart showing an example of the idle stop control process of the control device 100. The idle stop control process shown in Figure 6 is started, for example, when the ignition of the saddle-type vehicle 10 is turned on or the engine starts (power unit starts), and is repeatedly executed at a predetermined cycle (for example, several msec). 【0053】 In step ST51, the control device 100 determines whether the IS (idling stop) flag is ON or OFF. Here, the IS flag is a flag that indicates whether or not idling stop is in operation. The IS flag is switched ON when idling stop is in operation and OFF when idling stop is not in operation. The IS flag is a flag in which ON and OFF information is stored using a predetermined storage area in the storage unit 120 of the control device 100. 【0054】 If the control device 100 determines that the IS flag is ON (step ST51; YES), it proceeds to step ST52. Therefore, the process following step ST52 is the process during the idle stop of the engine 40. If the control device 100 determines that the IS flag is not ON (step ST51; NO), it proceeds to step ST56. 【0055】 In step ST52, the control device 100 determines whether or not the restart condition has been met. Here, the restart condition can be, for example, that the driver has opened the throttle valve 32 (rotated the throttle grip 31). Therefore, when the control device 100 determines whether or not the restart condition has been met, it can determine whether or not the throttle valve 32 has been opened. 【0056】If the control device 100 determines that the restart condition has been met (step ST52; YES), it proceeds to step ST53. If the control device 100 determines that the restart condition has not been met (step ST52; NO), it terminates the idle stop control process shown in Figure 6. 【0057】 In step ST53, the control device 100 performs restart control. Specifically, in step ST53, the control device 100 calls the subroutine shown in Figure 7 to drive the ISG 43 as a starter and rotate the crankshaft 23a in the forward direction. The control device 100 also drives the engine 40 by supplying fuel with the fuel injector 33 and igniting with the ignition device 34. When the processing in step ST53 is completed, the control device 100 terminates the idle stop control processing shown in Figure 6. 【0058】 In step ST56, the control device 100 determines whether the IS condition has been met. Here, the IS condition can be, for example, that the vehicle speed is less than or equal to a specified vehicle speed (e.g., 3 km / h) and that the throttle valve 32 has been closed for a specified time (e.g., 3 seconds). Other conditions may include that the headlights are off, that the driver has previously authorized the execution of idle stop control (by providing an idle stop switch and having the driver turn it ON), the temperature of the engine oil and coolant, and the health of the battery voltage. The determination of whether the IS condition has been met is made based on the state data stored in the memory unit 120. 【0059】 Here, the IS condition is a condition that can be met while the saddle-type vehicle 10 is in motion, and does not require the saddle-type vehicle 10 to stop (such as the vehicle speed remaining at 0 for a certain period of time). As a result, the engine 40 automatically stops while the saddle-type vehicle 10 is decelerating and coming to a stop, which improves fuel efficiency compared to the case where the stopping of the saddle-type vehicle 10 is a requirement. 【0060】If the control device 100 determines that the IS condition is met (step ST56; YES), it proceeds to step ST57. If the control device 100 determines that the IS condition is not met (step ST56; NO), it terminates the idling stop control process shown in Figure 6. 【0061】 In step ST57, the control device 100 performs automatic stop control to automatically stop the engine 40. The control device 100 can, for example, shut off the fuel supply by the fuel injector 33 by performing automatic stop control. Alternatively, the control device 100 can, for example, stop ignition by the ignition device 34 by performing automatic stop control. 【0062】 In step ST37, the control device 100 switches the IS flag to OFF. When the control device 100 finishes processing in step ST37, it terminates the idle stop control process shown in Figure 6. 【0063】 Figure 7 is a flowchart showing an example of the control process of the ISG 43 when the control device 100 is restarted. The control process of the ISG 43 during restart shown in Figure 7 is started by being called in step ST53 of the idling stop process shown in Figure 6. 【0064】 In step ST71, it is determined whether the crankshaft 23a is in a stopped state. In this embodiment, the crankshaft 23a is determined to be in a stopped state if the crank rotation speed Ne is 300 rpm or less. Therefore, in this embodiment, in step ST71, the control device 100 determines whether the crank rotation speed Ne is 300 rpm or less. If the control device 100 determines that the crankshaft 23a is in a stopped state (step ST71; YES), it proceeds to the process in step ST72. If the control device 100 determines that the crankshaft 23a is not in a stopped state (step ST71; NO), it proceeds to the process in step ST91. 【0065】In step ST72, the control device 100 sets the operating target value of the ISG 43 to a first rotational speed Ne1 (see Figure 8). The first rotational speed Ne1 is preset. The first rotational speed Ne1 is set based on the crank rotational speed Ne at which the decompression mechanism 60 operates. Specifically, the crank rotational speed Ne at which the decompression mechanism 60 operates is 900 rpm or less. For example, the first rotational speed Ne1 is set to 750 rpm. 【0066】 In step ST73, the control device 100 starts energizing the ISG 43 and rotates the ISG 43 to reach the target operating value. In step ST74, the control device 100 obtains the crank rotation speed Ne during the combustion stroke. 【0067】 In step ST75, the control device 100 determines whether the crank rotation speed Ne is less than or equal to a predetermined threshold TH0 (see Figure 8). In other words, in step ST75, the control device 100 determines whether the crank rotation speed Ne does not exceed a predetermined threshold TH0. Here, the predetermined threshold TH0 is set to be greater than the first rotation speed Ne1 and less than or equal to the decompression rotation speed. In this embodiment, the threshold TH0 is 850 rpm. 【0068】 If the control device 100 determines that the crank rotation speed Ne is less than or equal to the threshold TH0 (step ST75; YES), it proceeds to the process in step ST76. If the control device 100 determines that the crank rotation speed Ne is not less than or equal to a predetermined threshold TH0, that is, that the crank rotation speed Ne exceeds a predetermined threshold TH0 (step ST75; NO), it proceeds to the process in step 91. 【0069】 In step ST77, the control device 100 determines whether a predetermined time has elapsed since the ISG 43 was energized. The predetermined time is, for example, 20 seconds. This allows it to determine whether or not the startup has failed for a predetermined period of time or longer. 【0070】If the control device 100 determines that a predetermined time has elapsed (step ST77; YES), it proceeds to step ST78. If the control device 100 determines that a predetermined time has not elapsed (step ST77; NO), it returns to step ST74. 【0071】 In step ST78, the control device 100 controls the alarm device 151 to notify of the abnormality. Specifically, the control device 100 causes the IS indicator of the alarm device 151 to flash rapidly. Alternatively, an image of the abnormality may be displayed on the meter panel of the alarm device 151. In addition, the driver can be more easily alerted to the abnormality by sounding an audible alarm through a speaker. 【0072】 In step ST79, the control device 100 stops the power supply to the ISG43. After completing the process in step ST79, the control device 100 returns to the idling stop control process shown in Figure 6. 【0073】 In step ST91, the control device 100 sets the operating target value of the ISG43 to a second rotational speed Ne2 (see Figure 8). The second rotational speed Ne2 is preset. The second rotational speed Ne2 is set to be higher than the decompression operating speed and lower than the idling rotational speed NeI (see Figure 8). Specifically, the second rotational speed Ne2 is, for example, 1300 rpm. The idling rotational speed NeI is, for example, 1600 rpm. 【0074】 In step ST92, the control device 100 obtains the crank rotation speed Ne during the combustion stroke. 【0075】 In step ST93, the control device 100 determines whether the crank speed Ne is equal to or greater than the third rotational speed Ne3 (see Figure 8). In other words, in step ST93, the control device 100 determines whether the crank speed Ne has reached the third rotational speed Ne3. The third rotational speed Ne3 is preset. The third rotational speed Ne3 is set to a value that allows the device to determine that the restart is complete. For example, the third rotational speed Ne3 is 1800 rpm. 【0076】If the control device 100 determines that the crank rotation speed Ne is equal to or greater than the third rotation speed Ne3 (step ST93; YES), it proceeds to step ST94. If the control device 100 determines that the crank rotation speed Ne is not equal to or greater than the third rotation speed Ne3, that is, that the crank rotation speed Ne has not reached the third rotation speed Ne3 (step ST93; YES), it returns to step ST92. 【0077】 In step ST94, the control device 100 stops the power supply to the ISG 43. In step ST95, the control device 100 switches the ISG 43 to power generation mode. In step ST96, the control device 100 switches the IS flag to OFF. After completing the process in step 96, the control device 100 returns to the idling stop control process shown in Figure 6. 【0078】 Figure 8 shows the timing chart of the ISG 43 when the crank speed Ne restarts from 0, and the relationship between this chart and the time change of the crank speed Ne associated with the operation of the ISG 43. The lower part of Figure 8 shows the timing chart of the ISG 43, and the upper part of Figure 8 shows the time change of the crank speed Ne. In the lower part of Figure 8, the horizontal axis is the elapsed time T, and the vertical axis shows the ON and OFF states, indicating the energized and de-energized states of the ISG 43. In the upper part of Figure 8, the horizontal axis is the elapsed time T, and the vertical axis is the crank speed Ne. In Figure 8, the solid line shows the desired combustion pattern, and the dashed line shows the combustion pattern in which a combustion defect deviates from the design. 【0079】 As shown in Figure 8, when the IS condition is met and the restart condition is met, the restart control of the ISG 43 is started (steps ST51 to ST53 in Figure 6, and steps ST71 to ST96 in Figure 7). That is, the target operating value of the ISG 43 is set to the first rotational speed Ne1, and the ISG 43 is energized (steps ST72 to ST73 in Figure 7). At this time, as shown in Figure 8, if the restart condition is met during period A1 when the crank rotational speed Ne is 0, the crank rotational speed Ne of the crankshaft 23a gradually increases from 0 in accordance with the operation of the ISG 43. 【0080】In this case, the fuel injection system 33 and the ignition system 34 are also controlled, so generally a crank speed Ne higher than the crank speed Ne which is the target value for operation of the ISG 43 can be obtained. In other words, the ISG 43 functions as a device that assists the rotation of the crankshaft 23a. 【0081】 In this embodiment, when it is determined that the crank rotation speed Ne has reached a threshold TH0 that is higher than the first rotation speed Ne1, the second rotation speed Ne2 is set as the operating target value for the ISG 43 (steps ST75 to ST91 in Figure 7), and the ISG 43 operates toward the second rotation speed Ne2 (step ST92 in Figure 7). 【0082】 In the engine 40, the crank speed Ne decreases during the compression stroke as the piston moves towards top dead center, and then increases sharply during the combustion stroke as the piston moves towards bottom dead center. That is, if the initial combustion is successful, the crank speed Ne exceeds the threshold TH0, and if the crank speed Ne during the compression stroke exceeds the third rotational speed Ne3, the ISG 43 is turned OFF as shown in time Tb. Then, the fuel injection system 33 and ignition system 34 are controlled, and the crank speed Ne increases. 【0083】 On the other hand, if combustion is insufficient at the initial combustion, the crank speed Ne will not increase rapidly. In this case, if the crank speed Ne exceeds the decompression activation speed, the decompression will not operate, and the engine will not be able to pass the top dead center of the compression stroke, which may cause reverse rotation during the compression stroke, or so-called kickback. In contrast, in this embodiment, the threshold value TH0 determines whether combustion is insufficient and the crank speed Ne is not high, and the ISG43 is assisted while keeping the first rotation speed Ne1 as the target value (steps ST75 to ST76 in Figure 7), thus suppressing the frequency of kickback. 【0084】Then, if combustion is successful in the combustion stroke following the initial combustion, as shown by the dashed line in Figure 8, when the crank rotation speed Ne exceeds the third rotation speed Ne3 and the detected time Tc of the crank rotation speed Ne in the combustion stroke has passed, the ISG 43 is turned OFF, and the fuel injection device 33 and ignition device 34 are controlled to increase the crank rotation speed Ne. 【0085】 Furthermore, if combustion is unsuccessful and the crank rotation speed Ne does not reach the threshold TH0 after a predetermined time has elapsed, the alarm device 151 is activated (steps ST74 to ST78 in Figure 7). This notifies the driver of a malfunction in the starting device related to starting the saddle-type vehicle 10, such as the ISG 43, and prompts appropriate repairs. 【0086】 Furthermore, in Figure 7, if it is determined that the crankshaft 23a is not in a stopped state (step ST71; NO), that is, if the engine is restarted with a crank rotation speed Ne greater than 300 rpm, the ISG 43 can be controlled with a target second rotation speed Ne2 to assist in overcoming the compression top dead center. 【0087】As described above, according to this embodiment to which the present invention is applied, the engine starting system (internal combustion engine starting system) comprises an engine 40, an ISG 43 that rotates the crankshaft 23a of the engine 40, a control device 100 that controls the engine 40 and the ISG 43, and a decompression mechanism 60 that reduces the compression pressure in the cylinder head 38 in the cylinder portion 24 of the engine 40, wherein when restarting the engine 40 from an idle stop state, the ISG 43 is rotated with a target value of a predetermined first rotational speed Ne1 that does not exceed the crank rotational speed Ne at which the operation of the decompression mechanism 60 stops, i.e., the decompression operating rotational speed, and the target value of the ISG 43 is not changed if the crank rotational speed Ne at a predetermined crank phase of the combustion stroke does not exceed a predetermined threshold TH0. With this configuration, even if restarting fails in the first cycle, cranking is performed so as not to exceed the crank rotation speed at which the decompression mechanism 60 stops operating until the next cycle. This allows the crankshaft to rotate smoothly past top dead center, preparing for restarting in the next cycle. Therefore, this configuration provides an engine starting system that can restart smoothly and quickly while utilizing the function of the ISG 43 as a starting motor. 【0088】 In this embodiment, if the crank speed Ne at a predetermined crank phase of the combustion stroke exceeds the threshold TH0, the target value of the ISG 43 is changed to a second rotation speed Ne2 that is greater than the first rotation speed Ne1. With this configuration, the decompression mechanism 60 operates during cranking, allowing the engine to rotate smoothly past the compression top dead center. Once the initial combustion is confirmed, the engine transitions to a rotation speed that assists cranking, allowing the engine 40 to start quickly and restart smoothly. 【0089】Furthermore, in this embodiment, the second rotational speed Ne2 is set higher than the decompression rotational speed and lower than the idling rotational speed NeI. With this configuration, by assisting the rotation of the crankshaft 23a, even if the combustion state after ignition is not good, it is possible to transition to a normal combustion state in the next cycle. In addition, since the ISG 43 does not provide more assistance than necessary, power consumption can be reduced. 【0090】 Furthermore, in this embodiment, the predetermined crank phase is the crank phase in which the angular velocity of the crankshaft 23a is maximized during the combustion stroke. This configuration allows for more accurate determination of the combustion state. 【0091】 Furthermore, in this embodiment, the engine 40 is a single-cylinder engine. With this configuration, reverse rotation of the compression stroke during restart can be effectively suppressed, making restarting easier. 【0092】 Furthermore, in this embodiment, at the start of startup, the ISG 43 is rotated to an initial rotational speed N0, which is a crank rotational speed Ne different from the first rotational speed Ne1, as the target value. With this configuration, smooth starting can be achieved even at the initial start-up when the stroke has not yet been determined. 【0093】 Furthermore, in this embodiment, the ISG 43 is arranged coaxially with the crankshaft 23a and used in conjunction with the generator. This configuration allows for more precise control of the crank rotation speed Ne. 【0094】 Furthermore, in this embodiment, when the crank speed Ne at a predetermined crank phase of the combustion stroke reaches a third rotation speed Ne3, the power supply to the ISG 43 is terminated. With this configuration, power consumption can be reduced by stopping the power supply to the ISG 43 after the engine 40 has finished starting. 【0095】 Furthermore, in this embodiment, if the first rotational speed Ne1 continues for a predetermined period of time, the power supply to the ISG 43 is terminated and a warning is issued. With this configuration, the driver can be notified of any malfunction in the starting device related to starting the vehicle, such as the ISG 43, and promptly encouraged to make appropriate repairs. 【0096】 [Other Embodiments] The embodiments described above are merely one aspect of the present invention and can be modified and applied as needed without departing from the spirit of the present invention. 【0097】 In the above embodiment, a configuration was described in which the rotational speed of the ISG 43 and the crank rotational speed Ne are the same, and a configuration was described in which the rotational speed of the ISG 43 is controlled to match the first rotational speed Ne1 and the second rotational speed Ne2 set by the crank rotational speed Ne. However, the embodiment is not limited to this. For example, the rotational speed of the starting motor may not match the rotational speed of the crankshaft 23a, and the operation target value of the starting motor may be set so that the crankshaft 23a is at the first rotational speed Ne1 and the second rotational speed Ne2, and the starting motor may be controlled accordingly. 【0098】 In the above embodiment, a configuration was described in which it is determined whether or not the threshold TH0 is exceeded based on the crank rotation speed Ne during the combustion stroke. However, instead of the crank rotation speed Ne, a configuration may be used in which the magnitude of the angular acceleration of the crank rotation speed Ne over a predetermined time is compared. 【0099】 In the above embodiment, a motorcycle having a front wheel 13 and a rear wheel 15 was used as an example to describe the saddle-type vehicle 10. However, the present invention is not limited thereto, and can be applied to three-wheeled saddle-type vehicles having two front or rear wheels, or saddle-type vehicles having four or more wheels. 【0100】 [Configurations supported by the above embodiment] The above embodiment supports the following configurations. 【0101】(Configuration 1) An internal combustion engine starting system comprising an internal combustion engine, a starting motor for rotating the crankshaft of the internal combustion engine, a control device for controlling the internal combustion engine and the starting motor, and a decompression mechanism for reducing the compression pressure in the cylinder of the internal combustion engine, wherein, in restarting the internal combustion engine from an idle stop state, the starting motor is rotated to a predetermined first rotational speed that does not exceed the crank rotational speed at which the decompression mechanism stops operating, and the target value of the starting motor is not changed if the crank rotational speed at a predetermined crank phase of the combustion stroke does not exceed a predetermined threshold. With this configuration, even if restarting in the first cycle fails, cranking is performed so as not to exceed the crank rotational speed at which the decompression mechanism stops operating until the next cycle, so that the crankshaft can be rotated smoothly past the compression top dead center and prepared for restarting in the next cycle. Therefore, with this configuration, it is possible to provide an internal combustion engine starting system that can easily restart smoothly while suppressing the use of the starting motor, thereby improving fuel efficiency. 【0102】 (Configuration 2) The starting system for an internal combustion engine according to Configuration 1, characterized in that, if the crank rotation speed at a predetermined crank phase of the combustion stroke exceeds the threshold, a second rotation speed greater than the first rotation speed is set to the target value of the starting motor. With this configuration, the decompression mechanism operates during cranking, allowing the engine to rotate smoothly beyond the compression top dead center, and once the initial combustion is confirmed, the engine transitions to a rotation speed that assists cranking, so that the internal combustion engine starts quickly and a smooth restart is possible. 【0103】(Configuration 3) The starting system for an internal combustion engine according to Configuration 2, characterized in that the second rotational speed is set higher than the crank rotational speed at which the decompression mechanism stops operating, and lower than the idling rotational speed. With this configuration, by assisting the rotation of the crankshaft, even if the combustion state after ignition is not good, it is possible to transition to a normal combustion state in the next cycle. In addition, since the starting motor does not provide more assistance than necessary, power consumption can be reduced. 【0104】 (Configuration 4) The starting system for an internal combustion engine according to Configuration 1, characterized in that the predetermined crank phase is the crank phase in which the angular velocity of the crankshaft is maximum during the combustion stroke. With this configuration, the combustion state can be determined more accurately. 【0105】 (Configuration 5) The starting system for an internal combustion engine according to Configuration 1, characterized in that the internal combustion engine is a single-cylinder engine. With this configuration, reverse rotation of the compression stroke during restart can be effectively suppressed, making restarting easier. 【0106】 (Configuration 6) The starting system for an internal combustion engine according to Configuration 1, characterized in that, at the start of starting, the starting motor is rotated with a crank rotation speed different from the first rotation speed as the target value. With this configuration, smooth starting can be performed even at the first start when the stroke has not been determined. 【0107】 (Configuration 7) The starting system for an internal combustion engine according to Configuration 1, characterized in that the starting motor is arranged coaxially with the crankshaft and used in combination with a generator. With this configuration, the crankshaft rotation speed can be controlled more precisely. 【0108】 (Configuration 8) An internal combustion engine starting system according to Configuration 1, characterized in that the power supply to the starting motor is terminated when the crank rotation speed reaches a third rotation speed in a predetermined crank phase of the combustion stroke. With this configuration, power consumption can be reduced by stopping the power supply to the starting motor after the starting of the internal combustion engine is complete. 【0109】(Configuration 9) The starting system for an internal combustion engine according to Configuration 2, characterized in that when the first rotational speed continues for a predetermined period of time, the power supply to the starting motor is terminated and a warning is issued. With this configuration, the driver can be notified of any malfunction in the starting device related to starting the vehicle, such as the starting motor, and is promptly encouraged to make appropriate repairs. 【0110】 10 Saddle-type vehicle 23a Crankshaft 24 Cylinder section (cylinder) 40 Engine (internal combustion engine) 43 ISG (starting motor) 60 Decompression mechanism 100 Control device TH0 Threshold Ne Crank rotation speed Ne1 First rotation speed Ne2 Second rotation speed Ne3 Third rotation speed NeI Idling rotation speed
Claims
1. An internal combustion engine starting system comprising an internal combustion engine (40), a starting motor (43) for rotating the crankshaft (23a) of the internal combustion engine (40), a control device (100) for controlling the internal combustion engine (40) and the starting motor (43), and a decompression mechanism (60) for reducing the compression pressure in the cylinder (24) of the internal combustion engine (40), wherein, in restarting the internal combustion engine (40) from an idle stop state, the starting motor (43) is rotated with a predetermined first rotational speed (Ne1) as the target value, which does not exceed the crank rotational speed (Ne) at which the operation of the decompression mechanism (60) stops, and the target value of the starting motor (43) is not changed if the crank rotational speed (Ne) at a predetermined crank phase of the combustion stroke does not exceed a predetermined threshold (TH0).
2. The starting system for an internal combustion engine according to claim 1, characterized in that, if the crank rotation speed (Ne) at a predetermined crank phase of the combustion stroke exceeds the threshold (TH0), a second rotation speed (Ne2) greater than the first rotation speed (Ne1) is changed to the target value of the starting motor (43).
3. The starting system for an internal combustion engine according to claim 2, characterized in that the second rotational speed (Ne2) is set higher than the crank rotational speed (Ne) at which the operation of the decompression mechanism (60) stops, and lower than the idling rotational speed (NeI).
4. The starting system for an internal combustion engine according to claim 1, characterized in that the predetermined crank phase is the crank phase in which the angular velocity of the crankshaft (23a) is maximized during the combustion stroke.
5. The starting system for an internal combustion engine according to claim 1, characterized in that the internal combustion engine (40) is a single-cylinder engine.
6. The starting system for an internal combustion engine according to claim 1, characterized in that, at the start of starting, the starting motor (43) is rotated with a target value of a crank rotation speed (Ne) different from the first rotation speed (Ne1).
7. The starting system for an internal combustion engine according to claim 1, characterized in that the starting motor (43) is arranged coaxially with the crankshaft (23a) and is used in combination with a generator.
8. The starting system for an internal combustion engine according to claim 1, characterized in that when the crank speed (Ne) at a predetermined crank phase of the combustion stroke reaches a third rotation speed (Ne3), the power supply to the starting motor (43) is terminated.
9. The starting system for an internal combustion engine according to claim 2, characterized in that when the first rotational speed (Ne1) is maintained for a predetermined period of time, the power supply to the starting motor (43) is terminated and a warning is issued.