Engine unit and saddle-ridden vehicle

Abstract

The present invention relates to an engine unit 21 and a saddle-ridden vehicle 1. The engine unit 21 comprises an engine 22, a motor 24, a first sensor 23, and a control portion 25. The motor 24 is connected to the engine 22. The motor 24 is configured to rotate the engine 22. The first sensor 23 detects a rotational speed G of the engine 22. The control portion 25 performs first assist control DA1 on the basis of the detection result of the first sensor 23. In the first assist control DA1, the control portion 25 causes the motor 24 to rotate the engine 22. When the rotational speed G is lower than a first threshold H1, the control portion 25 starts the first assist control DA1. The first threshold H1 is lower than an idle speed range J of the engine 22.

Description

Engine Unit and Straddle-Type Vehicle

[0001] The present invention relates to an engine unit and a straddle-type vehicle.

[0002] Patent Document 1 discloses a motorcycle. The motorcycle includes an engine, a fuel injection device, a motor, a first sensor, a second sensor, and a control unit. The fuel injection device supplies fuel to the engine. When the engine burns the fuel, the engine rotates. The motor outputs rotational power to the engine. The motor assists the rotation of the engine. The first sensor detects the rotational speed of the engine. The second sensor detects the amount of throttle grip operation. The control unit controls the fuel injection device and the motor based on the detection results of the first sensor and the second sensor. The control unit controls the fuel injection device and the motor in a range of the rotational speed of the engine that is equal to or higher than the idle speed range.

[0003] For example, when the rotational speed is equal to or higher than the idle speed range and the amount of throttle grip operation is zero, the control unit operates only the fuel injection device and does not operate the motor. The control unit reduces the amount of fuel supplied by the fuel injection device. Therefore, in the range of the rotational speed equal to or higher than the idle speed range, the motorcycle reduces the fuel consumption.

[0004] For example, when the rotational speed is equal to or higher than the idle speed range and the amount of throttle grip operation increases from zero, the control unit operates the motor in addition to operating the fuel injection device. The rotational speed of the engine rapidly increases by the motor. Therefore, in the range of the rotational speed equal to or higher than the idle speed range, the motorcycle has excellent acceleration response.

[0005] International Publication No. 2014 / 173982

[0006] The inventors have noticed one objective (hereinafter referred to as the "first objective") relating to a saddle-type vehicle. The first objective is to improve the comfort of a saddle-type vehicle for the driver when the engine speed is lower than the idle speed range. The first objective was previously unknown. The first objective itself is novel.

[0007] This invention has been made in view of these circumstances, and the object of this invention is the first object described above. Specifically, the object of this invention is to provide an engine unit and a saddle-type vehicle that are comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0008] First, the inventor came up with one technique (hereinafter referred to as "the first technique"). The first technique involves having a motor assist the rotation of the engine in the range of engine rotational speeds lower than the idle speed range.

[0009] Therefore, a saddle-type vehicle possessing the first technology was considered. Specifically, an engine unit possessing the first technology and a saddle-type vehicle including this engine unit were considered. As a result, it was found that when the engine unit possesses the first technology, the comfort of the engine unit for the driver is improved in the range of engine rotational speeds lower than the idle speed range. When the saddle-type vehicle includes an engine unit possessing the first technology, it was found that the comfort of the saddle-type vehicle for the driver is improved in the range of engine rotational speeds lower than the idle speed range.

[0010] Therefore, the engine unit and the saddle-type vehicle were further investigated. The present invention is based on these investigations. The present invention has the following configuration: That is, the present invention is an engine unit comprising: an engine; a motor connected to the engine and configured to rotate the engine; a first sensor for detecting the rotational speed of the engine; and a control unit that performs first assist control based on the detection result of the first sensor. In the first assist control, the control unit causes the motor to rotate the engine, and when the rotational speed is lower than a first threshold, the control unit starts the first assist control, and the first threshold is an engine unit where the engine's idle speed is lower than the idle speed range.

[0011] The engine unit comprises an engine, a motor, a first sensor, and a control unit. The motor is connected to the engine. The motor is configured to rotate the engine. The first sensor detects the rotational speed of the engine. The control unit performs first assist control based on the detection result of the first sensor. In the first assist control, the control unit causes the motor to rotate the engine. In other words, the first assist control assists the rotation of the engine.

[0012] When the rotational speed is lower than the first threshold, the control unit starts the first assist control. The first threshold is lower than the engine's idle speed range. Therefore, when the rotational speed is lower than the idle speed range, the control unit starts the first assist control. Thus, in the range of engine rotational speeds lower than the idle speed range, the first assist control assists the engine's rotation. Consequently, in the range of engine rotational speeds lower than the idle speed range, the first assist control appropriately controls the engine's rotational speed. In the range of engine rotational speeds lower than the idle speed range, the first assist control improves the comfort of the engine unit for the driver.

[0013] In summary, the engine unit is comfortable for the driver within the engine speed range below idle speed.

[0014] In this engine unit, it is preferable that the control unit does not start the first assist control when the rotational speed is equal to or greater than the first threshold. Therefore, in the range of engine rotational speeds lower than the idle speed range, the first assist control effectively assists the rotation of the engine. Thus, it is easy for the first assist control to appropriately control the engine rotational speed in the range of engine rotational speeds lower than the idle speed range. In the range of engine rotational speeds lower than the idle speed range, it is easy for the first assist control to improve the comfort of the engine unit for the driver.

[0015] In this engine unit, it is preferable that the control unit can start the first assist control only when the rotational speed is lower than the first threshold. Therefore, it is easy for the first assist control to appropriately control the engine rotational speed in the range of engine rotational speeds lower than the idle speed range. It is also easy for the first assist control to improve the comfort of the engine unit for the driver in the range of engine rotational speeds lower than the idle speed range.

[0016] In this engine unit, the idle speed range has a lower limit, and it is preferable that the first threshold is lower than the lower limit. Therefore, it is easy to make the first threshold lower than the idle speed range.

[0017] In this engine unit, the difference between the first threshold and the lower limit is preferably 50 rpm or more. Therefore, when the rotational speed is 50 rpm or more lower than the lower limit, the control unit starts the first assist control. Thus, in the range of engine rotational speeds 50 rpm or more lower than the lower limit, the first assist control assists the rotation of the engine. Consequently, in the range of engine rotational speeds 50 rpm or more lower than the lower limit, the engine unit is comfortable for the driver.

[0018] In this engine unit, it is preferable that the control unit does not start the first assist control while the engine is starting. Therefore, the first assist control does not interfere with the engine starting. Thus, the first assist control allows the engine to start.

[0019] In this engine unit, when the engine starts, the control unit performs a second assist control, in which the control unit causes the motor to rotate the engine, and while the second assist control is being performed, the first assist control is not performed, and it is preferable that the execution of the first assist control is permitted after the second assist control has finished. For this reason, the first assist control does not interfere with the execution of the second assist control. Thus, the first assist control permits the execution of the second assist control.

[0020] In this engine unit, when the rotational speed is lower than the first threshold and higher than the second threshold, the control unit starts the first assist control, and it is preferable that the second threshold is lower than the first threshold and higher than zero. Therefore, in the range of engine rotational speeds lower than the idle speed range and higher than zero, the first assist control assists the rotation of the engine. Consequently, in the range of engine rotational speeds lower than the idle speed range and higher than zero, the engine unit is comfortable for the driver.

[0021] In this engine unit, it is preferable that the control unit does not start the first assist control when the rotational speed is below the second threshold. Therefore, in the range of engine rotational speeds lower than the idle speed range and higher than zero, the first assist control effectively assists the rotation of the engine. Thus, it is easy for the first assist control to appropriately control the engine rotational speed in the range of engine rotational speeds lower than the idle speed range and higher than zero. In the range of engine rotational speeds lower than the idle speed range and higher than zero, it is easy for the first assist control to improve the comfort of the engine unit for the driver.

[0022] In this engine unit, it is preferable that the control unit can start the first assist control only when the rotational speed is lower than the first threshold and higher than the second threshold. Therefore, in the range of engine rotational speeds lower than the idle speed range and higher than zero, the first assist control effectively assists the rotation of the engine. Thus, it is easy for the first assist control to appropriately control the engine rotational speed in the range of engine rotational speeds lower than the idle speed range and higher than zero. In the range of engine rotational speeds lower than the idle speed range and higher than zero, it is easy for the first assist control to improve the comfort of the engine unit for the driver.

[0023] In this engine unit, it is preferable that the second threshold value is higher than half of the lower limit value. Therefore, when the rotational speed is lower than the idle speed range and higher than half of the lower limit value, the control unit starts the first assist control. Thus, in the range of engine rotational speeds that is lower than the idle speed range and higher than half of the lower limit value, the first assist control assists the rotation of the engine. Consequently, in the range of engine rotational speeds that is lower than the idle speed range and higher than half of the lower limit value, the engine unit is comfortable for the driver.

[0024] In this engine unit, it is preferable that the second threshold value is higher than half of the upper limit value. Therefore, when the rotational speed is lower than the idle speed range and higher than half of the upper limit value, the control unit starts the first assist control. Thus, in the range of engine rotational speeds that is lower than the idle speed range and higher than half of the upper limit value, the first assist control assists the rotation of the engine. Consequently, in the range of engine rotational speeds that is lower than the idle speed range and higher than half of the upper limit value, the engine unit is comfortable for the driver.

[0025] In this engine unit, it is preferable that the control unit initiates first assist control when the rotational speed decreases from a value higher than the first threshold to a value lower than the first threshold. Therefore, when the rotational speed decreases from a value higher than the first threshold to a value lower than the first threshold, the first assist control assists the rotation of the engine. Consequently, when the rotational speed decreases from a value higher than the first threshold to a value lower than the first threshold, the engine unit is comfortable for the driver.

[0026] In this engine unit, it is preferable that the control unit initiates first assist control when the rotational speed decreases from a value equal to or higher than the idle speed range to a value lower than the first threshold. Therefore, when the rotational speed decreases from a value equal to or higher than the idle speed range to a value lower than the first threshold, the first assist control assists the rotation of the engine. Consequently, when the rotational speed decreases from a value equal to or higher than the idle speed range to a value lower than the first threshold, the engine unit is comfortable for the driver.

[0027] In this engine unit, a generator configured to generate electricity by the rotation of the engine is provided, and the period during which the generator generates power after the most recent first assist control is completed is defined as the most recent power generation period. Even if the rotational speed is lower than the first threshold, it is preferable that the control unit does not start the first assist control until the most recent power generation period is equal to or greater than the first reference time. Therefore, the generator generates power appropriately during the most recent power generation period. Consequently, when two first assist controls are executed, the power balance does not decrease continuously. After one first assist control is completed and before the other first assist control is started, the power balance increases.

[0028] In this engine unit, it is preferable that the control unit starts the first assist control when the rotational speed is lower than the first threshold and the most recent power generation period is equal to or greater than the first reference time. Therefore, the generator generates a sufficient amount of power during the most recent power generation period. Multiple first assist controls are executed with intervals of equal to or greater than the first reference time between them.

[0029] In this engine unit, it is preferable that the amount of electricity consumed in one of the first assist control cycles is less than the amount of electricity generated by the generator in the first reference time. Therefore, the generator generates a sufficient amount of electricity in the most recent power generation period.

[0030] In this engine unit, it is preferable that the motor is configured to generate rotational power using electricity discharged from the battery, and the generator is configured to charge the battery. Therefore, it is easy for the motor to generate rotational power. Thus, it is easy for the motor to rotate the engine. In the first assist control, the battery discharges to the motor. During the power generation period, the battery is charged by the generator. As described above, the control unit does not start the first assist control until the most recent power generation period is equal to or greater than the first reference time. Therefore, when two first assist controls are executed, the battery's power balance does not decrease continuously. After one first assist control is completed and before the other first assist control begins, the battery's power balance increases.

[0031] In this engine unit, it is preferable that the motor also functions as the generator. Therefore, it is easy to miniaturize the entire motor and generator unit.

[0032] In this engine unit, it is preferable that the motor is integrated with the generator. Therefore, it is easy to miniaturize the entire motor and generator.

[0033] In this engine unit, even when the rotational speed is lower than the first threshold, it is preferable that the control unit does not start the first assist control when it performs engine stop control to stop the engine. Therefore, the first assist control does not interfere with the execution of engine stop control. The first assist control allows the execution of engine stop control.

[0034] In this engine unit, when the rotational speed is lower than the first threshold and the control unit does not perform engine stop control, it is preferable that the control unit starts the first assist control. For this reason, the first assist control starts at an appropriate timing.

[0035] In this engine unit, even if the rotational speed is lower than the first threshold, it is preferable that the control unit does not start the first assist control when the first operation to keep the engine rotating has not been performed. Therefore, the first assist control does not prevent the engine from stopping. The first assist control allows the engine to stop.

[0036] In this engine unit, it is preferable that the control unit starts the first assist control when the rotational speed is lower than the first threshold and a first operation is performed to keep the engine rotating. For this reason, the first assist control starts at an appropriate timing.

[0037] In this engine unit, even if the rotational speed is lower than the first threshold, it is preferable that the control unit does not start the first assist control if a predetermined device is not functioning correctly. Therefore, the first assist control does not start at an inappropriate timing.

[0038] In this engine unit, it is preferable that the control unit starts the first assist control when the rotational speed is lower than the first threshold and the predetermined equipment is functioning normally. Therefore, the first assist control starts at an appropriate timing.

[0039] In this engine unit, it is preferable that the control unit terminates the first assist control based on the detection result of the first sensor. Therefore, the timing at which the first assist control ends depends on the rotational speed of the engine. Thus, the first assist control ends at an appropriate timing. Therefore, the engine unit is comfortable for the driver.

[0040] In this engine unit, when the rotational speed is equal to or higher than a third threshold value, the control unit terminates the first assist control, and it is preferable that the third threshold value is higher than the first threshold value. Therefore, it is easy for the first assist control to end at an appropriate timing.

[0041] In this engine unit, the idle speed range has an upper limit value, and it is preferable that the third threshold value is not higher than the upper limit value. Therefore, it is easy for the first assist control to end at an appropriate timing.

[0042] In this engine unit, it is preferable that the third threshold value is not lower than the lower limit value. Therefore, it is easy for the first assist control to end at an appropriate timing.

[0043] In this engine unit, the control unit obtains a first quantity based on the detection result of the first sensor, the first quantity is the increase in the rotational speed due to the combustion of the engine, and it is preferable that the control unit terminates the first assist control based on the first quantity. Therefore, it is easy for the first assist control to end at an appropriate timing.

[0044] In this engine unit, when the first quantity is equal to or higher than a reference quantity, it is preferable that the control unit terminates the first assist control. Therefore, it is easy for the first assist control to end at an appropriate timing.

[0045] In this engine unit, the rotational speed includes a first instantaneous value indicating the rotational speed at the moment when the combustion of the engine starts and a second instantaneous value indicating the rotational speed at the moment when the combustion of the engine ends, and it is preferable that the first amount is an increase amount from the first instantaneous value to the second instantaneous value. For this reason, it is easy to obtain the first amount.

[0046] In this engine unit, the engine repeats a cycle, the engine combusts in each cycle, and it is preferable that the first instantaneous value and the second instantaneous value are obtained during each cycle. For this reason, it is easy to obtain the first amount in each cycle.

[0047] In this engine unit, when the first assist period during which the first assist control is executed is longer than a second reference time, it is preferable that the control unit ends the first assist control. For this reason, the first assist period is limited to be not longer than the second reference time. Therefore, the first assist period is not excessively long.

[0048] In this engine unit, it is preferable that the second reference time is 1 second or less. For this reason, the first assist period is relatively short.

[0049] In this engine unit, it is preferable that the second reference time is shorter than the first reference time. For this reason, it is easy to increase the power balance.

[0050] In this engine unit, when the control unit performs engine stop control for stopping the engine, it is preferable that the control unit ends the first assist control. For this reason, the first assist control does not prevent the execution of the engine stop control. The first assist control allows the execution of the engine stop control.

[0051] In this engine unit, when a second operation to stop the engine is performed, it is preferable that the control unit terminates the first assist control. Therefore, the first assist control does not prevent the engine from stopping. The first assist control allows the engine to stop.

[0052] In this engine unit, it is preferable that the control unit terminates the first assist control when a predetermined device malfunctions. Therefore, the first assist control does not prevent the engine from stopping. The first assist control allows the engine to stop.

[0053] In this engine unit, a fuel injection device is provided, and during the period in which the first assist control is performed, it is preferable that the control unit controls the fuel injection device to supply fuel to the engine. Therefore, during the period in which the first assist control is performed, the control unit controls the fuel injection device to rotate the engine. Thus, during the period in which the first assist control is performed, the control unit causes the fuel injection device to rotate the engine and the motor to assist the rotation of the engine. Consequently, during the period in which the first assist control is performed, the control unit controls the rotational speed of the engine more appropriately.

[0054] In this engine unit, during the period in which the first assist control is performed, it is preferable that the control unit controls the fuel injection device to adjust the amount of fuel supplied to the engine. Therefore, it is easy for the control unit to more appropriately control the engine's rotational speed during the period in which the first assist control is performed.

[0055] In this engine unit, a throttle device is provided, and during the period in which the first assist control is performed, it is preferable that the control unit controls the throttle device to supply air to the engine. Therefore, during the period in which the first assist control is performed, the control unit controls the throttle device to rotate the engine. Thus, during the period in which the first assist control is performed, the control unit causes the throttle device to rotate the engine and the motor to assist the rotation of the engine. Consequently, during the period in which the first assist control is performed, the control unit controls the rotational speed of the engine more appropriately.

[0056] In this saddle-type vehicle, during the period in which the first assist control is performed, it is preferable that the control unit controls the throttle device to adjust the amount of air supplied to the engine. Therefore, it is easy for the control unit to more appropriately control the engine's rotational speed during the period in which the first assist control is performed.

[0057] In this engine unit, an ignition device is provided, and during the period when the first assist control is performed, it is preferable that the control unit controls the ignition device to ignite the fuel-air mixture in the engine. Therefore, during the period when the first assist control is performed, the control unit controls the ignition device to rotate the engine. Thus, during the period when the first assist control is performed, the control unit causes the ignition device to rotate the engine and the motor to assist the rotation of the engine. Consequently, during the period when the first assist control is performed, the control unit controls the rotational speed of the engine more appropriately.

[0058] In this saddle-type vehicle, during the period in which the first assist control is performed, it is preferable that the control unit controls the ignition device to adjust the ignition timing of the air-fuel mixture in the engine. Therefore, it is easy for the control unit to more appropriately control the engine's rotational speed during the period in which the first assist control is performed.

[0059] The present invention relates to a saddle-type vehicle, comprising the engine unit described above and a saddle-type vehicle.

[0060] As mentioned above, the engine unit is comfortable for the driver in the range of engine rotational speeds below the idle speed range. Therefore, saddle-type vehicles are comfortable for the driver in the range of engine rotational speeds below the idle speed range.

[0061] In this saddle-type vehicle, it is preferable that the control unit initiates the first assist control regardless of the speed of the saddle-type vehicle. Therefore, regardless of the speed of the saddle-type vehicle, the saddle-type vehicle is comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0062] In this saddle-type vehicle, it is preferable that the control unit initiates the first assist control regardless of the acceleration of the saddle-type vehicle. Therefore, regardless of the acceleration of the saddle-type vehicle, the saddle-type vehicle is comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0063] In this saddle-type vehicle, it is preferable that the control unit initiates the first assist control regardless of the amount of accelerator operation provided in the saddle-type vehicle. Therefore, regardless of the amount of accelerator operation, the saddle-type vehicle is comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0064] In this saddle-type vehicle, it is preferable that the control unit initiates the first assist control regardless of the operation of the throttle device provided in the engine unit. Therefore, regardless of the operation of the throttle device, the saddle-type vehicle is comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0065] In this saddle-type vehicle, it is preferable that the control unit terminates the first assist control regardless of the speed of the saddle-type vehicle. Therefore, regardless of the speed of the saddle-type vehicle, the saddle-type vehicle is comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0066] In this saddle-type vehicle, it is preferable that the control unit terminates the first assist control regardless of the acceleration of the saddle-type vehicle. Therefore, regardless of the acceleration of the saddle-type vehicle, the saddle-type vehicle is comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0067] In this saddle-type vehicle, it is preferable that the control unit terminates the first assist control regardless of the amount of accelerator operation provided in the saddle-type vehicle. Therefore, regardless of the amount of accelerator operation, the saddle-type vehicle is comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0068] In this saddle-type vehicle, it is preferable that the control unit terminates the first assist control regardless of the operation of the throttle device provided in the engine unit. Therefore, regardless of the operation of the throttle device, the saddle-type vehicle is comfortable for the driver in the range of engine rotational speeds lower than the idle speed range.

[0069] In the range of engine rotational speeds below idle speed, the engine unit is comfortable for the driver. In the range of engine rotational speeds below idle speed, the saddle-type vehicle is comfortable for the driver.

[0070] This is a side view of a saddle-type vehicle according to the first embodiment. This is a flowchart showing the procedure for an example of the operation of the engine unit of the first embodiment. This is a timing chart showing an example of the operation of the engine unit of the first embodiment. This is a side view of a saddle-type vehicle according to the second embodiment. This is a partial cross-sectional view showing the configuration of the engine unit. This is a diagram of the motor generator viewed from the direction of the axis of the crankshaft. This is a block diagram showing the electrical configuration of the engine unit. This is a flowchart showing the procedure for an example of the operation of the engine unit of the second embodiment. This is a timing chart showing an example of the operation of the engine unit of the second embodiment. This is a graph explaining the first quantity. This is a side view of a saddle-type vehicle according to the third embodiment. This is a block diagram showing the electrical configuration of the engine unit. This is a table showing specific examples of start conditions. This is a table showing specific examples of end conditions.

[0071] The saddle-type vehicle according to the present invention will be described below with reference to the drawings.

[0072] 1. First Embodiment 1-1. The schematic diagram 1 of the saddle-type vehicle 1 is a side view of the saddle-type vehicle 1 according to the first embodiment. The saddle-type vehicle 1 is, for example, a motorcycle.

[0073] The saddle-type vehicle 1 comprises a body 3, a front fork 5, a front wheel 7, and a handlebar 9. The front fork 5 is supported by the body 3. The front wheel 7 is supported by the front fork 5. The handlebar 9 is supported by the front fork 5.

[0074] The saddle-type vehicle 1 is equipped with a seat 15. The seat 15 is supported by the vehicle body. The seat 15 is positioned behind the handlebars 9.

[0075] The driver sits on the saddle-type vehicle 1. The driver sits on the seat 15. The driver grips the handlebars 9. The driver is also called the rider.

[0076] The saddle-type vehicle 1 is equipped with a swing arm 17 and a rear wheel 18. The swing arm 17 is supported by the vehicle body 3. The rear wheel 18 is supported by the swing arm 17. The rear wheel 18 is positioned behind the front wheel 7.

[0077] The saddle-type vehicle 1 is equipped with an engine unit 21. The engine unit 21 is supported by the vehicle body 3.

[0078] The engine unit 21 includes an engine 22. The engine 22 is an internal combustion engine. The engine 22 rotates. Hereinafter, the rotational speed of the engine 22 will be referred to as "rotational speed G". The engine 22 rotates at rotational speed G. The engine 22 generates rotational power. The rotational power of the engine 22 is used to propel the saddle-type vehicle 1.

[0079] For example, the engine 22 drives the rear wheels 18. For example, the saddle-type vehicle 1 is equipped with a power transmission mechanism (not shown). The power transmission mechanism transmits rotational power from the engine 22 to the rear wheels 18. The power transmission mechanism is, for example, a chain. When the power transmission mechanism transmits rotational power to the rear wheels 18, the rear wheels 18 rotate and the saddle-type vehicle 1 moves forward.

[0080] 1-2. Outline Configuration of Engine Unit 21 The engine unit 21 includes an engine 22 and a first sensor 23. The first sensor 23 detects the rotational speed G.

[0081] The engine unit 21 includes a motor 24. The motor 24 generates rotational power. The motor 24 converts electrical power into rotational power. The motor 24 is also called an electric motor.

[0082] The motor 24 is connected to the engine 22. The motor 24 is configured to rotate the engine 22. The motor 24 outputs rotational power to the engine 22.

[0083] The engine unit 21 includes a control unit 25. The control unit 25 acquires the detection result of the first sensor 23. The control unit 25 controls the motor 24 based on the detection result of the first sensor 23. The control unit 25 may also be an Engine Control Unit (ECU) provided in the saddle-type vehicle 1.

[0084] For example, the control unit 25 performs first assist control. In first assist control, the control unit 25 causes the motor 24 to rotate the engine 22. Hereafter, first assist control will be referred to as "first assist control DA1" as appropriate.

[0085] Although not shown in the diagram, the control unit 25 includes a memory. The memory stores information. The information includes, for example, information relating to the first assist control DA1. The information relating to the first assist control DA1 includes, for example, a program for the first assist control DA1, conditions for starting the first assist control DA1, and conditions for ending the first assist control DA1. Hereinafter, the conditions for starting the first assist control DA1 will be appropriately referred to as "start condition A". The conditions for ending the first assist control DA1 will be appropriately referred to as "end condition B". The memory includes, for example, at least one of a semiconductor memory and a hard disk.

[0086] Although not shown in the diagram, the control unit 25 includes, for example, a processor. The processor reads information from memory. The processor executes, for example, a program for the first assist control DA1. The processor refers to, for example, start condition A and end condition B. The processor includes, for example, a central processing unit (CPU).

[0087] 1-3. Operation Example of Engine Unit 21 of the First Embodiment Figure 2 is a flowchart showing the procedure for an operation example of the engine unit 21 of the first embodiment. In the following operation example, it is assumed that the engine 22 is rotating. It is assumed that the engine 22 is not in the process of starting. It is assumed that the engine 22 has already completed starting.

[0088] Step S1: Is the starting condition A met? The control unit 25 determines whether the starting condition A is met. If the starting condition A is met, proceed to step S2. Otherwise, repeat the process in step S1.

[0089] Step S2: First assist control DA1 begins. The control unit 25 starts the first assist control DA1.

[0090] Step S3: Is termination condition B met? The control unit 25 determines whether termination condition B is met. If termination condition B is met, proceed to step S4. Otherwise, repeat the process in step S3.

[0091] Step S4: The first assist control DA1 ends. The control unit 25 terminates the first assist control DA1.

[0092] Here, the starting condition A depends on the rotational speed G. Therefore, the control unit 25 determines whether the starting condition A is met based on the detection result of the first sensor 23. Then, the control unit 25 starts the first assist control DA1 based on the detection result of the first sensor 23.

[0093] For example, starting condition A depends only on the rotational speed G. The control unit 25 determines whether starting condition A is met based solely on the detection result of the first sensor 23. Then, the control unit 25 starts the first assist control DA1 based solely on the detection result of the first sensor 23.

[0094] For example, termination condition B depends on the rotation speed G. Therefore, the control unit 25 determines whether termination condition B is met based on the detection result of the first sensor 23. Then, the control unit 25 terminates the first assist control DA1 based on the detection result of the first sensor 23.

[0095] For example, termination condition B depends only on the rotation speed G. The control unit 25 determines whether termination condition B is met based solely on the detection result of the first sensor 23. Then, the control unit 25 terminates the first assist control DA1 based solely on the detection result of the first sensor 23.

[0096] As described above, the control unit 25 performs the first assist control DA1 based on the detection result of the first sensor 23. For example, the control unit 25 performs the first assist control DA1 based solely on the detection result of the first sensor 23.

[0097] Let's explain a specific example of starting condition A. For example, starting condition A includes a first starting condition A1. The first starting condition A1 is "the rotational speed G is lower than the first threshold H1". When the first starting condition A1 is met, starting condition A is met. When the first starting condition A1 is not met, starting condition A is not met.

[0098] Let's explain a specific example of termination condition B. For example, termination condition B includes a first termination condition B1. The first termination condition B1 is "the rotational speed G is higher than the third threshold H3". When the first termination condition B1 is met, termination condition B is met. When the first termination condition B1 is not met, termination condition B is not met.

[0099] Figure 3 is a timing chart showing an example of the operation of the engine unit 21 of the first embodiment. The horizontal axis represents time T. The vertical axis represents the control performed by the control unit 25, the period during which the control by the control unit 25 is performed, and the rotational speed G.

[0100] The rotational speed G includes the idle speed range J of the engine 22. When the rotational speed G is within the idle speed range J, the saddle-type vehicle 1 is stationary. The idle speed range J is, for example, in the range from 1,200 rpm to 1,400 rpm.

[0101] The idle speed range J has an upper limit JU. The upper limit JU is, for example, 1,400 rpm.

[0102] The idle speed range J has a lower limit JL. The lower limit JL is lower than the upper limit JU. For example, the lower limit JL is 1,200 rpm.

[0103] The first threshold H1 is set in advance.

[0104] The first threshold H1 is lower than the idle speed range J.

[0105] The first threshold H1 is lower than the upper limit JU.

[0106] The first threshold H1 is lower than the lower limit JL.

[0107] The difference between the first threshold H1 and the lower limit JL is 50 rpm or more.

[0108] The first threshold H1 is, for example, 1,000 rpm. The difference between the first threshold H1 and the lower limit JL is, for example, 200 rpm.

[0109] The first threshold H1 is higher than zero.

[0110] The third threshold H3 is set in advance.

[0111] The third threshold H3 is higher than zero.

[0112] The third threshold H3 is higher than the first threshold H1.

[0113] The third threshold H3 is within the idle speed range J.

[0114] The third threshold H3 is greater than or equal to the lower limit JL.

[0115] The third threshold is less than or equal to the upper limit JU.

[0116] The third threshold H3 is, for example, 1,300 rpm.

[0117] From time T0 to time T5, the control unit 25 acquires the rotation speed G based on the detection result of the first sensor 23.

[0118] From time T0 to time T5, the rotational speed G is greater than zero.

[0119] From time T0 to time T3, the rotational speed G is higher than the first threshold H1. Therefore, from time T0 to time T3, the first start condition A1 is not met. Thus, from time T0 to time T3, the start condition A is not met. Consequently, from time T0 to time T3, the control unit 25 does not start the first assist control DA1. From time T0 to time T3, the control unit 25 does not perform the first assist control DA1.

[0120] At time T3, the rotational speed G is lower than the first threshold H1.

[0121] Let me explain in more detail. Before time T3, the rotational speed G is higher than the first threshold H1. After time T3, the rotational speed G is lower than the first threshold H1. Therefore, at time T3, the rotational speed G decreases from a value higher than the first threshold H1 to a value lower than the first threshold H1.

[0122] Before time T2, the rotational speed G is equal to or higher than the idle speed range J. Specifically, from time T0 to time T1, the rotational speed G is higher than the idle speed range J. From time T1 to time T2, the rotational speed G is equal to the idle speed range J. After time T3, the rotational speed G is lower than the first threshold H1. Therefore, at time T3, the rotational speed G decreases from a value equal to or higher than the idle speed range J to a value lower than the first threshold H1.

[0123] Therefore, at time T3, the first start condition A1 is satisfied. Thus, at time T3, the start condition A is satisfied. Consequently, at time T3, the control unit 25 starts the first assist control DA1.

[0124] From time T3 to time T4, the rotational speed G is lower than the third threshold H3. Therefore, from time T3 to time T4, the first termination condition B1 is not met. Consequently, from time T3 to time T4, termination condition B is not met. Therefore, from time T3 to time T4, the control unit 25 does not terminate the first assist control DA1.

[0125] At time T4, the rotational speed G is greater than or equal to the third threshold H3. Therefore, at time T4, the first termination condition B1 is satisfied. Thus, at time T4, termination condition B is satisfied. Consequently, at time T4, the control unit 25 terminates the first assist control DA1.

[0126] As a result, the first assist control is not performed from time T0 to time T3. The first assist control is performed from time T3 to time T4. The first assist control is not performed from time T4 to time T5.

[0127] The period during which the first assist control is performed is called the "first assist period FA1". The first assist period FA1 is the period from time T3 to time T4.

[0128] In the first assist control DA1, the control unit 25 causes the motor 24 to rotate the engine 22. In the first assist control DA1, the motor 24 assists the rotation of the engine 22. In other words, the first assist control DA1 assists the rotation of the engine 22.

[0129] Therefore, during the first assist period FA1, the rotational speed G is unlikely to decrease. During the first assist period FA1, the rotational speed G is likely to increase.

[0130] When the first assist control DA1 begins, the rotational speed G is lower than the idle speed range J. Therefore, in the range of rotational speed G lower than the idle speed range J, the rotational speed G is unlikely to decrease. In the range of rotational speed G lower than the idle speed range J, the rotational speed G is unlikely to decrease to an excessively low value. In the range of rotational speed G lower than the idle speed range J, the decrease in rotational speed G is likely to stop. In the range of rotational speed G lower than the idle speed range J, the rotational speed G is likely to increase. In the range of rotational speed G lower than the idle speed range J, the rotational speed G is likely to change from decreasing to increasing.

[0131] During the first assist period FA1, the rotational speed G tends to increase from a value lower than the idle speed range J to a value within the idle speed range J.

[0132] The cases in which the control unit 25 starts the first assist control DA1 and the cases in which the control unit 25 does not start the first assist control DA1 are listed below.

[0133] When the rotational speed G is lower than the first threshold H1, the control unit 25 starts the first assist control DA1. In other words, the control unit 25 starts the first assist control DA1 on the condition that the rotational speed G is lower than the first threshold H1.

[0134] When the rotational speed G is greater than or equal to the first threshold H1, the control unit 25 does not start the first assist control DA1.

[0135] The control unit 25 can start the first assist control DA1 only when the rotational speed G is lower than the first threshold H1.

[0136] For example, when the rotational speed G is lower than the idle speed range J, the control unit 25 starts the first assist control DA1.

[0137] When the rotational speed G is equal to or higher than the idle speed range J, the control unit 25 does not start the first assist control DA1.

[0138] For example, when the rotational speed G is lower than the lower limit JL, the control unit 25 starts the first assist control DA1.

[0139] When the rotational speed G is higher than the lower limit JL, the control unit 25 starts the first assist control DA1.

[0140] For example, when the rotational speed G is 50 rpm or more lower than the lower limit JL, the control unit 25 starts the first assist control DA1.

[0141] For example, when the difference between the rotational speed G and the lower limit JL is less than 50 rpm, the control unit 25 does not start the first assist control DA1. When the rotational speed G is near the lower limit JL, the control unit 25 does not start the first assist control DA1. For example, when the rotational speed G is substantially equivalent to the idle speed range J, the control unit 25 does not start the first assist control DA1.

[0142] When the rotational speed G decreases from a value higher than the first threshold H1 to a value lower than the first threshold H1, the control unit 25 starts the first assist control DA1.

[0143] When the rotational speed G decreases from a value equal to or higher than the idle speed range J to a value lower than the first threshold H1, the control unit 25 starts the first assist control DA1.

[0144] Furthermore, when the engine 22 is not rotating, the control unit 25 does not start the first assist control DA1.

[0145] The control unit 25 can start the first assist control DA1 only when the engine 22 is rotating.

[0146] When the rotational speed G is zero, the control unit 25 does not start the first assist control DA1.

[0147] While the engine 22 is starting, the control unit 25 does not start the first assist control DA1.

[0148] The starting condition A is independent of the speed of the saddle-type vehicle 1. Regardless of the speed of the saddle-type vehicle 1, the control unit 25 starts the first assist control DA1.

[0149] For example, even when the speed of the saddle-type vehicle 1 is zero, the control unit 25 can start the first assist control DA1. For example, even when the saddle-type vehicle 1 is stopped, the control unit 25 can start the first assist control DA1. For example, even when the speed of the saddle-type vehicle 1 is greater than zero, the control unit 25 can start the first assist control DA1. For example, even when the saddle-type vehicle 1 is moving, the control unit 25 can start the first assist control DA1.

[0150] The starting condition A does not depend on the acceleration of the saddle-type vehicle 1. Regardless of the acceleration of the saddle-type vehicle 1, the control unit 25 starts the first assist control DA1.

[0151] For example, even when the acceleration of the saddle-type vehicle 1 is zero, the control unit 25 can start the first assist control DA1. For example, even when the saddle-type vehicle 1 is traveling at a constant speed, the control unit 25 can start the first assist control DA1. For example, even when the acceleration of the saddle-type vehicle 1 is greater than zero, the control unit 25 can start the first assist control DA1. For example, even when the saddle-type vehicle 1 is accelerating, the control unit 25 can start the first assist control DA1. For example, even when the saddle-type vehicle 1 is starting up, the control unit 25 can start the first assist control DA1. For example, even when the acceleration of the saddle-type vehicle 1 is less than zero, the control unit 25 can start the first assist control DA1. For example, even when the saddle-type vehicle 1 is decelerating, the control unit 25 can start the first assist control DA1.

[0152] Although not shown in the diagram, the saddle-type vehicle 1 is equipped with an accelerator. The starting condition A does not depend on the amount of accelerator operation. Regardless of the amount of accelerator operation, the control unit 25 starts the first assist control DA1.

[0153] For example, even when the amount of accelerator operation is zero, the control unit 25 can start the first assist control DA1. For example, even when the amount of accelerator operation is greater than zero, the control unit 25 can start the first assist control DA1. For example, even when the amount of accelerator operation increases, the control unit 25 can start the first assist control DA1. For example, even when the amount of accelerator operation decreases, the control unit 25 can start the first assist control DA1.

[0154] Although not shown in the diagram, the engine unit 21 is equipped with a throttle device. The starting condition A does not depend on the operation of the throttle device. Regardless of the operation of the throttle device, the control unit 25 starts the first assist control DA1.

[0155] For example, even when the throttle device is operating, the control unit 25 can start the first assist control DA1. For example, even when the throttle device is not operating, the control unit 25 can start the first assist control DA1.

[0156] The cases in which the control unit 25 terminates the first assist control DA1 and the cases in which the control unit 25 does not terminate the first assist control DA1 are listed below.

[0157] When the rotational speed G is equal to or greater than the third threshold H3, the control unit 25 terminates the first assist control DA1. In other words, the control unit 25 terminates the first assist control DA1 on the condition that the rotational speed G is equal to or greater than the third threshold H1.

[0158] When the rotational speed G is lower than the third threshold H3, the control unit 25 does not terminate the first assist control DA1.

[0159] For example, when the rotational speed G is lower than the idle speed range J, the control unit 25 does not terminate the first assist control DA1.

[0160] For example, when the rotational speed G is within the idle speed range J, the control unit 25 terminates the first assist control DA1.

[0161] For example, when the rotational speed G is greater than or equal to the lower limit value JU, the control unit 25 terminates the first assist control DA1.

[0162] For example, when the rotational speed G is less than or equal to the upper limit value JU, the control unit 25 terminates the first assist control DA1.

[0163] For example, when the rotational speed G is greater than or equal to the lower limit JU and less than or equal to the upper limit JU, the control unit 25 terminates the first assist control DA1.

[0164] For example, the control unit 25 terminates the first assist control DA1 before the rotational speed G exceeds the idle speed range J. Therefore, when the rotational speed G is higher than the idle speed range J, the control unit 25 does not execute the first assist control DA1. In other words, in the range of rotational speeds G higher than the idle speed range J, the control unit 25 does not execute the first assist control DA1.

[0165] For example, the control unit 25 terminates the first assist control DA1 before the rotational speed G exceeds the upper limit value JU. Therefore, when the rotational speed G is higher than the upper limit value JU, the control unit 25 does not execute the first assist control DA1. In other words, within the range of rotational speeds G higher than the upper limit value JU, the control unit 25 does not execute the first assist control DA1.

[0166] Note that termination condition B does not depend on the speed of the saddle-type vehicle 1. Regardless of the speed of the saddle-type vehicle 1, the control unit 25 terminates the first assist control DA1.

[0167] Termination condition B is independent of the acceleration of the saddle-type vehicle 1. Regardless of the acceleration of the saddle-type vehicle 1, the control unit 25 terminates the first assist control DA1.

[0168] Termination condition B does not depend on the amount of accelerator operation of the saddle-type vehicle 1. Regardless of the amount of accelerator operation, the control unit 25 terminates the first assist control DA1.

[0169] Termination condition B does not depend on the operation of the throttle device of the engine unit 21. Regardless of the operation of the throttle device, the control unit 25 terminates the first assist control DA1.

[0170] 1-4. Effects of the First Embodiment The engine unit 21 comprises an engine 22, a motor 24, a first sensor 23, and a control unit 25. The motor 24 is connected to the engine 22. The motor 24 is configured to rotate the engine 22. The first sensor 23 detects the rotational speed G of the engine 22. The control unit 25 performs first assist control DA1 based on the detection result of the first sensor 23. In first assist control DA1, the control unit 25 causes the motor 24 to rotate the engine 22. That is, first assist control DA1 assists the rotation of the engine 22.

[0171] When the rotational speed G is lower than the first threshold H1, the control unit 25 starts the first assist control DA1. The first threshold H1 is lower than the idle speed range J. Therefore, when the rotational speed G is lower than the idle speed range J, the control unit 25 starts the first assist control DA1. Thus, in the range of rotational speed G lower than the idle speed range J, the first assist control DA1 assists the rotation of the engine 22. Thus, in the range of rotational speed G lower than the idle speed range J, the first assist control DA1 appropriately controls the rotational speed G. In the range of rotational speed G lower than the idle speed range J, the first assist control DA1 improves the comfort of the engine unit 21 for the driver.

[0172] In summary, the engine unit 21 is comfortable for the driver in the range of rotational speeds G lower than the idle speed range J.

[0173] When the rotational speed G is equal to or greater than the first threshold H1, the control unit 25 does not start the first assist control DA1. Therefore, when the rotational speed G is equal to or higher than the idle speed range J, the first assist control DA1 does not start. In other words, the first assist control DA1 focuses on the range of rotational speed G that is lower than the idle speed range J. Therefore, in the range of rotational speed G that is lower than the idle speed range J, the first assist control DA1 effectively assists the rotation of the engine 22. Consequently, it is easy for the first assist control DA1 to appropriately control the rotational speed G in the range of rotational speed G that is lower than the idle speed range J. In the range of rotational speed G that is lower than the idle speed range J, it is easy for the first assist control DA1 to improve the comfort of the engine unit 21 for the driver.

[0174] The control unit 25 can start the first assist control DA1 only when the rotational speed G is lower than the first threshold H1. For this reason, the first assist control DA1 focuses on the range of rotational speed G that is lower than the idle speed range J. Therefore, in the range of rotational speed G that is lower than the idle speed range J, the first assist control DA1 effectively assists the rotation of the engine 22. Thus, it is easy for the first assist control DA1 to appropriately control the rotational speed G in the range of rotational speed G that is lower than the idle speed range J. In the range of rotational speed G that is lower than the idle speed range J, it is easy for the first assist control DA1 to improve the comfort of the engine unit 21 for the driver.

[0175] The idle speed range J has a lower limit JL. The first threshold H1 is lower than the lower limit JL. Therefore, it is easy to make the first threshold H1 lower than the idle speed range J.

[0176] The difference between the first threshold H1 and the lower limit JL is 50 rpm or more. Therefore, when the rotational speed G is 50 rpm or more lower than the lower limit, the control unit 25 starts the first assist control DA1. Thus, in the range of rotational speed G that is 50 rpm or more lower than the lower limit JL, the first assist control DA1 assists the rotation of the engine 22. Consequently, in the range of rotational speed G that is 50 rpm or more lower than the lower limit JL, the engine unit 21 is comfortable for the driver.

[0177] While the engine 22 is starting, the control unit 25 does not start the first assist control DA1. Therefore, the first assist control DA1 does not interfere with the starting of the engine 22. Thus, the first assist control DA1 allows the starting of the engine 22.

[0178] When the rotational speed G decreases from a value higher than the first threshold H1 to a value lower than the first threshold H1, the control unit 25 starts the first assist control DA1. Therefore, when the rotational speed G decreases from a value higher than the first threshold H1 to a value lower than the first threshold H1, the first assist control DA1 assists the rotation of the engine 22. Consequently, when the rotational speed G decreases from a value higher than the first threshold H1 to a value lower than the first threshold H1, the engine unit 21 is comfortable for the driver.

[0179] When the rotational speed G decreases from a value equal to or higher than the idle speed range J to a value lower than the first threshold H1, the control unit 25 starts the first assist control DA1. Therefore, when the rotational speed G decreases from a value equal to or higher than the idle speed range J to a value lower than the first threshold H1, the first assist control DA1 assists the rotation of the engine 22. Consequently, when the rotational speed G decreases from a value equal to or higher than the idle speed range J to a value lower than the first threshold H1, the engine unit 21 is comfortable for the driver.

[0180] The control unit 25 terminates the first assist control DA1 based on the detection result of the first sensor 23. Therefore, the timing of the termination of the first assist control DA1 depends on the rotational speed G. Thus, the first assist control DA1 terminates at an appropriate timing. Consequently, the engine unit 21 is comfortable for the driver.

[0181] When the rotational speed G is greater than or equal to the third threshold H3, the control unit 25 terminates the first assist control DA1. The third threshold H3 is higher than the first threshold H1. Therefore, it is easy to terminate the first assist control DA1 at an appropriate timing.

[0182] The idle speed range J has an upper limit value JU. The third threshold H3 is less than or equal to the upper limit value JU. Therefore, it is easy for the first assist control DA1 to terminate at an appropriate timing.

[0183] The third threshold H3 is greater than or equal to the lower limit JL. Therefore, it is easy for the first assist control DA1 to terminate at the appropriate timing.

[0184] As mentioned above, the third threshold H3 is greater than or equal to the lower limit JL. Therefore, it is easy to control the rotational speed G to a value greater than or equal to the lower limit JL.

[0185] The saddle-type vehicle 1 is equipped with an engine unit 21. As described above, the engine unit 21 is comfortable for the driver in the range of rotational speed G, which is lower than the idle speed range J. Therefore, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G, which is lower than the idle speed range J.

[0186] Regardless of the speed of the saddle-type vehicle 1, the control unit 25 starts the first assist control DA1. Therefore, regardless of the speed of the saddle-type vehicle 1, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G which is lower than the idle speed range J.

[0187] Regardless of the acceleration of the saddle-type vehicle 1, the control unit 25 starts the first assist control DA1. Therefore, regardless of the acceleration of the saddle-type vehicle 1, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G which is lower than the idle speed range J.

[0188] Regardless of the amount of accelerator operation on the saddle-type vehicle 1, the control unit 25 starts the first assist control DA1. Therefore, regardless of the amount of accelerator operation, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G lower than the idle speed range J.

[0189] Regardless of the operation of the throttle device provided in the engine unit 21, the control unit 25 starts the first assist control DA1. Therefore, regardless of the operation of the throttle device, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G lower than the idle speed range J.

[0190] Regardless of the speed of the saddle-type vehicle 1, the control unit 25 terminates the first assist control DA1. Therefore, regardless of the speed of the saddle-type vehicle 1, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G which is lower than the idle speed range J.

[0191] Regardless of the acceleration of the saddle-type vehicle 1, the control unit 25 terminates the first assist control DA1. Therefore, regardless of the acceleration of the saddle-type vehicle 1, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G which is lower than the idle speed range J.

[0192] Regardless of the amount of accelerator operation on the saddle-type vehicle 1, the control unit 25 terminates the first assist control DA1. Therefore, regardless of the amount of accelerator operation, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G lower than the idle speed range J.

[0193] Regardless of the operation of the throttle device provided in the engine unit 21, the control unit 25 terminates the first assist control DA1. Therefore, regardless of the operation of the throttle device, the saddle-type vehicle 1 is comfortable for the driver in the range of rotational speed G lower than the idle speed range J.

[0194] 2. Second Embodiment 2-1. Schematic diagram 4 of the saddle-type vehicle 1 is a side view of the saddle-type vehicle 1 according to the second embodiment. The saddle-type vehicle 1 is, for example, a motorcycle. Note that the same reference numerals are used for components identical to those in the first embodiment, and detailed explanations are omitted.

[0195] The saddle-type vehicle 1 is equipped with an accelerator 10. The accelerator 10 is mounted on the handlebars 9. The driver of the saddle-type vehicle 1 operates the accelerator 10. When the amount of operation of the accelerator 10 increases, the speed of the saddle-type vehicle 1 increases.

[0196] The saddle-type vehicle 1 is equipped with a second sensor 11. The second sensor 11 is attached to the accelerator 10. The second sensor 11 detects the amount of operation of the accelerator 10.

[0197] The saddle-type vehicle 1 is equipped with a battery 19. The battery 19 stores electricity.

[0198] Battery 19 is classified as a rechargeable battery. Battery 19 can be charged, discharged, and recharged. Battery 19 can be recharged many times.

[0199] 2-2. Outline Configuration of Engine Unit 21 The engine unit 21 includes a motor 24A. The motor 24A also functions as a generator. The motor 24A has the functions of both a motor and a generator. Specifically, the motor 24A is configured to generate rotational power and electricity.

[0200] Motor 24A is an example of the motor of the present invention, and also an example of the generator of the present invention.

[0201] Motor 24A is a single component. Motor 24A is integrated with the generator. Motor 24A constitutes a motor-generator. In other words, motor 24A is classified as a motor-generator. A motor-generator is also called a starter-generator.

[0202] Hereafter, motor 24A will be referred to as "motor generator 24A" as appropriate.

[0203] The motor generator 24A is configured to generate rotational power from the electricity discharged from the battery 19. When the battery 19 discharges power to the motor generator 24A, the motor generator 24A generates rotational power. Specifically, the motor generator 24A converts the electricity discharged from the battery 19 into rotational power.

[0204] The motor generator 24A is configured to assist the rotation of the engine 22. When the motor generator 24A generates rotational power, it outputs rotational power to the engine 22.

[0205] The motor generator 24A is configured to generate electricity using the rotational power of the engine 22. When the engine 22 outputs rotational power to the motor generator 24A, the motor generator 24A generates electricity. Specifically, the motor generator 24A converts the rotational power output by the engine 22 into electricity.

[0206] The motor generator 24A is configured to charge the battery 19. When the motor generator 24A generates power, it supplies power to the battery 19.

[0207] The engine unit 21 further includes a power control unit 27. The power control unit 27 is electrically connected to the battery 19. The power control unit 27 is electrically connected to the motor generator 24A. The battery 19 and the motor generator 24A are electrically connected via the power control unit 27. The power control unit 27 sends power from the battery 19 to the motor generator 24A. The power control unit 27 sends power from the motor generator 24A to the battery 19.

[0208] The power control unit 27 controls the motor generator 24A.

[0209] Here, the state of the motor generator 24A that generates rotational power is called "assist mode EA". The state of the motor generator 24A that generates electricity is called "power generation mode EG". The power control unit 27 switches the motor generator 24A between assist mode EA and power generation mode EG. For example, the power control unit 27 switches the motor generator 24A between assist mode EA and power generation mode EG by adjusting the voltage applied to the motor generator 24A.

[0210] Furthermore, the power control unit 27 may adjust the voltage applied to the battery 19. The power control unit 27 may convert DC power to AC power. The power control unit 27 may convert AC power to DC power. For example, the power control unit 27 includes at least one of an inverter and a converter.

[0211] The control unit 25 controls the power control unit 27. By controlling the power control unit 27, the control unit 25 controls the motor generator 24A.

[0212] The control unit 25 performs the first assist control DA1. In the first assist control DA1, the control unit 25 causes the motor generator 24A to enter assist mode EA.

[0213] The control unit 25 performs power generation control DG. In power generation control DG, the control unit 25 causes the motor generator 24A to enter power generation mode EG.

[0214] Figure 5 is a partial cross-sectional view showing the configuration of the engine unit 21. The engine 22 is classified as, for example, a single-cylinder engine. The engine 22 is classified as, for example, a four-stroke engine.

[0215] The engine 22 comprises a crankcase 30 and a crankshaft 31. The crankshaft 31 is housed within the crankcase 30. The crankshaft 31 is supported by the crankcase 30. The crankshaft 31 rotates relative to the crankcase 30. The crankshaft 31 has an axis 31a. The crankshaft 31 extends in the direction of the axis 31a. The crankshaft 31 rotates about the axis 31a.

[0216] The crankshaft 31 outputs rotational power to the engine 22. The rotation of the crankshaft 31 corresponds to the rotation of the engine 22. The axis 31a corresponds to the rotation axis of the engine 22.

[0217] The engine 22 comprises a cylinder unit 32 and a piston 33. The cylinder unit 32 is connected to the crankcase 30. The piston 33 is located inside the cylinder unit 32. The piston 33 moves back and forth relative to the cylinder unit 32.

[0218] The cylinder unit 32 and piston 33 form a combustion chamber 34. The combustion chamber 34 is a space within the engine 22. The fuel-air mixture burns in the combustion chamber 34. The combustion of the fuel-air mixture generates exhaust gas in the combustion chamber 34.

[0219] The engine 22 includes a connecting rod 35. The connecting rod 35 is connected to the piston 33. The connecting rod 35 is connected to the crankshaft 31. When the piston 33 moves back and forth, the connecting rod 35 rotates the crankshaft 31.

[0220] The engine 22 is equipped with an intake port 36. The intake port 36 is formed within the cylinder unit 32. The intake port 36 communicates with the combustion chamber 34. The intake port 36 supplies the fuel-air mixture to the combustion chamber 34.

[0221] The engine 22 is equipped with an intake valve 37. The intake valve 37 is located in an intake port 36. The intake valve 37 opens and closes the intake port 36. When the intake valve 37 opens the intake port 36, the intake port 36 supplies a fuel-air mixture to the combustion chamber 34. When the intake valve 37 closes the intake port 36, the intake port 36 does not supply a fuel-air mixture to the combustion chamber 34.

[0222] The engine 22 is equipped with an exhaust port 38. The exhaust port 38 is formed within the cylinder unit 32. The exhaust port 38 communicates with the combustion chamber 34. The combustion chamber 34 discharges exhaust gas into the exhaust port 38.

[0223] The engine 22 is equipped with an exhaust valve 39. The exhaust valve 39 is located in the exhaust port 38. The exhaust valve 39 opens and closes the exhaust port 38. When the exhaust valve 39 opens the exhaust port 38, the combustion chamber 34 discharges exhaust gas into the exhaust port 38. When the exhaust valve 39 closes the exhaust port 38, the combustion chamber 34 does not discharge exhaust gas into the exhaust port 38.

[0224] The engine unit 21 is equipped with an ignition device 41. The ignition device 41 ignites the fuel-air mixture in the engine 22. The ignition device 41 is inserted into the combustion chamber 34. The ignition device 41 ignites the fuel-air mixture in the combustion chamber 34. When the fuel-air mixture is ignited, it burns. Combustion of the fuel-air mixture begins at the timing of its ignition.

[0225] The engine unit 21 is equipped with an intake pipe 42. The intake pipe 42 is connected to the engine 22. The intake pipe 42 is connected to the cylinder unit 32. The intake pipe 42 communicates with the intake port 36. The intake pipe 42 supplies air to the engine 22. The intake pipe 42 supplies air to the intake port 36.

[0226] The engine unit 21 is equipped with a throttle device 43. The throttle device 43 supplies air to the engine 22. The throttle device 43 is located on the intake pipe 42.

[0227] The throttle device 43 adjusts the amount of air flowing through the intake manifold 42. The amount of air flowing through the intake manifold 42 corresponds to the amount of air supplied to the engine 22. Therefore, the throttle device 43 adjusts the amount of air supplied to the engine 22. The amount of air supplied to the engine 22 is also called the intake air volume of the engine 22.

[0228] The configuration of the throttle device 43 is illustrated. For example, the throttle device 43 includes a throttle valve 44. The throttle valve 44 opens and closes the intake manifold 42. When the throttle valve 44 opens the intake manifold 42, the throttle device 43 supplies air to the engine 22. When the throttle valve 44 closes the intake manifold 42, the throttle device 43 does not supply air to the engine 22. By changing the position of the throttle valve 44, the throttle device 43 adjusts the amount of air supplied to the engine 22.

[0229] The throttle device 43 is classified as, for example, an electronically controlled throttle.

[0230] The engine unit 21 is equipped with a fuel injector 45. The fuel injector 45 supplies fuel to the engine 22. For example, the fuel injector 45 is attached to the intake manifold 42. The fuel injector 45 injects fuel into the intake manifold 42. The air and fuel form a mixture in the intake manifold 42.

[0231] The fuel injector 45 adjusts the amount of fuel supplied to the engine 22. For example, by changing the fuel injection time, the fuel injector 45 adjusts the amount of fuel supplied to the engine 22.

[0232] The engine 22 is equipped with an exhaust pipe 46. The exhaust pipe 46 is connected to the engine 22. The exhaust pipe 46 is connected to the cylinder unit 32. The exhaust pipe 46 communicates with the exhaust port 38. The exhaust pipe 46 carries exhaust gas.

[0233] The engine 22 is equipped with a transmission 47. The transmission 47 is connected to the crankshaft 31. The transmission 47 is connected, for example, to the first end of the crankshaft 31. The transmission 47 is, for example, a continuously variable transmission. The transmission 47 continuously changes the gear ratio, for example.

[0234] The transmission 47 comprises a primary pulley 48 and a belt 49. The primary pulley 48 is attached to one end of the crankshaft 31. The primary pulley 48 rotates integrally with the crankshaft 31. The primary pulley 48 rotates around the axis 31a. The belt 49 is placed over the primary pulley 48. The belt 49 transmits the rotational power of the crankshaft 31.

[0235] The primary pulley 48 has an effective diameter. The effective diameter of the primary pulley 48 is continuously variable. The belt 49 is placed over the primary pulley 48 at its effective diameter.

[0236] The motor-generator 24A is connected to the crankshaft 31. For example, the motor-generator 24A is connected to the second end of the crankshaft 31.

[0237] The motor generator 24A is, for example, located inside the crankcase 30.

[0238] The motor generator 24A includes a rotor 51. The rotor 51 is fixed to the crankshaft 31. The rotor 51 is attached, for example, to the second end of the crankshaft 31. The rotor 51 rotates integrally with the crankshaft 31. The rotor 51 rotates about the axis 31a.

[0239] The rotation axis of the rotor 51 corresponds to the rotation axis of the motor generator 24A. The rotation axis of the motor generator 24A is coaxial with axis 31a. The rotation axis of the motor generator 24A is coaxial with the rotation axis of the engine 22.

[0240] The rotor 51 comprises a rotor core 52 and permanent magnets 53. The rotor core 52 is connected to the crankshaft 31. The permanent magnets 53 are attached to the rotor core 52.

[0241] The motor generator 24A includes a stator 56. The stator 56 is supported, for example, by the crankcase 30. The stator 56 is fixed to the crankcase 30.

[0242] The stator 56 comprises a stator core 57 and windings 58. The windings 58 are attached to the stator core 57. Figure 5 shows the windings 58 in a simplified manner for convenience.

[0243] The rotational speed G of the engine 22 is equal to, for example, the rotational speed of the crankshaft 31. The rotational speed G is equal to, for example, the rotational speed of the motor generator 24A. The rotational speed G is equal to, for example, the rotational speed of the rotor 51.

[0244] For example, the first sensor 23 directly detects the rotational speed of the motor generator 24A. The first sensor 23 directly detects the rotational speed of the rotor 51. The first sensor 23 indirectly detects the rotational speed G of the engine 22.

[0245] The rotor 51 is provided with a plurality of protrusions 55. The protrusions 55 are fixed to the rotor 51. The protrusions 55 are attached to the rotor core 52.

[0246] The first sensor 23 detects the protrusion 55. As a result, the first sensor 23 detects the rotational speed G.

[0247] The first sensor 23 is provided, for example, inside the crankcase 30.

[0248] Figure 6 shows a motor generator 24A viewed from the direction of axis 31a. The stator 56 is positioned outside the crankshaft 31, for example. The rotor 51 is positioned outside the stator 56. The rotor 51 is classified as an outer rotor. The stator 56 is classified as an inner stator. The crankshaft 31 and rotor 51 rotate relative to the stator 56.

[0249] The rotor core 52 has an annular shape centered on the axis 31a. Each projection 55 is positioned on the outside of the rotor core 52. Multiple projections 55 are arranged at intervals in the circumferential direction around the axis 31a.

[0250] The first sensor 23 is positioned outside the rotor 51. The first sensor 23 is positioned outside the projection 55.

[0251] The permanent magnet 53 is positioned inside the rotor core 52. The permanent magnet 53 has an annular shape centered on the axis 31a. The permanent magnet 53 forms magnetic poles 54. The magnetic poles 54 include multiple north poles and multiple south poles. The north poles and south poles are arranged alternately in the circumferential direction around the axis 31a.

[0252] The stator core 57 is positioned inside the permanent magnet 53. The stator core 57 has a plurality of teeth 57a. Each tooth 57a extends radially from the axis 31a. The plurality of teeth 57a are arranged at intervals in the circumferential direction around the axis 31a. The winding 58 is wound around each tooth 57a.

[0253] The motor generator 24A is, for example, a three-phase motor. Although not shown in the diagram, the winding 58 includes the first phase winding, the second phase winding, and the third phase winding. The first, second, and third phases are also called the U phase, V phase, and W phase, respectively.

[0254] Figure 7 is a block diagram showing the electrical configuration of the engine unit 21. For example, the power control unit 27 includes a plurality (e.g., six) of switching units 28. The switching units 28 are connected to the battery 19. The switching units 28 are connected to the windings 58. Each switching unit 28 is connected to either the first phase winding, the second phase winding, or the third phase winding. Each switching unit 28 controls the passage / interruption of current between the battery 19 and the windings 58.

[0255] The switching unit 28 constitutes, for example, a bridge inverter. The switching unit 28 constitutes, for example, a three-phase bridge inverter. More specifically, the switching unit 28 constitutes three half-bridges. Each half-bridge includes two switching units 28 connected in series. The three half-bridges are connected in parallel to the battery 19. Each half-bridge is connected to the first phase winding, the second phase winding, and the third phase winding, respectively.

[0256] The switching unit 28 includes, for example, a semiconductor element. The switching unit 28 includes, for example, at least one of a Field Effect Transistor (FET), a thyristor, and an Insulated Gate Bipolar Transistor (IGBT).

[0257] The control unit 25 acquires the detection result from the second sensor 11.

[0258] The control unit 25 acquires the detection result from the first sensor 23.

[0259] The control unit 25 controls the ignition device 41. The control unit 25 controls the throttle device 43. The control unit 25 controls the fuel injection device 45.

[0260] For example, the control unit 25 controls the throttle device 43 based on the detection result of the second sensor 11.

[0261] For example, the control unit 25 controls the ignition device 41, throttle device 43, and fuel injection device 45 based on the detection result of the first sensor 23.

[0262] 2-3. Operation Example of Engine Unit 21 of the Second Embodiment Figure 8 is a flowchart showing the procedure for an operation example of the engine unit 21 of the second embodiment. In the following operation example, it is assumed that the engine 22 is rotating. It is assumed that the engine 22 is not in the process of starting. It is assumed that the engine 22 has already completed starting.

[0263] Step S11: Is the starting condition A met? The control unit 25 determines whether the starting condition A is met. If the starting condition A is met, proceed to step S12. Otherwise, repeat the process in step S11.

[0264] When the control unit 25 performs the processing in step S11, the control unit 25 performs power generation control DG.

[0265] Step S12: Power generation control DG ends. First assist control DA1 begins. The control unit 25 terminates power generation control DG. The control unit 25 starts first assist control DA1.

[0266] Step S13: Is termination condition B met? The control unit 25 determines whether termination condition B is met. If termination condition B is met, proceed to step S14. Otherwise, repeat the process in step S13.

[0267] Step S14: The first assist control DA1 ends. Power generation control DG begins. The control unit 25 terminates the first assist control DA1. The control unit 25 starts power generation control DG.

[0268] Here, the starting condition A depends on the rotational speed G. Therefore, the control unit 25 starts the first assist control DA1 based on the detection result of the first sensor 23.

[0269] Termination condition B depends on the rotation speed G. Therefore, the control unit 25 terminates the first assist control DA1 based on the detection result of the first sensor 23.

[0270] For example, termination condition B depends solely on the rotational speed G. Therefore, the control unit 25 terminates the first assist control DA1 based solely on the detection result of the first sensor 23.

[0271] For example, termination condition B depends on a first quantity K. The first quantity K is defined by the rotational speed G. The first quantity K is obtained from the detection result of the first sensor 23. Specifically, the first quantity K is the increase in rotational speed G due to combustion of the engine 22. More specifically, the first quantity K is the increase in rotational speed G due to one combustion cycle of the engine 22. The first quantity K is also called the "increase in rotational speed G Δne".

[0272] The control unit 22 acquires a first quantity K based on the detection result of the first sensor 23. The control unit 25 determines whether termination condition B is met based on the first quantity K. Then, the control unit 25 terminates the first assist control DA1 based on the first quantity K.

[0273] For example, termination condition B depends only on the first quantity K. Therefore, the control unit 25 terminates the first assist control DA1 based only on the first quantity K.

[0274] Let's explain a specific example of starting condition A. Starting condition A includes the first starting condition A1, as well as the second starting condition A2 and the third starting condition A3.

[0275] The first starting condition A1 is that "the rotational speed G is lower than the first threshold H1".

[0276] The second starting condition A2 is that "the rotational speed G is higher than the second threshold H2."

[0277] The third starting condition A3 is that "the FGM for the most recent power generation period is equal to or greater than the first reference time F1."

[0278] Here, "power generation period FG" is the period during which the motor generator 24A generates electricity. In other words, "power generation period FG" is the period during which power generation control DG is executed.

[0279] "The most recent power generation period FGM" is the power generation period FG after the most recent first assist control DA1M has finished. Specifically, "the most recent power generation period FG" is the period during which the motor generator 24A generated power after the most recent first assist control DA1M has finished. "The most recent first assist control DA1M" can be rephrased as the last first assist control DA1 that was performed.

[0280] "The most recent power generation period FGM" refers, for example, to the currently ongoing power generation period FG.

[0281] When all of the first, second, and third initiation conditions A1, A2, and A3 are met, initiation condition A is met. When at least one of the first, second, and third initiation conditions A1, A2, and A3 is not met, initiation condition A is not met.

[0282] Let's explain a specific example of termination condition B. For example, termination condition B includes a second termination condition B2.

[0283] The second termination condition B2 is "the first quantity K is equal to or greater than the standard quantity L."

[0284] When the second termination condition B2 is met, termination condition B is met. When the second termination condition B2 is not met, termination condition B is not met.

[0285] Figure 9 is a timing chart showing an example of the operation of the engine unit 21 of the second embodiment. The horizontal axis represents time T. The vertical axis represents the control performed by the control unit 25, the period during which the control by the control unit 25 is performed, and the rotational speed G.

[0286] The second threshold H2 is set in advance.

[0287] The second threshold H2 is lower than the first threshold H1.

[0288] The second threshold H2 is higher than zero.

[0289] The second threshold H2 is higher than half the value of the lower limit JL.

[0290] The second threshold H2 is higher than half the upper limit JU.

[0291] The second threshold H2 is, for example, higher than 600 rpm. The second threshold H2 is, for example, higher than 700 rpm. The second threshold H2 is, for example, higher than 800 rpm. The second threshold H2 is, for example, higher than 900 rpm.

[0292] The first reference time F1 is set in advance.

[0293] The amount of electricity generated by the motor generator 24A during the first reference time F1 is greater than the amount of electricity consumed during one first assist control DA1. In other words, the amount of electricity consumed during one first assist control DA1 is less than the amount of electricity generated by the motor generator 24A during the first reference time F1.

[0294] For example, the first reference time F1 is longer than the first assist period FA1.

[0295] For example, the first reference time F1 is 6 seconds.

[0296] From time T10 to time T15, the rotational speed G is greater than zero.

[0297] The period from time T10 to time T11, and the period from time T13 to time T14, constitute the first assist period FA1. During the first assist period FA1, the control unit 25 performs the first assist control DA1.

[0298] The operation of the engine unit 21 during the first assist period FA1 will be explained.

[0299] During the first assist period FA1, the control unit 25 controls the ignition device 41, throttle device 43, fuel injection device 45, and motor generator 24A based on the detection result of the first sensor 23. During the first assist period FA1, the control unit 25 controls the rotational speed G using the ignition device 41, throttle device 43, fuel injection device 45, and motor generator 24A.

[0300] During the first assist period FA1, the control unit 25 controls the ignition device 41 to ignite the air-fuel mixture in the engine 22.

[0301] For example, during the first assist period FA1, the control unit 25 controls the ignition device 41 to adjust the ignition timing of the air-fuel mixture in the engine 22.

[0302] During the first assist period FA1, the control unit 25 controls the throttle device 43 to supply air to the engine 22.

[0303] For example, during the first assist period FA1, the control unit 25 controls the throttle device 43 to adjust the amount of air supplied to the engine 22.

[0304] During the first assist period FA1, the control unit 25 controls the fuel injection device 45 to supply fuel to the engine 22.

[0305] During the first assist period FA1, the control unit 25 controls the fuel injection device 45 to adjust the amount of fuel supplied to the engine 22.

[0306] As described above, during the first assist period FA1, the control unit 25 performs the first assist control DA1. During the first assist control DA1, the control unit 25 maintains the motor generator 24A in assist mode EA. During the first assist control DA1, the control unit 25 supplies power from the battery 19 to the motor generator 24A. During the first assist control DA1, the control unit 25 causes the motor generator 24A to convert the power into rotational power. During the first assist control DA1, the control unit 25 causes the motor generator 24A to output the rotational power to the engine 22. During the first assist control DA1, the control unit 25 causes the motor generator 24A to assist the rotation of the engine 22.

[0307] In the first assist control DA1, the motor generator 24A assists the rotation of the engine 22.

[0308] During the first assist period FA1, the motor generator 24A consumes power. During the first assist period FA1, the motor generator 24A does not generate power.

[0309] Therefore, during the first assist period FA1, the balance of electricity decreases.

[0310] Here, "power balance" is, for example, the value obtained by subtracting the amount of power consumed by the motor generator 24A from the amount of power generated by the motor generator 24A. During the first assist period FA1, the amount of power consumed by the motor generator 24A increases. When the amount of power consumed by the motor generator 24A increases, the power balance decreases.

[0311] During the first assist period FA1, the battery 19 is discharged. During the first assist period FA1, the battery 19 is not charged.

[0312] Therefore, during the first assist period FA1, the power balance of the battery 19 decreases.

[0313] Here, "the power balance of battery 19" is, for example, the value obtained by subtracting the discharge amount of battery 19 from the charge amount of battery 19. During the first assist period FA1, the discharge amount of battery 19 increases. When the discharge amount of battery 19 increases, the power balance of battery 19 decreases.

[0314] The period from time T11 to time T13, and the period from time T14 to time T15, are the power generation period FG. During the power generation period FG, the control unit 25 performs power generation control DG.

[0315] The operation of the engine unit 21 during the power generation period FG will be explained.

[0316] During the power generation period FG, the control unit 25 controls the ignition device 41, throttle device 43, and fuel injection device 45 based on the detection results of the first sensor 23 and the second sensor 11. During the power generation period FG, the control unit 25 controls the rotational speed G using the ignition device 41, throttle device 43, and fuel injection device 45.

[0317] As described above, during the power generation period FG, the control unit 25 performs power generation control DG. During power generation control DG, the control unit 25 maintains the motor generator 24A in power generation mode EG. During power generation control DG, the control unit 25 causes the motor generator 24A to convert the rotational power of the engine 22 into electricity. During power generation control DG, the control unit 25 supplies power from the motor generator 24A to the battery 19. During power generation control DG, the control unit 25 causes the motor generator 24A to charge the battery 19.

[0318] During the power generation period FG, the motor generator 24A generates electricity. During the power generation period FG, the motor generator 24A does not assist the rotation of the engine 22.

[0319] During the power generation period FG, the amount of electricity generated by the motor generator 24A increases. When the amount of electricity generated by the motor generator 24A increases, the power balance increases. Therefore, during the power generation period FG, the power balance increases.

[0320] During the power generation period FG, the battery 19 is charged. During the power generation period FG, the battery 19 does not discharge.

[0321] During the power generation period FG, the amount of electricity charged to battery 19 increases. When the amount of electricity charged to battery 19 increases, the power balance of battery 19 increases. Therefore, during the power generation period FG, the power balance of battery 19 increases.

[0322] During the power generation period FG, the control unit 25 repeats the process in step S11.

[0323] Here, the first assist period FA1 from time T10 to time T11 will be appropriately referred to as "first assist period FA1a". The first assist control DA1 in the first assist period FA1a will be appropriately referred to as "first assist control DA1a". The first assist period FA1 from time T13 to time T14 will be appropriately referred to as "first assist period FA1b". The first assist control DA1 in the first assist period FA1b will be appropriately referred to as "first assist control DA1b".

[0324] The power generation period FG from time T11 to time T13 will be appropriately referred to as "power generation period FGa". The power generation control DG during power generation period FGa will be appropriately referred to as "power generation control DGa". The power generation period FG from time T14 to time T15 will be appropriately referred to as "power generation period FGb". The power generation control DG during power generation period FGb will be appropriately referred to as "power generation control DGb".

[0325] During the power generation period FGa, the control unit 25 performs the processing in step S11 as follows.

[0326] From time T11 to time T13, the control unit 25 acquires the rotation speed G based on the detection result of the first sensor 23.

[0327] From time T11 to time T13, the rotational speed G is higher than the first threshold H1. Therefore, the first condition A1 is not met from time T11 to time T13. At time T13, the rotational speed G is lower than the first threshold H1. Therefore, at time T13, the first starting condition A1 is met.

[0328] From time T11 to time T13, the rotational speed G is higher than the second threshold H2. Therefore, from time T11 to time T13, the second start condition A2 is satisfied.

[0329] During the period from time T11 to time T13, the control unit 25 treats the power generation period FGa as the "most recent power generation period FGM". During the period from time T11 to time T13, the control unit 25 treats the first assist control DA1a as the "most recent first assist control DA1M".

[0330] From time T11 to time T13, the control unit 25 measures the FGM for the most recent power generation period.

[0331] The period from time T11 to time T12 is equal to the first reference time F1. From time T11 to time T12, the most recent power generation period FGM is shorter than the first reference time F1. Therefore, from time T11 to time T12, the third start condition A3 is not met. From time T12 to time T13, the most recent power generation period FGM is greater than or equal to the first reference time F1. Therefore, from time T12 to time T13, the third start condition A3 is met.

[0332] From time T11 to time T13, at least one of the first start condition A1, the second start condition A2, and the third start condition A3 is not met. Therefore, from time T11 to time T13, start condition A is not met. Consequently, from time T11 to time T13, the control unit 25 does not terminate the power generation control DGa. From time T11 to time T13, the control unit 25 does not start the first assist control DA1b.

[0333] At time T13, all of the first start condition A1, the second start condition A2, and the third start condition A3 are met. Therefore, at time T13, start condition A is met. Consequently, at time T13, the control unit 25 terminates power generation control DGa. At time T13, the control unit 25 starts the first assist control DA1b.

[0334] During the first assist period FA1, the control unit 25 repeats the process of step S13. During the first assist period FA1b, the control unit 25 performs the process of step S13 as follows.

[0335] The control unit 25 acquires a first quantity K based on the detection result of the first sensor 23.

[0336] Although Figure 9 does not explicitly show the first quantity K, from time T13 to time T14, the first quantity K is smaller than the reference quantity L. Therefore, from time T13 to time T14, the second termination condition B2 is not met. Consequently, from time T13 to time T14, termination condition B is not met. Therefore, from time T13 to time T14, the control unit 25 does not terminate the first assist control DA1b. From time T13 to time T14, the control unit 25 does not start the power generation control DGb.

[0337] At time T14, the first quantity K is greater than or equal to the reference quantity L. Therefore, at time T14, the second termination condition B2 is satisfied. Thus, at time T14, termination condition B is satisfied. Consequently, at time T14, the control unit 25 terminates the first assist control DA1b. At time T14, the control unit 25 starts the power generation control DGb.

[0338] Figure 10 is a graph illustrating the first quantity K. The horizontal axis represents the crank angle N. The vertical axis represents the cycle, stroke, piston 33 position, detection result of the first sensor 23, and rotational speed G.

[0339] The crank angle N is the angle of the crankshaft 31 around the axis 31a. When the engine 22 completes one cycle, the crankshaft 31 rotates twice around the axis 31a. In one cycle, the crank angle N increases by 720 degrees.

[0340] Engine 22 repeats a cycle. Engine 22 burns in each cycle. Engine 22 burns once in each cycle. A cycle is also called a combustion cycle.

[0341] One cycle consists of four strokes. Specifically, one cycle consists of an expansion stroke, an exhaust stroke, an intake stroke, and a compression stroke. For example, during the expansion stroke, the crank angle N increases from 0 degrees to 180 degrees. During the exhaust stroke, the crank angle N increases from 180 degrees to 360 degrees. During the intake stroke, the crank angle N increases from 360 degrees to 540 degrees. During the compression stroke, the crank angle N increases from 540 degrees to 720 degrees.

[0342] During the expansion stroke, the engine burns. The expansion stroke is also called the combustion stroke. During the expansion stroke, the ignition device 41 ignites the fuel-air mixture in the combustion chamber 34. During the expansion stroke, the fuel-air mixture burns and expands.

[0343] The exhaust stroke is performed after the expansion stroke. During the exhaust stroke, exhaust gas is discharged from the combustion chamber 34 into the exhaust pipe 46.

[0344] The intake stroke is performed after the exhaust stroke. During the intake stroke, the fuel-air mixture is drawn into the combustion chamber 34. The mixture consists of air supplied by the throttle device 43 and fuel supplied by the fuel injector 45.

[0345] The compression stroke is performed after the intake stroke. During the compression stroke, the air-fuel mixture in the combustion chamber 34 is compressed by the piston 33.

[0346] In one cycle, the piston 33 moves back and forth twice between the top dead center M1 and the bottom dead center M2.

[0347] During the expansion stroke, the piston 33 moves from top dead center M1 to bottom dead center M2. During the exhaust stroke, the piston 33 moves from bottom dead center M2 to top dead center M1. During the intake stroke, the piston 33 moves from top dead center M1 to bottom dead center M2. During the compression stroke, the piston 33 moves from bottom dead center M2 to top dead center M1.

[0348] The detection result of the first sensor 23 is, for example, a plurality of signals P0, P1, ..., P23. In one cycle, the first sensor 23 generates a plurality of signals P0, P1, ..., P23. Specifically, when the crankshaft 31 rotates twice around the axis 31a, the first sensor 23 generates a plurality of signals P0, P1, ..., P23.

[0349] When signals P0, P1, ..., P23 are not distinguished, they are referred to as "signal P" as appropriate. When the first sensor 23 detects one protrusion 55, the first sensor 23 generates one signal P. Signal P is, for example, a pulse signal. Each signal P is associated with a time.

[0350] The rotational speed G is obtained based on the signal P.

[0351] The rotational speed G includes multiple instantaneous values ​​g0, g1, ..., g23.

[0352] All of the instantaneous values ​​g0, g1, ..., g23 are included in one cycle. The multiple instantaneous values ​​g0, g1, ..., g23 represent the change in rotational speed G during one cycle.

[0353] When instantaneous values ​​g0, g1, ..., g23 are not distinguished, they are appropriately referred to as "instantaneous value g". Each instantaneous value g is obtained based on signal P. For example, instantaneous value g6 is obtained based on at least two of signals P5, P6, and P7.

[0354] For example, the instantaneous value g0 indicates the rotational speed G at the moment combustion of the engine 22 begins. The instantaneous value g0 indicates the rotational speed G at the moment the expansion stroke begins. Hereafter, the instantaneous value g0 will be referred to as the "first instantaneous value g0".

[0355] For example, the instantaneous value g6 represents the rotational speed G at the moment when combustion of the engine 22 ends. The instantaneous value g6 represents the rotational speed G at the moment when the expansion stroke ends. Hereafter, the instantaneous value g6 will be referred to as the "second instantaneous value g6".

[0356] For example, the first quantity K is the increase from the first instantaneous value g0 to the second instantaneous value g6. For example, the first quantity K is the difference between the first instantaneous value g0 and the second instantaneous value g6. If the second instantaneous value g6 is higher than the instantaneous value g0, the first quantity K is positive. If the second instantaneous value g6 is lower than the instantaneous value g0, the first quantity K is negative.

[0357] The first instantaneous value g0 is obtained in each cycle. The second instantaneous value g6 is obtained in each cycle. The first quantity K is obtained in each cycle.

[0358] For example, when the first amount K is smaller than the standard amount L, it is not estimated that the engine 22 is burning properly. When the first amount K is smaller than the standard amount L, it is not estimated that the engine 22 is burning regularly.

[0359] For example, when the first amount K is equal to or greater than the standard amount L, it is presumed that the engine 22 is burning properly. When the first amount K is equal to or greater than the standard amount L, it is presumed that the engine 22 is burning regularly.

[0360] As described above, in Figure 9, from time T13 to time T14, the first quantity K is smaller than the reference quantity L. In Figure 9, at time T14, the first quantity K is greater than or equal to the reference quantity L.

[0361] The cases in which the control unit 25 starts the first assist control DA1 and the cases in which the control unit 25 does not start the first assist control DA1 are listed below.

[0362] When the rotational speed G is lower than the first threshold H1, and the rotational speed G is higher than the second threshold H2, and the most recent power generation period FGM is equal to or greater than the first reference time F1, the control unit 25 starts the first assist control DA1.

[0363] When the rotational speed G is greater than or equal to the first threshold H1, the control unit 25 does not start the first assist control DA1.

[0364] When the rotational speed G is less than or equal to the second threshold H2, the control unit 25 does not start the first assist control DA1. For example, even if the rotational speed G is lower than the first threshold, if the rotational speed G is less than or equal to the second threshold H2, the control unit 25 does not start the first assist control DA1.

[0365] For example, when the rotational speed G is lower than the first threshold H1 and higher than the second threshold H2, the control unit 25 starts the first assist control DA1.

[0366] The control unit 25 can start the first assist control DA1 only when the rotational speed G is lower than the first threshold H1 and higher than the second threshold H2.

[0367] When the most recent power generation period FGM is shorter than the first reference time F1, the control unit 25 does not start the first assist control DA1. Even if the rotational speed G is lower than the first threshold H1, the control unit 25 does not start the first assist control DA1 until the most recent power generation period FGM is equal to or greater than the first reference time F1.

[0368] For example, when the rotational speed G is lower than the first threshold H1, and the most recent power generation period FGM is equal to or greater than the first reference time F1, the control unit 25 starts the first assist control DA1.

[0369] The cases in which the control unit 25 terminates the first assist control DA1 and the cases in which the control unit 25 does not terminate the first assist control DA1 are listed below.

[0370] When the first quantity K is equal to or greater than the reference quantity L, the control unit 25 terminates the first assist control DA1. In other words, the control unit 25 terminates the first assist control DA1 on the condition that the first quantity K is equal to or greater than the reference quantity L.

[0371] When the first quantity K is smaller than the reference quantity L, the control unit 25 does not terminate the first assist control DA1.

[0372] 2-4. Effects of the Second Embodiment The second embodiment also produces similar effects to the first embodiment. For example, in the range of rotational speed G lower than the idle speed range J, the engine unit 21 is comfortable for the driver. In the range of rotational speed G lower than the idle speed range J, the saddle-type vehicle 1 is comfortable for the driver. Furthermore, the second embodiment produces the following effects.

[0373] When the rotational speed G is lower than the first threshold H1 and higher than the second threshold H2, the control unit 25 starts the first assist control DA1. The second threshold H2 is lower than the first threshold H1 and higher than zero. Therefore, when the rotational speed G is lower than the idle speed range J and higher than zero, the first assist control DA1 starts. Thus, in the range of rotational speed G that is lower than the idle speed range J and higher than zero, the first assist control DA1 assists the rotation of the engine 22. Consequently, in the range of rotational speed G that is lower than the idle speed range J and higher than zero, the engine unit 21 is comfortable for the driver. In other words, when the engine 22 rotates in the range of rotational speed G that is lower than the idle speed range J, the engine unit 21 is comfortable for the driver.

[0374] When the rotational speed G is less than or equal to the second threshold H2, the control unit 25 does not start the first assist control DA1. Therefore, when the rotational speed G is zero, the first assist control DA1 does not start. In other words, the first assist control DA1 focuses on the range of rotational speed G that is higher than zero and lower than the idle speed range J. Therefore, in the range of rotational speed G that is lower than the idle speed range J and higher than zero, the first assist control DA1 effectively assists the rotation of the engine 22. Consequently, it is easy for the first assist control DA1 to appropriately control the rotational speed G in the range of rotational speed G that is lower than the idle speed range J and higher than zero. In the range of rotational speed G that is lower than the idle speed range J and higher than zero, it is easy for the first assist control DA1 to improve the comfort of the engine unit 21 for the driver.

[0375] The control unit 25 can start the first assist control DA1 only when the rotational speed G is lower than the first threshold H1 and higher than the second threshold H2. Therefore, in the range of rotational speed G that is lower than the idle speed range J and higher than zero, the first assist control DA1 effectively assists the rotation of the engine 22. Thus, it is easy for the first assist control DA1 to appropriately control the rotational speed G in the range of rotational speed G that is lower than the idle speed range J and higher than zero. It is easy for the first assist control DA1 to improve the comfort of the engine unit 21 for the driver in the range of rotational speed G that is lower than the idle speed range J and higher than zero.

[0376] The second threshold H2 is higher than half the lower limit JL. Therefore, when the rotational speed G is lower than the idle speed range J and higher than half the lower limit JL, the control unit 25 starts the first assist control DA1. Thus, in the range of rotational speed G that is lower than the idle speed range J and higher than half the lower limit, the first assist control DA1 assists the rotation of the engine 22. Consequently, in the range of rotational speed G that is lower than the idle speed range J and higher than half the lower limit, the engine unit 21 is comfortable for the driver.

[0377] The second threshold H2 is higher than half the upper limit JU. Therefore, when the rotational speed G is lower than the idle speed range J and higher than half the upper limit JU, the control unit 25 starts the first assist control DA1. Thus, in the range of rotational speed G that is lower than the idle speed range J and higher than half the upper limit JU, the first assist control DA1 assists the rotation of the engine 22. Consequently, in the range of rotational speed G that is lower than the idle speed range J and higher than half the upper limit JU, the engine unit 21 is comfortable for the driver.

[0378] The saddle-type vehicle 1 is equipped with a motor generator 24A. The motor generator 24A is configured to generate electricity by the rotation of the engine 22. Even if the rotational speed G is lower than the first threshold H1, the control unit 25 does not start the first assist control DA1 until the most recent power generation period FGM is equal to or greater than the first reference time F1. Therefore, when the most recent power generation period FGM is shorter than the first reference time F1, the control unit 25 does not start the first assist control DA1. Thus, the motor generator 24A generates electricity appropriately during the most recent power generation period FGM. Consequently, when the first assist controls DA1a and DA1b are executed, the power balance does not decrease continuously. For example, power generation control DGaa is performed after the first assist control DA1a is completed and before the first assist control DA1b is started. Therefore, after the first assist control DA1a is completed and before the first assist control DA1b is started, the power balance increases.

[0379] When the rotational speed G is lower than the first threshold H1, and the most recent power generation period FGM is equal to or greater than the first reference time F1, the control unit 25 starts the first assist control DA1. As a result, the motor generator 24A generates a sufficient amount of power during the most recent power generation period FGM. Multiple instances of the first assist control DA1 are executed with an interval of at least the first reference time F1 between them.

[0380] The amount of power consumed in one first assist control DA1 is less than the amount of power generated by the motor generator 24A during the first reference time F1. Therefore, the motor generator 24A generates a sufficient amount of power during the most recent power generation period FGM.

[0381] The motor generator 24A is configured to generate rotational power using electricity discharged from the battery 19. The motor generator 24A is configured to charge the battery 19. Therefore, it is easy for the motor generator 24A to generate rotational power. Thus, it is easy for the motor generator 24A to rotate the engine 22.

[0382] In the first assist control DA1, the battery 19 discharges to the motor generator 24A. During the power generation period, the battery 19 is charged by the motor generator 24A. As described above, the control unit 25 does not start the first assist control DA1 until the most recent power generation period FGM is equal to or greater than the first reference time F1. Therefore, when two first assist control DA1s are executed, the power balance of the battery 19 does not decrease continuously. For example, power generation control DGa is performed after the first assist control DA1a has finished and before the first assist control DA1b has started. As a result, the power balance of the battery 19 increases after the first assist control DA1a has finished and before the first assist control DA1b has started.

[0383] The motor-generator 24A also functions as a generator. Therefore, it is easy to miniaturize the entire motor and generator unit.

[0384] The motor-generator 24A is integrated with the generator. Therefore, it is easy to miniaturize the entire motor and generator unit.

[0385] The control unit 25 acquires a first quantity K based on the detection result of the first sensor 23. Based on the first quantity K, the control unit 25 terminates the first assist control DA1. Therefore, it is easy to terminate the first assist control DA1 at an appropriate timing.

[0386] When the first quantity K is equal to or greater than the reference quantity L, the control unit 25 terminates the first assist control DA1. Therefore, it is easy to terminate the first assist control DA1 at an appropriate timing.

[0387] The rotational speed G includes a first instantaneous value g0 and a second instantaneous value g6. The first instantaneous value g0 is the rotational speed G at the moment combustion of the engine 22 begins. The second instantaneous value g6 is the rotational speed G at the moment combustion of the engine 22 ends. The first quantity K is the increase from the first instantaneous value g0 to the second instantaneous value g6. Therefore, obtaining the first quantity K is easy.

[0388] Engine 22 repeats cycles. Engine 22 burns in each cycle. The first instantaneous value g0 and the second instantaneous value g6 are obtained during each cycle. Therefore, it is easy to obtain the first quantity K in each cycle.

[0389] The engine unit 21 is equipped with a fuel injector 45. During the first assist period FA1, the control unit 25 controls the fuel injector 45 to supply fuel to the engine 22. Therefore, during the first assist period FA1, the control unit 25 controls the fuel injector 45 to rotate the engine 22. Thus, during the first assist period FA1, the control unit 25 causes the fuel injector 45 to rotate the engine 22 and also causes the motor generator 24A to assist in the rotation of the engine 22. Consequently, during the first assist period FA1, the control unit 25 controls the rotational speed G more appropriately.

[0390] During the first assist period FA1, the control unit 25 controls the fuel injection device 45 to adjust the amount of fuel supplied to the engine 22. Therefore, it is easy for the control unit 25 to more appropriately control the rotational speed G during the first assist period FA1.

[0391] The engine unit 21 is equipped with a throttle device 43. During the first assist period FA1, the control unit 25 controls the throttle device 43 to supply air to the engine 22. Therefore, during the first assist period FA1, the control unit 25 controls the throttle device to rotate the engine 22. Thus, during the first assist period FA1, the control unit 25 causes the throttle device 43 to rotate the engine 22 and also causes the motor generator 24A to assist in the rotation of the engine 22. Consequently, during the first assist period FA1, the control unit 25 controls the rotational speed G more appropriately.

[0392] During the first assist period FA1, the control unit 25 controls the throttle device 43 to adjust the amount of air supplied to the engine 22. Therefore, it is easy for the control unit 25 to control the rotational speed G more appropriately during the first assist period FA1.

[0393] The engine unit 21 is equipped with an ignition device 41. During the first assist period FA1, the control unit 25 controls the ignition device 41 to ignite the air-fuel mixture in the engine 22. Therefore, during the first assist period FA1, the control unit 25 controls the ignition device 41 to rotate the engine 22. Thus, during the first assist period FA1, the control unit 25 causes the ignition device 41 to rotate the engine 22 and also causes the motor generator 24A to assist in the rotation of the engine 22. Consequently, during the first assist period FA1, the control unit 25 controls the rotational speed G more appropriately.

[0394] During the first assist period FA1, the control unit 25 controls the ignition device 41 to adjust the ignition timing of the air-fuel mixture in the engine 22. Therefore, it is easy for the control unit 25 to control the rotational speed G more appropriately during the first assist period FA1.

[0395] 3. Third Embodiment 3-1. The schematic diagram 11 of the saddle-type vehicle 1 is a side view of the saddle-type vehicle 1 according to the third embodiment. The saddle-type vehicle 1 is, for example, a motorcycle. Note that components identical to those in the first or second embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0396] The saddle-type vehicle 1 is equipped with a main switch 12. The main switch 12 is mounted, for example, on the handlebar 9. The main switch 12 is operated by the driver. The driver switches the main switch 12 between the ON state and the OFF state. When the main switch 12 is in the ON state, the motor generator 24A is electrically connected to the battery 19. When the main switch 12 is in the OFF state, the motor generator 24A is electrically disconnected from the battery 19.

[0397] The saddle-type vehicle 1 is equipped with an engine start switch 13. The engine start switch 13 is mounted, for example, on the handlebar 9. The engine start switch 13 is operated by the driver. The driver switches the engine start switch 13 between the ON state and the OFF state. When the engine start switch 13 is in the ON state, the control unit 25 starts the engine 22 using the motor generator 24A. When the engine start switch 13 is in the OFF state, the control unit 25 does not start the engine 22.

[0398] The saddle-type vehicle 1 is equipped with an engine stop switch 14. The engine stop switch 14 is mounted, for example, on the handlebar 9. The engine stop switch 14 is operated by the driver. The driver switches the engine stop switch 14 between the ON state and the OFF state. When the engine stop switch 14 is in the ON state, the control unit 25 stops the engine 22. When the engine stop switch 14 is in the OFF state, the control unit 25 does not stop the engine 22.

[0399] The saddle-type vehicle 1 is equipped with a kick-start device 61. The kick-start device 61 is for starting the engine 22. For example, when the power from the battery 19 is not sufficient to start the engine 22, the kick-start device 61 is used to start the engine 22. The kick-start device 61 includes, for example, a kick pedal. The kick-start device 61 is connected to, for example, the engine 22. The driver of the saddle-type vehicle 1 operates the kick-start device 61.

[0400] The saddle-type vehicle 1 is equipped with a stand 62. The stand 62 is movable between a retracted position and an upright position. Figure 11 shows the stand 62 in the retracted position with a solid line. Figure 11 shows the stand 62 in the upright position with a dashed line. When the saddle-type vehicle 1 is moving, the stand 62 is in the retracted position. When the saddle-type vehicle 1 is stopped, the stand 62 is in the upright position. When the stand 62 is in the upright position, the stand 62 keeps the saddle-type vehicle 1 in an upright position. The upright position is also called the deployed position. The stand 62 is supported, for example, by the vehicle body 3. The driver of the saddle-type vehicle 1 operates the stand 62.

[0401] The saddle-type vehicle 1 is equipped with a third sensor 63. The third sensor 63 detects the position of the stand 62. The third sensor 63 is, for example, attached to the stand 62.

[0402] The saddle-type vehicle 1 is equipped with a fourth sensor 64. The fourth sensor 64 detects the speed of the saddle-type vehicle 1. The fourth sensor 64 is attached, for example, to the rear wheel 18.

[0403] The engine unit 21 includes a fifth sensor 65. The fifth sensor 65 detects the temperature of the engine 22. The fifth sensor 65 is, for example, mounted on the engine 22.

[0404] The engine unit 21 includes a sixth sensor 66. The sixth sensor 66 detects the state of the motor generator 24A. The state of the motor generator 24A includes, for example, at least one of the voltage of the motor generator 24A, the current of the motor generator 24A, and the temperature of the motor generator 24A. The sixth sensor 66 is, for example, mounted on the motor generator 24A.

[0405] The saddle-type vehicle 1 is equipped with a seventh sensor 67. The seventh sensor 67 detects the state of the battery 19. The state of the battery 19 includes, for example, at least one of the voltage of the battery 19, the current of the battery 19, and the temperature of the battery 19. The seventh sensor 67 is, for example, attached to the battery 19.

[0406] Figure 12 is a block diagram showing the electrical configuration of the engine unit 21.

[0407] The control unit 25 acquires the detection result from the second sensor 11.

[0408] The control unit 25 acquires the status of the main switch 12. The control unit 25 acquires the status of the engine start switch 13. The control unit 25 acquires the status of the engine stop switch 14.

[0409] The control unit 25 acquires the detection result from the first sensor 23.

[0410] The control unit 25 acquires the detection result of the third sensor 63. The control unit 25 acquires the detection result of the fourth sensor 64. The control unit 25 acquires the detection result of the fifth sensor 65. The control unit 25 acquires the detection result of the sixth sensor 66. The control unit 25 acquires the detection result of the seventh sensor 67.

[0411] The control unit 25 controls the ignition device 41. The control unit 25 controls the throttle device 43. The control unit 25 controls the fuel injection device 45.

[0412] In addition to the first assist control DA1 and power generation control DG, the control unit 25 performs the second assist control DA2. When the driver turns on the engine start switch 13, the control unit 25 starts the second assist control DA2 to start the engine 22. That is, when the engine 22 starts, the control unit 25 performs the second assist control DA2. In the second assist control DA2, the control unit 25 puts the motor generator 24A into assist mode EA. In the second assist control DA2, the control unit 25 causes the motor generator 24A to rotate the engine 22. In the second assist control DA2, the control unit 25 starts the engine 22 using the motor generator 24A.

[0413] In the second assist control DA2, the battery 19 discharges power to the motor generator 24A. In the second assist control DA2, the motor generator 24A converts the power discharged from the battery 19 into rotational power. In the second assist control DA2, the motor generator 24A outputs the rotational power to the engine 22, causing the engine 22 to start rotating.

[0414] When the rotational speed G is zero, the control unit 25 can start the second assist control DA2. When the rotational speed G is higher than the second threshold H2, the control unit 25 does not start the second assist control DA2.

[0415] When the second assist control DA2 is being executed, the control unit 25 does not start the first assist control DA1. While the second assist control DA2 is being executed, the first assist control DA1 is not executed. After the second assist control DA2 has finished, the execution of the first assist control DA1 is permitted.

[0416] When the first assist control DA1 is being executed, the control unit 25 does not start the second assist control DA2.

[0417] 3-2. Example of operation of the engine unit 21 of the third embodiment. For convenience, refer to Figure 8.

[0418] Steps S11 and S12: If starting condition A is met, the control unit 25 terminates the power generation control DG and starts the first assist control DA1.

[0419] Steps S13 and S14: If termination condition B is met, the control unit 25 terminates the first assist control DA1 and starts the power generation control DG.

[0420] Figure 13 is a table showing specific examples of starting condition A. Starting condition A includes the first to sixth starting conditions A1-A6. For example, starting condition A is satisfied when all of the first to sixth starting conditions A1-A6 are met. Starting condition A is not satisfied when at least one of the first to sixth starting conditions A1-A6 is not met.

[0421] The first starting condition A1 is that "the rotational speed G is lower than the first threshold H1".

[0422] The second starting condition A2 is that "the rotational speed G is higher than the second threshold H2."

[0423] The third starting condition A3 is that "the FGM for the most recent power generation period is equal to or greater than the first reference time F1."

[0424] The fourth starting condition A4 is that "the control unit 25 does not perform engine stop control DS."

[0425] The fifth starting condition A5 is "the first operation has been performed."

[0426] The sixth starting condition, A6, is "the specified equipment is functioning correctly."

[0427] The fourth starting condition A4 is explained below. Engine stop control DS is a control for stopping the engine 22. When the control unit 25 performs engine stop control DS, the control unit 25 stops the rotation of the engine 22. When the control unit 25 does not perform engine stop control DS, the fourth starting condition A4 is satisfied. When the control unit 25 performs engine stop control DS, the fourth starting condition A4 is not satisfied.

[0428] For example, the engine stop control DS includes at least one of the forced stop control DS1 and the stop idling control DS2. When the control unit 25 does not perform the forced stop control DS1 and the control unit 25 does not perform the stop idling control DS2, the fourth start condition A4 is satisfied. When the control unit 25 performs the forced stop control DS1, the fourth start condition A4 is not satisfied. When the control unit 25 performs the stop idling control DS2, the fourth start condition A4 is not satisfied.

[0429] For example, when no abnormality related to the engine 22 occurs, the control unit 25 does not perform the forced stop control DS1. When an abnormality related to the engine 22 occurs, the control unit 25 performs the forced stop control DS1. "Abnormality related to the engine 22" includes, for example, at least one of the following: an abnormality of the first sensor 23, an abnormality of the ignition device 41, an abnormality of the throttle device 43, and an abnormality of the fuel injection device 45.

[0430] For example, based on the start-stop system, the control unit 25 performs stop-idling control DS2.

[0431] The following are examples of conditions C1-C4 for the stop idling control DS2. For example, if at least some of conditions C1-C4 are not met, the control unit 25 does not perform stop idling control. If all of conditions C1-C4 are met, the control unit 25 performs stop idling control.

[0432] Condition C1 is that "the rotational speed G is within the idle speed range J".

[0433] Condition C2 is "the amount of operation performed by accelerator 10 is zero."

[0434] Condition C3 is "the speed of the saddle-type vehicle 1 is zero."

[0435] Condition C4 is "the temperature of the engine 22 is equal to or above the first reference temperature."

[0436] The control unit 25 determines whether condition C1 is met based on the detection result of the first sensor 23. The control unit 25 determines whether condition C2 is met based on the detection result of the second sensor 12. The control unit 25 determines whether condition C3 is met based on the detection result of the fourth sensor 64. The control unit 25 determines whether condition C4 is met based on the detection result of the fifth sensor 65.

[0437] The fifth starting condition A5 is explained. The first operation is an operation performed by the driver. When the driver performs the first operation, it is presumed that the driver will not stop the rotation of the engine 22. In other words, the first operation is an operation performed by the driver to keep the engine 22 rotating. When the first operation is performed, the fifth starting condition A5 is satisfied. When the first operation is not performed, the fifth starting condition A5 is not satisfied.

[0438] For example, the first operation includes at least one of turning on the main switch 12, turning off the engine stop switch 14, and positioning the stand 62 in the retracted position.

[0439] For example, the fifth starting condition A5 is satisfied when the main switch 12 is in the ON position, the engine stop switch 14 is in the OFF position, and the stand 62 is in the retracted position. The fifth starting condition A5 is not satisfied when the main switch 12 is not in the ON position. The fifth starting condition A5 is not satisfied when the engine stop switch 14 is not in the OFF position. The fifth starting condition A5 is not satisfied when the stand 62 is not in the retracted position.

[0440] The control unit 25 determines whether the main switch 12 is in the ON state based on the state of the main switch 12. The control unit 25 determines whether the engine stop switch 14 is in the OFF state based on the state of the engine stop switch 14. The control unit 25 determines whether the stand 62 is in the retracted position based on the detection result of the third sensor 63.

[0441] The sixth starting condition A6 is explained below. When the specified equipment is functioning normally, the sixth starting condition A6 is met. When the specified equipment is not functioning normally, the sixth starting condition A6 is not met.

[0442] For example, the specified equipment includes at least one of a motor generator 24A and a battery 19. For example, when the motor generator 24A is functioning normally and the battery 19 is functioning normally, the sixth starting condition A6 is satisfied. When the motor generator 24A is not functioning normally, the sixth starting condition A6 is not satisfied. When the battery 19 is not functioning normally, the sixth starting condition A6 is not satisfied.

[0443] For example, if the voltage of the motor generator 24A is normal, the current of the motor generator 24A is normal, and the temperature of the motor generator 24A is normal, the control unit 25 determines that the motor generator 24A is normal. The control unit 25 determines whether or not the motor generator 24A is normal based on the detection result of the sixth sensor 66.

[0444] For example, if the voltage of the battery 19 is normal, the current of the battery 19 is normal, and the temperature of the battery 19 is normal, the control unit 25 determines that the battery 19 is normal. The control unit 25 determines whether or not the battery 19 is normal based on the detection result of the seventh sensor 67.

[0445] For example, when the engine 22 is started by the motor generator 24A instead of the kickstarter 61, the control unit 25 determines that the battery 19 and motor generator 24A are functioning normally. In this case, the control unit 25 determines whether the battery 19 and motor generator 24A are functioning normally based on the detection result of the first sensor 23 and the state of the engine start switch 13. Specifically, the control unit 25 identifies when the engine 22 was started based on the detection result of the first sensor 23. Furthermore, the control unit 25 identifies whether the engine start switch 13 was in the ON position when the engine 22 was started. As a result, if the engine start switch 13 was in the ON position when the engine 22 was started, it is presumed that the engine 22 was started by the motor generator 24A. Therefore, if the engine start switch 13 was in the ON position when the engine 22 was started, the control unit 25 determines that the battery 19 and motor generator 24A are functioning normally. If the engine start switch 13 was not in the ON position when the engine 22 was started, it is presumed that the engine 22 was started by the kickstarter 61. Therefore, if the engine start switch 13 is not in the ON position when the engine 22 is started, the control unit 25 determines that at least one of the battery 19 and the motor generator 24A is not functioning properly.

[0446] The cases in which the control unit 25 starts the first assist control DA1 and the cases in which the control unit 25 does not start the first assist control DA1 are listed below.

[0447] When starting condition A is met, the control unit 25 starts the first assist period FA1. For example, when all of the first to sixth starting conditions A1 to A6 are met, the control unit 25 starts the first assist period FA1.

[0448] If starting condition A is not met, the control unit 25 will not start the first assist period FA1. For example, if at least one of the first to sixth starting conditions A1 to A6 is not met, the control unit 25 will not start the first assist period FA1.

[0449] When the rotational speed G is equal to or higher than the first threshold value H1, the control unit 25 does not start the first assist control DA1.

[0450] When the rotational speed G is equal to or lower than the second threshold value H2, the control unit 25 does not start the first assist control DA1.

[0451] When the most recent power generation period FGM is shorter than the first reference time F1, the control unit 25 does not start the first assist control DA1.

[0452] When the control unit 25 performs the engine stop control DS, the control unit 25 does not start the first assist control DA1.

[0453] For example, even when the rotational speed G is lower than the first threshold value H1, when the control unit 25 performs the engine stop control DS, the control unit 25 does not start the first assist control DA1.

[0454] For example, when the rotational speed G is lower than the first threshold value H1 and the control unit 25 does not perform the engine stop control DS, the control unit 25 starts the first assist control DA1.

[0455] When the first operation is not being performed, the control unit 25 does not start the first assist control DA1.

[0456] Even when the rotational speed G is lower than the first threshold value H1, when the first operation is not being performed, the control unit 25 does not start the first assist control DA1.

[0457] For example, when the rotational speed G is lower than the first threshold value H1 and the first operation is being performed, the control unit 25 starts the first assist control DA1.

[0458] When a predetermined device is not normal, the control unit 25 does not start the first assist control DA1.

[0459] Even when the rotational speed G is lower than the first threshold value H1, when a predetermined device is not normal, the control unit 25 does not start the first assist control DA1.

[0460] For example, when the rotational speed G is lower than the first threshold value H1 and a predetermined device is normal, the control unit 25 starts the first assist control DA1.

[0461] Furthermore, while the second assist control DA2 is being executed, the control unit 25 does not start the first assist control DA1. After the second assist control DA2 is completed, the control unit 25 can start the first assist control DA1.

[0462] Figure 14 is a table showing specific examples of termination condition B. Termination condition B includes the first to sixth starting conditions B1 to B6. For example, termination condition B is satisfied when at least one of the first to sixth termination conditions B1 to B6 is satisfied. For example, termination condition B is not satisfied when none of the first to sixth termination conditions B1 to B6 are satisfied.

[0463] The first termination condition B1 is that "the rotational speed G is higher than the third threshold H3."

[0464] The second termination condition B2 is "the first quantity K is equal to or greater than the standard quantity L."

[0465] The third termination condition B3 is that "the first assist period FA1 is longer than the second reference time F2."

[0466] The fourth termination condition B4 is "the control unit 25 performs engine stop control DS".

[0467] The fifth termination condition, B5, is "the second operation is performed."

[0468] The sixth termination condition, B6, is "the specified equipment is malfunctioning."

[0469] The third termination condition B3 is explained below. The third termination condition B3 is satisfied when the first assistance period FA1 is less than or equal to the second reference time F2. The third termination condition B3 is satisfied when the first assistance period FA1 is longer than the second reference time F2.

[0470] The second reference time F2 is set in advance.

[0471] The second reference time F2 is shorter than the first reference time F1.

[0472] The second reference time F2 is substantially equal to, for example, the time it takes for the engine 22 to complete five cycles.

[0473] The second reference time F2 is, for example, 0.5 seconds or more.

[0474] The second reference time F2 is, for example, 2 seconds or less.

[0475] The second reference time F2 is, for example, 1 second.

[0476] The second reference time F2 is, for example, 0.6 seconds.

[0477] The fourth termination condition B4 is explained below. When the control unit 25 performs engine stop control DS, the fourth termination condition B4 is satisfied. When the control unit 25 does not perform engine stop control DS, the fourth termination condition B4 is not satisfied.

[0478] For example, the engine stop control DS includes at least one of the forced stop control DS1 and the stop idling control DS2. When the control unit 25 performs the forced stop control DS1, the fourth termination condition B4 is satisfied. When the control unit 25 performs the stop idling control DS2, the fourth termination condition B4 is satisfied. When the control unit 25 does not perform the forced stop control DS1 and does not perform the stop idling control DS2, the fourth termination condition B4 is not satisfied.

[0479] The fifth termination condition B5 is explained. The second operation is an operation performed by the driver. When the driver performs the second operation, it is presumed that the driver will stop the rotation of the engine 22. In other words, the second operation is an operation performed by the driver to stop the engine 22. When the second operation is performed, the fifth termination condition B5 is satisfied. When the second operation is not performed, the fifth termination condition B5 is not satisfied.

[0480] For example, the second operation includes at least one of turning the main switch 12 to the OFF position, turning the engine stop switch 14 to the ON position, and positioning the stand 62 in the upright position.

[0481] For example, when the main switch 12 is in the off state, the fifth termination condition B5 is satisfied. When the engine stop switch 14 is in the on state, the fifth termination condition B5 is satisfied. When the stand 62 is in the upright position, the fifth termination condition B5 is satisfied. When the main switch 12 is not in the off state, the engine stop switch 14 is not in the on state, and the stand 62 is not in the upright position, the fifth termination condition B5 is not satisfied.

[0482] The control unit 25 determines whether the main switch 12 is in the off state based on the state of the main switch 12. The control unit 25 determines whether the engine stop switch 14 is in the on state based on the state of the engine stop switch 14. The control unit 25 determines whether the stand 62 is in the upright position based on the detection result of the third sensor 63.

[0483] The sixth termination condition B6 will be described. When a predetermined device is abnormal, the sixth termination condition B6 is satisfied. When the predetermined device is not abnormal, the sixth termination condition B6 is not satisfied.

[0484] The predetermined device includes, for example, at least one of the motor generator 24A and the battery 19. For example, when the motor generator 24A is abnormal, the sixth termination condition B6 is satisfied. When the battery 19 is abnormal, the sixth termination condition B6 is satisfied. When the motor generator 24A is not abnormal and the battery 19 is not abnormal, the sixth termination condition B6 is not satisfied.

[0485] For example, when the voltage of the motor generator 24A is abnormal, the control unit 25 determines that the motor generator 24A is abnormal. When the current of the motor generator 24A is abnormal, the control unit 25 determines that the motor generator 24A is abnormal. When the temperature of the motor generator 24A is abnormal, the control unit 25 determines that the motor generator 24A is abnormal. The control unit 25 determines whether the motor generator 24A is abnormal based on the detection result of the sixth sensor 66.

[0486] For example, if the voltage of battery 19 is abnormal, the control unit 25 determines that battery 19 is abnormal. If the current of battery 19 is abnormal, the control unit 25 determines that battery 19 is abnormal. If the temperature of battery 19 is abnormal, the control unit 25 determines that battery 19 is abnormal. The control unit 25 determines whether or not battery 19 is abnormal based on the detection result of the seventh sensor 67.

[0487] The cases in which the control unit 25 terminates the first assist control DA1 and the cases in which the control unit 25 does not terminate the first assist control DA1 are listed below.

[0488] When termination condition B is met, the control unit 25 terminates the first assist period FA1. For example, when at least one of the first to sixth termination conditions B1 to B6 is met, the control unit 25 terminates the first assist period FA1.

[0489] If termination condition B is not met, the control unit 25 does not terminate the first assist period FA1. For example, if none of the first to sixth termination conditions B1 to B6 are met, the control unit 25 does not terminate the first assist period FA1.

[0490] When the rotational speed G is higher than the third threshold H3, the control unit 25 terminates the first assist control DA1.

[0491] When the first quantity K is equal to or greater than the reference quantity L, the control unit 25 terminates the first assist control DA1.

[0492] When the first assist period FA1 is longer than the second reference time F2, the control unit 25 terminates the first assist control DA1.

[0493] When the control unit 25 performs engine stop control DS, the control unit 25 terminates the first assist control DA1.

[0494] When the second operation is performed, the control unit 25 terminates the first assist control DA1.

[0495] When a specified device malfunctions, the control unit 25 terminates the first assist control DA1.

[0496] 3-3. Effects of the Third Embodiment The third embodiment also provides similar effects to the first or second embodiment. For example, in the range of rotational speed G lower than the idle speed range J, the engine unit 21 is comfortable for the driver. In the range of rotational speed G lower than the idle speed range J, the saddle-type vehicle 1 is comfortable for the driver. Furthermore, the third embodiment provides the following effects.

[0497] Even when the rotational speed G is lower than the first threshold H1, the control unit 25 does not start the first assist control DA1 when it performs engine stop control DS. Therefore, the first assist control DA1 does not interfere with the execution of engine stop control DS. The first assist control DA1 allows the execution of engine stop control DS.

[0498] When the rotational speed G is lower than the first threshold H1, and the control unit 25 does not perform engine stop control DS, the control unit 25 starts the first assist control DA1. Therefore, the first assist control DA1 starts at an appropriate timing.

[0499] For example, the engine stop control DS includes the forced stop control DS1. Therefore, the first assist control does not interfere with the execution of the forced stop control. Thus, the first assist control allows for the smooth execution of the forced stop control.

[0500] For example, the engine stop control DS includes the stop idling control DS2. Therefore, the first assist control does not interfere with the execution of the stop idling control. Thus, the first assist control allows for the smooth execution of the stop idling control.

[0501] Even if the rotational speed G is lower than the first threshold H1, the control unit 25 does not start the first assist control DA1 if the first operation to keep the engine 22 rotating has not been performed. Therefore, the first assist control DA1 does not prevent the engine 22 from stopping. The first assist control DA1 allows the engine 22 to stop.

[0502] When the rotational speed G is lower than the first threshold H1 and the first operation is being performed, the control unit 25 starts the first assist control DA1. Therefore, the first assist control DA1 starts at an appropriate timing.

[0503] For example, the first operation includes turning the main switch 12 to the ON position. Therefore, obtaining the first operation is easy.

[0504] For example, the first operation includes turning the engine stop switch 14 to the OFF state. Therefore, it is easy to perform the first operation.

[0505] For example, the first operation includes at least one of the following: positioning the stand 62 in the storage position. Therefore, the first operation is easy to perform.

[0506] Even if the rotational speed G is lower than the first threshold H1, the control unit 25 will not start the first assist control DA1 if the specified equipment is not functioning correctly. Therefore, the first assist control DA1 will not start at an inappropriate timing.

[0507] When the rotational speed G is lower than the first threshold H1 and the predetermined equipment is functioning normally, the control unit 25 starts the first assist control DA1. Therefore, the first assist control DA1 starts at an appropriate timing.

[0508] For example, the specified device includes a motor generator 24A. Therefore, the specified device is operated by the first assist control DA1. Thus, it is easy to start the first assist control DA1 at the appropriate timing.

[0509] For example, the specified device includes at least one of the batteries 19. Therefore, the specified device is operated by the first assist control DA1. Thus, it is easy to start the first assist control DA1 at the appropriate timing.

[0510] When the engine 22 starts, the control unit 25 performs the second assist control DA2. In the second assist control DA2, the control unit 25 causes the motor generator 24A to rotate the engine 22. While the second assist control DA2 is being executed, the first assist control DA1 is not executed. After the second assist control DA2 is finished, the execution of the first assist control DA1 is permitted. Therefore, the first assist control DA1 does not interfere with the execution of the second assist control DA2. Thus, the first assist control DA1 allows the execution of the second assist control DA2.

[0511] When the first assist period FA1 is longer than the second reference time F2, the control unit 25 terminates the first assist control DA1. Therefore, the first assist period FA1 is limited to less than or equal to the second reference time F2. Thus, the first assist period FA1 is not excessively long.

[0512] The second reference time F2 is less than 1 second. Therefore, the first assist period FA1 is relatively short.

[0513] The second reference time F2 is shorter than the first reference time F1. Therefore, it is easy to increase the power balance.

[0514] When the control unit 25 performs engine stop control DS, the control unit 25 terminates the first assist control DA1. Therefore, the first assist control DA1 does not interfere with the execution of engine stop control DS. The first assist control DA1 allows the execution of engine stop control DS.

[0515] When the second operation to stop the engine 22 is performed, the control unit 25 terminates the first assist control DA1. Therefore, the first assist control DA1 does not prevent the engine 22 from stopping. The first assist control DA1 allows the engine 22 to stop.

[0516] When a designated device malfunctions, the control unit 25 terminates the first assist control DA1. Therefore, the first assist control DA1 does not interfere with stopping the engine 22. Thus, the first assist control DA1 terminates at an appropriate time.

[0517] 4. Modified Embodiments This invention is not limited to the above embodiments and can be modified and implemented as follows.

[0518] (1) The engine 22 may be classified as a single-cylinder engine. Alternatively, the engine 22 may be classified as a multi-cylinder engine.

[0519] (2) Engine 22 may be classified as a four-stroke engine. Engine 22 may be classified as a two-stroke engine.

[0520] (3) The engine 22 may be classified as an air-cooled engine. The engine 22 may be classified as a water-cooled engine.

[0521] (4) The engine unit 21 may be fixed to the vehicle body 3. The engine unit 21 may be immovable relative to the vehicle body. The engine unit 21 may be movable relative to the vehicle body 3.

[0522] (5) Motors 24 and 24A may be classified as AC motors. Motors 24 and 24A may be classified as DC motors.

[0523] (6) Motors 24 and 24A may also function as generators. Motors 24 and 24A do not have to function as generators.

[0524] (7) Motors 24 and 24A may be integrated with the generator. Motors 24 and 24A may be separate from the generator.

[0525] (8) The rotation axis of the motor 24 may be coaxial with the rotation axis of the engine 22. The rotation axis of the motor 24 does not have to be coaxial with the rotation axis of the engine 22.

[0526] (9) The rotation axis of the motor 24 may be coaxial with the axis 31a of the crankshaft 31. The rotation axis of the motor 24 does not have to be coaxial with the axis 31a.

[0527] (10) The first sensor 23 may directly detect the rotational speed G of the engine 22. The first sensor 23 may directly detect the rotational speed of the crankshaft 31. The first sensor 23 may indirectly detect the rotational speed G of the engine 22. The first sensor 23 may indirectly detect the rotational speed of the crankshaft 31.

[0528] (11) The first sensor 23 may include a pickup coil. The first sensor 23 may include a Hall IC. The first sensor 23 may include a Hall element.

[0529] (12) The configuration of the power control unit 27 may be changed as appropriate. For example, if the motor 24 is classified as a DC motor, the configuration of the power control unit 27 may be changed as appropriate. For example, if the motor 24 is classified as a DC motor, the power control unit 27 may be omitted.

[0530] (13) Start condition A may consist only of the first start condition A1. Alternatively, start condition A may include the first start condition A1 in addition to at least one of the second to sixth start conditions A2 to A6.

[0531] (14) Termination condition B2 may include at least one of the first to sixth termination conditions B1-B6. For example, termination condition B2 may consist of only one of the first to sixth termination conditions B1-B6.

[0532] (15) The first starting condition A1, "the rotational speed G is lower than the first threshold H1," may mean that at least one of the instantaneous values ​​g is lower than the first threshold H1. According to this modified embodiment, if the rotational speed G changes in one cycle, the first starting condition A1 is satisfied at a relatively early timing.

[0533] The first starting condition A1, "the rotational speed G is lower than the first threshold H1," may also mean that the average value GA of the rotational speed G is lower than the first threshold H1. According to this modified embodiment, if the rotational speed G changes in one cycle, the first starting condition A1 is satisfied at a relatively late timing.

[0534] Here, the average value GA is, for example, the average value of the rotational speed G in each cycle. The average value GA is, for example, the average value of the instantaneous values ​​g0, g1, ..., g23.

[0535] (16) The second starting condition A2, "the rotational speed G is higher than the second threshold H2," may mean that at least one of the instantaneous values ​​g is higher than the second threshold H2. The first starting condition A1, "the rotational speed G is higher than the second threshold H2," may mean that the average value GA is higher than the second threshold H2.

[0536] (17) The first termination condition B1, "the rotational speed G is higher than the third threshold H3," may mean that at least one of the instantaneous values ​​g is higher than the third threshold H3. According to this modified embodiment, if the rotational speed G changes in one cycle, the first termination condition B1 is satisfied at a relatively early timing.

[0537] The first termination condition B1, "the rotational speed G is higher than the third threshold H3," may also mean that the average value GA is higher than the third threshold H3. According to this modified embodiment, if the rotational speed G changes in one cycle, the first termination condition B1 is satisfied at a relatively late timing.

[0538] (18) With respect to the second termination condition B2, one first quantity K may be acquired in each cycle.

[0539] Alternatively, multiple first quantities K may be acquired in each cycle. For example, the first quantity K includes first quantities K1 and K2. The first quantity K1 is the increase from the first instantaneous value g0 to the second instantaneous value g6. The first quantity K2 is the increase from the instantaneous value g12 to the instantaneous value g18. According to this modified embodiment, even if combustion occurs in the crank angle range of 360 degrees to 540 degrees, the increase in rotational speed G due to that combustion is reflected in the first quantity K2. Therefore, even if combustion occurs in the crank angle range of 360 degrees to 540 degrees, it is easy to appropriately determine the second termination condition B2.

[0540] (19) The “predetermined equipment” in the sixth start condition A6 may include the power control unit 27. The “predetermined equipment” in the sixth end condition B6 may also include the power control unit 27. For example, the engine unit 21 is equipped with an eighth sensor (not shown). The eighth sensor detects the state of the power control unit 27. The state of the power control unit 27 includes, for example, at least one of the voltage of the power control unit 27, the current of the power control unit 27, and the temperature of the power control unit 27. The control unit 25 determines whether the power control unit 27 is normal or not based on the detection result of the eighth sensor. The control unit 25 determines whether the power control unit 27 is abnormal or not based on the detection result of the eighth sensor.

[0541] (20) The start of power generation control DG may be simultaneous with the end of the first assist control DA1. The start of power generation control DG does not have to be simultaneous with the end of the first assist control DA1. Power generation control DG may start after the end of the first assist control DA1. The start conditions for power generation control DG may be different from the end conditions B of the first assist control DA1.

[0542] (21) The termination of the power generation control DG may occur simultaneously with the start of the first assist control DA1. The termination of the power generation control DG does not have to occur simultaneously with the start of the first assist control DA1. The first assist control DA1 may start after the power generation control DG has finished. The termination conditions for the power generation control DG may differ from the start conditions A for the first assist control DA1.

[0543] (22) The throttle device 43 may be classified as, for example, an electronically controlled throttle. The throttle device 43 may be classified as, for example, a mechanical throttle.

[0544] (23) The number of front wheels 7 may be one. The number of front wheels 7 may be two. The number of rear wheels 18 may be one. The number of rear wheels 18 may be two.

[0545] (24) The saddle-type vehicle 1 may be classified into the sports type category. The saddle-type vehicle 1 may be classified into any of the following categories: street type, scooter type, and off-road vehicle (ALL-TERRAIN VEHICLE).

[0546] (25) The embodiments and each modified embodiment described in (1) to (24) above may be further modified as appropriate by substituting or combining each component with the components of other modified embodiments.

[0547] 1: Saddle-type vehicle 3: Body 7: Front wheel 9: Handlebars 10: Accelerator 11: Second sensor (accelerator sensor) 12: Main switch 13: Engine start switch 14: Engine stop switch 15: Seat 18: Rear wheel 19: Battery 21: Engine unit 22: Engine 23: First sensor (rotation speed sensor) 24: Motor 24A: Motor generator (motor, generator) 25: Control unit 27: Power control unit 28: Switching unit 31: Crankshaft 31a: Crankshaft axis 33: Piston 34: Combustion chamber 41: Ignition device 43: Throttle device 44: Throttle valve 45: Fuel injection device 51: Rotor 52: Rotor core 53: Magnet 55: Protrusion 56 : Stator 57 : Stator core 58 : Winding 61 : Kick start device 62 : Stand 63 : Third sensor (stand position sensor) 64 : Fourth sensor (saddle-type vehicle speed sensor) 65 : Fifth sensor (engine temperature sensor) 66 : Sixth sensor (motor status sensor) 67 : Seventh sensor (battery status sensor) A: Start conditions A1 : First start condition "Rotation speed G is lower than the first threshold H1" A2 : Second start condition "Rotation speed G is higher than the second threshold H2" A3 : Third start condition "The most recent power generation period FGM is equal to or greater than the first reference time F1" A4 : Fourth start condition "The control unit 25 does not perform engine stop control DS" A5 : Fifth start condition "The first operation has been performed" A6 : Sixth start condition "The specified equipment is functioning normally" B1 : First termination condition: "The rotational speed G is higher than the third threshold H3" B2: Second termination condition: "The first quantity K is greater than or equal to the standard quantity L" B3: Third termination condition: "The first assist period FA1 is longer than the second standard time F2" B4: Fourth termination condition: "The control unit 25 performs engine stop control DS" B5: Fifth termination condition: "The second operation is performed" B6: Sixth termination condition: "The specified equipment is abnormal" DA1, DA1a, DA1b: First assist control DA2: Second assist control (engine start control) DG, DGa, DGb: Power generation control EA: Assist mode EG: Power generation modeFA1, FA1a, FA1b: First assist period FG, FGa, FGb: Power generation period F1: First reference time F2: Second reference time G: Rotational speed GA: Average value of rotational speed g, g0-g23: Instantaneous value of rotational speed H1: First threshold H2: Second threshold H3: Third threshold J: Idle speed range JU: Upper limit of idle speed range JL: Lower limit of idle speed range K, K1, K2: First quantity L: Reference quantity

Claims

1. An engine unit comprising: an engine; a motor connected to the engine and configured to rotate the engine; a first sensor for detecting the rotational speed of the engine; and a control unit that performs first assist control based on the detection result of the first sensor, wherein in the first assist control, the control unit causes the motor to rotate the engine, and when the rotational speed is lower than a first threshold, the control unit starts the first assist control, and the first threshold is lower than the idle speed range of the engine.

2. An engine unit according to claim 1, wherein the idle speed range has a lower limit, and the first threshold is lower than the lower limit.

3. An engine unit according to claim 1 or 2, wherein when the rotational speed is lower than the first threshold and higher than the second threshold, the control unit starts the first assist control, and the second threshold is lower than the first threshold and higher than zero.

4. An engine unit according to claim 1 or 2, wherein when the rotational speed decreases from a value higher than the first threshold to a value lower than the first threshold, the control unit starts the first assist control.

5. An engine unit according to claim 1 or 2, comprising a generator configured to generate electricity by the rotation of the engine, wherein the period during which the generator generates electricity after the most recent first assist control has ended is defined as the most recent power generation period, and even if the rotational speed is lower than the first threshold, the control unit does not start the first assist control until the most recent power generation period is equal to or greater than the first reference time.

6. An engine unit according to claim 5, wherein the motor is configured to generate rotational power by power discharged from a battery, and the generator is configured to charge the battery.

7. The engine unit according to claim 5, wherein the motor also functions as the generator.

8. An engine unit according to claim 1 or 2, wherein the control unit terminates the first assist control based on the detection result of the first sensor.

9. An engine unit according to claim 8, wherein when the rotational speed is greater than or equal to a third threshold, the control unit terminates the first assist control, and the third threshold is higher than the first threshold.

10. An engine unit according to claim 9, wherein the idle speed range has an upper limit, and the third threshold is less than or equal to the upper limit.

11. An engine unit according to claim 1 or 2, wherein the control unit acquires a first quantity based on the detection result of the first sensor, the first quantity is the increase in rotational speed due to combustion of the engine, and the control unit terminates the first assist control based on the first quantity.

12. An engine unit according to claim 1 or 2, wherein the control unit terminates the first assist control when the first assist period during which the first assist control is performed is longer than the second reference time.

13. An engine unit according to claim 12, wherein the second reference time is 1 second or less.

14. A saddle-type vehicle comprising the engine unit described in claim 1 or 2, and a saddle-type vehicle.

15. A saddle-type vehicle according to claim 14, wherein the control unit starts the first assist control regardless of the speed of the saddle-type vehicle.

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