BR112019023949B1 - ENGINE UNIT AND METHOD FOR CONTROLLING AN ENGINE UNIT - Google Patents

Abstract

The present invention relates to an intake tube fuel injection four-stroke engine unit capable of improving the starting capability of an engine in which a high load region TH and a low load region TL are present. in four times. The engine unit includes: a four stroke engine body 10 having the high load region TH and the low load region TL in four strokes; a permanent magnet starter 30, including a permanent magnet and configured to rotate a crankshaft 46; and an ECU 32 configured to control the permanent magnet starter 30. The rotational speed of the permanent magnet starter 30 is controlled based on a four-stroke engine body temperature 10 measured by an engine temperature sensor. engine 28, such that an increase in the rotational speed of the crankshaft 46 is suppressed while the crank angle is in the low load region TL and from when a fuel injection device 54 injects fuel into an intake passage 33a until when an inlet valve 50 is closed.

Description

FIELD OF TECHNIQUE

[001] The present description relates to an engine unit that includes a high load region and a low load region in four strokes and begins by driving a crankshaft with a starter motor.

FUNDAMENTALS OF THE INVENTION

[002] A known engine of a vehicle is a four-stroke engine (e.g. a one-cylinder engine) that includes, in four strokes, a high load region where a load to rotate an engine crankshaft is high, and a low load region where the load to rotate the engine crankshaft is small.

[003] Patent Document 1 (Japanese Patent Application Publication No. 2003-343404) describes an engine starting apparatus that starts an engine by temporarily rotating a crankshaft in the reverse direction to stop the crankshaft and then rotate the crankshaft in a reverse direction. normal direction.

[004] In the engine starter of Patent Document 1, after the rotation of the engine crankshaft has stopped, an engine causes the crankshaft to rotate in the reverse direction to a position where the load increases in reverse rotation, i.e. , in the midst of a time of expansion. Then, the engine starter rotates the engine in the normal direction from the intermediate position in the expansion time to thereby rotate the crankshaft in the normal direction.

[005] As described above, the crankshaft is rotated in the reverse direction to the position at which the load increases, that is, the intermediate position in the expansion time, so that the crankshaft rotates in a region of low load, halfway through expansion time to a compression time at engine start. Subsequently, the motor reaches a first high load region. Thus, before the engine reaches the first high load region, the crankshaft rotation speed can be increased. Using both a large inertia force with the high rotational speed and torque output of a starter motor, the motor can pass through the first high load region.

[006] Patent Document 2 (International Patent Publication No. WO2015/093576) describes an engine unit in which while the crankshaft rotates in the normal direction after a combustion operation of a four-stroke engine body has stopped, a Resistance is applied to normal crankshaft rotation with a three-phase brushless motor.

[007] The engine unit stops the crankshaft in the one-stroke compression position in the four-stroke engine body. Then, according to an input from a start instruction to stop the crankshaft, the three-phase brushless motor rotates the crankshaft in the normal direction of the compression timing stop position.

[008] Therefore, in case of starting the body of a four-stroke engine, according to the input of the starting instruction, even with a small engine output torque, the crankshaft rotation can be started in a position in which the four stroke engine can be easily started.

[009] In the case where the crankshaft starts to rotate according to the input of the start instruction as described above, the crankshaft rotation speed gradually increases from the stopped state. In the case where normal crankshaft rotation starts from compression time, crankshaft rotation speed is low at compression time. As described above, in the case where the rotational speed of the crankshaft is low in the compression time, the crankshaft is not affected by a reaction force of compression by a gas in a combustion chamber. Consequently, the crankshaft can rotate rapidly under a load in the high-load region of the compression time. Citation List Patent Document Patent Document 1: Japanese Patent Application Publication No. 2003-343404. Patent Document 2: International Patent Publication No. WO2015/093576.

SUMMARY OF THE INVENTION Technical problem

[010] The inventors of the present description evaluated the starting capability of the motor in which the high load region and the low load region are present in four strokes, as described in Patent Documents 1 and 2. Consequently, the inventors of the present description found that on some specific phases, the load varies greatly, so that the starting ability of the motor degrades.

[011] It is, therefore, an objective of the present description to provide a configuration capable of improving the starting capability in the motor in which the high load region and the low load region are present in four strokes.

Solution to Problems

[012] The inventors of the present description evaluated the starting capacity of a previously presented motor in which a high load region and a low load region are present in four strokes.

[013] In the previously presented engine in which the high load region and the low load region are present in four strokes, the starting capacity of the engine is improved using an inertia force obtained by increasing the rotation speed of the crankshaft in the low load region. So the motor basically shows excellent starting ability.

[014] However, upon examination, the inventors of the present description have found that in some specific phases, a large variation of an engine load degrades the engine's starting ability inversely, when the crankshaft rotational speed is increased in the region low load.

[015] Specifically, in the engine where the high load region and the low load region are present in four strokes, even with an extremely low engine temperature, the crankshaft rotation speed increases in the low load region. In particular, with the extremely low engine temperature, the engine load increases even more and therefore controlling the increase of an inertia force by increasing the rotational speed of the crankshaft in the low load region is considered preferable.

[016] However, if the crankshaft rotation speed is increased in the low load region with an extremely low engine temperature, vaporization of the injected fuel is suppressed under a reduced vapor pressure of the fuel due to the decrease in temperature. This suppression of vaporization and increased crankshaft rotational speed reduces the time from the start of fuel injection to the completion of an intake stroke. Consequently, the amount of fuel flowing into a combustion chamber decreases.

[017] Consequently, the total amount of heat generation that contributes to combustion decreases so that a touch obtained by combustion cannot be sufficiently obtained, and the engine cannot be started in some cases. Furthermore, in the engine where the high load region and the low load region are present in four strokes, a large combustion interval can cause a similar phenomenon in the next combustion.

[018] As described above, in the engine where the high load region and the low load region are present in four strokes, when the crankshaft rotation speed increases in the low load region with an extremely low engine temperature, the Starting capacity can degrade on the other hand in some cases. The inventors of the present description found the above phenomenon by evaluating the starting capability of the motor in which the high load region and the low load region are present in the four strokes.

[019] As described in Patent Documents 1 and 2, in the motor where the high load region and the low load region are present in four strokes, the starting capability is improved using an inertia force obtained by increasing the crankshaft rotation speed in the low load region. As the engine load increases even more with an extremely low engine temperature, it is not conceivable to reduce the inertia force by suppressing an increase in the rotational speed of the crankshaft in the low load region.

[020] However, in the case of a permanent magnet starter, a torque can be increased as the rotational speed decreases. The inventors of the present description have found that in the motor in which the high load region and the low load region are present in four strokes, such a characteristic of a permanent magnet starter can be used to sufficiently increase the energy obtained by the first combustion, even when an increase in crankshaft rotation speed is suppressed in the low load region after crankshaft rotation from the stopped state and before the first combustion at extremely low engine temperature. In addition, in an engine temperature region where starting capability does not degrade, the increase in crankshaft rotation speed can be promoted in the low load region after crankshaft rotation from the stopped state and before the first combustion, and starting capability with the same level as before can be obtained.

[021] Based on the results of the examination described above, the inventors of the present description arrived at the configuration as follows.

[022] The present description employs the following configuration in order to solve the problem described above.

[023] (1) An engine unit according to an embodiment of the present description includes:

[024] A four-stroke engine body, including a combustion chamber having an intake port and an exhaust port, an intake valve configured to open and close the intake port, an exhaust valve configured to open and close the exhaust port, an intake passage connected to the intake port and configured to guide air in the atmosphere into the combustion chamber through the intake port, an exhaust passage connected to the exhaust port, a configured fuel injection device for injecting fuel into the intake passage, an ignition device configured to ignite an air-fuel mixture including fuel and air in the combustion chamber, a piston configured to move back and forth in the combustion chamber, and a crankshaft connected to the piston to rotate according to the back and forth motion of the piston, a high load region where a load to rotate the crankshaft is high and a low load region where the load to rotate the crankshaft is low being present in four strokes: a permanent magnet starter that includes a permanent magnet and is configured to rotate the crankshaft; a control device that controls the permanent magnet starter, the fuel injection device, and the ignition device; an engine temperature detector that senses a four-stroke engine body temperature; and a crank angle detector that senses a crank angle, the crank angle being a position of a crankshaft rotation angle, where the control device drives the permanent magnet starter to rotate the crankshaft from a crankshaft stopped state, controls the fuel injection device while a crankshaft crank angle is in the low load region, thus injecting fuel into the intake passage, controls the rotation speed of the permanent magnet starter so that an increase in the Crankshaft rotation speed is suppressed, based on the four-stroke engine body temperature detected by the engine temperature detector while the crankshaft crank angle is in the low load region and from when the fuel injection device injects fuel into the intake passage for when the intake valve is closed, and starts the four-stroke engine body igniting the air-fuel mixture in the combustion chamber using the igniter device while the crankshaft crank angle is in the high load region.

[025] With the configuration described above, the rotational speed of the permanent magnet starter is controlled according to the temperature of the motor unit, so that the rotational speed of the crankshaft can be reduced. Thus, the fuel injection time increases so that the fuel evaporation time according to the engine temperature can be obtained. In addition, as the permanent magnet starter has a large torque at low speed rotation, enough power to start the motor can be obtained. Therefore, this configuration described above can improve the starting ability of the motor.

[026] (2) In another aspect, the motor unit according to the present description preferably includes a configuration as follows: The control device controls the rotational speed of the permanent magnet starter, so that a speed of crankshaft rotation obtained when the body temperature of a four-stroke engine detected by the engine temperature detector is a first temperature is lower than the rotational speed of the crankshaft obtained when the body temperature of a four-stroke engine detected by the temperature detector engine temperature is a second temperature higher than the first temperature.

[027] With this configuration, at a low engine temperature, the time for fuel evaporation can be obtained so that the engine starting capability can be improved.

[028] (3) In yet another aspect, the engine unit according to the present description preferably includes a configuration as follows: The fuel injection device injects fuel towards the inlet valve. Injecting fuel to a position close to the intake port can increase fuel efficiency.

[029] (4) In yet another aspect, the engine unit according to the present description preferably includes a configuration as follows: The control device determines a rotational speed of the crankshaft according to a given fuel injection time based on the four-stroke engine body temperature detected by the engine temperature detector.

[030] With this configuration, the control of the fuel injection time according to the engine temperature can be easily performed. Thus, motor starting can be more efficiently controlled.

[031] (5) In yet another aspect, the engine unit according to the present description preferably includes a configuration as follows: The engine temperature detector is a sensor that senses the temperature of a coolant in the engine body. four-stroke engine or the oil temperature in an oil passage. With this configuration, the sensor needed as a function of the motor is shared so that the configuration of the motor unit can be simplified.

[032] (6) In yet another aspect, the engine unit according to the present description preferably includes a configuration as follows: The control device causes the fuel injection device to inject fuel until the injection time of fuel exceeds a predetermined time in which the fuel required to start the engine is allowed to be supplied. With this configuration, a predetermined amount or more of fuel delivery to the engine can be obtained so that the starting capability of the engine can be improved.

[033] (7) In yet another aspect, the motor unit according to the present description preferably includes a configuration as follows: The control device controls the rotational speed of the motor so that as the body temperature of four-stroke engine detected by the engine temperature detector decreases, the crankshaft rotation speed in the fuel injection timing decreases. With this configuration, the time for fuel evaporation at low temperatures can be obtained so that the engine starting capability can also be improved at low temperatures.

[034] (8) In yet another aspect, the engine unit according to the present description preferably includes a configuration as follows: The four-stroke engine body further includes a decompression mechanism that temporarily opens the exhaust valve of so as to eject the air-fuel mixture into the combustion chamber while the crankshaft crank angle is in the high load region. In the configuration, including the decompression mechanism as described above, the crankshaft rotation speed may be insufficiently increased by the first combustion at engine start. On the other hand, the application of the settings described above allows the energy to start the engine to be obtained by the first combustion, and therefore the engine's starting capability can be improved.

[035] The terminology used in this document is used for the purpose of defining certain modalities only and is not intended to limit the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

[036] It will be further understood that the terms "including", "comprising" or "having" and their variations, when used in this specification, specify the presence of features, steps, elements, components and/or their equivalents, but may include steps , operations, elements, components and/or one or more of the groups.

[037] It will be further understood that the terms "mounted", "connected", "coupled" and/or their equivalents are widely used and cover both mounting, connection and direct coupling and indirect mounting, connection and coupling. Furthermore, “attached” and “attached” are not restricted to physical or mechanical connections or couplings, and may include direct or indirect connections or couplings.

[038] Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as is commonly understood by one skilled in the art to which the present description pertains.

[039] It will further be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant technique and in the present description and will not be interpreted in an idealized or excessively manner. formal, unless expressly defined here.

[040] In describing the present description, it is understood that various techniques and steps are described. Each of these has individual benefits and can also be used in conjunction with one or more, or in some cases, all of the other techniques described.

[041] Therefore, for the sake of clarity, this description will refrain from repeating all possible combinations of individual steps unnecessarily. Even so, the specification and claims should be read with the understanding that such combinations are entirely within the scope of the present description.

[042] In the following description, several specific examples are presented in order to provide a complete understanding of the present description. It will be apparent, however, to one skilled in the art that the present description can be practiced without these specific examples.

[043] Therefore, the following description is to be considered as an exemplification of the present description, and is not intended to limit the present description to the specific embodiments illustrated by the figures or description below.

1. Departure Definition >

[044] Starting here refers to the rotation of a crankshaft applying an external force from outside an engine without using combustion in the cylinders of an engine. In particular, starting refers to the rotation of the crankshaft using an engine to start the engine. The term “starting” includes the application of an external force to the crankshaft while combustion takes place in the engine cylinders.

2. Definition of High Load Region >

[045] The high engine load region in this document refers to a region where a torque required to compress a gas in the cylinder is high at a compression time over an engine operating range. The engine's high load region includes the compression time.

3. Definition of Low Load Region >

[046] The low load region of the engine in this document refers to a region where the gas in the cylinder is not compressed within the operating range of the engine.

4. Four Stroke Engine Temperature Setting >

[047] Four-stroke engine body temperature refers to a temperature in an engine's combustion chamber or a temperature detected by an engine temperature detector to detect a temperature relative to a temperature in the combustion chamber. The temperature relative to the temperature in the combustion chamber refers to a temperature that varies depending on the temperature in the combustion chamber, such as a temperature of a coolant, temperatures of a cylinder, and a crankcase body of a four-stroke engine body. , a fuel temperature, an injector temperature, and an inlet port temperature. This temperature could be an oil temperature in an oil passage in the case of an air-cooled engine, for example.

ADVANTAGEOUS EFFECTS OF THE INVENTION

[048] A motor unit according to an embodiment of the present description can improve the starting capability of a motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[049] Figure 1 is a schematic view illustrating a configuration of an engine unit according to the first embodiment.

[050] Figure 2 is an illustration showing a relationship between a crank angle and a torque required to start a motor.

[051] Figure 3 is a flowchart depicting a rotational speed control operation of a permanent magnet starter by an ECU at the start of the motor unit illustrated in Figure 1.

[052] Figure 4 is a graph showing a relationship between motor speed and crank angle at start-up of the motor unit illustrated in Figure 1.

[053] Figure 5 is a view that illustrates an example of movement of a crankshaft in a starter of the motor unit illustrated in Figure 1.

[054] Figure 6 is a graph schematically showing a relationship between a degree of opening of an exhaust valve and a crank angle in the motor unit illustrated in Figure 1.

[055] Figure 7 is a graph showing the motor speeds at a high motor temperature and a low motor temperature at start-up of the motor unit illustrated in Figure 1.

[056] Figure 8A is a graph showing an example of a relationship between an engine temperature and a crankshaft rotation speed at engine start.

[057] Figure 8B is a graph showing another example of the relationship between engine temperature and crankshaft rotation speed at engine start.

[058] Figure 9 illustrates a schematic configuration of the engine unit, while showing an example of a relationship between engine temperature and crankshaft rotation speed at engine start and a relationship between a crank angle and a required torque at engine start.

[059] Figure 10 is a schematic view illustrating a configuration of an engine unit according to the second embodiment.

[060] Figure 11 is a graph that shows an example of a comparison with the cases of a different fuel injection position in the relationship between engine temperature and crankshaft rotation speed at engine start.

DETAILED DESCRIPTION First Mode

[061] The modalities will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals, and their description will not be repeated. Dimensions of components in drawings do not strictly represent actual dimensions of components and dimensional proportions of components.

5. Motor Unit Setup >

[062] A configuration of a 100 motor unit will be described. Engine unit 100 is provided on a motorcycle, which is an example of a vehicle. Figure 1 is a view schematically illustrating a configuration of engine unit 100. The following description will be directed to a case where engine unit 100 includes a single cylinder four-stroke engine body 10 (hereinafter referred to simply as of an engine 10). In Figure 1, the components of the motor unit 100 are simplified. The engine unit 100 according to this embodiment is an engine unit, including a four-stroke engine 10 in which an intake time, a compression time, an expansion time and an exhaust time are included in a cycle.

[063] As illustrated in Figure 1, the engine unit 100 includes the engine 10, an air filter 12, an intake pipe 14a, an intake pipe 14b, an exhaust pipe 16, an accelerator device 20, a sensor (hereinafter called TPS) 22, a pressure sensor 24, a crank angle sensor 26 (crank angle sensor), an engine temperature sensor 28 (engine temperature sensor), a permanent magnet starter 30, an engine control device (control unit, hereafter called an ECU) 32, an inverter 62, a battery 64, and a starter 66. First, the components except the engine 10, will be briefly described.

[064] Air filter 12 takes air from the atmosphere (external vehicle air, including engine 10) and purifies the intake air. One end of the inlet tube 14a is connected to the air cleaner 12. The other end of the inlet tube 14a is connected to a throttle body 20c described later of the throttle device 20. One end of the inlet tube 14b is connected to the throttle body 20c. of the throttle 20c of the throttle device 20. The other end of the inlet pipe 14b is connected to a passage 34a formed in a cylinder head 34 described later. One end of the exhaust tube 16 is connected to the passage 34b formed in the cylinder head 34 described later. In that embodiment, an inlet passage 33a is formed, for example, by a space within the inlet tube 14a, a space within the throttle body 20c, a space within the inlet tube 14b, and the passage 34a. In this embodiment, an exhaust passage 33b is formed, for example, by passage 34b and a space within exhaust pipe 16.

[065] Inlet passage 33a guides air in the atmosphere purified by air filter 12 to a combustion chamber 36, described later, of engine 10 through an inlet port 35a described later. On the other hand, the exhaust passage 33b expels the air in the combustion chamber 36 to the atmosphere (outside the vehicle) through an exhaust port 35b described later.

[066] The configuration of the inlet passage 33a is not limited to the configuration illustrated in Figure 1, and only needs to guide the air in the atmosphere to the combustion chamber 36 described later. The configuration of the exhaust passage 33b is not limited to the configuration illustrated in Figure 1, and only needs to discharge a gas in the combustion chamber 36 to the atmosphere. In the following description, the terms "upstream" and "downstream" refer to "upstream" and "downstream" in relation to an airflow direction 20 from air filter 12 to exhaust passage 33b through the inlet port 33a and the engine 10.

[067] Throttle device 20 includes a butterfly valve 20a, an actuator device 20b for actuating the butterfly valve 20a and the throttle body 20c. The butterfly valve 20a and the actuation device 20b are arranged on the throttle body 20c. As the drive device 20b, an electric motor can be used, for example.

[068] The butterfly valve 20a is actuated by the actuation device 20b to thus adjust an opening area of the inlet passage 33a. That is, in this embodiment, the butterfly valve 20a serves as a regulating valve that adjusts the opening area of the inlet passage 33a. As will be described later, the drive device 20b is controlled by an ECU 32.

[069] The TPS 22 detects a position of the throttle valve 20a as a throttle opening angle. The TPS 22 issues a signal indicating the detected throttle opening angle to the ECU 32.

[070] Pressure sensor 24 senses a pressure (inlet pressure) from a space downstream of butterfly valve 20a in inlet passage 33a. That is, the pressure sensor 24 senses a pressure from a space between the butterfly valve 20a and the combustion chamber 36 described later in the inlet passage 33a. In the following description, inlet pressure refers to a pressure of a space between butterfly valve 20a and combustion chamber 36 in inlet passage 33a. The pressure sensor 24 emits a signal referring to the pressure detected in the ECU 32. In this embodiment, the pressure sensor 24 is a pressure detector.

[071] Crank angle sensor 26 detects a position of rotation (hereinafter called a crank angle) of a crankshaft 46 described further from engine 10. Crank angle sensor 26 outputs a signal indicating the crank angle detected (crank pulse signal) to ECU 32.

[072] Based on the signal emitted from the crank angle sensor 26, the ECU 32 ignites an air mixture in the combustion chamber 36 by an ignition plug 56 described further from the engine 10.

[073] The configuration and operation of ECU 32 described above is similar to a conventional ECU and will not be described in detail.

[074] ECU 32 performs the operation control at engine start. Specifically, the ECU 32 includes a rotational speed calculator 70, a crank angle determiner 71, a fuel injection determiner 72, an engine controller 73, a fuel injection controller 74, an ignition controller 75, and a memory 76.

[075] The rotational speed calculator 70 calculates a rotational speed of the engine 10, i.e. a rotational speed of the crankshaft 46, based on the crank pulse signal emitted from the crank angle sensor 26. A crankshaft rotational speed 46 calculated by rotational speed calculator 70 is input to motor controller 73 and is used for feedback control of permanent magnet starter 30.

[076] The crank angle determiner 71 determines whether the crank angle obtained based on the crank pulse signal emitted from the crank angle sensor 26 is greater than a predetermined angle or not, and determines whether the crank angle crank is greater than a specified angle at which fuel injection starts or does not start. The result of the determination by the crank angle determiner 71 is input to the motor controller 73 and used to control the drive of the permanent magnet starter 30. The result of the determination by the crank angle determiner 71 is entered into the injection controller 74 and used for driving control of a fuel injection device 54, described later, of the engine 10. The predetermined angle is an angle smaller than the specified angle.

[077] Based on the engine temperature information emitted from the engine temperature sensor 28, the fuel injection timer 72 obtains a fuel injection time according to an engine temperature from data from injection time previously stored in memory 76. On injection of fuel from the fuel injection device 54, the fuel injection timer 72 calculates a cumulative fuel injection time (cumulative fuel injection time), and determines whether the calculated cumulative fuel injection time is greater than a default value (default time) or not.

[078] The engine temperature sensor 28 is, for example, a sensor for measuring a temperature of an engine coolant 10. The engine temperature sensor 28 can directly measure a temperature in the combustion chamber 36 or it can measure a temperature in a cylinder 40 or a crankcase 44, for example, of the engine 10. That is, the temperature sensor of the engine 28 can be arranged in any position, provided that the temperature sensor of the engine 28 can measure a temperature relative to the chamber combustion engine 36 of engine 10.

[079] The motor controller 73 controls the drive of the permanent magnet starter 30 at motor start, based on the rotational speed of the crankshaft 46 emitted from the rotational speed calculator 70 and the result of the determination emitted to from the crank angle determiner 71. Specifically, the motor controller 73 performs the rotational speed control of the permanent magnet starter 30, according to the determination result emitted from the crank angle determiner 71, and performs feedback control of permanent magnet starter motor 30 using crankshaft rotation speed 46.

[080] If the crank angle determiner 71 determines that the crank angle is greater than the specified angle at which fuel injection begins, the fuel injection controller 74 causes the fuel injection device 54 to inject fuel. On the other hand, if the fuel injection timer 72 determines that the cumulative fuel injection time is longer than the default value, the fuel injection controller 74 stops fuel injection by the fuel injection device 54 .

[081] The ignition controller 75 ignites the ignition plug 56 at the moment when the crank angle obtained based on the pulse signal emitted from the crank angle sensor 26 reaches an ignition timing of the ignition plug 56.

[082] Permanent magnet starter 30 is a motor that drives crankshaft 46 to start motor 10. In this embodiment, permanent magnet starter 30 is a DC brushless motor. The permanent magnet starter 30 has a characteristic that the torque increases as the rotation speed decreases.

[083] Like the brushless DC motor, a brushless DC motor of a type that senses an electrical angle using a Hall sensor or a brushless DC motor of a type that senses a mechanical angle using a hand crank can be used.

[084] An output shaft of the permanent magnet starter 30 is connected to the crankshaft 46 of the motor 10 to rotate the crankshaft 46. In this embodiment, the output shaft of the permanent magnet starter 30 is connected to the crankshaft 46 through of the power transmission motor (for example, a belt, a chain, a gear, a speed reducer or an acceleration gear). It should be noted that the permanent magnet starter 30 only needs to be connected to the crankshaft 46 of the motor 10 so that the crankshaft 46 can rotate in the normal direction. Thus, the permanent magnet starter 30 can be connected to the crankshaft 46 via the power transmission motor. The axis of rotation of the permanent magnet starter 30 may substantially coincide with an axis of rotation of the crankshaft 46.

[085] Inverter 62 controls a current to be supplied from battery 64 to permanent magnet starter 30 to thereby control the rotational speed of permanent magnet starter 30. Inverter 62 is controlled by motor controller 73 of ECU 32.

[086] Battery 64 supplies electrical power to permanent magnet starter 30 through inverter 62.

[087] On starting engine 10, starter switch 66 gives an ON signal in accordance with a driver's operation or in the event that engine starting conditions are satisfied in an idle stop system described later. When the ON signal is output from starter 66, ECU 32 starts controlling the rotational speed of permanent magnet starter 30 in order to start engine 10.

[088] Motor 10 configuration will now be described. Like engine configuration 10, several known engine configurations may be employed and thus engine components will not be described in detail.

[089] Engine 10 includes cylinder head 34, cylinder 40, piston 42, crankcase 44, crankshaft 46, connecting rod 48, inlet valve 50, exhaust valve 52, fuel injection 54, and ignition plug 56 (ignition device).

[090] Piston 42 is movable back and forth in cylinder 40. Crankshaft 46 is rotatable in crankcase 44. Piston 42 and crankshaft 46 are coupled to each other via connecting rod 48. rearward movement of piston 42 is transferred to crankshaft 46 via connecting rod 48. Accordingly, crankshaft 46 rotates.

[091] In the engine 10, the combustion chamber 36 is formed by the cylinder head 34, the cylinder 40 and the piston 42. The combustion chamber 36 includes the inlet port 35a and the exhaust port 35b. Cylinder head 34 includes port 34a to be connected to inlet port 35a and port 34b to be connected to exhaust port 35b. In this embodiment, passage 34a connects inlet pipe 14b and combustion chamber 36a to each other. Passage 34b connects combustion chamber 36 and exhaust pipe 16 to each other.

[092] Inlet valve 50 opens and closes inlet port 35a. Exhaust valve 52 opens and closes exhaust port 35b. The inlet valve 50 is actuated by a valve mechanism not illustrated. Likewise, the exhaust valve 52 is actuated by a valve mechanism not illustrated.

[093] In one cycle, the inlet valve 50 is opened before the exhaust valve 52 is closed, and the inlet valve 50 is closed before the exhaust valve 52 is opened. In other words, at least in the low load operating range, the intake time starts before the exhaust time has expired.

[094] Specifically, the inlet valve 50 is opened at a crank angle of, for example, 344 degrees to 576 degrees. The crank angle while the inlet valve 50 is open is not limited to the range described above, and the inlet valve 50 can be opened with a crank angle of 360 degrees to 540 degrees minimum and 326 degrees to 610 degrees maximum. .

[095] Exhaust valve 52 is open at least on exhaust time. Specifically, the exhaust valve 52 is opened at a crank angle of, for example, 64 degrees to 378 degrees. The crank angle while the exhaust valve 52 is open is not limited to the range described above, and the exhaust valve 52 can be opened with a crank angle of 180 degrees to 360 degrees minimum and 70 degrees to 390 degrees maximum. .

[096] The fuel injection device 54 injects fuel into the inlet passage 33a. In this embodiment, the fuel injection device 54 injects fuel towards the inlet valve 50. The fuel supplied in the inlet passage 33a is sent to the combustion chamber 36 as an air-fuel-air mixture. Ignition plug 56 ignites the air-fuel mixture in combustion chamber 36.

[097] Fuel injection device 54 and ignition plug 56 perform fuel injection and ignition by ECU control 32 at appropriate times according to times in an engine cycle 10.

[098] A decompression mechanism 58 is provided near a camshaft not illustrated to actuate the exhaust valve 52. The decompression mechanism 58 reduces an increase in resistance to rotation of the crankshaft 46 caused by the compression of air in the cylinder over time. engine compression. That is, the decompression mechanism 58 is a mechanism that opens the exhaust valve 52 at a predetermined time in order to reduce the pressure in the cylinder at the compression time at engine start.

6. Motor Unit Start Operation >

[099] First, a torque required to start the motor will be described. Figure 2 is an illustration showing a relationship between a crank angle and a torque required to start the engine.

[0100] The engine 10 of the engine unit 100 includes, in four strokes, a high load region TH where a load to rotate the crankshaft 46 is high and a low load region TL where the load to rotate the crankshaft 46 is less than the load in the high load region TH. At the crank angle of crankshaft 46, the low load region TL is equal to or greater than the high load region TH. More specifically, the TL low-charge region is larger than the TH-high-charge region. In other words, a rotation angle region corresponding to the low load region TL is larger than a rotation angle region corresponding to the high load region TH.

[0101] More specifically, engine 10 repeats four strokes between intake time, compression time, expansion time and exhaust time. As illustrated in Figure 2, compression time is included in the high-load region TH, but not included in the low-load region TL. In engine 10 according to this embodiment, the high-load region TH is a region substantially overlapping the compression time, and the low-load region TL is a region substantially overlapping the intake time, expansion time, and exhaust time. exhaustion. It should be noted that the edge of each high-load region TH and the low-load region TL need not coincide with the edge of each of the times.

[0102] In the compression stroke, an air-fuel mixture in the combustion chamber 36 is compressed by the piston 42, so that a reaction force is generated by the compression. Therefore, at compression time, a torque required to start is greater than at other times. The decompression mechanism 58 is activated at the compression time to thereby reduce the pressure in the combustion chamber 36.

[0103] Decompression mechanism 58 operates to open exhaust valve 52 with a crank angle of about 630 degrees. A period that the exhaust valve 52 is opened by the decompression mechanism 58 is a short period in the compression time. Furthermore, as illustrated in Figure 6, the time when the exhaust valve 52 is opened by the pressure relief mechanism 58 is immediately before the inlet valve 50 is closed or after the inlet valve 50 is closed. As illustrated in Figure 6, the moment at which the exhaust valve 52 is opened by the decompression mechanism 58 is adjustable within the compression time. The amount of valve lift of the exhaust valve 52 in a period of actuation of the decompression mechanism 58 is less than the amount of lift of the valve of the inlet valve 50. The amount of lift of the valve is a distance at which the valve moves away from the valve seat in an axial direction.

[0104] A start operation of the motor unit 100 will now be described. In this embodiment, when starting the engine 10, the start is performed by the starter 30. The starter 10 includes a case where the engine 10 starts from a state in which the engine temperature is lower than the temperature of the engine. operating temperature of engine 10 and a case where engine 10 restarts from an engine stop state in an idle stop system. The idle stop system has a configuration similar to a known configuration and therefore the detailed description and illustration of the idle stop system will be omitted.

[0105] Figure 3 is a flowchart depicting a rotational speed control operation of the permanent magnet starter 30 by the ECU 32 at the start of the motor unit 100. Figure 4 is a graph showing a relationship between the engine speed and crank angle when starting the engine unit 100. Figure 5 is a view illustrating an example of a movement of the crankshaft 46 at starting the engine unit 100.

[0106] First, when starter 66 is turned on and a start request flag is set (step S1), motor controller 73 of ECU 32 drives and rotates permanent magnet starter 30.

[0107] Engine 10 stops combustion by a stop combustion instruction by ECU 32. Crankshaft 46 rotates with an inertia force after stopping combustion in engine 10. When the inertia force becomes less than an inertia force compression reaction at the compression time of engine 10, crankshaft 46 rotates in the reverse direction by the compression reaction force and stops. Thus, as illustrated in Figure 5, the crankshaft 46 stop position is generally at a crank angle P0 of the intake stroke which is one time before the compression stroke.

[0108] Based on a signal emitted from the crank angle sensor 26, the ECU 32 acquires information about the crank angle and the rotational speed of the engine 10. In the case where the crank angle of the crankshaft 46 is not is in a specified position, the motor controller 73 of the ECU 32 rotates the permanent magnet starter 30 in the reverse direction, as indicated by dashed lines in Figures 4 and 5. The reverse rotation of the permanent magnet starter 30 continues until the crank angle reaches the specified position P1 in the expansion time.

[0109] Subsequently, the crank angle determiner 71 of the ECU 32 determines whether the crank angle of the crankshaft 46 is greater than a predetermined angle or not (step S2). The default angle is an angle smaller than a crank angle (specified angle) at which fuel injection takes place.

[0110] If crank angle of crankshaft 46 is greater than predetermined angle (YES in step S2), engine controller 73 of ECU 32 controls the drive of permanent magnet starter 30, so that speed rotation speed of crankshaft 46 is a target rotation speed A (step S3). The rotational speed control of the permanent magnet starter 30 can be torque control using an operating rate, or speed control where feedback control is performed by detecting the rotational speed of the magnet starter. permanent 30.

[0111] The upper limit of target rotational speed A is the speed at which a fuel injection time obtained from the engine temperature measured by the engine temperature sensor 28 as described below can be obtained, and the lower limit of the target rotational speed A is a speed at which the motor can undergo a maximum load in the high load region TH.

[0112] If the rotational speed of the crankshaft 46 is low, the vaporized fuel cannot be compressed in the high load region TH, and the engine 10 is stopped.

[0113] On the other hand, if the rotation speed of the crankshaft 46 is high, the time for evaporation of the injected fuel cannot be sufficiently obtained. In that case, a concentration of fuel in the combustion chamber 36 of the engine 10 becomes insufficient, which can cause a failure to increase the rotational speed of the engine 10 and an accidental fire, for example.

[0114] That is, when the rotational speed of crankshaft 46 at start-up increases excessively, after an FI fuel injection time lapse (see Figure 4), fuel is insufficiently evaporated in passage 34a of intake passage 33a. Consequently, an air-fuel ratio in the combustion chamber 36 is not an appropriate value in some cases.

[0115] The target rotation speed A of the crankshaft 46 is determined within the range between the upper and lower limits considering the phenomenon described above. The target rotation speed A is obtained based on the temperature of the motor 10, which will be described later.

[0116] If the crank angle of crankshaft 46 is less than or equal to the predetermined angle value (NOT in step S2), the crank angle determiner 71 repeats the determination of step S2 until the crank angle of crankshaft 46 exceeds the predetermined angle.

[0117] After the permanent magnet starter 30 is driven and controlled at target rotational speed A, the crank angle determiner 71 determines whether the crank angle of crankshaft 46 is greater than a specified angle at which fuel injection starts (step S4). If the crank angle of crankshaft 46 is greater than the specified angle for the start of fuel injection (YES in step S4), the fuel injection controller 74 of the ECU 32 causes the fuel injection device 54 to inject fuel (step S5). On the other hand, if the crank angle of crankshaft 46 is less than or equal to the angle specified for the start of fuel injection (NOT in step S4), the determination of step S4 is repeated until the crank angle of crankshaft 46 exceeds the specified angle to start fuel injection.

[0118] In this mode, the specified angle for fuel injection starts at the fuel injection device 54 is, for example, 300°. Alternatively, the angle specified for the start of fuel injection can be an angle other than 300°. As described above, the fuel injection timing is determined by the fuel injection timing 72 based on predetermined injection timing data based on engine temperature. Injection timing data is stored in memory 76 of ECU 32. Fuel injection must be completed within a period from the start of fuel injection until when the inlet valve 50 is closed (within a period FI shown in Figure 4) at the latest.

[0119] After the start of fuel injection by the fuel injection device 54, the fuel injection timing 72 of the ECU 32 determines whether the cumulative fuel injection time as a cumulative fuel injection time is longer than than a default value (default time) of the fuel injection time or not (step S6). If the cumulative fuel injection time is determined to be longer than the default value (YES in step S6), fuel injection by the fuel injection device 54 is stopped (step S7). Afterwards, the rotational speed control at which the target rotational speed was set to A in step S3 is canceled (step S8), and a flow of rotational speed control at motor start is completed (end). The default value is determined depending on engine temperature using injection timing data.

[0120] On the other hand, if the cumulative fuel injection time is determined to be less than or equal to the default value (NO in step S6), fuel injection by the fuel injection device 54 continues until the injection time of cumulative fuel exceeds the default value.

[0121] After controlling the rotational speed of the permanent magnet starter 30 by the ECU 32 described above, when the inlet valve 50 is closed, in the following compression time, the compressed pressure in the combustion chamber 36 serves as a rotational load of crankshaft 46. Thus, as shown in Figure 4, the rotational speed of crankshaft 46 decreases. After crankshaft 46 has passed through a position corresponding to a compression top dead center in compression timing, ignition controller 75 of ECU 32 causes ignition plug 56 to ignite an air-fuel mixture in the combustion chamber. 36, so that initial combustion occurs. In this embodiment, the ignition crank angle of ignition plug 56 is 715 degrees, but is not limited to this example.

[0122] With the initial combustion, a rotational force is exerted on the crankshaft 46, and the times in the four cycles are run intermittently in the engine 10, so that the starting of the engine 10 by starting is completed.

< Target Rotation Speed Determination Procedure >

[0123] Next, a procedure for determining the target rotational speed A of crankshaft 46 at engine start 10 will be described.

[0124] Based on the engine temperature 10 measured by the engine temperature sensor 28, the fuel injection timing 72 of the ECU 32 refers to the injection timing data previously stored in the memory 76 of the ECU 32, and determines a fuel injection time for the first combustion at engine start 10.

[0125] Injection time data is, for example, a table in which the engine temperature is associated with the fuel injection time. Injection timing data is set so that fuel injection timing increases as engine temperature decreases. The injection time can be calculated so that the injection time increases with decreasing temperature according to a predetermined relational expression, or it can be defined so that the injection time is constant within a predetermined range and decreases as the temperature increases. engine temperature rises through the predetermined range. An example of injection time is indicated by solid arrow in Figure 2. As shown in Figure 2, injection time at -5°C engine temperature is longer than injection time at 80°C engine temperature. Figure 2 only shows a first time for the injection time and does not show subsequent times.

[0126] Injection timing data varies depending on the position at which the fuel injection device 54 injects fuel, the direction of injection, and the size of the liquid droplets of the injected fuel. This is carried out in order to obtain an adequate air-fuel ratio at ignition by sufficiently evaporating the injected fuel, even at low engine temperatures 10. Thus, the injection time data is defined so that the fuel injection time is long. at a low engine temperature. In general, the injection time decreases as the liquid droplet size of the injected fuel decreases and the spray expansion angle increases.

[0127] Fuel injection by fuel injection device 54 starts at a predetermined crank angle (e.g. 300 degrees), and ends until intake valve 50 is closed at engine intake timing 10. Thus, the rotational speed of the crankshaft 46 needs to be determined such that the fuel injection ends before the inlet valve 50 is opened. In this mode, the timing of the start of fuel injection is fixed at a crank angle of 300 degrees, regardless of the engine temperature.

[0128] Consequently, in order to obtain fuel injection timing at low temperatures, the target rotational speed A of crankshaft 46 needs to be adjusted depending on the time from fuel injection until intake valve 50 closes. shown in Figure 7, as the injection time increases, the target rotation speed A is set lower. As described above, the fuel injection timing needs to be increased as the engine temperature drops. Thus, as shown in Figure 7, a target rotational speed A' at a low engine temperature is less than the target rotational speed A at a high engine temperature.

[0129] Figure 8A shows an example of a relationship between engine temperature and a rotational speed of crankshaft 46 at engine start. As described above, the target rotational speed A of the crankshaft 46 decreases as the temperature of the engine 10 decreases. As an example, as shown in Figure 8A, at motor temperatures 10 at any two points on the graph (called a first temperature and a second temperature, respectively), the ECU 32 controls the rotational speed of the permanent magnet starter. 30, so that the rotational speed of the crankshaft 46 at the relatively low first temperature is less than the rotational speed at the second temperature greater than the first temperature.

[0130] The rotational speed of crankshaft 46 does not change continuously according to the temperature of engine 10 as described above, but as shown in Figure 8B, control can be performed so that the temperature of engine 10 is constant up to a temperature predetermined and when the temperature of the motor 10 drops below the predetermined temperature, the rotation speed is reduced.

[0131] As described above, fuel injection only needs to be completed within a period from when fuel injection starts to when the inlet valve 50 is closed (FI fuel injection time). Thus, the fuel injection time of the injection timing data may be shorter than the FI fuel injection time.

[0132] When the target rotation speed of the crankshaft 46 is increased according to the fuel injection timing, the power consumption of the permanent magnet starter 30 increases and consequently the power consumption of the battery 64 increases. On the other hand, the target rotational speed A of the crankshaft 46 can be reduced to a rotational speed whose required fuel injection time can be obtained according to the engine temperature. This can reduce the power consumption of the permanent magnet starter 30 so that an increase in the power consumption of the battery 64 can be suppressed.

[0133] In the motor unit 100 according to this embodiment, the permanent magnet starter 30 which can achieve higher output torque at lower rotational speed is used as the starter. Furthermore, in the engine 10 in which the high load region TH and the low load region TL are present in four strokes, as shown in Figure 5, in the low load region TL after the crankshaft 46 rotates from the stopped state to the first combustion, the target rotation speed A of the crankshaft 46 is adjusted according to the engine temperature. Thus, a time for vaporization of fuel supplied in the inlet passage 33a can be obtained. As a result, the energy obtained by the first combustion can be sufficiently increased so that the starting capability of the engine 10 can be improved.

[0134] In this embodiment, the decompression mechanism 58 is activated at the compression time at engine start, so that the pressure in the combustion chamber 36 can be reduced. However, the actuation of the decompression mechanism 58 at the compression time may cause the possibility that sufficient power cannot be obtained in the first compression at engine start so that the rotational speed of the crankshaft 46 cannot be increased. On the other hand, in the motor unit 100 according to this embodiment, in the low load region TL after rotation of the crankshaft 46 from the stopped state to the first combustion, the target rotational speed A of the crankshaft 46 is adjusted according to the engine temperature so that the vaporization time of the fuel supplied in the inlet port 33a can be obtained. Thus, the energy obtained by the first combustion can be sufficiently improved and, as a result, the starting ability of the engine 10 can be improved.

Second Mode

[0135] Figure 10 is a schematic view illustrating a configuration of a motor unit 101 according to the second embodiment. The engine unit 101 according to this embodiment is different from the engine unit 100 according to the first embodiment, wherein an ECU 80 sets a rotational speed of the crankshaft 46 according to the temperature of the engine 10 using speed data from rotation as engine temperature map data and a target rotation speed A.

[0136] Specifically, the ECU 80 includes a rotational speed calculator 70, a crank angle determiner 71, an engine controller 73, a fuel injection controller 74, an ignition controller 75, a memory 76, and a rotational speed determiner 81.

[0137] In this embodiment, the memory 76 stores rotational speed data as map data in which the temperature of the engine 10 and the target rotational speed A of the crankshaft 46 when starting the engine are associated with each other in advance, in addition to the injection time data similar to the first modality.

[0138] The rotational speed determiner 81 determines, using the rotational speed data stored in memory 76, the target rotational speed A of the crankshaft 46 at engine start according to the engine temperature measured by the engine temperature sensor. motor 28. The motor controller 73 controls an inverter 62 using the target rotational speed A determined by the rotational speed determiner 81 to thereby drive a permanent magnet starter 30 such that the crankshaft 46 reaches the target rotation speed A.

[0139] The fuel injection controller 74 determines, using the rotational speed data stored in the memory 76, a fuel injection time according to the engine temperature measured by the engine temperature sensor 28. The method for determining the fuel injection time is similar to the first modality. The fuel injection time can be determined according to the crankshaft rotation speed 46.

[0140] Part of the configuration of ECU 80, except for the configuration described above, is similar to that of ECU 32 of the first mode, and detailed description of the ECU will be omitted.

[0141] Setting this mode can also obtain the time to vaporization of fuel supplied in an inlet port 33a. As a result, the energy obtained by the first combustion can be increased sufficiently so that the starting capability of the engine 10 can be improved.

Other Modalities

[0142] The embodiments of the present description have been described above, but the embodiments are mere examples for carrying out the present description. Thus, the present description is not limited to the modalities, and the modalities may be modified as necessary within a range that does not depart from the essence of the present description.

[0143] The modalities described above were aimed at engine units using four stroke single cylinder engines. The engines, however, can be either a parallel twin-cylinder four-stroke engine or a V-twin cylinder engine.

[0144] The modalities described above were directed to the case where the crankshaft 46 rotates in the reverse direction when starting the engine. However, the present description is not limited to these embodiments, and the crankshaft 46 may not rotate in the reverse direction and may rotate in the normal direction when starting the engine.

[0145] The permanent magnet starter 30 used in each mode can be either a brushed motor or a brushless motor. The starter motor can be a starter motor generator also serving as an electrical generator.

[0146] In the embodiments described above, the fuel injection device 54 injects fuel towards the inlet valve 50, but may inject fuel towards another position in the inlet passage 33a. For example, the fuel injection device 54 may inject fuel towards a position upstream of the inlet valve 50 and located on an inner surface of the wall constituting the inlet passage 33a.

[0147] In this case, the injection time data can be configured so that the injection time is longer than in the case of injecting fuel towards the inlet valve 50. That is, as shown in Figure 11, a target rotational speed A of the crankshaft 46 in the case of injecting fuel towards the inner surface A of the wall constituting the inlet passage 33a is lower than that in the case of injecting fuel towards the inlet valve 50.

[0148] The modalities described above are directed to the configurations in which the engine units 100 and 101 are applied to motorcycles. Alternatively, the engine units 100 and 101 can be applied to other vehicles, such as tricycles or four-wheeled vehicles.

[0149] In the modalities described above, the temperature of an engine coolant is measured as the temperature of the engine 10. In the case of an air-cooled engine, for example, the temperature of the oil in an oil passage in which the Lubricating oil flows can be measured as engine temperature.

[0150] Although engine 10 uses TPS 22 in the above embodiments, engine 10 may use a throttle position sensor instead of TPS 22.

[0151] In the first embodiment, the motor unit 100 includes the decompression mechanism 58. The motor unit 101 in the second embodiment may also include a decompression mechanism. Motor unit 100 may not include a decompression mechanism. Description of Part Numbers Four-stroke engine body Air filter Intake pipe Exhaust pipe TPS throttle device Pressure sensor Crank angle sensor (Crank angle sensor) Engine temperature sensor (Crank Engine temperature sensor) permanent magnet starter ECU (control device) Inlet port Exhaust port Inlet port Exhaust port Cylinder head Combustion chamber Cylinder Piston Crankcase Crankshaft Connecting rod Inlet valve Exhaust valve Fuel injection device Ignition plug ( ignition device) Decompression mechanism Inverter Battery Starter Rotation speed calculator Crank angle determiner Fuel injection timer Engine controller Fuel injection timing controller Ignition controller Memory Rotation speed determiner 101 Unit of engine

Claims (13)

1. An engine unit (100, 101) comprising: a four-stroke engine body (10) including a combustion chamber (36) having an inlet port (35a) and an exhaust port (35b), a inlet (50) configured to open and close the inlet port (35a), an exhaust valve (52) configured to open and close the exhaust port (35b), an inlet passage (33a) connected to the inlet port ( 35a) and configured to guide atmospheric air into the combustion chamber (36) through the inlet port (35a), an exhaust passage (33b) connected to the exhaust port (35b), a fuel injection device (54) ) configured to inject fuel into the inlet passage (33a), an igniter (56) configured to ignite an air-fuel mixture including fuel and air in the combustion chamber (36), a piston (42) configured to move forwards and backwards in the combustion chamber (36), and a crankshaft (46) connected to the floor so (42) to rotate in accordance with the back and forth movement of the piston (42), wherein a region of high load (TH) where a load to rotate the crankshaft (46) is high and a region of low load (TL) where a load to rotate the crankshaft (46) is less than the load in the high load region (TH) are present in four strokes; a permanent magnet starter (30) that includes a permanent magnet and is configured to rotate the crankshaft (46); a control device (32) which is configured to control the permanent magnet starter (30), the fuel injection device (54) and the igniter device (56); an engine temperature detector (28) which is configured to sense a four-stroke engine body temperature (10); and a crank angle detector (26) which is configured to detect a crank angle, the crank angle being a position of an angle of rotation of the crankshaft (46), CHARACTERIZED by the fact that the control device (32) is configured to drive the permanent magnet starter (30) to rotate the crankshaft (46) from a stopped state, control the fuel injection device (54) while a crank angle of the crankshaft (46) is at low load region (TL), thereby injecting fuel into the intake passage (33a), controlling a rotational speed of the permanent magnet starter (30) so that an increase in a rotational speed of the crankshaft (46) is suppressed and the time for fuel vaporization is obtained, based on the four-stroke engine body temperature (10) detected by the engine temperature detector (28) while the crankshaft crank angle (46) is in the low region. load (TL) and the from when the fuel injection device (54) injects fuel into the inlet passage (33a) to when the inlet valve (50) is closed, and starting the four-stroke engine body (10) by igniting the fuel mixture. air-fuel in the combustion chamber (36) using the igniter (56) while the crank angle of the crankshaft (46) is in the high load region (TH). 2. Motor unit (100, 101), according to claim 1, CHARACTERIZED in that the control device (32) is configured to control the rotational speed of the permanent magnet starter (30) so that a rotational speed of the crankshaft (46) obtained when the temperature of the four-stroke engine body (10) detected by the engine temperature detector (28) is a first temperature is less than a rotational speed of the crankshaft (46). ) obtained when the four-stroke engine body temperature (10) detected by the engine temperature detector (28) is a second temperature higher than the first temperature. 3. Engine unit (100, 101), according to claim 1 or 2, CHARACTERIZED in that the fuel injection device (54) is configured to inject fuel towards the inlet valve (50). 4. Engine unit (100, 101), according to any one of claims 1 to 3, CHARACTERIZED in that the control device (32) is configured to determine a rotational speed of the crankshaft (46) in accordance with a fuel injection time determined based on the four-stroke engine body temperature (10) detected by the engine temperature detector (28). 5. Engine unit (100, 101) according to any one of claims 1 to 4, CHARACTERIZED in that the engine temperature detector is a sensor (28) which is configured to detect a temperature of a coolant liquid of the four-stroke engine body (10) or an oil temperature in an oil passage. 6. Engine unit (100, 101), according to any one of claims 1 to 5, CHARACTERIZED in that the control device (32) is configured to cause the fuel injection device (54) to inject fuel until the fuel injection time exceeds a predetermined time at which the fuel required to start the engine is allowed to be supplied. 7. Engine unit (100, 101), according to any one of claims 1 to 6, CHARACTERIZED in that the control device (32) is configured to control the rotational speed of the engine so that, as As the four-stroke engine body temperature (10) detected by the engine temperature detector (28) decreases, the rotational speed of the crankshaft (46) at the time of fuel injection decreases. 8. Engine unit (100, 101) according to any one of claims 1 to 7, CHARACTERIZED in that the four-stroke engine body (10) additionally includes a decompression mechanism (58) which is configured to temporarily opening the exhaust valve (52) in order to eject the air-fuel mixture into the combustion chamber (36) while the crank angle of the crankshaft (46) is in the high load region (TH). 9. Method for controlling an engine unit (100, 101) having a four-stroke engine body (10) with a combustion chamber (36) having an inlet port (35a) and an exhaust port (35b), an inlet valve (50) configured to open and close the inlet port (35a), an exhaust valve (52) configured to open and close the exhaust port (35b), an inlet passage (33a) connected to the port inlet (35a) and configured to guide atmospheric air to the combustion chamber (36) through the inlet port (35a), an exhaust passage (33b) connected to the exhaust port (35b), a fuel injection device fuel (54) configured to inject fuel into the inlet passage (33a), an igniter (56) configured to ignite an air-fuel mixture including fuel and air in the combustion chamber (36), a piston (42) configured to move back and forth in the combustion chamber (36), and a crankshaft (46) connects attached to the piston (42) to rotate in accordance with the back and forth movement of the piston (42), wherein a region of high load (TH) where a load to rotate the crankshaft (46) is high and a region of low load (TL) where a load to rotate the crankshaft (46) is less than the load in the high load (TH) region are present in four stroke, a permanent magnet starter (30) that includes a permanent magnet and is configured to rotate the crankshaft (46), CHARACTERIZED in that the method comprises: detecting a four-stroke engine body temperature (10) through an engine temperature detector (28); and detecting a crank angle by means of a crank angle detector (26), the crank angle being a position of an angle of rotation of the crankshaft (46), driving the permanent magnet starter (30) to rotate the crankshaft (46). crankshaft (46) from a stopped state, controlling the fuel injection device (54) while a crank angle of the crankshaft (46) is in the low load (TL) region, thereby injecting fuel into the intake passage (33a) ), controlling a rotational speed of the permanent magnet starter (30) so that an increase in a rotational speed of the crankshaft (46) is suppressed and the time for fuel vaporization is obtained, based on the body temperature of four stroke engine (10) detected by the engine temperature detector (28) while the crank angle of the crankshaft (46) is in the low load region (TL) and from when the fuel injection device (54 ) injects fuel into the passage (33a) until when the inlet valve (50) is closed, and starting the four-stroke engine body (10) by igniting the air-fuel mixture in the combustion chamber (36) using the ignition device ( 56) while the crankshaft crank angle (46) is in the high load region (TH). 10. Method for controlling a motor unit (100, 101), according to claim 9, CHARACTERIZED in that it further comprises: controlling the rotational speed of the permanent magnet starter (30) so that a speed of crankshaft (46) rotation obtained when the four-stroke engine body (10) temperature detected by the engine temperature detector (28) is a first temperature is less than a crankshaft rotational speed (46) obtained when the four-stroke engine body temperature (10) detected by the engine temperature detector (28) is a second temperature higher than the first temperature. 11. Method for controlling an engine unit (100, 101), according to claim 9 or 10, CHARACTERIZED in that it further comprises: determining a rotational speed of the crankshaft (46) according to an injection time of fuel determined based on the four-stroke engine body temperature (10) detected by the engine temperature detector (28). 12. Method for controlling an engine unit (100, 101) according to any one of claims 9 to 11, CHARACTERIZING in that it further comprises: causing the fuel injection device (54) to inject fuel until the fuel injection time exceeds a predetermined time at which the fuel required to start the engine is allowed to be supplied. 13. Method for controlling an engine unit (100, 101), according to any one of claims 9 to 12, CHARACTERIZED in that it further comprises: controlling the rotational speed of the engine so that, as the temperature of the four-stroke engine body (10) detected by the engine temperature detector (28) decreases, the rotational speed of the crankshaft (46) at the time of fuel injection decreases.

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