WO2016051629A1

WO2016051629A1 - Engine system and vehicle

Info

Publication number: WO2016051629A1
Application number: PCT/JP2015/003330
Authority: WO
Inventors: 貴裕増田; 坂井　浩二
Original assignee: ヤマハ発動機株式会社
Priority date: 2014-09-30
Filing date: 2015-07-02
Publication date: 2016-04-07
Also published as: TWI610021B; EP3203056A4; TW201619495A; EP3203056A1

Abstract

Provided is an engine system in which an ECU controls an engine and a starter/generator so that an engine start operation that includes at least a reverse rotation start operation is carried out. During the reverse rotation start operation, a crankshaft is rotated in a reverse direction while an air-fuel mixture is introduced into a first cylinder, and the crankshaft is driven in the forward direction by combustion of the air-fuel mixture within the first cylinder. A decompression mechanism reduces the pressure within the first cylinder or within another cylinder so that increases in the rotational resistance of the crankshaft caused by an increase in the pressure within the first cylinder or within another cylinder are minimized during the engine start operation.

Description

Engine system and vehicle

The present invention relates to an engine system and a vehicle including the same.

In order to improve the startability of the engine, there is a technique for rotating the crankshaft in the reverse direction when starting the engine and burning the air-fuel mixture in the cylinder. In the engine start control device described in Patent Document 1, an air-fuel mixture is introduced into a specific cylinder when the engine is stopped in the idle stop control, and the crankshaft is stopped while the cylinder is in an expansion stroke. . Thereafter, when the engine is restarted, the crankshaft is reversely rotated so that the piston in the specific cylinder returns to the initial position of the expansion stroke or the vicinity thereof, and the air-fuel mixture in the cylinder is ignited.
JP 2005-180380 A

In the idle stop control, the engine is stopped and restarted automatically. In this case, since the engine stop time is relatively short, the air-fuel mixture introduced into the cylinder when the engine is stopped is highly likely to remain in the cylinder even when the engine is restarted. On the other hand, when the engine stop time becomes longer, the air-fuel mixture in the cylinder disappears naturally. For this reason, the above operation cannot be realized at the time of cold start or the like.

Also, even if the engine stop time is short, the air-fuel mixture in the cylinder is diluted during that time. Therefore, it is difficult to properly adjust the air-fuel ratio in the cylinder at the time of ignition.

For these reasons, the technology described in the above document may not be able to start the engine properly.

An object of the present invention is to provide an engine system and a vehicle that can appropriately start the engine.

(1) An engine system according to one aspect of the present invention has an engine start operation including an engine having a plurality of cylinders, a rotation drive unit that rotates the crankshaft of the engine in the forward direction and the reverse direction, and at least a reverse rotation start operation. A plurality of cylinders including first and second cylinders, and in the reverse rotation start operation, the first rotation is performed while the crankshaft is rotated in the reverse direction. The air-fuel mixture is introduced into the first cylinder, and the air-fuel mixture is combusted in the first cylinder, whereby the crankshaft is driven in the forward direction. The engine is installed in at least one of the first and second cylinders. The pressure reducing mechanism includes a pressure reducing mechanism that reduces the pressure, and the pressure reducing mechanism suppresses an increase in rotational resistance of the crankshaft caused by an increase in pressure in at least one of the cylinders in the engine starting operation. Cormorant to reduce the pressure in at least one cylinder.

In this engine system, the engine is started by an engine start operation including at least a reverse rotation start operation. In the reverse rotation starting operation, the air-fuel mixture is introduced into the first cylinder among the plurality of cylinders while the crankshaft is reversely rotated, and the air-fuel mixture is combusted in the first cylinder, so that the crankshaft is driven in the forward direction. Is done. In this case, since the time from when the air-fuel mixture is introduced into the first cylinder until the air-fuel mixture is ignited is short, the air-fuel mixture in the first cylinder is prevented from being lost or diluted, and at the time of ignition. The air-fuel ratio of the air-fuel mixture in can be adjusted appropriately.

In the engine starting operation, the pressure in the at least one of the first and second cylinders is reduced by the pressure reducing mechanism, so that the rotation resistance of the crankshaft caused by the increase in the pressure in at least one of the cylinders. Increase is suppressed. Thereby, the engine starting operation is smoothly performed without hindering the rotation of the crankshaft. Therefore, the torque in the forward direction of the crankshaft can be sufficiently increased by the reverse rotation starting operation. As a result, the engine can be started properly.

(2) The pressure reducing mechanism may reduce the pressure in at least one of the cylinders in the reverse rotation starting operation.

In this case, in the reverse rotation starting operation, an increase in the rotational resistance of the crankshaft due to the increase in the pressure in the at least one cylinder is suppressed, so that the reverse rotation of the crankshaft is not hindered. Thereby, reverse rotation starting operation can be performed appropriately.

(3) The engine further includes an opening / closing mechanism that opens and closes the intake port and the exhaust port of each of the first and second cylinders, and the intake stroke, compression stroke, expansion stroke, and exhaust stroke of the first cylinder during normal operation. Are defined as a first intake range, a first compression range, a first expansion range, and a first exhaust range, and the intake stroke and compression stroke of the second cylinder during normal operation are defined. The ranges of the crank angle corresponding to the expansion stroke and the exhaust stroke are defined as a second intake range, a second compression range, a second expansion range, and a second exhaust range, respectively. The first expansion range includes the start ignition range, and the rotational drive unit reverses the crankshaft so that the crank angle exceeds the start intake range and reaches the start ignition range in the reverse rotation start operation. Rotate and open In the reverse rotation start operation, the mechanism opens the intake port of the first cylinder when the crank angle is in the start intake range, and the fuel injection device corresponding to the first cylinder has the crank angle in the reverse rotation start operation. The ignition device corresponding to the first cylinder is reversely injected by injecting fuel into the intake passage that guides air to the first cylinder so that the air-fuel mixture is introduced into the first cylinder when in the starting intake air range. In the rotation start operation, the air-fuel mixture in the first cylinder is ignited when the crank angle is in the start ignition range, the second expansion range includes a start pressure reduction range, and the pressure reduction mechanism is in the reverse rotation start operation. The pressure in the second cylinder may be reduced when the crank angle is in the start pressure reduction range.

In this case, in the reverse rotation start operation, the crankshaft is reversely rotated so that the crank angle reaches the start ignition range via the start intake range. When the crank angle is in the start intake range, the intake port of the first cylinder is opened, and the air-fuel mixture is introduced into the first cylinder. Thereafter, when the crank angle is within the starting ignition range, the air-fuel mixture in the first cylinder is ignited. The crankshaft is driven in the positive direction by the combustion energy of the air-fuel mixture.

When the crank angle is within the start pressure reduction range, the pressure in the second cylinder is reduced by the pressure reduction mechanism. Thereby, even if the crank angle approaches an angle corresponding to the compression top dead center of the second cylinder, an increase in the pressure in the second cylinder is suppressed. For this reason, an increase in the rotational resistance of the crankshaft is suppressed, so that the reverse rotation of the crankshaft is not hindered.

Since the pressure in the second cylinder does not hinder the reverse rotation of the crankshaft, it is possible to appropriately introduce the air-fuel mixture into the first cylinder and compress the air-fuel mixture in the first cylinder. Thereby, the air-fuel mixture can be appropriately combusted in the first cylinder, and the torque in the positive direction of the crankshaft can be sufficiently increased. As a result, the engine can be started properly.

(4) At least one of the first compression range and the first intake range includes a reverse rotation start range, and the engine start operation is performed by rotating the crankshaft in the forward direction before the reverse rotation start operation. May further include a forward rotation alignment operation for adjusting to the reverse rotation start range.

In this case, since the crank angle is adjusted to the reverse rotation start range before the reverse rotation start operation, the reverse rotation speed of the crankshaft is increased before the crank angle reaches the start intake range in the reverse rotation start operation. Therefore, the air-fuel mixture is appropriately introduced into the first cylinder in the start intake range, and the crank angle easily reaches the start ignition range. Thereby, the air-fuel mixture can be appropriately combusted in the first cylinder.

(5) The second compression range includes an alignment decompression range, and the decompression mechanism reduces the pressure in the second cylinder when the crank angle is in the alignment decompression range in the forward rotation alignment operation. Also good.

In this case, even if the crank angle approaches the angle corresponding to the compression top dead center of the second cylinder, the pressure increase in the second cylinder is suppressed. For this reason, an increase in the rotational resistance of the crankshaft is suppressed, so that normal rotation of the crankshaft is not hindered. Thereby, the crank angle can be easily adjusted to the reverse rotation start range.

(6) The difference between the crank angle when the piston reaches compression top dead center in the first cylinder and the crank angle when the piston reaches compression top dead center in the second cylinder may be 360 degrees. .

In this case, during normal operation of the engine, the combustion of the air-fuel mixture in the first cylinder and the combustion of the air-fuel mixture in the second cylinder are performed at equal intervals. Even in such an engine, the air-fuel mixture can be appropriately combusted in the first cylinder during the reverse rotation start operation. Thereby, the engine can be started appropriately.

(7) In the reverse rotation start operation, the fuel injection device corresponding to the second cylinder supplies air to the second cylinder after the crank angle exceeds the start intake range and before the start ignition range. Fuel may be injected into the intake passage that leads.

In this case, when the crank angle reaches the start ignition range and the forward rotation of the crankshaft is started, the second cylinder is in the intake stroke. Therefore, before the crank angle reaches the starting ignition range, fuel is injected into the intake passage that guides air to the second cylinder, and immediately after the crankshaft starts to rotate forward, the second cylinder A mixture is introduced. Thereby, the air-fuel mixture can be combusted in the second cylinder in the first expansion stroke of the second cylinder. Therefore, the engine can be started quickly.

(8) The difference between the crank angle when the piston reaches the compression top dead center in the first cylinder and the crank angle when the piston reaches the compression top dead center in the second cylinder is an angle other than 360 degrees. May be.

In this case, during normal operation of the engine, the combustion of the air-fuel mixture in the first cylinder and the combustion of the air-fuel mixture in the second cylinder are performed at unequal intervals. Even in such an engine, the air-fuel mixture can be appropriately combusted in the first cylinder during the reverse rotation start operation. Thereby, the engine can be started appropriately.

(9) The engine start operation further includes a forward rotation alignment operation for adjusting the crank angle to the reverse rotation start range by rotating the crankshaft in the forward direction before the reverse rotation start operation. In the alignment operation, the pressure in at least one of the first and second cylinders may be reduced.

In this case, since the crank angle is adjusted to the reverse rotation start range before the reverse rotation start operation, the air-fuel mixture can be appropriately introduced into the first cylinder in the reverse rotation start operation, and the mixture is sufficiently Can be compressed. Thereby, the air-fuel mixture can be appropriately combusted in the first cylinder.

Further, in the forward rotation alignment operation, an increase in the rotational resistance of the crankshaft due to an increase in the pressure in at least one of the first and second cylinders is suppressed, so that the forward rotation of the crankshaft is hindered. I can't. Thereby, the forward rotation alignment operation can be appropriately performed.

(10) The engine further includes an opening / closing mechanism that opens and closes an intake port and an exhaust port of each of the first and second cylinders, and an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke of the first cylinder during normal operation. Are defined as a first intake range, a first compression range, a first expansion range, and a first exhaust range, and the intake stroke and compression stroke of the second cylinder during normal operation are defined. The ranges of crank angles corresponding to the expansion stroke and the exhaust stroke are defined as a second intake range, a second compression range, a second expansion range, and a second exhaust range, respectively. The first exhaust range includes the start intake range, the first expansion range includes the start ignition range, and the rotation drive unit starts the reverse rotation of the crank angle in the forward rotation alignment operation. I'm reaching the range In the reverse rotation start operation, the crankshaft is reversely rotated so that the crank angle exceeds the start intake range from the reverse rotation start range to the start ignition range, and the open / close mechanism starts reverse rotation. In operation, when the crank angle is in the start intake range, the intake port of the first cylinder is opened, and the fuel injection device corresponding to the first cylinder is in the reverse rotation start operation when the crank angle is in the start intake range. So that the air-fuel mixture is introduced into the first cylinder, the fuel is injected into the intake passage that guides air to the first cylinder, and the ignition device corresponding to the first cylinder The air-fuel mixture in the first cylinder is ignited when the angle is in the starting ignition range, the first compression range includes an alignment decompression range, and the decompression mechanism has a crank angle position in the forward rotation alignment operation. Combined decompression range The pressure in the first cylinder may be lowered when in.

In this case, after the crank angle is adjusted to the reverse rotation start range by the normal rotation alignment operation, the crank angle reaches the start ignition range from the reverse rotation start range via the start intake range by the reverse rotation start operation. The crankshaft is reversely rotated.

In the reverse rotation start operation, when the crank angle is in the start intake range, the intake port of the first cylinder is opened, and the air-fuel mixture is introduced into the first cylinder. Thereafter, when the crank angle is within the starting ignition range, the air-fuel mixture in the first cylinder is ignited, and the crankshaft is driven in the positive direction by the energy of the combustion.

Since the forward rotation alignment operation is performed before the reverse rotation start operation, the reverse rotation speed of the crankshaft is increased before the crank angle reaches the start intake range in the reverse rotation start operation. As a result, the air-fuel mixture is appropriately introduced into the first cylinder in the start intake range, and the crank angle easily reaches the start ignition range.

Thus, the air-fuel mixture can be appropriately burned in the first cylinder, and the torque in the positive direction of the crankshaft can be sufficiently increased. As a result, the engine can be started properly.

In the forward rotation alignment operation, when the crank angle is in the alignment pressure reduction range, the pressure in the first cylinder is reduced by the pressure reduction mechanism. In this case, even if the crank angle approaches an angle corresponding to the compression top dead center of the first cylinder, an increase in pressure in the first cylinder is suppressed. For this reason, an increase in the rotational resistance of the crankshaft is suppressed, so that normal rotation of the crankshaft is not hindered. Thereby, the crank angle can be easily adjusted to the reverse rotation start range.

(11) At least a part of the first intake range is in the second compression range, and the crank angle passes through an angle corresponding to the compression top dead center of the first and second cylinders in the reverse rotation start operation. The starting ignition range may be reached without doing so.

In this case, in the reverse rotation starting operation, the crank angle does not pass through the angle corresponding to the compression top dead center of the first and second cylinders, so that the crank pressure can be reduced without reducing the pressure in the first and second cylinders. The shaft can easily reach the starting ignition range. Accordingly, the forward rotation alignment operation and the reverse rotation start operation can be appropriately performed with a simple configuration.

(12) The plurality of cylinders may further include a third cylinder, and the pressure reducing mechanism may reduce the pressure in the second and third cylinders in the reverse rotation operation.

In this case, in the reverse rotation starting operation, an increase in the rotational resistance of the crankshaft due to the increase in pressure in the second or third cylinder is suppressed, and the reverse rotation of the crankshaft is not hindered. Thereby, in the multi-cylinder engine having three or more cylinders, the reverse rotation starting operation can be appropriately performed, and the engine can be appropriately started.

(13) The engine start operation includes a forward rotation alignment operation that adjusts the crank angle to a predetermined reverse rotation start range by rotating the crankshaft in the forward direction before the reverse rotation start operation. In the forward rotation alignment operation, the pressures in the second and third cylinders may be reduced.

In this case, since the crank angle is adjusted to the reverse rotation start range before the reverse rotation start operation, the air-fuel mixture can be appropriately introduced into the first cylinder in the reverse rotation start operation, and the crank angle can be easily set. The starting ignition range can be reached. Thereby, the air-fuel mixture can be appropriately combusted in the first cylinder.

Also, in the forward rotation alignment operation, an increase in the rotational resistance of the crankshaft due to an increase in pressure in the second or third cylinder is suppressed, so that the forward rotation of the crankshaft is not hindered. Thereby, in the multi-cylinder engine having three or more cylinders, the forward rotation alignment operation can be appropriately performed.

(14) The decompression mechanism includes a communication path that communicates the second cylinder and the third cylinder, and a communication path opening / closing mechanism that switches the communication path between a communication state and a closed state. The pressure in the second and third cylinders may be reduced by bringing the passage into a communicating state.

In this case, an increase in the rotational resistance of the crankshaft due to an increase in pressure in the second or third cylinder can be suppressed with a simple configuration and simple control.

(15) The communication path has a first opening that opens in the second cylinder and a second opening that opens in the third cylinder, and the communication path opening and closing mechanism opens and closes the first opening. A valve, a second valve that opens and closes the second opening, and a communication drive unit that integrally drives the first and second valves. The communication drive unit includes the first and second valves. Thus, the pressures in the second and third cylinders may be lowered by opening the first and second openings.

In this case, the communication path can be appropriately switched between the communication state and the closed state with a simple configuration.

(16) A vehicle according to another aspect of the present invention includes a main body having driving wheels and the engine system that generates power for rotating the driving wheels.

Since this engine system is used in this vehicle, the engine can be started appropriately.

(17) The decompression mechanism may be configured to reduce the pressure in the second cylinder in the start decompression range when the crank angle rotates at a rotational speed lower than a predetermined value.

In this case, with a simple configuration, the pressure in the second cylinder can be reduced during the reverse rotation start operation.

(18) The pressure reducing mechanism may be configured to reduce the pressure in the first or second cylinder in the alignment pressure reducing range when the crankshaft rotates at a rotational speed lower than a predetermined value.

In this case, the pressure in the first or second cylinder can be reduced with a simple configuration during the forward rotation alignment operation.

According to the present invention, the engine can be started appropriately.

FIG. 1 is a schematic side view showing a schematic configuration of a motorcycle according to an embodiment of the present invention. FIG. 2 is a schematic side view for explaining the configuration of the engine system according to the first embodiment. FIG. 3 is a schematic side view for explaining the configuration of the engine system according to the first embodiment. FIG. 4 is a diagram for explaining the operation of the engine during normal operation in the first embodiment. FIG. 5 is a diagram for explaining the operation of the engine during normal operation in the first embodiment. FIG. 6 is a diagram for explaining the forward rotation alignment operation of the engine unit in the first embodiment. FIG. 7 is a diagram for explaining the reverse rotation start operation of the engine unit in the first embodiment. FIG. 8 is a diagram showing the relationship between the rotational load of the crankshaft and the crank angle in the first embodiment. FIG. 9 is a flowchart for explaining an example of the engine start process in the first embodiment. FIG. 10 is a flowchart for explaining an example of the engine start process in the first embodiment. FIG. 11 is a diagram for explaining another example of the reverse rotation starting operation in the first embodiment. FIG. 12 is a diagram for explaining another example of the reverse rotation starting operation in the first embodiment. FIG. 13 is a schematic side view for explaining the configuration of the engine system according to the second embodiment. FIG. 14 is a diagram for explaining the operation of the engine during normal operation in the second embodiment. FIG. 15 is a view for explaining the forward rotation alignment operation of the engine unit in the second embodiment. FIG. 16 is a view for explaining the forward rotation alignment operation of the engine unit in the second embodiment. FIG. 17 is a diagram for explaining the reverse rotation start operation of the engine unit in the second embodiment. FIG. 18 is a diagram for explaining the reverse rotation start operation of the engine unit in the second embodiment. FIG. 19 is a diagram showing the relationship between the rotational load of the crankshaft and the crank angle in the second embodiment. FIG. 20 is a flowchart of the engine start process in the second embodiment. FIG. 21 is a schematic diagram illustrating an example of a valve drive unit according to the second embodiment. FIG. 22 is a perspective view showing a decompression mechanism according to the second embodiment. FIG. 23 is a schematic cross-sectional view for explaining the operating state of the decompression mechanism in the second embodiment. FIG. 24 is a schematic cross-sectional view for explaining the inoperative state of the decompression mechanism in the second embodiment. FIG. 25 is a diagram for explaining the configuration of the engine unit according to the third embodiment. FIG. 26 is a diagram for explaining the normal operation of the engine according to the third embodiment. FIG. 27 is a diagram for explaining the normal operation of the engine according to the third embodiment. FIG. 28 is a diagram for explaining the normal operation of the engine according to the third embodiment. FIG. 29 is a diagram showing the relationship between the rotational load of the crankshaft and the crank angle in the third embodiment. FIG. 30 is a view for explaining the forward rotation alignment operation in the third embodiment. FIG. 31 is a diagram for explaining the reverse rotation starting operation in the third embodiment. FIG. 32 is a diagram showing a specific example of the decompression mechanism in the third embodiment. FIG. 33 is a diagram for explaining the operation in the second and third cylinders in the third embodiment. FIG. 34 is a schematic diagram for explaining the flow of gas during the forward rotation alignment operation in the third embodiment. FIG. 35 is a diagram for explaining the operation in the second and third cylinders in the third embodiment. FIG. 36 is a schematic diagram for explaining the gas flow during the reverse rotation starting operation in the third embodiment. FIG. 37 is a diagram showing the relationship between the crankshaft rotational load and the crank angle during the forward rotation alignment operation and the reverse rotation start operation in the third embodiment. FIG. 38 is a flowchart for explaining a cold start process in the third embodiment. FIG. 39 is a flowchart for explaining a cold start process in the third embodiment. FIG. 40 is a flowchart for explaining reverse rotation start processing in the third embodiment.

Hereinafter, an engine system and a vehicle according to an embodiment of the present invention will be described with reference to the drawings.

[A] Vehicle FIG. 1 is a schematic side view showing a schematic configuration of a motorcycle according to an embodiment of the present invention. The motorcycle 100 in FIG. 1 is an example of a vehicle. In the motorcycle 100 of FIG. 1, a front fork 2 is provided at the front portion of the vehicle body 1 so as to be swingable in the left-right direction. A handle 4 is attached to the upper end of the front fork 2, and a front wheel 3 is rotatably attached to the lower end of the front fork 2.

The seat 5 is provided at the substantially upper center of the vehicle body 1. Below the seat 5, an ECU (Engine Control Unit) 6 and an engine unit EU are provided. The engine system 200 is configured by the ECU 6 and the engine unit EU. A rear wheel 7 is rotatably attached to the lower rear end of the vehicle body 1. The rear wheel 7 is rotationally driven by the power generated by the engine unit EU.

[B] Engine system (first embodiment)
(1) Configuration FIGS. 2 and 3 are schematic side views for explaining the configuration of the engine system 200 according to the first embodiment of the present invention. As shown in FIG. 2, the engine unit EU includes an engine 10 and a starter / generator 14. The engine 10 is a two-cylinder four-cycle engine and includes a first cylinder 31A and a second cylinder 31B. A piston 11 is provided in each of the first and

second cylinders

31A and 31B. Each piston 11 is connected to a crankshaft 13 via a connecting rod (connecting rod) 12. The reciprocating motion of each piston 11 is converted into the rotational motion of the crankshaft 13.

The starter / generator 14 is provided on the crankshaft 13. The starter / generator 14 is a generator having a function of a starter motor, and rotates the crankshaft 13 in the forward direction and the reverse direction and generates electric power by the rotation of the crankshaft 13. The forward direction is the direction of rotation of the crankshaft 13 during normal operation of the engine 10, and the reverse direction is the opposite direction. The starter / generator 14 directly transmits torque to the crankshaft 13 without using a reduction gear. The rotation of the crankshaft 13 in the positive direction (forward rotation) is transmitted to the rear wheel 7 so that the rear wheel 7 is rotationally driven. Instead of the starter / generator 14, a starter motor and a generator may be provided separately.

FIG. 3 shows only the first cylinder 31A among the first and

second cylinders

31A and 31B. The configuration of the second cylinder 31B and its peripheral portion is the same as the configuration of the first cylinder 31A and its peripheral portion.

As shown in FIG. 3, the engine 10 includes an intake valve 15, an exhaust valve 16, a spark plug 18, an injector 19, and a valve drive unit 17. The intake valve 15, the exhaust valve 16, the spark plug 18, and the injector 19 are provided so as to correspond to each of the first and

second cylinders

31A and 31B, and the valve drive unit 17 includes the first and second cylinders 31A. , 31B.

A combustion chamber 31a is formed above the piston 11 in each of the first and

second cylinders

31A and 31B. The combustion chamber 31 a communicates with the intake passage 22 through the intake port 21 and communicates with the exhaust passage 24 through the exhaust port 23. The intake valve 15 opens and closes the intake port 21, and the exhaust valve 16 opens and closes the exhaust port 23. The intake valve 15 and the exhaust valve 16 are driven by the valve drive unit 17. The intake passage 22 is provided with a throttle valve TV for adjusting the flow rate of air flowing from the outside. The spark plug 18 is configured to ignite the air-fuel mixture in the combustion chamber 31a. The injector 19 is configured to inject fuel into the intake passage 22.

The engine 10 includes a decompression mechanism DE for reducing the pressure in the first cylinder 31A. The decompression mechanism DE, for example, lowers the pressure in the first cylinder 31A by lifting the exhaust valve 16 corresponding to the first cylinder 31A.

ECU6 contains CPU (central processing unit) and memory, for example. A microcomputer may be used instead of the CPU and the memory. A main switch 40, a starter switch 41, an intake pressure sensor 42, a crank angle sensor 43, and a current sensor 44 are electrically connected to the ECU 6. The main switch 40 is provided, for example, below the handle 4 in FIG. 1, and the starter switch 41 is provided, for example, in the handle 4 in FIG. The main switch 40 and the starter switch 41 are operated by the driver. The intake pressure sensor 42 detects the pressure in the intake passage 22. The crank angle sensor 43 detects the rotational position of the crankshaft 13 (hereinafter referred to as the crank angle). The current sensor 44 detects a current (hereinafter referred to as a motor current) flowing through the starter / generator 14.

The operation of the main switch 40 and the starter switch 41 is given to the ECU 6 as operation signals, and the detection results by the intake pressure sensor 42, the crank angle sensor 43 and the current sensor 44 are given to the ECU 6 as detection signals. The ECU 6 controls the starter / generator 14, the spark plug 18, and the injector 19 based on the given operation signal and detection signal.

(2) Operation of Engine System For example, the engine 10 is started when the starter switch 41 of FIG. 3 is turned on, and the engine 10 is stopped when the main switch 40 of FIG. 3 is turned off. Further, the engine 10 may be automatically stopped when a predetermined idle stop condition is satisfied, and then the engine 10 may be automatically restarted when a predetermined idle stop cancellation condition is satisfied. . The idle stop condition includes, for example, a condition relating to at least one of a throttle opening (opening of the throttle valve TV), a vehicle speed, and a rotational speed of the engine 10. The idling stop release condition is, for example, that the throttle opening is larger than 0 when the accelerator grip is operated. Hereinafter, a state where the engine 10 is automatically stopped when the idle stop condition is satisfied is referred to as an idle stop state.

In this embodiment, after the engine 10 is started by the engine start operation, the engine 10 shifts to normal operation. The engine start operation includes a forward rotation alignment operation and a reverse rotation start operation which will be described later. In the normal operation, the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke are periodically repeated in each of the first and

second cylinders

31A and 31B.

In the following description, the top dead center through which the piston 11 passes during the transition from the compression stroke to the expansion stroke is referred to as the compression top dead center, and the top dead center through which the piston 11 passes during the transition from the exhaust stroke to the intake stroke. Called dead point. Also, the bottom dead center through which the piston 11 passes during the transition from the intake stroke to the compression stroke is called the intake bottom dead center, and the bottom dead center through which the piston 11 passes during the transition from the expansion stroke to the exhaust stroke is called the expansion bottom dead center. Call.

The crank angle ranges corresponding to the intake stroke, compression stroke, expansion stroke, and exhaust stroke of the first cylinder 31A during normal operation are defined as the first intake range, the first compression range, the first expansion range, and This is called the first exhaust range. In addition, the crank angle ranges corresponding to the intake stroke, compression stroke, expansion stroke, and exhaust stroke of the second cylinder 31B during normal operation are defined as the second intake range, second compression range, second expansion range, and This is called the second exhaust range.

The crank angle is expressed in a range of 720 degrees (two rotations of the crankshaft 13). The crank angle sensor 43 in FIG. 3 detects the rotational position of the crankshaft 13 in the range of one rotation (360 degrees). The ECU 6 determines whether the rotational position detected by the crank angle sensor 43 based on the pressure in the intake passage 22 detected by the intake pressure sensor 42 is one of the two rotations of the crankshaft 13 corresponding to one cycle of the engine 10. It is determined whether it corresponds to the rotation of. Thereby, the ECU 6 can acquire the rotational position of the crankshaft 13 in the range of two rotations (720 degrees).

(2-1) Normal Operation FIGS. 4 and 5 are diagrams for explaining the normal operation of the engine 10. FIG. 4 shows the relationship between the operation in the first cylinder 31A and the crank angle, and FIG. 5 shows the relationship between the operation in the second cylinder 31B and the crank angle. 4 and 5 and a plurality of drawings to be described later, a range of 720 degrees of the crank angle is represented by one circle.

As shown in FIG. 4, in the first cylinder 31A, when the crank angle is the angle A1, the piston 11 is positioned at the compression top dead center, and when the crank angle is the angle A2, the piston 11 is expanded and dead. The piston 11 is located at the exhaust top dead center when the crank angle is the angle A3, and the piston 11 is located at the intake bottom dead center when the crank angle is the angle A4.

During normal operation, the crankshaft 13 (FIG. 2) is rotated forward. During the forward rotation of the crankshaft 13, the crank angle changes in the direction of the arrow R1. In the first cylinder 31A, as indicated by arrows P11 to P14, the piston 11 (FIG. 2) is lowered in the range from the angle A1 to the angle A2, and the piston 11 is raised in the range from the angle A2 to the angle A3. Then, the piston 11 descends in the range from the angle A3 to the angle A4, and the piston 11 rises in the range from the angle A4 to the angle A1.

The range from angle A3 to angle A4 corresponds to the first intake range, the range from angle A4 to angle A1 corresponds to the first compression range, and the range from angle A1 to angle A2 is the first expansion range. The range from the angle A2 to the angle A3 corresponds to the first exhaust range.

The intake port 21 (FIG. 3) is opened by the intake valve 15 (FIG. 3) in the range from the angle A11 to the angle A12, and the exhaust port 23 (FIG. 3) is opened by the exhaust valve 16 (FIG. 3) in the range from the angle A13 to the angle A14. 3) is opened. The angle A11 is in the first exhaust range and is positioned at a constant angle advance side with respect to the angle A3 in the positive direction, and the angle A12 is in the first compression range and is a constant angle later than the angle A4 in the positive direction. Located on the corner side. The angle A13 is in the first expansion range and is positioned at a certain angle advance side with respect to the angle A2 in the positive direction, and the angle A14 is in the first intake range and is a certain angle later than the angle A3 in the positive direction. Located on the corner side.

The fuel is injected into the intake passage 22 (FIG. 3) by the injector 19 (FIG. 3) at the angle A15, and ignited by the spark plug 18 (FIG. 3) at the angle A16. The angle A15 is in the first exhaust range and is located on the more advanced side than the angle A11 in the positive direction. The angle A16 is in the first compression range and is positioned at a certain angle advance side from the angle A1 in the positive direction.

In this case, the air-fuel mixture containing fuel injected at the angle A15 is introduced into the combustion chamber 31a through the intake port 21 in the range from the angle A11 to A12. The air-fuel mixture is compressed in the combustion chamber 31a and ignited by the spark plug 18 at an angle A16. As a result, the air-fuel mixture is combusted in the combustion chamber 31a, the piston 11 is driven by the combustion energy, and the crankshaft 13 is driven in the forward direction. Thereafter, the burned gas is discharged from the combustion chamber 31a through the exhaust port 23 in the range from the angle A13 to the angle A14.

As shown in FIG. 5, in the second cylinder 31B, when the crank angle is the angle A1, the piston 11 is located at the expansion bottom dead center, and when the crank angle is the angle A2, the piston 11 is exhausted top dead. When the crank angle is an angle A3, the piston 11 is positioned at the intake bottom dead center, and when the crank angle is the angle A4, the piston 11 is positioned at the compression top dead center.

During normal operation, as indicated by arrows P21 to P24, the piston 11 (FIG. 2) rises in the range from the angle A1 to the angle A2, and the piston 11 descends in the range from the angle A2 to the angle A3. To the angle A4, the piston 11 is raised, and the piston 11 is lowered in the range from the angle A4 to the angle A1.

The range from angle A2 to angle A3 corresponds to the second intake range, the range from angle A3 to angle A4 corresponds to the second compression range, and the range from angle A4 to angle A1 is the second expansion range. The range from the angle A1 to the angle A2 corresponds to the second exhaust range.

The intake port 21 (FIG. 3) is opened by the intake valve 15 (FIG. 3) in the range from the angle A21 to the angle A22, and the exhaust port 23 is opened by the exhaust valve 16 (FIG. 3) in the range from the angle A23 to the angle A24. It is. The angle A21 is in the second exhaust range and is positioned at a certain angle advance side from the angle A2 in the positive direction, and the angle A22 is in the second compression range and is a certain angle later than the angle A3 in the positive direction. Located on the corner side. The angle A23 is in the second expansion range and is positioned at a certain angle advance side from the angle A1 in the positive direction, and the angle A24 is in the second intake range and is a certain angle later than the angle A2 in the positive direction. Located on the corner side.

The fuel is injected into the intake passage 22 (FIG. 3) by the injector 19 (FIG. 3) at the angle A25, and ignited by the spark plug 18 (FIG. 3) at the angle A26. The angle A25 is in the second exhaust range and is located on the more advanced side than the angle A21 in the positive direction. The angle A26 is in the second compression range and is positioned at a constant angle advance side from the angle A4 in the positive direction.

In this case, the air-fuel mixture containing fuel injected at the angle A25 is introduced into the combustion chamber 31a through the intake port 21 in the range from the angle A21 to A22. The air-fuel mixture is compressed in the combustion chamber 31a and ignited by the spark plug 18 at an angle A26. As a result, the air-fuel mixture is combusted in the combustion chamber 31a, the piston 11 is driven by the combustion energy, and the crankshaft 13 is driven in the forward direction. Thereafter, the burned gas is discharged from the combustion chamber 31a through the exhaust port 23 in the range from the angle A23 to the angle A24.

In this example, the difference between the crank angle when the piston 11 reaches the compression top dead center in the first cylinder 31A and the crank angle when the piston 11 reaches the compression top dead center in the second cylinder 31B is 180 degrees. is there. Therefore, during normal operation, the air-fuel mixture is burned at unequal intervals in the first and

second cylinders

31A and 31B. Specifically, the ignition operation is performed in the second cylinder 31B after the crankshaft 13 has rotated 180 degrees after the ignition operation has been performed in the first cylinder 31A, and again after the crankshaft 13 has rotated 540 degrees. An ignition operation is performed in the first cylinder 31A.

(2-2) Forward rotation alignment operation and reverse rotation start operation The engine unit EU performs a forward rotation alignment operation before the engine 10 is started, and performs a reverse rotation start operation when the engine 10 is started. FIG. 6 is a view for explaining the forward rotation alignment operation of the engine unit EU. FIG. 7 is a diagram for explaining the reverse rotation start operation of the engine unit EU.

6 and 7 show the relationship between the operation of the first cylinder 31A and the crank angle. In this example, the main operations related to the forward rotation alignment operation and the reverse rotation start operation are performed by the first cylinder 31A. Therefore, the operation in the first cylinder 31A will be mainly described.

As shown in FIG. 6, in the forward rotation alignment operation, the crankshaft 13 is rotated forward by the starter / generator 14 (FIG. 3), so that the crank angle is adjusted to the angle A30. The angle A30 is an example of the reverse rotation start range and is in the first intake range. It is preferable that the angle A30 is located on the more retarded side than the angle A14 in the positive direction. The reverse rotation start range may be a specific angle range instead of a specific angle.

At the start of the forward rotation alignment operation, the crank angle is retarded from the angle A4 corresponding to the compression top dead center of the second cylinder 31B in the positive direction and corresponds to the compression top dead center of the first cylinder 31A. In some cases, the angle is on the more advanced side than the angle A1 (eg, angle A30a in FIG. 6). In this case, in the forward rotation alignment operation, the crank angle needs to exceed the angle A1 corresponding to the compression top dead center of the first cylinder 31A.

Therefore, in the forward rotation alignment operation, when the crank angle needs to exceed the angle A1, the crankshaft 13 is rotated forward while the pressure in the first cylinder 31A is reduced by the decompression mechanism DE. In the example of FIG. 6, the pressure in the first cylinder 31A is reduced by the decompression mechanism DE in the range from the angle AD1 to the angle AD2. The range from the angle AD1 to the angle AD2 is an example of the alignment decompression range, and is in the first compression range.

Thereby, even if the crank angle approaches the angle A1, an increase in the pressure in the first cylinder 31A is suppressed. Therefore, the forward rotation of the crank angle is not hindered, and the crank angle can be easily adjusted to the angle A30. The relationship between the forward rotation alignment operation and the decompression mechanism DE will be described later.

7, in the reverse rotation start operation, the crankshaft 13 is reversely rotated from a state where the crank angle is in the reverse rotation start range (angle A30). As a result, the crank angle changes in the direction of arrow R2. During reverse rotation of the crankshaft 13, as indicated by arrows P31 to P34, the piston 11 rises in the range from the angle A4 to the angle A3, and the piston 11 descends in the range from the angle A3 to the angle A2, and the angle A2 The piston 11 rises in the range from the angle A1 to the angle A1, and the piston 11 falls in the range from the angle A1 to the angle A4. The moving direction of the piston 11 when the crankshaft 13 rotates in the reverse direction is opposite to the moving direction of the piston 11 when the crankshaft 13 rotates in the forward direction.

In the range from the angle A31 to the angle A32, the intake port 21 (FIG. 3) is opened by the intake valve 15 (FIG. 3). Fuel is injected into the intake passage 22 (FIG. 3) by the injector 19 (FIG. 3) at an angle A33, and ignited by the spark plug 18 at an angle A34. Further, at the angle A34, the rotation direction of the crankshaft 13 is switched from the reverse direction to the forward direction.

The range from the angle A31 to the angle A32 is an example of the start intake range and is in the first exhaust range. The angle A31 is preferably positioned on the more retarded side than the angle A11 in the reverse direction. The angle A33 may be in the first exhaust range or in the first intake range. The angle A33 is preferably located on the more advanced side than the angle A31 in the reverse direction. Angle A34 is an example of the starting ignition range and is in the first expansion range. The angle A34 is at a certain angle advance side from the angle A1 in the reverse direction.

The angles A31 and A32 are in the range (first exhaust range) from the angle A3 to the angle A2. As described above, the piston 11 descends in the range from the angle A3 to the angle A2. Therefore, when the intake port 21 is opened in the range from the angle A31 to the angle A32, the air-fuel mixture containing air and fuel is introduced from the intake passage 22 into the combustion chamber 31a through the intake port 21. Thereafter, the air-fuel mixture introduced into the combustion chamber 31a is ignited at an angle A34. As a result, the crankshaft 13 is driven in the positive direction by the combustion energy of the air-fuel mixture, and the torque in the positive direction of the crankshaft 13 is increased.

Thereafter, the engine 10 shifts to the normal operation shown in FIGS. Specifically, fuel is injected into the intake passage 22 by the injector 19 corresponding to the second cylinder 31B at an angle A25 (FIG. 5) immediately after the rotation direction of the crankshaft 13 is switched, from the angle A21 to the angle A22. In this range, the air-fuel mixture is introduced into the second cylinder 31B. Thereafter, the air-fuel mixture in the second cylinder 31B is ignited by the spark plug 18 corresponding to the second cylinder 31B at the angle A26.

Thus, in the present embodiment, when the engine 10 is started, the air-fuel mixture is introduced into the first cylinder 31A while the crankshaft 13 is reversely rotated by the starter / generator 14. Thereafter, in the first cylinder 31A, the air-fuel mixture in the combustion chamber 31a is ignited with the piston 11 approaching the compression top dead center (the crank angle approaches the angle A1), and the rotation direction of the crankshaft 13 Is switched in the positive direction. In this case, the torque in the positive direction of the crankshaft 13 is increased by the combustion energy. Thereby, the crank angle can easily exceed the angles A1 and A4 corresponding to the compression top dead centers of the first and

second cylinders

31A and 31B, and the engine 10 is stably started.

In the first cylinder 31A, when the crankshaft 13 rotates in the reverse direction, the intake port 21 may be opened in the same crank angle range as in the normal rotation (range from the angle A12 to the angle A11 in FIG. 7). Or it may not be opened. At the time of reverse rotation of the crankshaft 13, the piston 11 rises in the range from the angle A4 to the angle A3. Therefore, even if the intake port 21 is opened, air and fuel are hardly introduced into the combustion chamber 31a. Therefore, there is almost no influence on the reverse rotation starting operation. Further, when the crankshaft 13 rotates in the reverse direction, the exhaust port 23 may or may not be opened in the same crank angle range (the range from the angle A14 to the angle A13 in FIG. 7) as in the normal rotation. Good. By opening the intake port 21 and the exhaust port 23 in the same crank angle range during forward rotation and reverse rotation of the crankshaft 13, the configuration of the valve drive unit 17 can be simplified.

(3) Crankshaft Rotation Load FIG. 8 is a diagram showing the relationship between the rotation load of the crankshaft 13 and the crank angle. In FIG. 8, the horizontal axis indicates the crank angle, and the vertical axis indicates the rotational load of the crankshaft 13. The rotational load caused by the first cylinder 31A is represented by a solid line, and the rotational load caused by the second cylinder 31B is represented by a one-dot chain line. The sum of the rotational load caused by the first cylinder 31 </ b> A and the rotational load caused by the second cylinder 31 </ b> B acts on the crankshaft 13.

Regarding the first cylinder 31A, the rotational load becomes the largest at the angle A1 corresponding to the compression top dead center. Further, with respect to the second cylinder 31B, the rotational load becomes the largest at an angle A4 corresponding to the compression top dead center.

Further, when the valve drive unit 17 of FIG. 3 is formed of a camshaft, a reaction force applied to the valve drive unit 17 when driving the intake valve 15 and the exhaust valve 16 becomes a rotational load of the valve drive unit 17. Since the valve drive unit 17 is rotated by the crankshaft 13, the rotational load of the valve drive unit 17 becomes the rotational load of the crankshaft 13.

In the example of FIG. 8, with respect to the first cylinder 31A, the rotational load on the crankshaft 13 increases in order to drive the intake valve 15 (FIG. 3) in the range from the angle A3 to the angle A4, and from the angle A2 to the angle A3. In order to drive the exhaust valve 16 (FIG. 3) in this range, the rotational load on the crankshaft 13 increases. Further, with respect to the second cylinder 31B, the rotational load on the crankshaft 13 increases in order to drive the intake valve 15 in the range from the angle A2 to the angle A3, and the exhaust valve 16 is driven in the range from the angle A1 to the angle A2. Therefore, the rotational load on the crankshaft 13 increases.

When the engine 10 is stopped, the rotation of the crankshaft 13 tends to stop when the rotational load is large. Thereby, the rotation of the crankshaft 13 tends to stop mainly when the crank angle approaches the angles A1 and A4 corresponding to the compression top dead center. Further, the rotation of the crankshaft 13 may be stopped by a load for driving the intake valve 15 or the exhaust valve 16.

For example, the rotation of the crankshaft 13 may stop in a state where the crank angle is on the retard side with respect to the angle A33 and on the advance side with respect to the angle A34 in the reverse direction. If the reverse rotation start operation is started from this state, the crank angle does not pass through the angle A33, so that fuel is not injected and the air-fuel mixture is not introduced into the first cylinder 31A. In the reverse rotation starting operation, in order to inject fuel and introduce the air-fuel mixture into the first cylinder 31A, it is necessary to reversely rotate the crankshaft 13 so that the crank angle passes through the range from the angle A33 to the angle A32. There is.

Also, in the reverse rotation starting operation, in order to effectively introduce the air-fuel mixture into the first cylinder 31A, it is preferable that the rotational speed of the crankshaft 13 is increased before the crank angle reaches the angle A31. Furthermore, it is preferable that the rotational speed of the crankshaft 13 is sufficiently increased in order to ensure that the crank angle reaches the angle A34. Therefore, in the reverse direction, it is preferable that the reverse rotation start operation is performed from a state in which the crank angle is sufficiently advanced from the angle A33.

On the other hand, rotation of the crankshaft 13 stops in a state where the crank angle is in the retarded direction with respect to the angle A1 and in the advanced direction with respect to the angle A4 in the reverse direction (for example, the state at the angle A30a in FIGS. 6 and 8). Sometimes. If the reverse rotation start operation is started from this state, a large rotational load is applied to the crankshaft 13 as the crank angle approaches the angle A4 corresponding to the compression top dead center of the second cylinder 31B. Therefore, reverse rotation of the crankshaft 13 is hindered.

Therefore, before the reverse rotation start operation, the crank angle is adjusted to the angle A30 by the forward rotation alignment operation. The angle A30 is sufficiently advanced than the angle A33 in the reverse direction. Therefore, when the reverse rotation of the crankshaft 13 is started from a state where the crank angle is at the angle A30, the crankshaft passes through the range from the angle A33 to the angle A32 and the crank angle reaches the angle A31. The rotational speed of 13 is sufficiently increased. Therefore, the air-fuel mixture is sufficiently introduced into the combustion chamber 31a in the range from the angle A31 to the angle A32, and the crank angle easily reaches the angle A34.

Further, since the angle A30 is on the retard side with respect to the angle A4 in the reverse direction, the reverse rotation of the crankshaft 13 is not hindered during the reverse rotation start operation. Therefore, the air-fuel mixture can be combusted appropriately, and the torque in the positive direction of the crankshaft 13 can be sufficiently increased.

Further, as described above, in the forward rotation alignment operation, when the crank angle needs to exceed the angle A1 corresponding to the compression top dead center of the first cylinder 31A, the decompression mechanism DE causes the first cylinder 31A. The crankshaft 13 is rotated forward while the internal pressure is reduced. Thereby, the normal rotation of the crankshaft 13 is not hindered, and the crank angle can be easily adjusted to the angle A30.

The decompression mechanism DE may be configured to be switched between an operating state and a non-operating state by a centrifugal governor. For example, when the rotational speed of the crankshaft 13 is lower than a certain threshold value, the decompression mechanism DE is activated, and the exhaust valve 16 is lifted in the first compression range. Further, when the rotational speed of the crankshaft 13 exceeds a certain threshold value, the decompression mechanism DE is deactivated and the exhaust valve 16 is not lifted. In this case, with a simple configuration, the pressure in the first cylinder 31A can be reduced during the forward rotation alignment operation.

Further, it is preferable that the decompression mechanism DE is configured so as not to lower the pressure in the first cylinder 31A in a range (first expansion range) on the advance side from the angle A1 in the reverse direction. In this case, during the above-described reverse rotation starting operation, when the crank angle approaches the angle A1, the pressure in the first cylinder 31A is not reduced by the decompression mechanism DE. Thereby, a decrease in energy obtained by combustion of the air-fuel mixture is prevented.

Further, the decompression mechanism DE reduces the pressure in the first cylinder 31A within a certain angular range only when the rotational speed of the crankshaft 13 is lower than a certain threshold value and only when the crankshaft 13 is rotating forward. It may be configured as follows. Also in this case, the pressure in the first cylinder 31A is prevented from being lowered during the reverse rotation starting operation.

It should be noted that when the engine 10 is stopped, the rotation of the crankshaft 13 may stop in a state where the crank angle is at or near the reverse rotation start range. In that case, the forward rotation alignment operation may not be performed.

(4) Engine start process ECU6 performs an engine start process based on the control program previously memorize | stored in memory. 9 and 10 are flowcharts for explaining an example of the engine start process. The engine start process is performed when the main switch 40 or the starter switch 41 in FIG. 3 is turned on or when the engine 10 shifts to the idle stop state.

As shown in FIG. 9, first, the ECU 6 determines whether or not the current crank angle is stored in the memory (step S11). For example, immediately after the main switch 40 is turned on, the current crank angle is not stored. In the idle stop state, the current crank angle is stored.

If the current crank angle is not stored, the ECU 6 controls the starter / generator 14 so that the crankshaft 13 rotates forward (step S12). In this case, the starter / generator is based on the detection signal from the current sensor 44 (FIG. 3) so that the crank angle does not reach the angle A4 (FIG. 8) corresponding to the compression top dead center of the second cylinder 31B. 14 torque is adjusted.

In step S12, when the crank angle passes through the angle A1 corresponding to the compression top dead center of the first cylinder 31A, the decompression mechanism DE is prevented so that the forward rotation of the crankshaft 13 is not hindered as described above. As a result, the pressure in the first cylinder 31A is reduced.

Next, the ECU 6 determines whether or not a specified time has elapsed since the rotation of the crankshaft 13 was started in step S12 (step S13). If the specified time has not elapsed, the ECU 6 controls the starter / generator 14 so that the rotation of the crankshaft 13 in the positive direction is continued (step S12). When the specified time elapses, the ECU 6 controls the starter / generator 14 so that the rotation of the crankshaft 13 is stopped (step S14). As a result, the crank angle is adjusted to the reverse rotation start range (angle A30 in FIG. 6).

In step S12, the crank angle may be detected when the crankshaft 13 is rotated forward, and the crank angle may be adjusted to the reverse rotation start range based on the detected value.

On the other hand, if the current crank angle is stored in step S11, the ECU 6 determines whether or not the current crank angle is in the reverse rotation start range (step S15). When the current crank angle is not in the reverse rotation start range, the ECU 6 controls the starter / generator 14 so that the crankshaft 13 is rotated forward (step S16). In this case, the starter / generator is based on the detection signal from the current sensor 44 (FIG. 3) so that the crank angle does not reach the angle A4 (FIG. 8) corresponding to the compression top dead center of the second cylinder 31B. 14 torque is adjusted.

As in step S12 above, in step S16, when the crank angle passes through the angle A1 corresponding to the compression top dead center of the first cylinder 31A, the forward rotation of the crankshaft 13 is not hindered. The pressure in the first cylinder 31A is reduced by the decompression mechanism DE.

Next, the ECU 6 determines whether or not the current crank angle has reached the reverse rotation start range based on detection signals from the intake pressure sensor 42 and the crank angle sensor 43 (step S17). If the current crank angle has not reached the reverse rotation start range, the ECU 6 controls the starter / generator 14 so that the forward rotation of the crankshaft 13 is continued (step S16). When the current crank angle reaches the reverse rotation start range, the ECU 6 controls the starter / generator 14 so that the rotation of the crankshaft 13 is stopped (step S14). Thereby, the crank angle is adjusted to the reverse rotation start range.

In the processes in steps S16 and S17, the crank angle is adjusted with higher accuracy than in the processes in steps S12 and S13, and the power consumption by the starter / generator 14 is suppressed.

After the crankshaft 13 is rotated forward, the crank angle is adjusted to the reverse rotation start range, and then the process of step S21 in FIG. 10 is performed. In step S15, when the current crank angle is in the reverse rotation start range, the process of step S21 in FIG. 10 is performed as it is.

As shown in FIG. 10, in step S21, the ECU 6 determines whether or not a predetermined starting condition for the engine 10 is satisfied. The starting condition of the engine 10 is, for example, that the starter switch 41 (FIG. 3) is turned on or that the idle stop cancellation condition is satisfied.

When the start condition of the engine 10 is satisfied, the ECU 6 controls the starter / generator 14 so that the crankshaft 13 is rotated in the reverse direction (step S22). Next, the ECU 6 determines whether or not the current crank angle has reached the angle A33 in FIG. 7 based on detection signals from the intake pressure sensor 42 (FIG. 3) and the crank angle sensor 43 (FIG. 3). (Step S23). The ECU 6 repeats the process of step S23 until the current crank angle reaches the angle A33.

When the current crank angle reaches the angle A33, the ECU 6 controls the injector 19 corresponding to the first cylinder 31A so that fuel is injected into the intake passage 22 (FIG. 3) (step S24). In this case, when the crank angle reaches the angle A33, a pulse signal is given from the crank angle sensor 43 to the ECU 6, and the ECU 6 may control the injector 19 so that fuel is injected in response to the pulse signal. .

Next, the ECU 6 determines whether or not the motor current has reached a predetermined threshold value based on the detection signal from the current sensor 44 (step S25). In this case, the motor current increases as the crank angle approaches the angle A1 in FIG. In this example, when the crank angle reaches the angle A34 in FIG. 7, the motor current reaches the threshold value. If the motor current has not reached the threshold value, the ECU 6 repeats the process of step S25.

When the motor current reaches a predetermined threshold value, the ECU 6 controls the starter / generator 14 so that the reverse rotation of the crankshaft 13 is stopped (step S26), and corresponds to the first cylinder 31A. The air-fuel mixture in the combustion chamber 31a is ignited by the spark plug 18 that performs (step S27). Further, the ECU 6 controls the starter / generator 14 so that the crankshaft 13 is rotated forward (step S28). Thereby, ECU6 complete | finishes an engine starting process, and the engine 10 transfers to normal driving | operation. Note that the driving of the crankshaft 13 by the starter / generator 14 is stopped after a predetermined time elapses from the processing of step S28, for example.

In this example, it is determined whether or not the crank angle has reached the starting ignition range (angle A34) based on the motor current, but the present invention is not limited to this. For example, it may be determined whether or not the crank angle has reached the start ignition range based on the current crank angle detected by the intake pressure sensor 42 (FIG. 3) and the crank angle sensor 43 (FIG. 3).

Further, after the crankshaft 13 has started to reversely rotate in step S22, if a predetermined time has passed without the crank angle reaching the starting ignition range, an abnormality of the engine unit EU has occurred. The reverse rotation starting operation may be stopped. The abnormality of the engine unit EU includes a malfunction of the starter / generator 14 or a malfunction of the valve drive unit 17.

(5) Effect In the engine system 200 according to the present embodiment, the air-fuel mixture is guided into the first cylinder 31A while the crankshaft 13 is rotated in reverse by the reverse rotation start operation, and the piston 11 is compressed top dead center. The air-fuel mixture is ignited while approaching The crankshaft 13 is driven in the positive direction by the combustion energy of the air-fuel mixture. In this case, since the time from when the air-fuel mixture is introduced into the first cylinder 31A until the air-fuel mixture is ignited is short, the air-fuel ratio at the time of ignition can be adjusted appropriately.

Also, before the reverse rotation start operation, the crank angle is adjusted to the reverse rotation start range (angle A30) by the forward rotation alignment operation. Thereby, the air-fuel mixture can be appropriately introduced into the first cylinder 31A in the reverse rotation start operation, and the crank angle can easily reach the start ignition range (angle A34).

Thus, the air-fuel mixture can be appropriately combusted in the first cylinder 31A, and the positive torque of the crankshaft 13 can be sufficiently increased. As a result, the engine 10 can be started appropriately.

In the forward rotation alignment operation, when the crank angle is within the alignment pressure reduction range (range from angle AD1 to angle AD2), the pressure in the first cylinder 31A is reduced by the decompression mechanism DE. In this case, even if the crank angle approaches the angle A1 corresponding to the compression top dead center of the first cylinder 31A, an increase in pressure in the first cylinder 31A is suppressed. Therefore, an increase in the rotational resistance of the crankshaft 13 is suppressed, and the normal rotation of the crankshaft 13 is not hindered. Thereby, the crank angle can be easily adjusted to the reverse rotation start range.

In the present embodiment, in the reverse rotation start operation, the crank angle does not pass through the angles A1 and A4 corresponding to the compression top dead centers of the first and

second cylinders

31A and 31B. The crank angle can easily reach the starting ignition range (angle A34) without reducing the pressure in the

cylinders

31A and 31B. Accordingly, the forward rotation alignment operation and the reverse rotation start operation can be appropriately performed with a simple configuration.

(6) Another example of reverse rotation start operation When the engine 10 is stopped with the crank angle being in the first compression range, the reverse rotation start operation is performed without performing the normal rotation alignment operation. It may be broken. 11 and 12 are diagrams for explaining another example of the reverse rotation starting operation. In the example of FIGS. 11 and 12, the reverse rotation starting operation is performed from the state where the crank angle is at the angle A70 in the first compression range. As indicated by arrows P71 to P74 in FIG. 12, in the second cylinder 31B, when the crankshaft 13 rotates in the reverse direction, the piston 11 rises in the range from the angle A1 to the angle A4, and from the angle A4 to the angle A3. The piston 11 is lowered in the range of A, the piston 11 is raised in the range from the angle A3 to the angle A2, and the piston 11 is lowered in the range from the angle A2 to the angle A1.

In this case, the crank angle needs to exceed the angle A4 corresponding to the compression top dead center of the second cylinder 31B. Therefore, the crankshaft 13 is rotated in reverse while the pressure in the second cylinder 31B is reduced by the decompression mechanism DE. In the example of FIG. 12, the pressure in the second cylinder 31B is reduced by the decompression mechanism DE in the range from the angle AD7 to the angle AD8. The range from the angle AD7 to the angle AD8 is an example of the starting decompression range and is in the second expansion range. Thereby, even if a crank angle approaches angle A4, the raise of the pressure in the 2nd cylinder 31B is suppressed. Therefore, the reverse rotation of the crankshaft 13 is not hindered.

The angle A70 is sufficiently advanced from the angle A31 in FIG. 11 in the reverse direction. Therefore, when the reverse rotation of the crankshaft 13 is started from the state where the crank angle is at the angle A70, the crank angle passes through the range from the angle A33 to the angle A32 in FIG. 11 and the crank angle reaches the angle A31. At that time, the rotational speed of the crankshaft 13 is sufficiently increased. Therefore, the air-fuel mixture is sufficiently introduced into the combustion chamber 31a in the range from the angle A31 to the angle A32, and the crank angle easily reaches the angle A34.

As described above, also in the present embodiment, when the engine 10 is started, the air-fuel mixture is introduced into the first cylinder 31A while the crankshaft 13 is reversely rotated by the starter / generator 14. Thereafter, in the first cylinder 31A, the air-fuel mixture in the combustion chamber 31a is ignited with the piston 11 approaching the compression top dead center, and the rotation direction of the crankshaft 13 is switched to the positive direction. In this case, the torque in the positive direction of the crankshaft 13 is increased by the combustion energy. Thereby, the crank angle can easily exceed the angles A1 and A4 corresponding to the compression top dead centers of the first and

second cylinders

31A and 31B, and the engine 10 is started appropriately.

11 and 12, when the engine 10 is stopped in a state where the crank angle is in the first compression range (second expansion range), the engine 10 is not started (reverse rotation start). Before the operation), the crank angle may be adjusted to the angle A30 in FIG. 6 by rotating the crankshaft 13 in the reverse direction. In this case, the crank angle exceeds the angle A4 corresponding to the compression top dead center of the second cylinder 31B because the decompression mechanism DE reduces the pressure in the second cylinder 31B while the crankshaft 13 is rotated in the reverse direction. . Thereby, the crank angle can be adjusted to the angle A30. Therefore, similarly to the example of FIG. 6, the reverse rotation starting operation can be started from the state where the crank angle is at the angle A30.

[C] Engine system (second embodiment)
The engine system according to the second embodiment of the present invention will be described while referring to differences from the first embodiment. FIG. 13 is a schematic side view for explaining the configuration of the engine system 200 according to the second embodiment. In the engine system 200 of FIG. 13, the crank angle when the piston 11 reaches the compression top dead center in the first cylinder 31A, and the crank angle when the piston 11 reaches the compression top dead center in the second cylinder 31B. The difference is 360 degrees. Therefore, in the vertical direction (reciprocating direction of the piston 11), the position of the piston 11 in the first cylinder 31A and the position of the piston 11 in the second cylinder 31B coincide.

(1) Normal Operation FIG. 14 is a diagram for explaining the normal operation of the engine 10. FIG. 14 (a) shows the relationship between the operation in the first cylinder 31A and the crank angle, and FIG. 14 (b) shows the relationship between the operation in the second cylinder 31B and the crank angle. It is.

As shown in FIG. 14A, the relationship between the operation of the first cylinder 31A and the crank angle during the normal operation is the same as the example of FIG. 4 of the first embodiment. As shown in FIG. 14B, in the second cylinder 31B, the piston 11 is located at the exhaust top dead center when the crank angle is the angle A1, and the piston 11 is moved when the crank angle is the angle A2. When the crank angle is an angle A3, the piston 11 is positioned at the compression top dead center when the crank angle is the angle A3, and when the crank angle is the angle A4, the piston 11 is positioned at the expansion bottom dead center.

During normal operation, as indicated by arrows P41 to P44, the piston 11 (FIG. 2) is lowered in the range from the angle A1 to the angle A2, and the piston 11 is raised in the range from the angle A2 to the angle A3. To the angle A4, the piston 11 descends, and the piston 11 rises in the range from the angle A4 to the angle A1.

The range from angle A1 to angle A2 corresponds to the second intake range, the range from angle A2 to angle A3 corresponds to the second compression range, and the range from angle A3 to angle A4 is the second expansion range. The range from the angle A4 to the angle A1 corresponds to the second exhaust range.

The intake port 21 (FIG. 3) is opened by the intake valve 15 (FIG. 3) in the range from the angle A41 to the angle A42, and the exhaust port 23 (FIG. 3) is opened by the exhaust valve 16 (FIG. 3) in the range from the angle A43 to the angle A44. 3) is opened. The angle A41 is in the second exhaust range and is positioned at a certain angle advance side from the angle A1 in the positive direction, and the angle A42 is in the second compression range and is a certain angle later than the angle A2 in the positive direction Located on the corner side. The angle A43 is in the second expansion range and is positioned at a constant angle advance side from the angle A4 in the positive direction, and the angle A44 is in the second intake range and is a constant angle delay from the angle A1 in the positive direction. Located on the corner side.

The fuel is injected into the intake passage 22 (FIG. 3) by the injector 19 (FIG. 3) at an angle A45, and ignited by the spark plug 18 (FIG. 3) at an angle A46. The angle A45 is in the second exhaust range and is located on the more advanced side than the angle A41 in the positive direction. The angle A46 is in the second compression range and is positioned at a constant angle advance side from the angle A3 in the positive direction.

In this case, the air-fuel mixture containing the fuel injected at the angle A45 is introduced into the combustion chamber 31a through the intake port 21 in the range from the angle A41 to A42. The air-fuel mixture is compressed in the combustion chamber 31a and ignited by the spark plug 18 at an angle A46. As a result, the air-fuel mixture is combusted in the combustion chamber 31a, the piston 11 is driven by the combustion energy, and the crankshaft 13 is driven in the forward direction. Thereafter, the burned gas is discharged from the combustion chamber 31a through the exhaust port 23 in the range from the angle A43 to the angle A44.

As described above, in the second embodiment, the crank angle when the piston 11 reaches the compression top dead center in the first cylinder 31A and the piston angle when the piston 11 reaches the compression top dead center in the second cylinder 31B. The difference from the crank angle is 360 degrees. Therefore, during normal operation, the air-fuel mixture is combusted at equal intervals in the first and

second cylinders

31A and 31B. Specifically, the ignition operation is performed in the second cylinder 31B after the crankshaft 13 has rotated 360 degrees after the ignition operation has been performed in the first cylinder 31A, and again after the crankshaft 13 has rotated 360 degrees. An ignition operation is performed in the first cylinder 31A.

(2) Forward rotation alignment operation and reverse rotation start operation FIGS. 15 and 16 are diagrams for explaining the forward rotation alignment operation of the engine unit EU. 17 and 18 are diagrams for explaining the reverse rotation starting operation of the engine unit EU. 15 and 17 show the relationship between the operation in the first cylinder 31A and the crank angle. 16 and 18 show the relationship between the operation in the second cylinder 31B and the crank angle.

As shown in FIG. 15, in the forward rotation alignment operation, the crankshaft 13 is rotated forward by the starter / generator 14 (FIG. 3), so that the crank angle is adjusted to the angle A50. The angle A50 is an example of the reverse rotation start range and is in the first compression range. The reverse rotation start range may be a specific angle range instead of a specific angle. The reverse rotation start range may be in the first intake range, or may be a certain angle range from an angle in the first intake range to an angle in the first compression range.

At the start of the forward rotation alignment operation, the crank angle is retarded from the angle A1 corresponding to the compression top dead center of the first cylinder 31A in the positive direction and corresponds to the compression top dead center of the second cylinder 31B. In some cases, the angle is on the more advanced side than the angle A3 (for example, the angle A50a in FIG. 15). In this case, in the forward rotation alignment operation, the crank angle needs to exceed an angle A3 corresponding to the compression top dead center of the second cylinder 31B.

Therefore, in the second embodiment, the decompression mechanism DE of FIG. 3 is configured to reduce the pressure in the second cylinder 31B. The decompression mechanism DE reduces the pressure in the second cylinder 31B by, for example, lifting the exhaust valve 16 corresponding to the second cylinder 31B.

When the crank angle needs to exceed the angle A3 in the forward rotation alignment operation, the crankshaft 13 is rotated forward while the pressure in the second cylinder 31B is reduced by the decompression mechanism DE. In the example of FIG. 16, the pressure in the second cylinder 31B is reduced by the decompression mechanism DE in the range from the angle AD3 to the angle AD4 while the crankshaft 13 is rotated forward. The range from the angle AD3 to AD4 is an example of the alignment decompression range and is in the second compression range.

Thereby, even if the crank angle approaches the angle A3, an increase in pressure in the second cylinder 31B is suppressed. Therefore, the forward rotation of the crankshaft 13 is not hindered, and the crank angle can be easily adjusted to the angle A50.

17 and 18, in the reverse rotation start operation, the crankshaft 13 is reversely rotated from a state where the crank angle is in the reverse rotation start range (angle A50). As indicated by arrows P51 to P54 in FIG. 18, in the second cylinder 31B, the piston 11 rises in the range from the angle A4 to the angle A3, and the piston 11 falls in the range from the angle A3 to the angle A2. The piston 11 is raised in the range from the angle A2 to the angle A1, and the piston 11 is lowered in the range from the angle A1 to the angle A4.

In the first cylinder 31A, the intake port 21 (FIG. 3) is opened by the intake valve 15 (FIG. 3) in the range from the angle A31 to the angle A32 in FIG. Fuel is injected into the intake passage 22 (FIG. 3) by the injector 19 (FIG. 3). Further, at the angle A34, the spark plug 18 is ignited and the rotation direction of the crankshaft 13 is switched from the reverse direction to the forward direction. Thereby, the air-fuel mixture is combusted in the first cylinder 31A, and the crankshaft 13 is driven in the positive direction by the combustion energy of the air-fuel mixture.

In the reverse rotation starting operation, the crank angle needs to exceed the angle A3 corresponding to the compression top dead center of the second cylinder 31B. Therefore, the crankshaft 13 is rotated in reverse while the pressure in the second cylinder 31B is reduced by the decompression mechanism DE. In the example of FIG. 18, the pressure in the second cylinder 31B is reduced by the decompression mechanism DE in the range from the angle AD5 to the angle AD6 while the crankshaft 13 is rotated in the reverse direction. The range from the angle AD5 to the angle AD6 is an example of the starting decompression range, and is in the second expansion range. Thereby, even if a crank angle approaches angle A3, the raise of the pressure in the 2nd cylinder 31B is suppressed. Therefore, the reverse rotation of the crankshaft 13 is not hindered.

The angle A50 is sufficiently advanced from the angle A31 (FIG. 17) in the reverse direction. Therefore, when the reverse rotation of the crankshaft 13 is started from the state where the crank angle is at the angle A50, the crank angle passes through the range from the angle A33 to the angle A32 and the crank angle reaches the angle A31. The rotational speed of the shaft 13 is sufficiently increased. Therefore, the air-fuel mixture is sufficiently introduced into the combustion chamber 31a in the range from the angle A31 to the angle A32, and the crank angle easily reaches the angle A34.

As shown in FIG. 18, in the reverse rotation starting operation, when the crank angle reaches the angle A47, fuel is injected into the intake passage 22 by the injector 19 (FIG. 3) corresponding to the second cylinder 31B. . The angle A47 is in the second intake range and is positioned on the more advanced side than the angle A34 in the reverse direction.

At angle A34, the rotation direction of the crankshaft 13 is switched from the reverse direction to the forward direction. At this time, the second cylinder 31B is in the intake stroke. Therefore, the air-fuel mixture containing the fuel injected at the angle A47 is introduced into the second cylinder 31B immediately after the rotation direction of the crankshaft 13 is switched to the positive direction at the angle A34. Thereby, the air-fuel mixture can be burned in the second cylinder 31B in the first expansion stroke after the rotation direction of the crankshaft 13 is switched to the positive direction. Therefore, the engine 10 can quickly shift to the normal operation of FIG.

As described above, also in the present embodiment, when the engine 10 is started, the air-fuel mixture is introduced into the first cylinder 31A while the crankshaft 13 is reversely rotated by the starter / generator 14. Thereafter, in the first cylinder 31A, the air-fuel mixture in the combustion chamber 31a is ignited with the piston 11 approaching the compression top dead center, and the rotation direction of the crankshaft 13 is switched to the positive direction. In this case, the torque in the positive direction of the crankshaft 13 is increased by the combustion energy. Thereby, the crank angle can easily exceed the angles A1 and A3 corresponding to the compression top dead centers of the first and

second cylinders

31A and 31B, and the engine 10 is stably started.

(3) Crankshaft Rotation Load FIG. 19 is a diagram showing the relationship between the rotation load of the crankshaft 13 and the crank angle. The difference between the example of FIG. 19 and the example of FIG. 8 will be described. In the example of FIG. 19, with respect to the second cylinder 31B, the rotational load becomes the largest at an angle A3 corresponding to the compression top dead center. Further, when the valve drive unit 17 of FIG. 3 is formed of a camshaft, the rotational load on the crankshaft 13 is increased in order to drive the intake valve 15 in the range from the angle A1 to the angle A2 with respect to the second cylinder 31B. Since the exhaust valve 16 is driven in the range from the angle A4 to the angle A1, the rotational load on the crankshaft 13 increases.

When the engine 10 is stopped, the rotation of the crankshaft 13 tends to stop when the rotational load is large. Thereby, the rotation of the crankshaft 13 tends to stop mainly when the crank angle approaches the angles A1 and A3 corresponding to the compression top dead center.

Similarly to the first embodiment, it is preferable that the reverse rotation start operation is performed from a state where the crank angle is sufficiently advanced from the angle A33 in the reverse direction. Therefore, the crank angle is adjusted to the angle A50 by the forward rotation alignment operation before the reverse rotation start operation. The angle A50 is sufficiently advanced than the angle A33 in the reverse direction. Therefore, when the reverse rotation of the crankshaft 13 is started from the state where the crank angle is at the angle A50, the crankshaft passes through the range from the angle A33 to the angle A32 and the crank angle reaches the angle A31. The rotational speed of 13 is sufficiently increased. Therefore, the air-fuel mixture is sufficiently introduced into the combustion chamber 31a in the range from the angle A31 to the angle A32, and the crank angle easily reaches the angle A34.

Further, when the crank angle needs to exceed the angle A3 corresponding to the compression top dead center of the second cylinder 31B in the forward rotation alignment operation, the pressure in the second cylinder 31B is reduced by the decompression mechanism DE. The crankshaft 13 is rotated forward while being rotated. Thereby, the normal rotation of the crankshaft 13 is not hindered, and the crank angle can be easily adjusted to the angle A50.

As in the first embodiment, the decompression mechanism DE may be configured to be switched between an operating state and a non-operating state by a centrifugal governor. For example, when the rotational speed of the crankshaft 13 is lower than a certain threshold value, the decompression mechanism DE is activated, and the exhaust valve 16 is lifted in the second compression range. Further, when the rotational speed of the crankshaft 13 exceeds a certain threshold value, the decompression mechanism DE is deactivated and the exhaust valve 16 is not lifted. In this case, with a simple configuration, the pressure in the second cylinder 31B can be reduced during the forward rotation alignment operation.

(4) Engine start process The engine start process according to the second embodiment will be described while referring to differences from the example of FIGS. 9 and 10 of the first embodiment. FIG. 20 is a flowchart illustrating a part of the engine start process according to the second embodiment.

First, the crank angle is adjusted to the reverse rotation start range by performing the processing of steps S11 to S17 in FIG. In steps S12 and S16 in FIG. 9, when the crank angle passes through the angle A3 corresponding to the compression top dead center of the second cylinder 31B, the decompression mechanism DE is prevented so that the forward rotation of the crankshaft 13 is not hindered. As a result, the pressure in the second cylinder 31B is reduced.

Subsequently, the process of step S21 in FIG. 20 is performed. The example of FIG. 20 is different from the example of FIG. 10 in that the processes of steps S31 and S32 are performed after the process of step S24 and before the process of step S25.

In step S31, the ECU 6 determines whether or not the current crank angle has reached the angle A47 in FIG. 18 based on detection signals from the intake pressure sensor 42 (FIG. 3) and the crank angle sensor 43 (FIG. 3). To do. The ECU 6 repeats the process of step S31 until the current crank angle reaches the angle A47.

When the current crank angle reaches the angle A47, the ECU 6 controls the injector 19 corresponding to the second cylinder 31B so that the fuel is injected into the intake passage 22 (FIG. 3) (step S32). In this case, when the crank angle reaches the angle A47, a pulse signal is given from the crank angle sensor 43 to the ECU 6, and the ECU 6 may control the injector 19 so that fuel is injected in response to the pulse signal. .

Thus, as described above, the air-fuel mixture is introduced into the second cylinder 31B immediately after the rotation direction of the crankshaft 13 is switched to the positive direction at the angle A34. Therefore, the engine 10 can quickly shift to normal operation.

(5) Specific Example of Decompression Mechanism A specific example of the decompression mechanism DE in the second embodiment will be described. FIG. 21 is a schematic diagram illustrating an example of the valve driving unit 17. 21 includes an intake camshaft 171 and an exhaust camshaft 172. Each of the intake camshaft 171 and the exhaust camshaft 172 rotates in conjunction with the crankshaft 13. The intake camshaft 171 includes a plurality of intake cams 173 that drive the intake valves 15 of the first and

second cylinders

31A and 31B, respectively. The exhaust camshaft 172 includes a plurality of exhaust cams 174 that respectively drive the exhaust valves 16 of the first and

second cylinders

31A and 31B. FIG. 21 shows only one intake cam 173 and one exhaust cam 174.

In this example, the exhaust cam 174 is provided with a decompression mechanism DE. FIG. 22 is a perspective view of the decompression mechanism DE. In FIG. 22, a part of the exhaust cam 174 is transparently represented.

The exhaust cam 174 in FIG. 22 drives the exhaust valve 16 (FIG. 21) corresponding to the second cylinder 31B. The exhaust cam 174 of FIG. 22 includes a cam member CA and a decompression mechanism DE. The cam member CA lifts the exhaust valve 16 corresponding to the second cylinder 31B in the range from the angle A43 to A44 in FIG.

The decompression mechanism DE includes a rotating member 61, decompression pins 62 and 63, a connecting member 64, a decompression weight 65, and a stopper pin 66. The rotating member 61 and the decompression pins 62 and 63 are accommodated inside the cam member CA. The rotating member 61 has a substantially cylindrical shape, and is provided to be rotatable with respect to the cam member CA around a straight line parallel to the rotation center line of the exhaust cam 174. Each of the decompression pins 62 and 63 is provided so as to contact the outer peripheral surface of the rotating member 61.

The connecting member 64, the decompression weight 65, and the stopper pin 66 are provided on one surface of the cam member CA. One end of the connecting member 64 is fixed to the rotating member 61. A protruding pin 64 a is provided at the other end of the connecting member 64.

The decompression weight 65 has a substantially U shape. One end of the decompression weight 65 is attached to the cam member CA via the swing shaft 65a. The decompression weight 65 can swing around the swing shaft 65a with respect to the cam member CA. An oblong through hole 65 b is provided at the other end of the decompression weight 65. The protruding pin 64a of the connecting member 64 is inserted into the through hole 65b.

When the decompression weight 65 swings with respect to the cam member CA, the connecting member 64 swings in conjunction with the rotation, and the rotating member 61 rotates with respect to the cam member CA. A stopper pin 66 is provided between the connecting member 64 and the decompression weight 65. The swing range of the connecting member 64 and the decompression weight 65 is limited by the stopper pin 66.

21. The rotational speed of the exhaust camshaft 172 in FIG. 21 depends on the rotational speed of the crankshaft 13. The decompression mechanism DE is switched between an operating state and a non-operating state depending on the rotational speed of the exhaust camshaft 172, that is, the rotational speed of the crankshaft 13. When the rotational speed of the crankshaft 13 is lower than a certain threshold value, the decompression mechanism DE is maintained in an operating state, and when the rotational speed of the crankshaft 13 is equal to or greater than a certain threshold value, the decompression mechanism DE is in an inoperative state. Maintained.

The operation of the decompression mechanism DE will be described. FIG. 23 is a schematic cross-sectional view for explaining the operating state of the decompression mechanism DE. FIG. 24 is a schematic cross-sectional view for explaining the inoperative state of the decompression mechanism DE. 23 and 24, the cross section of the cam member CA is represented by a dot pattern. Further, the decompression weight 65 and the stopper pin 66 are represented by dotted lines.

As shown in FIGS. 23 and 24, the cam member CA is formed with a housing hole CAa for housing the rotating member 61 and housing holes CAb and CAc for housing the decompression pins 62 and 63, respectively. One end of each of the accommodation holes CAb and CAc is opened on the outer peripheral surface of the cam member CA, and the other end thereof is opened on each inner peripheral surface of the accommodation hole CAa. One end of the accommodation hole CAb and one end of the accommodation hole CAc are provided at different positions in the rotation direction of the cam member CA.

A flange-shaped contact portion 62 a is provided at one end of the decompression pin 62, and a flange-shaped contact portion 63 a is provided at one end of the decompression pin 63. An enlarged portion CAB capable of accommodating the contact portion 62a is provided at the other end of the accommodation hole CAb, and an enlarged portion CAC capable of accommodating the contact portion 63a is provided at the other end of the accommodation hole CAc. A spring SP1 is disposed in the enlarged portion CAB, and a spring SP2 is disposed in the enlarged portion CAC. The contact portion 62a of the decompression pin 62 is pressed against the outer peripheral surface of the rotating member 61 by the spring SP1, and the contact portion 63a of the decompression pin 63 is pressed against the outer peripheral surface of the rotating member 61 by the spring SP2.

The outer peripheral surface of the rotating member 61 has

curved surface portions

61a and 61b and

flat surface portions

61c and 61d. The

curved surface portions

61 a and 61 b are respectively included in cylindrical surfaces centering on the rotation center line of the rotating member 61. The flat surface portion 61c is provided so as to connect one side of the curved surface portion 61a and one side of the curved surface portion 61b, and the flat surface portion 61d is provided so as to connect the other side of the curved surface portion 61a and the other side of the curved surface portion 61b. The connecting member 64 is biased in one direction DR1 by a biasing member (not shown).

When the rotational speed of the crankshaft 13 is lower than a certain threshold value, the decompression mechanism DE is maintained in the operating state of FIG. As shown in FIG. 23, in the operating state, the decompression weight 65 abuts against the stopper pin 66 by the urging force acting on the connecting member 64. In this case, the contact portion 62 a of the decompression pin 62 contacts the curved surface portion 61 a of the rotating member 61, and the contact portion 63 a of the decompression pin 63 contacts the curved surface portion 61 b of the rotating member 61. Accordingly, the distal end portion of the decompression pin 62 projects from the outer peripheral surface of the cam member CA, and the distal end portion of the decompression pin 63 projects from the outer peripheral surface of the cam member CA.

The decompression pin 62 lifts the exhaust valve 16 (FIG. 21) corresponding to the second cylinder 31B when the crank angle is in the range from the angle AD3 to the angle AD4 in FIG. Thus, in the forward rotation alignment operation, when the crank angle approaches the angle A3 corresponding to the compression top dead center of the second cylinder 31B, the pressure in the second cylinder 31B can be reduced. Therefore, the crank angle can easily exceed the angle A3.

The decompression pin 63 lifts the exhaust valve 16 (FIG. 21) corresponding to the second cylinder 31B when the crank angle is in the range from the angle AD5 to the angle AD6 in FIG. Thereby, in the reverse rotation starting operation, when the crank angle approaches the angle A3 corresponding to the compression top dead center of the second cylinder 31B, the pressure in the second cylinder 31B can be reduced. Therefore, the crank angle can easily exceed the angle A3.

When the rotational speed of the crankshaft 13 is equal to or higher than a certain threshold value, the decompression mechanism DE is maintained in the inoperative state of FIG. As shown in FIG. 24, in a non-operating state, the decompression weight 65 moves away from the rotation center line of the exhaust cam 174 by centrifugal force. Thereby, the connecting member 64 contacts the stopper pin 66. In this case, the contact portion 62 a of the decompression pin 62 contacts the flat surface portion 61 c of the rotating member 61, and the contact portion 63 a of the decompression pin 63 contacts the flat surface portion 61 d of the rotating member 61. Thereby, the front-end | tip part of the decompression pin 62 is accommodated in the accommodation hole CAa, and the front-end | tip part of the decompression pin 63 is accommodated in the accommodation hole CAb. Therefore, during normal operation, the decompression pins 62 and 63 do not lift the exhaust valve 16 (FIG. 21).

As described above, during the forward rotation alignment operation and the reverse rotation start operation, the decompression mechanism DE is maintained in the operating state, and the exhaust valves 16 corresponding to the second cylinder 31B are within a certain crank angle range by the decompression pins 62 and 63. Is lifted. On the other hand, during normal operation, the decompression mechanism DE is maintained in an inoperative state, and the exhaust valve 16 is not lifted by the decompression pins 62 and 63.

Note that the same configuration as that of the decompression mechanism DE of FIGS. 22 to 24 can be applied to the decompression mechanism DE of the first embodiment. In this case, a decompression mechanism DE is provided in the exhaust cam 174 that drives the exhaust valve 16 corresponding to the first cylinder 31A. Further, instead of the decompression pins 62 and 63, a decompression pin for lifting the exhaust valve 16 in the range of the angle AD1 to the angle AD2 in FIG. 6 is provided.

With such a configuration, the decompression mechanism DE is activated during the forward rotation alignment operation, and when the crank angle approaches the angle A1 corresponding to the compression top dead center of the first cylinder 31A, the decompression mechanism DE The pressure in one cylinder 31A is reduced. Further, during the reverse rotation starting operation, the pressure in the first and

second cylinders

31A and 31B is not reduced by the decompression mechanism DE. During normal operation, the decompression mechanism DE is deactivated, and the decompression mechanism DE does not reduce the pressure in the first and

second cylinders

31A and 31B. Therefore, in the first embodiment, it is possible to appropriately perform the forward rotation start operation and the reverse rotation start operation while simplifying the configuration of the decompression mechanism DE as compared with the second embodiment.

(6) Effect Also in the engine system 200 according to the present embodiment, the engine 10 is started by the reverse rotation starting operation as in the first embodiment. Thereby, the air-fuel ratio at the time of ignition can be adjusted appropriately. Further, when the crank angle is in the starting pressure reduction range (range from the angle AD5 to the angle AD6), the pressure in the second cylinder 31B is reduced by the decompression mechanism DE. In this case, even if the crank angle approaches the angle A3 corresponding to the compression top dead center of the second cylinder 31B, an increase in pressure in the second cylinder 31B is suppressed. Therefore, an increase in the rotational resistance of the crankshaft 13 is suppressed, and the reverse rotation of the crankshaft 13 is not hindered.

Since the pressure in the second cylinder 31B does not hinder the reverse rotation of the crankshaft 13, the introduction of the air-fuel mixture into the first cylinder 31A and the compression of the air-fuel mixture in the first cylinder 31A can be performed appropriately. . Thereby, the air-fuel mixture can be appropriately burned in the first cylinder 31A, and the positive torque of the crankshaft 13 can be sufficiently increased. As a result, the engine 10 can be started appropriately.

Also, before the reverse rotation start operation, the crank angle is adjusted to the reverse rotation start range (angle A50) by the forward rotation alignment operation. Thereby, the air-fuel mixture can be appropriately introduced into the first cylinder 31A in the reverse rotation start operation, and the crank angle can easily reach the start ignition range (angle A34).

In the forward rotation alignment operation, when the crank angle is within the alignment pressure reduction range (range from angle AD3 to angle AD4), the pressure in the second cylinder 31B is reduced by the decompression mechanism DE. Thereby, an increase in the rotational resistance of the crankshaft 13 is suppressed, and the normal rotation of the crankshaft 13 is not hindered. Thereby, the crank angle can be easily adjusted to the reverse rotation start range.

(7) Modification In the first embodiment, the crank angle when the piston 11 reaches the compression top dead center in the first cylinder 31A and the piston 11 reaches the compression top dead center in the second cylinder 31B. Is 180 degrees, and in the second embodiment, the difference is 360 degrees. However, the present invention is not limited to this.

For example, the difference between the crank angle when the piston 11 reaches the compression top dead center in the first cylinder 31A and the crank angle when the piston 11 reaches the compression top dead center in the second cylinder 31B is 270 degrees. Also good. In this case, similarly to the first embodiment, the pressure in the first cylinder 31A may be reduced by the decompression mechanism DE in the forward rotation alignment operation. Alternatively, as in the second embodiment, the pressure in the second cylinder 31B may be reduced by the decompression mechanism DE in the forward rotation alignment operation and the reverse rotation start operation.

[D] Engine system (third embodiment)
A difference of the engine system according to the third embodiment of the present invention from the first embodiment will be described.

(1) Configuration FIG. 25 is a diagram for describing a configuration of an engine unit EU used in the third embodiment. The engine unit EU in FIG. 25 includes an engine 10A instead of the engine 10 in FIG. Engine 10A is a three-cylinder four-cycle engine, and includes first, second, and

third cylinders

31P, 31Q, and 31R. A piston 11 is provided in each of the first, second, and

third cylinders

31P, 31Q, and 31R, and a combustion chamber 31a is provided above the piston 11. Each piston 11 is connected to a crankshaft 13 via a connecting rod 12.

An intake port 21 and an exhaust port 23 are provided in each of the first, second, and

third cylinders

31P, 31Q, and 31R. Each intake port 21 is opened and closed by the intake valve 15, and each exhaust port 23 is opened and closed by the exhaust valve 16. An intake camshaft 171 and an exhaust camshaft 172 are respectively provided in common to the first, second and

third cylinders

31P, 31Q, 31R. The intake camshaft 171 includes a plurality of intake cams 173, and the exhaust camshaft 172 includes a plurality of exhaust cams 174. Each intake cam 173 and each exhaust cam 174 drive the intake valve 15 and the exhaust valve 16, respectively. The spark plug 18 and the injector 19 in FIG. 3 are provided so as to correspond to each of the first, second, and

third cylinders

31P, 31Q, 31R.

A decompression mechanism DEa is provided between the second cylinder 31Q and the third cylinder 31R. The decompression mechanism DEa suppresses an increase in pressure in the second and

third cylinders

31Q and 31R. Details of the decompression mechanism DEa will be described later.

(2) Normal Operation FIGS. 26 to 27 are diagrams for explaining the normal operation of the engine 10A. FIG. 26 shows the relationship between the operation in the first cylinder 31P and the crank angle, FIG. 27 shows the relationship between the operation in the second cylinder 32Q and the crank angle, and FIG. The relationship between the operation in the third cylinder 32R and the crank angle is shown.

As shown in FIG. 26, the relationship between the operation in the first cylinder 31P and the crank angle during normal operation is the relationship between the operation in the first cylinder 31A and the crank angle in the first embodiment. The same. Specifically, as shown in FIG. 26, the piston 11 is located at the compression top dead center when the crank angle is the angle A1, and the piston 11 is located at the expansion bottom dead center when the crank angle is the angle A2. When the crank angle is the angle A3, the piston 11 is located at the exhaust top dead center, and when the crank angle is the angle A4, the piston 11 is located at the intake bottom dead center. The piston 11 (FIG. 25) is lowered in the range from the angle A1 to the angle A2, the piston 11 is raised in the range from the angle A2 to the angle A3, and the piston 11 is lowered in the range from the angle A3 to the angle A4. The piston 11 rises in the range from A4 to the angle A1.

The intake port 21 (FIG. 25) is opened by the intake valve 15 (FIG. 25) in the range from the angle A11 to the angle A12, and the exhaust port 23 (FIG. 25) is opened by the exhaust valve 16 (FIG. 25) in the range from the angle A13 to the angle A14. 25) is opened. Further, fuel is injected into the intake passage 22 (FIG. 3) by the injector 19 (FIG. 3) at an angle A15, and ignited by the spark plug 18 (FIG. 3) at an angle A16.

As shown in FIG. 27, in the second cylinder 31Q, when the crank angle is the angle A101, the piston 11 is positioned at the compression top dead center, and when the crank angle is the angle A102, the piston 11 is expanded and dead. The piston 11 is located at the exhaust top dead center when the crank angle is the angle A103, and the piston 11 is located at the intake bottom dead center when the crank angle is the angle A104. The piston 11 descends in the range from the angle A101 to the angle A102, the piston 11 rises in the range from the angle A102 to the angle A103, the piston 11 descends in the range from the angle A103 to the angle A104, and the angle A104 to the angle A101. The piston 11 rises in the range up to. In the positive direction, the angles A101 to A104 in FIG. 27 are respectively delayed by 240 degrees from the angles A1 to A4 in FIG.

The intake port 21 (FIG. 25) is opened by the intake valve 15 (FIG. 25) in the range from the angle A111 to the angle A112, and the exhaust port 23 (FIG. 25) is opened by the exhaust valve 16 (FIG. 25) in the range from the angle A113 to the angle A114. 25) is opened. Further, fuel is injected into the intake passage 22 (FIG. 3) by the injector 19 (FIG. 3) at an angle A115, and ignited by the spark plug 18 (FIG. 3) at an angle A116.

As shown in FIG. 28, in the third cylinder 31R, when the crank angle is the angle A201, the piston 11 is positioned at the compression top dead center, and when the crank angle is the angle A202, the piston 11 is expanded and dead. The piston 11 is located at the exhaust top dead center when the crank angle is the angle A203, and the piston 11 is located at the intake bottom dead center when the crank angle is the angle A204. The piston 11 is lowered in the range from the angle A201 to the angle A202, the piston 11 is raised in the range from the angle A202 to the angle A203, the piston 11 is lowered in the range from the angle A203 to the angle A204, and from the angle A204 to the angle A201. The piston 11 rises in the range up to. In the positive direction, the angles A201 to A204 in FIG. 28 are respectively delayed by 240 degrees from the angles A101 to A104 in FIG.

The intake port 21 (FIG. 25) is opened by the intake valve 15 (FIG. 25) in the range from the angle A211 to the angle A212, and the exhaust port 23 (FIG. 25) is opened by the exhaust valve 16 (FIG. 25) in the range from the angle A213 to the angle A214. 25) is opened. Further, fuel is injected into the intake passage 22 (FIG. 3) by the injector 19 (FIG. 3) at the angle A215, and ignited by the spark plug 18 (FIG. 3) at the angle A216. The angles A211 to A216 in FIG. 27 are different from the angles A11 to A16 in FIG. 26 by 480 degrees, respectively.

FIG. 29 is a diagram showing the relationship between the rotational load of the crankshaft 13 and the crank angle. In FIG. 29, the horizontal axis indicates the crank angle, and the vertical axis indicates the rotational load of the crankshaft 13. FIG. 29A shows the rotational load caused by the first cylinder 31P, FIG. 29B shows the rotational load caused by the second cylinder 31Q, and FIG. Indicates the rotational load caused by the third cylinder 31R. FIG. 29 (d) shows the total rotational load caused by the first, second, and

third cylinders

31P, 31Q, 31R.

As shown in FIGS. 29 (a) to 29 (c), the first, second, and

third cylinders

31P, 31Q, and 31R are rotated at angles A1, A101, and A201 corresponding to the compression top dead centers, respectively. Is the largest. As described above, in the positive direction, the angle A101 differs from the angle A1 by 240 degrees, and the angle A201 differs from the angle A101 by 240 degrees. Thereby, as shown in FIG. 29 (d), the rotational load of the crankshaft 13 increases every time the crank angle changes by 240 degrees.

As described above, when the engine 10 is stopped, the rotation of the crankshaft 13 is likely to stop when the rotational load is large. Therefore, in this example, when the crank angle approaches the angle A1, when the crank angle approaches the angle A101, or when the crank angle approaches the angle A201, the rotation of the crankshaft 13 tends to stop.

(3) Forward rotation alignment operation and reverse rotation start operation FIG. 30 is a diagram for explaining the forward rotation alignment operation of the engine unit EU, and FIG. 31 illustrates the reverse rotation start operation of the engine unit EU. FIG. 30 and 31 show the relationship between the operation and the crank angle in the first cylinder 31P.

In the forward rotation starting operation, as shown in FIG. 30, the crankshaft 13 is rotated forward to adjust the crank angle to an angle A300. Angle A300 is an example of the reverse rotation start range. The angle A300 is positioned more retarded than the angle A4 and more advanced than the angle A1 in the positive direction. When the engine 10 is stopped with the crank angle being close to the angle A300, the forward rotation starting operation may not be performed.

In the reverse rotation start operation, as shown in FIG. 31, the crankshaft 13 is reversely rotated from a state where the crank angle is in the reverse rotation start range (angle A300). In the first cylinder 31P, as in the first embodiment, the intake port 21 (FIG. 25) is opened by the intake valve 15 (FIG. 25) in the range from the angle A31 to the angle A32, and the injector at the angle A33. 19 (FIG. 3) injects fuel into the intake passage 22 (FIG. 3). Further, at the angle A34, the spark plug 18 is ignited and the rotation direction of the crankshaft 13 is switched from the reverse direction to the forward direction. Thereby, the air-fuel mixture is combusted in the first cylinder 31A, and the crankshaft 13 is driven in the positive direction by the combustion energy of the air-fuel mixture.

If the crank angle is between the angle A101 and the angle A201 in FIG. 29 when the engine 10 is stopped, the crank angle exceeds the angle A201 corresponding to the compression top dead center of the third cylinder 31R during the forward rotation alignment operation. There is a need. If the crank angle is between the angle A1 and the angle A101 in FIG. 29 when the engine 10 is stopped, the crank angle corresponds to the compression top dead center of the second cylinder 31Q during the forward rotation alignment operation. It is necessary to exceed both the angle A201 corresponding to the compression top dead center of the third cylinder 31R. Further, during the reverse rotation start operation, the crank angle needs to exceed both the angle A201 corresponding to the compression top dead center of the third cylinder 31R and the angle A101 corresponding to the compression top dead center of the second cylinder 31Q. Therefore, during the forward rotation alignment operation and the reverse rotation start operation, the pressure in the second and

third cylinders

31Q and 31R is reduced by the decompression mechanism DEa (FIG. 25). FIG. 32 is a diagram illustrating a specific example of the decompression mechanism DEa.

32 includes a communication path 210,

auxiliary valves

212a and 212b, valve springs 213a and 213b, and an auxiliary valve drive unit 220. The decompression mechanism DEa shown in FIG. The communication path 210 is provided so as to communicate the combustion chamber 31a of the second cylinder 31Q with the combustion chamber 31a of the third cylinder 31R. The second cylinder 31Q is provided with an opening 211a at one end of the communication passage 210, and an auxiliary valve 212a is disposed so as to open and close the opening 211a. The third cylinder 31R is provided with an opening 211b at the other end of the communication path 210, and an auxiliary valve 212b is disposed so as to open and close the opening 211b.

The auxiliary valve 212a is urged in a direction to close the opening 211a by a valve spring 213a. The auxiliary valve 212b is biased in a direction to close the opening 211b by a valve spring 213b. The

auxiliary valves

212a and 212b are connected to each other by a connecting member 215. The auxiliary valve drive unit 220 is a solenoid actuator, for example, and switches the communication path 210 between a communication state and a closed state by driving the

auxiliary valves

212a and 212b integrally. The communication state means a state in which the

openings

211a and 211b are opened by the

auxiliary valves

212a and 212b, and the closed state means a state in which the

openings

211a and 211b are respectively closed by the

auxiliary valves

212a and 212b. In the present embodiment, the communication path 210 is maintained in the communication state by the auxiliary valve drive unit 220 during the forward rotation alignment operation and the reverse rotation start operation.

A change in pressure in the second and

third cylinders

31Q and 31R during the forward rotation alignment operation will be described. FIG. 33 is a diagram for explaining the operation of the second and

third cylinders

31Q and 31P when the crankshaft 13 is rotating forward. FIG. 34 is a schematic diagram for explaining the flow of gas during the forward rotation alignment operation. In FIG. 33, the horizontal axis represents the crank angle. FIG. 33A shows the opening / closing timing of the intake port 21 and the exhaust port 23 and the moving direction of the piston 11 in the second cylinder 31Q, and FIG. 33B shows the third cylinder 31R. The opening / closing timing of the intake port 21 and the exhaust port 23 and the moving direction of the piston 11 are shown.

As shown in FIG. 33 (a), in the second cylinder 31Q, when the crank angle is in the range from the angle A112 to the angle A101, the piston 21 is in a state where both the intake port 21 and the exhaust port 23 are closed. 11 goes up. Therefore, when the communication path 210 is closed, the pressure in the second cylinder 31Q increases. On the other hand, as shown in FIG. 33B, in the third cylinder 31R, when the crank angle is in the range from the angle A112 to the angle A101, at least one of the intake port 21 and the exhaust port 23 is opened. Yes. In this case, if the communication path 210 is in a communication state, the gas in the second cylinder 31Q flows to the third cylinder 31R through the communication path 210 in FIG. 32, and thus the pressure in the second cylinder 31Q increases. Is suppressed.

For example, when the crank angle is in the range from the angle A214 to the angle A101, the piston 11 descends in the third cylinder 31R with the intake port 21 opened. In this case, as shown in FIG. 34A, the gas in the second cylinder 31Q passes through the communication path 210 while the gas flows into the third cylinder 31R through the intake port 21 of the third cylinder 31R. It flows to the third cylinder 31R. Therefore, gas is not compressed in the second cylinder 31Q, and an increase in pressure in the second cylinder 31Q is suppressed.

Further, as shown in FIG. 33 (b), in the third cylinder 31R, when the crank angle is in the range from the angle A212 to the angle A201, both the intake port 21 and the exhaust port 23 are closed. As a result, the piston 11 rises. Therefore, when the communication path 210 is closed, the pressure in the third cylinder 31R increases. On the other hand, as shown in FIG. 33A, in the second cylinder 31Q, when the crank angle is in the range from the angle A212 to the angle A113, both the intake port 21 and the exhaust port 23 are closed. Then, the piston 11 descends. In this case, when the communication path 210 is in the communication state, the gas in the third cylinder 31R flows to the second cylinder 31Q through the communication path 210 as shown in FIG. Thereby, the gas is not compressed in the third cylinder 31R, and the increase in the pressure in the third cylinder 31R is suppressed.

Further, as shown in FIG. 33 (a), when the crank angle is in the range from the angle A113 to the angle A201, the exhaust port 23 of the second cylinder 31Q is opened. Therefore, when the communication path 210 is in the communication state, the gas in the third cylinder 31R flows to the second cylinder 31Q through the communication path 210, thereby suppressing an increase in pressure in the third cylinder 31R. .

For example, when the crank angle is in the range from the angle A102 to the angle A201, the piston 11 rises in the second cylinder 31Q with the exhaust port 23 being opened. In this case, as shown in FIG. 34C, the gas in the third cylinder 31R flows to the second cylinder 31Q through the communication path 210 and the gas in the second cylinder 31Q flows out through the exhaust port 23. . Therefore, gas is not compressed in the third cylinder 31R, and an increase in pressure in the third cylinder 31R is suppressed.

A change in pressure in the second and

third cylinders

31Q and 31R during the reverse rotation starting operation will be described. FIG. 35 is a diagram for explaining the operation of the second and

third cylinders

31Q and 31P when the crankshaft 13 rotates in the reverse direction. FIG. 36 is a schematic diagram for explaining the flow of gas during the reverse rotation starting operation. In FIG. 35, the horizontal axis represents the crank angle. FIG. 35A shows the opening / closing timing of the intake port 21 and the exhaust port 23 and the moving direction of the piston 11 in the second cylinder 31Q, and FIG. 35B shows the third cylinder 31R. The opening / closing timing of the intake port 21 and the exhaust port 23 and the moving direction of the piston 11 are shown.

As shown in FIG. 35B, in the third cylinder 31R, when the crank angle is in the range from the angle A213 to the angle A201, the piston 21 is in a state where both the intake port 21 and the exhaust port 23 are closed. 11 goes up. Therefore, when the communication path 210 is closed, the pressure in the third cylinder 31R increases. On the other hand, as shown in FIG. 35 (a), in the second cylinder 31Q, when the crank angle is in the range from the angle A213 to the angle A201, at least one of the intake port 21 and the exhaust port 23 is opened. Yes. In this case, if the communication path 210 is in a communication state, the gas in the third cylinder 31R flows to the second cylinder 31Q through the communication path 210, thereby suppressing an increase in pressure in the third cylinder 31R. The

For example, when the crank angle is in the range from the angle A111 to the angle A201, the piston 11 descends with the exhaust port 23 opened in the second cylinder 31Q. In this case, as shown in FIG. 36A, the gas in the third cylinder 31R passes through the communication path 210 while the gas flows into the second cylinder 31Q through the exhaust port 23 of the second cylinder 31Q. It flows to the second cylinder 31Q. Therefore, gas is not compressed in the third cylinder 31R, and an increase in pressure in the third cylinder 31R is suppressed.

Further, as shown in FIG. 35 (a), in the second cylinder 31Q, when the crank angle is in the range from the angle A113 to the angle A101, both the intake port 21 and the exhaust port 23 are closed. As a result, the piston 11 rises. Therefore, when the communication path 210 is closed, the pressure in the second cylinder 31Q increases. On the other hand, as shown in FIG. 35B, in the third cylinder 31R, when the crank angle is in the range from the angle A113 to the angle A212, both the intake port 21 and the exhaust port 23 are closed. Then, the piston 11 descends. In this case, when the communication path 210 is in the communication state, the gas in the second cylinder 31Q flows to the third cylinder 31R through the communication path 210 as shown in FIG. Thereby, the gas is not compressed in the second cylinder 31Q, and an increase in pressure in the second cylinder 31Q is suppressed.

Further, as shown in FIG. 35B, when the crank angle is in the range from the angle A212 to the angle A101, the intake port 21 of the third cylinder 31R is opened. Therefore, when the communication path 210 is in a communication state, the gas in the second cylinder 31Q flows to the third cylinder 31R through the communication path 210, thereby suppressing an increase in pressure in the second cylinder 31Q. .

For example, when the crank angle is in the range from the angle A204 to the angle A101, the piston 11 rises in the third cylinder 31R with the intake port 21 opened. In this case, as shown in FIG. 36C, the gas in the second cylinder 31Q flows to the third cylinder 31R through the communication path 210, and the gas in the third cylinder 31R flows out through the intake port 21. . Therefore, gas is not compressed in the second cylinder 31Q, and an increase in pressure in the second cylinder 31Q is suppressed.

FIG. 37 is a diagram showing the relationship between the rotational load of the crankshaft 13 and the crank angle during the forward rotation alignment operation and the reverse rotation start operation. Similarly to FIG. 29, the rotational loads caused by the first, second and

third cylinders

31P, 31Q and 31R are shown in FIGS. 37 (a) to 37 (c), respectively, and the sum of these is shown in FIG. d). As described above, during the forward rotation alignment operation and the reverse rotation start operation, an increase in pressure in the second and

third cylinders

31Q and 31R is suppressed. Specifically, as shown in FIG. 37 (b), even if the crank angle approaches the angle A101 corresponding to the compression top dead center of the second cylinder 31Q, the rotational resistance due to the second cylinder 31Q increases. Is suppressed. Further, as shown in FIG. 37 (c), even when the crank angle approaches A201 corresponding to the compression top dead center of the third cylinder 31R, an increase in rotational resistance due to the third cylinder 31R is suppressed. . As a result, as shown in FIG. 37 (d), the rotational load of the crankshaft 13 increases only in the vicinity of the angle A1 corresponding to the compression top dead center of the first cylinder 31P. The forward rotation and reverse rotation of the shaft 13 are not hindered. Therefore, the forward rotation alignment operation of FIG. 30 and the reverse rotation start operation of FIG. 31 can be appropriately performed.

(4) Engine start process ECU6 performs an engine start process based on the control program previously memorize | stored in memory. In this example, the engine start process includes a cold start process, an idle stop process, and a reverse rotation start process. FIG. 38 is a flowchart for explaining the cold start process. FIG. 39 is a flowchart for explaining the idle stop process. FIG. 40 is a flowchart for explaining the reverse rotation starting process.

When the main switch 40 in FIG. 3 is turned on, the ECU 6 starts the cold start process in FIG. In this case, the current crank angle is not stored in the ECU 6. First, the ECU 6 controls the auxiliary valve drive unit 220 so that the communication path 210 is in a communication state (step S101). Next, the ECU 6 controls the starter / generator 14 so that the crankshaft 13 rotates forward (step S102). In this case, since the communication path 210 is maintained in the communication state, an increase in pressure in the second and

third cylinders

31Q and 31R is suppressed. Thereby, the forward rotation of the crankshaft 13 is not hindered. Further, the starter / generator 14 is based on the detection signal from the current sensor 44 (FIG. 3) so that the crank angle does not reach the angle A1 (FIG. 30) corresponding to the compression top dead center of the first cylinder 31P. Torque is adjusted.

Next, the ECU 6 determines whether or not a specified time has elapsed since the forward rotation of the crankshaft 13 was started in step S102 (step S103). When the specified time has elapsed, the ECU 6 controls the starter / generator 14 so that the forward rotation of the crankshaft 13 is stopped (step S104). As a result, the crank angle is adjusted to the reverse rotation start range (angle A300 in FIG. 30). Thereafter, the ECU 6 controls the auxiliary valve drive unit 220 so that the communication path 210 is closed (step S105), and ends the cold start process.

On the other hand, when the above-described idle stop condition is satisfied, the ECU 6 starts the idle stop process of FIG. First, the ECU 6 injects fuel from each injector 19 (FIG. 3) and each spark plug 18 (FIG. 3) so that combustion is stopped in each of the first, second and

third cylinders

31P, 31Q, 31R. ) Is stopped (step S111).

Next, the ECU 6 determines whether or not the rotational speed of the crankshaft 13 is equal to or less than a specified value based on the detection signal from the crank angle sensor 43 in FIG. 3 (step S112). This prescribed value is a value that is sufficiently lower than the rotational speed of the crankshaft 13 during idling. When the rotational speed of the crankshaft 13 is greater than the prescribed value, the ECU 6 determines that the rotational speed of the crankshaft 13 is less than the prescribed value. Until it becomes, the process of step S112 is repeated.

When the rotational speed of the crankshaft 13 becomes equal to or less than the specified value, the ECU 6 controls the auxiliary valve drive unit 220 so that the communication path 210 is in a communication state (step S113). In this case, an increase in pressure in the second and

third cylinders

31Q and 31R is suppressed, so that the crankshaft 31 when the crank angle approaches the angle A1 corresponding to the compression top dead center of the first cylinder 31P. The rotation of the is easy to stop. Thereby, the rotation of the crankshaft 13 is easily stopped in a state where the crank angle is at or near the reverse rotation start range.

Next, the ECU 6 determines whether or not the rotation of the crankshaft 13 has stopped based on the detection signal from the crank angle sensor 43 (step S114). If the rotation of the crankshaft 13 has not stopped, the ECU 6 repeats the process of step S114 until the rotation of the crankshaft 13 stops.

When the rotation of the crankshaft 13 stops, the ECU 6 determines whether or not the current crank angle is in the reverse rotation start range (step S115). If the current crank angle is not within the reverse rotation start range, the ECU 6 controls the starter / generator 14 so that the crankshaft 13 rotates forward (step S116). As in step S102 of FIG. 38, since the communication path 210 is maintained in the communication state, an increase in pressure in the second and

third cylinders

31Q and 31R is suppressed. Thereby, the forward rotation of the crankshaft 13 is not hindered.

Next, the ECU 6 determines whether or not the crank angle has reached the reverse rotation start range based on the detection signal from the crank angle sensor 43 (step S117). The ECU 6 repeats the process of step S117 until the crank angle reaches the reverse rotation start range. When the crank angle reaches the reverse rotation start range, the ECU 6 controls the starter / generator 14 so that the forward rotation of the crankshaft 13 is stopped (step S118). Thereafter, the ECU 6 controls the auxiliary valve drive unit 220 so that the communication path 210 is closed (step S119), and ends the idle stop process. On the other hand, when the current crank angle is in the reverse rotation start range in step S115, the ECU 6 controls the auxiliary valve drive unit 220 so that the communication path 210 is closed without performing the forward rotation alignment operation. (Step S119), the idle stop process is terminated.

When the starter switch 41 in FIG. 3 is turned on after the cold-start process is completed, the ECU 6 starts the reverse rotation start process in FIG. Further, after the idle stop process ends, when the above-described idle stop release condition is satisfied, the ECU 6 starts the reverse rotation start process of FIG.

In the reverse rotation starting process of FIG. 40, the ECU 6 first controls the auxiliary valve drive unit 220 so that the communication path 210 is in a communication state (step S121). Next, the ECU 6 controls the starter / generator 14 so that the crankshaft 13 rotates in the reverse direction (step S122). In this case, since the communication path 210 is maintained in the communication state, an increase in pressure in the second and

third cylinders

31Q and 31R is suppressed. Thereby, reverse rotation of the crankshaft 13 is not hindered.

Next, the ECU 6 determines whether or not the crank angle has reached the angle A33 in FIG. 31 based on the detection signal from the crank angle sensor 43 (step S123). The ECU 6 repeats the process of step S123 until the crank angle reaches the angle A33. When the crank angle reaches the angle A33, the ECU 6 controls the injector 19 corresponding to the first cylinder 31P so that the fuel is injected into the intake passage 22 (step S124). Next, the ECU 6 determines whether or not the motor current has reached a predetermined threshold value based on the detection signal from the current sensor 44 (step S125). If the motor current has not reached the threshold value, the ECU 6 repeats the process of step S125 until the motor current reaches the threshold value.

When the motor current reaches the threshold value, the ECU 6 controls the starter / generator 14 so that the reverse rotation of the crankshaft 13 is stopped (step S126). Further, the ECU 6 controls the spark plug 18 corresponding to the first cylinder 31P so that the air-fuel mixture in the first cylinder 31P is ignited (step S127). Note that the crankshaft 13 may be driven to rotate in the forward direction by the starter / generator 14 at the time of ignition in step S127 or immediately after ignition.

Next, based on the detection signal from the crank angle sensor 43, the ECU 6 determines whether the rotational speed of the crankshaft 13 has reached a predetermined initial explosion determination value before a predetermined time has elapsed since ignition in step S127. It is determined whether or not (step S128). When the air-fuel mixture is properly combusted in the first cylinder 31P by ignition in step S127, before the crank angle reaches the angle A2 corresponding to the first compression top dead center of the first cylinder 31P. The rotational speed of the crankshaft 13 reaches the initial explosion determination value.

In step S128, when the rotational speed of the crankshaft 13 reaches the initial explosion determination value within a predetermined time, the ECU 6 controls the auxiliary valve drive unit 220 so that the communication path 210 is closed (step S129). The reverse rotation start process is terminated.

On the other hand, when the air-fuel mixture is not properly combusted in the first cylinder 31P by the ignition in step S127, the rotational speed of the crankshaft 13 does not reach the initial explosion determination value. In this case, the crankshaft 13 stops rotating or reversely rotates due to the rotational resistance caused by the pressure in the first cylinder 31P without the crank angle exceeding the angle A2. In this example, when the air-fuel mixture is not properly combusted in this way, the reverse rotation starting operation is repeatedly performed.

In step S128, when the rotation speed of the crankshaft 13 does not reach the initial explosion determination value within a predetermined time, the ECU 6 determines whether the crankshaft 13 is stopped or reversely rotated (step S130). When the crankshaft 13 is not stopped or reversely rotated, the forward rotation of the crankshaft 13 is continued, so the ECU 6 repeats the process of step S130 until the crankshaft 13 stops rotating or reversely rotates.

When the crankshaft 13 stops rotating or reversely rotates, the ECU 6 determines whether or not the reverse rotation starting operation has been repeated a specified number of times (step S131). If the reverse rotation starting operation has not been repeated the specified number of times, the ECU 6 returns to step S122. If the reverse rotation starting operation is repeated a specified number of times, there is a possibility that an abnormality has occurred in the engine system 200. Examples of the abnormality in the engine system 200 include an abnormal operation of the engine unit EU or failure of various sensors. Therefore, the ECU 6 issues a warning (step S132). Specifically, a warning lamp or the like informs the driver that there is a possibility that the engine system 200 is abnormal. Thereafter, the ECU 6 controls the auxiliary valve drive unit 220 so that the communication path 210 is closed (step S129), and ends the reverse rotation starting process.

In the example of FIGS. 9 and 10 or the example of FIG. 20 as well, as in the example of FIG. 40, whether or not the air-fuel mixture is properly combusted in the first cylinder 31A based on the rotational speed of the crankshaft 13 is determined. Such a determination may be made. Further, when it is determined that the air-fuel mixture is not properly burned, the reverse rotation start operation may be repeatedly performed.

(5) Effect In engine system 200 according to the present embodiment, the decompression mechanism DEa suppresses an increase in pressure in second and

third cylinders

31Q and 31R during the forward rotation alignment operation and the reverse rotation start operation. Is done. As a result, an increase in rotational resistance of the crankshaft 13 due to an increase in pressure in the second and

third cylinders

31Q and 31R is suppressed. Therefore, the forward rotation alignment operation and the reverse rotation start operation are smoothly performed without hindering the rotation of the crankshaft 13. Therefore, the air-fuel mixture can be appropriately combusted in the first cylinder 31P, and the engine 10 can be appropriately started. Further, since the torque required for the starter / generator 14 is reduced, the starter / generator 14 and a battery (not shown) can be reduced in size.

Further, in the present embodiment, the second cylinder 31Q and the third cylinder 31R communicate with each other through the communication path 210, thereby suppressing an increase in pressure in the second and

third cylinders

31Q and 31R. Thereby, it is possible to suppress an increase in rotational resistance of the crankshaft 13 due to an increase in pressure in the second and

third cylinders

31Q and 31R with a simple configuration and simple control.

In this embodiment, the

auxiliary valves

212a and 212b are integrally driven to open and close the

openings

211a and 211b of the communication path 210. Thereby, the communication path 210 can be appropriately switched between the communication state and the closed state with a simple configuration.

(6) Other Examples of Decompression Mechanism In the third embodiment, the communication path 210 is maintained in the communication state during the forward rotation alignment operation and the reverse rotation start operation, but the present invention is not limited to this. The communication path 210 may be in a communication state only during a certain period. For example, the communication path 210 may be in a communication state only during a period in which the intake port 21 and the exhaust port 23 are closed and the piston 11 is raised in each of the second and

third cylinders

31Q and 31R.

In the third embodiment, the second cylinder 31Q and the third cylinder 31R communicate with each other through the communication path 210, thereby suppressing an increase in pressure in the second and

third cylinders

31Q and 31R. However, the present invention is not limited to this. For example, when the exhaust valve 16 corresponding to the second cylinder 31Q is lifted, the pressure in the second cylinder 31Q is reduced, and when the exhaust valve 16 corresponding to the third cylinder 31R is lifted, the third The pressure in the cylinder 31R may be reduced. In this case, a decompression mechanism having the same configuration as in FIGS. 22 to 24 may be provided to correspond to each of the second and

third cylinders

31Q and 31R.

[E] Other Embodiments The first to third embodiments described above are examples in which the present invention is applied to a two-cylinder engine and a three-cylinder engine. However, the present invention is applied to a multi-cylinder engine having four or more cylinders. May be. In this case, in the reverse rotation start operation, the air-fuel mixture is combusted in one cylinder, and in the engine start operation including the reverse rotation start operation, the rotation resistance of the crankshaft caused by the pressure increase in one or the other cylinder The pressure in one or the other cylinder is reduced so that the increase is suppressed. Thereby, the engine can be started appropriately.

The above embodiment is an example in which the present invention is applied to a motorcycle. However, the present invention is not limited to this, and other saddle-type vehicles such as an automobile tricycle or an ATV (All Terrain Vehicle) or an automobile The present invention may be applied to other vehicles such as a wheeled vehicle.

[F] Correspondence between Each Component in Claim and Each Element in Embodiment The following describes an example of correspondence between each component in the claim and each element in the embodiment. It is not limited to.

In the above embodiment, the engine system 200 is an example of an engine system, the engine unit EU is an example of an engine unit, the engine 10 is an example of an engine, and the

first cylinders

31A and 31P are first cylinders. The

second cylinders

31B and 31Q are examples of the second cylinder, the third cylinder 31R is an example of the third cylinder, and the starter / generator 14 is an example of the rotation drive unit. The ECU 6 is an example of a control unit, the valve drive unit 17 is an example of an opening / closing mechanism, the decompression mechanisms DE and DEa are examples of a pressure reducing mechanism, the injector 19 is an example of a fuel injection device, and the spark plug 18 is ignited. It is an example of an apparatus. The communication path 210 is an example of a communication path, the

auxiliary valves

212a and 212b and the auxiliary valve drive unit 220 are examples of a communication path opening / closing mechanism, the opening 211a is an example of a first opening, and the opening 211b is a first opening. 2, the auxiliary valve 212 a is an example of the first valve, the auxiliary valve 212 b is an example of the second valve, and the auxiliary valve driving unit 220 is an example of the communication driving unit. The motorcycle 100 is an example of a vehicle, the rear wheel 7 is an example of a driving wheel, and the vehicle body 1 is an example of a main body.

As the constituent elements of the claims, various other elements having configurations or functions described in the claims can be used.

The present invention is applicable to various engine systems and vehicles.

Claims

An engine having a plurality of cylinders;
A rotation drive unit for rotating the crankshaft of the engine in a forward direction and a reverse direction;
A control unit that controls the engine and the rotation drive unit so that an engine start operation including at least a reverse rotation start operation is performed,
The plurality of cylinders include first and second cylinders;
In the reverse rotation starting operation, the air-fuel mixture is introduced into the first cylinder while the crankshaft is rotated in the reverse direction, and the air-fuel mixture is combusted in the first cylinder so that the crankshaft is in the forward direction. Driven by
The engine includes a pressure reducing mechanism that reduces a pressure in at least one of the first and second cylinders,
The pressure reducing mechanism reduces the pressure in the at least one cylinder so that an increase in rotational resistance of the crankshaft due to an increase in pressure in the at least one cylinder is suppressed in the engine starting operation. Engine system.
The engine system according to claim 1, wherein the pressure reducing mechanism reduces the pressure in the at least one cylinder in the reverse rotation starting operation.
The engine further includes an opening / closing mechanism that opens and closes an intake port and an exhaust port of each of the first and second cylinders,
The crank angle ranges corresponding to the intake stroke, compression stroke, expansion stroke, and exhaust stroke of the first cylinder during normal operation are the first intake range, the first compression range, the first expansion range, and the first, respectively. The range of the crank angle corresponding to the intake stroke, compression stroke, expansion stroke, and exhaust stroke of the second cylinder during normal operation is defined as the second intake range, the second compression range, and the second compression range, respectively. Defined as an expansion range and a second exhaust range,
The first exhaust range includes a start-up intake range; the first expansion range includes a start-up ignition range;
The rotation drive unit reversely rotates the crankshaft so that a crank angle exceeds the start intake air range and reaches the start ignition range in the reverse rotation start operation,
The opening / closing mechanism opens the intake port of the first cylinder when the crank angle is in the start intake range in the reverse rotation start operation,
The fuel injection device corresponding to the first cylinder is configured such that, in the reverse rotation start operation, the air-fuel mixture is introduced into the first cylinder when a crank angle is in the start intake air range. Fuel is injected into the intake passage that leads air to
The ignition device corresponding to the first cylinder ignites the air-fuel mixture in the first cylinder when the crank angle is in the start ignition range in the reverse rotation start operation,
The second expansion range includes a starting decompression range;
3. The engine system according to claim 2, wherein, in the reverse rotation start operation, the pressure reduction mechanism reduces the pressure in the second cylinder when a crank angle is in the start pressure reduction range.
At least one of the first compression range and the first intake range includes a reverse rotation start range,
The engine start operation further includes a forward rotation alignment operation of adjusting a crank angle to the reverse rotation start range by rotating the crankshaft in a forward direction before the reverse rotation start operation. Engine system.
The second compression range includes an alignment decompression range;
5. The engine system according to claim 4, wherein the decompression mechanism reduces the pressure in the second cylinder when a crank angle is in the alignment decompression range in the forward rotation alignment operation.
The difference between the crank angle at which the piston reaches compression top dead center in the first cylinder and the crank angle at which the piston reaches compression top dead center in the second cylinder is 360 degrees. The engine system according to any one of 1 to 5.
The fuel injection device corresponding to the second cylinder is provided in the second cylinder in the reverse rotation start operation after the crank angle exceeds the start intake range and before the start ignition range. The engine system according to claim 6, wherein fuel is injected into an intake passage that guides air.
The difference between the crank angle when the piston reaches compression top dead center in the first cylinder and the crank angle when the piston reaches compression top dead center in the second cylinder is an angle other than 360 degrees. The engine system according to any one of claims 3 to 5.
The engine start operation further includes a forward rotation alignment operation for adjusting a crank angle to the reverse rotation start range by rotating the crankshaft in the forward direction before the reverse rotation start operation,
2. The engine system according to claim 1, wherein the pressure reducing mechanism reduces a pressure in at least one of the first and second cylinders in the forward rotation alignment operation.
The engine further includes an opening / closing mechanism that opens and closes an intake port and an exhaust port of each of the first and second cylinders,
The crank angle ranges corresponding to the intake stroke, compression stroke, expansion stroke, and exhaust stroke of the first cylinder during normal operation are the first intake range, the first compression range, the first expansion range, and the first, respectively. The range of the crank angle corresponding to the intake stroke, compression stroke, expansion stroke, and exhaust stroke of the second cylinder during normal operation is defined as the second intake range, the second compression range, and the second compression range, respectively. Defined as an expansion range and a second exhaust range,
The first intake range includes a reverse rotation start range, the first exhaust range includes a start intake range, the first expansion range includes a start ignition range,
The rotation driving unit rotates the crankshaft forward so that the crank angle reaches the reverse rotation start range in the forward rotation alignment operation, and the crank angle is in the reverse rotation start range in the reverse rotation start operation. The crankshaft is reversely rotated so as to reach the start ignition range beyond the start intake air range,
The opening / closing mechanism opens the intake port of the first cylinder when the crank angle is in the start intake range in the reverse rotation start operation,
The fuel injection device corresponding to the first cylinder is configured such that, in the reverse rotation start operation, the air-fuel mixture is introduced into the first cylinder when a crank angle is in the start intake air range. Fuel is injected into the intake passage that leads air to
The ignition device corresponding to the first cylinder ignites the air-fuel mixture in the first cylinder when the crank angle is in the start ignition range in the reverse rotation start operation,
The first compression range includes an alignment decompression range;
10. The engine system according to claim 9, wherein the pressure reducing mechanism reduces the pressure in the first cylinder when a crank angle is in the alignment pressure reducing range in the forward rotation alignment operation.
At least a portion of the first intake range is within the second compression range;
The engine system according to claim 10, wherein, in the reverse rotation starting operation, a crank angle reaches the start ignition range without passing through an angle corresponding to a compression top dead center of the first and second cylinders.
The plurality of cylinders further includes a third cylinder;
The engine system according to claim 2, wherein the pressure reducing mechanism reduces the pressure in the second and third cylinders in the reverse rotation operation.
The engine start operation includes a forward rotation alignment operation that adjusts the crank angle to a predetermined reverse rotation start range by rotating the crankshaft in the forward direction before the reverse rotation start operation,
The engine system according to claim 12, wherein the pressure reducing mechanism reduces the pressure in the second and third cylinders in the forward rotation alignment operation.
The decompression mechanism is
A communication path for communicating the second cylinder and the third cylinder;
A communication path opening and closing mechanism that switches the communication path between a communication state and a closed state;
The engine system according to claim 12 or 13, wherein the communication path opening / closing mechanism reduces the pressure in the second and third cylinders by bringing the communication path into a communication state.
The communication path has a first opening that opens in the second cylinder and a second opening that opens in the third cylinder;
The communication path opening and closing mechanism is
A first valve for opening and closing the first opening;
A second valve for opening and closing the second opening;
A communication drive unit that integrally drives the first and second valves;
The engine system according to claim 14, wherein the communication drive unit reduces the pressure in the second and third cylinders by opening the first and second openings by the first and second valves. .
A main body having a drive wheel;
A vehicle comprising the engine system according to any one of claims 1 to 15, which generates power for rotating the drive wheels.