JP2021032234A - Internal combustion engine - Google Patents

Abstract

To provide an internal combustion engine which can prevent occurrence of an impact caused by rapid decrease of a rotation number of a crank shaft when the engine starts.SOLUTION: An internal combustion engine includes: a starter motor (40) which transmits driving torque to a crank shaft (14) to start an internal combustion engine (1); a one-way clutch (44) which transmits the driving torque of the starter motor to the crank shaft and does not transmit driving torque of the crank shaft to the starter motor; and a crank angle sensor (19) which detects rotation of the crank shaft. Driving of the starter motor is stopped when a deceleration of the crank shaft detected by the crank angle sensor becomes a predetermined value or higher.SELECTED DRAWING: Figure 8

Description

The present invention relates to an internal combustion engine that is started by a starter motor.

In an engine with a large piston compression reaction force such as a single-cylinder engine with a high compression ratio, when the engine is started by a starter motor (starter motor), there is a demand to use a starter motor that is as small and lightweight as possible.

A decompression mechanism is known as a means for reducing the compression reaction force and facilitating starting (for example, Patent Document 1). The decompression mechanism decompresses the combustion chamber by slightly opening the exhaust valve during the compression stroke when the engine is started. More specifically, the decompression cam is urged at a position protruding from the exhaust cam, and the decompression cam is used to slightly open the exhaust valve during the compression stroke when the engine is started. When the engine speed (rotational speed of the crankshaft) increases, the decompression cam is accommodated within the contour of the exhaust cam by the centrifugal force applied to the decompression weight, and the decompression mechanism is switched to the non-operating state. By using such a decompression mechanism, the startability of the engine is improved.

Japanese Patent No. 5446919

By the way, the startability of an engine is affected by the amount of intake air (intake air pressure) from the intake system. For example, if the engine is started with the throttle opening for adjusting the intake air flow rate larger than the idling opening (idle opening), the amount of intake air into the combustion chamber increases. As a result, the compression reaction force becomes larger than usual. Then, even if the decompression mechanism is provided, the driving force of the starter motor for starting the engine may be insufficient. In particular, when the engine speed increases and the decompression mechanism is switched to the non-operating state, it is difficult to cope with the increase in the compression reaction force due to the increase in the intake air amount, and the driving force of the starter motor overcomes the compression reaction force. There is a risk that the engine speed will drop sharply without being able to do so.

A one-way clutch may be used as a means for transmitting the drive torque from the starter motor to the crankshaft when the engine is started and not transmitting the drive torque for the crankshaft to the starter motor in the operating state of the engine. If the crankshaft rotation speed drops sharply as described above when the engine is started, the one-way clutch suddenly reconnects and an impact is generated with a large difference in speed between the crankshaft and the starter motor. However, there is a risk of serious damage to the power transmission path from the starter motor to the crankshaft.

The present invention has been made in view of the above points, and an object of the present invention is to provide an internal combustion engine capable of preventing the generation of an impact due to a sudden decrease in the rotation speed of the crankshaft at the time of starting.

The internal combustion engine of the present invention has a starter motor that transmits drive torque to the crankshaft to start the internal combustion engine, and the drive torque of the starter motor is transmitted to the crankshaft, and the drive torque of the crankshaft is transmitted to the starter motor. It is provided with a one-way clutch that does not allow the crankshaft to rotate, and a crankshaft angle sensor that detects the rotation of the crankshaft. When the deceleration of the crankshaft detected by the crankshaft angle sensor exceeds a predetermined value, the drive of the starter motor is stopped. It is characterized by that.

According to the internal combustion engine of the present invention, the drive of the starter motor is stopped when the deceleration of the crankshaft exceeds a predetermined value, so that the impact when the drive torque is retransmitted from the starter motor to the crankshaft via the one-way clutch is affected. Occurrence can be prevented. That is, it is possible to prevent the generation of an impact due to a sudden decrease in the rotation speed of the crankshaft when the internal combustion engine is started.

It is a side view of an engine. It is a schematic diagram which shows the schematic structure of an engine. It is a perspective view of the starter drive mechanism. It is a perspective view of the valve gear. It is a side view which shows the decompression mechanism of the operating state. It is a side view which shows the decompression mechanism in a non-operating state. It is a graph showing the relationship between the pressure of the intake passage and the engine speed at the time of engine start. (A) is the case of normal engine start, and (B) is the case where the throttle opening is large and the engine speed drops sharply. Shown. It is a graph which shows the engine start control of this embodiment. It is a flowchart which shows the engine start control of this embodiment.

Hereinafter, embodiments to which the present invention is applied will be described with reference to the accompanying drawings. 1 and 2 show the appearance and schematic configuration of the engine 1 which is the internal combustion engine of the present embodiment. FIG. 3 shows a starter drive mechanism 2 for starting the engine 1. 4 to 6 show a valve gear 3 provided in the engine 1 and a decompression mechanism 4 as a part thereof. FIG. 7 is a diagram showing changes in engine speed according to differences in throttle opening. 8 and 9 are diagrams for explaining the start control of the engine 1. In the following description, each direction such as up / down, left / right, front / rear, etc. means a direction based on the vehicle body of the vehicle (motorcycle) on which the engine 1 is mounted.

First, the overall configuration and control system of the engine 1 will be described with reference to FIGS. 1 and 2. This control system is configured to control the operation of the engine 1 and its peripheral configurations by an ECM (Engine Control Module) 5.

The engine 1 is a single-cylinder 4-cycle engine for motorcycles, and is configured by attaching a cylinder block 11 and a cylinder head 12 to an upper portion of a crankcase 10 as shown in FIG. A crankshaft 14 (see FIG. 2) is arranged in a crank chamber formed in the crankcase 10. The crankshaft 14 extends in the left-right direction.

As shown in FIG. 2, a cylinder 15 is formed inside the cylinder block 11, and a piston 16 is arranged in the cylinder 15 so as to be reciprocating. The crankshaft 14 and the piston 16 are connected by a connecting rod, and when the piston 16 reciprocates, the crankshaft 14 is rotated via the connecting rod.

A combustion chamber 17 leading to the upper part of the cylinder 15 is formed in the cylinder head 12, and an ignition plug 18 is provided in the upper part of the combustion chamber 17. The spark plug 18 ignites at a predetermined timing based on the ignition signal output from the ECM 5, and burns a mixture of fuel and air in the combustion chamber 17. The piston 16 is reciprocated by the combustion of the air-fuel mixture, and is output as a rotational motion of the crankshaft 14. The normal rotation direction of the crankshaft 14 during operation of the engine 1 is the forward rotation direction R1, and the rotation direction of the crankshaft 14 opposite to this is the reverse rotation direction R2 (see FIGS. 1 and 3). A crank angle sensor 19 for detecting the rotation angle of the crankshaft 14 is provided, and the crank angle sensor 19 outputs a detected value to the ECM5. The ECM5 calculates the engine speed (rotational speed of the crankshaft 14) based on the detected value input from the crank angle sensor 19.

The cylinder head 12 is formed with an intake port 20 and an exhaust port 21 communicating with the combustion chamber 17. Air for generating an air-fuel mixture flows in through the intake port 20, and the exhaust gas after combustion in the combustion chamber 17 is discharged to the outside through the exhaust port 21. As movable valves involved in intake and exhaust, an intake valve 22 that opens and closes between the intake port 20 and the combustion chamber 17 and an exhaust valve 23 that opens and closes between the exhaust port 21 and the combustion chamber 17 are installed. The intake valve 22 is opened at the timing of taking in outside air (intake stroke), and the exhaust valve 23 is opened at the timing of discharging the exhaust gas (exhaust stroke).

An intake pipe 24 is connected to the upstream end of the intake port 20. The intake port 20 and the intake pipe 24 form an intake passage for inflowing intake air. An air cleaner 25 and a throttle valve 26 are provided in the middle of the intake pipe 24 in order from the upstream side. An air amount sensor 27 is provided in the intake passage between the air cleaner 25 and the throttle valve 26. The air amount sensor 27 detects the air flow rate (intake air amount) that passes through the air cleaner 25 and flows through the intake pipe 24, and outputs the detected value to the ECM5.

The throttle valve 26 is opened and closed by the throttle drive device 28. The throttle drive device 28 drives the throttle valve 26 to change the opening degree in response to the command of the ECM 5, thereby adjusting the flow rate (intake air amount) of the intake air traveling from the intake pipe 24 to the intake port 20. Specifically, the opening degree of the throttle valve 26 is controlled with reference to the intake air amount detected by the air amount sensor 27.

The throttle drive device 28 is provided with a throttle opening sensor 29 that detects the opening degree of the throttle valve 26. The throttle opening sensor 29 detects the opening degree of the throttle valve 26 based on the operating state of the throttle driving device 28, and outputs the detected value to the ECM5.

An injector 30 as a fuel injection device for injecting fuel into the intake port 20 is provided on the downstream side of the throttle valve 26. The injector 30 injects a predetermined amount of fuel into the intake port 20 at a predetermined timing in response to a command from the ECM 5.

An exhaust pipe 31 is connected to the downstream end of the exhaust port 21. The exhaust port 21 and the exhaust pipe 31 form an exhaust passage for exhausting exhaust gas. A catalyst or muffler (not shown) is connected to the exhaust pipe 31.

The operation of the accelerator 32 by the occupant is detected by the accelerator position sensor and input to the ECM 5 as an accelerator operation signal including the accelerator opening degree information. The ECM 5 controls the operation of the spark plug 18, the throttle valve 26, the injector 30, and the like in response to the accelerator operation signal. Specifically, when the output request by the accelerator operation signal becomes large, the ECM 5 increases the opening degree of the throttle valve 26 and increases the fuel injection from the injector 30.

It should be noted that, instead of the electric throttle drive device 28, a throttle of a type in which the accelerator grip operated by the occupant and the throttle body are connected by a wire and the opening degree of the throttle valve 26 is mechanically changed according to the traction amount of the wire. It may be a device. Further, the opening degree of the throttle valve 26 may be detected based on the output of the accelerator position sensor that detects the accelerator opening degree.

As shown in FIG. 1, a clutch cover 33 is attached to the right side surface of the crankcase 10. A clutch chamber (not shown) for accommodating a clutch mechanism (not shown) is formed between the crankcase 10 and the clutch cover 33. The rotation of the crankshaft 14 is transmitted to a transmission mechanism (not shown) via a clutch mechanism, and is taken out as a driving force for driving the driving wheels (rear wheels) of the motorcycle.

An outer peripheral wall 10a projects to the left on the left side surface of the crankcase 10. The outer wall 10a is formed so as to surround the crankshaft 14. A generator cover (not shown) is attached to the left side of the crankcase 10 so as to close the opening surrounded by the outer wall 10a. The generator cover is fixed to the crankcase 10 in contact with the mating surface which is the end surface of the outer peripheral wall 10a. In this state, a generator room surrounded by the crankcase 10 and the generator cover is formed. FIG. 1 shows a state in which the generator cover is removed.

One end of the crankshaft 14 projects into the generator room, and a generator 34 that generates power by rotating the crankshaft 14 is provided in the generator room. The generator 34 has a bottomed cylindrical rotor 34a fixed to the crankshaft 14 and a core (coil) 34b located on the inner diameter side of the rotor 34a. The rotor 34a is made of a magnetic material, and in the operating state of the engine 1, the rotor 34a rotates with the rotation of the crankshaft 14, the magnetic flux density passing through the core 34b changes, and a current is generated in the core 34b by electromagnetic induction. The generator 34 generates alternating current, which is converted to direct current by a rectifier (not shown) and the voltage is controlled below a certain level by a voltage adjustment circuit (not shown). The electric power thus obtained by using the generator 34 is charged in the battery 35 (see FIG. 2) and supplied to the electrical system of the motorcycle equipped with the engine 1.

Subsequently, the configuration of the starter drive mechanism 2 will be described with reference to FIGS. 1 and 3. A starter motor 40 is attached to the upper part of the crankcase 10. The starter motor 40 is driven by receiving electric power from the battery 35. The output shaft 40a projects to the left from the main body of the starter motor 40. The output shaft 40a is inserted in the generator chamber. In the generator room, three starter idle gears 41, 42, and 43 are arranged above the rear part of the generator 34. The output shaft 40a meshes with the starter idle gear 41, and constitutes a gear train that decelerates and transmits the rotation of the output shaft 40a in the order of the starter idle gear 41 to the starter idle gears 42 and 43.

The starter motor 40 is driven by being energized from the battery 35 by the operation of the starter switch 46 (FIG. 2) by the occupant (such as pushing the starter switch 46). When the starter switch 46 is operated, an operation signal is input to the ECM5, and the ECM5 sends a drive signal to the motor driver that drives the starter motor 40. When the operation of the starter switch 46 by the occupant is released, the ECM 5 sends a stop signal to the motor driver, and the starter motor 40 stops.

As shown in FIG. 3, the starter drive mechanism 2 includes a one-way clutch 44. The one-way clutch 44 has a starter gear 44a, an outer ring 44b, and an inner ring 44c. A tooth for meshing with the starter idle gear 43 is formed on the peripheral edge of the starter gear 44a. A cylindrical portion 44d is provided at the center of the starter gear 44a, and an inner ring 44c is arranged between the cylindrical portion 44d and the outer ring 44b.

The outer ring 44b has a shape surrounding the inner ring 44c and is fixed to the rotor 34a (FIG. 1) of the generator 34. Since the rotor 34a is fixed to the crankshaft 14, the outer ring 44b rotates integrally with the crankshaft 14. A plurality of rollers (not shown) are held on the inner ring 44c at different positions in the rotation direction. Each roller comes into contact with a cam surface (not shown) formed on the inner peripheral side of the outer ring 44b and an outer peripheral surface of the cylindrical portion 44d of the starter gear 44a. The space between the outer ring 44b on which each roller is arranged and the cylindrical portion 44d is defined as an accommodation space.

The accommodation space of each roller in the one-way clutch 44 becomes narrower in the radial direction toward the forward rotation direction R1 (the radial distance between the cam surface of the outer ring 44b and the outer peripheral surface of the cylindrical portion 44d becomes smaller). The one-way clutch 44 is provided with an urging member (not shown) that urges each roller in the forward rotation direction R1 (the direction in which the accommodation space becomes narrower in the radial direction). The urging member consists of a spring or the like.

With this one-way clutch 44 configuration, when the starter gear 44a to which the driving force of the starter motor 40 is transmitted rotates in the forward rotation direction R1, each roller is wedged by the contact surface pressure with respect to the cam surface of the outer ring 44b and the outer peripheral surface of the cylindrical portion 44d. The starter gear 44a and the outer ring 44b rotate integrally in the forward rotation direction R1. As a result, when the starter motor 40 is driven while the engine 1 is stopped, the driving torque in the forward rotation direction R1 is transmitted to the crankshaft 14, and the engine 1 can be started. When the start of the engine 1 is completed and the drive of the starter motor 40 is stopped (the operation of the starter switch 46 is released), the starter gear 44a stops rotating.

During operation of the engine 1, the outer ring 44b rotates in the forward rotation direction R1 together with the crankshaft 14. At this time, if the rotation speed of the outer ring 44b in the forward rotation direction R1 exceeds the rotation speed of the starter gear 44a in the forward rotation direction R1 (including the case where the starter gear 44a is stopped), each roller is accommodated in the accommodation space. Of these, the contact surface pressure (effect of the wedge) of each roller with respect to the outer ring 44b and the cylindrical portion 44d is released in order to move toward the side that becomes wider in the radial direction. Therefore, during operation of the engine 1 having an engine speed equal to or higher than a predetermined value, the one-way clutch 44 is in a free state in which the driving torque of the crankshaft 14 is not transmitted to the starter gear 44a and the starter motor 40.

As described above, the one-way clutch 44 has a function of transmitting the drive torque of the starter motor 40 to the crankshaft 14 when the engine 1 is started, and not transmitting the drive torque of the crankshaft 14 during the operation of the engine 1 to the starter motor 40 side. Has.

When the engine 1 is in a state close to stopping (when the rotation speed is low, etc.), the crankshaft 14 may try to rotate in the reverse direction R2 due to a compression reaction force on the piston 16. When the crankshaft 14 rotates in the reverse direction R2, the outer ring 44b rotates in the direction of increasing the contact surface pressure of each roller of the one-way clutch 44 (the effect of the wedge is generated). At this time, if the rotation of the starter gear 44a is regulated by the starter motor 40 in the stopped state, the rotation of the outer ring 44b is restricted via each roller, and it acts to stop the rotation of the crankshaft 14 in the reverse direction R2. ..

Subsequently, the configuration of the valve operating device 3 for opening and closing the intake valve 22 and the exhaust valve 23 will be described mainly with reference to FIGS. 4 to 6. Since the intake valve 22 and the exhaust valve 23 are well known, detailed description of the configuration will be omitted. The intake valve 22 and the exhaust valve 23 are respectively urged in the closing direction by a valve spring (not shown), and the rocker arm (not shown) swings to open and close. The valve gear 3 swings the rocker arm for the intake valve 22 and the rocker arm for the exhaust valve 23 at a predetermined timing in synchronization with the rotation of the crankshaft 14. The valve gear may be of a type in which the intake cam or the exhaust cam presses the tappet to operate the intake valve or the exhaust valve without using the rocker arm.

The valve gear 3 includes a camshaft 49 and a camshaft 50 arranged in a valve chamber formed above the cylinder head 12 (see FIG. 1). The camshafts 49 and 50 extend in the left-right direction in parallel with the crankshaft 14. The camshaft 49 is provided with an intake cam 53, and the camshaft 50 is provided with an exhaust cam 54.

The parts of the valve gear 3 that are involved in driving the exhaust valve 23 are shown in FIGS. 4 to 6. The camshaft 50 is rotatably supported with respect to the cylinder head 12 via bearings 51 and 52. The camshaft 50 is provided (fixed) with two exhaust cams 54 and a cam sprocket 55 at different positions in the axial direction. A cam chain (not shown) is bridged between a cam drive gear (not shown) that rotates integrally with the crankshaft 14 and a cam sprocket 55, and the rotation of the crankshaft 14 is transferred to the cam sprocket 55 via the cam chain. Be transmitted. Therefore, during the operation of the engine 1, the camshaft 50 rotates in synchronization with the crankshaft 14. The rotation direction of the camshaft 50 corresponding to the rotation of the crankshaft 14 in the forward rotation direction R1 is the forward rotation direction R11, and the rotation direction of the camshaft 50 corresponding to the rotation of the crankshaft 14 in the reverse rotation direction R2 is the reverse rotation direction R12. (See FIGS. 4 to 6).

Although detailed description will be omitted, the camshaft 49 provided with the intake cam 53 is rotated in synchronization with the crankshaft 14 via a mechanism (cam chain or cam sprocket) similar to that of the camshaft 50.

A cam surface is formed on the peripheral surfaces of the intake cam 53 and the exhaust cam 54. A cam follower provided on a rocker arm (not shown) on the intake valve 22 side comes into contact with the cam surface of the intake cam 53, and a rocker arm (not shown) on the exhaust valve 23 side with respect to the cam surface of the exhaust cam 54. The cam follower provided in is in contact with the cam follower. When the camshafts 49 and 50 rotate, the contact positions of the cam followers with respect to the cam surfaces of the intake cam 53 and the exhaust cam 54 change, each rocker arm swings, and the intake valve 22 and the exhaust valve 23 are predetermined. The opening and closing operation is performed at the timing of.

The cam surface of the exhaust cam 54 includes a base circle portion 54a and a lift control portion 54b. The base circle portion 54a is a circular (cylindrical) portion having a small radius from the rotation center of the camshaft 50. The lift control unit 54b has a non-circular shape with a larger amount of protrusion toward the outer diameter side with respect to the base circular portion 54a.

When the cam follower of the rocker arm for the exhaust valve 23 faces the base circle portion 54a of the exhaust cam 54, the valve lift amount is zero and the exhaust valve 23 is closed.

When the lift control unit 54b comes into contact with the cam follower of the rocker arm as the camshaft 50 rotates in the forward rotation direction R11, the lift operation of the exhaust valve 23 is started against the urging force of the valve spring. The valve lift amount (opening) of the exhaust valve 23 becomes maximum at the time when the most protruding portion of the lift control unit 54b in the outer diameter direction comes into contact with the cam follower.

Further, when the camshaft 50 rotates in the forward rotation direction R11, the pressure on the rocker arm by the lift control unit 54b is gradually released, and the lift amount of the exhaust valve 23 is gradually reduced by the urging force of the valve spring. Then, the exhaust valve 23 closes with the base circle portion 54a facing the cam follower.

Although detailed description will be omitted, the cam surface of the intake cam 53 includes a base circle portion 53a and a lift control portion 53b as in the exhaust cam 54, and the opening degree of the intake valve 22 is increased according to the rotation of the camshaft 49. To change.

A housing groove 50a extending in the axial direction is formed on a part of the peripheral surface of the camshaft 50. The accommodating groove 50a is formed in a range from the exhaust cam 54 to the cam sprocket 55 in the axial direction. One of the two exhaust cams 54 is formed with a storage recess 54c which is cut out from a part of the peripheral surface of the base circular portion 54a and communicates with the storage groove 50a. The cam sprocket 55 is formed with a circular through hole 55a located on an extension of the accommodating groove 50a.

The valve gear 3 includes a decompression mechanism 4 that performs a decompression operation in which the exhaust valve 23 is slightly opened (given an opening degree) to reduce the compression reaction force when the engine 1 is started. The decompression mechanism 4 has a decompression camshaft 56 and a decompression weight 57.

The decompression camshaft 56 is a columnar member extending in the axial direction of the camshaft 50, and is accommodated in the accommodating groove 50a. The decompression camshaft 56 passes through the inside of the bearing 52, and is supported so as to be able to rotate about the axis of the decompression camshaft 56 itself via the inner surface of the accommodating groove 50a and the bearing 52.

A decompression cam 58 is formed at one end of the decompression cam shaft 56. The decompression cam 58 has a shape (D-cut shape) in which a part of the columnar decompression cam shaft 56 is cut out, and has a cylindrical surface portion 58a corresponding to the uncut portion and a flat surface corresponding to the notched portion. It has a portion 58b.

As shown in FIG. 5, the cylindrical surface portion 58a has a shape (dimension) that protrudes in the outer diameter direction from the base circular portion 54a when facing the outside of the accommodating recess 54c. As shown in FIG. 6, when the flat surface portion 58b faces the outside of the accommodating recess 54c, the flat surface portion 58b is accommodated in the accommodating recess 54c without protruding in the outer diameter direction with respect to the base circular portion 54a (dimensions). Is. That is, in response to the rotation of the decompression camshaft 56 with respect to the camshaft 50, the decompression cam 58 has a protruding position (FIG. 5) that protrudes in the outer diameter direction with respect to the base circle portion 54a of the exhaust cam 54 and a storage position that does not protrude (FIG. 5). It changes to FIG. 6).

The other end of the decompression camshaft 56 penetrates the through hole 55a and connects to the decompression weight 57. The decompression weight 57 is arranged along one side surface of the cam sprocket 55, and rotates (swings) integrally with the decompression cam shaft 56. The decompression weight 57 extends an L-shaped arm 57b from a base end portion 57a connected to the decompression camshaft 56. As shown in FIGS. 5 and 6, the arm 57b has a hook-like shape extending in the reverse direction R12 along the vicinity of the outer circumference of the cam sprocket 55.

As shown in FIG. 4, a support plate 59 is attached to the cam sprocket 55. The support plate 59 supports the decompression weight 57 with the cam sprocket 55, and determines the positions of the decompression camshaft 56 and the decompression weight 57 in the axial direction. Further, the swing range of the decompression weight 57 is determined by the decompression weight 57 coming into contact with a predetermined portion of the support plate 59. Specifically, the protruding position of the decompression cam 58 (FIG. 5) and the storage position of the decompression cam 58 (FIG. 6) are configured to be one end and the other end of the swing range of the decompression weight 57.

The decompression weight 57 is urged by the spring 60 schematically shown in FIGS. 5 and 6 in the direction in which the decompression cam 58 is brought to the protruding position (clockwise in FIGS. 5 and 6). The spring 60 is composed of, for example, a coil spring, a torsion spring, or the like, and the specific form is not limited.

When the camshaft 50 rotates, the decompression weight 57 provided eccentrically from the rotation center of the camshaft 50 swings around the decompression camshaft 56 due to centrifugal force. More specifically, when the camshaft 50 rotates in the forward rotation direction R11, a centrifugal force that causes the decompression weight 57 to swing counterclockwise in FIGS. 5 and 6 acts. When this centrifugal force exceeds the urging force of the spring 60, the decompression weight 57 swings and the decompression cam 58 rotates from the protruding position (FIG. 5) to the retracted position (FIG. 6).

The decompression mechanism 4 having the above configuration operates as follows. When the engine 1 is stopped, the camshaft 50 is not rotating and no centrifugal force is acting on the decompression weight 57. Therefore, as shown in FIG. 5, the decompression cam 58 is held at the protruding position by the urging force of the spring 60, and the decompression mechanism 4 is in the operating state.

When the engine 1 in the stopped state is started, the crankshaft 14 rotates in the forward rotation direction R1 by driving the starter motor 40, and the camshaft 50 rotates in the forward rotation direction R11 accordingly. Then, in the compression stroke, the rocker arm for the exhaust valve 23 is pressed by the cylindrical surface portion 58a of the decompression cam 58 that protrudes in the outer diameter direction from the base circular portion 54a, and the exhaust valve 23 is slightly lifted. As a result, the pressure is released to the exhaust passage, the compression reaction force is reduced, and the piston 16 can exceed the compression top dead center by the driving force of the starter motor 40. Therefore, by using the small starter motor 40, it is possible to realize a reliable start in the engine 1 which is a single cylinder engine having a high compression ratio.

When the engine 1 starts and the crankshaft 14 reaches a predetermined rotation speed (rotational speed in an idle state), the decompression weight 57 supported by the camshaft 50 that rotates in synchronization with the crankshaft 14 is subjected to centrifugal force. It swings against the urging force of the spring 60. Then, the decompression cam 58 of the decompression camshaft 56 connected to the decompression weight 57 rotates from the protruding position of FIG. 5 to the storage position of FIG. As a result, the flat surface portion 58b faces the outer diameter side, and the decompression cam 58 (cylindrical surface portion 58a) is stored in the accommodating recess 54c and does not protrude from the base circular portion 54a, that is, the decompression mechanism 4 is inactive. In the non-operating state of the decompression mechanism 4, the valve lift of the exhaust valve 23 by the decompression cam 58 (cylindrical surface portion 58a) is not performed in the compression stroke, and the engine 1 performs normal operation without decompression operation.

When the operation of the engine 1 is stopped and the rotation speed of the crankshaft 14 becomes equal to or less than a predetermined value, the centrifugal force acting on the decompression weight 57 decreases, the decompression weight 57 swings due to the urging force of the spring 60, and the decompression cam 58 is retracted. It rotates from (FIG. 6) to the protruding position (FIG. 5). As a result, the next engine can be started while the decompression mechanism 4 is operating.

By the way, in an engine having a high compression ratio, under a predetermined condition, the engine speed may rapidly decrease during starting and the engine may stop. Specifically, this corresponds to the case where the throttle is started while being opened wider than a predetermined value (more than the idle opening).

The graph of FIG. 7A shows a case where the starter motor 40 is driven and cranked in a state where the throttle valve 26 is at an idle opening degree, that is, in an appropriate intake state. In FIG. 7A, M1 indicates a pressure change on the downstream side of the intake passage (intake pipe 24 and intake port 20) of the intake passage (intake pipe 24 and intake port 20) on the downstream side of the throttle valve 26, and N1 indicates a change in engine speed (rotation speed of crankshaft 14). Is shown.

When the engine 1 stops, the crankshaft 14 that rotates in the forward rotation direction R1 due to inertia receives resistance due to the compression reaction force in the compression stroke, and then tries to rotate in the reverse rotation direction R2 after stopping. As described above, when the crankshaft 14 rotates in the reverse direction R2, the one-way clutch 44 acts to stop the rotation of the crankshaft 14. Therefore, the stop position of the crankshaft 14 when the engine is stopped tends to be concentrated in a specific range in the compression stroke.

The starter motor 40 is started to be driven by the operation of the starter switch 46 by the occupant. FIG. 7A shows the first ignition cycle of cranking. When the starter motor 40 is driven from the engine stopped state, the crankshaft 14 rotates in the forward rotation direction R1 against the compression reaction force in the compression stroke. Here, the decompression mechanism 4 is in the operating state, and the exhaust valve 23 is slightly opened to rotate the crankshaft 14 while reducing the compression reaction force. Therefore, the driving force of the starter motor 40 causes the first compression top dead center. Can be exceeded. Then, when the crankshaft 14 exceeds the compression top dead center, the engine speed rapidly increases.

When the engine speed increases, the decompression weight 57 of the decompression mechanism 4 swings due to centrifugal force, and the decompression cam 58 rotates from the protruding position (FIG. 4) to the retracted position (FIG. 5). That is, the decompression mechanism 4 is inactive.

The engine speed gradually decreases from the expansion bottom dead center of the crankshaft 14 to the exhaust top dead center. Further, when the intake valve 22 is opened near the exhaust top dead center of the crankshaft 14 and enters the intake stroke, the intake passage (intake port 20, intake pipe 24) becomes negative pressure.

Here, when the throttle valve 26 has an idle opening degree, the amount of intake air from the intake passage (the amount of intake of outside air) is restricted, and the intake air to the combustion chamber 17 side from the throttle valve 26 to the intake port 20. Negative pressure increases. Since the amount of intake air to the combustion chamber 17 is small, the compression reaction force when the crankshaft 14 exceeds the intake bottom dead center and enters the compression stroke is suppressed. As a result, as shown in FIG. 7A, the drop in engine speed during the compression stroke is suppressed, and even if the decompression mechanism 4 is inactive, the inertial force of the crankshaft 14 causes the second compression. The top dead center can be exceeded, and the next ignition cycle can be advanced without stopping the engine.

The graph of FIG. 7B shows a case where the starter motor 40 is driven and cranked in a state where the throttle valve 26 is opened more than a predetermined amount from the idle opening degree, that is, in an excessive intake state. M2 in FIG. 7B shows a pressure change on the downstream side of the intake passage (intake pipe 24 and intake port 20) of the intake passage (intake pipe 24 and intake port 20) on the downstream side of the throttle valve 26, and N2 is a change in engine speed (rotation speed of crankshaft 14). Is shown.

In the case of FIG. 7 (B), the transition is the same as in the case of FIG. 7 (A) described above up to the vicinity of the exhaust top dead center of the first ignition cycle. However, since the opening degree of the throttle valve 26 is large and the intake amount is large, the degree of negative pressure in the intake passage is small in the intake stroke from the vicinity of the exhaust top dead center, and the intake passage is in the compression stroke from the vicinity of the intake bottom dead center. Is equivalent to atmospheric pressure. As a result, the compression reaction force becomes larger than in the case of FIG. 7A. Further, when the decompression cam 58 is in the retracted position and the decompression mechanism 4 is in the non-operating state, the pressure in the combustion chamber 17 cannot be reduced. Due to these factors, as shown in FIG. 7B, the inertial energy of the crankshaft 14 could not exceed the compression reaction force in the compression stroke, and the engine speed increased near the second compression top dead center. It drops sharply, leading to an engine stop.

In particular, if an engine stall occurs while participating in a race with a vehicle equipped with engine 1, the occupant wants to return to running as soon as possible, so the engine is started while operating the accelerator 32 excessively. May cause you to do. Then, the engine is likely to stop due to a start error due to such excessive intake air.

The one-way clutch 44 provided between the crankshaft 14 and the starter motor 40 transmits rotation when the rotation speed (engine rotation speed) on the crankshaft 14 side is relatively higher than the rotation speed on the starter motor 40 side. It becomes a free state in which the starter motor 40 is rotated with no load without performing the above. Therefore, when the engine 1 is properly started as shown in FIG. 7A, the power transmission via the one-way clutch 44 is released when the engine speed reaches a predetermined value or higher, and the starter motor 40 is continued. There is no problem even if it is driven by.

On the other hand, when the engine speed drops sharply as shown in FIG. 7B, the engine speed falls below the speed of the starter motor 40 when the starter motor 40 is continuously driven (energized). Rotational transmission (reconnection) of the one-way clutch 44 suddenly occurs at the stage. Then, there is a possibility that a large impact may occur due to the difference in the amount of operation between the starter motor 40 side, which is rotating at the maximum speed according to the specifications with no load, and the crankshaft 14 side, which has suddenly stopped. This impact damages the parts constituting the starter drive mechanism 2 and generates a loud abnormal noise.

In order to prevent such a problem, the engine 1 of the present embodiment is made to perform the following control and operation. When the engine 1 is started, the ECM 5 continuously monitors the deceleration X (the degree of decrease in the engine speed per unit time) of the engine speed based on the output signal of the crank angle sensor 19. As shown in the graph of FIG. 8, when it is detected that the deceleration X exceeds a predetermined threshold value, the ECM 5 interrupts the motor driver that controls the drive of the starter motor 40 to energize the starter motor 40. A signal is sent so as to stop the drive of the starter motor 40. The drive stop of the starter motor 40 is forcibly executed by the control of the ECM 5 even when the starter switch 46 is continuously turned on by the operation of the occupant.

FIG. 8 shows the boundary value Z of the engine speed at which the one-way clutch 44 switches between the free state and the connected state when the starter motor 40 is rotating at the maximum speed. The one-way clutch 44 is in the free state while the engine speed is higher than the boundary value Z, and the one-way clutch 44 is in the connected state when the engine speed is lower than the boundary value Z.

As shown in FIG. 8, the drive stop of the starter motor 40 based on the deceleration X of the engine speed is before the rotation of the engine 1 suddenly decelerates and drops to the boundary value Z without exceeding the compression reaction force. It is done at the stage of. In other words, the threshold value of the deceleration X of the engine speed, which is the execution condition of the stop control of the starter motor 40, is set so that the starter motor 40 has already stopped when the speed of the engine 1 reaches the boundary value Z. It is set.

As a result, the one-way clutch 44 is prevented from being suddenly connected with an impact under the condition that the starter switch 46 is continuously operated, and the starter drive mechanism 2 is configured without generating the excessive impact described above. It is possible to protect parts and the like.

After a lapse of a predetermined time T from the motor stop, the ECM 5 sends a drive signal of the starter motor 40 to the motor driver, energizes the starter motor 40, and redrives the starter motor 40. The appropriate predetermined time T differs depending on the configuration and specifications of the engine 1, but as an example, the predetermined time T may be set to about 0.1 to 0.5 seconds. After the elapse of the predetermined time T, the driving force is transmitted from the re-driving starter motor 40 to the crankshaft 14 which is in a state where the rotation is stopped or close to it, so that an impact is generated due to a sudden connection by the one-way clutch 44. It can be operated smoothly without doing so.

Stopping and re-driving the starter motor 40 based on the deceleration X of the engine speed is automatically performed as part of the engine start control by the ECM5, and does not require any special operation by the occupant. Further, since the starter motor 40 is automatically re-driven after the elapse of the predetermined time T, it is not necessary for the occupant to repeatedly turn the starter switch 46 on and off. That is, when the engine is started, the occupant only needs to perform a normal operation of turning on the starter switch 46, and the operation is not troublesome. In particular, even if the occupant is impatient and keeps pressing the starter switch 46 during a race or the like, the starter motor 40 and its peripheral structure can be automatically protected from impact and damage.

The flow of engine 1 start control according to the present embodiment will be described with reference to the flowchart of FIG. In step S1, it is checked whether or not the starter switch 46 is operated. When the operation of the starter switch 46 is detected (YES in step S1), it is checked in step S2 whether the drive instruction of the starter motor 40 by the operation is continued. If the drive instruction is continuous (YES in step S2), the process proceeds to step S3, and the ECM5 issues a drive signal to start driving the starter motor 40. Further, the ECM 5 causes the spark plug 18 to be ignited at a predetermined timing in the ignition cycle.

After the start of driving the starter motor 40, it is determined in step S4 whether or not the deceleration of the engine speed (rotational speed of the crankshaft 14) has reached a predetermined value (threshold value) or more. This determination is made by the ECM5 with reference to the output signal of the crank angle sensor 19. If the deceleration does not exceed the predetermined value (NO in step S4), that is, if the crankshaft 14 maintains the rotational speed equal to or higher than the predetermined value, there is no problem even if the starter motor 40 is continuously driven. Since it is in the state, the determination of step S2 and step S4 is continuously performed while continuing to drive the starter motor 40.

When the deceleration of the engine speed exceeds a predetermined value (YES in step S4), the process proceeds to step S5, the ECM5 is controlled to stop energizing the starter motor 40, and the drive of the starter motor 40 is stopped. Let me. Further, in step S5, the ECM 5 stops the ignition execution of the spark plug 18. As a result, the rotation of the crankshaft 14 suddenly stops without the driving force of the starter motor 40 exceeding the magnitude of the compression reaction force due to the opening degree of the throttle valve 26 being too large. Even so, it is possible to prevent the generation of an excessive impact due to the reconnection of the one-way clutch 44.

The ECM5 counts the time from the drive stop of the starter motor 40 in step S5, and determines whether or not a predetermined time (corresponding to T in FIG. 8) has elapsed in step S6. When a predetermined time has elapsed from the drive stop of the starter motor 40 (YES in step S6), the process returns to step S2 and checks whether or not the starter drive instruction continues. If the starter drive instruction continues (YES in step S2), the ECM5 causes the starter motor 40 to be redriven (step S3).

When either the determination in step S1 or the determination in step S2 is NO, that is, when the starter switch 46 is not operated or when the continuous operation of the starter switch 46 (instruction to drive the starter motor 40) is canceled. Finishes the start control and exits from the control flow of FIG.

For example, when it is confirmed that the engine 1 has started properly and the engine 1 has entered the idling state, the occupant cancels the continuous operation of the starter switch 46, so that the determination in step S2 is NO in accordance with the cancellation of the operation. become.

Further, if the driving force of the starter motor 40 cannot exceed the compression reaction force while the opening degree of the throttle valve 26 remains large, the starter motor 40 repeats stopping and re-driving after a while (FIG. FIG. 9 is in a state of looping from step S2 to step S6). When the occupant who recognizes that some error has occurred in starting the engine due to the behavior of the starter motor 40 cancels the continuous operation of the starter switch 46, the determination in step S2 becomes NO.

The above control flow consists of a mode in which the occupant continuously operates the starter switch 46 when starting the engine 1 and a mode in which the occupant temporarily operates the starter switch 46 (once the starter switch 46 is pressed once). It is possible to handle any of the release type operations). In the mode in which the occupant temporarily operates the starter switch 46, in step S2, it is determined that the starter motor 40 is continuously driven from the operation input to the starter switch 46 until a predetermined time elapses. To do.

In order to enhance the recognition to the occupants, when the starter motor 40 is stopped in step S5, it may be controlled to issue a warning by using a notification means such as a sound or a display. As a result, the occupant is informed that an operation that causes an error in starting the engine (such as an unreasonable accelerator operation that causes the opening degree of the throttle valve 26 to be excessively large) is being performed, and the occupant is urged to cancel the operation. Can be done.

As an option, a specified value is set for the number of stops and restarts of the starter motor 40, and a step of determining whether or not the number of stops and restarts of the starter motor 40 exceeds the above specified value is added. May be good. When the motor is stopped and re-driven more than the specified value, the start control is stopped and the starter motor 40 is not re-driven even if the occupant continuously operates the starter switch 46. To do so. As a result, the starter motor 40 can be protected even when the start request continues without eliminating the operation that causes an error in starting the engine.

As described above, in the start control of the engine 1 according to the present embodiment, when a sudden deceleration of the crankshaft 14 leading to the engine stop is detected, the drive of the starter motor 40 is stopped, so that the one-way clutch 44 Can prevent a large impact when reconnecting. As a result, the components of the engine 1, particularly the driving force transmission system from the starter drive mechanism 2 to the crankshaft 14, can be protected, and the risk of component damage can be reduced.

Further, the starter motor 40 does not need to have a high output that enables the engine to start against the compression reaction force even when the amount of intake air from the intake system is excessive, and a small and lightweight starter motor 40 is adopted. it can.

Since the drive stop of the starter motor 40 is automatically controlled by the ECM5 by detecting the deceleration of the crankshaft 14, the occupant does not need to perform complicated operations. Further, since it is realized by controlling the ECM5 based on the detection result of the crank angle sensor 19 and the like, it is not necessary to provide special parts, and the engine 1 can be obtained at low cost without increasing the size.

The present invention is not limited to the above-described embodiment, and can be implemented with various modifications. In the above embodiment, the configuration, control, and the like shown in the accompanying drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

For example, the engine 1 of the above embodiment is a single-cylinder engine having a high compression ratio, and the valve gear 3 is provided with a decompression mechanism 4 in order to cope with the magnitude of the compression reaction force. Since the driving force of the starter motor 40 is set on the premise that the decompression mechanism 4 functions, the intake amount is excessive when the engine speed increases and the decompression mechanism 4 is switched to the non-operating state. Then, there is a problem that the engine speed is likely to decrease sharply as shown in FIG. 7 (B). From this point of view, the present invention is particularly useful for an internal combustion engine provided with a decompression mechanism. However, since the increase in compression reaction force due to the excessive intake amount at the time of starting the engine occurs regardless of the presence or absence of the decompression mechanism, the present invention is also useful for an internal combustion engine not provided with the decompression mechanism. Is.

In the above embodiment, only the deceleration of the engine speed is referred to as a determination element for stopping and re-driving the starter motor 40. In addition to this, the determination may be made with reference to the opening degree of the throttle valve 26 detected by the throttle opening degree sensor 29. The sudden decrease in engine speed may be caused by factors other than the opening degree (intake amount) of the throttle valve 26. By including the opening degree of the throttle valve 26 in the determination element, the start control can be focused when the cause of the sudden decrease in the engine speed is the opening degree (intake amount) of the throttle valve 26.

In other words, the control of driving stop and re-driving of the starter motor 40 with reference only to the deceleration of the engine speed as in the above embodiment is due to factors other than the opening degree (intake amount) of the throttle valve 26. It can be applied and is effective even when a sudden decrease occurs. That is, it can be applied as a countermeasure against the general phenomenon that a large impact is generated when the one-way clutch 44 is reconnected.

The internal combustion engine of the present invention is not limited to a vehicle engine. Regardless of the application, it can be applied to all internal combustion engines having the same configuration.

As described above, the present invention has an effect of preventing the generation of an impact due to a sudden decrease in the engine speed when the internal combustion engine is started, and is particularly useful for an internal combustion engine using a small and lightweight starter motor. ..

1: Engine 2: Starter drive mechanism 3: Valve gear 4: Decompression mechanism 14: Crankshaft 17: Combustion chamber 19: Crank angle sensor 22: Intake valve 23: Exhaust valve 26: Throttle valve (throttle)
29: Throttle opening sensor 34: Generator 35: Battery 40: Starter motor 44: One-way clutch 46: Starter switch 49, 50: Camshaft 53: Intake cam 54: Exhaust cam 56: Decompression camshaft 58: Decompression cam

Claims (4)

A starter motor that transmits drive torque to the crankshaft to start the internal combustion engine,
A one-way clutch that transmits the drive torque of the starter motor to the crankshaft and does not transmit the drive torque of the crankshaft to the starter motor.
A crank angle sensor that detects the rotation of the crankshaft is provided.
An internal combustion engine characterized in that the drive of the starter motor is stopped when the deceleration of the crankshaft detected by the crank angle sensor exceeds a predetermined value. The internal combustion engine according to claim 1, wherein the starter motor is re-driven after a lapse of a predetermined time from the drive stop of the starter motor. A throttle for controlling the air flow rate in the intake passage is provided, and when the throttle is set to an opening larger than the idle opening and the start is performed, when the deceleration of the crankshaft becomes a predetermined value or more, the starter motor said. The internal combustion engine according to claim 1 or 2, wherein the drive is stopped. Equipped with a decompression mechanism capable of decompression operation that decompresses the combustion chamber by giving an opening to the exhaust valve at the time of starting
The internal combustion engine according to any one of claims 1 to 3, wherein the decompression mechanism is in a state of not performing the decompression operation when the drive stop of the starter motor is performed.

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