JP7347015B2 - internal combustion engine - Google Patents

Description

The present invention relates to an internal combustion engine equipped with a decompression mechanism.

A decompression mechanism is known as a means to reduce the compression reaction force in engines with a large compression reaction force on the piston, such as a single-cylinder engine with a high compression ratio, and to make starting easier (for example, a patented decompression mechanism). Reference 1). The decompression mechanism slightly opens the exhaust valve to reduce the pressure in the combustion chamber during the compression stroke when the engine starts.

The decompression mechanism described in Patent Document 1 includes a decompression cam that can protrude from an exhaust cam (exhaust cam lobe) that controls the operation of an exhaust valve. The decompression cam is biased to a position that protrudes from the exhaust cam, and is used to slightly open the exhaust valve during the compression stroke when the engine starts. When the engine speed (rotational speed of the crankshaft) increases, the centrifugal force applied to the decompression weight causes the decompression cam to be accommodated within the contour of the exhaust cam, and the decompression mechanism is switched to a non-operating state. By using such a decompression mechanism, engine startability is improved.

Japanese Patent Application Publication No. 2010-1789

In this type of decompression mechanism, the decompression cam may not return to its operating state (position protruding from the exhaust cam) under certain conditions when the engine is stopped. In recent years, starter motors (starter motors) have been increasingly used as a means to start engines equipped with decompression mechanisms, and there is a demand for small and lightweight starter motors on the premise that the decompression mechanisms function. Therefore, if the starter motor is driven in a state where the decompression mechanism is not functioning, the high compression reaction force cannot be overcome, making it difficult to start the engine. If the starter motor is energized for a long time without starting the engine, a large current will be generated in the starter motor drive circuit, which may cause a malfunction.

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 in which a decompression mechanism functions reliably to improve startability.

The internal combustion engine of the present invention includes a starter motor that transmits driving force to the crankshaft to start the internal combustion engine, and a decompression mechanism that is capable of a decompression operation that gives an opening to the exhaust valve at the time of starting and reduces the pressure in the combustion chamber. and, when the decompression mechanism does not function and the rotation of the crankshaft does not proceed due to the driving force of the starter motor at the time of starting, the starter motor is restarted after a predetermined period of time after stopping the driving of the starter motor. and automatically repeats the drive stop and the re-drive of the starter motor, and each time the drive is stopped, a counter number is added to a counter indicating the number of drive stops of the starter motor, and the number of counters of the counter is a specified value. If the value is reached, the starter motor is not redriven any further .

According to the internal combustion engine of the present invention, when the decompression mechanism does not function, by stopping and driving the starter motor again, the decompression mechanism can be made to function reliably and startability can be improved.

FIG. 3 is a side view of the engine. FIG. 1 is a schematic diagram showing a schematic configuration of an engine. It is a perspective view of a starter drive mechanism. It is a perspective view of a valve train. FIG. 3 is a side view showing the decompression mechanism in an operating state. FIG. 3 is a side view showing the decompression mechanism in an inoperative state. FIG. 3 is a diagram showing functional recovery of the decompression mechanism. It is a graph showing engine starting control of this embodiment. It is a flowchart which shows engine start control of this embodiment.

Embodiments to which the present invention is applied will be described below with reference to the accompanying drawings. FIGS. 1 and 2 show the appearance and schematic configuration of an engine 1, which is an internal combustion engine of this embodiment. FIG. 3 shows a starter drive mechanism 2 for starting the engine 1. As shown in FIG. 4 to 6 show a valve train 3 provided in the engine 1 and a decompression mechanism 4 that is a part of the valve train 3. FIG. 7 is a diagram showing functional recovery of the decompression mechanism 4. 8 and 9 are diagrams for explaining starting control of the engine 1. In the following description, directions such as up and down, left and right, and front and rear mean directions based on the body of the vehicle (motorcycle) in which the engine 1 is mounted.

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

The engine 1 is a single-cylinder four-stroke engine for a motorcycle, and as shown in FIG. 1, the engine 1 is constructed by attaching a cylinder block 11 and a cylinder head 12 to the upper part of a crankcase 10. A crankshaft 14 (see FIG. 2) is arranged in a crank chamber formed within 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 disposed within the cylinder 15 so as to be able to reciprocate. 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 communicating with the upper part of the cylinder 15 is formed in the cylinder head 12, and a spark 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 combusts a mixture of fuel and air within the combustion chamber 17. The combustion of the air-fuel mixture causes the piston 16 to reciprocate, which is output as a rotational movement of the crankshaft 14. The normal rotational direction of the crankshaft 14 during operation of the engine 1 is defined as a forward rotation direction R1, and the opposite rotational direction of the crankshaft 14 is defined as a reverse rotation direction R2 (see FIGS. 1 and 3). A crank angle sensor 19 is provided to detect the rotation angle of the crankshaft 14, and the crank angle sensor 19 outputs a detected value to the ECM 5. The ECM 5 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 that communicate with the combustion chamber 17 . Air for generating a mixture flows in through the intake port 20, and exhaust gas after being combusted 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 to take in outside air (intake stroke), and the exhaust valve 23 is opened at the timing to discharge 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 constitute an intake passage through which intake air flows. In the middle of the intake pipe 24, an air cleaner 25 and a throttle valve 26 are provided 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) passing through the air cleaner 25 and flowing inside the intake pipe 24, and outputs the detected value to the ECM 5.

The throttle valve 26 is opened and closed by a throttle drive device 28. The throttle drive device 28 drives the throttle valve 26 in response to a command from the ECM 5 to change the opening degree, thereby adjusting the flow rate (intake air amount) of intake air that advances 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 of the throttle valve 26 . The throttle opening sensor 29 detects the opening of the throttle valve 26 based on the operating state of the throttle drive device 28, and outputs the detected value to the ECM 5.

An injector 30 serving as a fuel injection device that injects fuel into the intake port 20 is provided downstream of the throttle valve 26 . The injector 30 injects a predetermined amount of fuel into the intake port 20 at a predetermined timing in accordance with 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 constitute an exhaust passage through which exhaust gas is discharged. A catalyst and a muffler (not shown) are connected to the exhaust pipe 31.

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

Note that instead of using the electric throttle drive device 28, this type of throttle connects the accelerator grip operated by the passenger with a wire to the throttle body, and mechanically changes the opening degree of the throttle valve 26 according to the amount of pull 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 an 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) that accommodates 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 extracted as driving force for driving drive wheels (rear wheels) of the motorcycle.

An outer wall 10a projects leftward from the left side surface of the crankcase 10. The outer surrounding wall 10a is formed 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 by coming into contact with a mating surface that is an end surface of the outer wall 10a. In this state, a generator chamber surrounded by the crankcase 10 and the generator cover is formed. Figure 1 shows the generator with the cover removed.

One end of the crankshaft 14 protrudes into the generator chamber, and a generator 34 that generates power by rotation of the crankshaft 14 is provided in the generator chamber. 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 when the engine 1 is in operation, the rotor 34a rotates as the crankshaft 14 rotates, the magnetic flux density passing through the core 34b changes, and current is generated in the core 34b due to electromagnetic induction. The alternating current generated by the generator 34 is converted into direct current by a rectifier (not shown), and the voltage is controlled to be below a certain level by a voltage regulating circuit (not shown). The electric power thus obtained using the generator 34 is charged into a battery 35 (see FIG. 2), and is supplied to the electrical system of the motorcycle equipped with the engine 1.

Next, the configuration of the starter drive mechanism 2 will be explained 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 power from the battery 35. An output shaft 40a protrudes leftward from the main body of the starter motor 40. The output shaft 40a is inserted into the generator chamber. In the generator room, three starter idle gears 41, 42, and 43 are arranged above the rear of the generator 34. The output shaft 40a meshes with a starter idle gear 41, forming a gear train that reduces and transmits the rotation of the output shaft 40a in order from the starter idle gear 41 to the starter idle gears 42 and 43.

The starter motor 40 is powered by the battery 35 and driven by the operation of the starter switch 46 (FIG. 2) by a passenger (such as pushing the starter switch 46). When the starter switch 46 is operated, an operation signal is input to the ECM 5, and the ECM 5 sends a drive signal to the motor driver that drives the starter motor 40. When the operator releases the starter switch 46, 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. Teeth with which the starter idle gear 43 meshes are 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 disposed between the cylindrical portion 44d and the outer ring 44b.

The outer ring 44b has a shape that surrounds 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 together with the crankshaft 14. The inner ring 44c holds a plurality of rollers (not shown) at different positions in the rotational direction. Each roller contacts a cam surface (not shown) formed on the inner circumferential side of the outer ring 44b and an outer circumferential surface of the cylindrical portion 44d of the starter gear 44a. The space between the outer ring 44b and the cylindrical portion 44d where each roller is arranged is defined as a housing space.

The accommodation space for each roller in the one-way clutch 44 becomes narrower in the radial direction (the radial interval between the cam surface of the outer ring 44b and the outer circumferential surface of the cylindrical portion 44d becomes smaller) as it advances in the normal rotation direction R1. The one-way clutch 44 is provided with a biasing member (not shown) that biases each roller in the forward rotation direction R1 (the direction in which the accommodation space narrows in the radial direction). The biasing member is made of a spring or the like.

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

While the engine 1 is operating, the outer ring 44b rotates together with the crankshaft 14 in the normal rotation direction R1. At this time, if the rotation speed of the outer ring 44b in the normal rotation direction R1 exceeds the rotation speed of the starter gear 44a in the normal rotation direction R1 (including the case where the starter gear 44a is stopped), each roller is moved into the accommodation space. Since the rollers tend to move toward the side that is wider in the radial direction, the contact surface pressure (wedge effect) of each roller against the outer ring 44b and the cylindrical portion 44d is released. Therefore, while the engine 1 is operating at a predetermined engine speed or higher, the one-way clutch 44 is in a free state in which it does not transmit the driving torque of the crankshaft 14 to the starter gear 44a or the starter motor 40.

In this way, the one-way clutch 44 has the function of transmitting the driving torque of the starter motor 40 to the crankshaft 14 when the engine 1 is started, and not transmitting the driving torque of the crankshaft 14 to the starter motor 40 while the engine 1 is running. has.

Note that when the engine 1 is close to stopping (for example, when the rotational speed is low), the crankshaft 14 may attempt to rotate in the reverse direction R2 due to compression reaction force against the piston 16. When the crankshaft 14 rotates in the reverse direction R2, the outer ring 44b rotates in a direction that increases the contact surface pressure of each roller of the one-way clutch 44 (creating a wedge effect). At this time, if the rotation of the starter gear 44a is restricted by the starter motor 40 in the stopped state, the rotation of the outer ring 44b is restricted via each roller, which acts to stop the rotation of the crankshaft 14 in the reverse direction R2. .

Next, the configuration of the valve train 3 that opens and closes the intake valve 22 and the exhaust valve 23 will be described with reference mainly to FIGS. 4 to 6. Since the intake valve 22 and the exhaust valve 23 are well known, detailed explanation of their configuration will be omitted. The intake valve 22 and the exhaust valve 23 are each biased in a closing direction by a valve spring (not shown), and are opened and closed by swinging of a rocker arm. The valve train 3 swings a rocker arm (not shown) for the intake valve 22 and a rocker arm 61 (FIG. 7) for the exhaust valve 23 at a predetermined timing in synchronization with the rotation of the crankshaft 14. Note that a type of valve operating device may be used in which an intake cam or an exhaust cam presses a tappet to operate an intake valve or an exhaust valve without using a rocker arm.

The valve train 3 includes a camshaft 49 and a camshaft 50 that are arranged in a valve train chamber formed in the upper part of the cylinder head 12 (see FIG. 1). The camshafts 49 and 50 extend parallel to the crankshaft 14 in the left-right direction. An intake cam 53 is provided on the camshaft 49, and an exhaust cam 54 is provided on the camshaft 50.

Parts of the valve train 3 that are involved in driving the exhaust valve 23 are shown in FIGS. 4 to 6. The camshaft 50 is rotatably supported by the cylinder head 12 via bearings 51 and 52. The camshaft 50 is provided with two exhaust cams 54 and a cam sprocket 55 at different positions in the axial direction (fixed). A cam chain (not shown) is spanned between a cam drive gear (not shown) that rotates together with the crankshaft 14 and a cam sprocket 55, and the rotation of the crankshaft 14 is transmitted to the cam sprocket 55 via the cam chain. communicated. Therefore, while the engine 1 is operating, 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 referred to as 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 referred to as the reverse rotation direction R12. (See Figures 4 to 6).

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

Cam surfaces are formed on the circumferential 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 contacts the cam surface of the intake cam 53, and a cam follower provided on a rocker arm (not shown) on the exhaust valve 23 side contacts the cam surface of the exhaust cam 54 (Fig. ) is in contact with a cam follower 61a (FIG. 7). 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, causing each rocker arm to swing, causing the intake valve 22 and the exhaust valve 23 to move to their respective predetermined positions. The opening and closing operations are performed at the timing of .

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

When the cam follower 61a of the rocker arm 61 for the exhaust valve 23 faces the base circular portion 54a of the exhaust cam 54, the valve lift amount is zero and the exhaust valve 23 is closed.

As the camshaft 50 rotates in the normal rotation direction R11, when the lift control section 54b comes into contact with the cam follower 61a of the rocker arm 61, the lift operation of the exhaust valve 23 is started against the biasing force of the valve spring. The valve lift amount (opening degree) of the exhaust valve 23 reaches its maximum at the time when the part of the lift control section 54b that most protrudes in the outer diameter direction comes into contact with the cam follower 61a.

When the camshaft 50 further rotates in the normal rotation direction R11, the pressure on the rocker arm 61 by the lift control section 54b is gradually released, and the lift amount of the exhaust valve 23 gradually decreases due to the biasing force of the valve spring. Then, the exhaust valve 23 is closed with the base circular portion 54a facing the cam follower 61a.

Although a detailed explanation will be omitted, the cam surface of the intake cam 53 includes a base circular portion 53a and a lift control portion 53b similarly to the exhaust cam 54, and the opening of the intake valve 22 is adjusted according to the rotation of the camshaft 49. change.

A housing groove 50a extending in the axial direction is formed in a part of the circumferential surface of the camshaft 50. The housing groove 50a is formed in the range from the exhaust cam 54 to the cam sprocket 55 in the axial direction. In one of the two exhaust cams 54, a part of the circumferential surface of the base circular portion 54a is cut out to form an accommodation recess 54c that communicates with the accommodation groove 50a. The cam sprocket 55 has a circular through hole 55a located on an extension of the housing groove 50a.

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

The decompression camshaft 56 is a cylindrical member extending in the axial direction of the camshaft 50, and is accommodated in the accommodation groove 50a. The decompression camshaft 56 passes inside the bearing 52, and is supported via the inner surface of the housing groove 50a and the bearing 52 so as to be rotatable about its own axis.

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

As shown in FIG. 5, the cylindrical surface portion 58a has a shape (dimensions) that protrudes further in the outer radial direction than the base circular portion 54a when facing outward from the accommodation recess 54c. As shown in FIG. 6, the flat portion 58b has a shape (dimensions) that is accommodated in the accommodation recess 54c without protruding in the outer radial direction with respect to the base circular portion 54a when facing outward of the accommodation recess 54c. It is. That is, depending on the rotation of the decompression camshaft 56 with respect to the camshaft 50, the decompression cam 58 is moved between a protruding position (FIG. 5) in which it protrudes in the outer radial direction with respect to the base circular portion 54a of the exhaust cam 54, and a retracted position (in which it does not protrude). Figure 6).

The other end of the decompression camshaft 56 passes through the through hole 55a and is connected to the decompression weight 57. The decompression weight 57 is arranged along one side of the cam sprocket 55 and rotates (swings) integrally with the decompression camshaft 56. The decompression weight 57 has an L-shaped arm 57b extending from a base end 57a connected to the decompression camshaft 56. As shown in FIGS. 5 and 6, the arm 57b has a hook-like shape that extends in the reverse rotation direction R12 along the vicinity of the outer periphery 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 between it and the cam sprocket 55, and determines the positions of the decompression camshaft 56 and the decompression weight 57 in the axial direction. Furthermore, 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 (FIG. 5) of the decompression cam 58 and the retracted position (FIG. 6) of the decompression cam 58 are configured to be at one end and the other end of the swinging range of the decompression weight 57.

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

When the camshaft 50 rotates, the decompression weight 57, which is 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 normal rotation direction R11, a centrifugal force acts that causes the decompression weight 57 to swing counterclockwise in FIGS. 5 and 6. 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 in the protruding position by the biasing force of the spring 60, and the decompression mechanism 4 is in an operating state.

When starting the stopped engine 1, the starter motor 40 is driven to rotate the crankshaft 14 in the normal rotation direction R1, and in response, the camshaft 50 rotates in the normal rotation direction R11. Then, in the compression stroke, the rocker arm 61 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, pressure is released to the exhaust passage, the compression reaction force is reduced, and the driving force of the starter motor 40 allows the piston 16 to exceed the compression top dead center. Therefore, using the small starter motor 40, reliable starting of the engine 1, which is a single cylinder engine with a high compression ratio, can be realized.

When the engine 1 starts and the crankshaft 14 reaches a predetermined rotational speed (idle rotational speed), the decompression weight 57 supported by the camshaft 50, which rotates in synchronization with the crankshaft 14, is moved by 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 shown in FIG. 5 to the retracted position shown in FIG. 6. As a result, the flat portion 58b faces toward the outer diameter side, and the decompression cam 58 (cylindrical surface portion 58a) is stored in the accommodation recess 54c and does not protrude beyond the base circular portion 54a, that is, the decompression mechanism 4 is in a non-operating state. When the decompression mechanism 4 is in a non-operating state, the decompression cam 58 (cylindrical surface portion 58a) does not lift the exhaust valve 23 during the compression stroke, and the engine 1 performs normal operation without decompression operation.

When the engine 1 stops operating and the rotational speed of the crankshaft 14 falls below a predetermined value, the centrifugal force acting on the decompression weight 57 decreases, the decompression weight 57 swings due to the biasing force of the spring 60, and the decompression cam 58 moves to the storage position. (Fig. 6) to the protruding position (Fig. 5). Thereby, the next engine start can be performed with the decompression mechanism 4 operating.

By the way, as shown in FIG. 7A, under certain conditions, the decompression cam 58 may not return to the protruding position when the engine 1 is stopped, and the decompression mechanism 4 may not function. In the state shown in FIG. 7A, the flat portion 58b of the decompression cam 58 faces the cam follower 61a of the rocker arm 61, and the decompression cam 58 stored in the storage recess 54c (in the storage position) moves to the protruding position. Rotation is prevented. As a result, the decompression cam 58, which was in the retracted position due to centrifugal force during engine operation, remains in the retracted position even when the engine 1 stops operating.

For example, when the engine is stopped, the crankshaft 14, which rotates in the forward rotation direction R1 due to inertia, stops due to resistance due to the compression reaction force in the compression stroke, and then attempts to rotate in the reverse rotation direction R2. 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 stopping position of the crankshaft 14 when the engine is stopped tends to be concentrated in a specific range in the compression stroke. When the crankshaft 14 is suddenly stopped at a specific position in the compression stroke due to the interaction between the compression reaction force and the one-way clutch 44, the rotation of the camshaft 50 is also stopped suddenly. At this time, if the decompression cam 58 is facing the cam follower 61a of the rocker arm 61, before the decompression cam 58 returns from the retracted position to the protruding position due to the urging force of the spring 60, the decompression cam 58 is brought into contact with the flat part 58b and the cam follower 61a. The return rotation of is restricted, resulting in the state shown in FIG. 7(A).

Another cause of the decompression mechanism 4 not functioning is that when the engine 1 stops, the decompression cam 58 once rotates from the retracted position to the protruding position due to the biasing force of the spring 60, but after that the crankshaft 14 and the camshaft As the decompression cam 50 rotates in the reverse directions R2 and R12, the decompression cam 58 may come into contact with the cam follower 61a and be pushed back to the storage position, resulting in the state shown in FIG. 7(A).

Regardless of the cause, if the state shown in FIG. 7A occurs when the engine 1 is stopped, the engine will be started next time from a non-operating state in which the decompression mechanism 4 cannot function as intended. The output of the starter motor 40 is set on the premise that the decompression mechanism 4 is in operation, so if the decompression mechanism 4 remains inactive, the driving torque required for the starter motor 40 (compression top dead center (torque required to overcome this) becomes excessive, making it impossible to start the engine 1 even if the starter motor 40 continues to be energized. If this state continues, there is a risk that a large current will be generated in the drive circuit of the starter motor 40, resulting in a problem (burnout of the circuit, etc.). The present embodiment prevents such problems and allows the decompression mechanism 4 to function regardless of the state when the engine is stopped, thereby realizing reliable starting of the engine 1. The details will be explained below.

FIG. 8 shows the relationship between the cylinder pressure (the internal pressure of the cylinder 15 and the combustion chamber 17) and the overcoming torque during the compression stroke. The cylinder pressure P1 when the decompression mechanism 4 is in the operating state (the decompression cam 58 is in the protruding position) is smaller than the cylinder pressure P2 when the decompression mechanism 4 is in the non-operation state (the decompression cam 58 is in the retracted position). . Depending on the difference between the cylinder pressures P1 and P2, the overcoming torque Q1 is applied by the starter motor 40 when the decompression mechanism 4 is in an operating state, and the overcoming torque Q1 is applied by the starter motor 40 when the decompression mechanism 4 is in an inactive state. Q2 is different.

If the overcoming torque is within the range of the motor setting torque QM, which is the maximum torque according to the specifications of the starter motor 40 (if it is above the motor setting torque QM in the graph of FIG. 8), it will resist the compression reaction force. The starter motor 40 can rotate the crankshaft 14 in the normal rotation direction R1.

As shown in FIG. 8, the overcoming torque Q1 when the decompression mechanism 4 is in the operating state is within the range of the motor setting torque QM until it exceeds the compression top dead center V1, and the starter motor 40 acts against the compression reaction force. Can be cranked.

On the other hand, when the decompression mechanism 4 is in a non-operating state, the overcoming torque Q2 and the motor setting torque QM intersect in the middle. At this intersection position, the drive torque of the starter motor 40 and the compression reaction force of the engine 1 are balanced, and the crankshaft 14 cannot be rotated any further in the normal rotation direction R1. The angular position of the crankshaft 14 in this state is defined as a torque balance position V2. As mentioned above, since the output of the starter motor 40 is set on the premise that the decompression mechanism 4 is functioning to reduce the compression reaction force, when the decompression mechanism 4 is not operating, only the driving torque of the starter motor 40 is generated. In this case, the compression top dead center V1 cannot be overcome, and a torque balance position V2 exists.

Regarding the angular position of the crankshaft 14, the position where the decompression mechanism 4 functions (the position where the cylindrical surface portion 58a of the decompression cam 58 presses the cam follower 61a of the rocker arm 61 to perform the decompression operation) is defined as a decompression function position V3. As shown in FIG. 8, the torque balance position V2 is set closer to the compression top dead center V1 than the decompression function position V3. In other words, in the normal rotation directions R1 and R11 of the crankshaft 14 and the camshaft 50, the decompression function position V3, the torque balance position V2, and the compression top dead center V1 are set in this order.

In the state shown in FIG. 7A, the decompression cam 58 is stored in the accommodation recess 54c and is not functioning, but the angular position of the crankshaft 14 corresponds to the decompression function position V3. Then, when the occupant operates the starter switch 46 to drive the starter motor 40 in the state shown in FIG. Rotate until. In this case, since the relationship between the cylinder pressure P2 and the overcoming torque Q2 shown in FIG. It remains stopped at position V2 and engine 1 is not started properly.

The angular position of the exhaust cam 54 corresponding to the torque balance position V2 of the crankshaft 14 is shown in FIG. 7(B). As the decompression cam 58 rotates from the decompression function position V3 (FIG. 7(A)) to the torque balance position V2, the decompression cam 58 is no longer in a positional relationship facing the cam follower 61a of the rocker arm 61, and the decompression cam 58 is no longer restricted from rotation by the cam follower 61a. , is rotated from the retracted position to the protruding position by the biasing force of the spring 60.

The ECM 5 counts the time from the start of driving the starter motor 40 and monitors the output signal of the crank angle sensor 19. Then, if the rotation of the crankshaft 14 is not detected even after a predetermined period of time has elapsed (the speed of the crankshaft 14 is zero, or the behavior is such that it can be considered as zero), the drive of the starter motor 40 is stopped. .

When the starter motor 40 stops driving, the force that rotates the crankshaft 14 in the normal rotation direction R1 is released and the force balance state is released, so that the crankshaft 14 receiving the compression reaction force is decompressed from the torque balance position V2. Rotates in reverse direction R2 toward functional position V3. Then, as shown in FIG. 7(C), the exhaust cam 54 rotates in the reverse direction R12, and the decompression cam 58 is positioned to face the cam follower 61a of the rocker arm 61.

When the starter motor 40 is driven to rotate to the torque balance position V2, the decompression cam 58 is returned to the protruding position by the biasing force of the spring 60. Therefore, when the crankshaft 14 rotating in the reverse direction R2 reaches the decompression function position V3, as shown in FIG. push in the direction. As a result, the decompression mechanism 4 becomes activated, and the function of the decompression mechanism 4 is restored.

Then, when the starter motor 40 is driven again with the function of the decompression mechanism 4 recovered, the relationship between the cylinder pressure P1 and the overcoming torque Q1 has been changed as shown in FIG. can be started.

The operation of the crankshaft 14 at the time of starting the engine is schematically shown in FIG. 8 by a dashed line F. When the starter motor 40 is first driven from a stopped state of the engine 1, the crankshaft 14 rotates forward to the torque balance position V2 (F1), and when it reaches the torque balance position V2, the compression reaction force prevents it from rotating further. limited. When the drive of the starter motor 40 is stopped, the crankshaft 14 receives the compression reaction force and reverses from the torque balance position V2 to the decompression function position V3 (F2). Subsequently, by re-driving the starter motor 40, the crankshaft 14 performs normal rotation from the decompression function position V3 (F3). When the starter motor 40 is driven again, the decompression mechanism 4 has recovered its function, so the crankshaft 14 can continue to rotate normally without being stopped by the compression reaction force.

With reference to the flowchart of FIG. 9, the flow of starting control of the engine 1 in this embodiment will be described. In step S1, it is checked whether the starter switch 46 has been operated. When the operation of the starter switch 46 is detected (YES in step S1), it is checked in step S2 whether the instruction to drive the starter motor 40 by the operation continues. If the drive instruction is continuous (YES in step S2), the process advances to step S3, where the ECM 5 issues a drive signal to start driving the starter motor 40. Further, the ECM 5 starts counting the time from when the starter motor 40 is driven. Although not explicitly shown in step S3, the ECM 5 also executes various operations necessary for starting the engine 1, such as fuel injection from the injector 30 and ignition using the spark plug 18, in conjunction with the driving of the starter motor 40.

After starting driving of the starter motor 40, it is determined in step S4 whether or not the crankshaft 14 is rotating. This determination is made by the ECM 5 with reference to the output signal of the crank angle sensor 19. If rotation of the crankshaft 14 is detected (YES in step S4), the process returns to step S2 and it is determined whether the instruction to drive the starter motor 40 continues.

If the rotation of the crankshaft 14 is not detected even after a predetermined period of time has elapsed since the start of driving the starter motor 40 (NO in step S4), the process proceeds to step S5, where the ECM 5 controls the starter motor 40 to stop being energized. , the driving of the starter motor 40 is stopped. Although not explicitly stated in step S5, the ECM 5 also stops fuel injection from the injector 30 and ignition from the spark plug 18 when the starter motor 40 is stopped.

When the starter motor 40 is driven with the decompression mechanism 4 inactive as shown in FIG. It becomes impossible to proceed to the dead center V1 side. Then, by stopping the driving of the starter motor 40 in step S5, the crankshaft 14 is rotated in the reverse direction R2 (towards the decompression function position V3) by the compression reaction force. That is, the crankshaft 14 performs the operations from F1 to F2 shown in FIG. Through this series of operations of the crankshaft 14, the decompression mechanism 4 rotates the decompression cam 58 from the storage position to the protrusion position, returning to the operating state shown in FIG. 7(C).

In step S6 following step S5, a counter number "1" is added to a counter indicating the number of times the starter motor 40 is stopped, and the process waits for a specified time. This waiting time is the time required for the rotation of the crankshaft 14 in the reverse direction R2 (F2 in FIG. 8) caused by the stoppage of the starter motor 40 and the time required for the decompression cam 58 to push the rocker arm 61 (FIG. 7(C)). A predetermined margin is added. The waiting time in step S6 varies depending on the configuration of the engine, but is set to about 0.1 to 0.5 seconds, as an example.

It is determined in step S7 whether the number of counters set in step S6 has reached a specified value. If the counter number is less than the specified value (NO in step S7), the process returns to step S2. Therefore, while the rotation of the crankshaft 14 is not detected even though the drive instruction for the starter motor 40 continues (NO in step S4), it is determined that the function of the decompression mechanism 4 has not been recovered, and the counter Stopping the starter motor 40 (step S5) and re-driving it (step S3) are repeated until the number reaches the specified value. In other words, the starter motor 40 is controlled to be automatically stopped and restarted a predetermined number of times.

If the decompression mechanism 4 does not return to the operating state by stopping the starter motor 40 once, the possibility that the decompression mechanism 4 will return to the operating state increases by stopping and re-driving the starter motor 40 multiple times. The specified value of the counter number in step S7 is set to a value that is assumed to be sufficient to return the decompression mechanism 4 to the operating state. Generally, the operations and controls from step S3 to step S6 only need to be performed about twice, so it is preferable to set the specified value of the counter number in step S7 to "2", "3", or the like. However, if necessary, the number of times the starter motor 40 is stopped and restarted may be increased by setting the predetermined value of the counter number in step S7 to be greater than that value.

If the counter number reaches the specified value (YES in step S7), some kind of error has occurred that prevents the decompression mechanism 4 from returning to the operating state, or another type of error has occurred other than the decompression mechanism 4 that prevents the engine from starting. It is assumed that there is a possibility that Therefore, when the counter number reaches the specified value in step S7, the control flow of FIG. 9 is exited without re-driving the starter motor 40 any further.

In addition, when the counter number reaches a predetermined value in step S7 and exits from the control flow, control is performed to issue a warning that there is a problem in starting the engine 1 using a notification means such as sound or display. You can.

Further, if the determination in step S1 or step S2 is NO, that is, the starter switch 46 is not operated, or the continuous operation of the starter switch 46 (instruction to drive the starter motor 40) is canceled. In this case, the start control is finished and the control flow shown in FIG. 9 is exited.

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

Note that when starting the engine 1, the above control flow is divided into two modes: one in which the occupant continuously operates the starter switch 46, and one in which the occupant temporarily operates the starter switch 46 (once the starter switch 46 is pressed once). It is possible to correspond to both types of operations (release type operation). In the case where the occupant temporarily operates the starter switch 46, it is determined in step S2 that a continuous drive instruction for the starter motor 40 is being given until a predetermined period of time has elapsed since the operation input to the starter switch 46. do.

As described above, in the engine 1 of the present embodiment, when the rotation of the crankshaft 14 is not detected even though the starter motor 40 is energized, the starter motor 40 is stopped and re-driven at least once. By performing these steps, the function of the decompression mechanism 4 can be restored, and the starter motor 40 can be reliably started without applying an excessive load. Since the starter motor 40 does not continue to be driven while the driving force of the starter motor 40 and the compression reaction force of the engine 1 are balanced, system damage may occur due to large current caused by driving the starter motor 40 for a long time. can be avoided. In addition, since the engine can be started with the decompression mechanism 4 functioning reliably, it is possible to select the starter motor 40 with the minimum necessary output and size, and it is possible to reduce the size and weight of the electrical system and the engine 1 as a whole. can.

Since driving of the starter motor 40 is automatically stopped and restarted up to a specified number of times under the control of the ECM 5, there is no need for the occupant to press the starter switch 46 again after stopping the driving of the starter motor 40, saving the trouble of complicated operations. You can definitely get the effect without using it.

Restoration of the function of the decompression mechanism 4 is realized with the reciprocating rotation of the crankshaft 14 (reciprocating movement from the decompression function position V3 to the torque balance position V2) caused by driving and stopping of the starter motor 40. Further, since no new parts are required to restore the function of the decompression mechanism 4, effects can be obtained with a simple configuration. That is, in terms of the configuration, it is sufficient that the angular position of the crankshaft 14 satisfies the requirement that the torque balance position V2 is closer to the compression top dead center V1 than the decompression function position V3. In addition, since the control is simple in that the drive of the starter motor 40 is turned on and off based on the rotational state of the crankshaft 14 detected by the crank angle sensor 19, the control burden is small and the control system is not required and is effective. can be obtained. Therefore, the startability of the engine 1 can be improved at low cost.

Note that in the above description, fluctuations in the torque of the starter motor 40 itself have been omitted, but the torque actually generated by the starter motor 40 is affected by the state of charge of the battery 35 that supplies power. Therefore, the above-mentioned positional relationship between the torque balance position V2 and the decompression function position V3 is set in consideration of the torque fluctuation of the starter motor 40 depending on the state of charge of the battery 35.

The present invention is not limited to the embodiments described above, and can be implemented with various modifications. In the embodiments described above, the configuration, control, etc. illustrated in the accompanying drawings are not limited to these, and can be modified as appropriate within the scope of achieving the effects of the present invention. Other changes can be made as appropriate without departing from the scope of the invention.

For example, in the above embodiment, the ECM 5 controls the energization of the starter motor 40 when starting the engine based on the detected value of the crank angle sensor 19, but the protection circuit of the battery 35 is used for similar energization control. It is also possible to use Specifically, a protection switch is provided inside the battery 35 to turn on/off energization of the starter motor 40 using a current value as a threshold, and a predetermined protection period (stop time) is set for driving the starter motor 40. When an instruction to start the engine is received, the starter motor 40 is energized from the battery 35, and if the current value exceeds the above threshold, it is determined that the decompression mechanism 4 is not functioning and proper cranking is not being performed. , the power supply from the battery 35 to the starter motor 40 is stopped. Then, after the above protection period (stop time) has elapsed, power supply from the battery 35 to the starter motor 40 is restarted to drive the starter motor 40 again.

As can be seen from this modification, in the present invention, the means for detecting and determining an engine starting error (failure to rotate the crankshaft even if the starter motor is driven) due to the decompression mechanism not functioning is as follows: It is not uniform and it is possible to use various detection means and determination means.

The internal combustion engine of the present invention is not limited to a vehicle engine. It is applicable to all internal combustion engines having a similar configuration, regardless of the purpose.

As explained above, the present invention has the effect of reliably functioning a decompression mechanism in an internal combustion engine to improve startability, and is particularly effective in internal combustion engines that are required to start reliably with a small and lightweight starter motor. It is useful for

1: Engine 2: Starter drive mechanism 3: Valve train 4: Decompression mechanism 14: Crankshaft 17: Combustion chamber 19: Crank angle sensor 22: Intake valve 23: Exhaust valve 32: Accelerator 33: Clutch cover 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 V1 : Compression top dead center V2 : Torque balance position V3 : Decompression Functional position

Claims (5)

a starter motor that transmits driving force to the crankshaft to start the internal combustion engine;
a decompression mechanism capable of a decompression operation that reduces the pressure in the combustion chamber by giving an opening to the exhaust valve at the time of startup;
At the time of starting, if the decompression mechanism does not function and the rotation of the crankshaft does not proceed due to the driving force of the starter motor, driving the starter motor again after a predetermined time after stopping the driving of the starter motor ;
The driving stop and the re-driving of the starter motor are automatically repeated, and each time the driving is stopped, a counter number is added to a counter indicating the number of driving stops of the starter motor, and the counter number of the counter reaches a specified value. The internal combustion engine is characterized in that, if the starter motor reaches the limit, the starter motor is not redriven any further . The position of the crankshaft at which the driving torque of the starter motor and the compression reaction force of the internal combustion engine are balanced when the decompression mechanism is not functioning is the position of the crankshaft when the decompression mechanism performs the decompression operation. The internal combustion engine according to claim 1, wherein the internal combustion engine is located closer to compression top dead center than the position of the engine. A crank angle sensor that detects rotation of the crankshaft is provided, and when rotation of the crankshaft is not detected by the crank angle sensor, the drive of the starter motor is stopped and the starter motor is driven again. 2. The internal combustion engine according to 1 or 2. Equipped with a starter switch operated by the passenger,
When the starter switch is temporarily operated, continuously instructing the starter motor to drive until a predetermined time period has elapsed since the operation input to the starter switch;
While the drive instruction is given, if the rotation of the crankshaft does not proceed due to the driving force of the starter motor, the stoppage of driving and the re-driving of the starter motor are automatically repeated. 3. The internal combustion engine according to any one of 3. The internal combustion engine according to any one of claims 1 to 4, further comprising a notification means for notifying when the counter number of the counter reaches the specified value.

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