Engine and straddled vehicle

Abstract

Provided are an engine and a straddled vehicle capable of precisely stopping a crankshaft at a position right before a maximum intake reaction force position while reducing supply power. This engine comprises a crankshaft, a motor generator, a power supply source, a control device, an exhaust valve, an exhaust valve spring, an intake valve, and an intake valve spring. The control device makes a supply power amount in a second half region between a maximum exhaust reaction force position and a maximum intake reaction force position on which a reaction force in a reverse rotation direction of an intake valve spring acts smaller than a supply power amount in a first half region, such that the crankshaft in normal rotation stops right before the maximum intake reaction force position by receiving the reaction force in the reverse rotation direction of the intake valve spring after passing through the maximum exhaust reaction force position.

Description

Engine and Straddled Vehicle

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

[0002] For example, Patent Document 1 discloses an engine unit that performs stop control to stop a crankshaft in either an expansion stroke or an exhaust stroke after the combustion operation of the engine stops. Patent Document 1 also discloses that the target region is preferably the expansion stroke of the engine.

[0003] Japanese Unexamined Patent Application Publication No. 2018-053772

[0004] An object of the present invention is to provide an engine and a straddle-type vehicle capable of accurately stopping a crankshaft at a position before the maximum intake reaction force position while reducing power supply.

[0005] For example, the control disclosed in Patent Document 1 attempts to stop the crankshaft in the expansion stroke by applying a braking force to the rotation of the crankshaft to a permanent magnet type rotating electric machine or changing the braking force while supplying current to the rotating electric machine.

[0006] However, in the expansion stroke of the engine after the combustion operation stops, the air in the cylinder compressed in the immediately preceding compression stroke is gradually released from the compression, and applies a force that promotes rotation to the crankshaft. Therefore, for the control of finally stopping the crankshaft at the target position, the rotating electric machine is required to be supplied with large electric power. Further, the magnitude of the force accompanying the release of the compressed air varies depending on the amount of the compressed air under the current situation. Even in a situation where the force generated by the compressed air is large, the rotating electric machine is required to be supplied with large electric power for the control of finally stopping the crankshaft at the target position.

[0007] The inventors have thoroughly investigated the precise stopping position of the crankshaft and the power to be supplied. As a result, the inventors have found that by controlling the amount of power supplied in the latter half region between the maximum exhaust reaction force position and the maximum intake reaction force position to be less than the amount of power supplied in the first half region, the crankshaft can be precisely stopped at the target position while reducing the power supply, so that the crankshaft stops before the maximum intake reaction force position, where the reaction force of the intake valve spring is at its maximum, after passing the maximum exhaust reaction force position where the reaction force of the exhaust valve spring is at its maximum. In the latter half region between the maximum exhaust reaction force position and the maximum intake reaction force position, deceleration can be achieved by receiving the reaction force in the reverse rotation direction of the intake valve spring, thus reducing the amount of power supplied compared to when the reaction force in the reverse rotation direction of the intake valve spring is not received. In addition, assuming that the reaction force of the intake valve spring in the reverse rotation direction is utilized in the latter half region, it is not necessary to stop the crankshaft in the first half region between the maximum exhaust reaction force position and the maximum intake reaction force position using only the supplied power, so the amount of power supplied in the first half region can be reduced compared to, for example, when stopping only in the first half region. By supplying power based on the assumption that the reaction force in the reverse direction of the intake valve spring is utilized, the crankshaft, which is rotating in the forward direction, can be stopped before the position of maximum intake reaction force after passing the position of maximum exhaust reaction force, due to the reaction force in the reverse direction of the intake valve spring, while reducing the power supply. The inventors have found that this allows the crankshaft to be precisely stopped before the position of maximum intake reaction force while reducing the power supply.

[0008] The engine according to the present invention, completed based on the above findings, has the following configuration: (1) A crankshaft that rotates in the forward direction during combustion operation; a motor generator connected to the crankshaft; a power supply source that supplies power to the motor generator; a control device electrically connected to the motor generator and which rotates in the forward direction, which is decelerated by the motor generator using the power from the power supply source and stopped at an arbitrary position; an exhaust valve spring that biases the exhaust valve in the closing direction; and an intake valve spring that biases the intake valve in the closing direction, wherein the crank angle position of the crankshaft where the reaction force of the exhaust valve spring is maximum is defined as the maximum exhaust reaction force position, and the crank angle position of the crankshaft where the reaction force of the intake valve spring is maximum is defined as the maximum intake reaction force position, and the multi-cylinder or single-cylinder engine is configured such that there is no maximum exhaust reaction force position or maximum intake reaction force position of another cylinder between the maximum exhaust reaction force position and the maximum intake reaction force position of one cylinder, and the control device is The amount of power supplied in the latter half region between the maximum exhaust reaction force position and the maximum intake reaction force position, where the reaction force of the intake valve spring acts in the reverse direction, is made smaller than the amount of power supplied in the first half region, so that the crankshaft, which is rotating in the forward direction, stops before the maximum intake reaction force position after passing the position of maximum exhaust reaction force, due to the reaction force of the intake valve spring in the reverse direction.

[0009] From the perspective of (1), in the latter half region between the position of maximum exhaust reaction force and the position of maximum intake reaction force, deceleration can be achieved by receiving the reaction force in the reverse direction of rotation of the intake valve spring, thus reducing the amount of power supplied compared to when the reaction force in the reverse direction of rotation of the intake valve spring is not received. In addition, since it is assumed that the reaction force of the intake valve spring in the reverse direction of rotation is utilized in the latter half region, it is not necessary to stop the crankshaft in the first half region between the position of maximum exhaust reaction force and the position of maximum intake reaction force using only the amount of power supplied, thus reducing the amount of power supplied in the first half region compared to when the crankshaft is stopped in the first half region only. By supplying power based on the assumption that the reaction force in the reverse direction of rotation of the intake valve spring is utilized, the crankshaft, which is rotating in the forward direction while reducing the supplied power, can be stopped before the position of maximum intake reaction force after passing the position of maximum exhaust reaction force by receiving the reaction force in the reverse direction of rotation of the intake valve spring. For this reason, the crankshaft can be precisely stopped before the position of maximum intake reaction force while reducing the supplied power.

[0010] According to one aspect of the present invention, the engine can adopt the following configuration: (2) The engine of (1), wherein the engine comprises the following intake valve drive mechanism (A) or (B) which reduces friction so as to suppress the reduction of the reaction force in the reverse direction of the intake valve spring received by the forward-rotating crankshaft after it has passed the position of maximum exhaust reaction force and before it reaches the position of maximum intake reaction force. (A) The intake valve drive mechanism includes a cam for opening and closing the intake valve, a rocker arm and a roller member provided on the rocker arm in a path that transmits force between the cam and the intake valve. (B) The intake valve drive mechanism includes a cam for opening and closing the intake valve and an intake valve lifter provided between the cam and the intake valve such that the displacement due to the rotational motion of the cam is transmitted linearly to the valve without passing through the rocker arm in a path that transmits force between the cam and the intake valve.

[0011] From the perspective of (2), an intake valve drive mechanism such as a rocker arm equipped with a roller member or an intake valve lifter that transmits force linearly reduces rotational frictional resistance compared to a case where neither a rocker arm equipped with a roller member nor a valve lifter is provided, so the reaction force in the reverse rotation direction of the intake valve spring can be utilized more effectively. As a result, the amount of power supplied can be reduced further. Note that the intake valve lifter includes, for example, a plate-shaped valve lifter shim inserted between the intake valve and the intake valve to finely adjust the opening of the intake valve. However, the intake valve lifter is not particularly limited, and for example, it does not have to include a valve lifter shim. Also, an intake valve drive mechanism consisting of a rocker arm without a roller member is not an intake valve drive mechanism of (2).

[0012] According to one aspect of the present invention, the engine may adopt the following configuration: (3) The engine of (1) or (2), wherein the engine comprises a plurality of intake valves and a plurality of intake valve springs such that the reduction in the reaction force in the reverse rotation direction of a plurality of intake valve springs received by the crankshaft, which is rotating in the forward direction, after it has passed the position of maximum exhaust reaction force and before it reaches the position of maximum intake reaction force.

[0013] From the perspective of (3), multiple intake valve springs allow for greater utilization of the reaction force in the reverse rotation direction of the intake valve springs. This allows for a further reduction in the amount of power supplied.

[0014] According to one aspect of the present invention, the engine can adopt the following configuration: (4) An engine according to any one of (1) to (3), wherein the control device, when the engine is warmed up, reduces the amount of power supplied in the latter half region between the position of maximum exhaust reaction force and the position of maximum intake reaction force, where the reaction force of the reverse rotation of the intake valve spring acts, to be less than the amount of power supplied in the first half region, such that the crankshaft, which is rotating in the forward direction, stops before the position of maximum intake reaction force after passing the position of maximum exhaust reaction force, due to the reaction force of the intake valve spring in the reverse rotation direction.

[0015] From the perspective of (4), when the engine is warmed up, there is less frictional loss in preventing the crankshaft from stopping before reaching the position of maximum intake reaction force. Therefore, the amount of power supplied can be reduced further.

[0016] According to one aspect of the present invention, the engine can adopt the following configuration: (5) An engine according to any one of (1) to (4), wherein the engine includes a cam for opening and closing the intake valve, and a rocker arm in a path for transmitting force between the cam and the intake valve, wherein the rocker arm is configured such that the friction parts of the engine are lubricated with a low viscosity oil with a low-temperature viscosity grade lower than 20W, such that the reduction in the reaction force in the reverse direction of the intake valve spring received by the forward-rotating crankshaft after it has passed the position of maximum exhaust reaction force and before it reaches the position of maximum intake reaction force is suppressed.

[0017] From the perspective of (5), the part that contacts the cam is configured so that the friction part of the engine is lubricated with low viscosity oil, resulting in less loss due to friction. Therefore, the amount of power supplied can be reduced further.

[0018] According to one aspect of the present invention, a saddle-type vehicle can adopt the following configuration: (6) A saddle-type vehicle, wherein the saddle-type vehicle is equipped with one of the engines (1) to (5), the crankshaft is arranged along the left-right direction of the body of the saddle-type vehicle, and the motor generator is provided at the right or left end of the crankshaft such that, after the crankshaft, which is rotating in the forward direction, passes the position of maximum exhaust reaction force, it receives a reaction force in the reverse direction of the intake valve spring and stops before the position of maximum intake reaction force, the amount of power supplied from the power source in the latter half region between the position of maximum exhaust reaction force and the position of maximum intake reaction force, where the reaction force in the reverse direction of the intake valve spring acts, is smaller than the amount of power supplied in the first half region.

[0019] From the perspective of (6), the displacement of the center position of the crankshaft and the center position of the motor generator due to the connection of gears and belts can be suppressed when viewed from the left or right. As a result, the space required for the power supply source and motor generator in a saddle-type vehicle can be made smaller. While making the saddle-type vehicle smaller and reducing power consumption, the crankshaft can be precisely stopped at a position before the position of maximum intake reaction force.

[0020] The technical terms used herein are intended to define only specific embodiments and are not intended to limit the invention. The terms “and / or” as used herein include any or all combinations of one or more related enumerated components. Where used herein, the use of the terms “including,” “comprising,” or “having,” and variations thereof, identifies the presence of described features, processes, operations, elements, components, and / or equivalents thereof, but may include one or more of the steps, operations, elements, components, and / or groups thereof. Where used herein, the terms “attached,” “connected,” “joined,” and / or equivalents thereof are used broadly and include both direct and indirect attachment, connection, and joining. Furthermore, “connected” and “joined” are not limited to physical or mechanical connection or joining, but may include direct or indirect electrical connection or joining. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as generally understood by those skilled in the art to whom the invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant technology and this disclosure, and not as ideal or overly formal unless expressly defined herein. It is understood that multiple technologies and processes are disclosed in this description of the invention. Each of these has its own distinct benefit, and each may be used in conjunction with one or more, or possibly all, of the other disclosed technologies. Therefore, for clarity, this description refrains from unnecessarily repeating all possible combinations of the individual steps. Nevertheless, the specification and claims should be read with the understanding that all such combinations are within the scope of the invention and claims. This specification describes a new engine and a saddle-type vehicle. The following description provides numerous specific details for illustrative purposes to provide a complete understanding of the invention.However, it will be apparent to those skilled in the art that the present invention can be carried out without these specific details. This disclosure should be considered illustrative of the present invention and is not intended to limit the invention to the specific embodiments shown by the following drawings or description.

[0021] The engine is an internal combustion engine. The engine can be multi-cylinder or single-cylinder. A multi-cylinder engine in which the maximum exhaust reaction force position or the maximum intake reaction force position of another cylinder lies between the maximum exhaust reaction force position and the maximum intake reaction force position of one cylinder is an engine in which the rotational angular phase difference between each cylinder is 180° or more. A multi-cylinder engine may be, for example, of the equal-spacing combustion type or the uneven-spacing combustion type. The engine is mounted, for example, in a saddle-type vehicle. However, the use of the engine is not particularly limited, and it may be mounted, for example, in an automobile, or in a vehicle including a ship. The engine may also be mounted, for example, in a work machine.

[0022] A motor generator has a motor function that drives the crankshaft and a function that generates electricity when driven by the crankshaft. A motor generator may also have a starter function that starts the engine by driving the crankshaft. A motor generator may be directly mounted on the crankshaft, or it may be connected to the crankshaft via a transmission mechanism such as gears. A motor generator can receive power and apply a driving force, i.e., a braking force, to the crankshaft in the reverse rotation direction. Furthermore, a motor generator is not particularly limited and may also receive power and apply a driving force to the crankshaft in the forward rotation direction.

[0023] The power source is, for example, a battery. However, the power source is not particularly limited; for example, it could be a capacitor, or a combination of a battery and a capacitor.

[0024] The control device includes, for example, a computer having a memory for storing a program and an arithmetic unit for executing the program. However, the structure of the control device is not particularly limited, and it may include, for example, logic circuits that do not have a program. The control device controls the motor generator. However, the functions of the control device are not particularly limited, and the control device may have, for example, a function to control engine combustion in addition to the function to control the motor generator. Furthermore, the control device may have a function to control other engine auxiliary equipment.

[0025] A saddle-type vehicle is a vehicle in which the driver sits straddling a saddle. Examples of saddle-type vehicles include motorcycles, three-wheeled vehicles, and ATVs (All-Terrain Vehicles). In saddle-type vehicles, the vehicle's posture is controlled by changes in the rider's posture. For this reason, saddle-type vehicles need to be lightweight and compact. For this reason, the power supply and motor generator mounted on a saddle-type vehicle also need to be lightweight and compact. If the power required to supply to the motor generator is small, the power supply source can be made lightweight and compact.

[0026] According to the present invention, an engine and a saddle-type vehicle can be realized that can precisely stop the crankshaft at a position before the position of maximum intake reaction force while reducing the power supply.

[0027] Figure 1 is a diagram illustrating an engine according to the first embodiment. Figure 2 is a schematic cross-sectional view showing a part of the first embodiment of the engine according to the first embodiment. Figure 3 is a configuration diagram showing a part of the second embodiment of the engine according to the first embodiment. Figure 4 is a plan view illustrating a saddle-type vehicle according to the second embodiment.

[0028] The engine and saddle-type vehicle according to the embodiments will be described below with reference to the drawings. It should be noted that the embodiments described below are merely examples. The present invention is not to be interpreted in any way as being limited by the embodiments and examples described below.

[0029] [First Embodiment] Figure 1 is a diagram illustrating an engine according to the first embodiment. Part (a) of Figure 1 is a block diagram showing the schematic configuration of the engine. Part (b) of Figure 1 is a flowchart illustrating the operation of the engine. Part (c) of Figure 1 is a chart showing the relationship between the reaction force of the valve springs and the crank speed with respect to the crank angle of the engine.

[0030] The engine 1 shown in Figure 1 is, for example, mounted on a vehicle and outputs power to drive the vehicle. The engine 1 is an internal combustion engine and outputs power by combustion. The engine 1 is a four-stroke engine. The engine 1 comprises a crankshaft 11, a motor generator 12, a power supply source 13, a control device 14, an exhaust valve 15, an exhaust valve spring 16, an intake valve 17, and an intake valve spring 18.

[0031] The crankshaft 11 rotates in the forward direction during the combustion operation of the engine 1. The engine 1 outputs power as the rotation of the crankshaft 11. The motor generator 12 is connected to the crankshaft 11. The motor generator 12 receives power and applies power to the crankshaft 11. The motor generator 12 generates electricity by receiving power from the crankshaft 11. For example, the motor generator 12 generates electricity by receiving power from the crankshaft 11 during the combustion operation of the engine 1. The motor generator 12 also drives the crankshaft 11 by receiving power. For example, the motor generator 12 drives the crankshaft 11 by receiving power when the engine 1 is started. Depending on the control, the motor generator 12 can receive power and apply driving force in either the forward or reverse rotation direction. The motor generator 12 can also apply a force in the opposite direction to the rotation, i.e., a braking force, by short-circuiting the windings. The power supply source 13 supplies power to the motor generator 12. The power supply source 13 is, for example, an energy storage device. The power supply source 13 supplies the stored power to the motor generator 12. The power supply source 13 is, for example, a battery or a capacitor.

[0032] The control device 14 controls the motor generator 12. The control device 14 is composed of, for example, a computer equipped with a central control unit (CPU) 14a that executes a program and a memory 14b that stores the program. The control device 14 performs control by having the central control unit 14a execute a control processing program stored in the memory 14b. The control device 14 is electrically connected to the motor generator 12. The control device 14 is electrically connected to the power supply source 13. The control device 14 controls the exchange of power between the motor generator 12 and the power supply source 13. The control device 14 includes, for example, an inverter including a switching transistor (not shown). In this way, the control device 14 controls the starting operation, power generation operation, and braking operation of the motor generator 12. After the combustion operation of the engine 1 stops, the control device 14 uses the power from the power supply source 13 to decelerate the forward rotation of the crankshaft 11, which is rotating in the forward direction, using the motor generator 12, and stops it at an arbitrary position.

[0033] The exhaust valve spring 16 biases the exhaust valve 15 in the closing direction. The intake valve spring 18 biases the intake valve 17 in the closing direction. The exhaust valve 15 opens by moving in a direction against the biasing force of the exhaust valve spring 16 due to the action of cams 26, 26a (see Figure 2), which will be described later. The exhaust valve 15 also closes by moving in the direction of the biasing force due to the biasing force of the exhaust valve spring 16. The intake valve 17 opens by moving in a direction against the biasing force of the intake valve spring 18 due to the action of cams 26, 26a, which will be described later. The intake valve 17 also closes by moving in the direction of the biasing force due to the biasing force of the intake valve spring 18. The cams 26, 26a that operate the exhaust valve 15 and the intake valve 17 rotate in conjunction with the crankshaft 11. More specifically, the cams 26, 26a rotate in response to the power of the crankshaft 11. Conversely, the biasing force of the exhaust valve spring 16 and the intake valve spring 18 influences the rotational force of the crankshaft 11 via the cams 26 and 26a. The biasing force of the exhaust valve spring 16 and the intake valve spring 18 act as reaction forces that accelerate or decelerate the crankshaft 11.

[0034] The chart in part (c) of Figure 1 shows the reaction forces of the valve springs with respect to the crank angle of engine 1. Fe is the reaction force from the exhaust valve spring 16. Fi is the reaction force from the intake valve spring 18. The horizontal axis of the chart shows the rotation angle of the crankshaft 11, and the numerical values ​​represent the rotation angle over four strokes, or two rotations. 0 (720) represents the crank angle at top dead center of compression for a four-stroke engine 1. The exhaust stroke E of engine 1 corresponds to a crank angle of approximately 180 to 360 degrees. The intake stroke I corresponds to a crank angle of approximately 360 to 540 degrees.

[0035] In the exhaust stroke E, the exhaust valve 15 opens. The exhaust valve 15 moves in a direction opposite to the biasing force of the exhaust valve spring 16, and the biasing force of the exhaust valve spring 16 affects the rotational force of the crankshaft 11. In other words, the crankshaft 11 rotates in a way that overcomes the force peak caused by the biasing force of the exhaust valve spring 16. The crank angle position of the crankshaft 11 at which the reaction force of the exhaust valve spring 16 is maximum is defined as the exhaust reaction force maximum position AEmax. In the exhaust stroke, at crank angles before the exhaust reaction force maximum position AEmax, the crankshaft 11 receives a force in the reverse rotation direction due to the biasing force. At crank angles after the exhaust reaction force maximum position AEmax, the crankshaft 11 receives a force in the forward rotation direction due to the biasing force. In the intake stroke I, the intake valve 17 opens. As the intake valve 17 moves in a direction opposite to the biasing force of the intake valve spring 18, the biasing force of the intake valve spring 18 affects the rotational force of the crankshaft 11. In other words, the crankshaft 11 rotates in a way that overcomes the force peak caused by the biasing force of the intake valve spring 18. The crank angle position of the crankshaft 11 at which the reaction force of the intake valve spring 18 is maximum is defined as the intake reaction force maximum position AImax. During the intake stroke, at crank angles before the intake reaction force maximum position AImax, the crankshaft 11 receives a force in the reverse rotation direction due to the biasing force. At crank angles after the intake reaction force maximum position AImax, the crankshaft 11 receives a force in the forward rotation direction due to the biasing force.

[0036] In this embodiment, the engine 1 is described as a single-cylinder engine. However, the engine 1 in this embodiment may have multiple cylinders. However, if the engine 1 has multiple cylinders, it is configured so that the maximum exhaust reaction force position or the maximum intake reaction force position of one cylinder does not lie between the maximum exhaust reaction force position and the maximum intake reaction force position of another cylinder.

[0037] The control device 14 controls the motor generator 12 so that the crankshaft 11, which is rotating in the forward direction, stops before the intake reaction force maximum position AImax after passing the exhaust reaction force maximum position AEmax, due to the reaction force in the reverse direction of the intake valve spring 18. The control device 14 makes the amount of power supplied Pb in the latter half of region Rb between the exhaust reaction force maximum position AEmax and the intake reaction force maximum position AImax, where the reaction force in the reverse direction of the intake valve spring 18 acts, smaller than the amount of power supplied Ia in the first half region Ra.

[0038] As shown in part (b) of Figure 1, the control device 14 acquires the crank angle and speed after the combustion operation of the engine 1 stops (S11). If the crankshaft 11 does not stop (No in S12), the control device 14 performs MG control (S13) on the motor generator 12. If the crankshaft 11 stops (Yes in S12), the control device 14 terminates the stop control. The control device 14 repeats the acquisition of crank angle and speed (S11) and the control of the motor generator 12 (S13) until it terminates the stop control for the motor generator 12. The control device 14 performs real-time feedback control based on the crank angle and speed. In MG control (S13), the control device 14 controls the motor generator 12 to output a force based on the acquired crank angle and speed. The control device 14 makes the amount of power supplied Pb in the latter half region Rb smaller than the amount of power supplied Ia in the first half region Ra.

[0039] The control device 14 controls the crankshaft 11 to apply a forward rotational force so that the crankshaft 11 overcomes the force peak caused by the exhaust valve spring 16 at a crank angle before the exhaust reaction force maximum position AEmax during the exhaust stroke. However, if the crank speed is greater than a predetermined value, for example, the control device 14 controls the crankshaft 11 to apply a force in the reverse rotational direction. Furthermore, if the crank speed is greater than a predetermined value that allows the crankshaft to stop in the target region, such as immediately after the end of combustion, the control device 14 controls the application of force to stop in subsequent cycles, or to apply a force in the rotational direction.

[0040] The control device 14 controls the crankshaft 11 to apply a force in the reverse direction to counteract the force in the forward direction when the crankshaft 11 descends the peak of force caused by the exhaust valve spring 16 during the exhaust stroke, at crank angles after the position of maximum exhaust reaction force AEmax. This suppresses the acceleration of the crankshaft 11 caused by the force in the forward direction from the exhaust valve spring 16 when the crankshaft 11 descends the peak of force caused by the exhaust valve spring 16. More specifically, the crankshaft 11 decelerates. In other words, in the first half region Ra, the crankshaft 11 decelerates regardless of the force in the forward direction from the reaction force of the exhaust valve spring 16. The crankshaft 11 may stop in the first half region Ra, or it may stop in the following second half region Rb.

[0041] In the latter half of region Rb, the control device 14 controls the motor generator 12 to apply a force to the crankshaft 11 in the reverse rotation direction. In the latter half of region Rb, as the crankshaft 11 overcomes the force peak caused by the intake valve spring 18, a force in the reverse rotation direction is applied to the crankshaft 11 due to the reaction force of the intake valve spring 18. In the latter half of region Rb, the crankshaft 11 decelerates and stops due to the reverse rotation force caused by the reaction force of the intake valve spring 18 and the reverse rotation force from the motor generator 12. In the latter half of region Rb, the control device 14 decelerates and stops the crankshaft 11 with a reduced amount of power supplied compared to the first half of region Ra.

[0042] According to this embodiment, in the latter half region Rb of the region R between the maximum exhaust reaction force position AEmax and the maximum intake reaction force position AImax, the crankshaft 11 can be decelerated by receiving the reaction force in the reverse rotation direction of the intake valve spring 18. Therefore, the amount of power supplied can be suppressed compared to the case where the intake valve spring 18 does not receive the reaction force in the reverse rotation direction. In addition, since it is assumed that the reaction force of the intake valve spring 18 in the reverse rotation direction is utilized in the latter half region Rb, in the first half region Ra between the maximum exhaust reaction force position AEmax and the maximum intake reaction force position AImax, it is not necessary to stop the system solely by the amount of power supplied. Therefore, the amount of power supplied in the first half region Ra can be suppressed compared to the case where the system is stopped only in the first half region Ra. By supplying power based on the assumption that the reaction force in the reverse rotation direction of the intake valve spring 18 is utilized, the power supply can be reduced, and the crankshaft 11, which is rotating in the forward direction, can be stopped before the intake reaction force maximum position AImax after passing the exhaust reaction force maximum position AEmax, by receiving the reaction force in the reverse rotation direction of the intake valve spring 18. Therefore, the power supply can be reduced, and the crankshaft 11 can be precisely stopped before the intake reaction force maximum position AImax.

[0043] In this embodiment, when the control device 14 controls the motor generator 12 to apply a force in the reverse rotation direction to the crankshaft 11 in the latter half region Rb, it can also employ a short-circuit brake by short-circuiting the windings of the motor generator 12. With a short-circuit brake, the supplied power is further reduced compared to when power is supplied to the motor generator 12 to generate a force in the reverse rotation direction. The control device 14 may make the amount of power supplied in the latter half region Rb even smaller than the amount of power supplied in the first half region Ra by making the period of short-circuit braking in the latter half region Rb longer than the period of short-circuit braking in the first half region Ra. Alternatively, the control device 14 may make the amount of power supplied in the latter half region Rb even smaller than the amount of power supplied in the first half region Ra by not performing a short-circuit brake in the first half region Ra and performing a short-circuit brake in the latter half region Rb.

[0044] After the crankshaft 11 decelerates and stops in the second half region Rb, the crankshaft 11 may rotate back in the reverse direction due to the reaction force of the intake valve spring 18 in the reverse rotation direction. This return in the reverse rotation direction can also occur when the engine stops while a short brake is being implemented.

[0045] [First Example] Figure 2 is a schematic cross-sectional view showing a part of the first example of the engine according to the first embodiment. Part (a) of Figure 2 shows an indirectly driven valve drive mechanism. Part (b) of Figure 2 shows a directly driven valve drive mechanism. Elements other than the valve drive mechanism in the engine of Figure 2 are the same as those in Figure 1, so the same reference numerals are assigned to the common elements, and the description thereof is omitted.

[0046] The intake valve drive mechanism 25 of the engine 1 is a mechanism for switching the intake valve 17 between an open state and a closed state. The indirectly driven intake valve drive mechanism 25 shown in part (a) of Figure 2 includes a cam 26, a rocker arm 27, and a roller member 28. The cam 26 rotates to open and close the intake valve 17. The rocker arm 27 and the roller member 28 are provided in the path that transmits force between the cam 26 and the intake valve 17. The roller member 28 is provided on the rocker arm 27. The exhaust valve drive mechanism 29 also has the same structure as the intake valve drive mechanism 25.

[0047] The cam 26 rotates in conjunction with the crankshaft 11 (Figure 1) to apply force to the roller member 28, which is a cam follower, and rotate the rocker arm 27. The rocker arm 27 rotates to move the intake valve 17 between an open position and a closed position. The intake valve spring 18 biases the intake valve 17 in a direction to move it to the closed position. The reaction force of the biasing by the intake valve spring 18 acts as a force for rotating the cam 26 via the rocker arm 27 and the roller member 28. This force affects the rotation of the crankshaft 11.

[0048] The intake valve drive mechanism 25 reduces friction so as to suppress a decrease in the reaction force in the reverse rotation direction of the intake valve spring 18, which is received before the maximum intake reaction force position AImax after the crankshaft 11 rotating in the forward direction passes the maximum exhaust reaction force position AEmax (FIG. 1). More specifically, since the cam driven member in contact with the cam 26 is a roller member 28, friction between the rotating cam 26 and the cam driven member is reduced. Friction between the cam driven member acts in a direction that suppresses transmission of the biasing force of the intake valve spring 18 to the cam 26. Since friction between the cam 26 and the cam driven member is reduced, a decrease in the reaction force in the reverse rotation direction of the intake valve spring 18, which is received before the maximum intake reaction force position AImax after the crankshaft 11 passes the maximum exhaust reaction force position AEmax (FIG. 1), is suppressed.

[0049] The direct-acting intake valve drive mechanism 35 shown in part (b) of FIG. 2 includes a cam 26a for opening and closing the intake valve 17, and an intake valve lifter 38 provided between the cam 26a and the intake valve 17. The cam 26a and the intake valve lifter 38 are provided such that displacement caused by the rotational motion of the cam 26a is linearly transmitted to the intake valve 17. The intake valve lifter 38 includes a valve lifter shim (not shown) for finely adjusting the opening degree of the intake valve 17. In the intake valve drive mechanism 35, displacement caused by the rotational motion of the cam 26a is linearly transmitted to the intake valve 17 without passing through the rocker arm 27 as shown in part (a) of FIG. 2. The exhaust valve drive mechanism 29 also has the same structure as the intake valve drive mechanism 25. The intake valve drive mechanism 35 shown in part (b) of FIG. 2 includes an exhaust cam 26b independent of the intake cam 26a.

[0050] As the cam 26a rotates in conjunction with the crankshaft 11 (Figure 1), the displacement of the cam 26 is transmitted linearly to the intake valve 17 via the intake valve lifter 38, which is a driven member. Because the displacement of the cam 26 is transmitted linearly, friction between the rotating cam 26a and the cam driven member is reduced. As friction between the cam 26a and the cam driven member is reduced, the decrease in the reaction force in the reverse rotation direction of the intake valve spring 18, which is received after the crankshaft 11 has passed the exhaust reaction force maximum position AEmax (Figure 1) but before reaching the intake reaction force maximum position AImax, is suppressed.

[0051] In this embodiment, the intake valve drive mechanisms 25 and 35, such as a rocker arm 27 or intake valve lifter 38 equipped with a roller member 28, reduce frictional resistance to the rotation of the crankshaft 11 compared to a case where, for example, a rocker arm 27 or intake valve lifter 38 equipped with a roller member is not provided. This allows for greater utilization of the reaction force of the intake valve spring 18 in the reverse rotation direction. As a result, the amount of power supplied can be further reduced.

[0052] [Second Embodiment] Figure 3 is a configuration diagram showing a part of a second embodiment of the engine according to the first embodiment. Figure 3 shows the structure around the valves in a view along the central axis of the engine cylinder. The engine 1 shown in Figure 3 is equipped with a plurality of intake valves 17a and a plurality of intake valve springs 18a. More specifically, the engine 1 is equipped with a plurality of intake valves 17a and a plurality of intake valve springs 18a so as to suppress the decrease in the reaction force in the reverse rotation direction of the plurality of intake valve springs 18a that the forward-rotating crankshaft 11 (Figure 1) receives after passing the exhaust reaction force maximum position AEmax (Figure 1) and before reaching the intake reaction force maximum position AImax. The engine 1 is also equipped with a plurality of exhaust valves 15a and a plurality of exhaust valve springs 16a. However, a configuration with a single exhaust valve is also possible. In the engine 1 shown in Figure 3, because there are a plurality of intake valve springs 18a, the reaction force in the reverse rotation direction of the crankshaft 11 (Figure 1) due to the biasing force of the intake valve springs 18a is large. Therefore, the reaction force in the reverse rotation direction of the crankshaft 11 can be utilized even more by the multiple intake valve springs 18a. As a result, the amount of power supplied can be reduced further.

[0053] [Third Embodiment] In the third embodiment of the engine according to the first embodiment, the control device 14 controls the motor generator 12 so that when the engine is warmed up, the crankshaft 11, which is rotating in the forward direction, passes the exhaust reaction force maximum position AEmax, and then receives the reaction force in the reverse direction of the intake valve spring 18 and stops before the intake reaction force maximum position AImax. More specifically, when the engine is warmed up, the control device 14 makes the amount of power supplied in the latter half region Rb between the exhaust reaction force maximum position AEmax and the intake reaction force maximum position AImax smaller than the amount of power supplied in the first half region Ra. The latter half region Rb is the region in which the reaction force in the reverse direction of the intake valve spring 18 acts.

[0054] According to this embodiment, when the engine 1 is warmed up, frictional losses are minimized so that the crankshaft 11 stops before the intake reaction force maximum position AImax. Therefore, the amount of power supplied can be further reduced.

[0055] [Fourth Embodiment] In the fourth embodiment of the engine according to the first embodiment, the engine 1 is equipped with a rocker arm 27 as shown in part (a) of Figure 2. In the fourth embodiment, the engine 1 is configured so that the contact parts of the engine 1 are lubricated with low viscosity oil. The low viscosity oil is a low viscosity oil with a low-temperature viscosity grade lower than 20W. By using low viscosity oil, the reduction in the reaction force in the reverse direction of the intake valve spring 18, which is received by the forward-rotating crankshaft 11 after passing the exhaust reaction force maximum position AEmax and before reaching the intake reaction force maximum position AImax, is suppressed. According to this embodiment, since the contact parts of the engine 1 that contact the cam 26 are lubricated with low viscosity oil, frictional losses are further reduced. Therefore, the amount of power supplied can be reduced even further.

[0056] [Fifth Embodiment] Figure 4 is a plan view illustrating a saddle-type vehicle according to the second embodiment.

[0057] The saddle-type vehicle 100 shown in Figure 4 is equipped with either the engine 1 described in the first embodiment or the engine 1 described in the first to fourth embodiments. The crankshaft 11 of the engine 1 is positioned along the left-right direction of the body of the saddle-type vehicle 100. The motor generator 12 is provided at the right end of the crankshaft 11. However, a configuration in which the motor generator 12 is provided at the left end of the crankshaft 11 is also possible. More specifically, the motor generator 12 is provided at the right or left end of the crankshaft 11 such that, after the forward-rotating crankshaft 11 has passed the exhaust reaction force maximum position AEmax, it receives the reaction force in the reverse rotation direction of the intake valve spring 18 and stops before the intake reaction force maximum position AImax. The motor generator 12 is positioned at the right or left end of the crankshaft 11 such that the amount of power supplied from the power supply source 13 in the latter half region Rb, where a reaction force in the reverse rotation direction from the intake valve spring 18 acts, is less than the amount of power supplied in the first half region Ra. According to this embodiment, the center position c of the crankshaft 11 and the center position c' of the motor generator 12 can be prevented from being misaligned due to the connection of gears and belts when viewed from the left or right. As a result, the space required for the power supply source 13 and the motor generator 12 in the saddle-type vehicle 100 can be made smaller. The saddle-type vehicle 100 can be made smaller and power consumption reduced, while the crankshaft 11 can be precisely stopped at a position before the intake reaction force maximum position AImax.

[0058] 1: Engine 11: Crankshaft 12: Motor generator 13: Power supply source 14: Control device 15, 15a: Exhaust valve 16, 16a: Exhaust valve spring 17, 17a: Intake valve 18, 18a: Intake valve spring 25, 35: Intake valve drive mechanism 26, 26a, 26b: Cam 27: Rocker arm 28: Roller member 38: Intake valve lifter 100: Saddle-type vehicle AEmax: Maximum exhaust reaction force position AImax: Maximum intake reaction force position Ra: First half region Rb: Second half region

Claims

1. A multi-cylinder or single-cylinder engine comprising: a crankshaft that rotates in the forward direction during combustion; a motor-generator connected to the crankshaft; a power supply source that supplies power to the motor-generator; a control device electrically connected to the motor-generator and using the power from the power supply source to decelerate the forward rotation of the crankshaft, which is rotating in the forward direction, and stop it at an arbitrary position; an exhaust valve spring that biases the exhaust valve in the closing direction; and an intake valve spring that biases the intake valve in the closing direction, wherein the crank angle position of the crankshaft where the reaction force of the exhaust valve spring is maximum is defined as the maximum exhaust reaction force position, and the crank angle position of the crankshaft where the reaction force of the intake valve spring is maximum is defined as the maximum intake reaction force position, wherein the multi-cylinder or single-cylinder engine is configured such that there is no maximum exhaust reaction force position or maximum intake reaction force position of another cylinder between the maximum exhaust reaction force position and the maximum intake reaction force position of one cylinder, and the control device is The amount of power supplied in the latter half region between the maximum exhaust reaction force position and the maximum intake reaction force position, where the reaction force of the intake valve spring acts in the reverse direction, is made smaller than the amount of power supplied in the first half region, so that the crankshaft, which is rotating in the forward direction, stops before the maximum intake reaction force position after passing the position of maximum exhaust reaction force, due to the reaction force of the intake valve spring in the reverse direction.

2. An engine according to claim 1, wherein the engine comprises an intake valve drive mechanism (A) or (B) below that reduces friction such that the reduction in the reaction force in the reverse direction of the intake valve spring received by the forward-rotating crankshaft after it has passed the position of maximum exhaust reaction force and before it reaches the position of maximum intake reaction force is suppressed. (A) The intake valve drive mechanism includes a cam for opening and closing the intake valve, a rocker arm and a roller member provided on the rocker arm in a path that transmits force between the cam and the intake valve. (B) The intake valve drive mechanism includes an intake valve lifter provided between the cam and the intake valve such that the displacement due to the rotational motion of the cam is transmitted linearly to the valve without passing through the rocker arm in a path that transmits force between the cam and the intake valve.

3. An engine according to claim 1 or 2, wherein the engine comprises a plurality of intake valves and a plurality of intake valve springs such that the reduction in the reaction force in the reverse rotation direction received by a plurality of intake valve springs after the crankshaft, which is rotating in the forward direction, has passed the position of maximum exhaust reaction force but before reaching the position of maximum intake reaction force is suppressed.

4. An engine according to any one of claims 1 to 3, wherein the control device, when the engine is warmed up, reduces the amount of power supplied in the latter half region between the position of maximum exhaust reaction force and the position of maximum intake reaction force, where the reaction force of the intake valve spring acts in the reverse direction, to be less than the amount of power supplied in the first half region, such that the crankshaft, which is rotating in the forward direction, stops before the position of maximum intake reaction force after passing the position of maximum exhaust reaction force, due to the reaction force of the intake valve spring in the reverse direction.

5. An engine according to any one of claims 1 to 4, wherein the engine includes a cam for opening and closing the intake valve, and a rocker arm in a path for transmitting force between the cam and the intake valve, wherein the contact portion of the rocker arm with the cam is lubricated with a low viscosity oil with a low-temperature viscosity grade lower than 20W, such that the reduction in the reverse rotational reaction force of the intake valve spring received by the forward-rotating crankshaft after it has passed the position of maximum exhaust reaction force and before it reaches the position of maximum intake reaction force is suppressed.

6. A saddle-type vehicle equipped with the engine described in any one of claims 1 to 5, wherein the crankshaft is arranged along the left-right direction of the body of the saddle-type vehicle, and the motor generator is provided at the right or left end of the crankshaft such that, after the crankshaft, which is rotating in the forward direction, has passed the position of maximum exhaust reaction force, it receives a reaction force in the reverse direction of the intake valve spring and stops before the position of maximum intake reaction force, the amount of power supplied from the power source in the latter half region between the position of maximum exhaust reaction force and the position of maximum intake reaction force, where the reaction force in the reverse direction of the intake valve spring acts, is smaller than the amount of power supplied in the first half region.

Images