WO2020141571A1

WO2020141571A1 - 4-stroke engine unit and straddle-type vehicle equipped with said engine unit

Info

Publication number: WO2020141571A1
Application number: PCT/JP2019/000022
Authority: WO
Inventors: 日野　陽至
Original assignee: ヤマハ発動機株式会社
Priority date: 2019-01-04
Filing date: 2019-01-04
Publication date: 2020-07-09
Also published as: WO2020141594A1; JPWO2020141594A1; JP7235771B2

Abstract

The purpose of the present invention is to provide a 4-stroke engine unit equipped with a starter generator, the size of which can be reduced in the axial direction of the crankshaft. This 4-stroke engine unit is equipped with: a load-variable 4-stroke engine configured in a manner such that the interior thereof is lubricated by a low-viscosity oil, the low-temperature viscosity grade of which is lower than 20W; a manual transmission lubricated by the low-viscosity oil; and a starter generator provided in a location which contacts the low-viscosity oil. The starter generator is equipped with: a stator having a stator core provided with a plurality of teeth provided in the circumferential direction with slots interposed therebetween, and also having a multi-phase stator winding wound around the teeth; and a rotor which has a permanent magnet having pole faces arranged in the circumferential direction so as to face the stator with an air gap interposed therebetween and present in a number which exceeds 2/3 the number of slots, is positioned so as to be coaxial with the crankshaft, and is not provided with a fan or fins for generating airflow for cooling.

Description

4-stroke engine unit and saddle-ride type vehicle equipped with the same engine unit

The present invention relates to a 4-stroke engine unit and a straddle-type vehicle equipped with the engine unit.

The motorcycle of Patent Document 1 is equipped with a 4-stroke engine. The engine unit includes a 4-stroke engine, a transmission, and a starter/generator.

Japanese Patent No. 5591778

The saddle-ride type vehicle is configured so that the posture of the vehicle is controlled by the weight shift of the driver while traveling. Therefore, from the viewpoint of operability and traveling performance, the straddle-type vehicle tends to be required to be small. In particular, a saddle-ride type vehicle as disclosed in Patent Document 1 is driven by a 4-stroke engine. Therefore, a straddle-type vehicle equipped with a 4-stroke engine may be strongly required to be small.

Also, in a saddle-type vehicle, the vehicle is relatively small, and the proportion of the engine in the entire vehicle is large. Therefore, the straddle-type vehicle itself can be effectively downsized by downsizing the 4-stroke engine. Therefore, how to downsize the 4-stroke engine is an important factor for a saddle-ride type vehicle equipped with the engine. In particular, the axial size of the crankshaft has a relatively large effect on the size of the vehicle. Therefore, how to reduce these sizes is more important. The axial direction of the crankshaft corresponds to, for example, the vehicle width direction of a saddle-ride type vehicle.

An object of the present invention is to provide a four-stroke engine equipped with a starter/generator capable of reducing the size of the crankshaft in the axial direction.

▽The starting generator has the functions of a starter motor and a generator. In a 4-stroke engine equipped with a starter/generator, the starter/generator needs to be maintained at an appropriate temperature during power generation. Therefore, the four-stroke engine equipped with the starter/generator has a cooling mechanism for cooling the starter/generator. Examples of the cooling mechanism include an oil cooler and a radiator. Since the cooling mechanism functions sufficiently, the temperature rise of the start-up generator is suppressed, which suppresses the evaporation of the lubricating oil in the engine.

Previously, there was a tendency for the cooling mechanism to become larger in order to obtain sufficient cooling mechanism performance. However, the present inventor has studied to suppress evaporation of the lubricating oil in the engine by the performance of the starting generator itself. As a result, the present inventor has found that if the starter/generator satisfies the condition that (the number of magnetic pole faces/the number of slots) is larger than 2/3, even if the starter/generator is placed in contact with the lubricating oil, It has been found that the evaporation of lubricating oil can be suppressed. When the condition that the number of magnetic pole faces/the number of slots of the starting generator is larger than 2/3 is satisfied, the generated current can be suppressed by a large impedance in the rotation region used as the generator. Therefore, in such a starter-generator, the temperature of the stator winding does not become higher than the temperature of the lubricating oil or does not easily become higher than that of the lubricating oil. Can be suppressed. Conventionally, it was considered that the cooling mechanism had to be large when the start-up generator was placed in an environment where it came into contact with the lubricating oil. However, based on the above-mentioned knowledge, it is possible to arrange the starter-generator in an environment where it comes into contact with the lubricating oil while suppressing or avoiding an increase in the size of the cooling mechanism.

Furthermore, the present inventor uses a lubricating oil having a low temperature viscosity grade lower than 20 W (hereinafter, also referred to as a low viscosity oil) to reduce or omit stirring of the lubricating oil by a starting generator for cooling. I found it. As a result, not only the energy loss due to the decrease in viscosity but also the energy loss of the starting generator due to the agitation of the lubricating oil can be reduced. That is, the resistance to rotation of the starting generator can be reduced. As a result, the starter generator can be further downsized.

In order to achieve the above object, according to one aspect of the present invention, a 4-stroke engine unit has the following configuration.

(1) A 4-stroke engine unit,
The 4-stroke engine unit is
A crankcase configured to be internally lubricated with a low-viscosity oil having a low-temperature viscosity grade lower than 20 W; and a crankshaft rotatably supported by the crankcase, wherein the crankcase is rotatably supported during four strokes. A load fluctuation type four-stroke engine having a high load region in which a load for rotating a crankshaft is large, and a low load region in which a load for rotating the crankshaft is smaller than a load in the high load region,
A transmission that is provided in the crankcase so as to be lubricated by the low-viscosity oil, and that transmits the driving force from the crankshaft;
A stator core having a plurality of teeth provided with slots formed in the circumferential direction, and a stator having windings of a plurality of phases wound around the teeth, and the circumferential direction so as to face the stator with a gap. Rotors having permanent magnet portions arranged in parallel with each other and having magnetic pole surfaces greater than 2/3 of the number of slots, arranged coaxially with the crankshaft, and having no fan or fin for generating an air flow for cooling. And a starting generator provided at a position in contact with the low-viscosity oil.

The engine unit (1) includes a load-changing four-stroke engine, a manual transmission, and a starting generator.
The load fluctuation type four-stroke engine has a crankcase configured to be internally lubricated with low-viscosity oil having a low temperature viscosity grade lower than 20 W, and a crankshaft rotatably supported by the crankcase.
The manual transmission is provided in the crankcase so as to be lubricated by the low-viscosity oil, and the driving force from the crankshaft is transmitted to the manual transmission.
The start generator includes a stator and a rotor. The stator has a stator core and a plurality of phases of stator windings. The stator core includes a plurality of tooth portions provided with slots in the circumferential direction. The multi-phase stator winding is wound around the teeth. The rotor has a permanent magnet section. The permanent magnet portion is arranged in the circumferential direction so as to face the stator with a gap, and has a magnetic pole surface larger than 2/3 of the number of slots. The rotor is fixed to the crankshaft and does not have fans or fins that generate the airflow for cooling. The starting generator is provided at a position in contact with the low viscosity oil.

According to the configuration of (1), the starter generator satisfies the condition that (pole face/number of slots) is more than 2/3. Therefore, the temperature of the stator winding does not become higher than the temperature of the low-viscosity oil or does not easily become higher. Thereby, even if the starting generator is arranged so as to come into contact with the low-viscosity oil, the evaporation of the low-viscosity oil can be suppressed. Therefore, the starter generator can be arranged in an environment where it comes into contact with the low-viscosity oil. Therefore, the start-up generator can suppress or avoid an increase in the size of the cooling mechanism. Therefore, the size of the crankshaft in the axial direction can be reduced.

According to the configuration of (1), since the low-viscosity oil whose low-temperature viscosity grade is lower than 20 W is used, it is possible to reduce the stirring of the low-viscosity oil by the starting generator for cooling. As a result, not only the energy loss associated with the decrease in viscosity but also the energy loss associated with stirring can be reduced. Therefore, it is possible to reduce the resistance against the rotation of the starting generator. As a result, the starter generator can be further downsized.

According to one aspect of the invention, the four-stroke engine unit can employ the following configurations.
(2) The four-stroke engine unit of (1),
The load fluctuation type four-stroke engine has a cylinder connected to the crankcase,
The rotor of the starter-generator has a bottomed tubular shape connected to the crankshaft between the stator and the cylinder in the axial direction in which the crankshaft extends.

According to the configuration of (2), the crankshaft of the load-changing four-stroke engine can be shortened as compared with, for example, a configuration in which the rotor of the starter generator is opened toward the cylinder in the axial direction. Therefore, the starter generator can be further downsized.

According to one aspect of the invention, the four-stroke engine unit can employ the following configurations.
(3) The four-stroke engine unit of (2),
A rotor, which is supported by the crankcase so as to be fixed in position in the crankcase in the space in which the starter-generator is housed, and outputs a signal indicating detection of the position of the rotor. A position detection device is further provided.

According to the configuration of (3), the rotor position detecting device outputs a signal indicating detection of the position of the rotor of the starting generator. The starter generator has a stator winding that does not rise above the temperature of the low viscosity oil. Therefore, as the configuration of the rotor position detecting device, for example, either a Hall IC with a relatively low upper limit operating temperature or a pickup coil with a relatively low upper limit operating temperature can be adopted. Therefore, the degree of freedom in design is high.

According to one aspect of the invention, a straddle-type vehicle can employ the following configurations.
(4) A straddle-type vehicle,
The saddle-ride type vehicle includes any one of the four-stroke engine units (1) to (3).

According to the configuration of (4), the saddle riding type vehicle can be downsized in the axial direction of the crankshaft by including any one of the four-stroke engine units of (1) to (3).

The terminology used herein is for the purpose of defining particular embodiments only and is not intended to limit the invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed components. As used herein, the use of the terms "including," "comprising," or "having" and variations thereof refers to the described feature, step, operation, It identifies the presence of elements, components and/or their equivalents, but can include one or more of steps, acts, elements, components, and/or groups thereof. As used herein, the terms “attached”, “connected”, “coupled” and/or their equivalents are widely used and refer to both direct and indirect attachment, connection and Includes both bindings. Furthermore, "connected" and "coupled" are not limited to physical or mechanical connections or couplings, but can include direct or indirect electrical connections or couplings. Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as commonly used dictionary-defined terms should be construed to have a meaning consistent with the meaning in the context of the relevant technology and this disclosure and are expressly defined herein. Unless stated otherwise, it should not be interpreted in the ideal or overly formal sense. In describing the present invention, it is understood that numerous techniques and steps have been disclosed. Each of these has individual benefits, and each may also be used with one or more, and possibly all, of the other disclosed techniques. Therefore, for the sake of clarity, this description refrains from unnecessarily repeating all possible combinations of individual steps. Nevertheless, the specification and claims should be read with the understanding that all such combinations are within the scope of this invention and claims.

In this specification, a new 4-stroke engine unit will be described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. This disclosure is to be considered as illustrative of the invention and is not intended to limit the invention to the particular embodiments illustrated by the following drawings or description.

The load fluctuation type four-stroke engine has a high load region and a low load region during four strokes. The load fluctuation type four-stroke engine is, for example, a single cylinder engine, a two-cylinder engine, a non-equidistant explosion three-cylinder engine, or a non-equidistant explosion four-cylinder engine. The load fluctuation type four-stroke engine is, for example, an engine having less than three cylinders. In one embodiment of the present disclosure, the load variation 4-stroke engine is, for example, a single-cylinder engine or a 2-cylinder engine. The two-cylinder engine may be a non-equidistant combustion engine having two cylinders. An example of a nonuniform combustion engine having two cylinders is a V-type engine.
The load fluctuation type 4-stroke engine has a large fluctuation in rotation at a low rotation speed as compared with other types of engines. The high load region is a region where the load torque is higher than the average value of the load torque in one combustion cycle in one combustion cycle of the engine. The low load region refers to a region other than the high load region in one combustion cycle. In the engine, the low load region is wider than the high load region, for example, when viewed from the rotation angle of the crankshaft. The compression stroke has an overlap with the high load area. It should be noted that in the present specification, the directions shown with respect to the load fluctuation type 4-stroke engine are shown with reference to a saddle type vehicle equipped with the load fluctuation type 4 stroke engine.

▽The starter generator is a rotating electric machine that can both start the engine and generate electricity. The starting generator may be, for example, an outer rotor type or an inner rotor type. Further, the starting generator may be an axial gap type instead of the radial gap type. According to one embodiment, in a starter generator, the rotor comprises permanent magnets. The start-up generator is, for example, a surface magnet type (SPM type) in which a magnetic pole portion of a rotor is exposed from a magnetic material. The starter generator is not limited to this, and may be, for example, an embedded magnet type (IPM type) in which the magnetic pole portion of the rotor is embedded in a magnetic material. The (pole surface/number of slots) is not particularly limited as long as it is larger than 2/3. As an upper limit value of (magnetic pole surface/number of slots), for example, 4/3 can be mentioned. In an example according to the present disclosure, the ratio is 8/9 or more. In an example according to the present disclosure, the ratio is 1/1 or more. In one example according to the present disclosure, the ratio is greater than 1/1. In one example according to the present disclosure, the ratio is 4/3. Note that some of the slots of the stator may not be formed because the control board or the like is installed on the stator. In such a case, the number of slots may be determined assuming that the slots are provided at the positions where the slots should originally be provided. The same applies to the number of magnetic poles of the flywheel. That is, when the 4:3 series of magnetic poles and slots are arranged such that the number of magnetic poles and the number of slots substantially satisfy the relationship of 4:3, (the magnetic pole surface/the number of slots) is 4/3. I can say.

The crankcase is a case that houses at least the crankcase of the 4-stroke engine unit. The crankcase is connected to the cylinder. The crankcase houses the manual transmission. The crankcase houses, for example, a starting generator. In this case, the crankcase also includes the starting generator cover and the starting generator housing space. However, the starting generator may be housed only in the crankcase.

The rotor position detection device is a device that detects the position of the rotor of the starting generator. For example, a Hall IC is used as the rotor position detecting device. However, for example, a pickup may be used as the rotor position detecting device. When the rotor position detecting device is arranged in the starting generator housing space, the rotor position detecting device is attached to the crankcase. The rotor position detecting device is attached to, for example, a crank generator starter generator cover. When the rotor position detecting device is arranged in the starter generator housing space, the rotor position detecting device may be attached to the stator, for example.

A straddle vehicle is a vehicle in which the driver sits across the saddle. Examples of the saddle riding type vehicle include a scooter type, a moped type, an off-road type and an on-road type motorcycle. Further, the saddle-ride type vehicle is not limited to a motorcycle, and may be, for example, a motorcycle, an ATV (All-Terrain Vehicle), or the like. The motorcycle may include two front wheels and one rear wheel, or may include one front wheel and two rear wheels. The drive wheels of the saddle type vehicle may be rear wheels or front wheels. Further, the drive wheels of the saddle riding type vehicle may be both rear wheels and front wheels.

Also, it is preferable that the straddle-type vehicle is configured to be able to turn in a lean posture. A straddle-type vehicle configured to be able to turn in a lean posture is configured to turn in a posture tilted inward of a curve. As a result, the straddle-type vehicle configured to be able to turn in the lean posture opposes the centrifugal force applied to the straddle-type vehicle at the time of turning. In a saddle-ride type vehicle that is configured to be able to turn in a lean posture, lightness is required, and therefore responsiveness of progress to a start operation is important. In a straddle-type vehicle that is configured to be able to turn in a lean posture, for example, a torque converter that utilizes the mechanical action of fluid is not provided in the power transmission path from the power source to the drive wheels.

According to the present invention, it is possible to realize a four-stroke engine unit including a starter/generator capable of reducing the size of the crankshaft in the axial direction.

It is a sectional view showing composition of a 4-stroke engine unit concerning one embodiment of the present invention. It is a side view of the 4-stroke engine unit shown in FIG. It is sectional drawing which shows the cross section perpendicular|vertical to the rotating shaft line of the starter generator shown in FIG. (A) is an explanatory view which shows typically the drive characteristic of a starting generator. (B) is an explanatory view schematically showing power generation characteristics. FIG. 2 is a side view of a saddle-ride type vehicle equipped with the 4-stroke engine unit of FIG. 1.

Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a configuration of a 4-stroke engine unit according to an embodiment of the present invention. The four-stroke engine unit 10 of FIG. 1 includes a load-changing four-stroke engine 20, a manual transmission 30, and a starter/generator 60. Note that, hereinafter, the load fluctuation type 4-stroke engine 20 is also referred to as the 4-stroke engine 20.
The 4-stroke engine 20 has a crankcase 21 and a crankshaft 24. The crankcase 21 is configured such that the inside thereof is lubricated with the low-viscosity oil OL. The crankshaft 24 is rotatably supported by the crankcase. The 4-stroke engine 20 outputs the power generated by the combustion of gas as the torque and the rotation speed of the crankshaft 24. The four-stroke engine 20 has a high load region in which the load that rotates the crankshaft 24 is large and a low load region in which the load that rotates the crankshaft is smaller than the load in the high load region during four strokes. In the present embodiment, the low-viscosity oil OL is a lubricating oil whose low-temperature viscosity grade according to SAE viscosity classification is lower than 20W. The low-viscosity oil OL is stored in a part of the crankcase 21.

The manual transmission 30 is provided in the crankcase 21 of the 4-stroke engine 20 so as to be lubricated by the low viscosity oil OL. A manual clutch 40 is provided between the crankshaft 24 of the four-stroke engine 20 and the manual transmission 30. The manual clutch 40 engages and disengages the power transmitted between the 4-stroke engine 20 and the manual transmission 30.

The starter/generator 60 includes a stator 62 and a rotor 61. The stator 62 has a stator core 621 having a plurality of teeth 623 provided with slots formed in the circumferential direction, and a plurality of phases of stator windings 622 wound around the teeth 623. The rotor 61 has a permanent magnet portion 614 which is arranged in the circumferential direction so as to face the stator 62 with a gap and has a magnetic pole surface of 4/3 of the number of slots. That is, the rotor 61 has the permanent magnet portion 614 having a magnetic pole surface larger than 2/3 of the number of slots. The rotor 61 is arranged coaxially with the crankshaft 24. The rotor 61 does not include a fan or fin that generates an air flow for cooling. The starter generator 60 is provided at a position in contact with the low viscosity oil OL. The start-up generator 60 receives the supply of electric power and drives the 4-stroke engine 20. The starter generator 60 is driven by the 4-stroke engine 20 via the crankshaft 24 to generate electric power.

FIG. 2 is a side view of the 4-stroke engine unit 10 shown in FIG. Hereinafter, the 4-stroke engine unit 10 will be described in more detail with reference to FIGS. 1 and 2.
The 4-stroke engine 20 of the 4-stroke engine unit 10 includes a crankcase 21, a cylinder 22, a piston 26, a connecting rod 25, and a crankshaft 24.
The piston 26 is provided in the cylinder 22 so as to be capable of reciprocating. The crankshaft 24 is rotatably provided in the crankcase 21. The connecting rod 25 connects the piston 26 and the crankshaft 24. A cylinder head 23 is attached to the top of the cylinder 22. A combustion chamber is formed by the cylinder 22, the cylinder head 23, and the piston 26.
The crankshaft 24 is rotatably supported by the crankcase 21 via a pair of bearings 242. The crankshaft 24 is provided with a starting generator 60 and a drive gear 241 for transmitting power to the manual clutch 40. The starter-generator 60 is mounted in the first direction of the crankshaft 24 when viewed in the direction of the rotation axis of the crankshaft 24. The drive gear 241 is mounted in the second direction of the crankshaft 24 when viewed in the direction of the rotation axis of the crankshaft 24.

The four-stroke engine 20 is provided with a throttle valve SV, a fuel injection device FI, and a spark plug 27. The throttle valve SV regulates the amount of air supplied to the combustion chamber. The fuel injection device FI supplies the fuel to the air supplied to the combustion chamber by the throttle valve SV by injecting the fuel. A mixed gas of fuel and air is supplied to the combustion chamber. The spark plug 27 burns a mixed gas of air and fuel supplied to the combustion chamber.

The 4-stroke engine 20 is an internal combustion engine. The 4-stroke engine 20 is supplied with fuel. The 4-stroke engine 20 outputs rotational power by a combustion operation that burns fuel. The driver adjusts the rotational power output from the 4-stroke engine 20 by operating an accelerator grip (not shown). The 4-stroke engine 20 outputs rotational power via the crankshaft 24. The rotational power of the crankshaft 24 is transmitted to the manual transmission 30 via the manual clutch 40.

The four-stroke engine 20 has a high load region where the load that rotates the crankshaft 24 is large and a low load region where the load that rotates the crankshaft 24 is smaller than the load in the high load region during four strokes. From the viewpoint of the rotation angle of the crankshaft 24, the low load region is wider than the high load region. More specifically, the four-stroke engine 20 rotates forward while repeating four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The compression stroke is included in the high load area and is not included in the low load area.

The 4-stroke engine 20 includes a camshaft 28, an intake valve 29a, an exhaust valve 29b, and a cam chain 281. The cam chain 281 is driven by the crankshaft 24 and rotates the camshaft 28. The cam shaft 28 has a plurality of cams. Each cam of the cam shaft 28 rotates to directly or indirectly move the intake valve 29a and the exhaust valve 29b up and down. More specifically, the crankshaft 24 drives the camshaft 28 and the cam chain 281 so as to lower the intake valve 29a in the intake stroke of the four-stroke engine 20 and lower the exhaust valve 29b in the exhaust stroke. Let The cam chain 281 is housed in a cam chain housing portion 282 formed in the crankcase 21, the cylinder 22, and the cylinder head 23.

The 4-stroke engine 20 includes an oil pan 211 below the crankcase 21. The oil pan 211 stores low-viscosity oil OL that lubricates the operation of the 4-stroke engine 20. The low viscosity oil OL accumulated in the oil pan 211 is pressurized by an oil pump (not shown). The pressurized low viscosity oil OL is supplied to the piston 26 and the crankshaft 24 via an oil supply passage (not shown). Such an oil supply passage is formed by, for example, a hole provided inside the crankshaft 24, a hole provided inside the cylinder 22, and a groove formed at the joint surface between the cylinder 22 and the cylinder head 23. It A part of the low-viscosity oil OL is supplied to the cam chain storage portion 282. The low-viscosity oil OL supplied to the cam chain housing portion 282 is also supplied to the cam shaft 28 and the valve 29 via the cam chain 281. In this way, the interior of the 4-stroke engine 20 is lubricated with the low-viscosity oil OL. Therefore, the inside of the crankcase 21 is lubricated with the low viscosity oil OL.

Low-viscosity oil OL is a low-viscosity oil whose low-temperature viscosity grade according to the SAE viscosity classification specified in SAE J300 is lower than 20W. The lower the viscosity grade, the lower the viscosity of the oil. The high temperature viscosity grade according to the SAE viscosity classification of the lubricating oil is not particularly limited. When X is an integer of 0 or more and less than 20 and Y is an integer of 0 or more, the SAE viscosity grade of the lubricating oil is represented by XW-Y. Lubricating oil is composed of base oil and additives. Roughly speaking, the lower the viscosity of the lubricating oil, the lower the evaporation temperature of the lubricating oil and the easier it is to evaporate. Depending on the type of base oil (for example, mineral oil or synthetic oil) and additives, the evaporation temperature may differ even if the lubricating oil has the same viscosity. The evaporation characteristics of the lubricating oil can be obtained, for example, by a boiling point distribution measurement method by gas chromatography simulated distillation according to ASTM D6352.

The manual clutch 40 includes a clutch housing 41, a friction plate 42, a clutch plate 43, a clutch boss 44, and a pressure plate 45. A driven gear 411 is provided in the clutch housing 41. The driving force from the crankshaft 24 is transmitted to the clutch housing 41 via a driving gear 241 and a driven gear 411 provided on the crankshaft 24. The friction plate 42 is arranged on the inner circumference of the clutch housing 41. The friction plate 42 engages with the clutch housing 41 and rotates together with the clutch housing 41. The clutch boss 44 is attached to the input shaft 32 of the manual transmission 30 so as to rotate integrally with the input shaft 32 of the manual transmission 30. The rotation axis of the clutch boss 44 and the rotation axis of the clutch housing 41 are substantially coincident with each other. The clutch plate 43 is arranged on the outer periphery of the clutch boss 44. The clutch plate 43 engages with the clutch boss 44 and rotates together with the clutch boss 44.

The pressure plate 45 is connected to the lifter rod 38 that penetrates the central axis of the input shaft of the manual transmission 30. The pressure plate 45 brings the friction plate 42 and the clutch plate 43 into close contact with and away from each other by the operation of the driver. More specifically, the driver operates the clutch lever (not shown) to displace the lifter rod 38 in the direction of the central axis via the wire (not shown) and the clutch arm 37. The pressure plate 45 is integrated with the lifter rod 38 and is displaced in the direction of the central axis of the lifter rod 38 to bring the friction plate 42 and the clutch plate 43 into close contact with or apart from each other. When the driver brings the friction plate 42 and the clutch plate 43 into close contact with each other with the pressure plate 45, the driving force of the four-stroke engine 20 is transmitted to the manual transmission 30. When the driver separates the friction plate 42 from the clutch plate 43 with the pressure plate 45, the driving force of the four-stroke engine 20 is disconnected from the manual transmission 30.

The manual transmission 30 is provided inside the crankcase 21. The manual transmission 30 is connected to the manual clutch 40. The manual transmission 30 has a plurality of shift speeds. The manual transmission 30 has an input shaft 32, an output shaft 33, a driving gear 34, a driven gear 35, and a gear stage setting mechanism 36. The input shaft 32 is rotatably arranged. The power output from the 4-stroke engine 20 is input to the input shaft 32 via the manual clutch 40. The manual transmission 30 changes the rotational speed of the output shaft 33 with respect to the input shaft 32 in a stepwise manner.

The output shaft 33 is rotatably arranged on an axis parallel to the input shaft 32. The plurality of drive gears 34 are provided on the input shaft 32 and are configured to always rotate together with the input shaft 32. Further, each of the plurality of drive gears 34 corresponds to each shift speed. The plurality of driven gears 35 are provided on the output shaft 33 and are configured to be rotatable relative to the output shaft 33. The plurality of driven gears 35 are configured to be able to mesh with the corresponding drive gears 34. At least one of the plurality of driven gears 35 always meshes with the drive gear 34.
Specifically, the plurality of drive gears 34 included in the manual transmission 30 shown in FIG. 1 are configured so as to always rotate together with the input shaft 32. Further, the plurality of driven gears 35 are configured to be rotatable relative to the output shaft 33. Further, each of the plurality of driven gears 35 always meshes with the driving gear 34.

The low viscosity oil OL is also supplied to the manual transmission 30. More specifically, the manual transmission 30 is partially immersed in the low viscosity oil OL stored in the oil pan 211. The low viscosity oil OL supplied to the piston 26 also flows to the manual transmission 30. The low-viscosity oil OL is agitated by the rotation of the manual transmission 30 and diffuses into the crankcase 21. As a result, the low-viscosity oil OL is supplied to the entire manual transmission 30.

FIG. 3 is a cross-sectional view showing a cross section perpendicular to the rotation axis of the starting generator 60 shown in FIG. The starting generator 60 will be described with reference to FIGS. 1 and 3. The starter generator 60 is a permanent magnet type three-phase brushless motor. The starter generator 60 also functions as a permanent magnet type three-phase brushless generator. The starter-generator 60 has a stator 62 whose position is fixed with respect to the crankcase 21 and a permanent magnet facing the stator 62 with a gap therebetween, and is provided on the crankshaft 24 so as to interlock with the rotation of the crankshaft 24. And a fixed rotor. The start-up generator 60 of this embodiment is a radial gap type. The starter generator 60 is an outer rotor type. That is, the rotor 61 is an outer rotor. The stator 62 is an inner stator. The starter/generator 60 is housed in a starter/generator housing portion 65 formed by the starter/generator cover 64 and the crankcase 21. The space of the starter generator storage portion 65 communicates with the space of the cam chain storage portion 282.

The rotor 61 has a rotor body 615. The rotor body 615 is made of, for example, a ferromagnetic material. The rotor body 615 has a bottomed tubular shape. The rotor body 615 has a cylindrical boss 615a, a disc-shaped bottom wall 615b, and a cylindrical back yoke 615c. The bottom wall portion 615b and the back yoke portion 615c are integrally formed. The bottom wall portion 615b and the back yoke portion 615c are fixed to the crankshaft 24 via a cylindrical boss portion 615a. The rotor 61 is not provided with a winding to which current is supplied.
The rotor 61 has a bottomed tubular shape connected to the crankshaft 24 between the stator 62 and the cylinder (cylinder 22) of the four-stroke engine 20 in the axial direction in which the crankshaft 24 extends. That is, the disc-shaped bottom wall portion 615b is provided in the direction of the cylinder 22 rather than the tubular back yoke portion 615c in the axial direction in which the crankshaft 24 extends.
The rotor 61 has a permanent magnet portion 614. The rotor 61 has a plurality of magnetic pole portions 616. The plurality of magnetic pole portions 616 are formed by the permanent magnet portion 614. The plurality of magnetic pole portions 616 are provided on the inner peripheral surface of the back yoke portion 615c. In the present embodiment, the permanent magnet section 614 has a plurality of permanent magnets. The plurality of magnetic pole portions 616 are provided in each of the plurality of permanent magnets.
In the present embodiment, the permanent magnet part 614 of the start-up generator 60 is designed to have a large thickness to increase the permeance coefficient. By increasing the permeance coefficient, the permanent magnet part 614 has robustness against demagnetization.

The plurality of magnetic pole portions 616 are provided such that the N poles and the S poles are alternately arranged in the circumferential direction of the starting generator 60. In the present embodiment, the rotor 61 facing the stator 62 has 24 magnetic poles. The number of magnetic poles of the rotor 61 refers to the number of magnetic poles facing the stator 62. No magnetic material is provided between the magnetic pole portion 616 and the stator 62.
The magnetic pole portion 616 is provided outside the stator 62 in the radial direction of the starting generator 60. The back yoke portion 615c is provided outside the magnetic pole portion 616 in the radial direction. The start-up generator 60 has more magnetic poles 616 than the number of teeth 623. In the present embodiment, the rotor 61 is a surface magnet type (SPM type) in which the magnetic pole portion 616 is exposed from the magnetic material.

The position of the stator 62 is fixed with respect to the crankcase 21. The stator 62 has a stator core 621 and a plurality of stator windings 622. The stator core 621 has a plurality of tooth portions 623 provided at intervals in the circumferential direction. The plurality of tooth portions 623 integrally extend from the stator core 621 outward in the radial direction. In the present embodiment, a total of 18 tooth portions 623 are provided at intervals in the circumferential direction. In other words, the stator core 621 has a total of 18 slots 624 formed at intervals in the circumferential direction. The tooth portions 623 are arranged at equal intervals in the circumferential direction.
The rotor 61 has a number of magnetic pole portions 616 that is greater than the number of teeth 623. The number of magnetic pole portions is 4/3 of the number of slots.

A stator winding 622 is wound around each tooth 623. That is, the plural-phase stator windings 622 are provided so as to pass through the slots 624. In FIG. 3, the stator winding 622 is shown in the slot 624. Each of the multiple-phase stator windings 622 belongs to any one of U phase, V phase, and W phase. The stator windings 622 are arranged, for example, in the order of U phase, V phase, and W phase. In the present embodiment, as the stator winding 622, a stator winding that is thicker than the stator winding that is used in the rotating electric machine used only for the generator is used.

The rotor position detection device 63 is arranged in the starter generator storage portion 65. The rotor position detection device 63 is supported by the crankcase 21 so that its position is fixed with respect to the crankcase 21 within the crankcase 21. The rotor position detecting device 63 outputs a signal indicating the detection of the position of the rotor 61 due to the change in electrical characteristics due to the passage of the magnetic pole portion 616. A Hall IC is used as the rotor position detection device 63.

The starter generator 60 is connected to the crankshaft 24 of the 4-stroke engine 20. Specifically, the rotor 61 is connected to the crankshaft 24 so as to rotate at a fixed speed ratio with respect to the crankshaft 24.
In the present embodiment, the rotation axis of the starter/generator 60 and the rotation axis of the crankshaft 24 are substantially coincident with each other. The rotor 61 is attached to the crankshaft 24 without a power transmission mechanism (for example, a belt, a chain, a gear, a speed reducer, a speed increaser, etc.). The rotor 61 rotates with respect to the crankshaft 24 at a speed ratio of 1:1. The starter generator 60 is configured to rotate the crankshaft 24 in the forward direction by the forward rotation of the 4-stroke engine 20.

The starting generator 60 starts the 4-stroke engine 20 by rotating the crankshaft 24 in the forward direction when the engine is started. Further, the starting generator 60 is driven by the four-stroke engine 20 to generate power when the four-stroke engine 20 performs a combustion operation. That is, the start-up generator 60 has both a function of starting the 4-stroke engine 20 by rotating the crankshaft 24 in the forward direction and a function of being driven by the 4-stroke engine 20 to generate power when the 4-stroke engine 20 performs a combustion operation. Have both. The starter-generator 60 is normally rotated by the crankshaft 24 and functions as a generator during at least a part of the period after the start of the 4-stroke engine 20. That is, when the starting power generator 60 functions as a generator, the starting power generator 60 does not always have to function as a generator after the combustion of the engine is started. Further, a period in which the starting generator 60 functions as a generator and a period in which the starting generator 60 functions as a vehicle driving motor after the start of combustion of the engine may be included.

The starter-generator 60 of this embodiment has more magnetic pole portions 616 than the number of tooth portions 623. Therefore, the starter generator 60 has a higher angular velocity than the starter generator having the magnetic pole portions smaller than the number of teeth. The angular velocity contributes to the impedance of the winding.
That is, the impedance of the winding is roughly expressed by the following equation.
(R ² +ω ² L ² ) ^1/2
Here, R is a DC resistance, ω is an angular velocity about an electrical angle, and L is an inductance.

The angular velocity ω with respect to the electrical angle is expressed by the following equation.
ω=(P/2)×(N/60)×2π
Where P: number of magnetic poles, N: rotational speed [rpm]

Since the starter-generator 60 has more magnetic poles 616 than the number of teeth 623, the angular velocity ω is larger than that of a starter-generator having less magnetic poles than the number of teeth. Therefore, the impedance when rotating is large. Moreover, as the rotation speed N increases, the angular speed ω increases, and the impedance increases.
Therefore, the start-up generator 60 can suppress the generated current with a large impedance in the rotation region used as the generator.

Further, as the stator winding 622 used in the starting generator 60 of the present embodiment, a stator winding thicker than the stator winding used in the rotating electric machine used only for the generator is used. By using a thicker stator winding, the DC resistance of the stator winding in the impedance of the starter generator 60 can be reduced. By reducing the DC resistance of the stator winding, it is possible to generate a large torque in the low speed rotation region where the start-up generator 60 is used as a starter motor.

FIG. 4A is an explanatory diagram that schematically shows the drive characteristics of the starting generator 60. FIG. 4B is an explanatory diagram schematically showing power generation characteristics.
In the figure, the horizontal axis represents the rotation speed of the crankshaft 24. The rotation speed per scale on the horizontal axis is different between the drive characteristics shown in FIG. 4A and the power generation characteristics shown in FIG. 4B. The rotation speed per scale in the diagram of power generation characteristics is higher than the rotation speed per scale in the diagram of drive characteristics. The vertical axis represents the output torque in the positive direction and the generated current in the negative direction. The solid line shows the characteristics of the starter generator 60 according to this embodiment. The broken line shows the characteristics of the starting generator according to the comparative example. The start-up generator according to the comparative example has magnetic pole portions (for example, 2/3 of the number of slots) that are smaller than the number of teeth. When the crankshaft 24 is driven, the starter generator 60 (solid line) of the present embodiment outputs the same torque as the starter generator (broken line) according to the comparative example (FIG. 4(A)), and rotates at high speed. Occasionally, the generated current can be suppressed more than the starting generator (broken line) according to the comparative example (FIG. 4(B)).

The low viscosity oil OL is also supplied to the starter generator 60. The low-viscosity oil OL supplied to the cam chain storage unit 282 is also supplied to the starter generator storage unit 65. More specifically, the low-viscosity oil OL is supplied to the cam chain housing portion 282 and then stirred by the cam chain 281 to be in a mist form. The mist-like low-viscosity oil OL has a space in the starter/generator storage section 65 communicating with a space in the cam chain storage section 282. Is also supplied. Further, the low-viscosity oil OL supplied to the piston 26 also flows to the starter generator 60. The low-viscosity oil OL supplied to the starter/generator storage section 65 is stored in the lower portion of the starter/generator storage section 65. The low-viscosity oil OL collects so that a part of the starting generator 60 is immersed in the low-viscosity oil OL. For example, when the low-viscosity oil OL collects in a blocking wall (not shown) provided so as to surround a part of the start-up generator 60, part of the start-up generator 60 is immersed in the low-viscosity oil OL. For example, the low viscosity oil OL overflowing from the dam wall flows to the oil pan 211. Due to the rotation of the start-up generator 60, the low-viscosity oil OL attached to the start-up generator 60 diffuses into the crankcase 21.

Conventionally, a starter/generator has a partition between the starter/generator housing and a four-stroke engine to block the entry and exit of oil, and a rotor provided with a fan or fins for generating an air flow for cooling. On the other hand, in the present embodiment, the starter/generator 60 does not have a partition for blocking the entry and exit of oil between the starter/generator storage section 65 and the four-stroke engine 20, and the low-viscosity oil is stored in the starter/generator storage section 65. It is in contact with OL. Since the starter generator 60 can suppress the generated current in the rotation region used as a generator, the amount of heat generated during power generation is less than that of a teaching generator (comparative example of FIG. 4) having magnetic pole faces with less number of teeth. Also few. Therefore, in the start-up generator 60, the temperature of the stator winding 622 does not become higher than the temperature of the low-viscosity oil OL or does not easily increase. Therefore, even if the starter generator 60 is arranged so as to come into contact with the low-viscosity oil OL, which is a lubricating oil having a low evaporation temperature, the evaporation of the low-viscosity oil OL can be suppressed.
As a result, in the present embodiment, the start-up generator 60 can be arranged in an environment in which it contacts the low-viscosity oil OL, which is lubricating oil, while suppressing or avoiding an increase in the size of the cooling mechanism of the start-up generator 60. Furthermore, the 4-stroke engine unit 10 does not need to be equipped with an oil cooler, a radiator and the like.
Further, since the starter generator 60 can suppress the generation of heat, it can suppress the change in the detection characteristics of the detection device.

In the 4-stroke engine unit 10, the partition between the starter generator housing portion 65 and the 4-stroke engine 20 can be eliminated without providing the rotor 61 with a fan or fins that generate an air flow for cooling. Therefore, it can be brought into contact with the low-viscosity oil OL of the 4-stroke engine 20. As a result, the size of the crankshaft 24 in the axial direction can be reduced. Further, since the 4-stroke engine unit 10 has the starter/generator 60, it is not necessary to provide a starter motor specialized for starting. Therefore, it is not necessary to attach a power transmission mechanism for transmitting the driving force from the starter motor to the crankshaft 24. Further, the rotor 61 is arranged in the direction of the cylinder 22 of the 4-stroke engine 20 rather than the stator 62 when viewed in the rotation axis direction of the crankshaft 24 of the 4-stroke engine 20. Therefore, the size of the crankshaft 24 in the axial direction can be further reduced.

Further, in the present embodiment, since the starter generator 60 can suppress the amount of heat generated during power generation, even if the low-viscosity oil OL having low viscosity is used as the lubricating oil, the low-viscosity oil OL is prevented from evaporating. be able to. Therefore, in the present embodiment, as the low-viscosity oil OL of the 4-stroke engine 20, a low-viscosity lubricating oil whose low temperature viscosity grade is lower than 20 W can be used. As a result, even if the starting generator 60 is arranged in an environment in which it contacts the low-viscosity oil OL, which is lubricating oil, it is possible to reduce or omit stirring of the low-viscosity oil OL by the starting generator 60 for cooling. Therefore, the starter generator 60 can reduce not only the energy loss accompanying the decrease in the viscosity of the low viscosity oil OL but also the energy loss accompanying the stirring of the low viscosity oil OL. Further, the resistance to rotation of the starter generator 60 can be reduced. As a result, the 4-stroke engine unit 10 can further reduce the size of the starting generator.

In the present embodiment, as described above, the stator winding 622 used in the starter-generator 60 is, for example, a stator winding thicker than the stator winding used in the rotating electric machine used only in the generator. It Therefore, a large torque can be generated in the low speed rotation region where the starter/generator 60 is used as a starter motor. Further, in the present embodiment, the low-viscosity oil OL of the 4-stroke engine 20 may be a low-viscosity oil having a low temperature viscosity grade lower than 20W. Therefore, the start-up generator 60 can reduce resistance to rotation at the time of starting. Therefore, for example, even in a single-cylinder engine having a high load region and a low load region during four strokes, it is possible to obtain a torque that overcomes the high load region.

In addition, in the present embodiment, the rotor position detection device 63 can be arranged in the starter/generator storage portion 65 that is a space in which the starter/generator 60 is stored. The Hall IC used in the rotor position detection device 63 has an input resistance that depends on temperature, and is not suitable for use in a high temperature environment. Therefore, conventionally, it was difficult to arrange the rotor position detecting device in the space in which the starter-generator is housed. However, in the present embodiment, the starter generator 60 can suppress the amount of heat even during power generation. Therefore, even if the rotor position detection device 63 is installed in the starter/generator storage portion 65, the effect of the Hall IC can be sufficiently exerted.

FIG. 5 is a side view showing a straddle-type vehicle equipped with the 4-stroke engine unit of FIG. 1.
More specifically, the straddle-type vehicle 1 is an MT (manual transmission)-type straddle-type vehicle. The saddle riding type vehicle 1 is a motorcycle. More specifically, the saddle riding type vehicle 1 is an MT type motorcycle.
More specifically, the saddle riding type vehicle 1 includes a 4-stroke engine unit 10, a vehicle body 11, a front fork 12, a handlebar 13, front wheels 14, drive wheels 15, a seat 16, and a power storage device 17. , Rear arm 151.

The front fork 12 is rotatably supported by the vehicle body 11. The handlebar 13 is fixed to the upper end of the front fork 12. That is, the handlebar 13 is rotatably supported by the vehicle body 11 via the front fork 12. A manual clutch lever 50 is provided at the left end of the handlebar 13. A brake lever (not shown) and an accelerator operator are provided on the right side of the handlebar 13. The front wheel 14 is rotatably supported by the front fork 12.
The rear arm 151 is swingably supported by the vehicle body 11. The drive wheel 15 is rotatably supported by the rear arm 151.

The 4-stroke engine unit 10 is held by the vehicle body 11. More specifically, the 4-stroke engine unit 10 is attached to a frame (not shown) of the vehicle body 11. The 4-stroke engine unit 10 outputs power from the output section 39 to the drive wheels 15. The output unit 39 is a sprocket around which the chain 152 is wound. The output unit 39 is provided outside the crankcase 21. The output part 39 is actually covered with a cover (not shown) provided on the vehicle body 11, but is shown by a solid line so that it is easily exposed to the outside of the housing of the 4-stroke engine unit 10. There is. The power of the four-stroke engine unit 10 is output to the drive wheels 15 via the sprocket as the output section 39 and the chain 152. Below the output unit 39, step 111 is provided.

The seat 16 is a saddle type and is provided on the upper portion of the vehicle body 11. The driver of the saddle riding type vehicle 1 sits astride the seat 16 and puts his/her foot on the step 111 while traveling.
Power storage device 17 is arranged inside vehicle body 11. The power storage device 17 stores electric power.

1 Saddle-type vehicle 10 4-stroke engine unit 13 Handlebar 15 Drive wheel 20 4-stroke engine 21 Crankcase 22 Cylinder 24 Crankshaft 30 Manual transmission 39 Output section 40 Manual clutch 60 Starter generator 61 Rotor 62 Stator

Claims

A four-stroke engine unit,
The 4-stroke engine unit is
A crankcase configured to be internally lubricated with a low-viscosity oil having a low-temperature viscosity grade lower than 20 W, and a crankshaft rotatably supported by the crankcase, and the crankshaft is provided with A load fluctuation type four-stroke engine having a high load region in which a load for rotating a crankshaft is large, and a low load region in which a load for rotating the crankshaft is smaller than a load in the high load region,
A manual transmission provided in the crankcase so as to be lubricated by the low-viscosity oil, to which the driving force from the crankshaft is transmitted,
A stator core having a plurality of tooth portions provided with slots in the circumferential direction, and a stator having a plurality of phases of stator windings wound around the tooth portions, and the stator so as to face the stator with a gap. Having permanent magnet portions arranged in the same direction and having a magnetic pole surface larger than 2/3 of the number of slots, arranged coaxially with the crankshaft, and having no fan or fin for generating an air flow for cooling. A rotor, and a starting generator provided at a position in contact with the low viscosity oil.
The four-stroke engine unit according to claim 1, wherein
The four-stroke engine has a cylinder connected to the crankcase,
The rotor of the starter-generator has a bottomed tubular shape connected to the crankshaft between the stator and the cylinder in the axial direction in which the crankshaft extends.
The four-stroke engine unit according to claim 2, wherein
A rotor, which is supported by the crankcase so as to be fixed in position in the crankcase in the space in which the starter-generator is housed, and outputs a signal indicating detection of the position of the rotor. A position detection device is further provided.
A saddle type vehicle,
The straddle-type vehicle includes the four-stroke engine unit according to any one of claims 1 to 3.