GB2612216A

GB2612216A - MT-type straddled vehicle

Info

Publication number: GB2612216A
Application number: GB2219859.2A
Authority: GB
Inventors: Shibasaki Shoji
Original assignee: Yamaha Motor Co Ltd
Current assignee: Yamaha Motor Co Ltd
Priority date: 2020-07-03
Filing date: 2020-07-03
Publication date: 2023-04-26
Anticipated expiration: 2040-07-03
Also published as: DE112020007382T5; ES2940351A2; ES2940351R1; GB2612216B; WO2022003985A1; GB202219859D0; ES2940351B2

Abstract

Provided is an MT-type straddled vehicle capable of increasing output of a starter motor which also serves as a generator while securing a moment of inertia of a crankshaft. The MT-type straddled vehicle according to the present invention comprising a starter generator, wherein the starter generator is formed such that the distance between an outer end of a power output portion and an inner end of a tapered portion is shorter than the width of a bearing so that an outer end of a rotor is located between a position outward from an outer end of a crankshaft by the width of the bearing in the axial direction of the crankshaft and an inner position inward from the outer end of the crankshaft by the width of the bearing, and the width of teeth of a stator core is wider than the width of the bearing.

Description

DESCRIPTION

Title of Invention

MT-TYPE STRADDLED VEHICLE

Technical Field

[0001] The present teaching relates to an MT(Manual Transmission)-type straddled vehicle.

Background Art

[0002] For example, Patent Literature 1 (PTL 1) shows a motorcycle as a MT(Manual Transmission)-type straddled vehicle including a manual transmission. The MT-type straddled vehicle of PTL 1 includes an engine, a starter motor, and a power generation motor. The starter motor is connected to a crankshaft of the engine via a gear train. The power generation motor is mounted to an end portion of the crankshaft. The starter motor drives the crankshaft in rotation via the gear train functioning as a speed reducer, so that the engine starts.

The MT-type straddled vehicle according to PTL 1 has no centrifugal clutch. The straddled vehicle according to PTL 1 has a gear-shift multiple clutch provided in a right end portion of the engine crankshaft, and has a generator provided in a left end portion thereof. The straddled vehicle according to PTL 1 has a weight for giving a moment of inertia to the crankshaft, the weight being provided farther in the right direction than the generator on the crankshaft.

For example, Patent Literature 2 (PTL 2) shows a motorcycle as an MT-type straddled vehicle. The motorcycle of PTL 2 includes an ACG starter that functions as a starter motor, too. The motorcycle of PTL 2 has no clutch lever, and has a centrifugal clutch provided on an end portion of a crankshaft.

Citation List Patent Literature [0003] PTL 1: Japanese Patent Application Laid-Open No. 2000-87833 PTL 2: Japanese Patent No. 5942035

Summary of Invention

Technical Problem [0004] It is conceivable that the MT-type straddled vehicle shown in PTL 1 for example employs the generator that functions as the starter motor, too, shown in PTL 2 for example.

The starter motor serving also as the generator is connected to the crankshaft not via a speed reducer, as shown in PTL 2 for example. Therefore, it is desired that the starter motor serving also as the generator has a high output that allows the engine to start in a short period of time. In addition, the centrifugal clutch as shown in PTL 2 is not provided to the crankshaft of the MT-type straddled vehicle. This is why the crankshaft requires a greater moment of inertia, too, in order to overcome a rotational load and to keep rotating. The MT-type straddled vehicle, however, is a compact vehicle, and thus both a size increase of the vehicle and a size increase of its engine need to be suppressed. The present teaching aims to provide an MT-type straddled vehicle capable of: suppressing a size increase of an engine, giving a greater moment of inertia to a crankshaft, and giving a starter motor serving also as a generator an increase in output.

Solution to the Problem [0005] The present inventor conducted studies on an output of a starter motor that also serves as a generator. In the studies, the present inventor discovered that the output of the starter motor can be increased by: (i) reducing the intervals between permanent magnet parts of a rotor and teeth of a stator core in the radial direction; and (ii) increasing the thickness of the teeth of the stator core in the axial direction.

To attain the condition (i), the present inventor considered arranging the outward end of the rotor at a location between an outward position and an inward position of an engine crankshaft in the axial direction of the crankshaft. Here, the outward position refers to a position located farther in the outward direction than the outward end of the crankshaft by a distance corresponding to the width of a bearing. The inward position refers to a position located farther in the inward direction than the outward end of the crankshaft by a distance corresponding to the width of the bearing. The rotor of the starter generator is attached to an end portion of the crankshaft. The crankshaft is supported by plural bearings, and if the distance from the outward end of the outermost bearing to the outward end of the rotor is long, a shaking of the rotation axis is likely to increase at a time of rotation because of a tolerance and the like. In correspondence, a shake amplification of a magnet position in the radial direction is likely to increase. If the spatial gap between the permanent magnet parts of the rotor and the teeth of the stator core in the radial direction 5 is increased with the shake amplification of the magnet position taken into account, the output of the starter generator tends to decrease. This is based on the fact that torque of the starter generator is easily influenced by the amount of magnetic flux flowing into the inside of the stator core, without leaking to the outside of the stator core, which comes from the permanent 10 magnet parts of the rotor.

[0006] The present inventor tried arranging the outward end of the rotor at the above-described position, to reduce the distance from the outward end of the crankshaft's outermost bearing to the outward end of the rotor. Therefore, the fluctuation that is likely to occur in the spatial gap between the permanent magnet parts of the rotor and the teeth of the stator core in the radial direction can be reduced, the fluctuation being caused by a shaking of the rotation axis. As a result, the permanent magnet parts of the rotor can be arranged close to the teeth of the stator core in the radial direction, which gives the starter generator an increase in output. Moreover, the reduced distance from the outward end of the outermost bearing of the crankshaft to the outward end of the rotor can suppress a size increase of the engine while giving the starter generator an increase in output.

[0007] To attain the condition (ii), the present inventor considered widening the width of the teeth of the stator core to be larger than the width of the bearing. The starter generator is rotated by a magnetic field repelling and attracting the permanent magnet parts of the rotor, the magnetic field being produced by an electric current flowing through windings of a stator. Increasing the thickness of the teeth of the stator core allows magnetic fluxes flowing in the teeth to increase. Even though, therefore, the permanent magnet parts of the rotor are larger, so that magnetic fluxes come from the permanent magnet parts of the rotor is allowed to increase, ineffective magnetic fluxes that don't flow into the teeth of the stator core can be reduced. This is why the width of the teeth of the stator core is larger than the width of the bearing. Consequently, the thickness of the teeth of the stator core can be increased, to give the starter generator an increase in output.

[0008] To give the starter generator a further increase in output, the present inventor examined satisfying both of the conditions (i) and (ii). Especially in a starter generator of an outer rotor type as shown in PTL 1 and PTL 2, it is conceivable to simply reduce the width of the rotor in the left-right direction, in order to satisfy the condition (0. This, however, makes satisfaction of the condition (ii) impossible. To be specific, widening the teeth of the stator core to be larger in the left-right direction is impossible. In the starter generator of an outer rotor type, on the other hand, it is conceivable to simply increase the width of the rotor in the left-right direction, in order to satisfy the condition (ii).

This, however, makes satisfaction of the condition (i) impossible. To be specific, reducing the spatial gap between the permanent magnet parts of the rotor and the teeth of the stator core in the radial direction is impossible.

[0009] Then, in order to satisfy the conditions (0 and (ii) in the starter generator of outer rotor type, the present inventor considered (iii) reducing the 15 distance from the outward end of the bearing to the inward end of the rotor.

To attain the condition the present inventor considered shortening the distance from the outward end of a power output part to the inward end of a tapered portion of the crankshaft, to be shorter than the width of the bearing. The tapered portion, which is for fixing the rotor to the crankshaft, is formed in an end portion of the crankshaft. The power output part, as exemplified by a cam chain sprocket, is disposed in a portion between the bearing and the tapered portion in the left-right direction, that is, a straight portion. This is why shortening the distance from the outward end of the power output part to the inward end of the tapered portion, to be shorter than the bearing can contribute to shortening the distance between the outward end of the outermost bearing of the crankshaft and the end of the tapered portion of the crankshaft toward the bearing. Consequently the inward end of the rotor can be closer to the bearing.

[0010] As described above, arranging the inward end of the rotor closer to the bearing makes it possible to increase the thickness of the teeth of the stator core, while suppressing outward protrusion of the rotor. Thus, satisfaction of the condition (iii) makes it possible that the outward end of the rotor is arranged between the inward position and the outward position, and at the same time widening the width of the teeth of the stator core to be larger than the width of the bearing in the left-right direction.

Especially in a starter generator of outer rotor type, a rotor generally has a bottomed cylinder shape. As compared to a rotor having a bottomed cylinder shape that is open toward the bearing of the crankshaft for example, a rotor having a bottomed cylinder shape that is open toward the opposite direction to the bearing of the crankshaft has the rotor's connection position and the rotor's center-of-gravity disposed closer to the bearing. Accordingly, satisfaction of the condition (iii) can suppress a shaking of the rotation axis when the rotor rotates. Thus, in the starter generator of outer rotor type, the rotor can satisfy both of the conditions (i) and (ii) by satisfying the condition (iii).

This is because even though the thickness of the teeth of the stator core and the size of the permanent magnet parts are increased, an increase in shaking of the rotation axis can be suppressed, so that an increase in the spatial gap between the permanent magnet parts and the teeth can also be suppressed.

Furthermore, shortening the distance from the outward end of the 15 power output part to the inward end of the tapered portion of the crankshaft to be shorter than the width of the bearing can suppress shortening of the distance from the outward end of the crankshaft to the inward end of the tapered portion of the crankshaft. This in turn can suppress shortening of the width of a weight portion of the rotor attached to the crankshaft in its axial direction, and therefore can contribute to giving the greater moment of inertia to the crankshaft.

Accordingly, a size increase of the engine can be suppressed, the crankshaft can be given a greater moment of inertia, and the starter motor serving also as the generator can be given an increase in output.

[0011] To attain the foregoing aims, an aspect of the present teaching provides an MT-type straddled vehicle having the following configuration.

(1) An MT-type straddled vehicle including: a vehicle body; an engine attached to the vehicle body the engine including a 30 crankshaft, a crankcase, and a bearing provided to the crankcase, the crankshaft being configured to output power, the crankcase accommodating the crankshaft, the bearing supporting the crankshaft rotatably; a driving wheel that receives power outputted from the engine to drive the MT-type straddled vehicle; a multistage transmission accommodated in the crankcase, the multistage transmission being configured to change a gear ratio between the speed of the crankshaft and the driving wheel in multiple stages; and a starter generator including a rotor and a stator, the rotor being attached to an end portion of the crankshaft so as to rotate together with the crankshaft, the stator being directly or indirectly fixed to the vehicle body with the relative position of the stator to the vehicle body maintained, the starter generator having both a function to start the engine and a function to be driven by the engine to generate electricity wherein the engine has a power output part disposed on the crankshaft between the starter generator and the bearing in an axial direction of the crankshaft in such a manner that the power output part rotates integrally with the crankshaft, the power output part being engaged with a power transmission element for transmitting rotation of the crankshaft to an auxiliary component of the engine such that power is partly outputted from the crankshaft to the auxiliary component of the engine, the stator includes a stator core and windings of plural phases, the stator core having plural teeth spaced from one another by slots in a circumferential direction, the windings being wound on the teeth, the rotor has permanent magnet parts disposed outside the stator in a radial direction, the permanent magnet parts being arranged in the circumferential direction so as to be opposed to the stator with a spatial gap therebetween, the rotor being configured to cover the inner side of the stator in the axial direction of the crankshaft, and to be supported by the crankshaft, the crankshaft has a straight portion and a tapered portion, the straight portion having the power output part disposed thereon, the tapered portion having the rotor disposed thereon, the tapered portion having a tapered shape that gradually tapers from an outward end of the straight portion, and for an outward end of the rotor to be located between an outward position and an inward position in the axial direction of the crankshaft and for the teeth of the stator core to have a width larger than the width of the bearing in the axial direction of the crankshaft, the power output part and the tapered portion are formed such that a distance between an outward end of the power output part and an inward end of the tapered portion is to be shorter than the width of the bearing, the outward position being located farther in an outward direction than an outward end of the crankshaft by a distance corresponding to the width of the bearing, the inward position being located farther in an inward direction than the outward end of the crankshaft by a distance corresponding to the width of the bearing.

[0012] The MT-type straddled vehicle of (1) includes the multistage transmission for changing the gear ratio in multiple stages. The MT-type straddled vehicle further includes the vehicle body, the engine, the driving wheel, and the starter generator. The engine includes the crankshaft, the crankcase, and the bearing. The crankshaft outputs power. The crankcase accommodates the crankshaft. The bearing supports the crankshaft to the crankcase in such a manner that the crankshaft is rotatable. The engine is attached to the vehicle body. Here, the direction "inward" in the axial direction of the crankshaft refers to a direction from an end of the crankshaft toward the center of the crankshaft in the axial direction of the crankshaft. The direction "outward" in the axial direction of the crankshaft refers to a direction from the center of the crankshaft toward the end of the crankshaft in the axial direction of the crankshaft. In a case where the axial direction of the crankshaft coincides or substantially coincides with the left-right direction (vehicle width direction) of the vehicle body, the direction "inward" in the direction in which the axis of the crankshaft extends is defined as the direction toward the center of the vehicle body in the axial direction of the crankshaft.

The direction "outward" in the direction in which the axis of the crankshaft extends is defined as the direction toward the outside of the vehicle body in the axial direction of the crankshaft.

The starter generator, which also has the function to generate electricity, includes the stator and the rotor. The rotor has the permanent magnet parts disposed outside the stator in the axial direction of the crankshaft, the permanent magnet parts being arranged in the circumferential direction so as to be opposed to the stator with a spatial gap therebetween. The rotor is configured to cover the inner side of the stator in the axial direction of the crankshaft, and to be supported by the crankshaft. In a preferred embodiment, the starter generator is a motor of outer rotor type. In a preferred embodiment, the rotor has a bottomed cylinder shape that is open outward in the axial direction of the crankshaft.

The rotor having a bottomed cylinder shape that is open outward in the axial direction of the crankshaft can be connected to the crankshaft at a 35 position closer to the bearing as compared to, for example, a rotor having a bottomed cylinder shape that is open inward in the axial direction of the

S

crankshaft. In addition, a portion of the crankshaft protruding from the bearing can be shortened. This can suppress a shake of the rotation axis line when the crankshaft rotates, which may otherwise be caused by a shaking of the center of gravity of the crankshaft and the rotor because of a tolerance and the like, for example.

The engine has the power output part. The power output part is disposed on the crankshaft between the starter generator and the bearing in the axial direction of the crankshaft in such a manner that the power output part rotates integrally with the crankshaft. The power output part is engaged with the power transmission element such that the power output part partly outputs power from the crankshaft to the auxiliary component of the engine. The power transmission element is a member for transmitting rotation of the crankshaft to the auxiliary component of the engine. Examples of the power transmission element include a cam, a chain, and the like.

[0013] In the MT-type straddled vehicle of (1), the distance between the outward end of the power output part and the inward end of the tapered portion is shorter than the width of the bearing. Further with this configuration, the MT-type straddled vehicle of (1) has the outward end of the rotor located between the outward position and the inward position in the axial direction of the crankshaft, and has the width of the teeth of the stator core larger than the width of the bearing in the axial direction of the crankshaft.

In the MT-type straddled vehicle of (1), the outward end of the rotor is located between the outward position and the inward position. This can (i) reduce the spatial gap between the permanent magnet parts of the rotor and the teeth of the stator core in the radial direction. In an embodiment, the outward end of the rotor is preferably located between the outward position and the outward end of the crankshaft in the axial direction of the crankshaft. Shortening a distance from the outward end of the outermost bearing of plural bearings supporting the crankshaft to the outward end of the rotor can suppress a shaking of the rotation axis at a time of rotation, which may otherwise be caused by a tolerance and the like. That is, a shake amplification of the position of the permanent magnet parts in the radial direction can be suppressed. Accordingly, a fluctuation that is likely to occur in the spatial gap between the permanent magnet parts of the rotor and the teeth of the stator core in the radial direction can be reduced, the fluctuation being caused by a shaking of the rotation axis. Consequently, the permanent magnet parts of the rotor can be arranged close to the teeth of the stator core in the radial direction. This gives the starter generator an increase in output. Here, the outward end of the rotor may be located at the permanent magnet parts, or may be located at a part (such as the back yoke) supporting the permanent magnet parts.

[0014] Moreover, in the MT-type straddled vehicle of (1), the width of the stator in the axial direction of the crankshaft is larger than the width of the bearing in the axial direction of the crankshaft. As a result, (ii) the thickness of the teeth of the stator core can be increased. This gives the starter generator an increase in output. The starter generator is rotated by a magnetic field repelling and attracting the permanent magnets of the rotor, the magnetic field being produced by an electric current flowing through the windings of the stator. Increasing the thickness of the teeth of the stator core in the axial direction of the crankshaft allows magnetic fluxes flowing in the teeth to increase.

Increasing the thickness of the teeth of the stator core in the axial direction of the crankshaft, therefore, can reduce ineffective magnetic fluxes, that is, magnetic fluxes that don't flow into the teeth of the stator core, even though the permanent magnet parts of the rotor are larger so that magnetic fluxes come from the permanent magnet parts of the rotor is allowed to increase.

[0015] Furthermore, in the MT-type straddled vehicle of (1), the distance from the outward end of the power output part to the inward end of the tapered portion is shorter than the width of the bearing. As a result, a distance from the outward end of the bearing to the inward end of the rotor can be shortened. The tapered portion is a portion having a tapered shape that gradually tapers from the outward end of the straight portion so that the rotor can be fixed to the crankshaft. The power output part such as a cam chain sprocket is provided between the outward end of the bearing and the inward end of the tapered portion in the axial direction of the crankshaft. If, therefore, the distance from the outward end of the power output part to the inward end of the tapered portion is shorter than the width of the bearing, the distance between the outward end of the bearing and the inward end of the tapered portion can be shortened. This allows the inward end of the rotor to be closer to the bearing. Since the distance between the outward end of the bearing and the inward end of the tapered portion can be shortened, it is possible to obtain a distance from the outward end of the crankshaft to the inward end of the tapered portion of the crankshaft. This can suppress shortening, in the axial direction of the crankshaft, of the width of a portion serving as a weight of the rotor attached to the crankshaft, and consequently the crankshaft can he given a greater moment of inertia.

[00161 In the MT-type straddled vehicle of (1), the inward end of the rotor is 5 closer to the bearing, which makes it possible to increase the thickness of the teeth of the stator core while suppressing outward protrusion of the rotor. That is, in the axial direction of the crankshaft, the outward end of the rotor can be disposed between the outward position and the inward position relative to the outward end of the crankshaft, and at the same time the width 10 (thickness) of the stator core can be larger than the width of the bearing.

Accordingly the MT-type straddled vehicle of (1) can satisfy both of the conditions (0 and (ii) by satisfying the condition (iii). This is because even though the thickness of the teeth of the stator core is increased and the size of the permanent magnet parts is increased, an increase in a shake amplification of the rotation axis can be suppressed, so that an increase in the spatial gap between the permanent magnet parts and the teeth can be suppressed. Consequently, in the MT-type straddled vehicle of (1), a size increase of the engine can be suppressed, a greater moment of inertia can be obtained, and the starter generator serving also as a generator can be realized in order to be given an increase in output.

[0017] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(2) In the MT-type straddled vehicle according to (D, the rotor has permanent magnet parts arranged in the circumferential 25 direction so as to be opposed to the stator with a spatial gap therebetween, the permanent magnet parts having magnetic pole faces, the number of which is greater than 2:3 of the number of the slots.

[00181 In the MT-type straddled vehicle of (2), the number of magnetic pole faces: the number of slots in the starter generator is greater than 2:3. This suppresses generation of an electric current at a time of high rotations when the starter generator operates as a generator. This can consequently suppress a rise in the temperature of the stator windings at a time of high rotations. Accordingly, the in MT-type straddled vehicle of (2), heat generation by the starter generator can be suppressed, while the starter generator allows to be given an increase in output. For example, the need for a structure (such as a fan, a heat sink, or the like) for cooling the starter generator can be eliminated.

Accordingly, in the MT-type straddled vehicle of (2), a size increase of the engine can be suppressed, a greater moment of inertia can be obtained, and the starter generator serving also as a generator can be realized in order to be given an increase in output.

[0019] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(3) In the MT-type straddled vehicle according to (1) or (2), the crankcase is configured such that its inside is lubricated with an oil, and the starter generator includes a rotor that is provided without a fan nor a fin for producing an air stream for cooling, and is positioned so as to be in contact with the oil.

[0020] In the MT-type straddled vehicle of (3), heat dissipation can be carried out by the oil of the starter generator. Accordingly, in the MT-type straddled vehicle of (3), the starter generator can give an increase in output while a size increase of a cooling mechanism can be suppressed or avoided. In the MT-type straddled vehicle of (3), therefore, a size increase of the engine can be suppressed, a greater moment of inertia can he obtained, and the starter generator serving also as a generator can be realized in order to be given an increase in output.

[0021] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(4) In the MT-type straddled vehicle according to any one of (1) to (3), the starter generator is configured to output power at least when the 25 engine is in combustion operation.

[0022] The MT-type straddled vehicle of (4) has the configuration of (1), and in addition, is configured to use the starter generator to assist an engine output, which makes it unnecessary to additionally provide another motor for assisting a driving force of the MT-type straddled vehicle, for example. Accordingly, in the MT-type straddled vehicle of (4), a size increase of the engine can be suppressed, a greater moment of inertia can be obtained, and the starter generator serving also as a generator can be realized in order to be given an increase in output. Thus, a size increase of the MT-type straddled vehicle can be suppressed even though an assist function to assist a driving force of the MT-type straddled vehicle is additionally provided. Here, the starter generator may output power when the engine is not in combustion operation.

[0023] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(5) In the MT-type straddled vehicle according to any one of (1) to (4), the starter generator has a rotor position detection device that is a 5 pickup coil that has a winding that is different from the windings of the stator. [0024] In the MT-type straddled vehicle of (5), the position of the rotor of the starter generator is detected by the pickup coil having the winding. It therefore is not necessary to use a Hall IC, which is less durable to heat than the pickup coil, for example. Using a Hall IC involves the need for a structure 10 that cools the Hall IC, for example. Accordingly, in the MT-type straddled vehicle of (2), a size increase of the engine can be suppressed, a greater moment of inertia can be obtained, and the starter generator serving also as a generator can be realized in order to give an increase in output. Here, it should he noted that the winding different from the windings of the stator is positioned so as 15 not to be in contact with the windings of the stator.

[0025] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(6) The MT-type straddled vehicle according to any one of (1) to (5) further includes a crankcase cover that covers at least an outward-facing 20 portion of the starter generator, wherein a spatial gap between the outward end of the stator and an inner wall surface of the crankcase cover in the axial direction of the crankshaft is larger than the width of the bearing.

[0026] The MT-type straddled vehicle of (6) has the configuration of (1), and in addition, is configured such that the stator and the crankcase cover can be spaced from each other by a gap so as to avoid hindering a flow of a fluid. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover. Accordingly a size increase of the engine can be suppressed, a temperature rise within the crankcase cover can be suppressed, and the starter generator can be given an increase in output.

[0027] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(7) The MT-type straddled vehicle according to any one of (1) to (5) further includes a crankcase cover that covers at least an outward-facing 35 portion of the starter generator, wherein a spatial gap between the outward end of the rotor and an inner wall surface of the crankcase cover in the axial direction of the crankshaft is larger than the width of the bearing.

[0028] The MT-type straddled vehicle of (7) has the configuration of (1), and in addition, is configured such that the rotor and the crankcase cover can be spaced from each other by a gap so as to avoid hindering a flow of a fluid. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover. Accordingly a size increase of the engine can be suppressed, a temperature rise within the crankcase cover can be suppressed, and the starter generator can be given an increase in output.

[0029] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(8) In the MT-type straddled vehicle of (6), a spatial gap between the outward end of the rotor and the inner wall surface of the crankcase cover in the axial direction of the crankshaft is larger 15 than the width of the bearing.

[00301 The MT-type straddled vehicle of (8) has the configuration of (1), and in addition, is configured such that the rotor and the crankcase cover can be spaced from each other by a gap so as to avoid hindering a flow of a fluid. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover. Accordingly a size increase of the engine can be suppressed, a temperature rise within the crankcase cover can be suppressed, and the starter generator can be given an increase in output.

(9) The MT-type straddled vehicle according to any one of (1) to (5) further includes a crankcase cover that covers at least an outward-facing portion of the starter generator, wherein the rotor includes a back yoke part having a cylindrical shape, a bottom wall part having a disc-like shape, and a boss part having a cylindrical shape, 30 the bottom wall part extending continuously from the back yoke part, the boss part being interposed between the bottom wall part and the crankshaft, and a distance from at least a portion of the back yoke part to an inner wall surface of the crankcase cover in the radial direction is longer than the width of the bearing in the axial direction of the crankshaft.

[0022] The MT-type straddled vehicle of (9) has the configuration of (1), and in addition, is configured such that the rotor includes the permanent magnet parts, the back yoke part having a cylindrical shape, the bottom wall part having a disc-like shape extending continuously from the back yoke part, and the boss part having a cylindrical shape interposed between the bottom wall part and the crankshaft. In the MT-type straddled vehicle of (9), the rotor and 5 the crankcase cover can be at least partially spaced from each other by a gap so as to avoid hindering a flow of a fluid. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover. Accordingly, a size increase of the engine can be suppressed, a temperature rise within the crankcase cover can be suppressed, and the starter generator can be given an 10 increase in output.

[0022] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(10) In the MT-type straddled vehicle of (6) or (7), the rotor includes a back yoke part having a cylindrical shape, a bottom 15 wall part having a disc-like shape, and a boss part having a cylindrical shape, the bottom wall part extending continuously from the back yoke part, the boss part being interposed between the bottom wall part and the crankshaft, and a distance from at least a portion of the back yoke part to the inner wall surface of the crankcase cover in the radial direction is longer than the width of 20 the bearing in the axial direction of the crankshaft.

[0034] The MT-type straddled vehicle of (10) has the configuration of (1), and in addition, is configured such that the rotor includes the permanent magnet parts, the back yoke part having a cylindrical shape, the bottom wall part having a disc-like shape extending continuously from the back yoke part, and the boss part having a cylindrical shape interposed between the bottom wall part and the crankshaft. In the MT-type straddled vehicle of (10), the rotor and the crankcase cover can be at least partially spaced from each other by a gap so as to avoid hindering a flow of a fluid. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover. Accordingly, a size increase of the engine can be suppressed, a temperature rise within the crankcase cover can be suppressed, and the starter generator can be given an increase in output.

[0035] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(11) In the MT-type straddled vehicle according to any one of (1) to (8), the rotor includes a back yoke part having a cylindrical shape, a bottom wall part having a disc-like shape, and a boss part having a cylindrical shape, the bottom wall part extending continuously from the back yoke part, the boss part being interposed between the bottom wall part and the crankshaft, and a spatial gap between an inner circumferential surface of the stator 5 defining a hole through which the crankshaft is received and an outer circumferential surface of the boss part is smaller than the width of the bearing in the axial direction of the crankshaft.

[0036] The MT-type straddled vehicle of (11) has the configuration of (1), and in addition, is configured to allow a greater amount of air or oil mist to be guided to the outside of the stator in the radial direction because of the narrow spatial gap between the stator and the boss part. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover. Accordingly, a size increase of the engine can be suppressed, a temperature rise within the crankcase cover can be suppressed, and the starter generator can be given an increase in output.

[00371 In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(12) In the MT-type straddled vehicle of (10), a spatial gap between an inner circumferential surface of the stator 20 defining a hole through which the crankshaft is received and an outer circumferential surface of the boss part is smaller than the width of the bearing in the axial direction of the crankshaft.

[0038] The MT-type straddled vehicle of (12) has the configuration of (1), and in addition, is configured to allow a greater amount of air or oil mist to be guided to the outside of the stator in the radial direction because of the narrow gap between the stator and the boss part. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover. Accordingly, a size increase of the engine can be suppressed, a temperature rise within the crankcase cover can be suppressed, and the starter generator can be given an increase in output.

[0039] In an aspect of the present teaching, an MT-type straddled vehicle may have the following configuration.

(13) In the MT-type straddled vehicle according to any one of (1) to (12), the engine is attached to the vehicle body with the axis of the 35 crankshaft extending in a left-right direction of the vehicle body [0040] The MT-type straddled vehicle of (13) has a transverse type engine, which means the engine having the crankshaft of which the axis extends in the left-right direction of the vehicle body. In the MT-type straddled vehicle of (13), therefore, downsizing of the engine can be made possible because it is possible to arrange the engine without converting the direction of an output shaft of the engine from the forward-backward direction to the left-right direction.

[0041] The terminology used herein is for defining particular embodiments only and is not intended to be limiting the teaching. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. As used herein, the terms "including", "comprising", or "having", and variations thereof specify the presence of stated features, steps, operations, elements, components, and/or equivalents thereof, and can include one or more of steps, operations, elements, components, and/or their groups. As used herein, the terms "attached", "connected", "coupled", and/or equivalents thereof are used in a broad sense, and include both of direct and indirect attachment and coupling unless otherwise specified. The terms "connected" and "coupled" are not limited to physical or mechanical connection or coupling, and can include direct and indirect electrical connection and coupling. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present teaching belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the present teaching and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. It will be understood that the description of the present teaching discloses multiple techniques and steps. Each of these has individual benefit and each can also be used in conjunction with one or more, or in some cases all, of the other disclosed techniques. Accordingly, for the sake of clarity, this description will refrain from repeating every possible combination of the individual steps in an unnecessary fashion. Nevertheless, Description and Claims should be read with the understanding that such combinations are entirely within the scope of the present teaching and the claims.

[0042] A novel MT-type straddled vehicle is explained in the present description. In the description given below, however, for the purposes of 35 explanation, numerous specific details are set forth in order to provide a thorough understanding of the present teaching. It will be apparent, nonetheless, that those skilled in the art may practice the present teaching without these specific details. The present disclosure is to be considered as an exemplification of the present teaching, and is not intended to limit the present teaching to the following specific embodiments illustrated by drawings or

descriptions.

[0043] The MT-type straddled vehicle is a straddled vehicle including a manual multistage transmission. The straddled vehicle refers to a vehicle including a saddle on which a driver can sit astride. Examples of the straddled vehicle encompass a moped motorcycle, an off-road motorcycle, and an on-road motorcycle. The straddled vehicle is not limited to a two-wheeled motorcycle. Alternatively, for example, the straddled vehicle may be a three-wheeled motor vehicle or an all-terrain vehicle (ATV). The three-wheeled motor vehicle may include two front wheels and one rear wheel. Alternatively, the three-wheeled motor vehicle may include one front wheel and two rear wheels. The straddled vehicle may include a driving wheel that is a rear wheel or a front wheel. Alternatively, the straddled vehicle may include driving wheels that are a rear wheel and a front wheel. The straddled vehicle is preferably configured to be capable of making a turn in a leaning posture. The straddled vehicle configured to be capable of making a turn in a leaning posture can make a turn while leaning toward the center of a curve. With this, the straddled vehicle configured to be capable of making a turn in a leaning posture can resist against a centrifugal force acting on the vehicle during a turn. Since it is desired that the straddled vehicle configured to be capable of making a turn in a leaning posture has agility, the responsiveness for running to a manipulation for starting is considered important. For example, in the straddled vehicle configured to be capable of making a turn in a leaning posture, a torque converter that works with use of a dynamic fluid action is not provided in a drive power transmission path from a drive source to the driving wheel.

[0044] The multistage transmission is configured to change the gear ratio in multiple stages in response to a manipulation on a shift pedal, for example. The multistage transmission may be configured to change the gear ratio in response to a manipulation. The multistage transmission may be configured to change the gear ratio irrespective of a manipulation. A continuously variable transmission does not fall within the definition of the multistage transmission.

[0045] The engine encompasses a single cylinder engine and an engine having two or more cylinders, for example. The engine having two or more cylinders encompasses a parallel engine, a V-type engine, and a horizontally-opposed engine, for example. The engine encompasses a transverse engine and a longitudinal engine, for example. Operation of the engine means that the engine outputs power generated by gas combustion, in the form of a torque and a rotation speed of the crankshaft. The engine can be a four-stroke engine having, in four strokes, a high-load region and a low-load region, for example. Examples of the four-stroke engine having the high-load region and the low-load region in four strokes include a single cylinder engine, a two-cylinder engine, a three-cylinder engine of unequal interval combustion type, or a four-cylinder engine of unequal interval combustion type. The four-stroke engine having the high-load region and the low-load region in four strokes is less stable when rotating at a low engine rotation speed than engines of other types. Here, it should be noted that the engine may be a four-stroke engine not having the high-load region and the low-load region in four strokes, for example. The high-load region refers to a region in one combustion cycle of the engine, in which a load torque is higher than the average value of load torques over the one combustion cycle. The kw-load region refers to a region that is other than the high-load region in the one combustion cycle. In the engine, from the viewpoint of the rotation angle of the crankshaft, the low -load region is wider than the high-load region, for example. A compression stroke has an overlap with the high-load region.

[0046] The starter generator is a brushless motor, for example. The starter generator is a generator that is driven by the engine or the driving wheel, to generate electricity. The starter generator may have a function to assist an output of the engine. The starter generator is a rotating electric machine capable of both starting the engine and generating electricity. The starter generator is, for example, a surface permanent magnet type (SPM type) having magnetic pole portions of a rotor exposed from a magnetic material. The starter generator is not limited to this, and for example, may he an interior permanent magnet type (IPM type) having magnetic pole portions of a rotor embedded in a magnetic material. The ratio [the number of magnetic pole faces: the number of slots] is greater than 2:3, for example. The ratio [the number of magnetic pole faces: the number of slots] is not particularly limited to this, and may be 2:3 or less, for example. In a case of the ratio [the number of magnetic pole faces: the number of slots] being greater than 2:3, the upper limit value of [the number of magnetic pole faces: the number of slots] may be 4:3, for example. In an example of the present disclosure, the ratio is 8:9 or more. In an example of the present disclosure, the ratio is 1:1 or more. In an example of the present disclosure, the ratio is greater than 1:1. In an example of the present disclosure, the ratio is 42. In some case, the slots of the stator are partially not provided for the purpose of installation of a control board or the like on the stator. In such a case, the number of slots may be determined on the assumption that slots are provided at positions where slots would be originally provided. The same applies to the number of magnetic poles of a flywheel. That is, in a case of a 4:3 arrangement of magnetic poles and slots in which the number of magnetic poles and the number of slots satisfy a relationship of substantially 4:3, it can be considered that the ratio [the number of magnetic pole faces: the number of slots] is 42.

[0047] The permanent magnet parts are disposed such that at least a part and 15 preferably all of the permanent magnet parts overlap the stator core in the radial direction, when viewed in a cross-section along the axial direction of the permanent magnet parts and the stator core, for example.

[0048] In a case of the rotor having a fan, the fan is normally provided to a support part for supporting the permanent magnet parts. In a case of the rotor having a fin, the fin is normally provided to a support part for supporting the permanent magnet parts. The support part normally has a bottomed cylindrical shape. The fan is provided to the support part so as to produce an air stream as the rotor rotates. If the fan is provided at a cylindrical shape portion (such as a back yoke part) of the support part having the bottomed cylindrical shape, the fan is formed so as to extend in the axial direction and protrude in the radial direction, for example. If the fan is provided at a bottom portion (such as a flat-plate shape portion) of the support part having the bottomed cylindrical shape, the fan is formed so as to extend in the radial direction and protrude in the axial direction, for example.

[0049] The bearing is a ball bearing, for example. The bearing may be a bearing other than the ball bearing, however. The bearing may be a roller bearing, for example. The bearing may be a plain bearing, for example. In a single cylinder engine, there are two support positions at which a crankshaft is supported by bearings. In a two cylinder engine, there are three support positions. In the present disclosure, the average value of the widths of plural bearings is used to refer to "the width of the bearing." In a case where plural bearings are provided for one support position, the total width of all the bearings provided for one support position corresponds to "the width of one bearing." [0050] The tapered portion is formed in the crankshaft. The tapered portion 5 is a portion of which the radial size continuously decreases from the center toward the distal end of the crankshaft in the axial direction thereof Here, the tapered portion may include a portion of which the radial size decreases stepwise, the portion being located in a part between the center and the distal end of the crankshaft in the axial direction thereof. The tapered portion fixes 10 the rotor and the weight of the starter generator via a cylindrical boss part of which the inside is formed to have a tapered shape.

[0051] The weight is attached to the crankshaft for the purpose of giving a greater moment of inertia to the crankshaft. The weight may be formed integrally with a rotor boss of the starter generator. It should be noted that a rotator of a centrifugal clutch, for example, is not included in the weight. A one-way clutch and a starter gear for transmitting power of the starter generator to the crankshaft, for example, is not included in the weight, either. When, for example, the support part for supporting the permanent magnet parts is provided to the tapered portion of the crankshaft while the weight is provided to the tapered portion, the weight can cooperate with the permanent magnet parts and the support part to constitute the rotor. When the support part for supporting the permanent magnet parts is provided to the tapered portion of the crankshaft while the weight is next to or adjacent to the support part in the axial direction, the weight can cooperate with the permanent magnet parts and the support part to constitute the rotor.

[0052] The power output part is, for example, a cam chain sprocket that transmits power to a cam chain for moving a cam of a cylinder head. The power output part may be, for example, an oil pump gear that drives an oil pump for supplying an engine oil in the engine. The power output part is not a component that transmits power from a power generating component different from the engine to the crankshaft of the engine. Thus, for example, a one-way clutch and a starter gear for transmitting power of the starter generator to the crankshaft is not the power output part.

The auxiliary component of the engine is equipment essential for engine 35 combustion operation. For example, an engine valve and a valve operating mechanism are auxiliary components of the engine, because the engine combustion operation cannot take place without operations of the engine valve and the valve operating mechanism. For example, an oil pump is an auxiliary component of the engine, because the engine combustion operation cannot take place without an operation of the oil pump. Here, equipment essential for engine combustion operation means equipment that is indispensable for carrying out the engine combustion operation under a situation where all equipment configurations or structures of the engine are maintained. For example, in an engine having an oil pump the oil pump normally corresponds to the "equipment essential for engine combustion operation." The oil pump is an auxiliary component of the engine, therefore. On the other hand, an engine including a dip lubrication system is able to carry out the engine combustion operation without using an oil pump, under a situation where all equipment configurations or structures of the engine are maintained. Thus, in the engine including the dip lubrication system, the oil pump does not correspond to the "equipment essential for engine combustion operation." The oil pump is not an auxiliary component of the engine, therefore. Equipment that transmits power resulting from the engine combustion operation to the outside of the engine is not the auxiliary component, because the engine combustion operation can take place without an operation of the equipment. For example, a clutch or a transmission is not the auxiliary component. The auxiliary component of the engine is provided to an engine main body, for example. The engine main body includes a cylinder head and a cylinder block. The auxiliary component of the engine may be provided either inside or outside the engine. The auxiliary component of the engine is configured to implement a function as the auxiliary component by mechanically receiving power from the power output part of the crankshaft via the power transmission element.

Advantageous Effects of Invention [0053] An MT-type straddled vehicle according to the present teaching can give 30 a greater moment of inertia to a crankshaft, and can give a starter motor serving also as a generator an increase in output.

Brief Description of Drawings

[0054] [FIG. 11 A diagram showing a configuration of an MT-type straddled 35 vehicle according to a first embodiment of the present teaching, in which FIG. 1(a) and (b) show the first embodiment, and (c) shows an example of the conventional art for comparison [FIG. 21 A cross-sectional view showing on an enlarged scale an engine unit of an MT-type straddled vehicle according to a second embodiment of the present teaching [FIG. 3] A cross-sectional view of a starter generator of an MT-type straddled vehicle according to a third embodiment of the present teaching, showing a cross-section orthogonal to the rotation axis line of the starter generator [FIG. 41 A left side view showing on an enlarged scale an engine unit of 10 an MT-type straddled vehicle according to the third embodiment of the present teaching [FIG. 51 A cross-sectional view showing on an enlarged scale a starter generator of an engine unit of an MT-type straddled vehicle according to a sixth embodiment of the present teaching [FIG. 61 A cross-sectional view showing on an enlarged scale a starter generator of an engine unit of an MT-type straddled vehicle according to a seventh embodiment of the present teaching [FIG. 7] A cross-sectional view showing on an enlarged scale a starter generator of an engine unit of an MT-type straddled vehicle according to an 20 eighth embodiment of the present teaching [FIG. 81 A cross-sectional view showing on an enlarged scale a starter generator 40 of an engine unit of an MT-type straddled vehicle according to a seventh embodiment of the present teaching [FIG. 91 A cross-sectional view showing on an enlarged scale a starter 25 generator of an engine unit of an MT-type straddled vehicle according to a tenth embodiment of the present teaching [FIG. 101 A cross-sectional view showing on an enlarged scale a starter generator of an engine unit EU of an MT-type straddled vehicle according to an eleventh embodiment of the present teaching [FIG. 11] A left side view of an MT-type straddled vehicle according to a twelfth embodiment of the present teaching

Description of Embodiments

[0055] In the following, the present teaching will be described with reference to 35 the drawings.

[0056] [First Embodiment] FIG. 1 is a diagram showing a configuration of an MT-type straddled vehicle 1 according to a first embodiment of the present teaching.

In Description and Drawings of the present application. F represents forward of the MT-type straddled vehicle 1. B represents backward of the 5 MT-type straddled vehicle 1. FB represents forward-backward direction of the MT-type straddled vehicle 1. U represents upward of the MT-type straddled vehicle 1. D represents downward of the MT-type straddled vehicle 1. UD represents upward-downward direction of the MT-type straddled vehicle 1. L represents leftward of the MT-type straddled vehicle 1. R represents 10 rightward of the MT-type straddled vehicle 1. LR represents left-right direction of the MT-type straddled vehicle 1. LR is equal to the axial direction of a crankshaft of the MT-type straddled vehicle 1. In other words, the axial direction LR of the crankshaft of the MT-type straddled vehicle 1 includes both the rightward R and the leftward L of the MT-type straddled vehicle 1.

[0057] FIG. 1(a) is a left side view of the MT-type straddled vehicle 1 according to an embodiment of the present teaching. The MT-type straddled vehicle 1 shown in FIG. 1(a) includes a vehicle body 5, an engine 20, a driving wheel 15, a multistage transmission 30, and a starter generator 40. FIG. 1(b) enlarges a part of the starter generator 40 of the MT-type straddled vehicle 1 according to this embodiment. FIG. 1(c) shows a comparative example, enlarging a part of a starter generator of a conventional MT-type straddled vehicle according to PTL 2.

The engine 20 includes a crankshaft 21, a crankcase 22, a bearing 23, and a power output part 24. The crankshaft 21 outputs power. The crankcase 22 accommodates the crankshaft 21. The bearing 23 is disposed in the crankcase 22, and supports the crankshaft 21 rotatably. The engine 20 is attached to the vehicle body 5. In FIG. 1(b) and (c), C represents the axial direction of the crankshaft. Here, inward in the axial direction of the crankshaft 21 refers to a direction toward the center of the vehicle body 5 in the axial direction of the crankshaft 21. Outward in the direction in which the axis of the crankshaft 21 extends refers to a direction toward the outside of the vehicle body 5 in the axial direction of the crankshaft 21.

The power output part 24 is disposed on the crankshaft 21 between the starter generator 40 and the bearing 23 in the axial direction of the crankshaft 35 21 in such a manner that the power output part 24 rotates integrally with the crankshaft 21. The power output part 24 is engaged with a power transmission element 241 such that power partly received from the crankshaft 21 is outputted to an auxiliary component 261 (see FIG. 2) of the engine 20. The power transmission element 241 is a member for transmitting rotation of the crankshaft 21 to the auxiliary component 261 of the engine 20. In this embodiment, the power output part 24 is a cam chain sprocket, the power transmission element 241 is a cam chain, and the auxiliary component 261 is a valve operating mechanism.

The driving wheel 15 receives power outputted from the engine 20, to drive the MT-type straddled vehicle 1. The multistage transmission 30, which 10 is accommodated in the crankcase 22, changes the gear ratio between the speed of the crankshaft 21 and the driving wheel 15 in multiple stages.

[0058] The starter generator 40 has a function to start the engine 20, and a function to be driven by the engine 20 to generate electricity. The starter generator 40 includes a stator 41 and a rotor 42. The stator 41 is directly or indirectly fixed to the vehicle body 5 with the relative position of the stator 41 to the vehicle body 5 maintained. The stator 41 has a stator core 411 and windings 413 of plural phases, the stator core 411 including plural teeth 412 disposed apart from one another by slots in the circumferential direction, the windings 413 being wound on the teeth 412. The rotor 42 is attached to an end portion of the crankshaft 21 so as to rotate together with the crankshaft 21. The rotor 42 has permanent magnet parts 421 disposed outside the stator 41 in the axial direction of the crankshaft 21, the permanent magnet parts 421 being arranged in the circumferential direction so as to be opposed to the stator 41 with a spatial gap therebetween. The rotor 42 is configured to cover the inner side of the stator 41 in the axial direction of the crankshaft 21, and to be supported by the crankshaft 21.

In this embodiment, the starter generator 40 is a motor of outer rotor type. In this embodiment, the rotor 42 has a bottomed cylinder shape that is open outward in the axial direction of the crankshaft 21.

The crankshaft 21 has a straight portion 211 and a tapered portion 212.

The straight portion 211 has the power output part 24 disposed thereat. The tapered portion 212, which has a tapered shape that gradually tapers from an outward end 211a of the straight portion 211, has the rotor 42 disposed thereat. [0059] The rotor 42 having a bottomed cylinder shape that is open outward in the axial direction of the crankshaft 21 can be connected to the crankshaft 21 at a position closer to the bearing as compared to, for example, a rotor having a bottomed cylinder shape that is open inward in the axial direction of the crankshaft 21. In addition, a portion of the crankshaft 21 protruding from the bearing 23 can be shortened. This can suppress a shift of the rotation axis line when the crankshaft 21 rotates, which may otherwise be caused by a shaking of the center of gravity of the crankshaft 21 and the rotor 42 because of a tolerance and the like, for example.

[0060] A structure of the starter generator 40 in the MT-type straddled vehicle 1 according to this embodiment will now he described by comparison with an example of the conventional art shown in FIG. 1(c). In all the embodiments described below, the bearing width is the average value of widths of plural bearings in the axial direction of the crankshaft, the plural bearings supporting the crankshaft. In the drawings showing the embodiments described below, however, only one bearing of the plural bearings supporting the crankshaft is shown, the one bearing being closest to the starter generator. These drawings are on the assumption that all the bearings supporting the crankshaft have equal widths in the axial direction of the crankshaft. Thus, it should be noted that the bearing widths (X and X' below) in the drawings are shown on the basis of the width of the bearing closest to the starter generator.

[0061] The starter generator 40 is capable of increasing its output by (0 reducing the spatial gap between the permanent magnet parts of the rotor and the teeth of the stator core in the radial direction. In the MT-type straddled vehicle of this embodiment, as shown in FIG. 1(b), an outward end 42a of the rotor 42 is located between an outward position 20a and an inward position 20b. Here, the outward position 20a refers to a position located farther in the outward direction than an outward end 21a of the crankshaft 21 by a distance corresponding to the width X of the hearing 23 in the axial direction of the crankshaft 21. The inward position 20b refers to a position located farther in the inward direction than the outward end 21a of the crankshaft 21 by a distance corresponding to the width X of the bearing 23 in the axial direction of the crankshaft 21. That is, in the axial direction of the crankshaft 21, a distance W between the outward end 42a of the rotor 42 and the outward end 21a of the crankshaft 21 is shorter than the width X of the bearing 23. In the comparative example shown in FIG. 1(c), on the other hand, a conventional rotor 142 has its outward end 142a located farther in the outward direction than an outward position 120a in the axial direction of a crankshaft 121. That is, in the axial direction of the crankshaft 121, a distance W' between the outward end 142a of the conventional rotor 142 and an outward end 121a of the crankshaft 121 is longer than a width X' of a bearing 123. Accordingly, the starter generator 40 of the MT-type straddled vehicle 1 according to this embodiment is configured such that the distance from an outward end 23a of the outermost bearing 23 of the plural bearings 23 supporting the crankshaft 21 to the outward end 42a of the rotor 42 is shorter than that of the comparative example shown in FIG. 1(c).

[0062] Preferably, the distance from the outward end 23a of the outermost hearing 23 of the plural hearings 23 supporting the crankshaft 21 to the outward end 42a of the rotor 42 is shortened in the axial direction of the crankshaft 21. Shortening the distance from the outward end 23a of the outermost bearing 23 of the plural bearings 23 supporting the crankshaft 21 to the outward end 42a of the rotor 42 can suppress a shaking of the rotation axis at a time of rotation, which may otherwise be caused by a tolerance and the like.

That is, a shaking amplification of the position of the permanent magnet parts 421 in the radial direction can be suppressed. Accordingly a fluctuation that is likely to occur in the spatial gap between the permanent magnet parts 421 of the rotor 42 and the teeth 412 of the stator core 411 in the radial direction can be reduced, the fluctuation that is likely to occur being caused by a shaking of the rotation axis. Consequently, the permanent magnet parts 421 of the rotor 42 can be arranged close in the radial direction to the teeth 412 of the stator core 411. This gives the starter generator an increase in output.

Thus, in the starter generator 40 of the MT-type straddled vehicle 1 according to this embodiment, (0 the spatial gap between the permanent magnet parts 421 of the rotor 42 and the teeth 412 of the stator core 411 can be reduced in the radial direction, as compared to the comparative example shown in FIG. 1(c). Thus, the starter generator 40 of the MT-type straddled vehicle 1 according to this embodiment is given an increase in output as compared to the comparative example shown in FIG. 1(c).

[0063] In addition, the starter generator 40 is given an increase in output by (ii) increasing the thickness of the teeth of the stator core in the axial direction. In the MT-type straddled vehicle according to this embodiment, as shown in FIG. 100, a width Y of the teeth 412 of the stator core 411 in the axial direction of the crankshaft 21 is larger than the width X of the bearing 23 in the axial direction of the crankshaft 21. In a conventional stator 141 according to the comparative example shown in FIG. 1(c), on the other hand, a stator core 1411 has teeth 1412 whose width Y' in the axial direction of the crankshaft is smaller than the width X' of the bearing 123 in the axial direction of the crankshaft. Thus, in the starter generator 40 of the MT-type straddled vehicle 1 according to this embodiment, (ii) the thickness of the teeth 412 of the stator core 411 is increased as compared to the comparative example shown in FIG. 1(c).

A starter generator is rotated by a magnetic field repelling and attracting permanent magnet parts of a rotor, the magnetic field being produced by an electric current flowing through windings of a stator.

Increasing the thickness of teeth of a stator core allows magnetic fluxes flowing in the teeth to increase. Even though, therefore, the permanent magnet parts of the rotor are made larger so that magnetic fluxes come from the permanent magnet parts of the rotor is allowed to increase, ineffective magnetic fluxes, that is, magnetic fluxes that don't flow into the teeth of the stator core, can be reduced. Accordingly, making the width of the stator core larger than the width of a bearing makes it possible to increase the thickness of the teeth of the stator core, which gives the starter generator an increase in output.

In the starter generator 40 of the MT-type straddled vehicle 1 according to this embodiment, therefore, the starter generator 40 is given an increase in output as compared to the comparative example shown in FIG. 1(c). The starter generator 40 is rotated by a magnetic field repelling and attracting permanent magnets of the rotor 42, the magnetic field being produced by an electric current flowing through the windings 413 of the stator 41. Increasing the thickness of the teeth 412 of the stator core 411 in the axial direction of the crankshaft 21 allows magnetic fluxes flowing in the teeth 412 to increase. Even though, therefore, the permanent magnet parts 421 of the rotor 42 are made larger so that magnetic fluxes come from the permanent magnet parts 421 of the rotor 42 is allowed to increase, ineffective magnetic fluxes, that is, magnetic fluxes that don't flow into the teeth 412 of the stator core 411, can be reduced because of the increased thickness of the teeth 412 in the axial direction of the crankshaft 21.

[0064] Furthermore, in the crankshaft 21 of the MT-type straddled vehicle 1, a shaking of the rotation axis when the rotor rotates can be suppressed by (iii) reducing the distance from the outward end of the bearing to the inward end of the rotor. In the MT-type straddled vehicle 1 according to this embodiment, as shown in FIG. 1(b), the crankshaft 21 is formed such that a distance Z from an outward end 24a of the power output part 24 to an inward end 212b of the tapered portion 212 is shorter than the width X of the bearing 23 in the axial direction of the crankshaft 21. In the comparative example shown in FIG. 1(c), on the other hand, the conventional crankshaft 121 is formed such that a distance Z' from an outward end 124a of a power output part 124 to an inward end 1212b of a tapered portion 1212 is longer than the width X' of the bearing 123 in the axial direction of the crankshaft 21. Thus, in the starter generator 40 of the MT-type straddled vehicle 1 according to this embodiment, (iii) the distance from the outward end 23a of the bearing 23 to the outward end 42a of the rotor 42 is reduced as compared to the comparative example shown in FIG. 1(c). The cam chain sprocket serving as the power output part 24 is disposed between the outward end 23a of the bearing 23 and the inward end 212b of the tapered portion 212 in the axial direction of the crankshaft 21. Therefore, making the distance Z from the outward end 24a of the power output part 24 to the inward end 212b of the tapered portion 212 shorter than the width of the bearing 23 can shorten the distance between the outward end 23a of the bearing 23 and the inward end 212b of the tapered portion 212. This allows the outward end 42a of the rotor 42 to be closer to the outward end 23a of the bearing 23. Since the distance between the outward end 23a of the bearing 23 and the inward end 212b of the tapered portion 212 can be shortened, it is possible to obtain a distance from the outward end 21a of the crankshaft 21 to the inward end 212b of the tapered portion 212 of the crankshaft 21. This can suppress shortening, in the axial direction of the crankshaft 21, of the width of a portion serving as a weight of the rotor 42 attached to the crankshaft 21, and consequently the crankshaft 21 can be given a greater moment of inertia.

[0065] In the MT-type straddled vehicle 1, as shown in FIG. 1(b), the outward end 42a of the rotor 42 is closer to the outward end 23a of the bearing 23, which makes it possible to increase the thickness of the teeth 412 of the stator core 411 while suppressing outward protrusion of the rotor 42. That is, in the axial direction of the crankshaft 21, the outward end 42a of the rotor 42 can be disposed between the outward position 20a and the inward position 20b relative to the outward end 21a of the crankshaft 21, and at the same time the width (thickness) of the stator core 411 can be larger than the width of the bearing 23.

Accordingly the MT-type straddled vehicle 1 can satisfy both of the conditions (i) and (ii) by satisfying the condition (iii). This is because even though the thickness of the stator 41 is increased or the size of the permanent magnet parts 421 is increased, an increase in a shaking amplification of the rotation axis can be suppressed, so that an increase in the spatial gap between the permanent magnet parts 421 and the teeth 412 can be suppressed.

Consequently, in the MT-type straddled vehicle 1, a size increased of the engine 20 can be suppressed, a greater moment of inertia can be obtained, and the starter generator 40 serving also as a generator can be realized in order to give an increase in output.

[0066] [Second Embodiment] An MT-type straddled vehicle according to a second embodiment will be described. An engine 20, a multistage transmission 30, and a starter generator 40 (hereinafter, collectively referred to also as engine unit EU1) of the second embodiment are ones according to the first embodiment, but are further configured as follows. FIG. 2 is a cross-sectional view showing on an enlarged scale the engine unit EU1 of an MT-type straddled vehicle 2 according to the second embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle 2 according to the second embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a) and (b).

[0067] An engine 20 includes a crankcase 22, a cylinder 25, and a cylinder head 26. The crankcase 22, the cylinder 25, and the cylinder head 26 constitute a housing of the engine unit EU1. The crankcase 22 and the cylinder head 26 are connected to the cylinder 25.

The engine 20 includes a piston 251, a connecting rod 252, and a spark 25 plug 262. The piston 251 is reciprocably disposed in the cylinder 25. The piston 251 and the crankshaft 21 are coupled to each other via the connecting rod 252. An auxiliary component 261 is disposed in the cylinder head 26.

[0068] The multistage transmission 30 includes a clutch 31, an input shaft 32, an output shaft 33, driving gears 34, driven gears 35, dog rings 35a, a gear stage setting mechanism 36, an output unit 37, and a shift pedal 39. The multistage transmission 30 converts the rotation speed of the crankshaft 21 at a gear ratio according to a manipulation on the shift pedal 39, and outputs a resultant. The shift pedal 39 is manipulated with a driver's foot.

[0069] The clutch 31 blocks power transmission between the engine 20 and a 35 driving wheel 15 (see FIG. 1(a)), in response to a manipulation on a clutch lever 19. More specifically, the clutch 31 blocks power transmission between the crankshaft 21 and the input shaft 32. The clutch 31 blocks power transmission in response to a driver's manipulation on the clutch lever 19. The clutch 31 is connected to the clutch lever 19 via a mechanical wire 191 and a clutch operating mechanism 311.

[0070] The plural driving gears 34, which are provided to the input shaft 32, are configured to always rotate together with the input shaft 32. Each of the plural driving gears 34 corresponds to each gear stage. The plural driven gears 35, which are provided to the output shaft 33, are configured to be able to rotate relative to the output shaft 33. The dog rings 35a, which are provided to the output shaft 33, are configured to rotate together with the output shaft 33. The plural driven gears 35 are configured to be able to mesh with the corresponding driving gears 34, respectively At least one of the plural driven gears 35 constantly meshes with the corresponding driving gear 34. The output unit 37 is fixed to the output shaft 33. Power received by the output shaft 33 is outputted through the output unit 37.

[00711 The gear stage setting mechanism 36 is configured to mechanically and selectively an effective power transmission from the input shaft 32 to the output shaft 33 via a driving gear 24 and a driven gear 35 each associated with any one of the gear stages. The gear stage setting mechanism 36 includes a shift cam and a shift fork (both not shown). When the shift cam rotates in response to a driver's manipulation on the shift pedal 39, the shift fork is guided to a cam groove provided in the shift cam, to move the dog ring 35a in the axial direction. Both the driven gear 35 and the dog ring 25a have dogs. As the dog ring 35a moves in the axial direction for example, the dog provided in the driven gear 35 and the dog provided in the dog ring 35a are engaged. Consequently, a power transmission associated with any of the gear stages becomes effective. This is how the multistage transmission 30 changes the gear ratio in response to a driver's manipulation on the shift pedal 39. The rotation speed of the crankshaft 21 is converted at a gear ratio according to the manipulation on the shift pedal 39, and is outputted from the output unit 37. [0072] The rotor 42 of the starter generator 40 includes a back yoke part 423 having a cylindrical shape, a bottom wall part 424 having a disc-like shape, and a boss part 425 having a cylindrical shape, the bottom wall part 424 extending continuously from the back yoke part 423, the boss part 425 being interposed between the bottom wall part 424 and the crankshaft 21. The back yoke part 423, the bottom wall part 424, and the boss part 425 constitute a rotor main body 427. A gap between the bottom wall part 424 and the permanent magnet parts 421 is filled with a resin 421a. Otherwise, the boundary between the bottom wall part 424 and the back yoke part 423 would interfere with corners of the permanent magnet parts 421 to hinder the permanent magnet parts 421 from being formed in contact with the back yoke part 423.

[0073] [Third Embodiment] An MT-type straddled vehicle according to a third embodiment will be described. A stator 41 and a rotor 42 of a starter generator 40 of the second embodiment are ones according to the first or second embodiment, but are further configured as follows. FIG. 3 is a cross-sectional view of a starter generator 40 of an MT-type straddled vehicle 3 according to the second embodiment of the present teaching, showing a cross-section orthogonal to the rotation axis line of the starter generator 40. As for the other configurations, there is no difference between the MT-type straddled vehicle 3 according to the third embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a) and (b).

[0074] The starter generator 40 is provided to a crankshaft 21. The starter generator 40 is a three-phase brushless motor of a permanent magnet type. The starter generator 40 functions as a three-phase brushless type generator of 20 a permanent magnet type.

[0075] The starter generator 40 includes a stator 41 and a rotor 42. The starter generator 40 is of a radial gap type. The starter generator 40 is of an outer rotor type. That is, the rotor 42 is an outer rotor. The stator 41 is an inner stator.

[0076] The stator 41 has plural teeth 412 extending integrally and radially outward from a stator core 411. In this embodiment, for example, eighteen teeth 412 in total are disposed at spatial gaps in the circumferential direction. In other words, in this embodiment, for example, the stator core 411 has eighteen slots 414 in total formed at spatial gaps in the circumferential direction. The teeth 412 are arranged at equal spatial gaps in the circumferential direction.

[0077] The rotor 42 has a rotor main body 427 made of a ferromagnetic material, for example. The rotor 42 has a bottomed cylinder shape connected to the crankshaft 21 at a location between the stator 41 and bearings 23 of an engine 20 in the axial direction in which the crankshaft 21 extends. The rotor main body 427 is fixed to the crankshaft 21. The rotor 42 does not have a winding to which an electric current is supplied.

The rotor 42 has permanent magnet parts 421 being opposed to the stator 41 with a spatial gap therebetween. The permanent magnet parts 421 are disposed on an inner circumferential surface of the rotor main body 427.

The permanent magnet parts 421 form plural magnetic pole faces 422. Alternatively, it may be possible that the permanent magnet parts 421 are formed by a single permanent magnet magnetized to have plural magnetic pole pairs.

[0078] The plural magnetic pole faces 422 are disposed such that N-poles and S-poles alternately appear in the circumferential direction of the starter generator 40. In this embodiment, the number of magnetic pole faces 422 included in the rotor 42 be opposed to the stator 41 is twenty-four, for example. The number of magnetic pole faces included in the rotor 42 means the number of magnetic pole faces 422 being opposed to the stator 41. There is no magnetic material provided between the magnetic pole faces 422 and the stator 41. The magnetic pole faces 422 are disposed further in the outward direction than the stator 41 in the radial direction of the starter generator 40.

[0079] The number of magnetic pole faces 422 included in the rotor 42 is greater than the number of teeth 412. Thus, the starter generator 40 has the magnetic pole faces 422 greater in number than the teeth 412. In this embodiment, the number of magnetic pole faces 422 is 4:3 of the number of slots, for example.

[0080] Each of the teeth 412 has a winding 413 wound therearound. In other words, the windings 413 of plural phases are disposed so as to be through the slots 414. FIG. 3 shows a state where the windings 413 reside in the slots 414. Each of the windings 413 of plural phases belongs to any of U-phase, V-phase, and W-phase. The windings 413 are arranged in the order of U-phase, V-phase, and W-phase, for example.

[0081] The rotor 42 is attached to the crankshaft 21 not via a power transmission mechanism (such as a belt, a chain, a gear, a speed-reducing gear, or a speed-increasing gear), as shown in FIG. 3 for example. The rotor 42 rotates at a speed ratio of 1:1 relative to the crankshaft 21. More specifically, the rotor 42 is connected to the crankshaft 21 so as to rotate at the same speed as that of the crankshaft 21. The rotation axis line of the starter generator 40 and the rotation axis line of the crankshaft 21 are substantially coincident with each other. More specifically, the rotor 42 is fixed to the crankshaft 21. Still more specifically, the rotor 42 is directly connected to the crankshaft 21. The rotor 42 rotates integrally with the crankshaft 21, therefore. The rotation axis of the starter generator 40 is integrated with the crankshaft 21.

[0082] In this embodiment, the ratio of the number of magnetic pole faces the number of slots included in the starter generator 40 is greater than 2:3. This suppresses generation of an electric current at a time of high rotations when the starter generator 40 operates as a generator. This can consequently suppress a rise in the temperature of the windings 413 at a time of high rotations. Accordingly, the in MT-type straddled vehicle 1 according to this embodiment, heat generation by the starter generator 40 can be suppressed, while the starter generator 40 allows to be given an increase in output. For example, the need for a structure (such as a fan, a heat sink, or the like) for cooling the starter generator 40 can be eliminated. Accordingly, in the MT-type straddled vehicle 1 according to this embodiment, a size increase of the engine 20 can he suppressed, a greater moment of inertia can be obtained and the starter generator 40 can be realized in order to give an increase in output. [0083] [Fourth Embodiment] An MT-type straddled vehicle according to a fourth embodiment will be described. An engine unit of the fourth embodiment is one according to any of the first to third embodiments, but is further configured as follows. FIG. 4 is a left side view showing on an enlarged scale an engine unit EU4 of an MT-type straddled vehicle 4 according to the fourth embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle 4 according to the fourth embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a) and (b).

[0084] The engine unit EU4 includes an engine 20, a multistage transmission 30, and a starter generator 40. A crankshaft 21 of the engine 20, the multistage transmission 30, and the starter generator 40 are arranged in a crankcase 22. The crankshaft 21 is rotatably supported by the crankcase 22.

Power of the crankshaft 21 is transmitted to a valve operating mechanism, which is an auxiliary component 261, via a cam chain sprocket serving as a power output part 24 and a cam chain serving as a power transmission element 241.

[0085] The crankcase 22 is configured such that its inside is lubricated with an 35 engine oil (hereinafter, referred to as oil OL). The engine 20 has the oil OL. The crankshaft 21, the multistage transmission 30, and the starter generator are lubricated with the same oil OL. The oil OL lubricates and cools each part of the engine unit EU4.

The oil OL is forcibly fed by an oil pump (not shown), to circulate through the engine unit EU4. More specifically, the oil OL is accumulated in an oil pan 221, which is disposed in a lower part of the crankcase 22. The oil OL accumulated in the oil pan 221 is pressurized by an oil pump (not shown). The oil OL thus pressurized is supplied to the engine 20 through an oil supply passage (not shown).

[0086] The oil OL is supplied to the multistage transmission 30 and the starter generator 40, too. Here, in this embodiment, the rotor 42 of the starter generator 40 is provided without a fan nor a fin for producing an air stream for cooling. The rotor 42 is disposed at a position where the rotor 42 is in contact with the oil OL. The oil OL is accumulated such that the starter generator 40 is partially immersed in the oil OL. For example, a damming wall (not shown) is disposed so as to surround a part of the starter generator 40, and the oil OL is accumulated therein, so that the starter generator 40 is partially immersed in the oil OL. The oil OL, if overflowing beyond the damming wall, flows to the oil pan 221, for example. As the starter generator 40 rotates, the oil OL adhered to the starter generator 40 is dispersed in the inside of the crankcase 22.

In this embodiment, heat dissipation can be carried out by the oil OL of the starter generator 40. Accordingly, in the MT-type straddled vehicle 1 according to this embodiment, the starter generator 40 can give an increase in output while a size increase of a cooling mechanism can be suppressed or avoided. In the MT-type straddled vehicle 4 according to this embodiment, therefore, a size increase of the engine 20 can be suppressed, a greater moment of inertia can be obtained, and the starter generator 40 can be realized in order to give an increase in output.

[0087] The oil OL may be a low-viscosity oil, for example. To be specific, the oil OL is a lubrication oil whose low temperature viscosity grade is lower than 20W according to the SAE viscosity classification specified in SAE J300. The lower the viscosity grade is, the lower the oil viscosity is. There is no particular limitation on the high temperature viscosity grade according to the SAE viscosity classification on the lubrication oil. The SAE viscosity grade on the lubrication oil is expressed by XW-Y, where X is an integer of 0 or more but less than 20, and Y is an integer of 0 or more. The lubrication oil includes a base oil and an additive. Roughly speaking, as a lubrication oil has a lower viscosity, the lubrication oil has a lower evaporation temperature, and the lubrication oil is more likely to be evaporated. Lubrication oils having the same viscosity may sometimes have different evaporation temperatures depending on types of base oils (for example, whether the base oil is a mineral oil or a synthetic oil) and/or additives. Evaporation characteristics of the lubrication oil can be obtained through a boiling point distribution measurement process using a gas chromatography simulated distillation in compliance with ASTM D6352, for example.

[0088] [Fifth Embodiment] An MT-type straddled vehicle according to a fifth embodiment will he described. A starter generator 40 of the fifth embodiment is one according to the third or fourth embodiment, but is configured to output power at least when an engine 20 is in combustion operation. More specifically, the starter generator 40 is supplied with electricity and drives a crankshaft 21, even after the engine 20 starts. With this configuration, the starter generator 40 has a function to assist an engine output of the MT-type straddled vehicle 1.

This embodiment can suppress the temperature of the starter generator 40 becoming high (see the third and fourth embodiments), and therefore the starter generator 40 can be used to assist the engine output, which makes it unnecessary to additionally provide another motor for assisting a driving force of the MT-type straddled vehicle. Accordingly, in the MT-type straddled vehicle according to this embodiment, a size increase of the engine 20 can be suppressed, a greater moment of inertia can be obtained, and the starter generator 40 can be realized in order to give an increase in output. Thus, in the MT-type straddled vehicle according to this embodiment, a size increase of the MT-type straddled vehicle can be suppressed even though an assist function to assist a driving force is additionally provided. Here, the starter generator 40 may output power when the engine 20 is not in combustion operation. As for the other configurations, there is no difference between the MT-type straddled vehicle according to the fifth embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a) and (h).

[0089] [Sixth Embodiment] An MT-type straddled vehicle according to a sixth embodiment will be 85 described. An engine unit of the sixth embodiment is one according to any of the first to fifth embodiments, but is further configured as follows. FIG. 5 is a cross-sectional view showing on an enlarged scale a starter generator 40 of an engine unit EU6 of an MT-type straddled vehicle 6 according to the sixth embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle 6 according to the sixth embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a).

[0090] The starter generator 40 is provided with a rotor position detection device 43. The rotor position detection device 43 is a device for detecting the position of a rotor 42. The rotor position detection device 43 is disposed at such a position that detection object portions 432 come to be opposed to the rotor position detection device 43 as the rotor 42 rotates. The rotor position detection device 43 has a coil type pickup coil having a winding different from windings 413 of a stator 41. The rotor position detection device 43 is attached to a crankcase 22, and is disposed in a space where the starter generator 40 is received.

[0091] In this embodiment, the position of the rotor 42 of the starter generator 40 is detected by the pickup coil having the winding. It therefore is not necessary to use a Hall IC, which is less durable to heat than the pickup coil, for example. Using a Hall IC involves the need for a structure that cools the Hall IC, for example. Accordingly, in the MT-type straddled vehicle 6 according to this embodiment, a size increase of an engine 20 can be suppressed, a greater moment of inertia can be obtained, and the starter generator 40 can be realized in order to give an increase in output.

[0092] [Seventh Embodiment] An MT-type straddled vehicle according to a seventh embodiment will be described. An engine unit of the seventh embodiment is one according to any of the first to sixth embodiments, but is further configured as follows. FIG. 6 is a cross-sectional view showing on an enlarged scale a starter generator 40 of an engine unit EU7 of an MT-type straddled vehicle 7 according to the seventh embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle 7 according to the seventh embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a). [0093] Referring to FIG. 6, the engine unit EU7 includes a crankcase cover 222 that covers at least an outward-facing portion of the starter generator 40. The engine unit EU7 shown in FIG. 6 is formed such that a spatial gap U between an outward end 41a of a stator 41 and an inner wall surface 222c of the crankcase cover 222 in the axial direction of a crankshaft 21 is larger than a width X of a bearing 23 in the axial direction of the crankshaft.

[00941 In this embodiment, the stator 41 and the crankcase cover 222 can be spaced from each other by a gap so as to avoid hindering a flow of a fluid. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover 222. Accordingly a size increase of an engine 20 can be suppressed, a temperature rise within the crankcase cover 222 can be suppressed, and the starter generator 40 can be given an increase in output.

[00951 [Eighth Embodiment] An MT-type straddled vehicle according to an eighth embodiment will be described. An engine unit of the eighth embodiment is one according to any of the first to seventh embodiments, but is further configured as follows. FIG. 7 is a cross-sectional view showing on an enlarged scale a starter generator 40 of an engine unit EU8 of an MT-type straddled vehicle 8 according to the eighth embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle 8 according to the eighth embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a).

[0096] Referring to FIG. 7, the engine unit EU8 includes a crankcase cover 222 that covers at least an outward-facing portion of the starter generator 40. The engine unit EU8 shown in FIG. 7 is formed such that a spatial gap V between an outward end 42a of a rotor 42 and an inner wall surface 222c of the crankcase cover 222 in the axial direction of a crankshaft 21 is larger than a width X of a bearing 23 in the axial direction of the crankshaft.

[00971 In this embodiment, the rotor 42 and the crankcase cover 222 can be spaced from each other by a gap so as to avoid hindering a flow of a fluid. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover 222. Accordingly, a size increase of an engine 20 can be suppressed, a temperature rise within the crankcase cover 222 can be suppressed, and the starter generator 40 can be given an increase in output.

[00981 [Ninth Embodiment] An MT-type straddled vehicle according to a ninth embodiment will be described. An engine unit of the ninth embodiment is one according to any of the first to eighth embodiments, but is further configured as follows. FIG. 8 is a cross-sectional view showing on an enlarged scale a starter generator 40 of an engine unit EU9 of an MT-type straddled vehicle 9 according to the seventh embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle 9 according to the seventh embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a).

[0099] Referring to FIG. 8, the engine unit EU9 includes a crankcase cover 222 that covers at least an outward-facing portion of the starter generator 40. The engine unit EU9 shown in FIG. 8 is formed such that a distance T from at least a portion of a back yoke part 423 of the rotor 42 to an inner wall surface 222c of the crankcase cover 222 in the radial direction of the back yoke part 423 is longer than a width X of a bearing 23 in the axial direction of a crankshaft 21. [0100] In this embodiment, the rotor 42 and the crankcase cover 222 can be at least partially spaced from each other by a gap so as to avoid hindering a flow of a fluid. This can suppress a phenomenon in which air or oil mist stays inside the crankcase cover 222. Accordingly, a size increase of an engine 20 can be suppressed, a temperature rise within the crankcase cover 222 can be suppressed, and the starter generator 40 can be given an increase in output. [0101] [Tenth Embodiment] An MT-type straddled vehicle according to a tenth embodiment will be described. An engine unit of the tenth embodiment is one according to any of the first to ninth embodiments, but is further configured as follows. FIG. 9 is a cross-sectional view showing on an enlarged scale a starter generator 40 of an engine unit EU10 of an MT-type straddled vehicle 10 according to the tenth embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle according to the tenth embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a).

[0102] Referring to FIG. 9, the engine unit EU10 is formed such that a spatial gap between an inner circumferential surface 41c of a stator 41 defining a hole through which a crankshaft 21 is received and an outer circumferential surface 425d of a boss part 425 of a rotor 42 is smaller than the length of a bearing 23 in the axial direction of the crankshaft 21.

[0103] This embodiment allows a greater amount of air or oil mist to be guided to the outside of the stator 41 in the radial direction because of the narrow spatial gap between the stator 41 and the boss part 425. This can suppress a phenomenon in which air or oil mist stays inside a crankcase cover 222. Accordingly, a size increase of an engine 20 can be suppressed, a temperature rise within the crankcase cover 222 can be suppressed, and the starter generator 40 can be given an increase in output.

[0104] [Eleventh Embodiment] An MT-type straddled vehicle according to an eleventh embodiment will be described. An engine unit of the eleventh embodiment is one according to any of the first to third embodiments and fifth to tenth embodiments, but is further configured as follows. FIG. 10 is a cross-sectional view showing on an enlarged scale a starter generator 40 of an engine unit EUll of an MT-type straddled vehicle 11 according to the eleventh embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle 11 according to the fourth embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(a).

[0105] Referring to FIG. 10, the engine unit EUll has a partition 223 disposed 10 between the starter generator 40 and a power output part 24 within a crankcase 22. The partition 223 is supported by the crankcase 22 via an oil seal 224. A crankshaft 21 extends through the partition 223.

A rotor 42 of the starter generator 40 has a fin 426 for producing an air stream for cooling. The rotor 42 is not in contact with an oil OL.

[0106] This embodiment, in which the rotor 42 of the starter generator 40 has the fin 426 for producing an air stream for cooling, suppresses a phenomenon in which air having entered the inside of a crankcase cover 222 stays within the crankcase cover 222. Accordingly, a size increase of an engine 20 can be suppressed, a temperature rise within the crankcase cover 222 can be suppressed, and the starter generator 40 can be given an increase in output.

[0107] [Twelfth Embodiment] An MT-type straddled vehicle according to a twelfth embodiment will be described. A vehicle body 5 of the twelfth embodiment is one according to any of the first to tenth embodiments, but is configured as follows. FIG. 11 is a left side view of an MT-type straddled vehicle 12 according to the twelfth embodiment of the present teaching. As for the other configurations, there is no difference between the MT-type straddled vehicle 1 according to the fourth embodiment and the MT-type straddled vehicle 1 shown in FIG. 1(b).

[0108] Referring to FIG. 11, an engine 20 of the MT-type straddled vehicle 1 is 30 attached to the vehicle body 5 with the axis of the crankshaft 21 extending in the left-right direction of the vehicle body 5.

[0109] The MT-type straddled vehicle according to this embodiment has a transverse type engine, which means the engine 20 having the crankshaft 21 whose axis extends in the left-right direction of the vehicle body 5. In the MT-type straddled vehicle 1 according to this embodiment, therefore, downsizing of the engine 20 is allowed because it is possible to arrange the engine 20 without converting the direction of an output shaft 33 of the engine 20 from the forward-backward direction FB to the left-right direction RL.

Reference Signs List [0110] 1 MT-type straddled vehicle vehicle body driving wheel engine 21 crankshaft 22 crankcase 23 bearing 24 power output part multistage transmission starter generator 41 stator 42 rotor

Claims

CLAIMS[Claim 1 An MT-type straddled vehicle comprising: a vehicle body; an engine attached to the vehicle body, the engine including a crankshaft, a crankcase, and a bearing provided to the crankcase, the crankshaft being configured to output power, the crankcase accommodating the crankshaft, the bearing supporting the crankshaft rotatably; a driving wheel that receives power outputted from the engine to drive the MT-type straddled vehicle; a multistage transmission accommodated in the crankcase, the multistage transmission being configured to change a gear ratio between the speed of the crankshaft and the driving wheel in multiple stages; and a starter generator including a rotor and a stator, the rotor being attached to an end portion of the crankshaft so as to rotate together with the crankshaft, the stator being directly or indirectly fixed to the vehicle body with the relative position of the stator to the vehicle body maintained, the starter generator having both a function to start the engine and a function to be driven by the engine to generate electricity, wherein the engine has a power output part disposed on the crankshaft between the starter generator and the bearing in an axial direction of the crankshaft in such a manner that the power output part rotates integrally with the crankshaft, the power output part being engaged with a power transmission element for transmitting rotation of the crankshaft to an auxiliary component of the engine such that power is partly outputted from the crankshaft to the auxiliary component of the engine, the stator includes a stator core and windings of plural phases, the stator core having plural teeth spaced from one another by slots in a 30 circumferential direction, the windings being wound on the teeth, the rotor has permanent magnet parts disposed outside the stator in a radial direction, the permanent magnet parts being arranged in the circumferential direction so as to be opposed to the stator with a spatial gap therebetween, the rotor being configured to cover the inner side of the stator in the axial direction of the crankshaft, and to be supported by the crankshaft, the crankshaft has a straight portion and a tapered portion, the straight portion having the power output part disposed thereon, the tapered portion having the rotor disposed thereon, the tapered portion having a tapered shape that gradually tapers from an outward end of the straight portion, and for an outward end of the rotor to be located between an outward position and an inward position in the axial direction of the crankshaft and for the teeth of the stator core to have a width larger than the width of the bearing in the axial direction of the crankshaft, the power output part and the tapered portion are formed such that a distance between an outward end of the power output part and an inward end of the tapered portion is to be shorter than the width of the bearing, the outward position being located farther in an outward direction than an outward end of the crankshaft by a distance corresponding to the width of the bearing, the inward position being located farther in an inward direction than the outward end of the crankshaft by a distance corresponding to the width of the bearing.
[Claim 2] The MT-type straddled vehicle according to claim 1, wherein the rotor has permanent magnet parts arranged in the circumferential direction so as to be opposed to the stator with a spatial gap therebetween, the 20 permanent magnet parts having magnetic pole faces, the number of which is greater than 2:3 of the number of the slots.
[Claim 3] The MT-type straddled vehicle according to claim 1 or 2, wherein the crankcase is configured such that its inside is lubricated with an oil, 25 and the starter generator includes a rotor that is provided without a fan nor a fin for producing an air stream for cooling, and is positioned so as to be in contact with the oil.
[Claim 4] The MT-type straddled vehicle according to any one of claims 1 to 3, wherein the starter generator is configured to output power at least when the engine is in combustion operation.
[Claim 5] The MT-type straddled vehicle according to any one of claims 1 to 4, wherein the starter generator has a rotor position detection device that is a pickup coil that has a winding that is different from the windings of the stator.
[Claim 6] The MT-type straddled vehicle according to any one of claims 1 to 5, 5 further comprising a crankcase cover that covers at least an outward-facing portion of the starter generator, wherein a spatial gap between the outward end of the stator and an inner wall surface of the crankcase cover in the axial direction of the crankshaft is larger than the width of the hearing.
[Claim 7] The MT-type straddled vehicle according to any one of claims 1 to 5, further comprising a crankcase cover that covers at least an outward-facing portion of the starter generator, wherein a spatial gap between the outward end of the rotor and an inner wall 15 surface of the crankcase cover in the axial direction of the crankshaft is larger than the width of the bearing.
[Claim 8] The MT-type straddled vehicle according to claim 6, wherein a spatial gap between the outward end of the rotor and the inner wall 20 surface of the crankcase cover in the axial direction of the crankshaft is larger than the width of the bearing.
[Claim 9] The MT-type straddled vehicle according to any one of claims 1 to 5, further comprising a crankcase cover that covers at least an outward-facing 25 portion of the starter generator, wherein the rotor includes a hack yoke part having a cylindrical shape, a bottom wall part having a disc-like shape, and a boss part having a cylindrical shape, the bottom wall part extending continuously from the back yoke part, the boss part being interposed between the bottom wall part and the crankshaft, and a distance from at least a portion of the back yoke part to an inner wall surface of the crankcase cover in the radial direction is longer than the width of the bearing in the axial direction of the crankshaft.
[Claim 10] The MT-type straddled vehicle according to claim 6 or 7, wherein the rotor includes a hack yoke part having a cylindrical shape, a bottom wall part having a disc-like shape, and a boss part having a cylindrical shape, the bottom wall part extending continuously from the back yoke part, the boss part being interposed between the bottom wall part and the crankshaft, and a distance from at least a portion of the back yoke part to the inner wall surface of the crankcase cover in the radial direction is longer than the width of 5 the bearing in the axial direction of the crankshaft.
[Claim 11] The MT-type straddled vehicle according to any one of claims 1 to 8, wherein the rotor includes a back yoke part having a cylindrical shape, a bottom 10 wall part having a disc-like shape, and a boss part having a cylindrical shape, the bottom wall part extending continuously from the back yoke part, the boss part being interposed between the bottom wall part and the crankshaft, and a spatial gap between an inner circumferential surface of the stator defining a hole through which the crankshaft is received and an outer 15 circumferential surface of the boss part is smaller than the width of the bearing in the axial direction of the crankshaft.
[Claim 12] The MT-type straddled vehicle according to claim 10, wherein a spatial gap between an inner circumferential surface of the stator 20 defining a hole through which the crankshaft is received and an outer circumferential surface of the boss part is smaller than the width of the bearing in the axial direction of the crankshaft.
[Claim 13] The MT-type straddled vehicle according to any one of claims 1 to 12, 25 wherein the engine is attached to the vehicle body with the axis of the crankshaft extending in a left-right direction of the vehicle body