JP7472756B2 - engine - Google Patents

Description

The present invention relates to an engine.

The engine is equipped with an engine starting device that transmits power from the starter motor to the crankshaft via a gear train. The engine is also equipped with a power transmission mechanism that transmits power from the crankshaft to the camshaft of the valve train via a timing chain. The power transmission mechanism is equipped with a chain tensioner that applies tension to the timing chain, and there are known engines in which the gear train of the engine starting device is located near the chain tensioner (see, for example, Patent Document 1). By locating the chain tensioner and the gear train close to each other, the engine can be made more compact.

Japanese Patent No. 4236656

In the engine described in Patent Document 1, the lever guide of the chain tensioner is attached by a pivot bolt, and each gear of the engine starting device is attached to a gear shaft. This increases the number of parts, which increases costs and weight. In addition, the chain tensioner and the gear train are brought closer together to make the engine more compact, but there is a demand for even more compact engines.

The present invention was made in consideration of these points, and aims to provide an engine that can reduce costs and weight while also achieving further compactness.

The engine of one aspect of the present invention is an engine in which power is transmitted from a crankshaft to a camshaft via a timing chain, and is equipped with a starter motor that starts and rotates the crankshaft, an idler gear that rotates by receiving power from the starter motor, an idler gear shaft that rotatably supports the idler gear, and a chain tensioner that applies tension to the timing chain, and the chain tensioner has a lever guide that guides the timing chain and a tensioner body that presses the lever guide against the timing chain, and the above problem is solved by the lever guide being supported swingably on the idler gear shaft.

In one aspect of the engine of the present invention, the idler gear shaft is used to support not only the idler gear but also the lever guide of the chain tensioner, thereby reducing the number of parts and reducing costs and weight. In addition, the lever guide and idler gear are attached coaxially, so that the gear train of the engine starting system can be brought closer to the peripheral parts of the timing chain, making the engine more compact.

FIG. 2 is a right side view of the engine of the present embodiment. FIG. 2 is a left side view of the engine of the present embodiment. FIG. 13 is a schematic diagram of a gear layout of a comparative example. FIG. 2 is a cross-sectional view of the engine of the present embodiment. FIG. 5 is a diagram showing the engine starting device with a part of the gear train removed from FIG. 4 . 5 is a cross-sectional view taken along line AA in FIG. 4. 5 is a cross-sectional view taken along line BB in FIG. 4.

In one embodiment of the engine of the present invention, power is transmitted from the crankshaft to the camshaft via a timing chain. The engine is provided with a starter motor that starts and rotates the crankshaft. An idler gear supported by an idler gear shaft is rotated by receiving power from the starter motor. The timing chain is guided by a lever guide of the chain tensioner, and tension is applied to the timing chain by the tensioner body pressing the lever guide against the timing chain. The idler gear shaft supports not only the idler gear but also the lever guide of the chain tensioner so that it can swing. The idler gear shaft supports both the idler gear and the lever guide, thereby reducing the number of parts and reducing costs and weight. In addition, the chain tensioner and the lever guide are attached coaxially, so that the gear train of the engine starting system can be brought closer to the peripheral parts of the timing chain, thereby realizing a compact engine.

The engine to which the lubrication structure for the power transmission mechanism of this embodiment is applied will now be described with reference to the attached drawings. Fig. 1 is a right side view of the engine of this embodiment. Fig. 2 is a left side view of the engine of this embodiment. In the following drawings, the arrow FR indicates the front of the vehicle, the arrow RE indicates the rear of the vehicle, the arrow L indicates the left side of the vehicle, and the arrow R indicates the right side of the vehicle.

As shown in FIG. 1, the engine 10 has a crankcase 11 with a vertically split structure consisting of an upper case 12 and a lower case 13. The upper case 12 is integrated with the cylinder, and a cylinder head 14 and a cylinder head cover 15 are attached to the top of the upper case 12. A valve mechanism (not shown) that operates the intake and exhaust valves is housed inside the cylinder head 14 and the cylinder head cover 15. An oil pan 16 that stores oil for lubrication and cooling is attached to the bottom of the lower case 13. A clutch cover 17 that covers the clutch (not shown) from the side is attached to the right side of the crankcase 11.

As shown in FIG. 2, a magneto cover 18 that covers the magneto (not shown) from the side is attached to the left side of the crankcase 11. A sprocket cover 19 that covers part of the drive chain (not shown) for driving the rear wheels and the drive sprocket (not shown) from the side is attached behind the magneto cover 18. A starter motor 21 that starts the engine 10 is attached above the magneto cover 18, and an oil control valve 22 that controls the oil pressure of the engine 10 is attached above the sprocket cover 19. Various power transmission mechanisms are housed inside the engine 10.

For example, as shown in the comparative example of FIG. 3, in addition to the power transmission mechanism 82 that transmits the power of the crankshaft 81 to the valve train, the inside of the engine also contains an engine starting device 91 that transmits the power of a starter motor 94 to the crankshaft 81. It is difficult to arrange the gear train of the engine starting device 91 in a compact manner by bringing it close to the peripheral parts of the timing chain 84 of the power transmission mechanism 82. For example, because the lever guide 93 of the chain tensioner is arranged around the timing chain 84, the gear train of the engine starting device 91 must be arranged to avoid the lever guide 93.

In the engine 10 of this embodiment, the second starter idler gear (idler gear) 45 is rotatably supported on the idler gear shaft 49, and the lever guide 51 of the chain tensioner 50 is swingably supported on this idler gear shaft 49 (see FIG. 7). By supporting the second starter idler gear 45 and the lever guide 51 on a single idler gear shaft 49, a compact arrangement is realized in which the peripheral parts of the timing chain 34 of the power transmission mechanism 30 and the gear train of the engine starting device 40 are close to each other. In addition, the number of parts of the engine 10 can be reduced.

The power transmission mechanism in the engine and the engine starting device will be described with reference to Figures 4 and 5. Figure 4 is a cross-sectional view of the engine of this embodiment. Figure 5 is a view of Figure 4 with a part of the gear train of the engine starting device removed.

As shown in Figures 4 and 5, the engine 10 houses a power transmission mechanism 30 that transmits power from the crankshaft 25 to a pair of camshafts 36a, 36b of a valve train (not shown). The power transmission mechanism 30 is a semi-cam gear train that combines gear transmission and chain transmission, and connects a chain idler gear (another idler gear) 31 and a pair of cam sprockets 35a, 35b with a timing chain 34 to move the pair of camshafts 36a, 36b. A chain drive gear 26 (see Figure 5) is provided on the crankshaft 25, located inside the starter clutch gear 27 in the engine width direction, and power is transmitted from the chain drive gear 26 to the chain idler gear 31.

The chain idler gear 31 is integrally formed with a large diameter gear 32 located on the inside in the engine width direction and a small diameter gear 33 located on the outside in the engine width direction. The large diameter gear 32 is connected to the chain drive gear 26, and the large diameter gear 32 rotates by receiving power from the crankshaft 25 through the chain drive gear 26. The lower part of the timing chain 34 is hung on the small diameter gear 33, and the upper part of the timing chain 34 is hung on a pair of cam sprockets 35a, 35b. The large diameter gear 32 and the small diameter gear 33 rotate together, causing the timing chain 34 to move in a circle, and rotating the camshafts 36a, 36b connected to the pair of cam sprockets 35a, 35b.

The timing chain 34 is guided by a lever guide 51 and a chain guide 52. The timing chain 34 sent from the small diameter gear 33 to the cam sprocket 35a is guided by the lever guide 51, and the timing chain 34 drawn from the cam sprocket 35b to the small diameter gear 33 is guided by the chain guide 52. Since slack occurs in the timing chain 34 going from the small diameter gear 33 to the cam sprocket 35a, the lever guide 51 is pressed against the timing chain 34 by the tensioner body 53, applying tension to the timing chain 34. The lever guide 51 and the tensioner body 53 form a chain tensioner 50.

The chain idler gear 31 is supported by the idler gear shaft 37 via a bearing 38. The idler gear shaft 37 is supported by the upper case 12 and the clutch cover 17 (see FIG. 1). One end of the idler gear shaft 37 penetrates the side wall of the upper case 12 and protrudes into the cylinder bore 61 (see FIG. 6). An oil passage 71 is formed in the idler gear shaft 37 in the axial direction, and oil is guided from the cylinder bore 61 to the bearing 38 by the oil passage 71. The lubrication structure of the bearing 38 by the oil passage 71 in the idler gear shaft 37 will be described later.

In addition, an engine starting device 40 that transmits power from the starter motor 21 to the crankshaft 25 is housed inside the engine 10. The engine starting device 40 transmits power from the starter motor 21 to the crankshaft 25 via a gear train. The starter motor 21 starts and rotates the crankshaft 25 until the engine 10 can operate autonomously. The starter motor 21 is attached to the upper part of the left side surface of the upper case 12 at a position behind the cylinder. A pinion gear 42 is formed on the output shaft of the starter motor 21, and a first starter idler gear 43 is connected to the pinion gear 42.

A limiter gear 44 is supported on the idler gear shaft 48 of the first starter idler gear 43. The limiter gear 44 is spaced apart from the first starter idler gear 43 in the engine width direction, and power is transmitted from the limiter gear 44 to the second starter idler gear 45. The second starter idler gear 45 is integrally formed with a large diameter gear 46 located on the outer side of the engine width direction and a small diameter gear 47 (see FIG. 7) located on the inner side of the engine width direction. The limiter gear 44 is connected to the large diameter gear 46, and the starter clutch gear 27, which is coaxial with the crankshaft 25, is connected to the small diameter gear 47.

The starter clutch gear 27 is provided with a starter one-way clutch 28, and only power transmission from the starter motor 21 to the crankshaft 25 is permitted. The starter motor 21 is connected to a second starter idler gear 45 via a pinion gear 42, a first starter idler gear 43, and a limiter gear 44, and the second starter idler gear 45 rotates upon receiving power from the starter motor 21. The starter clutch gear 27 rotates together with the second starter idler gear 45, and the crankshaft 25 starts to rotate via the starter one-way clutch 28.

The second starter idler gear 45 is rotatably supported by the idler gear shaft 49. A lever guide 51 of a chain tensioner 50 is swingably supported by the idler gear shaft 49. A pivot hole 54 (see FIG. 5) is formed in the base end (lower part) of the lever guide 51, and the idler gear shaft 49 is inserted into this pivot hole 54. Because the idler gear shaft 49 is used to support both the second starter idler gear 45 and the lever guide 51, the engine starting device 40 is brought closer to the chain tensioner 50, realizing a more compact engine 10.

In a side view of the engine, the base end of the lever guide 51 is disposed between the limiter gear 44 and the crankshaft 25 in the vertical direction. At this time, the base end of the lever guide 51 is disposed below the idler gear shaft 37 of the power transmission mechanism 30, and a part of the base end of the lever guide 51 overlaps with the chain idler gear 31 (see FIG. 5). The lever guide 51 extends upward from the idler gear shaft 49, and is disposed between the chain idler gear 31 and the limiter gear 44 in the front-rear direction. With this layout, the second starter idler gear 45 and the base end of the lever guide 51 are disposed coaxially.

Furthermore, the idler gear shafts 48, 49 of the engine starting device 40 are supported by the upper case 12 and the clutch cover 17 (see FIG. 1) in the same manner as the idler gear shaft 37 of the power transmission mechanism 30. In a side view of the engine, the pinion gear 42, the first starter idler gear 43, and the chain idler gear 31 are arranged side by side in the front-rear direction at approximately the same height. In a side view of the engine, the second starter idler gear 45 is arranged between the first starter idler gear 43 and the chain idler gear 31 in the front-rear direction, and between the chain idler gear 31 and the starter clutch gear 27 in the up-down direction.

That is, the chain idler gear 31 is disposed above the crankshaft 25, and the second starter idler gear 45 is disposed above the crankshaft 25 and behind the chain idler gear 31. Also, a portion of the second starter idler gear 45 overlaps with the large diameter gear 32 of the chain idler gear 31. As a result, in an engine 10 employing a semi-cam gear train power transmission mechanism 30, the second starter idler gear 45 of the engine starting device 40 and the chain idler gear 31 of the power transmission mechanism 30 are brought closer together, realizing a compact engine 10.

The lubrication structure of the power transmission mechanism will be described with reference to Figure 6. Figure 6 is a cross-sectional view taken along line A-A in Figure 4. Note that Figure 6 shows the piston positioned at bottom dead center.

As shown in FIG. 6, a piston 62 is disposed in a cylinder bore 61, and the piston 62 is connected to the crankshaft 25 via a connecting rod 63. An idler gear shaft 37 that is parallel to the crankshaft 25 is attached directly above the crankshaft 25. The idler gear shaft 37 is disposed to the side of the cylinder bore 61, and the chain idler gear 31 is rotatably supported on the idler gear shaft 37 via a bearing 38. One end of the idler gear shaft 37 protrudes into the cylinder bore 61 through the side wall of the upper case 12.

The idler gear shaft 37 is hollow and cylindrical, and an oil passage 71 is formed in the axial direction within the idler gear shaft 37. The upper half of one end of the idler gear shaft 37 is cut out to form an oil tray 72 that serves as the inlet of the oil passage 71. The middle part of the idler gear shaft 37 overlaps with the bearing 38, and an oil supply hole 73 that serves as the outlet of the oil passage 71 is formed in this middle part. As shown by the arrow, oil in the cylinder bore 61 is taken from the tray 72 into the oil passage 71, and oil in the oil passage 71 is supplied from the oil supply hole 73 to the bearing 38.

At this time, the top surface of the receiver 72 of the idler gear shaft 37 is open, so the oil that falls from above inside the cylinder bore 61 is received by the receiver 72. The receiver 72 has a semicircular cross section perpendicular to the axial direction of the idler gear shaft 37, making it difficult for the oil received in the receiver 72 to flow off the receiver 72. In addition, only the receiver 72 of the idler gear shaft 37 protrudes into the cylinder bore 61. For this reason, the oil running down the wall surface of the cylinder bore 61 flows smoothly into the receiver 72, and the receiver 72 efficiently collects the oil running down the wall surface of the cylinder bore 61.

The tray 72 protrudes from the lower wall surface of the cylinder bore 61 and extends further inside the cylinder bore 61 than the outer circumferential surface of the piston 62. In this case, the piston boss 65 is formed with a smaller diameter than the piston head 64, and the tray 72 fits below the piston head 64 and is brought close to the piston boss 65. In this case, the tray 72 is brought close to the piston boss 65 at a position that avoids the piston skirt 66. Each time the piston 62 descends inside the cylinder bore 61, the oil on the wall surface of the cylinder bore 61 is pushed downward and collected toward the tray 72.

In addition, at least a portion of the tray 72 is located below the piston head 64, which is located at the bottom dead center, and above the lower end of the piston boss 65. Even when the piston 62 moves up and down between the top dead center and the bottom dead center, there is no interference between the piston 62 and the tray 72. With interference between the piston 62 and the tray 72 suppressed, the idler gear shaft 37 is brought close to the piston 62, forming a compact engine 10. In addition, the oil passage 71 in the idler gear shaft 37 supplies oil from the cylinder bore 61 to the bearing 38 in the shortest distance. By increasing the amount of oil supplied to the bearing 38, the durability of the bearing 38 is improved.

The support structure of the chain tensioner's lever guide will be described with reference to Figure 7. Figure 7 is a cross-sectional view taken along line B-B in Figure 4.

As shown in FIG. 7, an idler gear shaft 49 is attached above the crankshaft 25 in parallel with the crankshaft 25. The second starter idler gear 45 is rotatably supported on the idler gear shaft 49, and a lever guide 51 of a chain tensioner 50 is swingably supported on the idler gear shaft 49. The idler gear shaft 49 is supported at both ends by the upper case 12 and the clutch cover 17, and is arranged in the order of the upper case 12, lever guide 51, second starter idler gear 45, and clutch cover 17 from the inside of the engine width direction to the outside of the engine width direction.

The idler gear shaft 49 is used to support both the second starter idler gear 45 and the lever guide 51, reducing the number of parts in the engine 10. In addition, because the idler gear shaft 49 is sandwiched between the upper case 12 and the clutch cover 17, no fastening members such as bolts are required to attach the lever guide 51 and the second starter idler gear 45. In addition, because the head of the fastening member does not protrude from the outer surface of the clutch cover 17, as would be the case if a fastening member were used instead of the idler gear shaft 49, the width of the engine is narrowed, realizing a more compact engine 10.

The lever guide 51 and timing chain 34 are sandwiched between the large diameter gear 32 of the chain idler gear 31 and the small diameter gear 47 of the second starter idler gear 45. That is, near the crankshaft 25, a chain drive gear train, such as the chain drive gear 26 and the large diameter gear 32 of the chain idler gear 31, is arranged on the inside of the lever guide 51 and the timing chain 34 in the engine width direction. A starter gear train, such as the small diameter gear 47 of the second starter idler gear 45 and the starter clutch gear 27, is arranged on the outside of the lever guide 51 and the timing chain 34 in the engine width direction.

The gear train for driving the chain and the gear train for the starter are arranged separately on the inside and outside of the engine width direction with respect to the timing chain 34. This allows the arrangement space near the crankshaft 25 to be effectively used as arrangement space for the gear train for driving the chain and the gear train for the starter. The base end of the lever guide 51 is sandwiched between the large diameter gear 32 of the chain idler gear 31 and the second starter idler gear 45, and the large diameter gear 32, the base end of the lever guide 51, and the second starter idler gear 45 are arranged closely together. This narrows the engine width and realizes a compact engine 10.

Furthermore, the chain idler gear 31, starter clutch gear 27, and second starter idler gear 45 are arranged in this order from the inside in the engine width direction to the outside in the engine width direction. The chain idler gear 31, starter clutch gear 27, and second starter idler gear 45 partially overlap in side view (see FIG. 4), and these gears are concentrated near the crankshaft 25. The idler gear shaft 37 of the chain idler gear 31, the idler gear shaft 49 of the second starter idler gear 45, and the crankshaft 25 are brought closer together, narrowing the front-to-rear length of the engine and achieving a compact engine 10.

As described above, according to this embodiment, the idler gear shaft 49 is used to support not only the second starter idler gear 45 but also the lever guide 51 of the chain tensioner 50, thereby reducing the number of parts and reducing costs and weight. In addition, the lever guide 51 and the second starter idler gear 45 are attached coaxially, so that the gear train of the engine starting system can be brought closer to the peripheral parts of the timing chain 34, thereby realizing a more compact engine 10.

In this embodiment, a semi-cam gear train that combines gear transmission and chain transmission is used as an example of the power transmission mechanism, but the power transmission mechanism may be a chain transmission mechanism that does not include an idler gear.

In addition, in this embodiment, the lever guide is supported on the idler gear shaft of the second starter idler gear, but the lever guide may be supported on the idler gear shaft of the first starter idler gear.

In addition, in this embodiment, power is transmitted from the starter motor to the crankshaft via two idler gears, but power may be transmitted from the starter motor to the crankshaft via a single idler gear or three or more idler gears.

In addition, the layout of the gears in the engine starting device and the power transmission mechanism in this embodiment is merely an example, and it is sufficient that at least the idler gear and the lever guide are supported on the same idler gear shaft.

The engine is not limited to an engine for a saddle-type vehicle, but may be applied to other vehicles, such as four-wheeled motor vehicles, buggy-type three-wheeled motor vehicles, jet skis, lawn mowers, outboard motors, and other special machinery. Note that a saddle-type vehicle is not limited to all vehicles on which a rider sits astride a seat, but also includes small scooter-type vehicles on which a rider does not sit astride a seat.

As described above, the engine (10) of this embodiment is an engine in which power is transmitted from the crankshaft (25) to the camshafts (36a, 36b) via the timing chain (34), and includes a starter motor (21) that starts and rotates the crankshaft, an idler gear (second starter idler gear 45) that rotates by receiving power from the starter motor, an idler gear shaft (49) that rotatably supports the idler gear, and a chain tensioner (50) that applies tension to the timing chain. The chain tensioner has a lever guide (51) that guides the timing chain and a tensioner body (53) that presses the lever guide against the timing chain, and the lever guide is supported by the idler gear shaft so that it can swing.

With this configuration, the idler gear shaft supports not only the idler gear but also the lever guide of the chain tensioner, which reduces the number of parts and reduces costs and weight. Also, by mounting the lever guide and idler gear coaxially, the gear train for the engine starting system can be brought closer to the peripheral parts of the timing chain, making the engine more compact.

In the engine of this embodiment, a clutch cover (17) is attached to the side of the crankcase (11) that houses the crankshaft, and the idler gear shaft is supported on both ends by the crankcase and the clutch cover. With this configuration, no fastening members such as bolts are required to attach the chain tensioner and idler gear, making it possible to narrow the engine width and make the engine more compact.

The engine of this embodiment is provided with another idler gear (chain idler gear 31) that transmits the power of the crankshaft to the timing chain, the other idler gear is disposed above the crankshaft, and the idler gear shaft is disposed above the crankshaft and behind the other idler gear. With this configuration, in a semi-cam gear train engine, the idler gear of the engine starting system and the other idler gear of the semi-cam gear train can be brought closer together to achieve a more compact engine.

In the engine of this embodiment, the other idler gear is integrally formed with a large diameter gear (32) that receives power from the crankshaft and a small diameter gear (33) to which a timing chain is attached, and the idler gear overlaps the large diameter gear when viewed from the side of the engine. With this configuration, the idler gear of the engine starting system and the other idler gears of the semi-cam gear train can be brought closer together to achieve a more compact engine.

In the engine of this embodiment, the base end of the lever guide is sandwiched between the large diameter gear and the idler gear in the engine width direction. This configuration makes it possible to narrow the engine width and make the engine more compact.

Although this embodiment has been described, other embodiments may be combinations of the above embodiments and variations in whole or in part.

The technology of the present invention is not limited to the above examples, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea.

10: Engine 11: Crankcase 17: Clutch cover 21: Starter motor 25: Crankshaft 31: Chain idler gear (other idler gear)
32: Large diameter gear 33: Small diameter gear 34: Timing chain 36a: Camshaft 36b: Camshaft 40: Engine starting device 45: Second starter idler gear (idler gear)
49: Idler gear shaft 50: Chain tensioner 51: Lever guide 53: Tensioner body

Claims (5)

An engine in which power is transmitted from a crankshaft to a camshaft via a timing chain,
a starter motor that starts and rotates the crankshaft;
an idler gear that rotates by receiving power from the starter motor;
an idler gear shaft that rotatably supports the idler gear;
a chain tensioner that applies tension to the timing chain,
The chain tensioner includes a lever guide that guides the timing chain, and a tensioner body that presses the lever guide against the timing chain,
The engine is characterized in that the lever guide is supported swingably on the idler gear shaft. The engine according to claim 1, characterized in that a clutch cover is attached to the side of the crankcase that houses the crankshaft, and the idler gear shaft is supported at both ends by the crankcase and the clutch cover. and another idler gear for transmitting the power of the crankshaft to the timing chain.
3. An engine according to claim 1 or 2, characterized in that the other idler gear is disposed above the crankshaft, and the idler gear shaft is disposed above the crankshaft and rearward of the other idler gear. the other idler gear is integrally formed with a large diameter gear that receives power from the crankshaft and a small diameter gear around which the timing chain is hung,
4. The engine according to claim 3, wherein the idler gear overlaps with the large diameter gear in a side view of the engine. The engine according to claim 4, characterized in that the base end of the lever guide is sandwiched between the large diameter gear and the idler gear in the engine width direction.

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