阅读说明：本技术 小齿轮和具有小齿轮的起动器 (Pinion and starter with pinion ) 是由 藤田达也 于 2020-01-14 设计创作，主要内容包括：一种小齿轮(20),固定到起动内燃机的起动器(10)的驱动轴(13),以抑制在曲柄启动期间产生噪音。小齿轮通过与设置于内燃机的齿圈(50)啮合而使其旋转。小齿轮(20)包括齿轮齿(21)和位于齿轮齿的径向内侧的环形中空部(22)。环形中空部收容振动吸收件(23),以吸收在齿轮齿(21)产生的振动。(A pinion gear (20) is fixed to a drive shaft (13) of a starter (10) that starts an internal combustion engine to suppress generation of noise during cranking. The pinion gear rotates by meshing with a ring gear (50) provided in the internal combustion engine. The pinion (20) includes gear teeth (21) and an annular hollow portion (22) located radially inward of the gear teeth. The annular hollow portion accommodates a vibration absorbing member (23) for absorbing vibration generated at the gear teeth (21).)

1. A pinion (20), the pinion (20) being fixed to a drive shaft (13) of a starter (10) that starts an internal combustion engine, the pinion rotating a ring gear (50) provided to the internal combustion engine by meshing with the ring gear, the pinion (20) comprising:

gear teeth (21), the gear teeth (21) being disposed on an outer periphery of the pinion gear;

a hollow (22), said hollow (22) being located radially inward of each said gear tooth; and

a shock-absorbing member (23), the shock-absorbing member (23) being stored in the hollow portion;

wherein the shock absorber has a shock absorbing characteristic higher than a portion of the pinion gear surrounding the hollow portion.

2. Pinion according to claim 1, characterised in that it further comprises a shaft hole (24) to allow the insertion of the drive shaft,

the hollow part is annular and surrounds the shaft hole.

3. Pinion according to claim 2, characterised in that it further comprises at least one connection (25) to connect a radially outer wall (22A) of said hollow portion, annular, and a radially inner wall (22B) of said hollow portion, annular, with each other, said radially outer wall acting as a radially outer part of said hollow portion and said radially inner wall acting as a radially inner part of said hollow portion.

4. A pinion according to claim 2 or 3, characterized by further comprising at least one blocking member (29) disposed in the annular hollow portion to suppress the shock absorber from moving in the circumferential direction of the pinion in the annular hollow portion.

5. Pinion according to claim 1, characterized in that said annular hollow comprises at least two cylindrical hollows (322C) arranged in the circumferential direction of the pinion for each tooth.

6. A pinion according to claim 5, characterised in that each of said at least two cylindrical hollow portions has a flattened cross-sectional shape which is longer in the circumferential direction of the pinion than in the radial direction.

7. A pinion according to any one of claims 2, 3 and 5, characterised in that said hollow comprises:

an annular interior hollow located radially inward of each of the gear teeth of the pinion gear, the annular interior hollow surrounding a shaft bore; and

at least two backside hollows at respective locations of a backside of the gear tooth facing the top land and the tooth face.

8. Pinion according to any of claims 2, 3 and 5, characterized in that said annular hollow comprises:

a first hollow portion (722D), said first hollow portion (722D) being located radially inward of each of said gear teeth of said pinion gear, said first hollow portion surrounding a shaft hole;

at least two second hollows (722E), said at least two second hollows (722E) being located at respective positions of the gear teeth facing the rear sides of the top land and the tooth face; and

a partition (28), the partition (28) extending in a circumferential direction to separate the first hollow and the at least two second hollows from each other.

9. A pinion according to any one of claims 1 to 3, 5 and 6, characterised in that the shock absorber comprises a powder.

10. Pinion according to claim 9, characterised in that said powder is a mixture of two or more different particle sizes.

11. The pinion according to claim 1, wherein a particle size of the powder stored as the shock absorber in the vicinity of a wall surrounding the hollow portion of the ring shape is different from a particle size of the powder stored in the core portion of the hollow portion of the ring shape,

the core portion corresponds to the vicinity of the center of the cross section of the hollow portion of the ring shape,

the particle size of the powder stored near the wall is larger than the particle size of the powder stored in the core of the hollow portion.

12. Pinion according to one of claims 1 to 8, characterised in that the shock absorber comprises a liquid.

13. A starter for starting an internal combustion engine comprising a transmission, characterized in that the transmission comprises a pinion according to any one of claims 1 to 12.

Technical Field

Embodiments of the present invention relate to a pinion gear for starting an internal combustion engine and a starter having the pinion gear.

Background

To start the internal combustion engine, the starter drives an electric motor that rotates a pinion gear that meshes with a ring gear attached to the internal combustion engine. However, when the pinion gear is meshed with the ring gear, teeth of these gears collide with each other and generate collision noise or the like. In order to suppress such noise, various prior arts have been proposed.

Disclosure of Invention

Thus, one aspect of the present invention provides a novel pinion gear (20) secured to a drive shaft (13) of a starter (10) for starting an internal combustion engine. The pinion gear rotates a ring gear (50) provided in the internal combustion engine by meshing with the ring gear (50). The pinion (20) includes gear teeth (21) arranged on the outer peripheral surface thereof, a hollow portion (22) located inside the gear teeth, and a shock absorbing member (23) stored in the annular hollow portion. The shock absorber has a shock absorbing property higher than that of a portion of the pinion gear surrounding the annular hollow portion.

When the starter 10 starts the internal combustion engine, compression and expansion are repeated in the cylinder of the internal combustion engine. In the cylinder compression stage, since the pinion needs to overcome the compression reaction force and rotate the ring gear, a large load is generated between the pinion and the ring gear. Furthermore, during the cylinder expansion phase, the pinion is rotated by the ring gear, since the ring gear is accelerated by the expansion of the compressed gas in its rotational direction. In this case, a face of the tooth of the pinion, which is in contact with the ring gear and receives stress therefrom, alternates with another face of the tooth, and vibrations of sliding noise and collision noise caused by sliding and collision between the ring gear and the pinion, respectively, are transmitted from the above faces to the pinion and the ring gear. Since these vibrations are not damped, unpleasant noise is still present, so that the noise becomes larger or becomes echo.

In view of this, according to an aspect of the present invention, in the pinion gear having the structure as described above, transmission of vibration from the gear teeth to the drive shaft is suppressed or reduced by the annular hollow portion. In addition, the vibration transmitted to the annular hollow portion is absorbed by the vibration absorbing member stored in the hollow portion, and therefore, the vibration can be more effectively suppressed or reduced. Further, in the process of transmitting the vibration due to the contact from the ring gear toward the axis of the pinion, the vibration generated in the ring gear by contacting the pinion can be reduced satisfactorily. That is, the vibration of the ring gear can be reduced. That is, if the ring gear and the pinion gear are in contact with each other such that vibration is efficiently transmitted from the ring gear to the pinion gear, the crank-start noise generated on the pinion gear and the ring gear side can be effectively reduced. As a result, sliding noise, collision noise, rolling noise, and the like generated between the pinion gear and the ring gear can be attenuated and reduced. That is, if the ring gear and the pinion gear are in contact with each other to allow vibration to be efficiently transmitted from the ring gear to the pinion gear, the crank starting noise generated in the pinion gear and the ring gear can be effectively reduced.

Drawings

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

fig. 1 is a schematic diagram showing an exemplary configuration of a starter according to a first embodiment of the invention;

fig. 2 is a diagram showing a state of engagement of a pinion gear and a ring gear that mesh with each other according to the first embodiment of the invention;

fig. 3A and 3B are sectional views collectively showing one example of a pinion gear according to the first embodiment of the invention;

FIGS. 4A and 4B are cross-sectional views collectively illustrating another exemplary pinion gear according to a second embodiment of the present invention;

FIGS. 5A and 5B are cross-sectional views collectively illustrating yet another exemplary pinion gear according to a third embodiment of the present invention;

fig. 6A and 6B are sectional views collectively showing still another exemplary pinion gear according to a fourth embodiment of the invention;

FIGS. 7A and 7B are cross-sectional views collectively illustrating yet another exemplary pinion gear according to a fifth embodiment of the present invention;

fig. 8A and 8B are sectional views collectively showing still another exemplary pinion gear according to a sixth embodiment of the invention;

FIGS. 9A and 9B are cross-sectional views collectively showing yet another exemplary pinion gear according to a seventh embodiment of the present invention;

fig. 10A and 10B are sectional views collectively showing still another exemplary pinion gear according to an eighth embodiment of the invention;

fig. 11A and 11B are sectional views collectively showing still another exemplary pinion gear according to a ninth embodiment of the invention; and

fig. 12A and 12B are sectional views collectively showing a modification of the pinion gear.

Detailed Description

As discussed in international patent application No. 2010-136429(WO2010/136429a)), the teeth of the pinion are divided into pieces in the thickness direction of the pinion to suppress collision noise when the starter performs cranking. However, another noise is generated. The present invention has been made in view of the above problems, and an object thereof is to solve the problems.

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof, and to fig. 1 and the applicable drawings, a configuration in which a pinion gear is employed in a starter to start an engine is described according to a first embodiment of the present invention. As shown in fig. 1, a starter 10 is generally mounted on a vehicle to start an on-vehicle engine (i.e., an internal combustion engine). The starter 10 includes a DC (direct current) motor 11 and a magnetic switch 12 serving as a switch that is turned on to supply power to the DC motor 11. When power is supplied to the magnetic switch 12, an energization circuit extending from the battery to the DC motor 11 is closed, whereby power is supplied from the battery to the DC motor 11. Accordingly, a rotational force is generated and transmitted from the DC motor 11 to the drive shaft 13, thereby rotating the drive shaft 13.

Between the DC motor 11 and the drive shaft 13, a reduction device such as a planetary gear reducer (not shown) is provided to reduce the rotation speed and transmit the rotation of the DC motor 11 to the drive shaft 13. Specifically, a rotary shaft (not shown) of the DC motor 11 slowly drives the drive shaft 13 through a speed reducer. Further, one end of the drive shaft 13 facing the DC motor 11 (i.e., the right side in fig. 1) is supported by a reduction gear. The rotating shaft of the DC motor 11 may be used as the drive shaft 13 of the DC motor 11 instead of the reduction gear. Further, the other end of the drive shaft 13 opposite to the DC motor 11 is supported by a bearing 14.

The pinion carrier 15 is attached to the drive shaft 13 so as to be movable in the axial direction thereof. The pinion carrier 15 includes an overrunning clutch 16 (hereinafter simply referred to as clutch 16) connected to the outer periphery of the drive shaft 13 by helical spline coupling. The pinion carrier 15 also includes pinion gears 20 that can mesh with a ring gear 50 provided in the engine. The clutch 16 is constituted by a one-way clutch employing a known cam system. Specifically, the clutch 16 includes: attached to the outside of the drive shaft 13; an inner portion rotatably attached to the outer portion at the outer portion; and a clutch roller for transmitting or blocking a rotational torque between the outside and the inside. The clutch 16 thus transmits rotational torque in only a single direction.

The pinion gear 20 is movable integrally with the clutch 16 in the axial direction (i.e., the lateral direction in fig. 1) on the outer periphery of the drive shaft 13. The pinion 20 is attached to the unit at a position further from the motor 11 than the clutch 16. The pinion gear 20 is rotated by torque generated by the DC motor 11.

Thus, when the starter switch and the magnetic switch 12 are turned on, the shift lever 18 depresses the pinion carrier 15 away from the motor until the pinion 20 engages with the ring gear 50 of the engine. At the same time, the DC motor 11 rotates and performs cranking, thereby starting the engine. Conversely, when the starter switch is turned off, the DC motor 11 stops rotating, and the shift lever 18 biased by a return spring (not shown) depresses the pinion carrier 15 in the axial direction toward the DC motor 11 until the pinion 20 is disengaged from the ring gear 50.

Now, referring to fig. 2, the following describes the meshed state and a mechanism that applies force to each of the pinion gear 20 and the ring gear 50 when the pinion gear 20 rotates and drives the ring gear 50 in the meshed state. That is, fig. 2 is a sectional view showing the bearing 14 and the pinion 20 perpendicular to the drive shaft 13 shown in fig. 1.

Each of the pinion gear 20 and the ring gear 50 includes a spur gear, and meshes with each other with respective tooth surfaces in contact with each other. The pinion 20 has a relatively small diameter. The number of gear teeth 21 of the pinion gear 20 is from about eight to about fifteen. In contrast, the ring gear 50 has a relatively large diameter and is fixed to the flywheel of the engine. A given offset is provided between the gear teeth 21 of the pinion gear 20 and the gear teeth 51 of the ring gear 50 to facilitate engagement of the pinion gear 20 with the ring gear 50 when the pinion gear 20 moves in the axial direction. Each of the pinion gear 20 and the ring gear 50 may employ a helical gear instead of a spur gear.

When the pinion gear 20 is meshed with the ring gear 50 and the DC motor 11 of the starter 10 is driven to perform cranking, the rotation speed of the engine is pulsated. The above-described pulsation generates vibration and cranking noise in each of the pinion 20 and the ring gear 50. During cranking of the engine by the starter 10, compression and expansion are repeated in the cylinders of the engine. Therefore, during the compression phase of the cylinder, since the number of revolutions of cranking is reduced and a large load is generated between the pinion 20 and the ring gear 50 due to the compression reaction force, a large cranking noise occurs due to the sliding of these gears on each other and the rolling of these gears. In contrast, during the expansion phase of the cylinder, since the ring gear 50 is rotated at a high speed due to the expansion in the engine expansion phase, the pinion gear 20 may be rotated by the ring gear 50. That is, the tooth surface of the gear tooth 21 of the pinion 20 receiving the stress alternates with the adjacent tooth surface thereof. When the stress-receiving tooth surfaces alternate with each other, since any one of the ring gear 50 and the pinion gear 20 is temporarily separated from each other or the contact pressure generated therebetween is reduced, the vibration caused by the cranking remains in the ring gear 50 and cannot be attenuated. Therefore, a large crank starting noise is significantly generated by the collision, sliding, and rolling of the ring gear 50 and the pinion gear 20. Further, since the ring gear 50 is larger than the pinion gear 20, the vibration of the ring gear 50 generated by cranking is less likely to be attenuated, and thus noise is easily generated. However, by bringing the ring gear 50 into contact with the pinion 20, it is possible to effectively damp vibrations generated in such ring gear 50.

Specifically, when cylinder compression is performed, the pinion gear 20 is rotated by the rotational torque generated by the DC motor 11, and the ring gear 50 is rotated by the rotational torque generated by the pinion gear 20. In particular, the compression reaction force is maximized just before the stroke transition from the compression stroke to the expansion stroke. Therefore, in the compression stroke, the ring gear 50 is decelerated by the compression reaction force increased in this manner. At this time, since a large amount of current flows, the DC motor 11 generates a torque that is dominant over the compression reaction force. Therefore, since the torque generated by the DC motor 11 is maximized immediately before the end of the compression stroke, a large force acts on the pinion gear 20 and the ring gear 50, resulting in a large slip and rolling noise generated therebetween.

Further, when the stroke is changed from the compression stroke to the expansion stroke, since the expansion in the cylinder accelerates the rotation of the engine, the ring gear 50 starts to rotate at a higher speed and does not contact with the pinion 20 (i.e., is separated from the pinion 20). As a result, since the ring gear 50 and the pinion gear 20 are not in contact with (i.e., separated from) each other, the vibrations of the pinion gear 20 and the ring gear 50 generated in the compression stroke are radially propagated in the pinion gear 20 and the ring gear 50, respectively. Thus, the vibration is not damped or stopped. Therefore, the generated noise (i.e., crank start noise) causes an echo without reduction.

Further, during expansion in the cylinder, the ring gear 50 is rotated in the forward direction by expansion of the compressed gas therein. At this time, when the ring gear 50 rotates at a higher speed than the pinion gear 20, the pinion gear 20 is rotated by the ring gear 50. However, since the transmission of the rotation of the pinion gear 20 to the DC motor 11 is blocked by the clutch 16, the pinion gear 20 is easily driven by the ring gear 50. Further, when the pinion gear 20 is driven by the ring gear 50, the ring gear 50 and the pinion gear 20 collide with each other on respective tooth surfaces opposite to the driving tooth surfaces on which the ring gear 50 and the pinion gear 20 collide with each other in the compression stroke. Since the contact pressure between the ring gear 50 and the pinion gear 20 is relatively small, the vibration transmission from the ring gear 50 to the pinion gear 20 is relatively small. Therefore, when the pinion gear 20 is driven by the ring gear 50, vibrations caused by collision, sliding, and rolling are not attenuated in the pinion gear 20. Therefore, the vibrations of the pinion gear 20 and the ring gear 50 generated in the expansion stroke are propagated radially inside these gears 20 and 50, respectively, and remain unattenuated. Therefore, the noise generated by the vibration (i.e., the crank start noise) is increased without being reduced.

Therefore, in order to suppress the crank-start noise, it is necessary to suppress or reduce the propagation of undamped vibrations in the pinion gear 20 and the ring gear 50. In other words, the vibration needs to be damped quickly.

Therefore, in the first embodiment of the present invention, the annular hollow portion 22 is provided radially inside the pinion gear 20 (i.e., below the gear teeth 21), and the shock absorbing member 23 that absorbs the shock generated at the gear teeth 21 is housed. This can suppress vibration of the pinion 20 and the ring gear 50 caused by cranking in the pinion 20.

Fig. 3A and 3B are sectional views collectively showing the pinion gear 20. More specifically, fig. 3A is a lateral cross-sectional view showing the pinion gear 20 perpendicular to the axis of the pinion gear 20. Fig. 3B is a longitudinal sectional view showing the pinion 20 along the axis of the pinion 20. The pinion gear 20 includes a shaft hole 24 allowing the drive shaft 13 to be inserted. A hollow space surrounded and closely surrounded by the inner wall of the pinion gear 20 is provided in the pinion gear 20 as an annular hollow portion 22. The annular hollow portion 22 is a ring surrounding the shaft hole 24.

As shown in fig. 3A, the annular hollow portion 22 is disposed radially in the middle of the pinion 20 between the root circle and the circumference of the shaft hole 24. Furthermore, the wall surrounding (i.e., enclosing) the annular hollow 22 is relatively thin. Therefore, the pinion 20 can be elastically deformed with a small degree of bending, and vibration can be damped. In addition, since the pinion 20 has the side walls at both ends in the axial direction, the pinion 20 can be effectively thinned while ensuring necessary rigidity, thereby enabling the volume of the annular hollow portion 22 to be increased.

In addition, in the pinion gear 20, the shock absorbing member 23 has higher shock absorption than a surrounding portion surrounding the outer periphery of the annular hollow portion 22. Vibration absorption is expressed as a degree of vibration suppression capability such that the higher the vibration absorption, the greater the vibration attenuation capability. The shock absorbing member 23 has a characteristic capable of absorbing vibration generated at a given frequency by converting the vibration into thermal energy. The shock absorbing member 23 is a mixture powder prepared by mixing two or more kinds of powders respectively having different particle sizes. Further, in the vicinity of the wall surrounding the annular hollow portion 22, the particle size of the powder stored as the shock absorbing member 23 in the annular hollow portion 22 and the particle size of the powder at the core portion of the annular hollow portion 22 are different from each other. That is, the particle size of the powder gradually becomes larger as it is stored in the annular hollow portion 22 in the vicinity of the wall surrounding the annular hollow portion 22 (i.e., in the vicinity of the interface between the annular hollow portion 22 and the pinion gear 20). In contrast, the particle size of the powder stored in the core portion of the annular hollow portion 22 is small.

An exemplary method of manufacturing the pinion gear 20 will now be described. The pinion 20 is made by melting powder with a laser beam in a 3D (three-dimensional) printer formed into a given shape.

Specifically, in 3D printers, powder is initially accumulated on a liftable platform to have a default thickness. Then, the laser beam is irradiated in a sectional shape determined based on the blueprint. Thus, the powder is melted and solidified, thereby forming a thin layer in a sectional shape. The platform is then lowered by a height equal to the thickness of the monolayer formed in this manner. The powder is re-accumulated and spread over the entire platform to have a height equal to a monolayer thickness. Further, the laser beam is irradiated in a sectional shape so that the powder is melted and bonded to the previously formed layer. By repeating such a process, the 3D printer manufactures the pinion 20 having a given shape.

Further, with such a 3D printer, the pinion 20 is manufactured without radiating a laser beam to the powder corresponding to the annular hollow portion 22. As a result, when the pinion gear 20 is completely manufactured, the powder is stored in the annular hollow portion 22 of the pinion gear 20. However, the powder serves as the shock-absorbing member 23 stored in the annular hollow portion 22.

Then, the pinion 20 manufactured by the 3D printer is heat-treated. That is, the pinion 20 manufactured only by the 3D printer may lack the required strength. Therefore, by applying the heat treatment to the pinion gear 20, the pinion gear 20 is strengthened. At this time, the particle size of the powder stored in the annular hollow portion 22 can be effectively increased by adjusting the heating temperature or the distribution of the powder. That is, the heat used in the heat treatment is transferred to the powder, and the powder is melted and solidified. As a result, the particle size of the powder located near the wall surrounding the annular hollow portion 22 increases. On the contrary, since it does not melt, the particle size of the powder stored in the vicinity of the core portion of the annular hollow portion 22 is kept small.

In this way, the particle size of the powder (shock absorbing member 23) stored in the annular hollow portion 22 near the wall is larger than the particle size of the powder stored in the vicinity of the core portion of the annular hollow portion 22. When the particle size of the powder stored in the annular hollow portion 22 changes, the frequency of absorption by the powder also changes. Therefore, by changing the particle size of the powder stored as the shock absorbing member 23, the frequency at which the shock can be absorbed can be increased. In addition, since powders of different particle sizes are mixed, small-sized particles enter gaps between large-sized particles, thereby enabling more efficient filling. Further, since the powder particles stored in the vicinity of the surface of the annular hollow portion 22 can be increased in size, the powder can be locally strengthened, whereby the vibration absorption rate can be improved, so that the generation of noise can be reduced while the strength of the pinion gear 20 is improved. As described above, according to the present embodiment, the advantages described below can be obtained.

As described above, when the ring gear 50 is driven by the pinion gear 20, crank-start noise is generated. That is, the ring gear 50 is affected by a change in engine load caused by the compression stroke and the expansion stroke in the engine. Therefore, when the engine load changes, the contact pressure generated between the pinion gear 20 and the ring gear 50 changes accordingly. In this case, since the DC motor 11 of the starter 10 is rotated by the driving force that is dominant in the variation of the contact pressure, the contact surface generates the crank start noise. The vibrations of the ring gear 50 and the pinion 20 generated by the crank activation are mutually transmitted to each other through the respective contact surfaces therebetween. Since the vibration of the pinion gear 20 and the ring gear 50 can be suppressed, the rapid attenuation of the vibration of the pinion gear 20 is a decisive factor in reducing the cranking noise. In view of this, according to the present embodiment, the vibrations generated in the gear teeth 21 are suppressed from traveling in the pinion 20 by the annular hollow portion 22, thereby suppressing the occurrence of crank-start noise.

In view of this, the annular hollow portion 22 is provided in the pinion gear 20, so that it is possible to effectively suppress or reduce the vibration generated in the gear teeth 21 of the pinion gear 20 from traveling radially inward to the drive shaft 13 of the pinion gear 20.

In addition, the annular hollow portion 22 accommodates powders such as metal powder, resin powder, and the like serving as the vibration absorbing member 23, so that the vibration energy is more effectively absorbed.

Further, as the particle size of the powder changes, the frequency of the vibrational waves absorbed by the powder (i.e., the particles) typically changes. In view of this, powders having various particle sizes are used as the shock absorbing member 23, so that the frequency band of the shock wave absorbed by the powder can be expanded.

Further, the closer to the wall surrounding the annular hollow portion 22 (or the outer circumferential surface of the annular hollow portion 22), the larger the particle size of the powder. In addition, the particle size of the powder is smaller as it is closer to the core of the annular hollow portion 22. Therefore, the particle size of the powder located near the core is different from the particle size of the powder near the wall surrounding the annular hollow portion 22, so that the frequency band in which the vibration wave can be absorbed can be expanded.

Now, a second embodiment of the present invention is described below with reference to fig. 4A and 4B. Fig. 4A and 4B are sectional views collectively showing the pinion gear 20 of the second embodiment. More specifically, fig. 4A is a cross-sectional view showing the pinion gear 20 perpendicular to the axis of the pinion gear 20. Fig. 4B is a longitudinal sectional view showing the pinion 20 along the axis of the pinion 20.

As shown, according to the second embodiment, a plurality of connecting portions 25 are provided in the annular hollow portion 222 to connect the radially outer wall 22A of the annular hollow portion 22 with the radially inner wall 22B thereof, as described in more detail below.

Specifically, as shown in fig. 4A, the annular hollow portion 222 is radially arranged between the root circle of the pinion gear 20 and the circumference of the shaft hole 24. The vibration absorbing material 23 made of powder is housed in the annular hollow portion 222. The powder desirably includes two or more different particle sizes.

In the annular hollow portion 222, a plurality of beam-like connecting portions 25 are provided to connect a radially outer wall 22A formed radially outside the annular hollow portion 222 with a radially inner wall 22B formed radially inside the annular hollow portion 222. The connecting portion 25 is a linear rod-shaped member made of substantially the same material as the pinion gear 20, and is formed integrally with the pinion gear 20. These plurality of connecting portions 25 radially extend at intervals of substantially the same angle as the axis of the pinion gear 20 while intersecting each other, as viewed in a direction orthogonal to the axial direction thereof. Thus, since the connecting portion 25 is opposed to the radially outer wall 22A and the inner wall 22B of the annular hollow portion 222, the connecting portion 25 can reinforce the inner space of the annular hollow portion 222. As a result, the annular hollow portion 222 can be enlarged to allow a larger amount of the shock-absorbing member 23 to be filled therein. Such a pinion 20 is manufactured by using a 3D printer so that the connection portion 25 can be freely positioned in the annular hollow portion 222.

Further, since the connecting portion 25 extends radially, the connecting portion 25 functions as a passage for vibration generated by the gear teeth 21. That is, the vibration generated by the gear teeth 21 may be transmitted to one end of the connecting portion 25, and further transmitted to the opposite end (i.e., the radially inner wall 22B) via the connecting portion 25 in the annular hollow portion 222. However, since the connecting portion 25 is surrounded by the shock absorbing member 23 in the annular hollow portion 222, the shock is absorbed by the shock absorbing member 23. That is, since each of the plurality of connecting portions 25 provided in the annular hollow portion 222 of the pinion gear 20 is in contact with the shock absorber 23, the interface of the shock absorber 23 and the pinion gear 20 in contact with each other is enlarged, and the shock can be absorbed and damped more effectively.

Now, a third embodiment of the present invention is described below with reference to fig. 5A and 5B. That is, fig. 5A and 5B are sectional views collectively showing the pinion gear 20 of the third embodiment. More specifically, fig. 5A is a cross-sectional view showing the pinion 20 perpendicular to the axis of the pinion 20. Fig. 5B is a longitudinal sectional view showing the pinion gear 20 along the axis of the pinion gear 20. According to the third embodiment, the hollow portion 322 includes a plurality of hollow portions 322C separately formed below the gear teeth 21 aligned in the circumferential direction of the pinion gear 20, respectively, as described in detail below.

That is, a cylindrical hollow portion 322C is formed near the base of each gear tooth 21 aligned in the circumferential direction. More specifically, the center of each cylindrical hollow portion 322C is located on a line extending through the axis of the pinion gear 20 and the center between the opposite tooth faces of the same gear tooth 21 corresponding to the cylindrical hollow portion 322C. In addition, each cylindrical hollow portion 322C includes a recess having a circular cross section, which extends in the axial direction from one side of the pinion 20. Since one end of each cylindrical hollow portion 322C is open, a cover 26 is provided to cover the opening of the cylindrical hollow portion 322C.

Further, each cylindrical hollow portion 322C accommodates a shock absorbing member 23 composed of powder. The powder desirably includes two or more different particle sizes. Further, since there is one for each gear tooth 21, the space of each cylindrical hollow portion 322C is relatively narrow. Thereby, uneven distribution of the shock absorbing member 23 in each cylindrical hollow portion 322C can be suppressed or reduced. Further, since each gear tooth 21 is provided with the cylindrical hollow portion 322C, it is possible to effectively suppress or reduce the vibration generated by the corresponding gear tooth 21 from traveling radially to the drive shaft 13 via the inside of the pinion gear 20.

Further, in the present embodiment, the pinion 20 is prepared by one of pressing, casting, cutting, and the like. That is, the depressed hollow portion 322C having an opening at one end may be manufactured by using such a conventional method instead of the 3D printer. Therefore, after the cylindrical hollow portion 322C is filled with the damper 23, the cap 26 is fixed to the opening by welding. As described above, the cap 26 may be prepared for each hollow portion 322C. Conversely, another annular cover 26 capable of covering all the openings may be prepared and fixed thereto. By such a manufacturing method, the shock absorbing member 23 can be arbitrarily stored in the cylindrical hollow portion 322C.

Now, a fourth embodiment of the present invention is described below with reference to fig. 6A and 6B. Fig. 6A and 6B are sectional views showing a pinion 20 of the fourth embodiment. More specifically, fig. 6A is a cross-sectional view showing the pinion 20 perpendicular to the axis of the pinion 20. Fig. 6B is a longitudinal sectional view showing the pinion 20 along the axis of the pinion 20.

As shown in the drawing, according to the fourth embodiment, the hollow portion 422 includes a plurality of cylindrical hollow portions 422C. Each cylindrical hollow 422C has an elliptical cross-section with a major axis in the circumferential direction of the pinion gear 20 and a minor axis in the radial direction thereof, as described in more detail below.

Specifically, in the vicinity of the bases of the gear teeth 21 aligned in the circumferential direction, separate plural hollow portions 422C are respectively formed below the gear teeth 21. The center of each cylindrical hollow portion 422C is located on a line extending through the axis of the pinion gear 20 and the center between the opposite surfaces of the same gear tooth 21 corresponding to the cylindrical hollow portion 422C. Since each cylindrical hollow portion 422C has an elliptical cross section and is thus longer in the circumferential direction than in the radial direction of the pinion gear 20, the circumferential dimension of each cylindrical hollow portion 422C can be lengthened while maintaining the dimension in the radial direction. Thereby, the vibration transmitted radially inward from the tooth surface can be effectively suppressed or reduced.

Further, each cylindrical hollow portion 422C accommodates a shock absorbing member 23 composed of powder. The powder desirably includes two or more different particle sizes. Since there is one for each gear tooth 21, the space of each cylindrical hollow portion 422C is relatively narrow. This can suppress or reduce uneven distribution of the damper 23 in the cylindrical hollow portion 422C. Further, since each gear tooth 21 is provided with the cylindrical hollow portion 422C, it is possible to effectively suppress or reduce the vibration generated by the corresponding gear tooth 21 from traveling radially to the drive shaft 13 via the inside of the pinion gear 20.

Now, a fifth embodiment of the present invention is described below with reference to fig. 7A and 7B. Fig. 7A and 7B are sectional views showing a pinion 20 of a fifth embodiment. More specifically, fig. 7A is a cross-sectional view showing the pinion 20 perpendicular to the axis of the pinion 20. Fig. 7B is a longitudinal sectional view showing the pinion 20 along the axis of the pinion 20.

As shown, according to the fifth embodiment, the columnar projections 27 stand from the bottom of each cylindrical hollow portion 522C toward the inside of the cylindrical hollow portion 522C, as described in more detail below.

Specifically, the hollow portion 522 includes a cylindrical hollow portion 522C formed near the base of each gear tooth 21 aligned in the circumferential direction of the pinion gear 20. As shown in fig. 7 (a), each cylindrical hollow portion 522C is disposed radially in the middle of the pinion 20 between the root circle and the circumference of the shaft hole 24. Further, each cylindrical hollow portion 522C accommodates the shock absorbing member 23 composed of powder. The powder desirably includes two or more different particle sizes.

As described above, the columnar projection 27 projects from the bottom of the cylindrical hollow portion 522C. The projection 27 comprises a rod-like linear member and functions as a cantilever. The projection 27 is made of substantially the same material as the pinion 20 and is integral with the pinion 20. Each cylindrical hollow 522C has a hollow cylindrical shape and is surrounded by a circular inner wall. The projection 27 extends axially from the center of the circular bottom of the cylindrical hollow portion 522C to the opposite side thereof. Therefore, for each gear tooth 21, the vibration generated in the gear tooth 21 is also transmitted to the protrusion 27 arranged in the cylindrical hollow portion 522C. Since the protrusion 27 is surrounded by the shock-absorbing member 23, the shock transmitted to the protrusion 27 can be effectively absorbed by the shock-absorbing member 23. Further, since the projection 27, which functions as a part of the pinion gear 20, contacts the shock absorbing member 23, the area of the shock absorbing member 23 in contact with the pinion gear 20 can be increased, so that the shock can be absorbed and/or damped more effectively.

Now, a sixth embodiment of the present invention is described below with reference to fig. 8A and 8B. Fig. 8A and 8B are sectional views showing a pinion 20 of a sixth embodiment. More specifically, fig. 8A is a cross-sectional view showing the pinion 20 perpendicular to the axis of the pinion 20. Fig. 8B is a longitudinal sectional view showing the pinion 20 along the axis of the pinion 20.

As shown, according to the sixth embodiment, the hollow portion 622 includes: an annular portion located radially inward of gear teeth 21; and a plurality of lobes that each project from the ring portion into the gear teeth 21, as opposed to the top land (top land) and tooth surface of the gear teeth 21, as described in more detail below.

Specifically, the hollow portion 622 has an annular first hollow portion 622D that surrounds the shaft hole 24 and is located radially inward of the gear teeth 21. The hollow 622 also includes a plurality of second protruding hollows 622E that protrude radially outward from the outer periphery of the cylindrical first hollow 622D through the tooth bottom circle, opposite the respective rear sides of the top land and the tooth face of the gear teeth 21. The annular first hollow portion 622D communicates with (i.e., is integral with) the second protruding hollow portion 622E. As shown in fig. 8A and 8B, the hollow portion 622 is disposed radially in the middle of the pinion 20 between the tooth tip circle and the circumference of the shaft hole 24. The annular hollow portion 622 accommodates a shock absorbing member 23 made of powder. The powder desirably includes two or more different particle sizes.

Therefore, since the hollow 622 receives the shock-absorbing member 23 and extends along the rear side of the top land and the tooth surface where the vibration is generated, and extends to the radially inner side of the gear teeth 21 for preventing the vibration from spreading to the entire pinion gear 20, the vibration can be absorbed and/or damped more effectively.

Now, a seventh embodiment of the present invention is described below with reference to fig. 9A and 9B. Fig. 9A and 9B are sectional views showing a pinion 20 of a seventh embodiment. More specifically, fig. 9A is a cross-sectional view showing the pinion 20 perpendicular to the axis of the pinion 20. Fig. 9B is a longitudinal sectional view showing the pinion 20 along the axis of the pinion 20. As shown in the drawings, according to the seventh embodiment, the hollow portion 722 includes an annular first hollow portion 722D and a plurality of second hollow portions 722E that are respectively disposed inside the gear teeth between the gear teeth and the annular first hollow portion 722D. The annular first hollow portion 722D and each second hollow portion 722E are separated by an annular spacer 28 extending in the circumferential direction of the pinion gear 20.

Specifically, the annular first hollow portion 722D is located radially inward of the gear teeth 21 to surround the shaft hole 24. Each second hollow portion 722E has a rectangular cross section, and extends in the width direction of the gear teeth. Each second hollow portion 722E extends radially on the root circle to face the rear side of the corresponding gear tooth 21. Also, between the annular first hollow portion 722D and each second hollow portion 722E, the separator 28 extends in the circumferential direction. Thus, the pinion gear 20 includes annular first and second hollow portions 722D and 722E facing the rear side of the face of the corresponding one of the gear teeth 21. As shown in fig. 9A and 9B, the hollow portion 722 is disposed radially in the middle of the pinion 20 between the tooth tip circle and the circumference of the shaft hole 24. The annular hollow portion 722 accommodates a vibration absorbing material 23 made of powder. The powder desirably includes two or more different particle sizes. Further, one of the type, grain size and material of the shock-absorbing member 23 stored in the annular first hollow portion 722D may be different from that in the second hollow portion 722E. Further, these shock absorbing members 23 may be powder and liquid, respectively. By using different types of the vibration absorbing members 23, vibrations of various frequencies can be attenuated.

As described above, since the annular hollow portion 722 that houses the shock absorbing member 23 is provided at each position facing the rear side of the face of the gear tooth that generates vibration and located radially inward of the gear tooth 21 that diffuses vibration, vibration can be absorbed and/or damped more effectively. In addition, since the annular first hollow portion 722D and the second hollow portion 722E are partitioned, and the second hollow portion 722E is disposed on each gear tooth 21, uneven distribution of the shock-absorbing member 23 therein can be suppressed or reduced.

Now, an eighth embodiment of the present invention is described below with reference to fig. 10A and 10B. Fig. 10A and 10B are sectional views showing a pinion 20 of a seventh embodiment. More specifically, fig. 10A is a cross-sectional view showing the pinion 20 perpendicular to the axial direction of the pinion 20. Fig. 10B is a longitudinal sectional view showing the pinion 20 along the axis of the pinion 20.

As shown in the drawings, according to the eighth embodiment, a plurality of connecting portions 25 are provided in an annular first hollow portion 822D having the same configuration as the annular first hollow portion 722D of the seventh embodiment, so as to connect a radially outer wall 822A of the annular first hollow portion and a radially inner wall 822B thereof to each other, as described in more detail below.

Specifically, the hollow portion 822 includes an annular first hollow portion 822D located radially inward of the gear teeth 21 to surround the shaft hole 24. Each second hollow portion 822E has a rectangular side cross section, and extends in the width direction of the gear teeth. Each second hollow portion 822E extends radially on the root circle to face the rear side of the corresponding gear tooth 21. That is, between the annular first hollow portion 822D and each second hollow portion 822E, the annular spacer 28 extends in the circumferential direction of the pinion gear 20. As shown in fig. 10A and 10B, the hollow portion 822 is disposed radially in the middle of the pinion 20 between the tooth tip circle and the circumference of the shaft hole 24.

In addition, a plurality of connecting portions 25 are provided in the annular first hollow portion 822D to connect a radially outer wall 22A located radially outside the annular first hollow portion 822D and a radially inner wall 22B located radially inside thereof. Each of the connecting portions 25 is a rod-shaped linear member composed of substantially the same material as the pinion gear 20, and is manufactured integrally with the pinion gear 20. One coupling portion 25 is provided on each gear tooth 21. Therefore, since the connecting portion 25 arranged in this way supports the radially outer wall 22A and the radially inner wall 22B of the annular first hollow portion 822D, the space of the annular first hollow portion 822D can be reinforced.

The annular hollow portion 822 accommodates a shock absorbing member 23 made of powder. The powder desirably includes two or more different particle sizes. Further, it is preferable that the type of the shock absorber 23 stored in the annular first hollow portion 822D is different from that stored in the second hollow portion 822E. That is, by using the different types of vibration absorbing members 23, vibrations of various frequencies can be attenuated.

Now, a ninth embodiment of the present invention is described below with reference to fig. 11A and 11B. That is, fig. 11A and 11B are sectional views collectively showing the pinion 20 of the ninth embodiment. More specifically, fig. 11A is a cross-sectional view showing the pinion 20 perpendicular to the axis of the pinion 20. Fig. 11B is a longitudinal sectional view showing the pinion 20 along the axis of the pinion 20.

According to the ninth embodiment, a plurality of blocking members 29 are provided in the hollow portion 922 to suppress the shock absorber 23 from moving in the circumferential direction of the pinion gear 20 in the hollow portion 22, as described in more detail below.

That is, the hollow portion 922 includes an annular first hollow portion 922D located radially inward of the gear teeth 21 to surround the shaft hole 24. The hollows 922 also include a plurality of second hollows 922E facing the top land and the rear side of the tooth face of the gear teeth 21. The annular first hollow portion 922D and the second hollow portion 922E communicate with each other (i.e., are integral). As shown in fig. 11A and 11B, the annular hollow portion 922 is disposed radially in the middle of the pinion 20 between the tooth tip circle and the circumference of the shaft hole 24. The annular hollow portion 922 accommodates a shock absorbing member 23 made of powder. The shock absorbing member 23 is desirably composed of powders having two or more different particle sizes.

As shown, in the hollow portion 922, a plurality of blocking members 29 connect the radially outer wall 22A of the second hollow portion 922E with the radially inner wall 22B of the annular first hollow portion 922D. Each blocking member 29 comprises a wall-like member of the same material as the pinion 20 having a curved cross-section. The blocking members 29 are arranged one by one at equal intervals in the circumferential direction for each gear tooth 21. Therefore, since the wall-like blocking member 29 is provided on each gear tooth 21, the movement and the corresponding uneven distribution of the shock-absorbing member 23 can be suppressed or reduced. In this regard, each blocking member 29 is desirably porous (i.e., grid-like) by having a plurality of pores. That is, the vibration generated in the gear teeth 21 is also transmitted to the blocking member 29 inside the hollow portion 922. However, since a plurality of holes are formed in the blocking member 29 and the shock-absorbing member 23 is allowed to pass therethrough, the shock can be absorbed and/or damped more effectively.

Now, various modifications of the embodiment described above are described below with reference to fig. 12A and 12B. That is, the present invention is not limited to the embodiments described above, and can be implemented by modifying them as follows. For example, the following different exemplary variations may be applied to each of the above-described embodiments individually or in any combination.

First, although manufactured by a 3D printer in the first, second, and fourth to eighth embodiments described above, the pinion 20 may be manufactured by casting, cutting, pressing, or the like.

Further, although the shock absorber 23 is composed of the same powder in a molten or non-molten state as that used in the 3D printers of the above-described first, second, and fourth to eighth embodiments, the shock absorber 23 may be composed of different various powders. In this case, when the pinion 20 is produced by the 3D printer, after the powder is ejected through the hole, different powder may be stored in the annular hollow portion 22 of the pinion 20 through the newly employed communication hole.

As shown in fig. 12, instead of the powder, a predetermined liquid may be used as the vibration absorbing material and stored in the annular hollow portion 22. For example, a single-component liquid such as water, alcohol, oil, refrigerant, or the like may be used, or a mixed liquid may be used. In this case, the annular hollow 22 may be completely or partially filled with liquid. Further, in this case, the pressure of the annular hollow portion 22 may be controlled so that the liquid performs the state transition due to heat generated in the annular hollow portion 22 when the pinion gear 20 is driven.

Further, the rate of vibration traveling through the liquid is less than the rate of vibration traveling through the solid. In view of this, by adjusting the kind or combination of the liquids stored in the annular hollow portion 22, it is possible to damp or suppress vibration at the interface of the liquids having different physical properties or the like. In addition, by partially transmitting and attenuating the vibration to the liquid in the annular hollow portion 22, the energy of the vibration wave emitted to the outside as noise can be minimized, and the noise can be reduced. In addition, when a part of the annular hollow portion 22 is filled with liquid, since an interface with gas appears, vibration can be absorbed or damped. However, in this case, the shock-absorbing members may be unevenly distributed. In this case, however, the pinion 20 may abruptly stop rotating due to such uneven distribution.

As described above, according to one embodiment of the present invention, a novel pinion gear 20 is provided that is fixed to the drive shaft 13 of a starter 10 for starting an internal combustion engine. The pinion gear rotates by meshing with a ring gear 50 provided in the internal combustion engine. The pinion gear 20 includes gear teeth 21 arranged on an outer circumferential surface thereof, an annular hollow 22 located inside the gear teeth, and a shock absorbing member 23 stored in the annular hollow. The shock-absorbing member absorbs vibration at the core of the annular hollow portion more than at the outer edge thereof.

When the starter 10 starts the internal combustion engine, compression and expansion are repeated in the cylinder of the internal combustion engine. In the cylinder compression stage, since the pinion needs to overcome the compression reaction force and rotate the ring gear, a large load is generated between the pinion and the ring gear. Furthermore, during the cylinder expansion phase, the pinion is rotated by the ring gear, since the ring gear is accelerated by the expansion of the compressed gas in its direction of rotation. In this case, the face of the tooth of the pinion, which is in contact with the ring gear and receives stress therefrom, alternates with the other face of the tooth, and vibrations of sliding noise and collision noise, which are respectively caused by sliding and collision of the ring gear and the pinion between them, are transmitted from the face to the pinion and the ring gear. Since these vibrations are not damped, unpleasant noise is still present, making the noise even larger or echoing.

In view of this, according to an aspect of the present invention, in the pinion gear having the structure as described above, transmission of vibration from the gear teeth to the drive shaft is suppressed or reduced by the annular hollow portion. In addition, the vibration transmitted to the annular hollow portion is absorbed by the vibration absorbing member stored in the hollow portion, and therefore, the vibration can be more effectively suppressed or reduced. Further, in the process of transmitting the vibration due to the contact from the ring gear toward the axis of the pinion, the vibration generated in the ring gear by contacting the pinion can be reduced satisfactorily. That is, the vibration of the ring gear can be reduced. That is, if the ring gear and the pinion gear are in contact with each other such that vibration is efficiently transmitted from the ring gear to the pinion gear, the crank-start noise generated on the pinion gear and the ring gear side can be effectively reduced. As a result, the sliding noise, the collision noise, the rolling noise, and the like generated between the pinion gear and the ring gear can be suppressed and reduced. That is, if the ring gear and the pinion gear are in contact with each other such that vibration is efficiently transmitted from the ring gear to the pinion gear, the crank-start noise generated on the pinion gear and the ring gear side can be effectively reduced.

In another embodiment of the invention, a shaft hole 24 is provided to allow insertion of the drive shaft, and an annular hollow surrounds the shaft hole. Thus, by providing the ring-shaped hollow portion in the pinion gear, it is possible to favorably suppress or reduce transmission of vibration generated by each tooth of the pinion gear to the inside in the radial direction of the drive shaft. In yet another embodiment of the present invention, a connecting portion 25 is provided to connect the radially outer wall 22A of the annular hollow portion and the radially inner wall 22B of the annular hollow portion to each other. The radially outer wall serves as a radially outer portion of the hollow portion, and the radially inner wall serves as a radially inner portion of the hollow portion. Thus, the space of the annular hollow portion can be reinforced by providing the connecting portion in the annular hollow portion. In addition, the vibration generated in the gear teeth is transmitted to the connecting portion of the annular hollow portion. However, in this case, since the connection portion is surrounded by the shock absorbing member, the shock transmitted to the connection portion is easily absorbed by the shock absorbing member. Therefore, the vibration can be absorbed and damped more effectively.

In still another embodiment of the present invention, at least one blocking member 29 is disposed within the annular hollow portion to inhibit the shock absorber from moving in the circumferential direction of the pinion gear in the annular hollow portion. Therefore, by preventing the shock absorbing member from moving in the circumferential direction, uneven distribution in the shock absorbing member can be suppressed or reduced. Further, the vibration generated in the gear teeth is also transmitted to the blocking member in the annular hollow portion. However, since the blocking member is surrounded by the shock absorber, the shock transmitted to the blocking member can be easily absorbed by the shock absorber. Therefore, the vibration can be absorbed and damped more effectively.

In yet another embodiment of the present invention, the annular hollow portion includes at least two cylindrical hollow portions 322C arranged in the circumferential direction of the pinion gear for each tooth. Therefore, by providing at least two cylindrical hollow portions in each tooth, it is possible to satisfactorily suppress or reduce the vibration generated in the tooth and transmitted from the pinion gear radially inward to the drive shaft. Further, by providing at least two cylindrical hollow portions in each tooth, uneven distribution of the shock-absorbing members in the annular hollow portion can be suppressed or reduced.

In still another embodiment of the present invention, each of the at least two cylindrical hollow portions has a flat sectional shape that is longer in a circumferential direction of the pinion and shorter in a radial direction of the pinion. Thereby, since each of the at least two cylindrical hollow portions is longer in the circumferential direction than in the radial direction, it is possible to increase the circumferential dimension while maintaining the radial dimension of each of the at least two cylindrical hollow portions. This can further effectively suppress the transmission of vibration to the drive shaft via the pinion gear.

In a further embodiment of the present invention, the annular hollow portion comprises: an annular internal hollow portion located radially inward of the gear teeth of the pinion gear; and at least two rear side hollows at respective positions facing a rear side of the tooth surface of the gear tooth. That is, hollow portions are provided respectively on the radially inner sides of the gear teeth surrounding the shaft to prevent vibration from spreading to the entire pinion gear and portions facing the rear sides of the respective tooth surfaces where vibration occurs. Therefore, by filling the hollow portion with the shock absorbing member, the shock can be absorbed and damped more effectively.

In a further embodiment of the present invention, the annular hollow portion comprises: a first hollow portion 722D located radially inward of the gear teeth of the pinion gear and surrounding the shaft hole; at least two second hollows 722E, said at least two second hollows 722E being located at respective positions at the rear side of the face facing the gear teeth; and a partition 28, the partition 28 extending in a circumferential direction to separate the first hollow portion and the at least two second hollow portions from each other. That is, the hollow portion is provided at a portion facing the rear side of the tooth surface where the vibration occurs and at a portion radially inside the gear teeth to prevent it from spreading to the entire pinion gear. Therefore, since the shock-absorbing member is stored in the hollow portion, the shock can be absorbed and damped more effectively. Further, since the first hollow portion and the second hollow portion are separated from each other and each gear tooth is provided with the second hollow portion, it is possible to effectively suppress uneven distribution of the shock-absorbing members.

In yet another embodiment of the invention, the shock absorber includes a powder. Therefore, by filling the hollow portion with powder such as metal powder, resin powder, or the like as a vibration absorbing member, vibration can be effectively absorbed.

In another embodiment of the invention, the powder is a mixture of two or more different particle sizes. That is, the width of the frequency range in which vibration can be damped varies depending on the particle size of the powder. In view of this, powders of two or more particle sizes are used as the vibration absorbing member to increase the frequency of absorbing the vibration waves. That is, by using powders having two or more particle sizes, vibration can be absorbed more effectively.

In still another embodiment of the present invention, the particle size of the powder stored as the shock absorber in the vicinity of the wall surrounding the annular hollow portion is different from the particle size of the powder stored in the core of the annular hollow portion. The core portion corresponds to the vicinity of the center of the cross section of the annular hollow portion. Further, the particle size of the powder stored near the wall is larger than the particle size of the powder stored in the core of the hollow portion.

The closer to the wall surrounding the annular hollow portion 22 (i.e., the outer circumferential surface of the annular hollow portion 22), the larger the particle size of the powder. Therefore, since the particle size of the powder located near the core of the annular hollow portion 22 is different from the particle size of the powder near the wall surrounding the annular hollow portion 22, the frequency band in which the vibration wave can be absorbed can be expanded.

In yet another embodiment of the invention, the shock absorber includes a liquid. That is, the rate at which the vibrations travel through the liquid is less than the rate at which the vibrations travel through the solid. In view of this, by adjusting the kind or combination of the liquids stored in the annular hollow portion, it is possible to damp or suppress vibration at the interface of the liquids having different physical properties or the like. Further, since it easily changes its own pressure distribution, for example, by changing the density in response to a vibration wave, the liquid can easily absorb the vibration. Further, since it easily changes its own pressure distribution, for example, by changing the density in response to a vibration wave, the liquid can easily absorb the vibration. In view of this, by partially transmitting the vibration to the liquid stored in the annular hollow portion to attenuate it, the energy of the vibration wave emitted to the outside as noise can be minimized, and the noise can be reduced.