JP2016211728A - Internal gear and speed reducer having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of an internal gear for a speed reducer and concurrently minimize increase of cost and weight of the internal gear.SOLUTION: An internal gear 52 comprises: a ring-shaped gear part 52a having a tooth surface 521; and a body part 52b including a shaft support part 523 for supporting an output shaft 5a of a speed reducer and an outer periphery part 522 for holding an outer periphery of the gear part 52a. The gear part 52a is formed by a sintered metal and the body part 52b is injection molded by using a resin with the gear part 52a used as an insert component.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal gear and a speed reducer having the internal gear.

A starter used for starting an automobile engine inputs an output of a motor to an overrunning clutch (hereinafter simply referred to as a clutch) via a reduction gear, and a pinion gear attached to an output shaft of the clutch by switching an electromagnetic switch. A configuration is adopted in which the pinion gear is engaged and disengaged with respect to the ring gear on the engine side by reciprocating in the axial direction.

As a reduction gear used for a starter, a planetary gear mechanism having a sun gear driven by a motor, a ring gear fixed to a stationary side, and a planetary gear that meshes with both the sun gear and the ring gear to rotate and revolve may be used. Many. As the ring gear, an internal gear (internal gear) having a tooth surface on the inner periphery is usually used. As an internal gear of a starter planetary gear mechanism, for example, a resin internal gear described in Japanese Patent Application Laid-Open No. 2007-77810 (Patent Document 1) is known. As shown in FIG. 6, the resin internal gear 100 is fixed to the inner peripheral surface of the center case 101.

The output shaft 104 of the speed reducer 103 needs to be rotatably supported at its shaft end with respect to a stationary member (for example, the center case 101). Thus, in order to rotatably support the output shaft 104 of the speed reducer 103, in the starter of Patent Document 1, the inner diameter end of the center case 101 holding the internal gear 100 is extended in the axial direction to form a shaft support portion 105. The output shaft 104 of the speed reducer 103 is rotatably supported by a slide bearing 106 press-fitted and fixed to the inner periphery of the shaft support portion 105.

JP 2007-77810 A

  In recent automobiles, there is an increasing number of examples equipped with an idling stop mechanism that detects when a vehicle is temporarily stopped, automatically stops the engine, and drives the starter to restart the engine when the vehicle restarts. . In a vehicle equipped with an idling stop mechanism, the engine is frequently stopped and restarted. Therefore, each gear of the reduction gear incorporated in the starter is 10 times or more compared to a gear for a vehicle not equipped with the mechanism. A durable life is required.

However, since the fatigue resistance of resin parts is generally inferior to that of metal parts, if the entire internal gear 100 is formed of resin as in Patent Document 1, the durability of the internal gear is lowered. Therefore, when this internal gear 100 is used for a starter for a vehicle equipped with an idling stop mechanism, there is a possibility that the durability life required for the reduction gear cannot be satisfied. On the other hand, the internal gear 100 is larger than the other gears (sun gear or planetary gear) of the speed reducer 103. Therefore, if the entire gear is made of metal, the weight increases remarkably, and there is a demand for weight reduction of automobile parts. The result will be contrary. In addition, when the shaft support portion 105 that supports the output shaft 104 of the reduction gear is made of metal, the weight of the entire starter is increased.

Therefore, an object of the present invention is to increase the durability of the internal gear for a speed reducer while minimizing cost increase and weight increase.

In order to achieve the above object, the present invention is an internal gear incorporated in a speed reducer and having a tooth surface on the inner periphery, and a ring-shaped gear portion having the tooth surface and an output shaft of the speed reducer And a main body portion having an outer peripheral portion for holding the outer periphery of the gear portion, the gear portion is formed of sintered metal, and the main body portion is made of resin using the gear portion as an insert part. It is characterized by being formed of a molded body formed by injection molding.

If the gear part is formed of sintered metal in this way, the fatigue resistance and mechanical strength of the tooth surface can be increased as compared with the case where the gear part is formed of resin. On the other hand, if the main body is formed of resin, the internal gear can be reduced in cost and weight. In addition, since the entire body including the shaft support is formed of resin, the center case 101 (see FIG. 6) having a complicated shape as required in Patent Document 1 is not required, and the weight and the cost are reduced. This is even more advantageous for achieving the above. In addition, since the outer peripheral portion for holding the outer periphery of the gear portion is provided in the main body portion, after the main body portion is injection-molded, the outer peripheral portion is pressed against the outer peripheral surface of the gear portion by molding shrinkage when cooled and solidified. And the bonding strength of the main body can be strengthened. Therefore, the durability life of the internal gear can be increased while suppressing an increase in weight and cost.

Of the gear part, the surface porosity of the surface that contacts the main body is made larger than the surface porosity of the tooth surface, or the open porosity of the part of the gear that contacts the main body is determined by the tooth part. If it is larger than the open porosity, the coupling force between the gear part and the main body part can be increased by the anchor effect by the resin that has entered the surface pores. On the other hand, the fatigue resistance and mechanical strength of the tooth surface can be increased.

Of the gear portion, the surface area ratio of the surface that contacts the main body portion is preferably 10% or more and 50% or less. Moreover, it is preferable that the surface aperture ratio of the tooth surface of the gear portion is 40% or less.
Of the gear part, the open porosity of the part in contact with the main body part is preferably 10% or more and 50% or less. The open porosity of the gear teeth is preferably 40% or less.

If it is a reduction gear which has the above interle gear, the durable life can be improved, avoiding the weight increase and cost increase of a reduction gear. Further, if this reduction gear is used for a starter of a vehicle equipped with an idling stop mechanism, early replacement of the reduction gear and the starter can be prevented, and the maintenance cost of the vehicle can be reduced.

  As described above, according to the present invention, it is possible to increase the durability of the internal gear for a speed reducer while minimizing cost increase and weight increase.

It is sectional drawing which shows schematic structure of a starter. It is sectional drawing of the reduction gear using the internal gear concerning this invention. It is a perspective view which shows the decomposition | disassembly state of a reduction gear. It is a perspective view which shows the assembly state of a reduction gear. It is sectional drawing which expands and shows the tooth surface of an internal gear. It is sectional drawing which shows the reduction gear for the conventional starters.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 shows a simplified configuration of a typical starter ST. As shown in FIG. 1, the starter ST includes a motor 4, a speed reducer 5, an overrunning clutch 6 (hereinafter simply referred to as a clutch), a pinion gear 7, a lever 8, and an electromagnetic switch 9 as main components. It is. The lever 8 is rotatable about a fulcrum O, and the tip thereof is disposed on the input side (motor 4 side) of the overrunning clutch 6. The overrunning clutch 6 is a one-way clutch, and an output shaft 5a (reduction gear output shaft) of the speed reducer 5 is coupled to an input side of the overrunning clutch 6 through a spline or the like so as to be slidable in the axial direction. A pinion gear 7 is attached to the output shaft 6 a (clutch output shaft) of the clutch 6. Therefore, the clutch 6 can move in the axial direction integrally with the clutch output shaft 6 a and the pinion gear 7. The reduction gear 5 and the clutch 6 are disposed inside a first case 11 as a gear case, and the motor 4 is disposed inside a second case 12 as a motor case. The first case 11 and the second case 12 are connected by an appropriate connection structure such as a bolt.

When an engine start command is input, the electromagnetic switch 9 is turned on to apply a rotational force in the direction of the arrow in the drawing to the lever 8, and the clutch 6, the clutch output shaft 6a, and the pinion gear 7 are integrated into the shaft. Move to the opposite side of the motor 4 in the direction. As a result, the pinion gear 7 meshes with the ring gear 10 coupled to the crankshaft of the engine. Further, the motor 4 is driven, and the output torque is transmitted to the pinion gear 7 via the speed reducer 5 and the clutch 6. As a result, the motor output is transmitted to the crankshaft via the ring gear 10 and the engine is started. After the engine is started, the electromagnetic switch 9 is turned off, the clutch 6 and the pinion gear 7 are retracted, and the pinion gear 7 is disengaged from the meshing position with the ring gear 10. The engine torque immediately after starting the engine is not transmitted to the motor 4 because it is interrupted by the clutch 6.

In FIG. 2, the typical structural example of the reduction gear 5 used for starter ST is shown. The reduction gear 5 is a planetary gear mechanism, and includes a sun gear 51 made of an external gear disposed on an axis O, an internal gear 52 fixed to a stationary member, a planetary gear 53 made of an external gear, and a planetary gear. And a plate-like carrier 54 that supports 53. The planetary gear 53 is disposed between the sun gear 51 and the internal gear 52 and is in mesh with both the gears 51 and 52. An output shaft 4a of the motor 4 is coupled to the sun gear 51 through a serration 61 (including splines; the same applies hereinafter) so as to transmit torque.

As shown in FIGS. 3 and 4, the planetary gears 53 are arranged at a plurality of locations (for example, three locations) equally arranged in the circumferential direction. As shown in FIGS. 2 to 4, a pin 55 having one end fitted and fixed to the hole of the plate-like carrier 54 is inserted in the inner periphery of each planetary gear 53, and each planetary gear 53 is arranged on the inner periphery thereof. A sliding bearing 56 is supported so as to be rotatable with respect to the pin 55. As shown in FIG. 2, the reduction gear output shaft 5 a is inserted into the inner periphery of the carrier 54, and the reduction gear output shaft 5 a and the carrier 54 are coupled via a serration 62 so that torque can be transmitted.

As shown in FIG. 2, one end (for example, the motor output shaft 4a) of the output shaft 4a of the motor 4 and the output shaft 5a of the speed reducer is formed at the shaft end of the other (for example, the speed reducer output shaft 5a). By inserting the slide bearing 63 between the two, the shafts 4a and 5a can be rotated relative to each other in a coaxial state. On the motor 4 side of the internal gear 52, a shielding plate 65 having an inner diameter end close to the outer peripheral surface of the output shaft 4a of the motor 4 is arranged. Intrusion of foreign matter into the speed reducer 5 is prevented.

In the above configuration, when the sun gear 51 is rotationally driven by the motor 4, the planetary gear 53 revolves around the axis O while rotating. In response to the revolution movement of the planetary gear 53, the carrier 54 rotates about the axis O, so that the speed reducer output shaft 5a coupled to the carrier 54 so as to transmit torque is rotated. As a result, the output of the motor 4 is decelerated and transmitted to the reducer output shaft 5a, and further transmitted to the pinion gear 7 via the clutch 6 (see FIG. 1).

As shown in FIG. 2, the internal gear 52 includes a gear part 52a and a main body part 52b. The gear part 52a is made of a ring-shaped sintered metal material, and a tooth part 525 having a large number of tooth surfaces 521 (see FIG. 3) is formed on the inner periphery thereof.

The main body 52b has a substantially cylindrical shape with a reduced diameter on one axial end (on the side opposite to the motor), a large-diameter outer peripheral portion 522 that covers the outer diameter of the gear 52a, and an axial end on the one end. A small-diameter shaft support portion 523 extending in the axial direction at the inner diameter end, and an outer peripheral portion 522 and the shaft support portion 523 are connected to each other, and a connecting portion 524 whose diameter is gradually reduced from the outer peripheral portion 522 to the shaft support portion 523 is integrally provided. On the motor 4 side of the internal gear 52, the end surface of the gear portion 52a and the end surface of the main body portion 52b are flush with each other. A carrier 54 is disposed on the inner diameter side of the connecting portion 524.

The internal gear 52 is fixed to the stationary side (the first case 11 or the second case) by sandwiching the outer peripheral portion 522 of the main body portion 52b between the first case 11 and the second case 12 from both sides in the axial direction. . At this time, it is preferable to provide a rotation stopper between the main body 52b and one case (for example, the first case 11). In addition, a sliding bearing 64 is press-fitted and fixed to the inner peripheral surface of the shaft support portion 523 in the main body portion 52 b, and one end (motor side end portion) of the reduction gear output shaft 5 a is connected to the internal gear 52 by the sliding bearing 64. Is supported so as to be freely rotatable.

The internal gear 52 described above is an insert part in which a gear part 52a manufactured by a powder metallurgy method is placed in a mold, and the gear part 52a is positioned in a predetermined position in the mold. It is manufactured by injecting resin and molding (insert molding) the main body 52b. Hereinafter, the composition and manufacturing procedure of the gear part 52b and the main body part 52b will be described in detail.

[Gear part]
The gear part 52a is formed of an iron-based sintered body. Specifically, iron powder is the main component, a raw material powder in which copper powder and graphite powder are mixed is compressed to form a green compact, and then the green compact is sintered to form the gear portion 52a. A sintered body having a corresponding shape is obtained.

This sintered body contains, for example, Cu: 1 to 8 mass%, C: 0.2 to 1 mass%, and the balance is Fe and inevitable impurities. The sintering temperature is preferably 1100 ° C to 1150 ° C. By sintering at this temperature, the molten Cu diffuses into Fe and strengthens the bonding force between the Fe structures. Moreover, since Fe reacts with C contained in the graphite powder, the Fe structure after sintering becomes a hard pearlite phase. Therefore, the strength of the sintered body can be increased. In order to sufficiently form the pearlite phase, the atmosphere gas of the sintering furnace is a gas containing carbon such as carbon monoxide or carbon dioxide, for example, liquefied petroleum gas such as butane gas or propane gas and air, and Ni catalyst. It is preferable to use an endothermic gas (RX gas) pyrolyzed in (1).

The sintered body after sintering is subjected to shaping (sizing) of the tooth surface by plastic working. At the time of the sintered body, as shown by a two-dot chain line in FIG. 5, the portion 521 ′ corresponding to the tooth surface 521 of the gear portion 52a is formed in a rough shape, but this portion 521 ′ is formed by rolling or the like. By plastic working, the portion 521 ′ is shaped into a finished shape (indicated by a solid line) such as an involute shape, and a gear portion 52a having a tooth surface 521 on the inner periphery is completed. In this plastic working, as shown in FIG. 5, it is preferable to finish each tooth portion 525 including the tooth surface 521 by compressing in the circumferential direction and extending and deforming in the radial direction.

By performing plastic working by rolling or the like in this manner, the porous structure of the surface layer portion including the tooth surface 521 is densified, and the number of pores serving as stress concentration sources in the surface layer portion is reduced. Further, the hardness of the tooth surface 521 becomes higher than that of the core portion (at this time, the hardness is maximum at the tooth surface 521, gradually decreases toward the core portion, and becomes constant when exceeding a predetermined depth). Therefore, it is possible to obtain a tooth surface 521 having excellent mechanical strength, particularly fatigue strength. This plastic working may be performed in any temperature range between cold, warm feeling, or hot, but is preferably performed cold considering the shaping accuracy and durability life of the tooth surface 521.

With the shaping of the tooth surface 521, each surface (end surface, outer peripheral surface, etc.) other than the tooth surface 521 of the gear portion 52a is also shaped. At this time, at least the surface of the gear portion 52a in contact with the main body portion 52b (particularly the outer peripheral surface of the gear portion 52a) is made smaller than the amount of compression at the tooth surface 521. It is preferable that the surface area ratio of the surface in contact with the main body portion 52b is larger than that of the tooth surface 521. Or it is preferable to make open porosity of the part which contacts the main-body part 52b at least of the gear part 52a larger than the tooth | gear part 525. FIG. As a result, when the main body 52b is injection-molded with resin, the resin enters the outer peripheral surface of the gear portion 52a or the surface opening of one end surface to exert an anchor effect, so that the coupling between the gear portion 52a and the main body 52b is performed. Strength can be increased. In addition, it is sufficient for the above-described magnitude relationship to satisfy either one of the surface porosity and the open porosity. Of course, you may be satisfied with both.

In order to sufficiently obtain such an anchor effect, the lower limit value of the surface area ratio of the surface (particularly the outer peripheral surface) of the gear portion 52a in contact with the main body portion 52b is 10% or more, preferably 15% or more, more preferably 20% or more. And Further, the open porosity of the portion of the gear portion 52a that contacts the main body portion 52b (the portion of the gear portion 52a excluding the tooth portion 525) is 10% or more, preferably 15% or more, and more preferably 20% or more. On the other hand, if the surface porosity or the open porosity is too large, the strength of the entire gear portion 52a is reduced. Therefore, the surface porosity is 50% or less, preferably 40% or less, and the open porosity is 50% or less, preferably 40% or less. Each of the above limit values only needs to satisfy either the surface porosity or the open porosity. Of course, you may be satisfied with both. For the sake of convenience, the surface open area referred to here is calculated, for example, by taking an image (for example, 500 times) taken with a metal microscope such as Nikon Corporation: ECLIPSE ME600 as image data and calculating the area of the pore portion. You can ask for it. The open porosity is defined by JIS Z 2501: 2000. Incidentally, the open porosity of the measurement object is expressed as a percentage of the volume, and is obtained by dividing the volume of oil after complete impregnation by the volume of the measurement object and multiplying by 100.

Further, the surface area ratio of the tooth surface 521 is 40% or less, preferably 20% or less, more preferably 10% or less, in order to ensure the strength. For the same reason, the open porosity of the tooth portion 525 is 40% or less, preferably 20% or less, and more preferably 10% or less. If the open porosity of the tooth surface 521 is too small, the molding pressure when molding the compact must be excessively increased, which is disadvantageous in terms of cost and the like. Is preferably set to 5% or more. For the same reason, the open porosity of the tooth portion 525 is preferably set to 5% or more. Each of the above limit values only needs to satisfy one of the surface porosity and the open porosity. Of course, you may be satisfied with both.

[Main unit]
As a resin material constituting the main body 52b, which is a resin molded body, any material that can be injection-molded can be used. Of the resin materials, those based on polyamide resins having excellent fatigue resistance are preferred. Examples of the polyamide resin include polyamide 6, polyamide 66, polyamide 46, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide MXD, polyamide 6T, and polyamide 6I. In addition, as a fibrous filler mix | blended with these resin, carbon fiber, an aromatic polyamide fiber, or a mixture thereof other than glass fiber can be used widely.

When the illustrated resin material is used, the outer peripheral portion 522 of the main body portion 52b tends to deform in the diameter-reducing direction due to molding shrinkage that occurs at the time of solidification after injection molding, so that the anchor effect is enhanced and the gear portion 52a and the main body portion 52b are strengthened. The bond strength of increases. Therefore, by utilizing the molding shrinkage of the resin in this way, the gear portion 52a and the main body portion 52b can be integrated, and the durability of the internal gear 52 can be improved. By the way, the molding shrinkage rate of unfilled polyamide 6 resin is generally 0.5 to 1.5%, the molding shrinkage rate of unfilled polyamide 66 resin is generally 0.8 to 1.5%, filled with glass fiber, etc. The molding shrinkage rate of the polyamide 6 resin is generally 0.4 to 0.8%, and the molding shrinkage rate of the polyamide 66 resin filled with glass fiber or the like is generally 0.2 to 1.0%.

The apparent melt viscosity of the base resin is preferably in the range of 1000 poise to 10,000 poise. If the apparent melt viscosity is lower than the lower limit value, there remains anxiety about the strength of the main body 52b. On the other hand, if the apparent melt viscosity is higher than the upper limit value, the melt viscosity becomes too high and the moldability is lowered, and the resin material in the molten state is less likely to enter the open pores on the surface of the gear portion 52a, thus reducing the anchor effect. To do.

The molecular weight of the base resin is preferably in the range of 13,000 to 30000 in terms of number average molecular weight considering injection moldability, and in the range of 18000 to 25000 in terms of number average molecular weight considering fatigue resistance and high molding accuracy. When the number average molecular weight is less than 13,000, the molecular weight is too low and the fatigue resistance becomes low. On the other hand, when the number average molecular weight exceeds 30000, the fatigue resistance is improved. However, in order to achieve the required mechanical strength such as impact strength, for example, when 10 to 50% by mass of glass fiber is contained, The melt viscosity exceeds the upper limit (10000 poise), and it becomes difficult to ensure the molding accuracy of the main body 52b during injection molding.

Moreover, a copolymerized polyamide resin can also be used as the base resin. Specific examples of the copolymerized polyamide resin include polycaproamide / polyhexamethylene adipamide copolymer (polyamide 6/66), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (polyamide 66 / 6T), polyhexa Methylene adipamide / polyhexamethylene isophthalamide copolymer (polyamide 66 / 6I), polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (polyamide 66 / 6T / 6I), polyxylylene azide Pamide (polyamide XD6) etc. are mentioned.

Examples of the amount of each component of the above-described polycaproamide / polyhexamethylene adipamide copolymer (polyamide 6/66) include 98 to 80% by mass of polyamide resin 6 components and 2 to 20% by mass of polyamide resin 66 components. Examples thereof include a polymerized polyamide resin or a copolymerized polyamide resin composed of 98 to 80% by mass of 66 components of polyamide resin and 2 to 20% by mass of 6 components of polyamide resin.

When the copolymerized polyamide resin is used, the affinity with the glass fiber is improved as compared with the case where the homopolymerized polyamide resin is a main component. Therefore, the orientation of the glass fiber in the molten resin composition is moderately relaxed, and for example, the difference in molding shrinkage (%) between the flow direction and the direction perpendicular to the flow can be reduced. On the other hand, it is possible to maintain the excellent tensile strength, bending strength, and compressive strength exhibited by ordinary glass fiber reinforced polyamide resins. As the copolymerized polyamide resin having such good characteristics, for example, a 6/66 copolymerized polyamide resin having a polyamide resin 6 and a polyamide resin 66 as a copolymerization component is preferably used.

If the internal gear 52 described above is used for the speed reducer 5, the following operational effects can be obtained.

Since the gear portion 52a of the internal gear 52 is formed of sintered metal, the fatigue resistance and mechanical strength of the tooth surface 521 can be increased. On the other hand, since the main body portion 52b other than the gear portion 52a of the internal gear 52 is formed of resin, the cost and weight of the internal gear 54 can be reduced. Therefore, compared with the conventional product (Patent Document 1) in which the entire internal gear 52 is formed of resin, the life can be extended while suppressing the increase in weight and cost. Therefore, even when the internal gear 52 of the present invention is used for the speed reducer 5 for the vehicle starter equipped with the idling stop mechanism, the starter does not reach the end of its life early, and the maintenance cost of the vehicle can be reduced.

In the present invention, the main body 52b of the internal gear 52 is configured to include a shaft support 523 that supports the reduction gear output shaft 5a, and the entire main body 52b including the shaft support 523 is formed of resin. Therefore, the center case 101 (see FIG. 6) having a complicated shape as described in Patent Document 1 is not necessary. Therefore, the reduction gear 5 is further effective in reducing the weight and cost.

In addition, since the outer peripheral portion 522 that holds the outer periphery of the gear portion 52a is provided in the main body portion 52b, after the main body portion 52b is injection-molded, the outer peripheral portion 522 is compressed in the diameter reducing direction by molding shrinkage when cooled and solidified. Can generate power. Accordingly, the coupling force between the gear portion 52a and the main body portion 52b can be strengthened. Preferably, if the thickness in the radial direction of the outer peripheral portion 522 is the largest in the main body portion 52b, the amount of molding shrinkage in the reduced diameter direction generated in the outer peripheral portion 522 can be increased, and the gear portion and the main body portion 52b can be increased. The binding force can be further strengthened. Further, if the thickness in the radial direction of the shaft support portion 523 is made the smallest in the main body portion 52b, it is possible to avoid an adverse effect on the slide bearing 64 (variation of the bearing gap, etc.) due to molding shrinkage in this portion.

At this time, in the gear portion 52a, the surface porosity of the tooth surface 521 and the teeth are set so that the surface porosity of the surface in contact with the main body portion 52b and the open porosity of the portion in contact with the main body portion 52b are 10% or more and 50% or less. By making it larger than the open porosity of the portion 525, the anchor effect at the boundary between the gear portion 52a and the main body portion 52b can be strengthened, and the coupling force between the gear portion and the main body portion 52b can be further increased. Become. In order to further increase the coupling force between the gear portion 52a and the main body portion 52b, particularly in the circumferential direction, concave portions and convex portions (key grooves, serrations, etc.) are formed on the outer peripheral surface of the gear portion 52a, and the outer periphery of the gear portion 52a and the main body portion 52a. The part 522 may be engaged in the circumferential direction.

  In the above description, the case where the slide bearing 64 is press-fitted and fixed to the inner periphery of the shaft support portion 523 of the main body portion 52b is illustrated. However, the main body portion 52b is injected with resin by using the slide bearing 64 as an insert part together with the gear portion 52a. You may shape | mold. Further, if the main body 52b is formed of a resin material having excellent slidability, the reduction gear output shaft 5a can be supported directly on the inner peripheral surface of the shaft support 523 without using the sliding bearing 64.

In the above description, the case where the internal gear 52 is used for the planetary gear mechanism has been described. However, the internal gear 52 of the present invention is not limited to the planetary gear mechanism, and can be widely used for reduction gears of other configurations. Can do.

4 Motor 4a Motor output shaft 5 Reducer 5a Reducer output shaft 6 Overrunning clutch 7 Pinion gear 52 Internal gear 52a Gear portion 52b Body portion 64 Slide bearing 521 Tooth surface 522 Outer portion 523 Shaft support portion

Claims (9)

An internal gear incorporated in the speed reducer and having a tooth surface on the inner periphery,
A gear portion having a ring-shaped gear portion including a tooth portion including the tooth surface, a shaft support portion that supports an output shaft of the reduction gear, and a peripheral portion that holds an outer periphery of the gear portion; The internal gear is formed of a sintered metal, and the main body portion is formed of a molded body formed by injection molding with a resin using the gear portion as an insert part.   The internal gear according to claim 1, wherein a surface area ratio of a surface of the gear portion that contacts the main body is larger than a surface area ratio of the tooth surface. The internal gear according to claim 1 or 2, wherein an open porosity of a portion in contact with the main body portion of the gear portion is larger than an open porosity of the tooth portion. The internal gear according to any one of claims 1 to 3, wherein a surface area ratio of a surface in contact with the main body portion of the gear portion is 10% or more and 50% or less. The internal gear according to any one of claims 1 to 4, wherein an open porosity of a portion in contact with the main body portion of the gear portion is 10% or more and 50% or less. The internal gear according to any one of claims 1 to 5, wherein the surface area of the tooth surface of the gear portion is 40% or less. The internal gear according to any one of claims 1 to 6, wherein an open porosity of a tooth portion of the gear portion is 40% or less. A reduction gear having the internal gear according to any one of claims 1 to 7.   The speed reducer according to claim 8, which is used for a starter of a vehicle equipped with an idling stop mechanism.

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