JP6400491B2 - Inscribed planetary gear unit - Google Patents

Description

  The present invention relates to an inscribed planetary gear device.

  The internal planetary gear device includes an internal gear with internal teeth, an external gear with external teeth, and a rotation around a central axis of the internal gear, and the internal teeth and the external teeth are And an eccentric member that rotatably supports the external gear around an axis that is eccentric with respect to the central axis of the internal gear in a meshed state. In the internal planetary gear device, the number of teeth of the internal gear is at least one less than the number of teeth of the external gear, the eccentric member is an input member, and either the internal gear or the external gear is a fixed member, By using the other as an output member, it is used as a reduction gear (hypocycloid type reduction gear).

  In the conventional inscribed planetary gear device, the inner teeth and the outer teeth are based on a tooth profile based on an involute curve or a trochoid curve (for example, Patent Document 1).

JP2013-142459A

  The tooth profile based on the involute curve or trochoid curve is a tooth profile that gradually decreases the tooth thickness from the root side to the tip side, and is due to the tooth profile that makes the meshing pressure angle positive. The radial component force generated by the meshing acts in a direction in which the teeth are separated from each other, that is, in a direction in which the meshing is separated.

  For this reason, in such a tooth profile, in order to increase the torque transmission efficiency and to avoid the tooth skipping phenomenon (ratchet phenomenon), the eccentric pressing force in the radial direction between the inner teeth and the outer teeth is increased. It is necessary to increase the meshing force by raising it. However, if the meshing pressure is high, tooth surface wear becomes severe and a problem occurs in the durability of the gear.

  The problem to be solved by the present invention is to achieve high torque transmission efficiency without increasing the meshing pressure in the inscribed planetary gear device and to prevent the tooth skipping phenomenon from occurring.

  An internal planetary gear device according to the present invention includes an internal gear (10) having internal teeth (12), an external gear (20) having external teeth (22), and the internal gear (10). The external gear (20) is eccentric with respect to the central axis of the internal gear (10) with the internal teeth (12) and the external teeth (22) meshing with each other. An internal planetary gear device having an eccentric member (30) rotatably supported around the axis line, wherein the internal teeth (12) and the external teeth (22) have at least a partial meshing pressure angle. This is a negative tooth profile. The tooth profile of the portion (12A, 22A) where the meshing pressure angle is negative is a tooth profile in which the tooth thickness gradually increases from the tooth base side toward the tooth tip side.

  In meshing with a negative meshing pressure angle, the component force (Fb) in the radial direction of the reaction force (Fa) due to the meshing pressure between the inner teeth (12) and the outer teeth (22) is the direction in which the teeth approach each other in the radial direction. Acts in the direction of deepening the mesh. As a result, a positive meshing state is ensured without increasing the eccentric pressing force, high torque transmission efficiency is obtained, and tooth skipping does not occur.

  In the internal planetary gear device according to the present invention, preferably, the internal teeth (12) and the external teeth (22) have a negative meshing pressure angle from the initial meshing stage to the middle meshing period, and the meshing pressure angle is positive at the final meshing stage. Tooth shape that becomes. The tooth profile of the portion (12E, 22E) where the meshing pressure angle becomes positive is a tooth profile in which the tooth thickness gradually decreases from the tooth base side toward the tooth tip side.

  According to this configuration, since the meshing pressure angle is meshed with positive at the end of meshing, the torque transmission efficiency is improved accordingly.

  The inscribed planetary gear device according to the present invention preferably has a tooth profile in which a portion (22A) where the meshing pressure angle is negative and a portion (22E) where the meshing pressure angle is positive are connected by an arc (22F). is there.

  According to this configuration, the internal teeth (12) and the teeth (12) and the portion (22A) where the meshing pressure angle is negative and the portion (22E) where the meshing pressure angle is positive have a sharp shape as compared with the case where The wear of the external teeth (22) is reduced, and the durability of the gear is improved.

  In the internal planetary gear device according to the present invention, preferably, the shape of the tooth groove (14) of the internal gear (10) meshes with the external teeth (22) so as not to interfere with the external teeth (22). It is the same shape as the contour shape defined by the trajectory or a shape approximate to the contour shape.

  According to this configuration, the internal gear (10) and the external gear (20) mesh with each other well without interfering with each other.

  According to the inscribed planetary gear device according to the present invention, the component force in the radial direction of the reaction force caused by the meshing pressure between the inner teeth and the outer teeth acts in the direction in which the teeth approach each other in the radial direction, so that the meshing pressure is increased. Therefore, high torque transmission efficiency can be obtained, and the tooth skipping phenomenon does not occur.

The front view which shows one Embodiment of the inscribed planetary gear apparatus by this invention. The front view which expands and shows the internal tooth of the internal type planetary gear apparatus by this embodiment. The front view which expands and shows the external tooth of the inscribed planetary gear apparatus by this embodiment. Explanatory drawing which shows the movement locus | trajectory of the external tooth with respect to the internal tooth of the internal planetary gear apparatus by this embodiment. The partial front view which shows the meshing state 1 of the inscribed planetary gear apparatus by this embodiment. The partial front view which shows the meshing state 2 of the inscribed planetary gear apparatus by this embodiment. The partial front view which shows the meshing state 3 of the inscribed planetary gear apparatus by this embodiment. The partial front view which shows the meshing state 4 of the inscribed planetary gear apparatus by this embodiment. The partial front view which shows the meshing state 5 of the inscribed planetary gear apparatus by this embodiment. The partial front view which shows the meshing state 6 of the inscribed planetary gear apparatus by this embodiment. The partial front view which shows the meshing state 7 of the inscribed planetary gear apparatus by this embodiment. Explanatory drawing which shows the reaction force at the time of meshing | engagement of the inscribed planetary gear apparatus by this embodiment.

  Embodiments of an inscribed planetary gear device according to the present invention will be described below with reference to FIGS.

  The inscribed planetary gear device has an annular internal gear 10 as shown in FIG. A series of internal teeth 12 are formed in the circumferential direction on the inner peripheral portion of the internal gear 10. The internal gear 10 is fixed to a fixing member (not shown) and forms a reaction force element. An annular external gear 20 is arranged inside the internal gear 10. A series of external teeth 22 are formed on the outer peripheral portion of the external gear 20 in the circumferential direction. The number of teeth Zb of the external teeth 22 is one less than the number of teeth Za of the internal teeth 12, and the pitch circle radius of the external gear 20 is smaller than the pitch circle radius of the internal gear 10.

  The internal gear 10 and the external gear 20 are configured by a laminated structure of a plurality of thin metal plates that have been press-formed or laser cut.

  An eccentric member 30 is disposed inside the external gear 20. The eccentric member 30 has a central shaft portion 32 concentric with the internal gear 10 and an eccentric shaft portion 34 that is eccentric with respect to the central shaft portion 32. The eccentric member 30 has a central shaft portion 32 supported by a fixing member (not shown) so as to be rotatable around the central axis of the central shaft portion 32, and the external gear 20 is mounted on the outer peripheral portion of the eccentric shaft portion 34 by a bearing 36. The teeth 12 and the outer teeth 22 are supported so as to be rotatable around the central axis of the eccentric shaft portion 34 in a state where the teeth 12 and the outer teeth 22 are engaged with each other. In other words, the eccentric member 30 is rotatable about the central axis of the internal gear 10 by supporting the central shaft portion 32 so as to be fixed to a fixing member (not shown). In a state where the teeth 12 and the external teeth 22 are engaged with each other, the external gear 20 is rotatably supported around an axis that is eccentric with respect to the central axis of the internal gear 10.

  In this configuration, the eccentric member 30 serves as an input element that is rotationally driven around the central axis of the central shaft portion 32, and only the rotational component of the external gear 20 around the central axis of the central shaft portion 32 is extracted by an Oldham coupling or the like. As a result, the external gear 20 forms an output element.

  In FIG. 1, the symbol A indicates the center of the internal gear 10 and the central shaft portion 32, and the symbol B indicates the center of the external gear 20 and the eccentric shaft portion 34.

  In this inscribed planetary gear device, the rotation of the eccentric member 30 about the center A causes the external gear 20 to rotate (rotate) around the central axis of the eccentric shaft portion 34, that is, about the center B as a rotation center. However, the external gear 20 rolls on the inner periphery of the internal gear 10 with the internal teeth 12 and the external teeth 22 engaged. The external gear 20 performs an internal cycloid movement with respect to the internal gear 10.

Thereby, a hypocycloid type reduction gear having a reduction ratio according to the equation is obtained.
Reduction ratio = Zb / (Za−Zb) = Zb / 1 = Zb

  In the above-described inscribed planetary gear device, when the eccentric member 30 rotates in the counterclockwise direction as viewed in FIG. The movement trajectory (meshing trajectory) with respect to the internal teeth 12 at the point that protrudes most in the circumferential direction (see FIG. 3) is as indicated by the symbol D in FIG.

  As shown in FIGS. 2 and 3, the tooth profile of the inner teeth 12 and the outer teeth 22 is such that the meshing pressure angle becomes negative from the initial meshing stage to the middle meshing stage, and the meshing pressure angle is positive at the final meshing stage. Tooth shape that becomes.

  When the meshing pressure angle is negative, the tooth thickness gradually increases as it goes from the tooth base side to the tooth tip side, and the tooth surface of the inner tooth 12 or the outer tooth 22 is viewed from the tooth tip side to the tooth bottom side. Becomes an overhanging surface. On the other hand, when the meshing pressure angle is positive, a tooth profile is formed in which the tooth thickness gradually decreases from the tooth base side to the tooth tip side.

  In the inner teeth 12 and the outer teeth 22, the portions where the meshing pressure angle is negative are the negative inclined portions 12 </ b> A and 22 </ b> A of the end of the teeth. Is gradually increasing. The tooth root side from the negative inclined portions 12A and 22A has a tooth profile that reaches the tooth bottom portions 12C and 22C through the fillet curve portions 12B and 22B.

  In the inner teeth 12 and the outer teeth 22, the portions where the meshing pressure angle is positive are the positive inclined portions 12E and 22E on the tooth tip side of the negative inclined portions 12A and 22A, and the positive inclined portions 12E and 22E are from the tooth root side. The tooth thickness gradually decreases toward the tooth tip side. The positive inclined portion 22E and the negative inclined portion 22A of the external tooth 22 are smoothly connected by an arc portion 22F. The circular arc portion 22F forms a portion (a portion corresponding to the tooth tip vicinity point C) where the outer teeth 22 protrude most in the circumferential direction.

  The tooth gap 14 defined between the adjacent internal teeth 12 has an outer peripheral locus of the external teeth 22 in order to avoid interference with the external teeth 22 assuming that the tooth tip vicinity point C of the external teeth 22 performs a hypocycloidal movement. The shape is almost the same as the contour shape defined by. As a result, the internal gear 10 and the external gear 20 do not interfere with each other, and good meshing between the internal teeth 12 and the external teeth 22 is ensured.

  Strictly speaking, in this portion, the tooth gap 14 is not provided so that friction loss due to sliding contact between the bottom portion (tooth bottom portion 12C) of the tooth groove 14 not involved in torque transmission and the tooth tip portion 22D of the external tooth 22 does not occur. The tooth gap 14 is formed so that a gap 16 (see FIG. 7) is formed between the bottom portion (the tooth bottom portion 12 </ b> C) and the tooth tip portion 22 </ b> D of the external tooth 22.

  Although it is difficult to create the internal teeth 12 and the external teeth 22 including the overhang portion by the above-described tooth profile by cutting with a hob cutter or the like, the internal gear 10 and the external gear 20 are formed by press molding or laser cutting. Further, if it is constituted by a laminated structure of a plurality of thin metal plates, the tooth profile design is highly flexible and a tooth profile including an overhang portion can be easily manufactured. Thereby, the internal gear 12 by the above-mentioned tooth profile, the internal gear 10 by the external gear 22, and the external gear 20 can be easily realized with high productivity.

  5 to 11 show the meshing state of the internal teeth 12 and the external teeth 22 at each position in the circumferential direction of the internal gear 10. The rotation direction of the external gear 20 in the illustrated example is a counterclockwise direction. In the following description, the position (maximum eccentric position) at which the outer teeth 22 engage with the inner teeth 12 most deeply is defined as the origin position X (see FIG. 1), and the position behind the rotational direction is rotated from the position of the front angle. The position on the direction advance side is called the rear angle position.

  As shown in FIG. 5, the inner teeth 12 and the outer teeth 22 start to be engaged by the negative inclined portions 12A and 22A at a position of about 90 degrees forward. The meshing by the negatively inclined portions 12A and 22A continues to the rotational angle position near the origin position, as shown in FIG. Thereby, the meshing pressure angle of the internal teeth 12 and the external teeth 22 becomes negative from the initial meshing to the middle.

  At the origin position X, as shown in FIG. 7, the negatively inclined portions 12 </ b> A and 22 </ b> A are separated from each other, and the tooth tip portion 22 </ b> D of the external tooth 22 comes closest to the bottom portion of the tooth gap 14.

  As shown in FIG. 8, in the section from the origin position X to a position of about 90 degrees, the negative inclined portions 12A and 22A on the side where torque transmission is not performed (turning direction delay side) are in contact with each other. The tooth 22 moves in the direction of coming out of the tooth gap 14. At a position of about 90 degrees afterward, as shown in FIG. 9, the meshing between the forward inclined portions 12E and 22E starts. As shown in FIG. 10, the meshing between the forward inclined portions 12E and 22E continues to a position of about 135 degrees. At a position on the further forward side in the rotational direction, as shown in FIG. 11, the forward inclined portions 12E and 22E are separated from each other, and the meshing between the inner teeth 12 and the outer teeth 22 is completed. Thereby, the meshing pressure angle of the internal teeth 12 and the external teeth 22 becomes positive at the end of meshing.

  In meshing with a negative meshing pressure angle generated from the initial meshing stage to the middle stage as described above, the component force Fb in the radial direction of the reaction force Fa due to the meshing pressure between the inner teeth 12 and the outer teeth 22 is as shown in FIG. From the meshing pressure angle, the teeth act in the direction in which the teeth approach each other in the radial direction, that is, in the direction in which the meshing becomes deep. As a result, the resistance to displacement in the direction of disengagement increases from the initial stage to the middle stage where the tooth skip phenomenon is likely to occur. Thus, a reliable meshing state is ensured without increasing the meshing pressure, and high torque transmission efficiency is obtained. Further, the tooth skipping phenomenon does not occur under a reliable meshing state.

  At the end of meshing, there is a meshing with positive meshing pressure angle, so that the torque transmission efficiency is improved accordingly. Since this meshing occurs at the rotational angle position after 90 degrees, the radial component of the reaction force due to the meshing pressure is the difference between the internal teeth 12 and the external teeth 22 at the meshing rotational position where the meshing pressure angle is negative. It does not act to release the mesh.

  In the above-described meshing, the portion of the outer teeth 22 that protrudes in the most circumferential direction and contacts the inner teeth 12 is the arc portion 22F, so that the wear on the inner teeth 12 is reduced as compared with a pointed shape. The Thereby, the durability of the internal gear 10 is improved.

  Although the present invention has been described above with reference to preferred embodiments thereof, the present invention is not limited to such embodiments and can be deviated from the spirit of the present invention, as will be readily understood by those skilled in the art. It is possible to change appropriately within the range not to be.

  For example, the positively inclined portions 12E and 22E of the internal teeth 12 and the external teeth 22 are not essential, and the internal teeth 12 and the external teeth 22 may have a tooth shape that meshes at least partially and has a negative pressure angle. The tooth form is basically a trapezoidal tooth form in which the tooth thickness gradually increases from the tooth base side toward the tooth tip side, as indicated by a virtual line E in FIG.

  Further, the tooth profile of the external tooth 22 can be generated based on the locus of relative movement as viewed from the external tooth 22 of the internal tooth 12. As a result, the inner teeth 12 and the outer teeth 22 come into contact with each other, thereby increasing the meshing area and relieving stress.

  The number of teeth Zb of the external teeth 22 is preferably one less than the number of teeth Za of the internal teeth 12 in order to obtain a large reduction ratio. However, this difference in the number of teeth may be other than 1, such as 2, 3. . Although the internal gear 10 is used as a fixed element and the external gear 20 is used as an output element, the internal gear 10 can be used as an output element using the external gear 20 as a fixed element.

DESCRIPTION OF SYMBOLS 10 Internal gear 12 Internal tooth 12A Negative inclination part 12B Thick curve part 12C Tooth bottom part 12E Positive inclination part 14 Tooth groove 16 Crevice 20 External gear 22 External tooth 22A Negative inclination part 22D Tooth tip part 22E Positive inclination part 22F Arc part 30 Eccentric member 32 Central shaft part 34 Eccentric shaft part 36 Ball bearing

Claims (6)

An internal gear with internal teeth;
An external gear with external teeth;
The external gear is rotatable about a central axis of the internal gear, and the external gear is supported rotatably about an axis eccentric with respect to the central axis of the internal gear in a state where the internal teeth and the external teeth are engaged with each other. An inscribed planetary gear device having an eccentric member that comprises:
The internal planetary gear device, wherein the internal teeth and the external teeth are tooth shapes in which at least a part of the internal teeth and the external pressure angle are negative.   2. The inscribed planetary gear device according to claim 1, wherein the tooth profile of the portion where the meshing pressure angle becomes negative is a tooth profile in which the tooth thickness gradually increases from the tooth base side toward the tooth tip side.   3. The internal planetary gear device according to claim 1, wherein the inner teeth and the outer teeth are tooth shapes in which a meshing pressure angle becomes negative from an initial meshing stage to a middle stage, and a meshing pressure angle becomes positive at a final meshing stage.   4. The inscribed planetary gear device according to claim 3, wherein the tooth profile of the portion where the meshing pressure angle becomes positive is a tooth profile in which the tooth thickness gradually decreases from the tooth base side to the tooth tip side.   The inscribed planetary gear set according to claim 3 or 4, wherein a portion where the meshing pressure angle is negative and a portion where the meshing pressure angle is positive are connected by a circular arc.   The shape of the tooth groove of the internal gear is the same shape as the contour shape defined by the meshing locus of the external teeth so as not to interfere with the external teeth. Inscribed planetary gear unit.

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