JP6748595B2 - Actuator of wave gear reducer and variable compression device of internal combustion engine - Google Patents

Description

The present invention relates to a wave gear reducer and an actuator of a variable compression device for an internal combustion engine.

As a gear used in the wave gear reducer described in Patent Document 1, an involute tooth profile or a special tooth profile in which a locus curve of a wave gear motion is applied to a tooth profile has been used.

JP 2012-251446 A

However, in the above-mentioned conventional technology, in these tooth profiles, an involute tooth profile can produce a highly accurate tooth profile more easily than the conventional technology, but since the tooth profile is not suitable for the wave gear motion, the allowable upper limit of torque is low. Becomes Further, the special tooth profile has an excellent allowable torque because the curve of the motion locus is applied to the tooth profile, but there is a risk that the efficiency is reduced because the tooth profile always has the maximum contact surface.
An object of the present invention is to provide a wave gear reducer and an actuator for a variable compression ratio device of an internal combustion engine, which can improve load torque performance and suppress a decrease in efficiency.

In one aspect of the present invention, the wave gear reducer is a tooth center portion of an external tooth having a tooth surface formed in a plane through a reference pitch circle, and a tooth tip portion of an outer tooth on the tooth tip side of the tooth center portion. A flexible external gear having a tooth root portion of an external tooth on the tooth root side of the tooth central portion, a tooth central portion of an internal tooth that passes through the reference pitch circle and has a tooth surface formed in a plane, and the tooth Rigidity arranged on the outer periphery of the flexible external gear having a tooth tip portion of the inner tooth on the tooth tip side of the middle portion and a tooth tip portion of the inner tooth on the tooth tip side of the tooth tooth side of the inner tooth. Wave generation that moves the meshing part in the circumferential direction by bending the internal gear and the flexible external gear in the radial direction to partially mesh with the rigid internal gear and rotating around the rotation axis. And a root portion of the outer tooth and a tip portion of the inner tooth have a line segment of an adder cycloid locus of the flexible outer gear, and a tip portion of the outer tooth and the The root portion of the inner tooth has a line segment of an abduction cycloid locus.

Therefore, according to a preferred aspect of the present invention, both load torque performance and efficiency can be improved.

1 is a schematic diagram of an internal combustion engine including an actuator A of a link mechanism for an internal combustion engine of Embodiment 1. FIG. 3 is a sectional view of an actuator A of the link mechanism for the internal combustion engine of the first embodiment. FIG. 2 is an exploded perspective view of a wave gear reducer 21 of Example 1. FIG. 5 is a schematic view showing a meshed state of a flexible external gear 36 and a rigid internal gear 27 of Embodiment 1. FIG. 5 is a schematic view showing the shape of external teeth 36a of the flexible external gear 36 of Example 1. FIG. 5 is a schematic view showing the shape of internal teeth 27a of the rigid internal gear 27 of Example 1. FIG. 5 is a schematic diagram showing the deepest meshing state of the outer teeth 36a of the flexible outer gear 36 and the inner teeth 27a of the rigid inner gear 27 of the first embodiment. FIG. 5 is a schematic diagram showing a state of minute dissociation between an external tooth 36a of a flexible external gear 36 and an internal tooth 27a of a rigid internal gear 27 of Example 1. FIG. 5 is a schematic diagram showing a dissociation progress state between an external tooth 36a of a flexible external gear 36 and an internal tooth 27a of a rigid internal gear 27 of Example 1. FIG. 5 is a diagram showing changes in the effective contact area with respect to the input rotation angle of the flexible external gear 36, the rigid internal gear 27 of Example 1, and the comparative example. FIG.

[Example 1]
FIG. 1 is a schematic diagram of an internal combustion engine including an actuator A of a link mechanism for an internal combustion engine according to a first embodiment. The basic configuration is the same as that shown in FIG. 1 of Japanese Patent Laid-Open No. 2011-169152, and therefore will be briefly described.
An upper end of an upper link 3 is rotatably connected to a piston 1 that reciprocates in a cylinder of a cylinder block of an internal combustion engine via a piston pin 2. A lower link 5 is rotatably connected to a lower end of the upper link 3 via a connecting pin 6. The crankshaft 4 is rotatably connected to the lower link 5 via a crankpin 4a. The upper end of the first control link 7 is rotatably connected to the lower link 5 via a connecting pin 8. The lower end of the first control link 7 is connected to a connecting mechanism 9 having a plurality of link members. The coupling mechanism 9 has a first control shaft 10, a second control shaft (control shaft) 11 and a second control link 12.

The first control shaft 10 extends parallel to the crankshaft 4 extending in the cylinder column direction inside the internal combustion engine. The first control shaft 10 has a first journal portion 10a, a control eccentric shaft portion 10b, and an eccentric shaft portion 10c. The first journal portion 10a is rotatably supported by the internal combustion engine body. The lower end portion of the first control link 7 is rotatably connected to the control eccentric shaft portion 10b. The eccentric shaft portion 10c is rotatably connected to one end portion 12a of the second control link 12. One end of the first arm portion 10d is connected to the first journal portion 10a, and the other end is connected to the lower end portion of the first control link 7. The control eccentric shaft portion 10b is provided at a position eccentric to the first journal portion 10a by a predetermined amount. The second arm portion 10e has one end connected to the first journal portion 10a and the other end connected to one end portion 12a of the second control link 12. The eccentric shaft portion 10c is provided at a position eccentric to the first journal portion 10a by a predetermined amount. The other end 12b of the second control link 12 is rotatably connected to one end of an arm link 13. The second control shaft 11 is connected to the other end of the arm link 13 such that the second control shaft 11 cannot move relatively. The second control shaft 11 is rotatably supported in a housing 20 described later via a plurality of journal portions.

The second control link 12 connects the first control shaft 10 and the second control shaft 11. The second control link 12 has a lever shape, and one end portion 12a connected to the eccentric shaft portion 10c is formed substantially linearly. On the other hand, the other end 12b of the second control link 12 to which the arm link 13 is connected is curved. An insertion hole, through which the eccentric shaft portion 10c is rotatably inserted, is formed at the tip of the one end portion 12a. The arm link 13 is formed as a separate body from the second control shaft 11. The rotational position of the second control shaft 11 is changed by the torque transmitted from the electric motor 22 via the wave gear reducer 21, which is a part of the actuator A of the link mechanism for the internal combustion engine. When the rotational position of the second control shaft 11 is changed, the first control shaft 10 is rotated via the second control link 12 and the position of the lower end portion of the first control link 7 is changed. As a result, the posture of the lower link 5 changes, the stroke position and stroke amount of the piston 1 in the cylinder are changed, and the engine compression ratio is changed accordingly.

Next, the configuration of the actuator A of the link mechanism for the internal combustion engine of the first embodiment will be described.
2 is a sectional view of the actuator A of the link mechanism for the internal combustion engine of the first embodiment, and FIG. 3 is an exploded perspective view of the wave gear reducer 21 of the first embodiment. The actuator A of the link mechanism for an internal combustion engine has an electric motor 22, a wave gear reducer 21, a housing 20, and a second control shaft 11.
The electric motor 22 is, for example, a brushless motor, and has a motor casing 45, a coil 46, a rotor 47, and a motor output shaft 48. The motor casing 45 is formed in a bottomed cylindrical shape. The coil 46 is fixed to the inner peripheral surface of the motor casing 45. The rotor 47 is rotatably provided inside the coil 46. One end of the motor output shaft 48 is fixed to the center of the rotor 47.
The motor output shaft 48 is rotatably supported by a ball bearing 52 provided at the bottom of the motor casing 45. The second control shaft 11 is rotatably supported by the housing 20. The second control shaft 11 has a shaft body 23 and a fixing flange 24. The shaft body 23 extends in the axial direction. The fixing flange 24 is located at one end of the shaft body 23 and rises outward in the radial direction. In the second control shaft 11, a shaft body 23 and a fixing flange 24 are integrally formed of an iron-based metal material. The fixing flange 24 has a plurality of bolt insertion holes formed at equal intervals in the circumferential direction of the outer peripheral portion. A bolt is inserted through this bolt insertion hole to be coupled with the flange portion 36b of the flexible external gear 36 of the wave gear reducer 21.

Next, the configuration of the wave gear reducer 21 of the first embodiment will be described.
The wave gear reducer 21 is attached to the front end side of the electric motor 22 and is housed inside the housing 20. The wave gear reducer 21 is housed in the opening groove portion 20a of the housing 20. Inside the opening groove portion 20a, above the wave gear reducer 21 in the direction of gravity, a supply hole 20b for supplying lubricating oil from a hydraulic source (not shown) or the like opens. When the lubricating oil is supplied from the supply hole 20b, the lubricating oil is dropped on the wave gear reducer 21 below, and lubricates between the rotating elements. The wave gear reducer 21 is bolted into the opening groove portion 20a of the housing 20. The wave gear reducer 21 has a rigid internal gear 27, a flexible external gear 36, and a wave generator 37.
The rigid internal gear 27 is a rigid annular member having a plurality of internal teeth 27a on the inner circumference.

The flexible external gear 36 is arranged on the inner diameter side of the rigid internal gear 27. The flexible external gear 36 has external teeth 36a that mesh with the internal teeth 27a on the outer peripheral surface. The flexible external gear 36 is a thin-walled cylindrical member which is made of a metal material and has a bottom portion and which can be flexibly deformed. The number of external teeth 36a of the flexible external gear 36 is two less than the number of internal teeth 27a of the rigid internal gear 27. An insertion hole 36c through which the second control shaft 11 penetrates is formed on the inner periphery of the flange portion 36b formed at the bottom of the flexible external gear 36. Therefore, the second control shaft 11 is inserted into the insertion hole 36c from the thin-walled cylindrical member side of the flexible external gear 36, and the fixing flange 24 of the second control shaft 11 and the flange portion 36b are coupled with each other by bolts. The inner periphery of the insertion hole 36c can be supported by the second control shaft 11, and the rigidity of the bottom portion of the flexible external gear 36 can be ensured.
The wave generator 37 is formed in an elliptical shape, and the outer peripheral surface slides along the inner peripheral surface of the flexible external gear 36. A motor output shaft 48 is fixed to the center of the wave generation plug 371 by press fitting. The wave generator 37 has a wave generation plug 371 and a deep groove ball bearing 372. The wave generation plug 371 has an elliptical shape. The deep groove ball bearing 372 has a flexible thin inner/outer ring that allows relative rotation between the outer circumference of the wave generation plug 371 and the inner circumference of the flexible outer gear 36.

FIG. 4 is a schematic diagram showing the meshing state of the flexible external gear 36 and the rigid internal gear 27 of the first embodiment. Since the wave generation plug 371 having an elliptical outer shape is fitted into the inner ring of the deep groove ball bearing 372 and follows the elliptical shape, the outer shape of the wave generator 37 is also elliptical. Further, by fitting the wave generator 37 into the inner diameter of the flexible external gear 36, the flexible external gear 36, which is initially circular, is also deformed into an elliptical shape. Since the flexible external gear 36 bent to an ellipse has two teeth less than the rigid internal gear 27, it meshes due to the deviation of the tooth pitch on the major axis of the ellipse, and the tooth pitch matches on the minor axis of the ellipse. Since the flexible external gear 36 is flexed in the axial direction, the teeth do not overlap with each other and do not interfere with each other. Therefore, the flexible external gear 36 and the rigid internal gear 27 having an even multiple difference in the number of teeth can mesh with each other as in the meshed state shown in FIG.
Although the tooth portion of the flexible external gear 36 is flexible, the flange portion 36b cannot be deformed from the circular shape in order to take out the output, and is directly fastened to the second control shaft 11, so the flange portion From 36b as a starting point, the shape expands into an elliptical shape toward the thin-walled cylindrical opening end. That is, the rotational movement of the flexible external gear 36 taken out from the deformation movement near the opening end can be transmitted from the flange portion 36b to the second control shaft 11.

The rotation input to the wave gear reducer 21 is converted by the wave generator 37 into a reciprocating displacement motion in a direction orthogonal to the rotation input shaft. The wave generation plug 371 having the rotation transmission mechanism is driven by the connected input shaft, and the inner ring of the deep groove ball bearing 372 which is a mating partner also follows this. In the outer ring of the deep groove ball bearing 372, the shape of the inner ring is transmitted to the outer ring by the ball sandwiched between the inner ring and the outer ring, but since the ball has 6 degrees of freedom of translation and rotation, the inner ring and the outer ring have independent circumferences. Has directional freedom. Since the wave generation plug 371 driven by the rotation input is an ellipsoid, it has a different radius depending on each position on the circumference of the ellipse. Due to the property of this ellipse, the increase/decrease in the radius due to the rotation of the wave generation plug 371 is transmitted to the outer ring of the wave generation plug 371 via the balls. At this time, since the inner and outer races have the flexible thin wall structure, when the circumferential freedom of the outer race of the deep groove ball bearing 372 is restricted, the outer race performs a deformation motion in synchronization with the increase and decrease of the radius.
Further, since the outer ring of the deep groove ball bearing 372 and the flexible external gear 36 are fitted to each other, the flexible external gear 36 also performs the deforming motion by following the deforming motion of the outer ring. This deformation motion changes the meshing position on the major axis between the rigid internal gear 27 and the flexible external gear 36. As a result, when the tooth portion is enlarged and observed from a fixed point on the rigid internal gear 27, the teeth have relative movement in the direction orthogonal to the axis. Then, the circumferential movement of the flexible external gear 36 with respect to the rigid internal gear 27 is changed by the difference, so that the circumferential movement is superposed, and the external teeth 36a of the flexible external gear 36 are the internal teeth 27a. It moves to the inner diameter side along the tooth surface.

In the first embodiment, aiming at improving both load torque performance and efficiency, the outer teeth 36a of the flexible external gear 36 pass through the reference pitch circle, and the tooth center portion having a flat tooth surface and the abduction. A rigid internal gear that forms a tooth tip portion on the tip side of the tooth center portion having a line segment of a cycloid curve and a tooth tip portion on the tooth root side of the tooth tooth portion having a line segment of an adduction cycloid locus. The inner teeth 27a of 27 pass through the reference pitch circle and have a tooth surface formed into a flat tooth surface, a tooth tip portion on the tooth tip side of the tooth center portion having a line segment of an adduction cycloid locus, and an abduction. The tooth root portion on the tooth root side of the tooth central portion having the line segment of the cycloid locus is formed.
The step of determining the tooth profiles of the rigid internal gear 27 and the flexible external gear 36 in the method for manufacturing the wave gear reducer 21 will be described in detail below.
(i) First determination step In the first determination step, the reduction ratio i, the reference pitch circle radii r _i , r _e of the rigid internal gear 27 and the flexible external gear 36 are determined. The reduction gear ratio i is a reduction gear ratio required for the wave gear reducer 21. The reference pitch circle radius r _i of the rigid internal gear 27 serves as a reference physique of the wave gear reducer 21, and is determined based on, for example, an impact load or a fatigue load (load+rotation speed). The reference pitch circle radius r _e of the flexible external gear 36 before deformation is determined from the reduction ratio i and the reference pitch circle radius r _{i of the} rigid internal gear 27 using the relationship shown in the following formula (1).

ここで、α_INTは内歯27aの圧力角、α_EXTは外歯36aの圧力角、S_INTは内歯27aの歯厚、S_EXTは外歯36aの歯厚、zは減速比iとz=2iの関係で表される外歯36aの歯数である。 (ii) Second determination step In the second determination step, the pressure angle and tooth thickness of the inner tooth 27a and the outer tooth 36a on the reference pitch circle are preliminarily set so as to satisfy the relationships of the following equations (2) and (3). decide.

Where α _INT is the pressure angle of the inner teeth 27a, α _EXT is the pressure angle of the outer teeth 36a, S _INT is the tooth thickness of the inner teeth 27a, S _EXT is the tooth thickness of the outer teeth 36a, and z is the reduction ratio i and z. =2i is the number of external teeth 36a represented by the relationship.

ここで、θは、剛性内歯車27が太陽歯車、可撓性外歯車36が遊星歯車、波動発生器37が遊星キャリアに相当する遊星歯車装置系とした場合における、遊星キャリアの公転角、すなわち波動発生器37への入力回転角に相当する。 (iii) Third determining step In the third determining step, using the tooth profile basic specifications determined in the second determining step, the line segment of the tip abduction cycloid locus of the outer tooth 36a and the tip adduction of the inner tooth 27a are used. Determine the line segment of the cycloid locus.
First, the line segment of the tip adder cycloid locus of the internal tooth 27a uses the adder cycloidal motion curve of the reference pitch circle of the flexible external gear 36 with respect to the reference pitch circle of the rigid internal gear 27. Is expressed by the following equation (4).

Here, θ is the revolution angle of the planetary carrier when the rigid internal gear 27 is a sun gear, the flexible external gear 36 is a planetary gear, and the wave generator 37 is a planetary gear system corresponding to a planetary carrier, that is, It corresponds to the input rotation angle to the wave generator 37.

ここで、ｎ(→)は内転サイクロイド曲線の法線ベクトルを、ｅ(→)_xは水平面を構成する単位ベクトルを指す。 At this time, the line segment used as the tooth tip is determined by the range of the following formula (5).

Here, n(→) indicates a normal vector of the adduction cycloid curve, and e(→) _x indicates a unit vector forming a horizontal plane.

このように、可撓性外歯車36及び剛性内歯車27の歯先歯面と、それぞれに接続される基準ピッチ円径近傍の歯中部の基本歯形である直線歯形が形成される。 Further, in addition to the translational movement due to the above curve, rotation of the outer tooth 36a occurs, so the line segment of the tip abduction cycloid locus of the outer tooth 36a is the abduction cycloid movement represented by the following equation (6). Expressed using a curve.

In this way, the tooth flanks of the flexible external gear 36 and the rigid internal gear 27 and the linear tooth profile that is the basic tooth profile of the central portion of the tooth near the reference pitch circle diameter connected to each are formed.

Further, regarding the root curve of the outer tooth 36a and the inner tooth 27a, since it is represented by the map of the tooth tip curve of the meshing partner, the outer tooth 36a tooth root curve is the above formula (4), the tooth root of the inner tooth 27a. The curve has a shape to which the above equation (6) is applied. The straight section in the vicinity of the reference pitch circle can be arbitrarily determined by adjusting the addendum h _a and the addendum h _f as long as the condition of Expression (5) is satisfied. Is expressed by the equations (7) and (8). Here, m is a module.

FIG. 5 is a schematic view showing the shape of the outer teeth 36a of the first embodiment formed based on the 1-3 determination step, and FIG. 6 is a schematic view showing the shape of the inner teeth 27a of the first embodiment similarly formed. Is.

The shape of the outer teeth 36a will be described with reference to FIG. Both addendum portion a on both sides up to the tooth tip from d point of the reference pitch circle radius r _e vicinity are formed by segments of the epicycloid trajectory. Further, the tooth root portion b from the point _{e in the} vicinity of the reference pitch circle radius re to the tooth root is formed by the line segment of the adduction cycloid locus on both sides.
The middle part c of the tooth between the points d and e forms a plane composed of straight lines. n(→) indicates a normal vector of the adduction cycloid curve, and e(→) _x indicates a unit vector forming a horizontal plane.

The shape of the inner teeth 27a will be described with reference to FIG. The tooth root portion f from the point _{i in the} vicinity of the reference pitch circle radius r _i to the tooth root is formed by the line segment of the abduction cycloid locus on both sides. Further, the tooth tip portion g from the point j near the reference pitch circle radius r _i to the tooth tip is formed by a line segment of the adduction cycloid locus on both sides.
The tooth middle portion h between the point i and the point j forms a plane formed by a straight line. n(→) indicates a normal vector of the adduction cycloid curve, and e(→) _x indicates a unit vector forming a horizontal plane.

FIG. 7 is a schematic diagram showing the deepest meshing state of the rigid internal gear 27 and the flexible external gear 36 of the first embodiment.

The internal teeth 27a of the rigid internal gear 27 and the external teeth 36a of the flexible external gear 36 are in contact with each other in the entire region from the root portion to the tip portion, and the contact area is large, and the surface pressure can be reduced.

FIG. 8 is a schematic diagram showing a minute dissociation state of the rigid internal gear 27 and the flexible external gear 36 of the first embodiment.

The inner teeth 27a of the rigid inner gear 27 and the outer teeth 36a of the flexible outer gear 36 are in contact with each other around the tooth middle portions h and c which are straight lines, and a certain contact area is secured.

FIG. 9 is a schematic diagram showing the disengagement progressing state of the rigid internal gear 27 and the flexible external gear 36 of the first embodiment.

The internal teeth 27a of the rigid internal gear 27 and the external teeth 36a of the flexible external gear 36 are a tooth tip portion g having a line segment of an adder cycloid locus of the internal teeth 27a of the rigid internal gear 27 and the flexible external gear 36. Of the outer teeth 36a of the outer tooth 36a is in point contact with the tooth tip a having a line segment of the abduction cycloid locus.

FIG. 10 is a diagram showing changes in the effective contact area with respect to the input rotation angle of the flexible external gear 36, the rigid internal gear 27 of Example 1 and the comparative example.

The solid line shows the compound curve tooth profile of Example 1, and the other lines show the comparative example. The large broken line is the locus curve tooth profile calculated from the locus of tooth movement, the small broken line is the straight tooth profile, and the dashed-dotted line is the involute tooth profile.
It can be seen that the linear tooth profile and the involute tooth profile have smaller effective contact areas as compared with the first embodiment, and the upper limit of the allowable load torque is low.
Further, the locus curve tooth profile has a large effective contact area with respect to the input rotation angle and has an excellent allowable load torque as compared with the first embodiment, but has a maximum contact surface at all times, which causes a reduction in efficiency.
From the above, the compound curved tooth profile of the first embodiment can establish a wave gear reducer with high allowable load torque and high efficiency.

The effects of Example 1 are listed below.
(1) The inner teeth 27a and the outer teeth 36a have straight tooth portions in the middle portions h and c of the outer teeth 36a, and the root portion b of the outer teeth 36a and the tip portion g of the inner teeth 27a have inner teeth 36a. A tooth profile having a line segment of the outer cycloid locus and a tooth profile having the line segment of the outer cycloid locus at the tooth tip a of the outer tooth 36a and the root f of the inner tooth 27a is provided. When the outer teeth 36a of the rigid inner gear 27 are inserted to the bottom of the specific inner teeth 27a of the rigid internal gear 27, the tooth tip a of the specific outer tooth 36a and the root f of the specific inner tooth 27a make surface contact. Then, the root portion b of the specific external tooth 36a and the tooth tip portion g of the specific internal tooth 27a are in surface contact, and the tooth center portion c of the specific external tooth 36a and the tooth central portion h of the specific internal tooth 27a are in surface contact. I made contact.
Therefore, in the deepest meshing state of both teeth 27a, 36a, the contact range from the tooth root to the tooth tip is large, the allowable load torque can be increased, and the load torque performance can be improved.

(2) Both the outer teeth 36a and the inner teeth 27a are continuously connected to the adduction cycloid locus and the abduction cycloid locus from the straight tooth portions of the tooth center parts c and h, and the tooth tip a of the specific outer tooth 36a is The contact area of the specific internal tooth 27a decreases as the speed at which the specific external tooth 36a moves away from the root of the specific internal tooth 27a increases.
Therefore, since the relative speed and the contact distance are continuously inversely proportional, it is possible to suppress a decrease in efficiency.

(3) The actuator A of the link mechanism for an internal combustion engine that rotates the second control shaft 11 that changes the attitude of the link mechanism of the internal combustion engine, the electric motor 22 that drives the motor output shaft 48 to rotate, and the motor output shaft 48. Has a wave gear reducer 21 for reducing the rotational speed of the gear and transmitting it to the second control shaft 11, and a housing 20 for covering the wave gear reducer 21. The wave gear reducer 21 has a straight tooth in the center of the teeth. A plurality of outer teeth 36a, which is a tooth profile having an abduction cycloid locus line segment of the outer tooth 36a at the root portion and a tooth tip portion having an abduction cycloid locus line portion. A flexible external gear 36 that transmits a force to the second control shaft 11, a flexible external gear 36 is arranged on the outer periphery of the flexible external gear 36, is fixed to the housing 20, has a straight tooth portion in the center of the tooth, and has a tooth tip portion. Rigid internal gear 27 having an inner tooth 27a having a line segment of the adduction cycloid locus of the outer tooth 36a and having a line segment of the abduction cycloid locus at the tooth root portion and having a larger number of teeth than the outer tooth 36a. And is driven to rotate by the motor output shaft 48, the flexible external gear 36 is bent in the radial direction and partially meshes with the rigid internal gear 27, and the meshing portion is formed by rotating around the rotary shaft. A wave generator 37 that moves in the circumferential direction.
Therefore, in the deepest meshing state of both teeth 27a, 36a, the contact range from the tooth root to the tooth tip is large, the allowable torque can be increased, and the load torque performance can be improved. Further, the contact area between the tooth tip a of the specific outer tooth 36a and the tooth tip g of the specific inner tooth 27a increases as the speed at which the specific outer tooth 36a moves away from the root of the specific inner tooth 27a increases. Since the relative speed and the contact distance are continuously inversely proportional to each other by reducing the decrease in efficiency, it is possible to suppress a decrease in efficiency.
As a result, both load torque performance and efficiency can be improved.

[Other Examples]
Although the embodiment for carrying out the present invention has been described above, the specific configuration of the present invention is not limited to the configuration of the embodiment, and there are design changes and the like within the scope not departing from the gist of the invention. Also included in the present invention.
For example, the wave gear reducer of the present invention is not limited to the actuator of the link mechanism for an internal combustion engine, and a valve timing control device for an internal combustion engine described in JP 2015-1190 A, JP 2011-231700 A, or the like. It is also applicable to a variable steering angle mechanism that can change the turning angle with respect to the steering angle.

A Link mechanism actuator for internal combustion engine
11 Second control axis (control axis)
20 housing
21 Wave gear reducer
22 Electric motor
27 Rigid internal gear
27a internal teeth
36 Flexible external gear
36a External teeth
37 Wave generator
48 Motor output shaft a External tooth tip b External tooth root c External tooth central f f Internal tooth root g Internal tooth tip h Internal tooth central

Claims (5)

A flexible external gear, the tooth center of an external tooth having a tooth surface formed in a plane through a reference pitch circle, the tooth tip of the outer tooth on the tooth tip side of the tooth center, and the tooth center. A flexible external gear having a tooth root portion of the outer tooth on the tooth root side,
A rigid internal gear arranged on the outer periphery of the flexible external gear, passing through the reference pitch circle, and a tooth center portion of an internal tooth having a tooth surface formed in a plane, and a tooth tip side of the tooth center portion. A rigid internal gear having a tooth tip portion of the inner tooth and a tooth root portion of the inner tooth on the tooth root side of the tooth middle portion of the inner tooth,
A wave generator that flexibly moves the flexible external gear in the radial direction and partially meshes with the rigid internal gear, and rotates the meshing portion in the circumferential direction by rotating around the rotation axis,
Equipped with
The root portion of the outer tooth and the tip portion of the inner tooth have a line segment of an adder cycloid locus of the flexible outer gear, and the tip portion of the outer tooth and the root portion of the inner tooth are further included. Has a line segment of an abduction cycloid trajectory,
A wave gear reducer characterized in that The wave gear reducer according to claim 1,
In a state where the specific external teeth of the flexible external gear are inserted at the most tooth bottom side of the specific internal teeth of the rigid internal gear,
Surface contact with the tooth tip of the specific external tooth and the tooth root of the specific internal tooth,
Surface contact with the root portion of the specific external tooth and the tip portion of the specific internal tooth,
Surface contact with the tooth center of the specific external tooth and the tooth center of the specific internal tooth,
A wave gear reducer characterized in that The wave gear reducer according to claim 2,
The contact area between the specific external tooth and the specific internal tooth decreases as the speed at which the specific external tooth moves away from the root of the specific internal tooth increases.
A wave gear reducer characterized in that An actuator of a variable compression ratio device for varying the piston stroke amount of an internal combustion engine,
A control shaft that changes the piston stroke amount of the internal combustion engine by rotating,
An electric motor that rotationally drives the motor output shaft,
A wave gear reducer that reduces the rotation speed of the motor output shaft and transmits it to the control shaft,
Have
The wave gear reducer,
A flexible external gear, the tooth center of the external tooth having a tooth surface formed in a plane through a reference pitch circle, the tooth tip of the outer tooth on the tooth tip side of the tooth center, and the tooth center. A flexible external gear having a tooth root portion of the outer tooth on the tooth root side,
A rigid internal gear arranged on the outer periphery of the flexible external gear, passing through the reference pitch circle, and a tooth center portion of an internal tooth having a tooth surface formed in a plane, and a tooth tip side of the tooth center portion. A rigid internal gear having a tooth tip portion of the inner tooth and a tooth root portion of the inner tooth on the tooth root side of the tooth middle portion of the inner tooth,
A wave generator that flexibly moves the flexible external gear in the radial direction and partially meshes with the rigid internal gear, and rotates the meshing portion in the circumferential direction by rotating around the rotation axis,
Equipped with
The root portion of the outer tooth and the tip portion of the inner tooth are along the line segment of the adduction cycloid locus of the flexible outer gear, and the tip portion of the outer tooth and the root of the inner tooth are further provided. The part is along the line segment of the abduction cycloid locus,
An actuator of a variable compression ratio device for an internal combustion engine, comprising: An actuator of a variable compression ratio device for an internal combustion engine according to claim 4,
In a state where the specific external teeth of the flexible external gear are inserted at the most tooth bottom side of the specific internal teeth of the rigid internal gear,
Surface contact with the tooth tip of the specific external tooth and the tooth root of the specific internal tooth,
Surface contact with the root portion of the specific external tooth and the tip portion of the specific internal tooth,
Surface contact with the tooth center of the specific external tooth and the tooth center of the specific internal tooth,
An actuator of a variable compression ratio device for an internal combustion engine, comprising:

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