JP7566661B2 - Differential reducer - Google Patents

Description

The present invention relates to a differential reducer that can increase rigidity.

Patent Document 1 discloses a gear transmission that includes an internal gear, an input shaft with two eccentric parts whose eccentric directions are offset by 180 degrees from each other, external gears that are arranged on each eccentric part and internally engage with the internal gear, output bodies that are arranged on the outside of each external gear in the axial direction, and cross-shaped conversion bodies that are arranged between the output bodies and the external gear.

Each output body has a stopper with a guide, which slides along the lateral guideway of the conversion body, giving it a degree of freedom in the lateral direction relative to the rotation axis of the output body. Also, each external gear has a stopper with a guide, which slides along the vertical guideway of the conversion body, giving it a degree of freedom in the vertical direction relative to the rotation axis of the output body. In other words, the conversion body functions in the same way as a universal joint, converting the eccentric rotational motion of the external gear into rotational motion centered on the axis of the output body.

Special Publication No. 9-508957

In the gear transmission of Patent Document 1, the conversion body is a thin plate, which has a large effect on the rigidity of the gear transmission. In other words, when torque is applied between the input and output of the gear transmission, the conversion body distorts, lowering the rigidity of the entire gear transmission. The rigidity can be increased by increasing the thickness of the conversion body, but this will increase the overall thickness of the gear transmission and the weight.

The present invention has been made to solve the above-mentioned problems, and aims to provide a differential reducer that can reduce distortion of the converter and increase rigidity with a simple configuration.

In order to achieve this object, the differential reduction gear described in claim 1 comprises an internal gear, an input shaft arranged coaxially with the internal gear and penetrating through the internal gear and having an eccentric portion eccentric with respect to a central axis, an external gear attached to the eccentric portion and inscribed in mesh with the internal gear and having a first sliding portion, a conversion member arranged adjacent to the external gear and having a second sliding portion capable of sliding with the first sliding portion via a first sliding member, and converting planetary motion of the external gear into rotational motion coaxial with the central axis, a plate member arranged outside the conversion member and having a fourth sliding portion capable of sliding with a third sliding portion provided on the conversion member via the second sliding member, and a reinforcing member arranged in a position overlapping at least one of the second sliding portion or the third sliding portion when viewed from the central axis direction and fixed to a side of the conversion member.
A differential reduction gear according to a second aspect of the present invention is the differential reduction gear according to the first aspect, further characterized in that the reinforcing member is in the shape of a hollow disk.
Furthermore, the differential reduction gear according to claim 3 is the differential reduction gear according to claim 1 or 2, further characterized in that the reinforcing member is made of a material different from that of the conversion member.
The differential reduction gear according to claim 4 is the differential reduction gear according to any one of claims 1 to 3, further characterized in that the reinforcing member and the conversion member are fastened by a countersunk screw.

According to the differential reducer of claim 1, the reinforcing member fixed to the side surface of the conversion member can reduce distortion of the conversion member. In particular, by increasing the strength of the second sliding portion or the third sliding portion, the rigidity of the differential reducer can be effectively increased.
According to the differential reduction gear of claim 2, since the reinforcing member is disk-shaped, it is difficult for the reinforcing member to be distorted in the circumferential direction. This makes it possible to further increase the rigidity of the differential reduction gear. Also, the reinforcing member is easy to manufacture.
According to the differential reduction gear of claim 3, since the material of the reinforcing member is different from that of the conversion member, it is possible to use an inexpensive material for the reinforcing member. For example, by using a material that can be mass-produced inexpensively by metal press processing or the like, the processing cost of the reinforcing member can be reduced.
According to the differential reducer of claim 4, the reinforcing member and the conversion member are fastened by flat head screws, so that the tapered head of the flat head screw prevents the reinforcing member and the conversion member from shifting in the circumferential direction, thereby further increasing the rigidity of the differential reducer.

1 is a central vertical sectional view of a differential reduction gear according to an embodiment of the present invention. FIG. FIG. 2 is a front view of the differential reduction gear with a bracket and a reinforcing plate removed. FIG. 2 is a front view of the differential reduction gear with the bracket removed.

The following describes an embodiment of the present invention with reference to the drawings. Fig. 1 is a central longitudinal cross-sectional view of a differential reduction gear 1. Fig. 2 is an exploded perspective view of the differential reduction gear 1. The differential reduction gear 1 of this embodiment is used, for example, in the joints of an industrial robot.

The differential reduction gear 1 is an eccentric oscillation type reduction gear in which the external gear 2 rotates eccentrically while meshing with the internal gear 3. The differential reduction gear 1 includes the external gear 2, the internal gear 3, a case 4, and an input shaft 5.

The case 4 is composed of a cylindrical main case 6, a backing plate 7 that is arranged on the input side of the main case 6 (the right side in FIG. 1) and has a circular shape that is approximately the same as that of the main case 6, and a bracket 8 that is arranged on the opposite side of the backing plate 7 and has a circular shape that is approximately the same as that of the main case 6 and the backing plate 7. The main case 6, the backing plate 7, and the bracket 8 are fastened together by a number of bolts 9, 9... that penetrate the backing plate 7 from the bracket 8 side and screw into the main case 6. The main case 6 has a raceway surface for a cross roller 11 formed on its inner circumferential surface. In other words, the main case 6 also serves as the outer ring of the cross roller bearing 12. In addition, a number of through holes 13 are formed in the main case 6, the backing plate 7, and the bracket 8 at positions that avoid the bolts 9, 9....

A cylindrical internal gear 3 is arranged radially inside the main case 6. The internal gear 3 has a raceway surface of a cross roller 11 formed on its outer circumferential surface, and is rotatably supported by the main case 6 via the cross roller 11. The cross roller 11 is arranged radially outside the internal gear 3 in a position overlapping with the internal teeth when viewed from a direction perpendicular to the central axis C0. In other words, the internal gear 3 also serves as the inner ring of the cross roller bearing 12. In the internal gear 3, an output section 15 having multiple bolt holes 14 is formed on the end face on the output side (left side of FIG. 1). Either the case 4 (through hole 13) or the output section 15 (bolt hole 14) is the fixed side, and the other is the output side and is connected to a mating device.

The inner circumferential surface of the internal gear 3 does not have internal teeth on the output section 15 side, and a disk-shaped bearing housing 16 is fixed by press fitting. An annular groove 17 is formed around the entire circumference of the input side end face of the internal gear 3, at a position facing the reaction plate 30 described later, and centered on the central axis C0.

A hollow cylindrical input shaft 5 is arranged inside the external gear 2. The input shaft 5 is cylindrical with a circular hollow portion 18 centered on the central axis C0 to allow wiring, a drive shaft, etc. to pass through. The central axis C0 of the input shaft 5 is coaxial with the axis of the internal gear 3.

Support parts 21 for arranging the first ball bearing 20a and the second ball bearing 20b are formed on both ends of the input shaft 5. The input shaft 5 is rotatably supported on the inner peripheral surface of the bracket 8 via the first ball bearing 20a, and is rotatably supported on the inner peripheral surface of the bearing housing 16 via the second ball bearing 20b. Between the support parts 21, 21 on the input shaft 5, an eccentric part 22 is formed, which has a cylindrical surface with an outer diameter larger than that of the support part 21 and is centered on an eccentric axis C1 offset from the central axis C0 by an eccentricity amount δ1.

A single external gear 2 is rotatably supported on the radial outside of the eccentric portion 22 via multiple needle rollers 23 arranged around the entire circumference in the circumferential direction and with a circular cross section. All of the needle rollers 23 together form a needle bearing that supports the external gear 2. In other words, the eccentric portion 22 also serves as a raceway surface serving as the inner ring of the needle bearing. Each needle roller 23 is arranged facing in the same direction as the central axis C0, and the axial length of each needle roller 23 is approximately the same as the axial width of the eccentric portion 22. The axial movement of each needle roller 23 is restricted by the side surfaces of the first ball bearing 20a and the second ball bearing 20b.

Figure 3 is a front view of the differential reduction gear 1 as viewed from the input side of the central axis C0, showing the state in which the bracket 8 and the reinforcing plate 40 described later have been removed from the differential reduction gear 1. Figure 4 is a front view of the differential reduction gear 1 as viewed from the input side of the central axis C0, showing the state in which the bracket 8 has been removed from the differential reduction gear 1. Figure 4 shows the fixed state of the reinforcing plate 40.

The input shaft 5 has four bolt holes 24 formed on its input end face. The bolt holes 24 are formed at equal intervals around a circumference, and are shaped to allow connection to a drive shaft (not shown). The input shaft 5 also has eight circular through holes 25 formed from the input end face to the output side. Each through hole 25 is circular and is formed on the eccentric axis C1 side (upper side of FIG. 4) relative to the central axis C0, in a position that avoids the bolt holes 24. The through holes 25 are not formed on the opposite side of the eccentric axis C1 relative to the central axis C0 (lower side of FIG. 4). The through holes 25 function as hollowed-out portions, and can improve the imbalance of rotation caused by the eccentricity of the input shaft 5 and the external gear 2 when the differential reduction gear 1 is driven.

The external gear 2 has a number of teeth slightly less than that of the internal gear 3, and is inscribed in the internal gear 3 at an eccentric position. On the input side of the external gear 2, two angular abutment blocks 26a, 26b are formed integrally with the external gear 2. Each of the abutment blocks 26a, 26b has a first sliding portion 27a, 27b formed on each side of both sides in the circumferential direction of the external gear 2. Each of the abutment blocks 26a, 26b is formed so that the first sliding portions 27a, 27b are parallel to each other. On the side (input side) of the external gear 2 facing the reaction plate 30 described later, multiple circular recesses 28 are formed at positions that avoid the abutment blocks 26a, 26b. Most of the multiple recesses 28 are formed at positions that overlap with the reaction plate 30 when viewed from the direction of the central axis C0. In addition, the recesses 28 are filled with a lubricant.

A thin disk-shaped reaction plate 30 is disposed on the radial inside of the contact plate 7. Two notches 33a, 33b are formed on the inner circumferential side of the reaction plate 30 at positions 180 degrees symmetrical to each other, and two notches 33c, 33d are formed on the outer circumferential side at positions 180 degrees symmetrical to each other. One pair of notches 33a, 33b has second sliding parts 34a, 34b parallel to both side surfaces in the circumferential direction. The other pair of notches 33c, 33d has third sliding parts 34c, 34d parallel to both side surfaces in the circumferential direction. One pair of notches 33a, 33b and the other pair of notches 33c, 33d are formed so that the second sliding parts 34a, 34b and the third sliding parts 34c, 34d are perpendicular to each other. Between the first sliding parts 27a, 27b and the second sliding parts 34a, 34b, two first needle rollers 35a with a circular cross section are arranged, and one pair of notches 33a, 33b can slide with the first sliding parts 27a, 27b of the contact blocks 26a, 26b via the first needle rollers 35a. The reaction plate 30 can slide in the direction of the second sliding parts 34a, 34b (horizontal direction in FIG. 3) relative to the external gear 2 by the first needle rollers 35a. In addition, the external gear 2 and the reaction plate 30 are designed so that their sides slide against each other.

Twelve screw holes 36 are formed on the side of the reaction plate 30. Some of the screw holes 36 are formed in positions that sandwich the notches 33a, 33b, 33c, and 33d from both sides. In other words, the screw holes 36 are formed near the second sliding parts 34a and 34b and the third sliding parts 34c and 34d.

The contact plate 7 is annular, and the inner peripheral surface is formed with protrusions 38a, 38b having fourth sliding parts 37a, 37b that face the third sliding parts 34c, 34d in parallel and protrude inward. Two second needle rollers 35b having the same shape as the first needle rollers 35a are disposed between the third sliding parts 34c, 34d and the fourth sliding parts 37a, 37b. The reaction plate 30 can slide relative to the contact plate 7 in the direction of the third sliding parts 34c, 34d (vertical direction in FIG. 3) via the second needle rollers 35b.

The groove 17 formed on the side of the internal gear 3 is located at a position where at least a portion of it overlaps with the reaction plate 30, the first needle roller 35a, and the second needle roller 35b when viewed from the direction of the central axis C0. The groove 17 is filled with lubricant, and is structured to facilitate the supply of lubricant to the reaction plate 30, the first needle roller 35a, and the second needle roller 35b.

A reinforcing plate 40, which has a thin disk shape and is substantially the same as the reaction plate 30, is fixed to the side of the reaction plate 30 opposite the external gear 2. The reinforcing plate 40 has 12 through holes at positions corresponding to the screw holes 36 formed in the reaction plate 30. The reinforcing plate 40 is integrally connected to the reaction plate 30 by flat head screws 41 fastened to the screw holes 36 through the respective through holes. The through holes are tapered to accommodate the heads of the flat head screws 41, thereby suppressing the amount of protrusion of the heads of the flat head screws 41 from the end face of the reinforcing plate 40. The reaction plate 30 is arranged so as to overlap the second sliding parts 34a, 34b (notches 33a, 33b) and the third sliding parts 34c, 34d (notches 33c, 33d) when viewed from the direction of the central axis C0.

In this embodiment, the reaction plate 30 is made of, for example, carbon steel (S-C material), chrome molybdenum steel (SCM material), nickel chrome molybdenum steel (SNCM material), high carbon chrome bearing steel (SUJ material), etc., and is adjusted to have high strength by heat treatment. On the other hand, the reinforcing plate 40 is made of, for example, cold rolled steel plate (SPC material), stainless steel plate (SUS material), etc., and is formed by metal press processing. Also, if a material with a higher Young's modulus is used for the reinforcing plate 40, it is possible to produce a model of a differential reduction gear with higher rigidity.

An oil seal 50 is disposed on the output side of the cross roller bearing 12 between the main case 6 and the internal gear 3. A groove 51 is formed around the entire circumference on the output side end face of the contact plate 7, radially inward from the through hole 13, and an O-ring 52 is disposed in the groove 51. A groove 53 is formed around the entire circumference on the output side end face of the bracket 8, radially inward from the through hole 13, and an O-ring 54 is disposed in the groove 53.

In the differential reducer 1 configured as above, the input shaft 5 rotates due to the power of a driving source (not shown), causing the eccentric portion 22 to move eccentrically, and the external gear 2 to move eccentrically and rotate while inscribed in the internal gear 3. For this reason, each of the contact blocks 26a, 26b also moves eccentrically and rotates, but each of the contact blocks 26a, 26b is arranged to slide in the direction of the second sliding portions 34a, 34b (horizontal direction) relative to the reaction plate 30, and the reaction plate 30 is arranged to slide in the direction of the third sliding portions 34c, 34d (vertical direction) relative to the contact plate 7. As a result, the power is transmitted while each sliding portion slides, and only the rotation component of the external gear 2 is taken out via the reaction plate 30, and the internal gear 3 rotates relative to the case 4. In other words, the reaction plate 30 functions similarly to a so-called universal joint, which converts the eccentric rotational motion of the external gear 2 into rotational motion centered on the central axis C0. The contact plate 7 also functions as a carrier that extracts the rotational motion of the external gear 2 relative to the internal gear 3 from the planetary motion of the external gear 2. At this time, the lubricant filled in the differential reduction gear 1 is sealed by the oil seal 50, O-ring 52, and O-ring 54.

In this way, according to the differential reduction gear 1 of the above embodiment, the reinforcing plate 40 fixed to the side of the reaction plate 30 can reduce the distortion of the reaction plate 30. In other words, when torque is applied between the input and output of the differential reduction gear 1, the notches 33a, 33b, 33c, and 33d of the reaction plate 30 are prevented from opening, thereby increasing the rigidity of the differential reduction gear 1.

In addition, because the reinforcing plate 40 has a disk shape, it is less likely to distort in the circumferential direction. This makes it possible to further increase the rigidity of the differential reduction gear 1. In addition, the reinforcing plate 40 is easy to manufacture and can be produced at low cost.

The material of the reinforcing plate 40 is different from the material of the reaction plate 30, and is a steel plate. Therefore, the reinforcing plate 40 can be mass-produced inexpensively by metal press processing, etc.

The reinforcing plate 40 and the reaction plate 30 are fastened together by flat head screws 41. The heads of the flat head screws 41 are tapered, so the reinforcing plate 40 and the reaction plate 30 do not shift in the circumferential direction, and the rigidity of the differential reducer 1 can be further increased.

Although the present embodiment has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. Below, examples of modifications that can be made to the above embodiment are described.

For example, in this embodiment, the input shaft 5 is hollow and cylindrical with a circular hollow portion 16 centered on the central axis C0, but the input shaft does not have to be hollow. In addition, in this embodiment, the first needle roller 35a is arranged between the first sliding portions 26a, 26b and the second sliding portions 27a, 27b, and the second needle roller 35b is arranged between the third sliding portions 34c, 34d and the fourth sliding portions 37a, 37b, but a sliding bearing may be arranged instead of the needle roller. In addition, in this embodiment, the reinforcing plate 40 is a single disk, but multiple plates may be prepared and fixed so as to cover the cutouts 33a, 33b, 33c, and 33d separately.

[Correspondence of configurations between the present invention and the embodiments]
The contact plate 7 of this embodiment is an example of a plate member of the present invention. The reaction plate 30 of this embodiment is an example of a conversion member of the present invention. The first needle roller 35a of this embodiment is an example of a first sliding member of the present invention. The second needle roller 35b of this embodiment is an example of a second sliding member of the present invention. The reinforcing plate 40 of this embodiment is an example of a reinforcing member of the present invention.

REFERENCE SIGNS LIST 1 differential reducer 2 external gear 3 internal gear 4 case 5 input shaft 7 contact plate 8 bracket 12 cross roller bearing 15 output portion 17 groove 22 eccentric portion 26a, 26b contact block 27a, 27b first sliding portion 28 recess 30 reaction plate 33a, 33b, 33c, 33d notch 34a, 34b second sliding portion 34c, 34d third sliding portion 35a first needle roller 35b second needle roller 36 screw hole 37a, 37b fourth sliding portion 40 reinforcing plate 41 countersunk screw C0 central axis C1 eccentric axis

Claims (4)

An internal gear;
an input shaft arranged coaxially with the internal gear and penetrating into the internal gear, the input shaft having an eccentric portion that is eccentric with respect to a central axis;
an external gear that is attached to the eccentric portion, inscribed in and meshed with the internal gear, and has a first sliding portion;
a conversion member that is disposed adjacent to the external gear, has a second sliding portion that is slidable with the first sliding portion via a first sliding member, and converts a planetary motion of the external gear into a rotational motion coaxial with the central axis;
a plate member having a fourth sliding portion disposed outside the conversion member and slidable with a third sliding portion provided on the conversion member via a second sliding member;
a reinforcing member that is arranged at a position overlapping with at least one of the second sliding portion or the third sliding portion when viewed from the central axis direction and is fixed to a side surface of the conversion member. 2. The differential reduction gear according to claim 1, wherein the reinforcing member has a hollow disk shape. 3. The differential reduction gear according to claim 1, wherein the reinforcing member is made of a different material from the conversion member. 4. The differential reduction gear according to claim 1, wherein the reinforcing member and the conversion member are fastened to each other by a countersunk head screw.

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