JPH0652095B2 - Power transmission device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power transmission device, and more particularly to a power transmission device that transmits power by rolling a rolling element between grooves formed on opposing surfaces of two members. .

[Technical background of the invention and its problems]

Conventionally, as a power transmission device of this type, for example, a speed reducer as shown in FIG. 7 is known (Japanese Patent Laid-Open No. 58-779).
No. 53). That is, in the case 101, an input plate 107 that is eccentrically moved via a bearing 105 by the rotation of an eccentric portion 103a formed on the input shaft 103, and an output disc connected to the output shaft 109.
111 and an intermediate disk 115 which is eccentrically moved via a bearing 113 by the rotation of an eccentric portion 103b which is arranged between the respective circular plates 107, 111 and which is integrally formed with the eccentric portion 103a.

In this speed reducer, the rotation of the input shaft 103 causes the rolling elements 119 to move between the periodic function grooves formed on the opposing surfaces of the fixed disc 117 and the input disc 107 forming the case 101, respectively. By rolling as shown in FIG. 8 which is a sectional view taken along line XX of FIG. 8, the input disc 107 eccentrically (revolves) with respect to the input shaft 103, and rotates and decelerates in the direction opposite to the input shaft 103. To be done. The rotary motion of the input disk 107 is transmitted to the intermediate disk 115 as it is by the crank mechanism via the rolling elements 121.

Between the intermediate disk 115 and the output disk 111, the input disk 10
The deceleration is performed by a method similar to the power transmission performed between 7 and the fixed disc 117, that is, the rolling element 123 rolls in the periodic function groove. As a result, the rotation of the input shaft 103 is reduced in two stages and transmitted to the output shaft 109.

However, this type of speed reducer has the following problems. That is, the engagement between the two grooves and the rolling elements in the speed reducing portion is as shown in FIG. 9, and if the precision of the groove processing is poor or the axial preload is insufficient, the rolling elements 123 ( 119) and the grooves 111a (117a), 115a (107a) contact at the groove ends 111b (117b), 115b (107b), and the tooth surface is deformed or damaged. Therefore, high accuracy, long life, high efficiency,
It becomes impossible to transmit power with a large transmission capacity.

[Object of the Invention]

The present invention has been made in view of such conventional problems, and an object of the present invention is to prevent rolling elements and grooves from contacting each other at groove end portions, and to achieve high accuracy, It is to provide a power transmission device with long life, high efficiency, and large transmission capacity.

[Outline of Invention]

The essence of the present invention is to form the groove cross-section asymmetrically in order to prevent the rolling element and the groove from contacting each other at the groove end.

That is, according to the present invention, the first member and the second member are arranged so as to face each other, and periodic function grooves having different periods are formed on the facing surfaces of these members, and a plurality of rolling elements are provided between these periodic function grooves. And a ball is used as the rolling element in the power transmission device that shifts and transmits the rotational force between the first member and the second member. The groove wall on the side where the ball receives the transmission force contacts the groove wall side of the groove of the second member on which the ball does not contact, and similarly, the groove wall on the side where the ball contacts the second member. Is configured so as to have a groove cross-sectional shape that extends to the groove wall side where the balls of the groove of the first member do not contact.

〔The invention's effect〕

According to the present invention, the side of the periodic function groove which is in contact with the rolling element (rolling side) is made to project to the side of the mating groove which is not in contact with the rolling element (non-rolling side), so that the meshing is slightly different. Even when the condition is not good or the preload is not applied, the contact area between the rolling element and the groove can be made large. Therefore, it is possible to prevent deformation and damage of the groove, and it is possible to realize a power transmission device with high accuracy, long life, high efficiency, and large transmission capacity.

Example of Invention

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing a schematic configuration of a speed reducer as a power transmission device. The case 1 is a cup-shaped case body 3 having an opening in the right direction in the figure, and a fixed circle as a first circular plate attached to the case body 3 to form the mechanism chamber 5 by closing the opening. It is composed of a plate (first member) 7. An output shaft 11 is rotatably provided on the case body 3 via a bearing 9, and an input shaft 15 is rotatably provided on the fixed disc 7 via a bearing 13.

An eccentric portion 15a that is eccentric with respect to the input shaft 15 is formed at the tip of the input shaft 15 on the mechanism chamber 5 side, and the eccentric portion 15a is eccentrically moved (revolves) with respect to the input shaft 15 via a bearing 17. An input disc (second member) 19 as a disc is provided so as to face the fixed disc 7.

On each of the facing surfaces of the fixed disk 7 and the input disk 19, a hypotrochoid gear as an internal gear and an epitrochoid gear as an external gear are formed. Hereinafter, a groove 7a having a hypotrochoid tooth profile) and a groove 19a having an epitrochoid equidistant curve tooth profile (hereinafter referred to as epitrochoid tooth profile) are formed. Then, as shown in FIG. 2 showing the meshing of the gears as viewed from the left and right in FIG. 1, each groove 7a,
A plurality of balls 23 as rolling elements having the function of a pin gear that can roll between these portions are arranged between 19a.

That is, consider two sets of a pin gear that meshes with a hypotrochoid tooth profile and a pin gear that meshes with an epitrochoid tooth profile,
By making the pin gears common to the two sets, an inscribed planetary mechanism having two tooth difference is formed as shown in FIG.

The groove cross-sectional shapes of the hypotrochoid tooth profile and the epitrochoid tooth profile are as shown in FIG. 3 or FIG.
That is, the hypotrochoid tooth groove 7a and the epitrochoid tooth groove 19a are on the rolling side where the rolling elements come into contact and roll, and the hypotrochoid tooth groove 7a is the epitrochoid tooth groove 19a.
a has a portion 7b that projects to the non-rolling side, and the epitrochoid tooth groove 19a has a portion 19b that projects to the non-rolling side of the hypotrochoid tooth groove 7a. Also, the groove 7
The non-rolling sides of a and 19a are removed so as to be flush with the groove bottom portion that contacts the ball 23. It should be noted that FIG. 3 shows a shape that projects linearly in the tangential direction, and FIG. 4 shows a shape that projects in an arc shape in accordance with the curvature of the groove.

In such a mechanism, the ball 23 (pin gear) rolls between the grooves 7a and 19a, so that the input disc 19
Rotates (rotates) in a direction opposite to the rotation direction of the input shaft 15 together with the revolution. If you take this rotation as output,
The first stage deceleration will be performed.

An eccentric portion 15b, which is eccentric by the same amount in the opposite direction to the eccentric portion 15a, is integrally formed on the left side end of the eccentric portion 15a. The eccentric portion 15b is provided with an intermediate disk 27 that moves eccentrically (revolves) and rotates about the input shaft 15 together with the input disk 19 via a bearing 25.

The eccentric amounts of the eccentric parts 15a and 15b are provided on the respective facing surfaces of the input disk 19 and the intermediate disk 27, as shown in FIG. 5, which is an explanatory view of the facing surface viewed from the left in FIG. A plurality of pairs of circular grooves 31 having a radius of and a pair of circular grooves 33 facing each other are formed. A ball 35 is arranged between the pair of circular grooves 31 and 33 as shown in FIG. 6 to form a crank mechanism, and the input disc 19 and the intermediate disc 27 have a rotation ratio of 1: 1. Are joined by. Therefore, the revolution and rotation of the input disc 19 are transmitted to the intermediate disc 27 as they are. At this time,
Since the eccentric portions 15a and 15b are eccentric by the same amount in the opposite directions, the balance of the input disc 19 and the intermediate disc 27 with respect to the revolution is maintained.

On the left side surface of the intermediate disc 27, an output disc 37 is arranged so as to face it. The output disc 37 is mounted on the output shaft 11 which is concentric with the input shaft 15. At the left end of the eccentric portion 15b, a small-diameter portion 15c of the input shaft 15 projects, and the small-diameter portion 15c is supported by the output disc 37 via a bearing 39 so that one end of the input shaft 15 in the case 3 is fixed. It has been supported.

On the respective facing surfaces of the intermediate disk 27 and the output disk 37, the epitrochoidal tooth-shaped grooves 27a and hypotheses similar to the periodic function grooves formed on the facing surfaces of the fixed disk 7 and the input disk 19 are formed. Grooves 37a each having a trochoidal tooth shape are formed, and a second groove is formed between the grooves 27a and 37a.
As shown in the figure, a plurality of balls 41 are arranged as rolling elements that roll between these disks and transmit (decelerate) power between the disks 27 and 37. That is, the ball 41 has a function as a pin gear, and when the ball 41 rolls between the grooves 27a and 37a, the output disc 37 is decelerated and rotates. That is, here again, an inscribed planetary mechanism having two tooth differences as shown in FIG. 2 is formed.

Therefore, the first speed reduction mechanism (inscribed planetary mechanism) 43 formed between the input disk 19 and the fixed disk 7 performs the first speed reduction, and the intermediate disk 27 and the output disk 37 are separated. The second speed reduction mechanism (inscribed planetary mechanism) 45 formed between the two speeds performs the second speed reduction.

Among the disks in the mechanism room 5, the intermediate disk 27 and the output disk 37
Considering the relationship with, since the output disk 37 corresponds to the fixed disk 7 and the intermediate disk 27 corresponds to the input disk 19, the output disk 37 is the first disk and the intermediate disk 27 is the intermediate disk. Disk 27 is second
It means that it is a disk.

Here, the numbers of teeth of the epitrochoidal tooth profile, the hypotrochoidal tooth profile and the pin gear in the first reduction gear mechanism 43 are Z _1e , Z _1h , and Z _1p , respectively, and the number of teeth in the second reduction gear mechanism 45 is Z _2e , respectively. , Z _2h , Z _2p , there is a relationship of Z _1p = Z _1e + 1 = Z _1h −1 Z _2p = Z _2e + 1 = Z _2h −1, and the first reduction gear ratio i ₁ and the second reduction gear The ratio i ₂ is as follows.

_{i 1 = - (Z 1h -Z} 1e) / Z 1e = -2 / Z 1e ... i 2 = 1- (Z 1h · Z 2e / Z 1e · Z 2h) ... where the load issue rotation of the input side It indicates that the direction and the rotation direction on the output side are opposite. Further, when Z _1p = Z _2p , output rotation cannot be obtained. In this example, Z _1e =
10, Z _1p = 11, Z _1h = 12, Z _2e = 11, Z _2p = 1
2, Z _2h = 13, and by substituting these numerical values into the above formula, the final reduction ratio i ₂ becomes − (1/65).

Reference numerals 47, 49, and 51 in FIG. 2 are a hypotrochoid tooth pitch circle, a pin gear pitch circle, and an epitrochoid tooth pitch circle, respectively.

Next, the operation of the above configuration will be described.

In response to the rotation of the input shaft 15, the input disc 19 makes an eccentric motion (revolution), and the first reduction mechanism 43 causes the input shaft 1 to rotate.
Deceleration rotation (rotational motion) is performed in the direction opposite to the rotation direction of 5.
The revolving and rotating movements are transmitted to the intermediate disc 27 through the crank mechanism having the balls 35 as they are.

The rotational movement of the intermediate disc 27 is further decelerated by the second reduction mechanism 45 and reaches the output shaft 11 via the output disc 37.

As shown in FIG. 3 and FIG. 4, the cross section of the tooth profile groove forming the reduction mechanisms 43 and 45 has a hypotrochoid tooth profile groove 7a (37a) whose rolling side is the epitrochoid tooth profile groove 19a (27a) on the other side. ) Part 7 protruding to the non-rolling side
b (37b) and conversely epitrochoid tooth profile 19a
(27a) is a portion 19b whose rolling side projects to the non-rolling side of the opponent hypotrochoid tooth profile 7a (37a).
It has (27b). For this reason, even when there is no preload in the axial direction or when the meshing is a little poor due to machining accuracy, etc.
The rolling element and the two tooth-shaped grooves do not come into contact with each other at the groove end, and always maintain a certain contact area. Therefore, the deformation of the tooth profile and the damage to the tooth surface due to the contact pressure are extremely reduced.

As described above, according to this embodiment, it is possible to prevent the ball and the groove from coming into contact with each other at the groove end. For this reason, deformation of the tooth profile forming the groove and damage to the tooth surface are extremely reduced, and a speed reduction mechanism with high accuracy, long life, high efficiency, and large transmission capacity can be realized.

The present invention is not limited to the above embodiment. For example, the speed reducing mechanism is not limited to two stages,
Of course, the number of steps may be one, three or more. Further, conditions such as the period, groove width, and depth of the periodic function groove of the first and second members may be appropriately determined according to the specifications. In addition, various modifications can be made without departing from the scope of the present invention.

[Brief description of drawings]

1 to 6 are each for explaining a schematic configuration of a speed reducer according to an embodiment of the invention. FIG. 1 is a sectional view showing the overall configuration, and FIG. 2 is a schematic diagram showing a meshing state of gears. FIGS. 3, 3 and 4 are sectional views showing the groove shape, FIGS. 5 and 6 are schematic views showing a crank mechanism in the speed reducer, and FIGS. 7 to 9 are explanatory views of a conventional speed reducer, respectively. FIG. 7 is a cross-sectional view showing the entire structure, FIG. 8 is a schematic view showing a meshed state of gears, and FIG. 9 is a cross-sectional view showing a groove shape. 1 ... Case, 7 ... Fixed disk (first member), 19 ...
... Input disk (second member), 31, 33 ... circumferential groove, 2
3, 35, 41 ... Ball (rolling element), 27 ... Intermediate disk, 37 ... Output disk, 7a, 37a ... Hypotrochoid tooth groove (periodic function groove), 19a, 27a ... Epitrochoid Tooth-shaped groove (periodic function groove).

Claims (3)

[Claims] 1. A first member and a second member are arranged to face each other,
Periodic function grooves having different periods are formed on the facing surfaces of these members, and a plurality of rolling elements are arranged between these periodic function grooves to rotate between the first member and the second member. In a power transmission device that shifts and transmits a force, balls are used as the rolling elements, and a groove wall on a side of the groove of the first member that contacts the ball is in contact with the ball of the groove of the second member. The groove cross-sectional shape is such that it projects to the groove wall side, and similarly, the groove wall on the side of the second member that contacts the ball extends to the groove wall side of the groove of the first member that does not contact the ball. Power transmission device characterized by. 2. A rotating shaft is coaxially provided on each of the first and second members via bearings, and these rotating shafts are fixed in a state of being eccentric to each other. The power transmission device according to claim 1. 3. The periodic function groove of each of the first and second members is characterized in that the groove wall side where the rolling elements do not contact is formed at the same height as the groove bottom. The power transmission device as set forth in claim 1.