PLANETARY GEAR DEVICE SERIES

Abstract

In a planetary gear device series composed of eight kinds of planetary gear devices with gear reduction ratios of 3 to 10, the planetary gear device of each gear reduction ratio uses an internal gear with 108 teeth or a slightly different number of teeth, and the module is common among the planetary gear devices of all gear reduction ratios. The combinations of the sun gear teeth number Za and the internal gear teeth number Zc in the planetary gear device of each reduction ratio are given in Table 1 of this application.

Claims

1. A planetary gear device series including a plurality of types of planetary gear devices having differing gear ratios, the planetary gear device series comprising: eight types of planetary gear devices having gear reduction ratios of 3-10 as the planetary gear devices; wherein a normal module is the same among the planetary gear devices; and in the planetary gear devices of each gear reduction ratio, a number of teeth Za of a sun gear and a number of teeth Zc of an internal gear are set to values either shown in table 1 or integral multiples thereof in a uniform manner. TABLE-US-00003 TABLE 1 Gear reduction ratio R 3 4 5 6 7 8 9 10 Number Za of 54 36 27 21 18 15 13 12 teeth of sun gear Number Zc of 108 108 108 105 108 105 104 108 teeth of internal gear

2. A planetary gear device series according to claim 1, wherein, in the planetary gear devices of each gear reduction ratio, the number of teeth Za of the sun gear, the number of teeth Zb of the planet gears, the number of teeth Zc of the internal gear, and intercentral distance where the normal module is 1.0 mm are set to values shown in table 2. TABLE-US-00004 TABLE 2 Intercentral distance Between sun and Normal Number of teeth planet gears; Gear module Sun Planet Internal between planet and reduction (mn) gear gear gear internal gears ratio R mm Za Zb Zc mm 3 1.0 54 27 108 41.2 4 1.0 36 36 108 36.8 5 1.0 27 40 108 34.4 6 1.0 21 42 105 32.3 7 1.0 18 45 108 32.3 8 1.0 15 45 105 30.8 9 1.0 13 45 104 30.1 10 1.0 12 48 108 30.8

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a structural diagram and a schematic diagram of a planetary gear device to which the present invention can be applied.

MODE FOR CARRYING OUT THE INVENTION

[0019] Embodiments of a planetary gear device series having differing gear reduction ratios to which the present invention is applied are described below with reference to the drawings.

[0020] FIG. 1(a) is a structural diagram of a planetary gear device constituting part of a planetary gear device series according to the present embodiment, and FIG. 1(b) is a schematic diagram of the same. The planetary gear device 1 has a sun gear A, an internal gear C disposed concentrically around the sun gear A, planet gears B that mesh with the sun gear A and the internal gear C, and a planet carrier D provided with planet shafts for rotatably supporting the planet gears B. In the present example, three planet gears B are disposed at equiangular intervals. Additionally, spur gears or helical gears are used as the gears A, B, C.

[0021] The planetary gear device 1 is a planetary-type gear reducer, where the sun gear A is an input shaft, the internal gear C is fixed, and the planet carrier D is an output shaft. As is well known, the gear reduction ratio R is represented by the following formula, where Za is the number of teeth of the sun gear A, Zb is the number of teeth of the planet gears B, and Zc is the number of teeth of the internal gear C.

R=(Zc/Za)+1

[0022] A planetary gear device series having differing gear reduction ratios is constructed from eight types of planetary gear devices having gear reduction ratios of 3-10, these eight types of planetary gear devices being planetary gear devices 1 configured as described above. Planetary gear devices having other gear reduction ratios can also be included.

[0023] In the series constructed from eight types of planetary gear devices 1 having gear reduction ratios of 3-10, the inventors focused on using an internal gear having 108 teeth as the internal gear C to the extent possible, and employing a configuration in which all of the modules (normal modules) of the gears in the planetary gear devices 1 were the same. The numbers of teeth of the gears of the planetary gear devices 1 of each gear reduction ratio were designed on this basis. A planetary gear device series in which the number of teeth, etc., of the planetary gear devices of each gear reduction ratio were set as in table 2 was thereby obtained. Table 2 shows a scenario in which helical gears having a helix angle of 10 are used as the gears, the normal module is 1.0 mm, equiangular-disposition design of three planet gears B is employed, and the pressure angle of the teeth is 20.

TABLE-US-00002 TABLE 2 Intercentral distance Between sun and Normal Number of teeth planet gears; Gear module Sun Planet Internal between planet and reduction (mn) gear gear gear internal gears ratio R mm Za Zb Zc mm 3 1.0 54 27 108 41.2 4 1.0 36 36 108 36.8 5 1.0 27 40 108 34.4 6 1.0 21 42 105 32.3 7 1.0 18 45 108 32.3 8 1.0 15 45 105 30.8 9 1.0 13 45 104 30.1 10 1.0 12 48 108 30.8

[0024] As shall be apparent from table 2, the modules of the gears constituting part of the planetary gear devices of each gear reduction ratio are the same. Therefore, the types of tools for use in gear cutting processes can be reduced, facilitating tool management, and the tool cost can also be reduced.

[0025] As the internal gear C, a common internal gear having 108 teeth is used in planetary gear devices having gear reduction ratios R of 3, 4, 5, 7, and 10, a common internal gear having 105 teeth is used in planetary gear devices having gear reduction ratios R of 6 and 8, and an internal gear having 104 teeth is used in an planetary gear device having a gear reduction ratio R of 9. Accordingly, just three types of internal gear may be prepared for the eight types of planetary gear devices. Because the difference in the numbers of teeth of the internal gears C is very small, variation in the outer diameters of the devices among the planetary gear devices included in the series can also be minimized.

[0026] As pertains to the distance between centers of the constituent gears in the planetary gear devices of each gear reduction ratio, the planetary gear devices having gear reduction ratios of 6 and 7 have intercentral distances of 32.3 mm, and the planetary gear devices having gear reduction ratios of 8 and 10 have intercentral distances of 30.8 mm. Among the planetary gear devices having the same intercentral distances, it is possible to use the same planet carriers provided with planet shafts for supporting the planet gears.

[0027] Furthermore, the planet gears among the planetary gear devices having gear reduction ratios of 7, 8, and 9 can be the same.

[0028] As described above, setting the series configured from the eight types of planetary gear devices having gear reduction ratios of 3-10 such that the gears are as shown in table 2 makes it possible to use the same gear cutting tools among the planetary gear devices of each gear reduction ratio. It is also possible to use the same internal gears, planet carriers, and planet gears among the planetary gear devices for some of the gear reduction ratios. Accordingly, the types of tools and the overall cost of tool management and stock management can be reduced. The types of gears for constituting the series and the manufacturing cost can also be reduced.

Other Embodiments

[0029] It is possible to similarly construct a series of eight types of planetary gear devices having gear reduction ratios of 3-10 such that the numbers of teeth of the gears constituting the planetary gear devices of each gear reduction ratio shown in table 2 are modified, in a uniform manner, to integral multiples thereof. Additionally, employing a dislocated tooth profile makes it possible to increase or decrease the number of teeth of the planet gears by 1. The intercentral distances also increase or decrease from the values shown in table 2 in accordance with this modification.

[0030] Cases where numbers of teeth that are modified in a uniform manner to integral multiples of the numbers of teeth shown in table 2 are used, and cases where planet gears in which the number of teeth shown in table 2 is increased or decreased through use of a dislocated tooth profile are used, are also included in the scope of the present invention. In these cases as well, the same operation and effect is achieved as in the case of an planetary gear device series configured on the basis of the designs shown in table 2.