Patent Description:
A prior art planetary gear based reducer is structured such that components, such as a sun gear, a carrier frame, planetary gears, and an output member, are sequentially mounted to an input axle. As shown in <FIG>, the planetary gear based reduction mechanism is made up of a planetary gear carrier frame <NUM>, a sun gear <NUM>, a plurality of planetary gears <NUM>, and an internally toothed ring <NUM>, and a housing <NUM>, wherein the internally toothed ring <NUM> is combined with the housing <NUM>, while the planetary gear carrier frame <NUM>, the sun gear <NUM>, and the planetary gears <NUM> are received in an interior of the combination of the internally toothed ring <NUM> and the housing <NUM>. The sun gear <NUM> includes a transmission axle <NUM>. Each of the planetary gears <NUM> is in meshing engagement with an outer circumference of the sun gear <NUM> and an inner circumference of the internally toothed ring <NUM>. The planetary gears <NUM> are mounted on the planetary gear carrier frame <NUM>.

Such a known reduction structure has drawbacks in respect of complicated assembly, insufficient accuracy, and deviation of concentricity. To overcome the inconvenience of the prior art in respect of servicing and inventory management that result from complicated assembling and a large number of processes involved, and also for handling deficiency of concentricity after being assembled, the machining precision of each component must be heightened and as such, the difficulty of machining and assembling is also increased, leading to an increase of overall cost of fabrication. On the other hand, if the machining precision is lowered, situations such as unsecured assembly and poor gear engagement may incur, leading to issues of noise and poor transmission efficiency for operation thereof.

Prior art patent documents are known. For example, <CIT> discloses a driving mechanism that comprises an input sun gear meshing with plant gears; and an output shaft of a motor detachably inserted into said input sun gear to enable said input sun gear to be radially movable to a very small degree, whereby said planet gears are allowed to effect a very small eccentric revolutional motion when the torque of said output shaft is transmitted to said input sun gear. Further, Japan patent document <CIT> discloses a planetary gear system including a sun gear and planetary gears mounted to a carrier case to receive the sun gear to axially inserted between the planetary gears, in which the teeth of the sun gear are chamfered to provide a sufficient clearance with respect to the planetary gears for easy insertion between the planetary gears.

The primary objective of the present invention is to make a majority of components modularized, in order to ease assembling, servicing, and inventory management of a reduction mechanism.

A second objective of the present invention is to enhance the concentricity of a reduction mechanism after being assembled, and to reduce the difficulty of machining and assembling, to thereby further lower down overall cost of fabrication.

A further objective of the present invention is to ensure high concentricity after assembly for making the entire assembled structure of a reduction mechanism more stable and more secured and enhancing the degree of meshing engagement, so as to reduce vibration and noise in operation thereof, to thereby extend the service life thereof and also to improve the transmission efficiency.

To achieve such objective, the present invention provides a coaxial gear set reduction mechanism, which comprises: a housing; a transmission axle, which is rotatably mounted in the housing; an internally toothed ring track, which is fixed to the housing; a coaxial gear set, which comprises a sun gear, a planetary gear set, and an output member, wherein the sun gear is selectively mountable to and connected to the transmission axle to rotate together therewith; the planetary gear set is arranged, in a rotatable manner, between two ends of the sun gear, and the planetary gear set is simultaneously in meshing engagement with the sun gear and the internally toothed ring track; and the output member is arranged at one side of the planetary gear set that is opposite to the internally toothed ring track, and the output member is driven by the planetary gear set, wherein one end of the transmission axle is formed with a mounting section and a coupling section, and the sun gear of the coaxial gear set is formed, in a center thereof, with a coupling hole that is fit over the mounting section, a coupling block being inserted into and disposed in the coupling hole to engage with the coupling section of the transmission axle, a fastening member penetrating through and pressing on the coupling block and fastened to the transmission axle, wherein the planetary gear set of the coaxial gear set comprises a first carrier frame and a second carrier frame that are opposite to each other and are respectively and rotatably arranged at two ends of the sun gear, a plurality of planetary gears being rotatably arranged between the first and second carrier frames and around an outer circumference of the sun gear, each of the planetary gears comprising a first toothed portion synchronously meshing with the sun gear and the internally toothed ring track, each of the planetary gears further comprising a second toothed portion meshing with the output member, the output member being rotatably mounted on the second carrier frame of the planetary gear set.

A structure of the present invention, as shown in <FIG> and <FIG>, is made up of a housing <NUM>, a transmission axle <NUM> arranged at a center of the housing <NUM>, an internally toothed ring track <NUM> arranged on an inner circumference of the housing <NUM>, and a coaxial gear set <NUM> arranged between the transmission axle <NUM> and the internally toothed ring track <NUM>.

For a detailed structure of a preferred embodiment according to the present invention, reference being had to <FIG> and <FIG>, the housing <NUM> includes a first mounting compartment <NUM> and a second mounting compartment <NUM>. The first mounting compartment <NUM> is provided for mounting the transmission axle <NUM> and the coaxial gear set <NUM> that is arranged on the transmission axle <NUM>, while the second mounting compartment <NUM> is provided for disposition of a driven member (not shown in the drawings) in meshing engagement with the coaxial gear set <NUM>. The housing <NUM> is provided, at a front end and a rear end thereof, respectively, with a first cover <NUM> and a second cover <NUM> fastened thereto and covering thereon for protection of internal components arranged therein. Two ends of the transmission axle <NUM> are rotatably mounted, as being each supported by a bearing, to the housing <NUM> and the first cover <NUM>. The end of the transmission axle <NUM> that extends outside of the housing <NUM> is formed with a mounting section <NUM> and a coupling section <NUM> for mounting the coaxial gear set <NUM> thereon to realize an operative coupling relationship therebetween. The internally toothed ring track <NUM> is fixed to an inner circumference of the first mounting compartment <NUM> of the housing <NUM> at a location corresponding to a site where the transmission axle <NUM> penetrates therethrough.

For a detailed structure of the coaxial gear set <NUM>, reference being had to <FIG> and <FIG>, the coaxial gear set <NUM> comprises a modularized structure formed of a sun gear <NUM>, a planetary gear set <NUM>, and an output member <NUM>, wherein the sun gear <NUM> is formed with a coupling hole <NUM> that is fit over the mounting section <NUM> of the transmission axle <NUM>, and a coupling block <NUM> is inserted into and disposed in the coupling hole <NUM> to engage with the coupling section <NUM> of the transmission axle <NUM>. A fastening member <NUM> penetrates through and presses on the coupling block <NUM> and is then fastened to the transmission axle <NUM> (as shown in <FIG>), so that the coaxial gear set <NUM> is selectively mounted to the mounting section <NUM> of the transmission axle <NUM> by means of the sun gear <NUM>. Two ends of the sun gear <NUM> are respectively provided with a first bearing <NUM> and a second bearing <NUM> in order to rotatably mount the planetary gear set <NUM>. The planetary gear set <NUM> comprises a first carrier frame <NUM>, a second carrier frame <NUM>, and a plurality of planetary gears <NUM> that mesh with and surround the sun gear <NUM>, wherein the first carrier frame <NUM> is mounted by the first bearing <NUM> to one of the ends of the sun gear <NUM>, and the second carrier frame <NUM> is provided, at a center thereof, with an axle tube <NUM> for mounting the output member <NUM>, and a free end of the axle tube <NUM> is rotatably mounted, by means of a bearing, to the second cover <NUM>. Further, the axle tube <NUM> of the second carrier frame <NUM> is provided, at a center thereof, with a stepped mounting hole <NUM> that receives an end of a mounting axle <NUM> to penetrate therethrough for pressing thereon, such that an end of the mounting axle <NUM> is mounted, by means of the second bearing <NUM>, to an opposite one of the ends of the sun gear <NUM>. The mounting axle <NUM> is formed with a through hole <NUM>, which receives a hand tool to insert therein for operating the fastening member <NUM> of the coupling block <NUM> of the sun gear <NUM>. Surfaces of the first and second carrier frames <NUM>, <NUM> that face each other are respectively provided with a plurality of counterbored-hole pillars <NUM>, <NUM>, which are set in abutting engagement with each other and respectively receive threaded fastening elements <NUM>, <NUM> to penetrate therethrough for mutually fastening to each other, so as to have the first and second carrier frames <NUM>, <NUM> on the sun gear <NUM> to attach to each other as a unity. A plurality of axle bars <NUM> are arranged between the first and second carrier frames <NUM>, <NUM> for mounting the planetary gears <NUM>. Each of the axle bars <NUM> rotatably supports a corresponding one of the planetary gears <NUM> by means of at least one bearing <NUM>. Each of the planetary gears <NUM> includes a first toothed portion <NUM> (as shown in <FIG>) that simultaneously mesh with both the sun gear <NUM> and the internally toothed ring track <NUM>, and each of the planetary gears <NUM> is provided with a second toothed portion <NUM> (as shown in <FIG>) located at one side of and integrated with the first toothed portion <NUM> to mesh with the output member <NUM>, so that the sun gear <NUM> of the coaxial gear set <NUM> may simultaneously drive the first toothed portions <NUM> of the planetary gears <NUM>, and as being constrained by the internally toothed ring track <NUM>, the planetary gears <NUM> are forced to generate spinning and orbiting motions. Further, the second toothed portions <NUM> of the planetary gears <NUM> synchronously drive the output member <NUM>, and the output member <NUM> is rotatably mounted, by means of a third bearing <NUM>, to the axle tube <NUM> of the second carrier frame <NUM> of the planetary gear set <NUM>. The output member <NUM> is formed, on an inner circumference thereof, with an internal toothed circumference <NUM> that is engageable with the second toothed portions <NUM> of the planetary gears <NUM> of the planetary gear set <NUM>, and the output member <NUM> is formed, on an outer circumference thereof, with a driving wheel portion <NUM> that is engageable with the driven member (not shown in the drawings). The driving wheel portion <NUM> can be an externally toothed wheel or a frictional wheel, and in the present invention, an externally toothed wheel is taken as an example for the driving wheel portion <NUM> of the output member <NUM>.

As such, the coaxial gear set <NUM> can be assembled in advance, and is selectively mountable to the transmission axle <NUM> of the housing <NUM> to be in meshing engagement with the internally toothed ring track <NUM> to thereby form a modularized coaxial gear set reduction mechanism.

An actual operation of the present invention will be described. As shown in <FIG>, <FIG>, and <FIG>, since the sun gear <NUM> of the coaxial gear set <NUM> receives the planetary gear set <NUM> and the output member <NUM> to mount thereon <NUM>, the coaxial gear set <NUM> can be pre-assembled as a modularized unity structure in a workshop, so that an operator is allowed to have the coaxial gear set <NUM> completely mounted on the transmission axle <NUM> in a one-time operation by means of the sun gear <NUM>, with the first toothed portions <NUM> of the planetary gears <NUM> of the planetary gear set <NUM> of the coaxial gear set <NUM> being put into engagement with the internally toothed ring track <NUM> of the housing <NUM>, and the transmission axle <NUM>, when being driven, may synchronously drive the sun gear <NUM> of the coaxial gear set <NUM> so as to cause the sun gear <NUM> to synchronously drive the planetary gear set <NUM>, and due to the first toothed portions <NUM> of the planetary gears <NUM> being in engagement with the internally toothed ring track <NUM> (as shown in <FIG>), the planetary gears <NUM> are spinning while synchronously orbiting around the sun gear <NUM>. Further, since for each of the planetary gears <NUM>, the second toothed portion <NUM> in formed as an integrated structure with the first toothed portion <NUM>, and the second toothed portion <NUM> of each of the planetary gears <NUM> is in meshing engagement with the output member (as shown in <FIG>), the planetary gears <NUM> may drive, in a synchronized manner, the output member <NUM> to then drive the driven member (not shown in the drawings).

Claim 1:
A coaxial gear set reduction mechanism, comprising:
a housing (<NUM>);
a transmission axle (<NUM>), which is rotatably mounted in the housing (<NUM>);
an internally toothed ring track (<NUM>), which is fixed to the housing (<NUM>);
a coaxial gear set (<NUM>), which comprises a sun gear (<NUM>), a planetary gear set (<NUM>), and an output member (<NUM>), wherein the sun gear (<NUM>) is selectively mountable to and connected to the transmission axle (<NUM>) to rotate together therewith; the planetary gear set (<NUM>) is arranged, in a rotatable manner, between two ends of the sun gear (<NUM>), and the planetary gear set (<NUM>) is simultaneously in meshing engagement with the sun gear (<NUM>) and the internally toothed ring track (<NUM>); and the output member (<NUM>) is arranged at one side of the planetary gear set (<NUM>) that is opposite to the internally toothed ring track (<NUM>), and the output member (<NUM>) is driven by the planetary gear set (<NUM>),
characterized in that one end of the transmission axle (<NUM>) is formed with a mounting section (<NUM>) and a coupling section (<NUM>), and the sun gear (<NUM>) of the coaxial gear set (<NUM>) is formed, in a center thereof, with a coupling hole (<NUM>) that is fit over the mounting section (<NUM>), a coupling block (<NUM>) being inserted into and disposed in the coupling hole (<NUM>) to engage with the coupling section (<NUM>) of the transmission axle (<NUM>), a fastening member (<NUM>) penetrating through and pressing on the coupling block (<NUM>) and fastened to the transmission axle (<NUM>), wherein the planetary gear set (<NUM>) of the coaxial gear set (<NUM>) comprises a first carrier frame (<NUM>) and a second carrier frame (<NUM>) that are opposite to each other and are respectively and rotatably arranged at two ends of the sun gear (<NUM>), a plurality of planetary gears (<NUM>) being rotatably arranged between the first and second carrier frames (<NUM>, <NUM>) and around an outer circumference of the sun gear (<NUM>), each of the planetary gears (<NUM>) comprising a first toothed portion (<NUM>) synchronously meshing with the sun gear (<NUM>) and the internally toothed ring track (<NUM>), each of the planetary gears (<NUM>) further comprising a second toothed portion (<NUM>) meshing with the output member (<NUM>), the output member (<NUM>) being rotatably mounted on the second carrier frame (<NUM>) of the planetary gear set (<NUM>).