Patent Description:
A known reduction mechanism has only a limited speed reduction ratio. To achieve a relatively large speed reduction ratio, it is necessary to increase the gear ratio between the sun gear and the peripheral planetary gears. This would expand the outside diameter of the entire reduction device and also affects the output torque thereof. For this, the manufacturers have developed multi-staged planetary gears to overcome such a problem, such as <CIT>, which discloses a planetary gear reducer, in which a gear carrier is provided with a first gear and a second gear mounted thereon, wherein the first gear is in meshing engagement with a sun gear and a fixed first ring gear, while the second gear is in meshing engagement with the sun gear and a second ring gear that is in connection with a transmission member. Since the first and second gears are individually mounted on the gear carrier and both are simultaneously in meshing engagement with the sun gear, when the gear ratio of the first and second gears is incorrect, interference occurs and easy generation of vibration noise during the operation may result. Also, the axle distance of the entire device is increased. Since the first and second gears must mesh the sun gear together, the range of the gear ratio is limited, making it not possible to enhance the effect of speed reduction.

In other words, the known reduction mechanism suffers incapability of reduction of size and increase of speed reduction ratio and may generate operation noise and vibration due to interference, and even causes wear and abrasion of gears to result in shortening of the service life thereof.

Prior art patent documents are known. For example, <CIT> discloses a hoist with gear reduction, in which a housing and a motor having motor shaft arranged in the housing are provided. A planetary drive system is arranged on the motor shaft and includes a sun gear arranged on the motor shaft, planet gears mounted on a planet gear carrier and including pinions meshing the sun gear, and a ring gear surrounding and meshing the planet gears. A second ring gear is also in meshing engagement with the planet gears to serve as an output gear. <CIT> discloses an electric axle drive that includes a motor having a shaft connected to a planetary gear system that includes a sun gear in engagement with a first planetary gear stage of a stepped planetary gear. A first ring gear fixed in a housing of the planetary gear system. The stepped planetary gear has a second planetary gear stage that serves as an output stage.

The primary objective of the present invention is to feature both a short axle distance and a large speed ratio, in order to effectively reduce the size and also to enhance the effect of speed reduction.

A second objective of the present invention is to reduce interference in order to make an overall operation smoother and to reduce vibration and noise.

A further objective of the present invention is to make the entire structure more stable and secured and to enhance the degree of meshing engagement, so as to reduce unnecessary wear and abrasion during operation, to thereby extend the service life and also to improve the transmission efficiency.

The present invention provides a short-axle large-speed-ratio gear set structure, which comprises: a housing; a transmission axle, which is rotatably mounted in the housing, the transmission axle being provided with a sun gear; an internally-toothed ring track, which is fixed to the housing; a planetary gear set, which comprises a first carrier frame and a second carrier frame that are opposite to each other, a plurality of stepped planetary gears being rotatably arranged between the first and second carrier frames and around an outer circumference of the sun gear, each of the stepped planetary gears comprising a first toothed portion synchronously meshing with the sun gear and the internally-toothed ring track, each of the stepped planetary gears further comprising a second toothed portion that is integrated and rotatable with the first toothed portion; and an output member, which has an inner circumference that is formed with an internal toothed circumference meshing with the second toothed portion of each of the stepped planetary gears, the output member having an outer circumference that is formed with a driving wheel portion for driving purposes, wherein the second carrier frame of the planetary gear set is provided, at a center thereof, with an axle tube, the axle tube rotatably supporting the output member by means of a third bearing, wherein the axle tube of the second carrier frame is provided, at a center thereof, with a stepped mounting hole that receives a mounting axle to penetrate therein, one end of the mounting axle being rotatably mounted on an end of the sun gear, wherein the mounting axle is formed with a through hole, and wherein the first and second carrier frames of the planetary gear set are rotatably mounted, by means of a first bearing and a second bearing arranged at centers thereof, to two ends of the sun gear, such that the sun gear, the planetary gear set, and the output member are assembled together as a coaxial gear set.

Particular embodiments of the invention are laid down in the dependent claims.

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 transmission axle <NUM> is rotatably arranged in the first mounting compartment <NUM> for mounting the coaxial gear set <NUM> that is arranged on the transmission axle <NUM>. 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, respectively at of a front end and a rear end thereof, with a first cover <NUM> and a second cover <NUM> fastened thereto and covering thereon for protection of internal components thereof. 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 through the housing <NUM> is formed with a mounting section <NUM> and a coupling section <NUM> for receiving the coaxial gear set <NUM> to mount thereon and to realize an operative coupling relationship therebetween. The internally-toothed ring track <NUM> is fixed to the inner circumference of the first mounting compartment <NUM> of the housing <NUM> to receive the coaxial gear set <NUM> to mesh therewith.

For a detailed structure of the coaxial gear set <NUM>, reference being had to <FIG>, <FIG>, and <FIG>, the coaxial gear set <NUM> comprises a modularized structure formed of a sun gear <NUM>, a planetary gear set <NUM>, and a output member <NUM>, wherein the sun gear <NUM> and the transmission axle <NUM> are arranged as an integrated unity structure or a combined structure, and in the present invention, the sun gear <NUM> and the transmission axle <NUM> being arranged to form a combined structure is taken as a primary example. The sun gear <NUM> is formed, in a center thereof, with a coupling hole <NUM> that is fit over the mounting section <NUM> of the transmission axle <NUM>. 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>, and the planetary gear set <NUM> is rotatably mounted on the sun gear <NUM> by means of a first bearing <NUM> and a second bearing <NUM> that are arranged at two ends of the sun gear <NUM>. According to some embodiments, the first and second bearings <NUM>, <NUM> of the planetary gear set <NUM> may alternatively arranged at two ends of the transmission axle <NUM> that correspond to the sun gear <NUM>. Further, at the two ends of the sun gear <NUM>, a first carrier frame <NUM> and a second carrier frame <NUM>, and also a plurality of stepped planetary gears <NUM> that mesh with and surround the sun gear <NUM> are arranged, 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> (as shown in <FIG>). The axle tube <NUM> of the second carrier frame <NUM> is provided, at a center thereof, with a stepped mounting hole <NUM> that receives a mounting axle <NUM> to penetrate therein and press 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> of 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 stepped planetary gears <NUM>. Each of the axle bars <NUM> rotatably supports a corresponding one of the stepped planetary gears <NUM> by means of at least one bearing <NUM>. Each of the stepped 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 stepped planetary gears <NUM> is provided with a second toothed portion <NUM> (as shown in <FIG>) located at one side 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 stepped planetary gears <NUM> to cause each of the stepped planetary gears <NUM> to generate spinning in a reversed direction (relative to a rotation direction of the sun gear <NUM>, this being applicable hereinafter), and at the same time, being constrained by the internally-toothed ring track <NUM>, the stepped planetary gears <NUM> are caused to simultaneously generate orbiting relative to the sun gear <NUM> in the same direction (as shown in <FIG>) for driving the planetary gear set <NUM>. Further, the second toothed portions <NUM> of the stepped planetary gears <NUM> synchronously drive the output member <NUM> to generate an output of rotation in a reversed direction (as shown in <FIG>), and due to the rotation of the planetary gear set <NUM> as the above-described orbiting in the same direction, a phenomenon of backward rotating is induced to thereby enhance an effect of reduction. 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 stepped 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 of the driving wheel portion <NUM> of the output member <NUM>.

As such, the first toothed portions <NUM> of the stepped planetary gears <NUM> of the planetary gear set <NUM> are set in synchronous meshing engagement with the internally-toothed ring track <NUM>, while the second toothed portions <NUM> that are integrally formed therewith are in direct meshing engagement with the internal toothed circumference <NUM> of the output member <NUM>, so as to form a short-axle-distance large-speed-ratio gear set structure.

An actual operation of the present invention will be described. As shown in <FIG>, <FIG>, and <FIG>, since the coaxial gear set <NUM> is arranged such that the planetary gear set <NUM> and the output member <NUM> are mounted on the sun gear <NUM>, so that the coaxial gear set <NUM> can be formed as a modularized structure for directly mounting on the transmission axle <NUM>, such that the first toothed portions <NUM> of the stepped planetary gears <NUM> of the planetary gear set <NUM> of the coaxial gear set <NUM> are in meshing engagement with the internally-toothed ring track <NUM> of the housing <NUM>, and, with the fastening member <NUM> of the coupling block <NUM> of the sun gear <NUM> being fastened to the transmission axle <NUM>, the transmission axle <NUM>, when being driven, may synchronously drive the sun gear <NUM> of the coaxial gear set <NUM> to rotate in synchronization therewith, allowing the sun gear <NUM> to synchronously drive the planetary gear set <NUM> by means of the first toothed portions <NUM> of the stepped planetary gears <NUM> to cause each of the stepped planetary gears <NUM> of the planetary gear set <NUM> to generate spinning in a reversed direction (relative to the rotation direction of the sun gear <NUM>, this being equally applied below), and due to being constrained by the internally-toothed ring track <NUM> that is fixed in position, the first and second carrier frames <NUM>, <NUM> of the planetary gear set <NUM> are caused to drive each of the stepped planetary gears <NUM> to generate orbiting about the sun gear <NUM> synchronously and in the same direction (as shown in <FIG>). The second toothed portion <NUM> of each of the stepped planetary gears <NUM>, being in meshing engagement with the internal toothed circumference <NUM> of the output member <NUM>, may synchronously drive the output member <NUM> to generate reversed-direction rotation (as shown in <FIG>). Due to the rotation of the planetary gear set <NUM> as orbiting synchronously and in the same direction, the planetary gear set <NUM> is caused to generate a phenomenon of backward rotation, and this could enhance the effect of speed reduction. And, the output member <NUM>, due to being coupled, by means of the driving wheel portion <NUM> of the outer circumference thereof, with the driven member, may drive the driven member (not shown in the drawings).

Claim 1:
A short-axle large-speed-ratio gear set structure, comprising:
a housing (<NUM>);
a transmission axle (<NUM>), which is rotatably mounted in the housing (<NUM>), the transmission axle (<NUM>) being provided with a sun gear (<NUM>);
an internally-toothed ring track (<NUM>), which is fixed to the housing (<NUM>);
a planetary gear set (<NUM>), which comprises a first carrier frame (<NUM>) and a second carrier frame (<NUM>) that are opposite to each other, a plurality of stepped 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 stepped 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 stepped planetary gears (<NUM>) further comprising a second toothed portion (<NUM>) that is integrated and rotatable with the first toothed portion (<NUM>); and
an output member (<NUM>), which has an inner circumference that is formed with an internal toothed circumference (<NUM>) meshing with the second toothed portion (<NUM>) of each of the stepped planetary gears (<NUM>), the output member (<NUM>) having an outer circumference that is formed with a driving wheel portion (<NUM>) for driving purposes,
characterized in that the second carrier frame (<NUM>) of the planetary gear set (<NUM>) is provided, at a center thereof, with an axle tube (<NUM>), the axle tube (<NUM>) rotatably supporting the output member (<NUM>) by means of a third bearing (<NUM>), wherein the axle tube (<NUM>) of the second carrier frame (<NUM>) is provided, at a center thereof, with a stepped mounting hole (<NUM>) that receives a mounting axle (<NUM>) to penetrate therein, one end of the mounting axle (<NUM>) being rotatably mounted on an end of the sun gear (<NUM>), wherein the mounting axle (<NUM>) is formed with a through hole (<NUM>), and wherein the first and second carrier frames (<NUM>, <NUM>) of the planetary gear set (<NUM>) are rotatably mounted, by means of a first bearing (<NUM>) and a second bearing (<NUM>) arranged at centers thereof, to two ends of the sun gear (<NUM>), such that the sun gear (<NUM>), the planetary gear set (<NUM>), and the output member (<NUM>) are assembled together as a coaxial gear set (<NUM>).