Title of Invention

ASYMMETRIC PLANETARY GEAR DEVICE

Abstract An asymmetric planetary gear device having planet gears consisting of unified tire parts of a smaller side roller par a gear part and a larger side roller part. Tile internal gear also has a smaller side ring part, a gear part and a larger side ring part which are unified in a body. A sun gear shaft can be inserted into or plucked out of the device after assembly. A small sun gear heightens the reduction ratio. The device is suitable for a reduction device of electric washing machines.
Full Text This invention relates to a planetary gear device provided with unified planet gears and a unified internal gear. Planetary gear devices have a wide scope of applications in various industries as decelerators or accelerators. In particular this invention aims at an improvement of the side-disc of planetary gear devices having planet gears with side discs and an internal gear with side rings.
A planetary gear device has a sun gear, three or four planet gears, an internal gear and a carrier. A planet gear meshes with a sun gear and an internal gear. A three-planet gear type has six meshing points. A four-planet gear type has eight meshing points. The number of gears is larger than the number of meshing points. One problem of a planetary gear device is the differences of torques at the meshing points which are caused by the lack of the freedom of the gears. The imbalance of torques decreases the efficiency as a reduction gear unit by causing an excess radial engagement at one meshing point. The strong radial force at the meshing point induces a large friction and reduces the efficiency of transmitting the torque. One solution is raising the accuracy of cutting teeth of the gears. Pursuing the precision enhances the cost of production.
The applicant has sought another way of solving the problem of discrepancy of torques or forces at the meshing points. The applicant contrived an improvement of adding side rollers to the planet gears and affixing side rings to the internal gear. Japanese Patent Laying Open No.58-94656 (laid open on June, 4, 1983) disclosed such a side-roller type

device for the first time. Each side roller has a diameter which is nearly equal to the tooth-edge circle of the planet gear. Each side ring of the internal gear has a diameter which is nearly equal to the tooth-root circle of the internal gear. Thus, the applicant called his new device as a tooth-edge side-roller type. The side-roller type exhibited an advantage of suppressing the differences of torques among different meshing points by the radial contacts of the planet side rollers and the internal side rings. This t3T)e had another merit of being feasible for unification of the tooth-root side rings and the internal gear.
Several concepts of a gear are now explained for facilitating the understanding of the present invention. An outer-toothed gear has teeth extending outward from a rim. An inner-toothed gear has teeth extending inward from a ring rim. The sun gear and the planet gears are outer-toothed gears. The internal gear is an inner-toothed gear. There are three different circles defined with regard to a gear. A pitch circle is the most important circle which represents the effective circle of the gear. The diameter D of a pitch circle is given by the product D=mZ of the module m and the tooth number Z. A tooth-edge circle is a circle which passes the tips of all teeth. A tooth-root circle is a circle which connects the roots of all teeth.
In a standard outer-toothed gear, the radius of the tooth-edge circle is longer than the radius mZ/2 of the pitch circle by one module m. Thus, the radius of the tooth-edge circle is m(Z/2+l). In the same gear, the radius of the tooth-root circle is shorter than the radius of the pitch circle by 1.2 module. Thus, m(Z/2-1.2) is the radius of the tooth-root circle of an

ordinary outer-toothed gear. 0.2 module is a margin of preventing the teeth from overmeshing. The relation is reversed in an inner-toothed gear. The tooth-root circle has a largest radius of m(Z/2+1.2). The tooth-edge circle has a smallest radius of m(Z/2-l). In the improvement, since the side rings of the internal gear have a tooth-root circle, two side rings and the internal gear can be produced in a body by plastic molding in the case of a plastic internal gear. Thus the internal gear and the side rings are reduced to a single ring-carrying internal gear.
The tooth-edge roller type sharply contradicted the common sense of the skilled in the art, because the line velocities of the side rollers and the side rings are different at the touching points. The line velocity of the planet side rollers is larger than that of the internal side rings. The applicant, however, discovered that the difference of line velocities causes little friction loss. The coupling of the planet rollers and the internal rings suppresses the over meshing of teeth but induces no bad influence upon the torque transmission despite the apparent difference of the line velocities.
The tooth-edge disc type planetary gear devices have been used as decelerators of electric washing machines in a large scale because of the convenient structure having an input shaft and an output shaft along the same axial line. Electric washing machines are inexpensive electric machines. The abundant application to electric washing machines requires the reduction of cost and an increment of the deceleration ratio. The enlarging amount of washing requires higher power and a higher reduction ratio for gears. The reduction ratio is determined by the ratio of the tooth number of the sun

gear to the tooth number of the internal gear. The reduction of cost
demands a decrease of the size. Therefore, the size of the sun gear must be
reduced. ,
In assembling a washing machine, a cylindrical basket is placed at the highest position, a reduction gear is ^quipped in secession to the basket below and a motor is placed at the bottom in series. In the structure, it is suitable that an output shaft of the motor can be inserted into the reduction device as a sun gear. The tooth-edge side roller type devices cannot satisfy the requirements at present. Since the diameter of the side roller is bigger than that of the planet gear itself, the sun gear cannot be inserted into the space enclosed by the planet gears after the construction of the reduction device. Because the side rollers are bigger than the planet gear in diameter, the side rollers cannot be unified to the planet gear. A planetary gear of this type requires three parts, that is, a planet gear and two side tooth-edge rollers. Large number of parts impedes the reduction of cost.
The Inventor once tried to make an ambitious planetary gear device of unifying three planet parts into a single planet gear having two side roller parts. This was an "asymmetric unified planetary gear device" which was applied as Japanese Patent Application No.62-262274(262274/'87), was laid open as Japanese Patent Laying Open No. 1-105039(105039/'89) and was published as Japanese Patent Publication No.5-7575(7575/'93). The asymmetric unified planetary gear devices boldly challenged the prevalept common sense of the planetary gear technology. The unification of three parts into one enables us to decrease the cost of production and the cost of assembly. The

differences of line velocities, however, become more conspicuously. The Inventor confirmed the fact that the differences of the line velocities make no significant difficulty on rotation and allow the reduction gear device to rotate as smooth as the prior one with separated three planetary parts. Such a convenient property is proved by experiences. The fact that the asymmetric planetary gear device can rotate smoothly is not a speculative one but is an experimental fact.
The novel asymmetric planetary gear device, however, had a problem as a reduction gear. Fig.6 shows the asymmetric planetary gear device in a horizontal posture. An Internal gear (3) Is sustained in a horizontal plane with a main carrier (4A) up and a subcarrier (4B) down by a casing (not shown in the figures), when the device is used as a reduction gear of an electric washing machine. The basket is fixed upon the main carrier, and the motor is positioned beneath the subcarrier (4B) for inserting an output shaft with a sun gear part into a hole of the sun gear (S). The weight of the carriers (4A) and (4B) and the planet gears (2) is transmitted through a contact region (C) between an upper side (52) of the Internal gear (3) and an inner side (51) of the main carrier (4A). The coupling of the planet gears (2) and the internal gear (3) does not contribute to support the weight of the carrier (4) and gears (2). The Internal gear (3) is at rest but the main carrier (4A) rotates. The dynamical friction loss at the circular contact (C) is large. The big friction loss at the circle (C) Induces the reduction of transmission efficiency, the wearing of the internal gear (3) and the generation of noise. This is a serious difficulty of the asymmetric planetary gear units. Another problem is the impossibility of inserting the

sun gear into the device after assembling. The electric washing machines require the possibility of inserting a motor shaft into a reduction device or extracting the motor shaft from the reduction device.
An object of the present invention is to provide a low cost planetary gear device having side rollers and rings. Another object of the present invention is to provide a planetary gear device which allows a motor shaft to be inserted into the device as a sun gear. A further object of the present invention is to provide a planetary gear device which gives a high reduction ratio suitable for washing machines.
The planetary gear device is constructed with a plurality of planet gears having a smaller side disc part and a larger side disc part, an internal gear having a larger side ring part and a smaller side ring part, and a carrier for supporting the planet gears by planet shafts. A feature of the device is a unified asymmetric planet gear having a smaller side disc part and a larger side disc part. Three parts, i.e., a gear, a side disc and the other side disc are integrated into one planet gear. Thus, a three planet gear type can curtail six parts, and a four planet gear type can save eight parts. The decrease of the number of parts reduces the cost of production. The existence of the smaller side disc parts allows a motor shaft to be inserted into the device as a sun gear, which is convenient to the reduction device of electric washing machines.
Accordingly the present invention provides an asymmetric planetary gear device comprising a plurality of planet gears, an internal gear enclosing the planet gears and a carrier having a subcarrier with an aperture and a main carrier with an output hole and rotatably supporting the planet gears with planet shafts; characterized in that the planet gear is a unified member having a planet gear part, a smaller side roller part with a diameter smaller than a tooth-root circle of the planet gear part on a side near the subcarrier and a larger side roller part with a diameter larger than a tooth-edge circle of the planet gear part on another side near the main carrier, the internal

gear has a gear part, a smaller side ring part with a diameter smaller than the tooth-edge of the internal gear part and a larger side ring part with a diameter larger than the tooth-root of the internal gear part, and the planet gears enclose a central space in which a sun gear shaft can be inserted or plucked after assembling.
BRIEF DESCRIPTION OF THE DRAWINGS
With reference to the accompanying drawings in which :
Figure 1 is a sectional front view of a planetary gear device as a first embodiment of the present invention.

Fig. 2 is a right side view of the same planetary gear device.
Fig.3 is a sectional front view of another planetary gear device as a second embodiment of the present Invention.
Fig.4 is a sectional front view of another planetary gear device as a third embodiment of the present invention.
Fig. 5 Is a sectional front view of the other planetary gear device as a fourth embodiment of the present invention.
Fig. 6 is a sectional view of a prior asymmetric planetary gear unit which was invented by the present inventor and had been laid open on Japanese Patent Laying Open No. 1-105039.
Fig. 7 is a partial perspective view of the internal gear of the device shown in Fig. 5.
DETAILED DESCRIPTION OF EMBODIMENTS An embodiment of the present Invention shown In FIg.l and Fig.2 has three planet gears (2), an internal gear (3) and a carrier (4). The carrier (4) has a main carrier (4A) and a subcarrier (4B) which are discs for supporting the planet gears (2) by planet shafts (5).
The planet gear (2) has a gear part (6) In the middle, a smaller side roller part (7) in the left and a larger side roller part (8) in the right in FIg.l. The smaller side roller part (7) Is smaller than the tooth-root circle by 0 module to 2 modules in diameter. The larger side roller part (8) Is larger than the tooth-edge circle by 0 module to 2 modules in diameter. The planet gear (2) and the side rollers (7) and (8) are unified in a body.
One of the features is the unified character of the planet gear

(2) including the gear part (6), the smaller side roller part (7) and the larger side roller part (8). Unification requires that at least one side roller should be smaller than the tooth-root circle, because the smaller side roller part allows metallic molds to be plucked up from the products of planet gears in the axial direction in a plastic injection molding. Thus, this invention adopts a smaller disc which is smaller than the tooth-root circle and a larger disc which is larger than the tooth-edge circle. The asymmetry is a result of the unification. The unification would be entirely impossible if both side rollers were to be tooth-edge ones. The planet gear (2) has a hub part (9) and an intermediate part (10). The material is curtailed by the shape in which the hub part (9) is connected to the gear part (6) by the thin intermediate part (10).
In accordance with the asymmetric planet gear (2), the internal gear (3) is also asymmetric. The internal gear (3) has a gear part (12) in the middle, a narrower ring part (13) in the left and a wider ring part (14) in the right in Fig.l. The smaller (narrower) ring part (13) is smaller than the tooth-edge circle by 0 module to 2 modules in diameter. The larger (wider) ring part (14) is larger than the tooth-root circle by 0 module to 2 module in diameter. The internal gear part (12) meshes with the planet gear parts (6). The left narrower side ring part (13) is sometimes in contact with the left smaller side roller parts (7) of the planet gears (2). The right wider (larger) side ring part (14) is sometimes in contact with the right larger side roller parts (8) of the planet gears (2). The asymmetry enables the plastic injection molding to make the internal gear (3) as a single body. The internal gear (3) has several projections (15) on the outer surface so as to fix the internal

gear in a casing (not shown in the figures).
The subcarrier (4B) and the main carrier (4A) are assembled by first coupling protrusions (16) of the main carrier (4A) and second coupling protrusions (17) of the subcarrier (4B). The second protrusion (17) has a hole (18). The first protrusion (16) has a plug (19). The main carrier (4A) and the subcarrier (4B) are coupled by inserting the plug (19) into the hole (18), pressing the tip of the plug (19), and widening the tip.
The main carrier (4A) has an output hole (21) with spline, as shown in Fig. 2. The subcarrier (43) has an aperture (22) for permitting a sun gear shaft to penetrate into a space enclosed by the planet gears (2). The carriers (4A) and (4B) have three pairs of the protrusions (16) and (17). The carriers (4A) and (4B) have three pairs of protuberances (23) and (24) for sustaining the planet shafts (5) in the directions bisecting the neighboring protrusions (16) and (17). The protuberances (23) and (24) kill the axial fluctuation of the planet gears (2) by contacting with the sides of the hub parts (9). The protuberances (23) and (24) have holes (25) and (26) which hold the ends of the planet shafts (5). Wide cavities (27) formed between the planet gears (2) and the carriers (4B) and (4A) can store grease or lubricant oil for alleviating the friction loss of power.
The planetary gear device shown by Fig.l and Fig.2 lacks a sun gear. The planet gear (2) is unified in a body. The smaller side roller parts (7) are positioned in the vicinity of the aperture (22) of the subcarrier (4B). The larger side roller part (8) is close to the output hole (21). These are features of the embodiment of Fig.l. An external shaft, for example, a motor shaft (30) can freely be inserted into a central space (28) enclosed by the

planet gears (2) after assembling. The motor shaft (30) has a shaft part (31), a sun gear part (32), a brim (33) and a front face (34). The sun gear part (32) is cut on the round surface of the shaft. Since the imaginary circle enclosed by the smaller roller parts (7) is wider than the tooth-edge circle of the sun gear part (32), the sun gear part (32) of the motor shaft (30) can penetrate the aperture (22) and mesh with the planet gears (2). The front face (34) is stopped by the larger side roller (8) of the planet gear (2). When the motor shaft (30) rotates, the planet gears (2) and the carrier (4) rotate in proportion to the rotation of the motor shaft (30). Radial forces are transmitted by the contacts between the smaller roller parts (7) and the smaller ring part (13) and between the larger disc parts (8), and the larger ring part (14). Since the radial displacement is alleviated by the radial interaction between the smaller side roller parts (7) and the smaller side ring part (13) and between the larger side roller parts (8) and the larger side ring part (14), no overmeshing occurs between the planet gears (2) and the internal gear (3). This embodiment is the most suitable for the reduction device of electric washing machines, since the motor shaft with a sun gear part can be inserted into and be plucked up from the central space (28) enclosed by the planet gears (2). Since the sun gear part (32) is directly formed on the tip of the motor shaft (30), the reduction ratio can be raised by thinning the sun gear shaft (30). The reduction ratio is given by S/(S+I), where S is the tooth number of the sun gear and I is the tooth number of the internal gear. The high reduction ratio means high ratio of (S+l)/S. Since the sun gear is directly formed on the shaft, high reduction ratio can be accomplished by reducing the diameter of the sun gear part (32). In the

electric washing machine, the basket is installed at the highest position, the planetary gear device is provided at the middle height and the motor is equipped at the bottom. The internal gear (3) is supported in a horizontal plane by a casing in the orientation with the main carrier (4A) up and the subcarrier (4B) down. In the orientation, the weight of the carriers (4) and the planet gears (2) is doubly transmitted on the internal gear (3) by both the contacts (B) between the sides of the larger side roller parts (8) and the side of the internal gear part (12) and the contacts (A) between the sides of the planet gear parts (6) and the side of the smaller side ring part (13). These properties make the embodiment to be the most suitable reduction gear for electric washing machines.
Fig. 3 shows another embodiment which has a sun gear in the device. When the inverse (S+I)/S of the reduction ratio is not so high, the device can include a built-in sun gear (35) having an input hole (36). The sun (input) hole (36) is a D-shaped hole or a splined hole for transmitting the rotation torque from an input shaft to the built-in sun gear (35). Since the smaller side roller parts (7) lie on the side of the aperture (22), the planet gears (2) cannot keep the sun gear (35) in the space (28) enclosed by the planet gears (2). Then, the embodiment narrows the aperture (22) of the subcarrier (4B) and forms a retainer (37) projecting on an inner side of the aperture (22). The sun gear (35) is sandwiched by the larger side roller parts (8) and the retainer (37). The retainer (37) has holes (38) for guiding grease into the inner space among the planet gears, the sun gear and the internal gear. The small holes (38) keep grease. The friction loss is alleviated by the grease or lubricant oil.

Fig. 4 exhibits a third embodiment. The planet shafts (5) are omitted by prolonging the protuberance (24) of the subcarrier (4B) to the main carrier (4A). A first extending part (40) supports the planet gears (2) by piercing the hole (11) of the planet gears (2). A second extending part (41) is fixed in a hole (42) of the main carrier (4A). An axial hole (43) saves the material of the carrier (4). The embodiment succeeds in curtailing the production cost further by saving the planet shafts (5). The sun gear can be inserted in the central space (28). Otherwise a built-in sun gear is also available in the embodiment.
Fig.5 and Fig.7 exhibit the other embodiment which makes a grease pocket (44) by cutting a side of the internal gear part (12). A small cavity is generated between the side of the teeth of the internal gear part (12) and the sides of the planet larger side roller parts (8). The grease stored in the pocket (44) raises the lubricancy between the planet gears (2) and the internal gear (3). The grease pocket reduces the noise and extends the lifetime of the planetary gear device.




WE CLAIM:
1. An asymmetric planetary gear device comprising a plurality of planet gears (2), an internal gear (3) enclosing the planet gears (2) and a carrier (4) having a subcarrier (4B) with an aperture and a main carrier (4A) with an output hole and rotatably supporting the planet gears (2) with planet shafts (5) characterized in that the planet gear (2) is a unified member having a planet gear part (6), a smaller side roller part (7) with a diameter smaller than a tooth-root circle of the planet gear part (6) on a side near the subcarrier (4B) and a larger side roller part (8) with a diameter larger than a tooth-edge circle of the planet gear part (6) on another side near the main carrier (4A), the internal gear (3) has a gear part (12) a smaller side ring part (13) with a diameter smaller than the tooth-edge of the internal gear part (12) and a larger side ring part (14) with a diameter larger than the tooth-root of the internal gear part (12), and the planet gears (2) enclose a central space in which a sun gear shaft can be inserted or plucked after assembling.
2. An asymmetric planetary gear device comprising a sub gear (35), a plurality of planet gears (2) meshing with the sun gear (35), in an internal gear (3) enclosing the planet gears (2) and a carrier (4), having a subcarrier (4B) with an aperture and a main carrier (4A) with an output hole and rotatably supporting the planet gears (2) with planet shafts (5); wherein the planet gear (2) is a unified member having a planet gear part (6), a smaller side roller part (7) with a diameter smaller than a tooth-root circle of the planet gear part (6) on a side near the subcarrier (4B) and a larger side roller part (8) with a diameter larger than a tooth-edge circle of the planet gear part (6) on another side near the main carrier (4A), the internal gear (3) has a gear part (12), a smaller side ring part (13) with a diameter smaller than the tooth-edge of the internal gear part (12) and a larger side ring part (14) with a diameter larger than the tooth-root of the internal gear part (12), and a retainer (37) of the carrier (4) holds the sun gear (35) within a central space (28) enclosed by the planet gears (2).

3. The asymmetric planetary gear device as claimed in claim 1, wherein the planet shafts are replaced by parts extending from the subcarrier (4B) or the main carrier (4A).
4. The asymmetric planetary gear device as claimed in claim 1, wherein grease pockets (44) are formed between a side of the internal gear teeth and a sides of the larger side roller parts (8).
5. An asymmetric planetary gear device substantially as herein described with reference to the accompanying drawings.

Documents:

2227-mas-1996 abstract duplicate.pdf

2227-mas-1996 abstract.pdf

2227-mas-1996 claims duplicate.pdf

2227-mas-1996 claims.pdf

2227-mas-1996 correspondence others.pdf

2227-mas-1996 correspondence po.pdf

2227-mas-1996 description (complete) duplicate.pdf

2227-mas-1996 description (complete).pdf

2227-mas-1996 drawings.pdf

2227-mas-1996 form-1.pdf

2227-mas-1996 form-26.pdf

2227-mas-1996 form-4.pdf

2227-mas-1996 petition.pdf


Patent Number 198117
Indian Patent Application Number 2227/MAS/1996
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date
Date of Filing 10-Dec-1996
Name of Patentee MATEX CO., LTD
Applicant Address 2-6 OBASE-CHO, TENNOJI-KU, OSAKA
Inventors:
# Inventor's Name Inventor's Address
1 SHOJI IGAKU 365-2 MATSUZUKA YAMATOTAKADA-SHI, NARA
PCT International Classification Number F16H1/28
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA