Gear transmission apparatus

Abstract: A gear transmission apparatus (7) comprises a planetary gear mechanism (57) having an internal gear (59), a plurality of pinion gears (61,63), a pinion carrier (71,73), and a sun gear (65). The pinion carrier (71,73) has an overhang portion (83) extending along an outer periphery of the internal gear (59). The rotation input shaft (23) is rotationally integral with the internal gear (59) while the rotation output shaft (45) is rotationally integral with the sun gear (65). A band brake (87) is provided for braking the pinion carrier (71,73) when brought into frictional contact with the overhang portion (83). A one-way clutch (55) is interposed between the rotation input shaft (23) and the rotation output shaft (45) so as to allow rotation of the rotation output shaft (45) in a speed-increase direction. In a preferred embodiment, either the sun gear (65) or the internal gear (59) is braked by the band brake (87).

Description: This invention relates to a gear transmission apparatus according to the preamble portion of claim 1 for use in a vehicle or the like. An apparatus of this type is disclosed in JP-A- 58 173 854. In this apparatus, an internal gear is coupled to a casing through an electromagnetic clutch to put a planetary gear mechanism into a speed-change state. With the above-mentioned structure including the electromagnetic clutch, an electromagnet and a clutch portion must be located between the planetary gear mechanism and the casing. Accordingly, the apparatus inevitably has a large size in an axial direction. The internal gear located at the side of a brake is cantilevered and has a free end. Since no centering function of the free end is provided, the internal gear often becomes eccentric when subjected to an external force from the electromagnetic clutch. In this event, normal engagement can not be maintained between the internal gear and other gears. This results in vibration, noise, deterioration of durability, and damage of the gears. Japanese Utility Model Laid Open No. 173854/1983 discloses an engine accessory drive apparatus with a planetary gear mechanism. The disclosure is directed to a gear transmission mechanism. The planetary gear mechanism includes an internal gear, a pinion carrier, and a sun gear. One of the internal gear, a pinion carrier, and a sun gear is braked by a braking unit to provide a speed-change state. The braking unit comprises a vacuum actuator. A vacuum may be derived from a vacuum pump or a suction side in an engine drive section. In any event, an output characteristic of an engine is unfavorably affected if the vacuum actuator is used. Alternatively, a hydraulic actuator may be used instead of the vacuum actuator. In this case, when an oil pump for lubrication of the engine is used in common for the hydraulic actuator, a risk of oil leakage increases because a hose is extended around to supply hydraulic fluid. The oil leakage often results in lubrication failure of the engine. On the other hand, installation of an additional oil pump is not desirable in view of an arrangement space. Thus, the above-mentioned structure with a pressure source is disadvantageous because the output characteristic of the engine is unfavorably affected. In addition, it is difficult to optionally incorporate such a structure as a post-fixial assembly because a wide range of modification is necessary including extension of a pressure supply pipe. The object of this invention to provide a gear transmission apparatus with a planetary gear mechanism, which has a small size in an axial direction and which assures good engagement of gears. With the above-mentioned structure, when the band brake brakes the rotation of one of the pinion carrier, and the sun gear, the planetary gear mechanism is put into a speed-change state. Rotation from an input side is changed in speed and transmitted to an output side. When the band brake is released to put the one of the internal gear, the pinion carrier, and the sun gear into a rotation-free state, the rotation from the input side is kept unchanged in speed and transmitted to the output side in accordance with a rotation transmission direction of the one-way clutch. Since the rotation of one of the pinion carrier, the sun gear, and the internal gear is braked by the band brake, functional parts can be arranged in a radial direction. As compared with the conventional apparatus having the electromagnetic clutch, this invention includes no such component arranged along an axial direction. Accordingly, the gear transmission apparatus according to this invention can be reduced in size in the axial direction. Generally, the pinion carrier or the sun gear often becomes eccentric in response to an external force from the band brake. According to this invention, the pinion carrier or the sun gear is centered through a bearing. In this connection, the gears are maintained in good engagement. It is thus possible according to this invention to prevent vibration, noise, deterioration of durability, and damage of the gears. In addition, operation sound is quiet because noise is shut off by presence of an overhang portion. When the braking mechanism is driven by a motor, no direct influence is imposed on the engine and no supply pipe is necessary. Accordingly, the braking mechanism is highly adaptable as an optional assembly. Further advantageous embodiments are set forth in the subclaims. Preferred embodiments of the invention will be described hereinafter with respect to the appended drawings. Fig. 1 is a sectional view of a gear transmission apparatus according to a first embodiment of this invention; Fig. 2 is a sectional view of a band brake for use in the gear transmission apparatus according to the first embodiment of this invention, taken along a line 2-2 in Fig. 1; Fig. 3 is a sectional view of a gear transmission apparatus according to a second embodiment of this invention; Referring to Fig. 1, description will be made as regards a gear transmission apparatus according to a first embodiment of this invention. The gear transmission apparatus is assembled into an accessory-side belt wheel (driven pulley) of a belt drive device for transmitting a rotation drive force of an engine to accessory units (such as an alternator and a compressor) in a vehicle. In the following description, leftward and rightward directions correspond to leftward and rightward directions shown in Fig. 1, respectively. Components with no reference numerals are not illustrated in the figure. Referring to Fig. 1, a driven pulley 1 comprises a pulley 3, an electromagnetic clutch 5, and a gear transmission 7 according to the first embodiment. The pulley 3 has a hollow portion 4 of a U-shaped section. An inner peripheral surface of the pulley 3 is supported through bearings 9 and 9 on an outer peripheral surface of a boss 13 of a casing 11. The pulley 3 is coupled to an engine-side belt wheel (drive pulley) through a belt received in a V-shaped groove 15 of the pulley 3 and is put into rotation by a driving force of an engine. The casing 11 is fixed to a casing 19 of an accessory unit 17 by means of bolts 21. Inside the boss 13, an input shaft 23 is stably supported through bearings 25 and 27 with a wide span given between the bearings 25 and 27. A flange member 29 is spline-coupled to a left end of input shaft 23 and is prevented by a nut 31 from being removed. An armature 33 of a ring shape is arranged around an outer periphery of the flange member 29. A disc spring 37 is fastened by a rivet 35 to the armature 33 and the flange member 29 to couple the armature 33 and the flange member 29. An electromagnet 39 of a ring shape is received in the hollow portion 4 of the pulley 3 and is supported through a supporting member 41 fastened to the casing 11 by a bolt 43. Thus, an electromagnetic clutch is formed. When the electromagnet 39 is supplied with a coil current, the disc spring 37 is bent by an attractive force of the electromagnet 39. Consequently, the armature 33 is pressed against the pulley 3 to couple the electromagnetic clutch 5. The rotation drive force of the engine is then transmitted to the input shaft 23. When the coil current is stopped, the armature 33 is forced by an urging force of the disc spring 37 to be returned leftwards in the figure. Thus, the electromagnetic clutch 5 is released to disconnect the input shaft 23 from the engine. A hollow output shaft 45 is arranged at the right side in the figure of the input shaft 23 to be coaxial with the input shaft 23. A boss 47 is spline-coupled to an inner peripheral surface of the output shaft 45. An input shaft 49 of the accessory unit 17 is connected to the boss 47 through a Woodruff key 51 and is prevented by a bolt 53 from being removed. A one-way clutch 55 is interposed between the input shaft 23 and the output shaft 45. A planetary gear mechanism 57 is arranged at the right side of the electromagnetic clutch 5. The planetary gear mechanism 57 comprises an internal gear 59, an outer pinion gear 61, an inner pinion gear 63, and a sun gear 65 which are engaged one to another in a sequential fashion. The outer pinion gear 61 is engaged with the internal gear 59 and the inner pinion gear 63. The inner pinion gear 63 is engaged with the outer pinion gear 61 and the sun gear 65. Each of the pinion gears 61 and 63 is supported through a bearing 69 on a pinion shaft 67. The pinion shaft 67 has opposite ends supported by left and right pinion carriers 71 and 73, respectively. The internal gear 59 is integral with a right end of the input shaft 23. The right pinion carrier 73 is supported on the casing 11 through a bearing 75. The sun gear 65 is formed on the output shaft 45. A left end of the output shaft 45 is supported by the input shaft 45 through a bearing 77 while a right end of the output shaft 45 is supported by the right pinion carrier 73 through a bearing 79. A bearing 81 is interposed between the left pinion carrier 71 and the input shaft 23 to prevent the sliding movement in the axial direction. An overhang portion 83 is welded to the pinion carrier 73 and extends along an outer periphery of the internal gear 59. A bush (bearing) 85 is arranged between the overhang portion 83 and the internal gear 59. Thus, a free end (the overhang portion 83) of the pinion carrier 73 is received on the internal gear 59 stably supported as described above and is exactly centered. The sun gear 65 is stably supported because the sun gear 65 is held against the internal gear 59 and the pinion carrier 73 both of which are stably supported. A band 87 of a band brake is arranged at an outer periphery of the overhang portion 83. The band 87 is for tightly clamping the outer periphery of the overhang portion 83 to lock the rotation of the pinion carriers 71 and 73. Thus, the planetary gear mechanism 57 is put into a speed-change state. Oil is enclosed in the casing 11. Seals 89 and 91 are inserted between the casing 11 11 and the flange member 29 and between the casing 11 11 and the output shaft 45, respectively, to prevent oil leakage. Accordingly, good lubrication is assured in engagement portions between the bearings and the gears in the casing 11. This improves durability of the gear transmission. The oil is supplied through an oil passage 93 also to the bush 85. Thus, the gear transmission 7 is formed. Fig. 2 is a sectional view, taken along a line 2-2 in Fig. 1, for describing an example of the band brake. The band 87 extends along the outer periphery of the overhang portion 83 forming a drum portion of the band brake. One end of the band 87 is fixed to the casing 11 11 through a pin 97. Other end of the band 87 is connected through a pin 99 to one end of a link rod 101. The link rod 101 is supported by the casing 11 to be movable along the axial direction. Other end of the link rod 101 is supported through a pin 103 by one end of a bell crank 105. The bell crank 105 is supported on the casing 11 to be rotatable around a center 107. Other end of the bell crank 105 is connected through a pin 109 to a wire 111. The wire 111 is connected to a motor. In the band brake, when the wire 111 is pulled by the motor, the bell crank 105 is rotated around the center 107 to pull the link rod 101 along its axial direction. When the link rod 101 is moved along the axial direction, the band 87 is pulled to tightly clamp the overhang portion 83. The rotation of the pinion carrier 73 is braked by frictional contact between the band 87 and the overhang portion 83. In Fig. 2, a needle roller bearing 113 is used instead of the bush 85 in Fig. 1. Other structure is similar to that illustrated in Fig. 1. Accordingly, the similar parts are designated by like reference numerals. When the rotation of the pinion carriers 71 and 73 are locked by the band brake, the rotation of the engine supplied to the input shaft 23 (internal gear 59) is increased in speed and transmitted to the output shaft 45 (sun gear 65) to rotate the accessory unit 17. The one-way clutch 55 is arranged so as to allow the rotation in this situation. When the band brake is released, the pinion carriers 71 and 73 are put into a rotation-free state. In this event, the rotation of the input shaft 23 is kept unchanged in speed and transmitted through the one-way clutch 55 to the output shaft 45. Unlike the conventional apparatus, the electromagnetic clutch for speed-change operation is not arranged at the side surface. In addition, braking operation is carried out by the overhang portion 83 formed at the outer periphery of the apparatus. In this connection, the gear transmission 7 is considerably reduced in size along the axial direction. As described above, the pinion carriers 71 and 73 or brake-side members, the internal gear 59, and the sun gear 65 are all stably supported. Accordingly, good engagement is established between the gears. As a consequence, engagement noise, vibration, and damage of the gears are avoided. Thus, gear noise is very small. In addition, any noise transmitted to the casing 11 11 is reduced by a shut-off effect of the overhang portion 83. Furthermore, the casing 11 11 surrounding the gear transmission 7 also has a noise shut-off effect. As a result, operation noise is quiet. The overhang portion may be formed on the sun gear. The overhang portion may be supported between the casing 11. Fig. 3 is a partial sectional view of a gear transmission apparatus according to a second embodiment of this invention. In this embodiment, an overhang portion 119 is formed on the sun gear 69. The input shaft 145 is provided with the pinion carriers 71 and 73 in a rotationally integral fashion. The pinion carriers 71 and 73 are supported through bearings 121 and 121 in the axial direction. The sun gear 65 has a boss 122 which is supported by the input shaft 145 through a bearing 117. On the other hand, the sun gear 65 has an axial support 123 supported on the casing 11 through a bearing 75. An extending portion 125 extends from the sun gear 65 in a radially outward direction. The overhang portion 119 is integrally formed on the extending portion 125. In this embodiment, the rotation of the sun gear 65 is braked by frictional contact between the band 87 of the band brake and the overhang portion 119. As a result, the rotation of the output shaft 123 is increased in speed through the pinion gear 63 and transmitted to the input shaft 145.

Claims: A gear transmission apparatus comprising: a planetary gear mechanism (57) having an internal gear (59), a plurality of pinion gears (61, 63) meshing with said internal gear, a pinion carrier (71, 73) for carrying said pinion gears rotatably, and a sun gear (65) meshing with said pinion gears; a rotation input shaft (23) rotationally integral with one of said internal gear, said pinion carrier, and said sun gear; a rotation output shaft (45) rotationally integral with one of said internal gear, said pinion carrier, and said sun gear that is not rotationally integral with said rotation input shaft; a braking mechanism including a band brake (87, 83) for braking rotation of one of said internal gear, said pinion carrier, and said sun gear that is not rotationally integral with said rotation input shaft and said rotation output shaft; and a one-way clutch (55) interposed between said rotation input shaft and said rotation output shaft so as to allow rotation of said rotation output shaft in a speed-increase direction, characterized in that said band brake (87) is arranged radially outwardly of an overhang portion (83, 119) which is connected to one of said pinion carrier and sun gear for braking rotation thereof when brought in frictional contact with said overhang portion (83, 119), said overhang portion (83, 119) extending along the outer periphery of said internal gear and being rotatably supported on said outer periphery. A gear transmission apparatus as claimed in claim 1, wherein: said pinion gears comprise an outer pinion gear (61) meshing with said internal gear and an inner pinion gear (63) meshing with said outer pinion gear and said sun gear; said pinion carrier has said overhang portion (83); said band brake (87) brakes rotation of said pinion carrier (71, 73); and wherein said overhang portion (83) is rotatably supported through a bearing (85; 113) by said internal gear (59). A gear transmission apparatus as claimed in claim 2, wherein: the rotation input shaft (23) is rotationally integral with said internal gear (59); and the rotation output shaft (45) is rotationally integral with said sun gear (65). A gear transmission apparatus as claimed in claim 2 or 3, wherein: said rotation output shaft (45) is rotatably supported through a bearing by said rotation input shaft (23) and rotatably supported through a bearing by said pinion carrier. A gear transmission apparatus as claimed in one of claims 1 to 4, further comprising: a casing (11) containing said planetary gear mechanism (57), said rotation input shaft (23), said rotation output shaft (45), said band brake (87), and said one-way clutch (55), said casing rotatably supporting said rotation output shaft through a bearing and rotatably supporting said pinion carrier through a bearing. A gear transmission apparatus as claimed in claim 1, wherein: said pinion gears comprise an outer pinion gear (61) meshing with said internal gear and an inner pinion gear (63) meshing with said outer pinion gear and said sun gear; said sun gear (65) has said overhang portion (119); said band brake (87) brakes rotation of said sun gear (65); and wherein said overhang portion (119) is rotatably supported through a bearing (85; 113) by said internal gear (59). A gear transmission apparatus as claimed in claim 6, wherein: the rotation output shaft (123) is rotationally integral with said internal gear (59); and the rotation input shaft (145) is rotationally integral with said pinion carrier (71, 73). A gear transmission apparatus as claimed in claim 6 or 7, wherein: said rotation output shaft is rotatably supported through a bearing (77) by said rotation input shaft and rotatably supported through a bearing (117) by said sun gear (65). A gear transmission apparatus as claimed in claim 1 or in one of claims 6 to 8, further comprising: a casing (11) containing said planetary gear mechanism, said rotation input shaft, said rotation output shaft, said band brake, and said one-way clutch, said casing rotatably supporting said rotation output shaft (123) through a bearing (27) and rotatably supporting said sun gear through a bearing (75).

Inventors: TERAOKA MASAO, TERAOKA, MASAO, TERAOKA, MASAO, C/O TOCHIGIFUJISANGYO K.K.
Applicants: TOCHIGI FUJI SANGYO KK, TOCHIGIFUJISANGYO KABUSHIKI KAISHA
Application year: 1992
Main classification: F16H3
IPC codes: F16H3, F02B67