Gear housing for accommodating a toroidal continously variable transmission

Abstract: A gear noise free toroidal continuously variable transmission (10) is disclosed wherein in order to suppress occurrence of gear noise, a gear train (30, 36) is accommodated in a gear housing (14) which includes a first housing part (18A) fixedly secured to a transmission casing (14) and a second housing part (18B) fixedly secured to the first housing part (18A) to form a dual-walled structure.

Description: BACKGROUND OF THE INVENTION The present invention relates to a toroidal continuously variable transmission, and more particularly to a gear housing for accommodating a gear train of the toroidal continuously variable transmission. A so-called double cavity toroidal continuously variable transmission is known according to a publication "A Continuously Variable Transmission for Automotive Fuel Economy" SAE (Society of Automotive Engineers Inc.) Paper 751180, see Fig. 7 thereof. United States Patent No. 4,928,542 issued on May 29, 1990 contains the same subject-matter as JP-A 121 6158 which is published on August 30, 1989 and from which is known a transmission according to the preamble of claim 1 showing a double cavity toroidal continuously variable transmission. This transmission includes a gear train for transmitting a rotary motion of two output discs to an intermediate shaft. The gear train includes an output gear splined to both of the output discs, and a drive gear splined to the intermediate shaft. The output gear meshes the drive gear. The gear train is disposed between the output discs and supported by a gear housing which is also disposed between the output discs. The gear housing includes a first housing part fixedly secured to a transmission casing and a second housing part fixedly secured to the first housing part. The first and second housing parts extend to cover the opposite axial end faces of the output gear and formed with bearing supports for the output gear. The first housing part extends further to cover one axial end face of the drive gear and is formed with a bearing support for the drive gear, but the second housing part does not further extend to cover the opposite axial end face of the drive gear. This structure of the gear housing is found to be not satisfactory in that it is difficult to sustain torque stress imparted to the drive gear, causing occurrence of gear noise between the output and drive gears. An object of the present invention is to improve a toroidal continuously variable transmission such that occurrence of gear noise derived from a gear train is suppressed. SUMMARY OF THE INVENTION According to the present invention, a toroidal continuously variable transmission comprises a gear a gear housing, and a gear train within the gear train. The gear housing includes a first housing part and a second housing part fixedly secured to the first housing part to form a dual-walled structure. According to the present invention to solve this object, there is provided a toroidal continuously variable transmission as defined by the features of claim 1. Preferred embodiments of the invention are the subject-matter of the sub claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a fragmentary diagrammatic section of a toroidal continuously variable transmission; and Fig. 2 is a cross section taken through the line II-II in Fig. 1 illustrating an end elevation of a gear housing with unnecessary parts removed. DETAILED DESCRIPTION OF THE INVENTION Referring to the accompanying drawings, and particularly to Fig. 1, a toroidal continuously variable transmission is generally designated by the reference numeral 10 and comprises an input shaft 12 rotatably supported by a transmission casing 14. The toroidal continuously variable transmission 10 includes a first toroidal change-speed mechanism 20 and a second toroidal change-speed mechanism 20a. The first toroidal change-speed mechanism 20 has a first set of coaxial input and output discs 22 and 24 having facing toric surfaces and a plurality of friction rollers, not shown, disposed between and in driving contact with the toric surfaces for transmitting tlorque between the input and output discs 22 and 24. Similarly, the second toroidal change-speed mechanism 20a has a second set of coaxial input and output discs 22a and 24a having facing toric surfaces and a plurality of friction rollers, not shown, disposed between and in driving contact with the toric surfaces for transmitting torque between the input and output discs 22a and 24a. As shown in Fig. 1, with the output discs 24 and 24a adjacent to each other, the two sets of coaxial input and output discs 22 and 24, and 22a and 24a are mounted on the input shaft 12. The input discs 22 and 22a are mounted on the input shaft 12 by ball splines 26 and 26a, respectively, for rotation and limited axial movement relative to the input shaft 11. The output discs 24 and 24a are rotatably supported on the input shaft 12 by needle bearings 28 and 28a, respectively. Between the output discs 24 and 24a is disposed an output gear 30 rotatable about the input shaft 12 and in driving connection with both of the output discs 24 and 24a by spline connections, not shown. For transmitting a rotary motion from the input shaft 12 to the input discs 22 and 22a, a loading cam 32 is operatively disposed between the input shaft 12 and the input disc 22, and a bellevile spring 34 between the input disc 22a and the input shaft 12. For transmitting a rotary motion of the output discs 24 and 24a to an intermedaite shaft 38, the output gear 30 meshes a drive gear 36 splined to the intermediate shaft 38. The output gear 30 and drive gear 36 cooperate with each other to form a gear train 40. The rotary motion of the intermediate shaft 38 is transmitted to an output shaft 46 via a counter gear 42 splined to the intermediate shaft 38, an idler gear, not shown, and a main gear 44 of the output shaft 46. The bottom of the transmission casing 14 is closed by an oil pan 60. The oil pan 60 is of a dual-walled structure including an inner pan 62 and an outer pan 64. Between the inner and outer oil pans 62 and 64 is defined a passage through which a cooling water for cooling lubricant oil flows. The inner pan 62 is made of an aluminium which exibits a good thermal conductivity and which is less susceptible to oxidation owing to contact with a traction oil used as the lubricant oil, while the outer pan 64 is made of a steel plate with a high rigidity. Disposed between the outermost portion of the inner oil pan 62 and the adjacent portion of the transmission casing 14 and between the outermost portion of the inner oil pan 62 and the adjacent outermost portion of the outer oil pan 64 are gaskets 66 for filling small gaps created owing to a difference in heat expansion between the materials which the inner and outer pans 62 and 64 are made of. Although not shown, a cooling water admission port is disposed near an oil inlet port of an oil suction pipe, and a cooling water discharge port is arranged remote from the oil inlet port. Referring to Fig. 1, the gear train 40 is accommodated in and covered by a dual-walled gear housing 18 which is disposed between the output discs 24 and 24a. As best seen in Fig. 2, the transmission casing 14 has inwardly projecting lateral extensions 14a and 14b, and an inwardly projecting top extension 14c. The gear housing 18 includes a first or main housing part 18a, and a second or cover housing part 18b. The first housing part 18a includes a generally circular portion having an annular attachment area fixedly secured to the inwardly projecting lateral extensions 14a and 14b and to the inwardly projecting top extension 14c by six bolts 100. The first housing part 18a also includes a skirt portion downwardy extending from the circular portion thereof. The second housing part 18b has substantially the same configuration as the first housing part 18a as viewed in Fig. 2. Thus, the second housing part 18b includes a generally circular portion and a skirt portion downwardly extending from the circular portion thereof. However, the circular portion of the second housing part 18b is different from that of the first housing part 18a in that an attachment area is not continuous and formed with cutouts to allow extension of the inwardly projecting lateral and top extensions 14a, 14b, and 14c of the transmission casing 14, leaving circumferentially-spaced attachment area zones. The second housing part 18b is fixedly secured to the first housing part 18a by eight bolts 48. All of these bolts 48 are screwed into the correcponding bolt holes from the first housing part 18a. However, the bottom two bolts 48′ are screwed into the corresponding bolt holes from the second housing part 18b (see Fig. 1 also). In order to facilitate adjusting of the bolts 100, 48, and 48′ with the corresponding bolt holes, the first housing part 18a is formed with, two pin holes for receiving two locate pins 200, respectively. As shown in Fig. 1, the first and second housing parts 18a and 18b are formed with bearing supports for ball bearings 50 and 50a, respectively, by which the output gear 30 is rotatably supported on the gear housing 18. The first housing part 18a is formed also with a bearing support for roller bearing 52 by which the drive gear 36 is rotatably supported on the gear housing 18. In order to strengthen the bottom of the skirt portions of the first and second housing parts 18a and 18b, a gusset or bracket 54 is fixedly secured to the second housing part 18b at the bottom of the skirt portion by the two bolts 48′ and also secured to a rigid member fixedly secured to the transmission casing. In this embodiment the rigid member is a control valve assembly 56. From the previous description of the embodiment according to the present invention, it will now be appreciated that the gear housing 18 is of the dual-walled structure and thus provides increased rigid bearing supports for the gear train 40, thus effectively suppressing occurrence of noise derived from between the output and drive gears 30 and 36. Owing to the gusset 54, the rigidity of the bottom portion of the gear housing has a remarkably increased. Owing to the structure of the gear housing 18 described above, the wall portions of the housing parts 18a and 18b may be redcued in thickness. Thus, occurrence of gear noise is suppressed without any substantial increase in weight. Lastly, the gear housing 18 encloses the gear train 40 to confine noise derived from the gear train 40 therein, thus preventing transmission of gear noise outwardly.

Claims: A toroidal consinuously variable transmission comprising: a transmission casing (14); coaxial input and output discs (22, 24; 22a, 24a) having facing toric surfaces; a gear housing (18) disposed within and fixedly secured to said transmission casing; and a gear train (40) within said gear housing and including an output gear (30) in driving connection with said output discs and a drive gear (36) meshing with said output gear (30) and splined to an intermediate shaft (38); said gear housing (18) including a first housing part (18a) and a second housing part (18b) secured to said first housing part (18a), said first and second housing parts (18, 18a) being formed with bearing supports for bearings (50, 50a), respectively, rotatably supporting said output gear (30), said first housing part (18a) having a first skirt portion formed with a bearing support for a bearing (52) rotatably supporting said drive gear (36), characterized in that said first and second housing parts (18a, 18b) enclose said gear train (40) to form a dual-walled structure and to confine noise derived from said gear train (40); said second housing part (18b) including a second skirt portion fixedly secured to said first skirt portion at portions adjacent their outer periphery and rigidly secured to a rigid member (56) fixed to the transmission casing (14). A toroidal continuously variable transmission as claimed in claim 1, characterized in that said rigid member is in the form of a control valve assembly (56). A toroidal continously variable transmission as claimed in claim 1 or 2, characterized in that said first and second skirt portions are fixedly secured by means of bolts (48). A toroidal continuously variable transmission as claimed in claim 1 or 2, characterized in that said second housing part (18b) includes a bracket (54) with which said second skirt portion is fixed to said rigid member (56).

Inventors: NAKANO MASAKI, NAKANO, MASAKI
Applicants: NISSAN MOTOR, NISSAN MOTOR CO., LTD.
Application year: 1990
Main classification: F16H15
IPC codes: F16H37, F16H57, F16H15