EP0072990A1 — Four-wheel vehicle drive system

Claim 1

Independent Claim 359 words

A four-wheel drive system for a vehicle with first and second pairs of road wheels, comprising a power unit having an output shaft rotatable about an axis in a lateral direction of the vehicle; a power transmission gear unit including transmission input and output shafts each having an axis of rotation parallel with an extension of the axis of rotation of the output shaft of said power unit; a final reduction gear rotatable about an axis parallel with the respective axes of rotation of the transmission input and output shafts, the transmission output shaft being held in driving engagement with said final reduction gear; a gear housing rotatable with said final reduction gear about the axis of rotation of the final reduction gear; a main transaxle gear casing having enclosed therein said transmission gear unit, said final reduction gear and said gear housing; and a differential gear assembly operative to transmit driving power to the first pair of road wheels, characterized by an auxiliary transaxle gear casing (27) secured to said main transaxle gear casing (6); a first wheel drive gear unit (4) comprising power splitting gear means (54,55) operative to split the driving power from said final reduction gear (25) into two power components and said differential gear assembly (38) to which one of said two power components is transmitted, said power splitting means (54,55) and said differential gear assembly (38) being enclosed within said auxiliary transaxle gear casing (27); a second wheel drive gear unit (5) enclosed within said auxiliary transaxle gear casing (27) and operative to transmit therethrough the other of said power components in a fore-and-aft direction of the vehicle for transmitting the power component to the second pair of road wheels (75,75'), said power splitting gear means (54,55) operatively intervening between said final reduction gear (25) and said second wheel drive gear unit (5); and low-and-high speed shifting means (26,48) operative to transfer driving power from the final reduction gear (25) to the differential gear assembly (38) selectively with two different gear ratios, the low-and-high speed shifting means (26,48) including a low-and-high speed shift gear assembly (26) enclosed within said rotatable gear housing (28).

Claim 2

Dependent Claim 359 words

A four-wheel drive system for a vehicle with first and second pairs of road wheels, comprising a power unit having an output shaft rotatable about an axis in a lateral direction of the vehicle; a power transmission gear unit including transmission input and output shafts each having an axis of rotation parallel with an extension of the axis of rotation of the output shaft of said power unit; a final reduction gear rotatable about an axis parallel with the respective axes of rotation of the transmission input and output shafts, the transmission output shaft being held in driving engagement with said final reduction gear; a gear housing rotatable with said final reduction gear about the axis of rotation of the final reduction gear; a main transaxle gear casing having enclosed therein said transmission gear unit, said final reduction gear and said gear housing; and a differential gear assembly operative to transmit driving power to the first pair of road wheels, characterized by an auxiliary transaxle gear casing (27) secured to said main transaxle gear casing (6); a first wheel drive gear unit (4) comprising power splitting gear means (54,55) operative to split the driving power from said final reduction gear (25) into two power components and said differential gear assembly (38) to which one of said two power components is transmitted, said power splitting means (54,55) and said differential gear assembly (38) being enclosed within said auxiliary transaxle gear casing (27); a second wheel drive gear unit (5) enclosed within said auxiliary transaxle gear casing (27) and operative to transmit therethrough the other of said power components in a fore-and-aft direction of the vehicle for transmitting the power component to the second pair of road wheels (75,75'), said power splitting gear means (54,55) operatively intervening between said final reduction gear (25) and said second wheel drive gear unit (5); and low-and-high speed shifting means (26,48) operative to transfer driving power from the final reduction gear (25) to the differential gear assembly (38) selectively with two different gear ratios, the low-and-high speed shifting means (26,48) including a low-and-high speed shift gear assembly (26) enclosed within said rotatable gear housing (28).

Claim 3

Dependent Claim 125 words

A four-wheel drive system as set forth in claim 1, characterized in that the differential gear assembly (38) of said first wheel drive gear unit (4) comprises a pair of rotatable output members (43,43') which have respective axes of rotation substantially aligned with each other and through which one of said two power components is to be transmitted to said first pair of road wheels (46, 46'), said low-and-high speed shift gear assembly (26) comprising power input and output members (31,35,30) rotatable about a common axis substantially aligned with the axis of rotation of the output members (43,43') of said differential gear assembly (38), a power input member (31) of the low-and-high speed shift gear assembly (26) being rotatable with said final reduction gear (25).

Claim 4

Dependent Claim 161 words

A four-wheel drive system as set forth in claim 1, characterized in that the differential gear assembly (38) of said first wheel drive gear unit (4) comprises a rotatable input member (39) and a pair of rotatable output members (43,43') which have respective axes of rotation substantially aligned with each other and through which one of said power components is to be transmitted to said first pair of road wheels (46,46'), said low-and-high speed shifting means (26,48) comprising a constant power input member (31) rotatable with said final reduction gear (25), a constant power output member (35) rotatable with the input member (39) of said differential gear assembly (38) and a lockable power output member (30) engageable with said auxiliary transaxle gear casing (27), the input and output members (31,35,30) of the low-and-high speed shift gear assembly (26) being rotatable about a common axis aligned with the axis of rotation of the output members (43,43') of said differential gear assembly (38).

Claim 5

Dependent Claim 147 words

A four-wheel drive system as set forth in claim 3, characterized in that the constant input member (31) of said low-and-high speed shift gear assembly (26) is held in driving engagement with the constant and lockable power output members (35,30) of said low-and-high speed shift gear assembly (26) and that said low-and-high speed shifting means further comprises a low-and-high speed shift control assembly (48) enclosed within said auxiliary transaxle gear casing (27) and comprising a first clutch member (50) locked with respect to the auxiliary transaxle gear casing (27), a second clutch member (51) rotatable with the constant output member (35) of the low-and-high speed shift gear assembly (26) and with the input member (39) of said differential gear assembly (38), and a coupling sleeve (52) rotatable with the lockable output member (30) and axially movable selectively into engagement with the first and second clutch members (50,51).

Claim 6

Dependent Claim 71 words

A four-wheel drive system as set forth in claim 4, characterized in that said first and second clutch members (50,51) have their respective axes commonly aligned with the axis of rotation of said final reduction gear (25) and that said coupling sleeve (52) is axially movable selectively into engagement with the first and second clutch members (50,51) in a direction parallel with the axis of the first and second clutch members.

Claim 7

Dependent Claim 199 words

A four-wheel drive system as set forth in claim 3, 4 or 5, characterized in that the power input and output members of said low-and-high speed shift gear assembly (26) form part of a planetary gear assembly which comprises a sun gear (30) rotatable about an axis substantially aligned with the axis of rotation of said final reduction gear (25) and constituting one of the input and output members of the low-and-high speed shift gear assembly (26), a ring gear (31) rotatable about the axis of rotation of the sun gear (30) and constituted by one of the remaining two of the input and output members of the low-and-high speed shift gear assembly (26), planet pinions (32) each held in mesh with the sun gear (30) and ring gear (31) and rotatable about an axis substantially parallel with the common axis of rotatation of the sun and ring gears (30,31), and a pinion carrier (35) connecting said planet pinions (32) together and rotatable about the common axis of rotation of the sun gear (30) and the ring gear (31) and constituted by the remaining one of the input and output members of the low-and-high speed shift gear assembly (26).

Claim 8

Dependent Claim 107 words

A four-wheel drive system as set forth in claim 2, 3, 4 or 5, characterized by a driveline (69, 70,73,73') intervening between said second wheel drive gear unit (5) and said second pair of road wheels (75,75') and adapted to be driven by the driving power component transmitted to the second wheel drive gear unit (5) through the power splitting gear means (54,55), said second wheel drive gear unit (5) comprising right-angle power transfer means (63) intervening between said power splitting means (54,55) and said driveline and operative to transmit said other of the two driving power components from said power splitting means (54,55) to the driveline.

Claim 9

Dependent Claim 97 words

A four-wheel drive system as set forth in claim 7, characterized in that said power splitting means comprises a first power transfer gear (54) rotatable with the input member (39) of said differential gear assembly (38) about an axis substantially aligned with the axis of rotation of said power input and output members of the low-and-high speed shift gear assembly (26) and a second power transfer gear (55) held in mesh with the first power transfer gear (54) and rotatable about an axis substantially parallel with the axis of rotation of said first power transfer gear (54).

Claim 10

Dependent Claim 53 words

A four-wheel drive system as set forth in claim 7, characterized in that said second wheel-drive gear unit (5) comprises two-wheel/four-wheel drive gear means (58) intervening between said power splitting means (54,55) and said driveline and operative to selectively provide and interrupt driving connection from the power splitting means (54,55) to the driveline.

Claim 11

Dependent Claim 83 words

A four-wheel drive system as set forth in claim 9, characterized in that said right-angle power transfer means (36) comprises a driving bevel gear (64) rotatable about an axis in a lateral direction of the vehicle, and a driven gear (65) rotatable about an axis in a fore-and-aft direction of the vehicle and held in mesh with said driving bevel gear (64), said power splitting means (54,55) being drivingly engageable with said driving bevel gear (64) through said two-wheel/four-wheel drive gear means (58).

Claim 12

Dependent Claim 150 words

A four wheel drive system as set forth in claim 10, characterized in that said power splitting means comprises a first power transfer gear (54) rotatable with the input member (39) of said differential gear assembly (38) about an axis substantially aligned with the axis of rotation of said power input and output members of said low-and-high speed shift gear assembly (26), a power transfer gear shaft (56) rotatable about an axis substantially parallel with the axis of rotation of said first power transfer gear (54), and a second power transfer gear (55) held in mesh with the first power transfer gear (54) and rotatable on said power transfer gear shaft (56), said second power transfer gear (55) being drivingly engageable with said power transfer gear shaft (56) through said two-wheel/four-wheel drive gear means (58) and said driving bevel gear (64) being rotatable with said power transfer gear shaft (56).

Claim 13

Dependent Claim 87 words

A four-wheel drive system as set forth in claim 11, characterized in that said two-wheel/four-wheel shift gear means (58) comprises a first clutch member (59) rotatable with said power transfer gear shaft (56), a second clutch member (60) rotatable with said second power transfer gear (55) on said power transfer gear shaft (56), and a coupling sleeve (61) axially movable on one of said first and second clutch members (69,60) selectively into and out of engagement with the other of the first and second clutch members (59,60).

Four-wheel vehicle drive system

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