Continuously variable transmission

Abstract

In a continuously variable transmission, driving force from a drive source is transmitted via a path to establish a LOW mode. A large torque that is transmitted in the LOW mode passes through a first output switching mechanism. Since a countershaft is relatively rotatably disposed on an outer periphery of an input shaft, and the first output switching mechanism is disposed on the countershaft, the countershaft which transmits a large torque is disposed on an outer peripheral side of a double tube and supported directly by a transmission case, and the input shaft which transmits a relatively small torque is supported via the countershaft, thereby making it possible to support the first output switching mechanism with high rigidity without carrying out special reinforcement.

Claims

1. A continuously variable transmission comprising: an input shaft into which driving force from a drive source is inputted; a belt type continuously variable transmission mechanism that is formed from a first pulley, a second pulley, and an endless belt; an output shaft that outputs the driving force whose speed has been changed by the belt type continuously variable transmission mechanism; a first input path that transmits the driving force from the drive source to the first pulley; a first input switching mechanism that switches the driving force from the drive source toward the first input path side; a speed decreasing mechanism that is disposed in the first input path and decreases the speed of an input to the first pulley; a second input path that transmits the driving force from the drive source to the second pulley; a second input switching mechanism that switches the driving force from the drive source (E) toward the second input path side; a speed increasing mechanism that is disposed in the second input path and increases the speed of an input to the second pulley; a first output path that outputs the driving force from the second pulley; a second output path that outputs the driving force from the first pulley, a first output switching mechanism that is disposed in the first output path and switches the driving force from the second pulley toward the output shaft side; and a second output switching mechanism that is disposed in the second output path and switches the driving force from the first pulley toward the output shaft side, the first pulley comprises a first fixed pulley and a first movable pulley, the second pulley comprises a second fixed pulley and a second movable pulley, the first fixed pulley and the second fixed pulley are disposed at mutually diagonal positions, the first movable pulley and the second movable pulley are disposed at mutually diagonal positions, the first input switching mechanism is disposed on the input shaft or on a rotating shaft on a rear face of the first movable pulley of the first pulley, the second input switching mechanism is disposed on a rotating shaft on a rear face of the second fixed pulley of the second pulley or on the input shaft, the first output switching mechanism is disposed on a countershaft relatively rotatably fitted around an outer periphery of the input shaft on the first output path, and the second output switching mechanism and the output shaft are disposed on a rotating shaft on a rear face of the first fixed pulley of the first pulley.

2. The continuously variable transmission according to claim 1, wherein the first output switching mechanism is formed from a dog clutch that can selectively join to the countershaft a first drive gear and a second drive gear relatively rotatably supported on the countershaft, the first drive gear is connected to a driven gear provided on the output shaft, and the second drive gear is connected to the driven gear provided on the output shaft via an idle shaft.

3. The continuously variable transmission according to claim 2, wherein the first output switching mechanism is disposed at a position in which part thereof overlaps the second output switching mechanism When viewed in a radial direction.

4. The continuously variable transmission according to claim 2, wherein when a gear ratio of the speed decreasing mechanism is i.sub.red, a gear ratio of the speed increasing mechanism is i.sub.ind, the minimum ratio of the first pulley and the second pulley is i.sub.min, and a gear ratio of the reduction gears disposed in the first output path is i.sub.sec, the relationship i.sub.redi.sub.min=i.sub.ind and the relationship i.sub.sec=i.sub.red/i.sub.ind hold.

5. The continuously variable transmission according to claim 1, wherein the first output switching mechanism is disposed at a position in which part thereof overlaps the second output switching mechanism when viewed in a radial direction.

6. The continuously variable transmission according to claim 5, wherein when a gear ratio of the speed decreasing mechanism is i.sub.red, a gear ratio of the speed increasing mechanism is i.sub.ind, the minimum ratio of the first pulley and the second pulley is i.sub.min, and a gear ratio of the reduction gears disposed in the first output path is i.sub.sec, the relationship i.sub.redi.sub.min=i.sub.ind and the relationship i.sub.sec=i.sub.red/i.sub.ind hold.

7. The continuously variable transmission according to claim 1, wherein when a gear ratio of the speed decreasing mechanism is i.sub.red, a gear ratio of the speed increasing mechanism is i.sub.ind, the minimum ratio of the first pulley and the second pulley is i.sub.min, and a gear ratio of the reduction gears disposed in the first output path is i.sub.sec, the relationship i.sub.redi.sub.min=i.sub.ind and the relationship i.sub.sec=i.sub.red/i.sub.ind hold.

Description

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a skeleton diagram of a continuously variable transmission. (first embodiment)

(2) FIG. 2 is a torque flow diagram of a LOW mode. (first embodiment)

(3) FIG. 3 is a torque flow diagram of transition mode 1. (first embodiment)

(4) FIG. 4 is a torque flow diagram of transition mode 2. (first embodiment)

(5) FIG. 5 is a torque flow diagram of a HI mode. (first embodiment)

(6) FIG. 6 is a torque flow diagram of a reverse mode. (first embodiment)

(7) FIG. 7 is a torque flow diagram of a directly coupled LOW mode. (first embodiment)

(8) FIG. 8 is a torque flow diagram of a directly coupled HI mode. (first embodiment)

(9) FIG. 9 is a diagram for explaining the transition between the LOW mode and the HI mode. (first embodiment)

(10) FIG. 10 is a diagram showing the relationship between overall gear ratio and gear ratio of a belt type continuously variable transmission mechanism. (first embodiment)

(11) FIG. 11 is a diagram for explaining the difference in overall gear ratio between the invention of the present application and a Comparative Example. (first embodiment)

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

(12) 13 Main input shaft (input shaft)

(13) 14 Countershaft

(14) 15 Output shaft

(15) 16 Idle shaft

(16) 20 Belt type continuously variable transmission mechanism

(17) 21 First pulley

(18) 21A First fixed pulley

(19) 21B First movable pulley

(20) 22 Second pulley

(21) 22A Second fixed pulley

(22) 22B Second movable pulley

(23) 23 Endless belt

(24) 24A LOW friction clutch (first input switching mechanism)

(25) 24B HI friction clutch (second input switching mechanism)

(26) 25 First reduction gear (speed decreasing mechanism)

(27) 26 Second reduction gear (speed decreasing mechanism)

(28) 27 First induction gear (speed increasing mechanism)

(29) 28 Second induction gear (speed increasing mechanism)

(30) 29 Fifth reduction gear (first drive gear or reduction gear)

(31) 30 Sixth reduction gear (driven gear or reduction (rear)

(32) 34 Reverse drive gear (second drive gear)

(33) 37 First output switching mechanism

(34) 38 Second output switching mechanism

(35) 39 Third reduction gear (reduction gear)

(36) 40 Fourth reduction gear (reduction gear)

(37) E Engine (drive source)

(38) IP1 First input path

(39) IP2 Second input path

(40) OP1 First output path

(41) OP2 Second output path

MODE FOR CARRYING OUT THE INVENTION

(42) An embodiment of the present invention is explained below by reference to FIG. 1 to FIG. 11.

(43) First Embodiment

(44) As shown in FIG. 1, a continuously variable transmission T mounted on a vehicle includes an input shaft 13 that is connected to a crankshaft 11 of an engine E via a torque converter 12, a first auxiliary input shaft 13A, a second auxiliary input shaft 13B, a countershaft 14, an output shaft 15, and an idle Shaft 16, which are disposed in parallel to the main input shaft 13, the tubular countershaft 14 is relatively rotatably fitted around the outer periphery of the main input shaft 13, and the tubular output shaft 15 is relatively rotatably fitted around the outer periphery of the first auxiliary input shaft 13A. The countershaft 14 is supported on a transmission case via bearings 17 and 17.

(45) A first reduction gear 25 relatively rotatably supported on the main input shaft 13 and a second reduction gear 26 fixedly provided on the first auxiliary input shaft 13A are meshed together, and the first reduction gear 25 can be joined to the main input shaft 13 via a LOW friction clutch 24A. Furthermore, a first induction gear 27 fixedly provided on the main input Shaft 13 and a second induction gear 28 relatively rotatably supported on the second auxiliary input shaft 13B are meshed together, and the second induction gear 28 can be joined to the second auxiliary input shaft 13B via a HI friction clutch 24B.

(46) A belt type continuously variable transmission mechanism 20 disposed between the first auxiliary input shaft 13A and the second auxiliary input shaft 13B includes a first pulley 21 provided on the first auxiliary input shaft 13A, a second pulley 22 provided on the second auxiliary input shaft 13B, and an endless belt 23 wound around the first and second pulleys 21 and 22. The groove widths of the first and second pulleys 21 and 22 are increased and decreased in opposite directions from each other by means of oil pressure, thus continuously changing the gear ratio between the first auxiliary input shaft 13A and the second auxiliary input shaft 13B. The first pulley 21 is formed from a first fixed pulley 21A fixed to the first auxiliary input shaft 13A, and a first movable pulley 21B that can move toward and away from the first fixed pulley 21A. Furthermore, the second pulley 22 is formed from a second fixed pulley 22A fixed to the second auxiliary input shaft 13B, and a second movable pulley 22B that can move toward and away from the second fixed pulley 22A.

(47) Furthermore, a third reduction gear 39 fixedly provided on the second input shaft 13B and a fourth reduction gear 40 fixedly provided on the countershaft 14 are meshed together, a fifth reduction gear 29 relatively rotatably supported on the countershaft 14 and a sixth reduction gear 30 fixedly provided on the output shaft 15 are meshed together, and a final drive gear 31 integral with the sixth reduction gear 30 and a final driven gear 32 provided on a differential gear 33 are meshed together. A reverse drive gear 34 relatively rotatably supported on the countershaft 14 and a reverse idle gear 35 fixedly provided on the idle shaft 16 are meshed together, and a reverse driven gear 36 fixedly provided on the idle shaft 16 meshes with the sixth reduction gear 30.

(48) A first output switching mechanism 37, which is a dog clutch, is provided on the outer periphery of the countershaft 14. The first output switching mechanism 37 can switch between a neutral position, a rightward-moved position, and a leftward-moved position; when moved rightward from the neutral position the fifth reduction gear 29 is joined to the countershaft 14, and when moved leftward from the neutral position the reverse drive gear 34 is joined to the countershaft 14. A second output switching mechanism 38, which is a dog clutch, is provided on the outer periphery of the first auxiliary input shaft 13A. The second output switching mechanism 38 can switch between a neutral position and a rightward-moved position, and when moved rightward from the neutral position the sixth reduction gear 30 and the final drive gear 31 are joined to the first auxiliary input shaft 13A.

(49) The first and second reduction gears 25 and 26 reduce the speed of rotation of the main input shaft 13 and transmit it to the first auxiliary input shaft 13A. On the other hand, the first and second induction gears 27 and 28 increase the speed of rotation of the main input shaft 13 and transmit it to the second auxiliary input shaft 13B. The first reduction gear 25 and the second reduction gear 26 form a first input path IP1 of the present invention, and the first induction gear 27 and the second induction gear 28 form a second input path IP2 of the present invention. The third reduction gear 39, the fourth reduction gear 40, the fifth reduction gear 29, and the sixth reduction gear 30 form a first output path OP1 of the present invention, and the first auxiliary input shaft 13A between the first pulley 21 and the second output switching mechanism 38 forms a second output path OP2 of the present invention.

(50) When the gear ratio from the first reduction gear 25 to the second reduction gear 26 is defined as i.sub.red, the gear ratio from the first induction gear 27 to the second induction gear 28 is defined as i.sub.ind, and the minimum gear ratio from the first pulley 21 to the second pulley 22 of the belt type continuously variable transmission mechanism 20 is defined as i.sub.min, the gear ratios are set so that i.sub.redi.sub.min=i.sub.ind. When the gear ratio from the third reduction gear 39 to the sixth reduction gear 30 via the fourth reduction gear 40 and the fifth reduction gear 29 is defined as i.sub.sec, the gear ratios are set so that i.sub.sec=i.sub.red/i.sub.ind.

(51) FIG. 2 shows a LOW mode of the continuously variable transmission T. In the LOW mode, the LOW friction clutch 24A is engaged, the HI friction clutch 24B is disengaged, the first output switching mechanism 37 is operated to the rightward-moved position (LOW position), and the second output switching mechanism 38 is operated to the neutral position.

(52) As a result, the driving force of the engine E is transmitted to the differential gear 33 via the path: crankshaft 11.fwdarw.torque converter 12.fwdarw.main input shaft 13.fwdarw.LOW friction clutch 24A.fwdarw.first reduction gear 25.fwdarw.second reduction gear 26.fwdarw.first auxiliary input shaft 13A.fwdarw.first pulley 21.fwdarw.endless belt 23.fwdarw.second pulley 22.fwdarw.second auxiliary input shaft 13B.fwdarw.third reduction gear 39.fwdarw.fourth reduction gear 40.fwdarw.countershaft 14.fwdarw.first output switching mechanism 37.fwdarw.fifth reduction gear 29.fwdarw.sixth reduction gear 30.fwdarw.output shaft 15.fwdarw.final drive gear 31.fwdarw.final driven gear 32.

(53) In the LOW mode the belt type continuously variable transmission mechanism 20 transmits the driving force from the first auxiliary input shaft 13A side to the second auxiliary input shaft 13B side, and according to the change in the gear ratio thereof the overall gear ratio of the continuously variable transmission T is changed.

(54) FIG. 3 shows a transition mode 1 as a first-half transition from the LOW mode to the HI mode, which is described later. In transition mode 1, the LOW friction clutch 24A is engaged, the HI friction clutch 24B is disengaged, the first output switching mechanism 37 is operated to the rightward-moved position (LOW position), the second output switching mechanism 38 is operated h the rightward-moved position (HI position), and the LOW mode and a directly coupled LOW mode (see FIG. 7), which is described later, are established at the same time.

(55) FIG. 4 shows a transition mode 2 as a second-half transition from the LOW mode to the HI mode, which is described later. In transition mode 2, the LOW friction clutch 24A is disengaged, the HI friction clutch 24B is engaged, the first output switching mechanism 37 is operated to the rightward-moved position (LOW position), the second output switching mechanism 38 is operated to the rightward-moved position (HI position), and the HI mode (see FIG. 5), which is described later, and a directly coupled HI mode (see FIG. 8), which is described later, are established at the same time.

(56) Transition mode 1 and transition mode 2 are for smoothly carrying out a transition from the LOW mode to the HI mode, and details thereof are described later.

(57) FIG. 5 shows the HI mode of the continuously variable transmission T. In the HI mode, the LOW friction clutch 24A is disengaged, the HI friction clutch 24B is engaged, the first output switching mechanism 37 is operated to the neutral position, and the second output switching mechanism 38 is operated to the rightward-moved position (HI position).

(58) As a result, the driving force of the engine E is transmitted to the differential gear 33 via the path: crankshaft 11.fwdarw.torque converter 12.fwdarw.main input shaft 13.fwdarw.first induction gear 27.fwdarw.second induction gear 28.fwdarw.HI friction clutch 24B.fwdarw.second auxiliary input shaft 13B.fwdarw.second pulley 22.fwdarw.endless belt 23.fwdarw.first pulley 21.fwdarw.first auxiliary input shaft 13A.fwdarw.second output switching mechanism 38.fwdarw.output shaft 15.fwdarw.final drive gear 31.fwdarw.final driven gear 32.

(59) In the HI mode, the belt type continuously variable transmission mechanism 20 transmits the driving force from the second auxiliary input shaft 13B side to the first auxiliary input shaft 13A side, and according to the change in the gear ratio thereof the overall gear ratio of the continuously variable transmission T is changed.

(60) FIG. 6 shows a reverse mode of the continuously variable transmission T. In the reverse mode, the LOW fiction clutch 24A is engaged, the HI friction clutch 24B is disengaged, the first output switching mechanism 37 is operated to the leftward-moved position (RVS position), and the second output switching mechanism 38 is operated to the neutral position.

(61) As a result, the driving force of the engine E is transmitted to the differential gear 33 as reverse rotation via the path: crankshaft 11.fwdarw.torque converter 12.fwdarw.main input shaft 13.fwdarw.LOW fiction clutch 24A.fwdarw.first reduction gear 25.fwdarw.second reduction gear 26.fwdarw.first auxiliary input shaft 13A.fwdarw.first pulley 21.fwdarw.endless belt 23.fwdarw.second pulley 22.fwdarw.second auxiliary input Shaft 13B.fwdarw.third reduction gear 39.fwdarw.fourth reduction gear 40.fwdarw.countershaft 14.fwdarw.first output switching mechanism 37.fwdarw.reverse drive gear 34.fwdarw.reverse idle gear 35.fwdarw.idle shaft 16.fwdarw.reverse driven gear 36.fwdarw.sixth reduction gear 30.fwdarw.output shaft 15.fwdarw.final drive gear 31.fwdarw.final driven gear 32.

(62) In the reverse mode, the belt type continuously variable transmission mechanism 20 transmits the driving force from the first auxiliary input shaft 13A side to the second auxiliary input shaft 13B side, and according to the change in the gear ratio thereof the overall gear ratio of the continuously variable transmission T is changed.

(63) FIG. 7 shows the directly coupled LOW mode of the continuously variable transmission T. In the directly coupled LOW mode, the LOW friction clutch 24A is engaged, the HI friction clutch 24B is disengaged, the first output switching mechanism 37 is operated to the neutral position, and the second output switching mechanism 38 is operated to the rightward-moved position (HI position).

(64) As a result, the driving force of the engine E is transmitted to the differential gear 33 via the path: crankshaft 11.fwdarw.torque converter 12.fwdarw.main input shaft 13.fwdarw.LOW friction clutch 24A.fwdarw.first reduction gear 25.fwdarw.second reduction gear 26.fwdarw.first auxiliary input shaft 13A.fwdarw.second output switching mechanism 38.fwdarw.output shaft 15.fwdarw.final drive gear 31.fwdarw.final driven gear 32.

(65) In the directly coupled LOW mode, the belt type continuously variable transmission mechanism 20 is not operated, and the overall gear ratio of the continuously variable transmission T is constant.

(66) FIG. 8 shows the directly coupled HI mode of the continuously variable transmission T. In the directly coupled HI mode, the LOW fiction clutch 24A is disengaged, the HI friction clutch 24B is engaged, the first output switching mechanism 37 is operated to the rightward-moved position (LOW position), and the second output switching mechanism 38 is operated to the neutral position.

(67) As a result, the driving force of the engine E is transmitted to the differential gear 33 via the path: crankshaft 11.fwdarw.torque converter 12.fwdarw.main input shaft 13.fwdarw.first induction gear 27.fwdarw.second induction gear 28.fwdarw.HI friction clutch 24B.fwdarw.second auxiliary input shaft 13B.fwdarw.third reduction gear 39.fwdarw.fourth reduction gear 40.fwdarw.countershaft 14.fwdarw.first output switching mechanism 37.fwdarw.fifth reduction gear 29.fwdarw.sixth reduction gear 30.fwdarw.output shaft 15.fwdarw.final drive gear 31.fwdarw.final driven gear 32.

(68) In the directly coupled HI mode, the belt type continuously variable transmission mechanism 20 is not operated, and the overall gear ratio of the continuously variable transmission T is constant.

(69) The operation at a time of transition from the LOW mode to the HI mode is now explained.

(70) As shown in FIG. 9, in the LOW mode shown in FIG. 2, when the gear ratio from the first pulley 21 to the second pulley 22 of the belt type continuously variable transmission mechanism 20 gradually decreases and attains the minimum gear ratio i.sub.min, the second output switching mechanism 38, which has until this time been in the neutral position, is operated to the rightward-moved position (HI position), thus attaining transition mode 1 shown in FIG. 3. Subsequently, the engagement relationship between the LOW friction clutch 24A and the HI friction clutch 24B is switched over to thus attain transition mode 2 shown in FIG. 4, and the first output switching mechanism 37, which has been in the rightward-moved position (LOW position), is then operated to the neutral position, thus attaining the HI mode shown in FIG. 5.

(71) At the end of the LOW mode and the beginning of the HI mode, the overall gear ratio of the continuously variable transmission T is the same, thereby preventing the occurrence of gear shift shock when switching from the LOW mode to the HI mode. It enables smooth operation of the first output switching mechanism 37, the second output switching mechanism 38, the LOW friction clutch 24A, and the HI friction clutch 24B by preventing the occurrence of differential rotation when the second output switching mechanism 38 is moved rightward to the HI position at a time of transition from the LOW mode to transition mode 1, when the LOW friction clutch 24A and the HI friction clutch 24B are interchangeably engaged at a time of transition from transition mode 1 to transition mode 2, and when the first output switching mechanism 37 moves leftward to the neutral position at a time of transition from transition mode 2 to the HI mode.

(72) In order to explain this in detail, assume that the gear ratio i.sub.red from the first reduction gear 25 to the second reduction gear 26 is 1.5, the gear ratio i.sub.ind from the first induction gear 27 to the second induction gear 28 is 0.75, the minimum gear ratio i.sub.min from the first pulley 21 to the second pulley 22 of the belt type continuously variable transmission mechanism 20 is 0.5, the gear ratio i.sub.sec from the third reduction gear 39 to the sixth reduction gear 30 via the fourth reduction gear 40 and the fifth reduction gear 29 is 2.0, and the rotational speed of the input shaft 13 is 1500 rpm.

(73) In the power transmission path of transition mode 1, the power transmission path of the LOW mode and the power transmission path of the directly coupled LOW mode coexist; in the power transmission path of the LOW mode, when the main input shaft 13 rotates at 1500 rpm, the first auxiliary input shaft 13A is reduced in speed at i.sub.red=1.5 to 1000 rpm by the first and second reduction gears 25 and 26, the second auxiliary input shaft 13B is increased in speed at i.sub.min=0.5 to 2000 rpm by the belt type continuously variable transmission mechanism 20, and the output shaft 15 is reduced in speed at i.sub.ind=2.0 by the third reduction gear 39, the fourth reduction gear 40, the fifth reduction gear 29, and the sixth reduction gear 30 and rotates at 1000 rpm. On the other hand, in the power transmission path of the directly coupled LOW mode, when the main input shaft 13 rotates at 1500 rpm, the first auxiliary input shaft 13A is reduced in speed at i.sub.red=1.5 to 1000 rpm by the first and second reduction gears 25 and 26, and the output shaft 15, which is directly coupled to the first auxiliary input shaft 13A, rotates at 1000 rpm.

(74) In the power transmission path of transition mode 2, the power transmission path of the HI mode and the power transmission path of the directly coupled HI coexist; in the power transmission path of the HI mode, when the main input shaft 13 rotates at 1500 rpm, the second auxiliary input shaft 13B is increased in speed at i.sub.ind=0.75 by the first and second induction gears 27 and 28 and attains 2000 rpm, the first auxiliary input shaft 13A is reduced in speed at 1/i.sub.min=2.0 by the belt type continuously variable transmission mechanism 20 and attains 1000 rpm, and the output shaft 15 directly coupled to the first auxiliary input shaft 13A rotates at 1000 rpm. On the other hand, in the power transmission path of the directly coupled HI mode, when the main input shaft 13 rotates at 1500 rpm, the second auxiliary input shaft 13B is increased in speed at i.sub.ind=0.75 by the first and second induction gears 27 and 28 and attains 2000 rpm, and the output shaft 15 is reduced in speed at i.sub.ind=2.0 by the third reduction gear 39, the fourth reduction gear 40, the fifth reduction gear 29, and the sixth reduction gear 30 and rotates at 1000 rpm.

(75) As described above, when shifting between the LOW mode, transition mode 1, transition mode 2, and the HI mode, the rotational speeds of the main input shaft 13, the first auxiliary input shaft 13A, the second auxiliary input shaft 13B, the countershaft 14, and the output shaft 15 do not change at all, the gear ratio of the belt type continuously variable transmission mechanism 20 is maintained at i.sub.min, and it is therefore possible to smoothly carry out operation of the first output switching mechanism 37, the second output switching mechanism 38, the LOW friction clutch 24A, and the HI friction clutch 24B in a state in which there is no differential rotation.

(76) Furthermore, at the time of transition from transition mode 1 to transition mode 2, the belt type continuously variable transmission mechanism 20 switches from the power transmission state of first pulley 21.fwdarw.second pulley 22 to the power transmission state of second pulley 22.fwdarw.first pulley 21, and there is an instant when torque transmission is temporarily interrupted. However, since at that instant the directly coupled LOW mode and the directly coupled HI mode are in existence to thus transmit torque, it is possible to prevent the occurrence of a shock due to interruption of torque transmission.

(77) As described above, in accordance with this embodiment, due to the belt type continuously variable transmission mechanism 20 being combined with the speed decreasing mechanism, which includes the first reduction gear 25, the second reduction gear 26, the third reduction gear 39, the fourth reduction gear 40, the fifth reduction gear 29, and the sixth reduction gear 30, and the speed increasing mechanism, which includes the first induction gear 27 and the second induction gear 28, as shown in FIG. 10, compared with a single belt type continuously variable transmission mechanism (overall gear ratio=about 6 to 7), the gear ratio on the LOW side and the gear ratio on the OD side are both increased, thus enabling an overall gear ratio as large as 10 or greater to be achieved (see FIG. 11). Furthermore, in the continuously variable transmission T of the present embodiment, the overall gear ratio when the gear ratio of the belt type continuously variable transmission mechanism 20 is 1.0 is a value close to the overall gear ratio at the OD end of the single belt type continuously variable transmission mechanism, and it can be seen that the effect in increasing the gear ratio on the OD side is particularly prominent.

(78) In the LOW mode, since rotation of the engine E is reduced in speed with a high gear ratio and transmitted to the differential gear 33, a large torque acts on the first output switching mechanism 37 disposed in the power transmission path thereof. However, with regard to the first output switching mechanism 37, the tubular countershaft 14 is fitted around the outer periphery of the inner main input shaft 15 to form a double tube structure, the countershaft 14, which transmits a large torque, is disposed on the outer peripheral side of the double tube and supported directly by the transmission case, the main input shaft 13, which transmits a relatively small torque, is supported via the countershaft 14, and it thereby becomes possible to support the first output switching mechanism 37 with high rigidity without carrying out special reinforcement.

(79) Furthermore, since the first output switching mechanism 37 is formed from a dog clutch that can selectively join to the countershaft 14 the fifth reduction gear 29 and the reverse drive gear 34, which are relatively rotatably supported on the countershaft 14, not only is it possible to reduce the drag resistance compared with a case in which a friction clutch is used, but it is also possible to selectively establish the LOW mode and the RVS mode merely by operating the first output switching mechanism 37 with a single actuator, thereby enabling the structure thereof to be simplified.

(80) Moreover, since the first fixed pulley 21A of the first pulley 21 and the second fixed pulley 22A of the second pulley 22 are disposed at mutually diagonal positions, the first movable pulley 21B of the first pulley 21 and the second movable pulley 22B of the second pulley 22 are disposed at mutually diagonal positions, the HI friction clutch 24B and the second induction gear 28 are disposed on the rear face side of the second fixed pulley 22A, the second output switching mechanism 38 and the output Shaft 15 are disposed on the rear face side of the first fixed pulley 21A, and the first output switching mechanism 37 is disposed at a position in which part thereof overlaps the second output switching mechanism 38 when viewed in the radial direction, it is possible to utilize effectively dead space formed on the rear face side of the first and second fixed pulleys 21A and 22A, thereby enabling the size of the continuously variable transmission T to be reduced.

(81) An embodiment of the present invention is explained above, but the present invention may be modified in a variety of ways as long as the modifications do not depart from the spirit and scope thereof.

(82) For example, in the embodiment the LOW friction clutch 24A is disposed on the main input shaft 13, and the HI friction clutch 24B is disposed on the second auxiliary input shaft 13B, but a LOW friction clutch 24A may be disposed on a first auxiliary input shaft 13A, and a HI friction clutch 24B may be disposed on a main input shaft 13.

(83) Furthermore, the drive source of the present invention is not limited to the engine E and may be a drive source of another type such as a motor/generator.