WO2004008001A1

WO2004008001A1 - Wide range continuously variable transmission

Info

Publication number: WO2004008001A1
Application number: PCT/KR2003/000745
Authority: WO
Inventors: Jongwan Lee
Original assignee: Jongwan Lee
Priority date: 2002-07-12
Filing date: 2003-04-15
Publication date: 2004-01-22
Also published as: AU2003219600A1

Abstract

The present invention relates to a continuously variable transmission. The continuously variable transmission comprises: a continuously variable transmission part (10) for transmitting power from a driving shaft (12) to a driven shaft (14) at a continuous rate of speed; a first planetary gear device (20) with which said driven shaft (14) is provided; a second planetary gear device (30) with which said driven shaft (14) is provided; a second clutch (52) with which said driven shaft (14) is provided; a fourth clutch (54) with which said driven shaft (14) is provided; a speed reduction member (40) installed between said driving shaft (12) and driven shaft (14); a seventh clutch installed in said driving shaft (12); and a first clutch (51) installed in said driving shaft (12). In addition, said speed reduction member (40) has a reduction ratio so that the speed ratio of a first carrier (24) to a first sun gear (21) may be maximum one, and that the gear ratio of a second ring gear (31) to a second sun gear (33) may be (speed of a first sun gear/speed of a first ring gear)-1 when the transmission rate of said continuous variable transmission part (10) is maximum.

Description

WIDE RANGE CONTINUOUSLY VARIABLE TRANSMISSION

[FIELD OF THE INVENTION]

The present invention relates to continuously variable transmissions (CVT), and more particularly to the type of CVT that have wide coverage of speed ratio and high output torque.

[BACKGROUND OF THE INVENTION]

A CVT transmits power of a driving shaft to a driven shaft to get desirable torque and speed at the driven shaft in a infinitely variable ratio. There are many different types of CVT, but the most common type is belt-type. A belt-type CVT is consisted of two pulleys and a belt, and transmits power by friction between pulleys and a belt. Transmittable torque is proportional to the coefficient of friction.

With high coefficient of friction, the ratio of radial-length/axial-length of pulley face should be small in order to change speed ratio by pushing pulley sheaves. Also the width of belt should be wide. Diameter of pulleys should be large for wide coverage of speed ratio.

To get high torque and wide ratio range, several mechanisms, which expand speed ratio range without enlarging size of the pulley, were invented. Figure 1 is a schematic diagram illustrating a prior art that the inventor filed on Korean patent application No. 10-2002-04421.

In this prior art, some clutches operate on asynchronous state. Consequently synchronizing mechamsm is needed and it consumes time to synchronize. The mechanism becomes large and hard to operate swiftly.

[DETAILED DESCRIPTION OF THE INVENTION]

Fig. 2 is a schematic diagram illustrating the first preferred embodiment of the present invention.

Referring to Fig. 2, the first preferred embodiment is composed of variator (10) which transfers power from driving shaft (12) to driven shaft (14) in continuous speed ratio, a first planetary gear set (20) installed on said driven shaft (14), a second planetary gear set (30) installed on said driven shaft (14), a second clutch (52) installed on said driven shaft (14), a fourth clutch (54) installed on said driven shaft (14), a drive train of fixed ratio (40) installed between said driving shaft (12) and driven shaft (14), a seventh clutch installed on said driving shaft (12), and a first clutch (51) installed on said driving shaft (12).

A first sun gear (21) of said first planetary gear set (20) is fixed on said driven shaft (14). First pinion gears (22) mesh with said first sun gear (21). A first ring gear (23) meshes with said first pinion gears (22). A first carrier (24) supports said first pinion gears (22) and rotates with said drive train (40). A second sun gear (31) of said second planetary gear set (30) is installed on the same centerline with said first sun gear (21) to rotate in one body. Second pinion gears (32) mesh with said second sun gear (31). A second ring gear (33) meshes with said second pinion gears (32). A second carrier (34) supports said second pinion gears (32) and is installed to rotate in one body with said first ring gear (23) and output shaft (18). Said first and second sun gears (21, 31) may be one gear when module and tooth number are identical.

Said drive train (40) is composed of a first gear (41) installed rotatably on said driving shaft (12), a third gear (43) installed on said driven shaft (14) to rotate in one body with said first carrier (24), and a second gear (42) meshes with said first and third gears (41, 43). Said first clutch (51) is installed to transfer selectively rotation of said driving shaft

(12) to said first carrier (24) through said drive train (40). Said second clutch (52) is installed to engage selectively said first ring gear (23) with said first carrier (24) in order to make said first planetary gear set (20) rotate in one body. Said second clutch (52) can be located variously, because a planetary gear set rotates in one body by joining any two members together out of four members. Said fourth clutch (54) is installed to lock selectively said second ring gear (33) on casing. A seventh clutch (57) installed on said driving shaft (12) is starting clutch allowing speed ratio of —minimum value of this invention.

Tooth number ratio of said first gear (41) to said third gear (43) should be same with the minimum speed ratio of said variator (10). Tooth number ratio of said second ring gear (33) to said second sun gear (31) should be same with (speed of said first sun gear / speed of said first ring gear) -1 when speed ratio of said variator (10) is the maximum.

Hereafter operation of the embodiment is explained more specifically with reference to Fig. 3. Followings are assumed. Ratio range of variator (10) is 1/1.48(=0.676)~ 1.4865. Tooth numbers are 25 for first gear (41), 37 for third gear (43), 18 for first sun gear, 48 for first ring gear, 16 for second sun gear, and 48 for second ring gear.

In the beginning, fourth clutch (54) is engaged and other clutches are disengaged, speed ratio of variator (10) is the minimum (=0.676). Speed of driven shaft (14) is reduced by second planetary gear set (30). The minimum speed ratio of the embodiment is 0.676/4 =0.169. As speed ratio of variator (10) increases up to maximum, speed of output shaft (18) increases up to 1.4865/4 =0.3716, and then speed of first ring gear (23) become minimum. Now speed ratio of drive train (40) and speed ratio of variator (10) are same, and speeds of first gear (41) and driving shaft (12) are same. Tooth numbers of gears were selected carefully for this condition.

In this condition, first clutch (51) is engaged in synchronized state, and fourth clutch (54) is disengaged. As ratio of variator (10) decreases down to minimum, speed of output shaft

(18) increases up to 25/37*(48+18)/48 -0.676*18/48 =0.676, and then speed of all the members of first planetary gear set (20) become same. And speed of all the members of second planetary gear set (30) becomes same.

Then, second clutch (52) is engaged in synchronized state, and first clutch (51) is disengaged. All the members on driven shaft (14) rotate in one body. As ratio of variator (10) increases up to maximum, speed of output shaft (18) increases up to 1.4865 . Speed ratio range of this embodiment is 1.4865/0.169 =8.8 .

In addition, an eighth clutch (58) may be added as shown Fig. 1, for reverse rotation of output shaft (18) by locking rotation of first carrier (24). Said eighth clutch can engage or disengage said drive train (40) with casing. Said eighth clutch (58) may be combined with said first clutch (51) as shown in Fig. 4 or Fig. 6. And said second clutch (52) and said fourth clutch (54) may be combined and may be shifted by one actuator as shown in Fig. 4. And said seventh clutch (57) may be installed on said output shaft (18) as shown in Fig. 4.

For reverse rotation of said output shaft (18), said first clutch (51) or said eighth clutch (58) is engaged with casing, and said second and fourth clutches (52, 54) are disengaged. The minimum reverse speed ratio is 0.676*(-18/48) =-0.2533 at minimum speed ratio of said variator (10). The maximum reverse speed ratio is 1.4865*(-18/48) =-0.5574 at maximum speed ratio of said variator (10).

Hereafter the same part number means part of the same function. The second preferred embodiment is shown in Fig. 4. Compared to the first embodiment, seventh clutch is moved from driving shaft (12) to output shaft (18), reverse drive function is added to first clutch (51), and second clutch (52) is combined with fourth clutch (54). This shows possibility of various modification. Tooth numbers and ratios are same as the first embodiment. Fig. 6 is a schematic diagram illustrating the third preferred embodiment of the present invention. It comprises variator (10), a first planetary gear set (20), a second planetary gear set (30), a first clutch (51), a fourth clutch (54), and a drive train of fixed ratio (40). First sun gear (21) and second sun gear (31) are separated for independent rotation. A sixth clutch (56) is installed between said two sun gears (21, 31) to unite them. A fifth clutch (55) is installed to connect said first ring gear (23) to said second sun gear (31). A third clutch (53) is installed to connect said first ring gear (23) to said second carrier (34).

Hereafter operation of the third embodiment is explained more specifically with reference to Fig. 7. The continuous ratio range of the third preferred embodiment is composed of four regions compared to three regions of said first preferred embodiment. Tooth numbers and speed ratio of said variator (10) are same as the first embodiment.

For the first region, said first clutch (51) is engaged with driving shaft (12), fourth and fifth clutches (54, 55) are engaged, and third and sixth clutches (53, 56) are disengaged. Speed ratio of output shaft (18) is (25/37*(48+18)/48 -1.4865*18/48)/4 =0.0929 when speed ratio of variator (10) is maximum. As ratio of variator (10) decreases down to minimum, speed of first ring gear (23) become maximum, and speed of output shaft (18) increases up to (25/37*(48+18)/48 -0.676* 18/48)/4 =0.169 .

Now all the members of first planetary gear set (20) rotate at same speed. In this condition, sixth clutch (56) is engaged in synchronized state, and fifth clutch (55) is disengaged. It is the second region. As speed ratio of variator (10) increases up to maximum, speed of output shaft (18) increases up to 1.4865/4 =0.3716, and then speed of first ring gear (23) become minimum which is same with the speed of second carrier (34).

In this condition, said third clutch (53) is engaged in synchronized state, and said fourth clutch (54) is disengaged. It is the third region. As speed ratio of variator (10) decreases down to minimum, speed of first ring gear (23) become minimum, speed of first sun gear (21) become niinimum, and all the members of first planetary gear set (20) rotate in same speed. Speed ratio of output shaft (18) increases up to 25/37*(48+18)/48 -0.676*18/48 =0.676.

In this condition, fifth clutch (55) is engaged in synchronized state, and said first clutch (51) is disengaged. It is the fourth region. Because all the members on driven shaft (14) rotate in one body, maximum speed ratio of output shaft (18) is 1.4865. Speed ratio range of this embodiment is 1.4865/0.0929 =16.

For reverse drive of output shaft (18), first clutch (51) is engaged with casing, fourth and fifth clutches (54, 55) are engaged, and said third and sixth clutches (53, 56) are disengaged. Then seventh clutch (57) is engaged gradually. Range of speed ratio is (0.676—

1.4865)*(-18/48)/4 =-0.0633 0.1393. If fourth clutch (54) is disengaged and third clutch (53) is engaged, range of speed ratio is (0.676- 1.4865)*(-18/48) =-0.2535- -0.5574 .

In addition, said seventh clutch (57) may be replaced by a torque converter or others, and said drive train (40) may be replaced by a chain drive or others.

Switching of all the clutches except starting clutch (seventh clutch) is performed on synchronized condition. These clutches can be operated swiftly, and are compact.

It is noted that the present invention is not limited to the preferred embodiments described above, and it is apparent that variations and modifications by those skilled in the art can be effected within the spirit and scope of the present invention defined in the claims.

Therefore, above wide range CVT is equipped with two serial planetary gear sets, a drive train, and a plurality of clutches to a variator which has narrow ratio range and limited torque capacity. Coverage of speed ratio is expanded continuously with compact and swift synchronous clutches. Consequently the CVT become compact, light, and inexpensive.

[BRIEF DESCRIPTION OF THE DRAWINGS] The above object and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which;

Fig. 1 is a schematic diagram illustrating a prior art;

Fig. 2 is a schematic diagram illustrating the first preferred embodiment of the present invention;

Fig. 3 is a graph of the first embodiment illustrating the relationship among clutch states, variator ratio, and transmission ratio;

Fig. 4 is a schematic diagram illustrating the second preferred embodiment of the present invention; Fig. 5 is a graph of the second embodiment illustrating the relationship among clutch states, variator ratio, and transmission ratio;

Fig. 6 is a schematic diagram illustrating the third preferred embodiment of the present invention;

Fig. 7 is a graph of the third embodiment illustrating the relationship among clutch states, variator ratio, and transmission ratio;

[BEST TYPE OF THE INVENTION]

Drawing No. 4 with the seventh clutch on the driving shaft.

[POSSIBLE INDUSTRIAL APPLICATION]

Present invention is suitable for a transmission of automobile. Also it is suitable to transforms speed and torque of engine to required speed and torque in continuous ratio for machining tools, industrial equipments, agricultural equipments, and etc.

Claims

[CLAIMS]What is claimed is:

1. A wide range continuously variable transmission comprising a variator which controls speed ratio of driven shaft to driving shaft in continuous ratio; a first planetary gear set having a first sun gear drivingly connected with said driven shaft, a plurality of first pinion gears meshing with said first sun gear, a first ring gear meshing with said first pinion gears, and a first carrier supporting said first pinion gears; a drive train of fixed-ratio that transmits power of said driving shaft to said first carrier; a second planetary gear set having a second sun gear formed in a body with said first sun gear, a plurality of second pinion gears meshing with said second sun gear, a second ring gear meshing with said second pinion gears, and a carrier supporting said second pinion gears, and rotating in a body with said first ring gear and output shaft; a first clutch selectively disconnecting said drive train; a second clutch selectively forcing all the member of first planetary gear set to rotate in the same speed; a fourth clutch selectively connecting said second ring gear with immovable case; and said drive train has a gear ratio so that speed ratio of said first carrier to said first sun gear may be 1 in maximum, tooth number ratio of said second ring gear to said second sun gear is equal to (speed ratio of said first sun gear to said first ring gear)-l at the maximum speed ratio of said variator.

2. A wide range continuously variable transmission according to claim 1, said second clutch and said fourth clutch are combined and may be shifted by one actuator.

3. A wide range continuously variable transmission according to claim 1 and claim 2, said first clutch have a third position selectively locking said first carrier immovably.

4. A wide range continuously variable transmission according to claim 1 through claim 3, said first sun gear and said second sun gear are one gear.

5. A wide range continuously variable transmission comprising a variator which controls speed ratio of driven shaft to driving shaft in continuous ratio; a first planetary gear set having a first sun gear drivingly connected with said driven shaft, a plurality of first pinion gears meshing with said first sun gear, a first ring gear meshing with said first pinion gears, and a first carrier supporting said first pinion gears; a drive train of fixed-ratio that transmits power of said driving shaft to said first carrier; a second planetary gear set having a second sun gear separated from said first sun gear on the same center line, a plurality of second pinion gears meshing with said second sun gear, a second ring gear meshing with said second pinion gears, and a carrier supporting said second pinion gears, and rotating in a body with said output shaft; a first clutch selectively connecting said drive train or selectively locking said first carrier; a third clutch selectively connecting said first ring gear with said second carrier; a fourth clutch selectively connecting said second ring gear with immovable case; a fifth clutch selectively connecting said first ring gear with said second sun gearr; a sixth clutch selectively connecting said first sun gear with said second sun gear; and said drive train has a gear ratio so that speed ratio of said first carrier to said first sun gear may be 1 in maximum, tooth number ratio of said second ring gear to said second sun gear is equal to (speed ratio of said first sun gear to said first ring gear)-l at the maximum speed ratio of said variator.