Gear train of an automatic five-speed transmission for a vehicle

Abstract: A gear train of an automatic five-speed transmission includes an input shaft (4) for transferring the power of an engine via a torque converter (2), a first-speed drive gear (6) mounted on the input shaft, a first-speed driven gear (8) meshed with the first-drive gear to produce a reduced speed ratio, an output shaft (10) for transferring the power received from the first-speed driven gear to a differential gear (D), a planetary gear unit (12) connected with the input shaft, a first friction element (C1) selectively connected with the input shaft and the output shaft for producing a first reduced speed ratio, a second friction element (C2) selectively connected with the input shaft for transferring the input power through a first power transfer member to a first sun gear (14) of the planetary gear unit to produce a second reduced speed ratio, a third friction element (C3) selectively connected with the input shaft for transferring the input power through a second power transfer member (28) to the planetary carrier (18) of the planetary gear unit serving as an input element, and a fourth friction element (B1) for gripping a third power transfer member (30) to employ as a reacting element a second sun gear (26) receiving the rotational force of the first sun gear of the planetary gear unit serving an input element.

Description: The present invention concerns a gear train of an automatic five-speed transmission for a vehicle and more particularly a gear train for obtaining five steps of forward moving speed and one step of backward moving speed according to driving condition. Conventionally, an automatic transmission for a vehicle includes a planetary gear unit connected between a torque converter and a driven shaft, which planetary gear unit comprises sun gears, a plurality of planetary gears, a planetary carrier for carrying the planetary gears, and a ring gear. A plurality of clutches and friction elements are controlled to selectively grip the gears of the planetary gear unit so as to obtain a target speed. As is well known, such conventional automatic transmission suffers inefficiency of the fuel consumption ratio or power or driving performance particularly in a high speed engine. Hence, there has been proposed a multi-stage control of speed in order to maximize the performance of a high speed engine. Meanwhile, the multi-stage speed control of a transmission is preferably required using a minimum number of the friction elements to facilitate the speed control. In addition it is preferable to minimize the number of the friction elements in order to reduce volume and weight. In this respect, the U. S. Patent No. 5,112,285 discloses a multi-stage speed control of a transmission, wherein a speed change may be obtained by shifting the frictional grip from one element to another. This patent requires many number of friction elements increasing the volume and weight. FR-A-2 659715 discloses a gear train of an automatic five-speed transmission comprising: an input means for transferring the power of an engine via a torque converter; a fifth-speed drive gear fixedly mounted on said input means; a fifth-speed driven gear meshed with said drive gear to produce a speed ratio; an output means for transferring the power received from said driven gear to a differential gear; a planetary gear unit connected with said input means; a first friction element selectively connected with said input means and output means for producing a fifth speed ratio; a second friction element selectively connected with said input means for transferring the input power through a first power transfer member to a first sun gear of said planetary gear unit to produce a reduced speed ratio; a third friction element selectively connected with said input means for transferring the input power through a second power transfer member to the planetary carrier of said planetary gear unit serving as an input element; and a fourth friction element for gripping a third power transfer member to employ as a reacting element a second sun gear receiving the rotational force of said first sun gear of said planetary gear unit serving as an input element. It is an aim of the present invention to provide a gear train of an automatic multi-stage speed control transmission for improving the engine performance. It is another aim of the present invention means for facilitating the control of the gear train of the multi-stage transmission. It is still another aim of the present invention to provide a gear train of an automatic transmission having a reduced number of gears to decrease the volume and weight. According to an aspect of the present invention, a gear train of an automatic five-speed transmission comprises: an input means for transferring the power of an engine via a torque converter; a first-speed drive gear mounted on the input means; a first-speed driven gear meshed with the first-drive gear to produce a reduced speed ratio; an output means for transferring the power received from the first-speed driven gear to a differential gear; a planetary gear unit connected with the input means; a first friction element selectively connected with the input means and output means for producing a first reduced speed ratio; a second friction element selectively connected with the input means for transferring the input power through a first power transfer member to a first sun gear of the planetary gear unit to produce a second reduced speed ratio; a third friction element selectively connected with the input means for transferring the input power through a second power transfer member to the planetary carrier of the planetary gear unit serving as an input element; and a fourth friction element for gripping a third power transfer member to employ as a reacting element a second sun gear receiving the rotational force of the first sun gear of the planetary gear unit serving as an input element, and a first one way clutch connected with the first friction element and output means to obtain an anti-clockwise rotation with respect to said engine. In an embodiment, a sixth friction element is directly connected with the first driven gear and output means for breaking the engine during the first speed. In a still further embodiment, the one-way clutch is idling by working the sixth friction element. In a still further embodiment, a second one-way clutch is preferable connected with the planetary carrier so as to prevent its anti-clockwise rotation with respect to the engine. In a still further embodiment, the planetary gear unit produces a reduced reverse speed ratio by working the seventh friction element for transferring the input rotational force to the second sun gear and the fifth friction element for gripping the planetary carrier. In a still further embodiment, the planetary gear unit is so designed that the second and third friction elements directly connect the first sun gear and the planetary carrier to work together as an input element to obtain the same rotational speed ratio of the output as the input. The present invention will now be described further, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is schematic diagram for illustrating the gear train of an automatic five-speed transmission according to an embodiment of the present invention; and Fig. 2 is a table for showing the operation of the friction elements according to the six steps of forward five speed ratios and backward one speed ratio in the gear train of Fig. 1; Referring to Fig. 1, a transmission according to an embodiment of the present invention includes an input shaft 4 connected with an engine (not shown) through a torque converter 2, a first speed drive gear 6 mounted on the input shaft 4, and a first speed driven gear 8 meshed with the first speed drive gear 6 for transferring the rotational driving force to a differential gear D. The first speed drive and driven gears 6 and 8 provide a first speed according to their tooth ratio. Between the first driven gear 8 and an output shaft 10 is provided a first friction element C1 for connecting the rotational driving force of the input shaft 4 to the output shaft 10. In addition, an one-way clutch F1 is provided between the first friction element C1 and the output shaft 10 to reduce the gear shift shock. The first one-way clutch F1 is designed to receive the engine power anti-clockwise with respect to the engine, so that the coasting torque of a vehicle is not transferred to the engine in the first speed. The gear train also includes a planetary gear unit 12 with a first sun gear 14 mounted on a first power transfer member 16, which may be operatively connected with the input shaft 4 by working a second friction element C2 to transfer the rotational driving force of the input shaft 4 to the first sun gear 14 and thus to the planetary gear unit 12 with a planetary carrier 18. The planetary carrier 18 is designed to receive the rotational driving force anti-clockwise with respect to the engine, but the rotation anti-clockwise may be prevented by working a second one-way clutch F2. The planetary gear unit 12 further comprises a first pinion gear 20 meshed with the first sun gear 14, a second pinion gear 22 meshed with the first pinion gear, a ring gear 24 internally meshed with the second pinion gear, and a second sun gear 26 meshed with the second pinion gear 22. The first and second pinion gears 20 and 22 are connected with each other with a given interval by the planetary carrier 18, which receives the rotational driving force of the input shaft 4 via a second power transfer member 28. A third friction element C3 is provided to selectively transfer the rotational driving force of the input shaft 4 to the second power transfer member 28. When the third friction element C3 is worked to grip the second power transfer member 28, a fourth friction element B1 mounted on the inside of the housing T of the transmission may be worked to check a third power transfer member 30 thus fixing the second sun gear 26 of the planetary gear unit 12. The fourth friction element B1 may be a kind of band break to grip the periphery of the third power transfer member 30 stopping its rotation. A fifth friction element B2 is mounted on the inside of the housing T of the transmission to prevent the planetary carrier 18 from being rotated clockwise with respect to the engine, so that it may be used to transfer a reversely driving torque of a gear to the engine in a gear shift. An output drum member 32 integrally formed with the ring gear 24 is provided with a transfer drive gear 34, which is meshed with a transfer driven gear 36 mounted on the output shaft lo to transfer the speed ratio of the planetary gear unit 12. The output shaft 10 is designed to be gripped by the sixth friction element C4 in the forward first speed so as to transfer the reversely driving torque to the engine through the first drive and driven gears 6 and 8. Between the input shaft 4 and the third power transfer member 30 is provided a seventh friction element C5 used to backward move the vehicle, through which the rotational force of the input shaft is transferred to the second sun gear 26 of the planetary gear unit 12. An end reduction gear 38 is provided between the output shaft 10 and the differential gear D. Thus, as shown in Fig. 2, the friction elements and one-way clutches, which are hydraulically controlled, are used to produce various speed ratios. In the backward speed ratio R, the seventh and fifth friction elements C5 and B2 are worked to transfer the rotational force of the input shaft 4 to the third power transfer member 30 thus rotating the second sun gear 26 of the planetary gear unit 12. Meanwhile, the fifth friction element B2 fixes the planetary carrier 18 that the second pinion gear 22 rotates only on its axis to rotate the ring gear 24 anti-clockwise with respect to the engine, thereby obtaining the backward speed ratio. The rotational force of the ring gear 24 is transferred to the differential gear D through the output drum member 32, drive and driven gears 34 and 36, output shaft 10, and end reduction gear 38. In the first forward speed ratio V1, the first friction element C1 is worked to transfer the rotational force of the input shaft 4 to the output shaft 10 through the first drive and driven gears 6 and 8. In this case, the first one-way clutch F1 makes the rotational force work anti-clockwise with respect to the engine. The engine is also prevented from being reversely driven (engine brake) because the first one-way clutch F1 freewheels when reversely driving. In the second forward speed ratio V2, the second friction element C2 is worked in addition to the first friction element C1 so that the rotational force of the input shaft 4 is transferred to the first power transfer member 16 rotating the first sun gear 14 of the planetary gear unit 12. The first sun gear 14 tries to force the planetary carrier 18 anti-clockwise with respect to the engine via the first and second pinion gears 20 and 22, but the second one-way clutch F2 checks the anti-clockwise rotation of the planetary carrier 18 to serve as a reacting element, which causes the second pinion gear 22 to rotate only on its axis so that the ring gear 24 is rotated clockwise with respect to the engine producing the second forward speed ratio through the output drum member 32. The rotational force is transferred to the differential gear D through the transfer drive and driven gears 34 and 36, output shaft 10, and the end reduction gear 38, driving the vehicle faster than in the first forward speed ratio. The second one-way clutch F2 freewheels during the reverse drive, so that the engine brake is not worked. In the third forward speed ratio V3, the fourth friction element B1 is worked in addition to the state of the second forward speed ratio to brake the third power transfer member 30, thus causing the second sun gear 26 to serve as a reacting element. The planetary gear unit 12 receiving the input via the first sun gear 14 produces the third forward speed ratio less than the second forward speed ratio through the first and second pinion gears 20 and 22 and the ring gear 24 because the second pinion gear 22 rotates along the periphery of the second sun gear 26 fixed. In this case, the reverse drive torque is transferred to the input shaft 4 so as to more quickly reduce the vehicle speed during coasting. In the fourth forward speed ratio V4, the fourth friction element B1 is released and the third friction element C3 is worked again, so that the first sun gear 14 and the planetary carrier 18 simultaneously serve as input elements and therefore the planetary gear unit 12 is rotated as a whole to produce the output with the same number of rotations as the input. In this case, the engine brake is also workable to quickly reduce the vehicle speed during coasting. In the fifth forward speed ratio V5, the second friction element C2 is released and the fourth friction element B1 is worked again to brake the third power transfer member 30, so that the rotational force of the input shaft 4 is transferred to the planetary gear unit 12 through the third friction element C3 and the planetary carrier 18. Meanwhile, the second sun gear 26 is fixed serving as a reacting element, so that the second pinion gear 22 rotates along the periphery of the second sun gear 26 with the same speed as the planetary carrier 18. Thus the ring gear 24 receives the sum of the rotations that the second pinion gear 22 makes on its own axis and along the periphery of the second sun gear 26, thereby producing the overdrive state of the fifth forward speed ratio. Of course, the engine brake is workable to quickly reduce the vehicle speed. The four speed ratios of the forward four-speed range IV are obtained in the same manner as the four speed ratios of the forward five-speed range V. Likewise the three speed ratios of the forward three-speed range III are obtained in the same manner. of course, the first speed ratio of the forward two-speed range II is obtained in the same manner, but its second speed ratio is obtained by working the engine brake, wherein the reverse drive torque of the engine is produced as follows. In the speed range II, the second speed ratio is obtained by applying the first and second friction elements C1 and C2 and the fifth friction element B2, so that the planetary carrier 18 is fixed to reversely transfer the driven power of the wheels to the engine during coasting, thus amplifying the reverse drive torque which affects the drive wheel and is divided by the radius of the drive wheel to calculate the driving resistance. In the forward one-speed range L, the one speed ratio is obtained by applying the first and sixth friction elements C1 and C4, which is different from the other speed ranges. This means that the rotational force of the input shaft 4 is transferred to the output shaft 10 through the transfer drive and driven gears 6 and 8. Hence, the engine brake is applied to produce the reverse drive power. In this case, the first one-way clutch F1 does nothing. Thus the gear train described above according to an embodiment of the present invention gives the engine brake effect in all speed ranges, and employs a planetary gear unit of Ravigneaux type to obtain five speed ratios simplifying the structure and increasing the engine performance. Moreover, one of the second and fourth friction elements C2 and B1 is controlled to make a gear shift between the first and second speed ratios or the second and third speed ratios, thus facilitating the control of the speed-changing gears.

Claims: A gear train of an automatic five-speed transmission comprising:- an input means (4, 102) for transferring the power of an engine via a torque converter; a first-speed drive gear (6) mounted on said input means; a first-speed driven gear (8) meshed with said first-drive gear to produce a reduced speed ratio; an output means (10) for transferring the power received from said first-speed driven gear to a differential gear (D); a planetary gear unit (12) connected with said input means; a first friction element (C1) selectively connected with said input means and output means for producing a first reduced speed ratio; a second friction element (C2) selectively connected with said input means for transferring the input power through a first power transfer member to a first sun gear (14) of said planetary gear unit to produce a second reduced speed ratio; a third friction element (C3) selectively connected with said input means for transferring the input power through a second power transfer member (28) to the planetary carrier (18) of said planetary gear unit serving as an input element; and a fourth friction element (B1) for gripping a third power transfer member (30) to employ as a reacting element a second sun gear (26) receiving the rotational force of said first sun gear of said planetary gear unit serving as an input element, and characterised in that a first one-way clutch (F1) is connected with the first friction element and output means to obtain an anti-clockwise rotation with respect to said engine. A gear train of an automatic five-speed transmission as claimed in claim 1, wherein a sixth friction element (C4) is directly connected with said first driven gear and output means for breaking said engine during said first speed. A gear train of an automatic five-speed transmission as claimed in claim 2, wherein said one-way clutch (F1) is designed to idle by applying said sixth friction element (C4). A gear train of an automatic five-speed transmission as claimed in anyone of claims 1, 2 or 3, wherein a second one-way clutch (F2) is connected with said planetary carrier so as to prevent its anti-clockwise rotation with respect to said engine. A gear train of an automatic five-speed transmission as claimed in anyone of the preceding claims, wherein said planetary gear unit is designed to produce a reduced reverse speed ratio by applying a seventh friction element (C5) for transferring the input rotational force to said second sun gear and a fifth friction element (B2) for gripping said planetary carrier. A gear train of an automatic five-speed transmission as claimed in anyone of the preceding claims, wherein said fourth friction element is a band brake (B1). A gear train of an automatic five-speed transmission as claimed in anyone of the preceding claims, wherein said planetary gear unit is so designed that said second and third friction elements (C2, C3) directly connect said first sun gear (14) and said planetary carrier (18) to work together as an input element to obtain the same rotational speed ratio of said output as said input.

Inventors: PARK DONGHOON, SEO TAEAEOK, PARK, DONGHOON, SEO, TAEAEOK
Applicants: HYUNDAI MOTOR CO LTD, HYUNDAI MOTOR COMPANY
Application year: 1995
Main classification: F16H3
IPC codes: F16H3