Multistage transmission for vehicle

The present application claims priority to Korean Patent Application No. 10-2017-0101997, filed on Aug. 11, 2017, which is incorporated herein by reference in its entirety.

The present disclosure relates generally to a multistage transmission for a vehicle.

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Recent increases in oil prices lead vehicle companies into more competition to improve fuel efficiency of vehicles. Especially in regards to the engine of a vehicle, research has focused on weight reduction through downsizing and improvement in fuel efficiency.

As an approach to improving fuel efficiency in regard to a vehicle transmission, there is a method of increasing the number of gears, which aims at operation of an engine at a desired operation point, ultimately leading to improvement in fuel efficiency.

A multistage transmission also enables an engine to operate at slow speed, i.e., at a relatively low RPM (revolutions per minute) range, so as to improve noise and vibration characteristics of a vehicle.

However, as the number of gears increases, the number of parts constituting the transmission correspondingly increases. This deteriorates mountability and overall transmission efficiency and also increases raw material costs and weight of the transmission. Therefore, we have discovered that in order to improve fuel efficiency through increasing the number of gears of a transmission, it is a key to devise a multistage transmission with reduced number of parts and having a simple structure.

The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.

The present disclosure provides a multistage transmission for a vehicle, the transmission providing at least ten forward stages and one reverse stage or more with a relatively small number of parts and a relatively simple structure, whereby the transmission enables an engine to silently operate at a desired operation point, thereby increasing fuel efficiency and achieving silent driving of a vehicle.

In one form of the present disclosure, a multistage transmission for a vehicle may include: an input shaft and an output shaft; a first planetary gear device, a second planetary gear device, a third planetary gear device, and a fourth planetary gear device, which are arranged to transfer rotary force between the input shaft and the output shaft, each of the first, second, third and fourth planetary gear devices including first, second and third rotary elements; and six shift elements connected to the rotary elements of the first to fourth planetary gear devices. In particular, the second rotary element of the first planetary gear device is fixedly connected to the third rotary element of the second planetary gear device, and the third rotary element of the first planetary gear device is fixedly connected to the third rotary element of the third planetary gear device and to the first rotary element of the fourth planetary gear device. The first rotary element of the second planetary gear device is fixedly connected to the input shaft and is fixedly connected to the second rotary element of the fourth planetary gear device, and the first rotary element of the third planetary gear device is fixedly connected to the second rotary element of the fourth planetary gear device.

The first rotary element of the first planetary gear device may be selectively connected to a transmission case and to the second rotary element of the second planetary gear device, the second rotary element of the first planetary gear device may be selectively connected to the transmission case, the third rotary element of the first planetary gear device may be selectively connected to the second rotary element of the second planetary gear device, the second rotary element of the third planetary gear device may be selectively connected to the output shaft, and the third rotary element of the fourth planetary gear device may be selectively connected to the output shaft.

The first rotary element of the first planetary gear device may be selectively connected to the transmission case via a first brake of the six shift elements, and the second rotary element of the first planetary gear device may be selectively connected to the transmission case via a second brake of the six shift elements.

The first rotary element of the first planetary gear device and the second rotary element of the second planetary gear device may be selectively connected to each other via a first clutch of the six shift elements, the third rotary element of the first planetary gear device and the second rotary element of the second planetary gear device may be selectively connected to each other via a second clutch of the six shift elements, the second rotary element of the third planetary gear device and the output shaft may be selectively connected to each other via a third clutch of the six shift elements, and the third rotary element of the fourth planetary gear device and the output shaft may be selectively connected to each other via a fourth clutch of the six shift elements.

In another form, a multistage transmission for a vehicle includes: a first planetary gear device, a second planetary gear device, a third planetary gear device, and a fourth planetary gear device each of which comprises first, second and third rotary elements; six shift elements configured to provide variable frictional force; and eight rotary shafts connected to the rotary elements of the first, second, third, and fourth planetary gear devices and respectively referred to as first, second, third, fourth, fifth, sixth, seventh, and eighth rotational shafts. In particular, the first rotational shaft is an input shaft fixedly connected to the first rotary element of the second planetary gear device, the first rotary element of the third planetary gear device, and the second rotary element of the fourth planetary gear device; the second rotational shaft is fixedly connected to the second rotary element of the second planetary gear device; the third rotational shaft is fixedly connected to the first rotary element of the first planetary gear device; the fourth rotational shaft is fixedly connected to the second rotary element of the first planetary gear device and the third rotary element of the second planetary gear device; the fifth rotational shaft is fixedly connected to the third rotary element of the first planetary gear device, the third rotary element of the third planetary gear device, and the first rotary element of the fourth planetary gear device; the sixth rotational shaft is fixedly connected to the second rotary element of the third planetary gear device; the seventh rotational shaft is fixedly connected to the third rotary element of the fourth planetary gear device; and the eighth rotational shaft is an output shaft.

The six shift elements may include: a first brake installed between the third rotational shaft and the transmission case; a second brake installed between the fourth rotational shaft and the transmission case; a first clutch installed between the second rotational shaft and the third rotational shaft; a second clutch installed between the second rotational shaft and the fifth rotational shaft; a third clutch installed between the sixth rotational shaft and the eighth rotational shaft; a fourth clutch installed between the seventh rotational shaft and the eighth rotational shaft.

As described above, a multistage transmission according to the present disclosure can provide at least ten forward stages and one reverse stage or more with a simplified structure and a reduced weight, thereby improving fuel efficiency of a vehicle.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating the construction of a multistage transmission for a vehicle in one form of the present disclosure;

FIG. 2 is an operation mode table showing gears that can be provided by the transmission of FIG. 1 ; and

FIG. 3 is a lever line diagram illustrating gears provided by the transmission of FIG. 1 .

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

Here, the term “fixedly connected” or the like means at least two members are connected to each other to always rotate together. Therefore, it is to be understood by a person of an ordinary skill in the art that the term “fixedly connected” or the like differs from the term “operably connected” or the like.

Here, the term “selectively connected” or the like means at least two members (e.g. a plurality of shafts including the input shaft and the output shaft, or plurality of rotary elements) that are connectable and disconnectable to/from each other, e.g. through at least one intermediate member or a shift element, and when connected rotate with the same rotational speed, or are connectable to the transmission housing through at least one intermediate member to be fixed to the transmission housing.

With reference to FIG. 1 , according to one form of the present disclosure, a multistage transmission for a vehicle, includes: an input shaft IN and an output shaft OUT; a first planetary gear device PG 1 , a second planetary gear device PG 2 , a third planetary gear device PG 3 , and a fourth planetary gear device PG 4 that are arranged to transfer rotary force between the input shaft IN and the output shaft OUT and each of which includes three rotary elements of the first to fourth planetary gear devices PG 1 to PG 4 .

A first rotary element S 1 of the first planetary gear device PG 1 can be selectively connected to a transmission case CS via one of the shift elements and is selectively connected to a second rotary element PC 2 of the second planetary gear device PG 2 . A second rotary element PC 1 of the first planetary gear device PG 1 can be selectively connected to the transmission case CS via another one of the shift elements and is fixedly connected to a third rotary element R 2 of the second planetary gear device PG 2 . A third rotary element R 1 of the first planetary gear device PG 1 is selectively connected to the second rotary element PC 2 of the second planetary gear device PG 2 and is fixedly connected to a third rotary element R 3 of the third planetary gear device PG 3 and a first rotary element S 4 of the fourth planetary gear device PG 4 .

A first rotary element S 2 of the second planetary gear device PG 2 is directly connected to the input shaft IN and is fixedly connected to a second rotary element PC 4 of the fourth planetary gear device PG 4 . A first rotary element R 3 of the third planetary gear device PG 3 is fixedly connected to a second rotary element PC 4 of the fourth planetary gear device PG 4 , and a second rotary element PC 3 of the third planetary gear device PG 3 is selectively connected to the output shaft OUT. A third rotary element R 4 of the fourth planetary gear device PG 4 is selectively connected to the output shaft OUT.

The first planetary gear device PG 1 , the second planetary gear device PG 2 , the third planetary gear device PG 3 , and the fourth planetary gear device PG 4 are arranged in this consecutive order, when viewed axially, from the input shaft IN to the output shaft OUT.

Specifically, the first rotary element 51 of the first planetary gear device PG 1 can be selectively connected to the transmission case CS via a first brake B 1 of the shift elements, and the second rotary element PC 1 of the first planetary gear device PG 1 can be selectively connected to the transmission case CS via a second brake B 2 of the shift elements.

That is, the first rotary element 51 and the second rotary element PC 1 of the first planetary gear device PG 1 are selectively connected to the transmission case CS by the first brake B 1 and the second brake B 2 , respectively, or are rendered freely rotatable.

The first rotary element 51 of the first planetary gear device PG 1 and the second rotary element PC 2 of the second planetary gear device PG 2 are selectively connected to each other via a first clutch C 1 of the shift elements. The third rotary element R 1 of the first planetary gear device PG 1 and the second rotary element PC 2 of the second planetary gear device PG 2 are selectively connected to each other via a second clutch C 2 of the shift elements. The second rotary element PC 3 of the third planetary gear device PG 3 and the output shaft OUT are selectively connected to each other via a third clutch C 3 of the shift elements. The third rotary element R 4 of the fourth planetary gear device PG 4 and the output shaft OUT are selectively connected to each other via a fourth clutch C 4 of the shift elements.

The first brake B 1 , the second brake B 2 , the first clutch C 1 , the second clutch C 2 , the third clutch C 3 , and the fourth clutch C 4 are all controlled by a controller. Those elements are controlled in accordance with drive conditions of a vehicle on the basis of an operation mode table of FIG. 2 . The multistage transmission of the present disclosure can form a total of at least forward ten stages and reverse one stage or more.

The first brake B 1 , the second brake B 2 , the first clutch C 1 , the second clutch C 2 , the third clutch C 3 , the fourth clutch C 4 are collectively referred to as ‘shift elements’. When the transmission of the present disclosure performs a series of gear shifts from a first gear to a tenth gear as illustrated in FIG. 2 , the transmission has a clutch- to-clutch shifting structure in which one shift element is disengaged and another shift element is engaged.

The first rotary element, the second rotary element, and the third rotary element of the first planetary gear device PG 1 are respectively implemented by a first sun gear S 1 , a first carrier PC 1 , and a first ring gear R 1 . The first rotary element, the second rotary element, and the third rotary element of the second planetary gear device PG 2 are respectively implemented by a second sun gear S 2 , a second carrier PC 2 , and a second ring gear R 2 . The first rotary element, the second rotary element, and the third rotary element of the third planetary gear device PG 3 are respectively implemented by a third sun gear S 3 , a third carrier PC 3 , and a third ring gear. The first rotary element, the second rotary element, and the third rotary element of the fourth planetary gear device PG 4 are respectively implemented by a fourth sun gear S 4 , a fourth carrier PC 4 , and a fourth ring gear R 4 .

The multistage transmission structured as described above can be also expressed as a multistage transmission including: a first planetary gear device PG 1 , a second planetary gear device PG 2 , a third planetary gear device PG 3 , and a fourth planetary gear device PG 4 each including three rotary elements; six shift elements providing variable frictional force; and eight rotational shafts respectively referred to as first to eighth rotational shafts and connected to the rotary elements of the first to fourth planetary gear devices PG 1 to PG 4 .

The first rotational shaft RS 1 is an input shaft IN fixedly connected to a first rotary element S 2 of the second planetary gear device PG 2 , a first rotary element S 3 of the third planetary gear device PG 3 , and a second rotary element PC 4 of the fourth planetary gear device PG 4 . The second rotational shaft RS 2 is fixedly connected to a second rotary element PC 2 of the second planetary gear device PG 2 . The third rotational shaft RS 3 is fixedly connected to a first rotary element S 1 of the first planetary gear device PG 1 . The fourth rotational shaft RS 4 is fixedly connected to a second rotary element PC 1 of the first planetary gear device PG 1 and a third rotary element R 2 of the second planetary gear device PG 2 . The fifth rotational shaft RS 5 is fixedly connected to a third rotary element R 1 of the first planetary gear device PG 1 , a third rotary element R 3 of the third planetary gear device PG 3 , and a first rotary element S 4 of the fourth planetary gear device PG 4 . The sixth rotational shaft RS 6 is fixedly connected to a second rotary element PC 3 of the third planetary gear device PG 3 . The seventh rotational shaft RS 7 is fixedly connected to a third rotary element R 4 of the fourth planetary gear device PG 4 . The eighth rotational shat RS 8 is an output shaft OUT.

Among the six shift elements, a first brake B 1 is installed between the third rotational shaft RS 3 and a transmission case CS, a second brake B 2 is installed between the fourth rotational shaft RS 4 and the transmission case CS, a first clutch C 1 is installed between the second rotational shaft RS 2 and the third rotational shaft RS 3 , a second clutch C 2 is installed between the second rotational shaft RS 2 and the fifth rotational shaft RS 5 , a third clutch C 3 is installed between the sixth rotational shaft RS 6 and the eighth rotational shaft RS 8 , and a fourth clutch C 4 is installed between the seventh rotational shaft RS 7 and the eighth rotational shaft RS 8 .

As described above, the multistage transmission composed of four simple planetary gear devices and six shift elements has ten forward gears and one reverse gear as shown in the operation mode table of FIG. 2 . Therefore, according to the present disclosure, it is possible to realize a multistage transmission having at least ten forward stages and one reverse stage or more with a reduced number of parts and a reduced weight in comparison with conventional counterparts, thereby providing desired gear ratios in accordance with drive conditions of a vehicle and thus improving fuel efficiency of a vehicle.

Although an exemplary form of the present disclosure has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the present disclosure.