CN104373534B - A kind of multi-shifting speed variator of planetary gear construction - Google Patents

Abstract

A multi-speed transmission with a planetary gear structure, which includes a housing, an input member, an output member, the first, second, and third planetary gear sets, and the first, second, third, fourth, fifth, sixth, and seventh interconnections Components and the first, second, third, fourth, fifth, and sixth torque transmission devices; the first, second, and third planetary gear sets are arranged in sequence from the input end to the output end; the first, second, third, fourth, fifth, and sixth The torque transmission device includes three brakes and three clutches. The first, second and third torque transmission devices are located between the second and third planetary gear sets and are parallel to the housing; the fourth, fifth and sixth torque transmission devices are The device is located between the first and second planetary gear sets, wherein the fourth torque transmission device is close to the center of rotation, the fifth and sixth torque transmission devices are located side by side above the fourth torque transmission device, and the above-mentioned components are all located in the housing ; The present invention is a compact multi-speed transmission.

Description

A multi-speed transmission with planetary gear structure

technical field

The invention relates to a multi-speed transmission with a planetary gear structure, in particular to an automatic transmission applied to motor vehicles, and belongs to the technical field of motor vehicle transmissions.

Background technique

The planetary gear structure is widely used in the field of automotive automatic transmissions due to its advantages of compact structure and large load capacity. An automatic transmission with a planetary gear structure needs to achieve different forward and reverse gears by combining different shifting elements such as brakes and clutches.

In addition, on May 30, 2004, US 6,712,731 B1 disclosed a multi-degree-of-freedom automatic transmission power transmission system with seven forward gears and one reverse gear. This series of transmissions contains three planetary gear sets with six power shift elements, and two fixed structural connections. The powertrain includes an engine and a torque converter connected to at least one planetary gear assembly, and the output member is connected to a member of another planetary gear set. Six of the power transmission paths provide multiple gear assemblies, fixed connections, interconnections between the input shaft, output shaft and transmission housing, and the speed ratios of seven forward gears and one reverse gear are established through the connection of three clutches .

On October 15, 2013, US 8,556,768 B2 disclosed a multi-speed planetary gear transmission system composed of four planetary gear sets, and achieved eight gear changes through three brakes and three clutches . The first set of planetary gears outputs a rotational speed opposite to that of the input shaft, and the main function of the second set of planetary gears is to output the reverse rotational speed transmitted from the first set of planetary gears or change it back to the forward rotational speed. The combined planetary gear set composed of three groups and the fourth group realizes eight forward gears and one reverse gear.

Although a large number of automatic transmissions using planetary gear structures have been introduced in the prior art, there is still a lot of room for improvement in the prior art considering factors such as the number of gears, transmission ratio range, efficiency, transmission size and weight. Especially in order to increase the number of gears of the automatic transmission, the number of planetary gear sets, clutches and brakes also increases, resulting in an oversized transmission, which is not conducive to the arrangement of the transmission in the vehicle drive train.

Contents of the invention

(1. Purpose

The purpose of the present invention is to provide a multi-speed transmission with a planetary gear structure, which can overcome the difficulties of the prior art, make up for the shortcomings of the current market, and propose a multi-speed transmission with compact structure and convenient for motor vehicles.

(2) Technical solution

The present invention is a multi-speed transmission with a planetary gear structure, which includes a housing, an input member, an output member, the first, second and third planetary gear sets, the first, second, third, fourth, fifth, sixth, Seven interconnecting members and first, second, third, fourth, fifth and sixth torque transmitting devices. The first, second, and third planetary gear sets are arranged sequentially from the input end to the output end; the first, second, third, fourth, fifth, and sixth torque transmission devices include three brakes and three clutches, and the positions between them The connection relationship is: the first, second and third torque transmission devices are located between the second and third planetary gear sets and are juxtaposed close to the housing; the fourth, fifth and sixth torque transmission devices are located between the first and second planetary gear sets Among the groups, the fourth torque transmission device is close to the center of rotation, and the fifth and sixth torque transmission devices are juxtaposed above the fourth torque transmission device. The above-mentioned components are all located in the housing.

The casing is the shell of the planetary gear transmission, which is fixed and used to accommodate and support other components of the transmission. Its shape and structure are determined by the design layout, and there is no universal fixed form.

The input member is the input shaft of the planetary gear transmission, through which the output speed and torque of the engine are input into the transmission of the planetary gear transmission. In this solution, there is only one input member, which is located in front of the first planetary gear set.

The output member is the output shaft of the planetary gear transmission, through which the rotational speed and torque of the planetary gear transmission are output to the subsequent transmission shaft. In this solution, there is only one output member, which is behind the third planetary gear set.

The first planetary gear set is a positive planetary gear set, which is composed of three basic components: the sun gear, the ring gear, and the planet carrier, and the sun gear, the planet carrier, and the ring gear are in sequence from inside to outside among the three. One planet gear meshes externally with the sun gear and the other planet gear meshes internally with the ring gear.

The second planetary gear set is a negative planetary gear set, which is composed of three basic components: the sun gear, the ring gear, and the planet carrier, and the sun gear, the planet carrier, and the ring gear are in sequence between the three, and the planet The gear wheel is externally meshed with the sun gear and internally meshed with the ring gear; similarly, the structure and composition of the third planetary gear set is the same as that of the planetary gear set.

The third planetary gear set is a negative planetary gear set, which is composed of three basic components: the sun gear, the ring gear, and the planet carrier, and the sun gear, the planet carrier, and the ring gear are in sequence between the three, and the planet The gear wheel is externally meshed with the sun gear and internally meshed with the ring gear; similarly, the structure and composition of the second planetary gear set is the same as that of the planetary gear set.

The first interconnecting member is a connecting shaft that fixedly connects the sun gear of the first planetary gear set with the input member.

The second interconnecting member is a connecting shaft that fixedly connects the ring gear of the third planetary gear set with the output member.

The third interconnecting member is a connecting shaft that fixedly connects the first planetary gear set carrier to the second planetary gear set carrier and to the first torque transmitting device.

The fourth interconnecting member is a connecting shaft that connects the second planetary gear set sun gear with the second torque transmitting device.

The fifth interconnecting member is a connecting shaft that connects the third planetary gear set carrier with the third, fourth and fifth torque transmitting devices.

The sixth interconnecting member is a connecting shaft that connects the first planetary gear set ring gear with the fifth and sixth torque transmitting devices.

The seventh interconnecting member is a connecting shaft that fixedly connects the second planetary gear set ring gear to the third planetary gear set sun gear and to the sixth torque transmitting device.

The six torque transmission devices are all wet friction coupling elements, through the engagement of different torque transmission devices, the corresponding two components are connected together and have the same motion state. Each of the six torque transfer devices can be selectively locked to temporarily connect the corresponding two members.

The first torque-transmitting device is selectively lockable to connect the first planetary gear set carrier and the second planetary gear set carrier with the housing.

The second torque-transmitting device is selectively lockable to connect the sun gear of the second planetary gear set with the housing.

The third torque-transmitting device is selectively lockable to connect the carrier of the third planetary gear set with the housing.

The fourth torque-transmitting device is selectively lockable to connect the first planetary gear set sun gear with the third planetary gear set carrier.

A fifth torque-transmitting device is selectively lockable to connect the first planetary gear set ring gear with the third planetary gear set carrier.

The sixth torque-transmitting device is selectively lockable to connect the first planetary gear set ring gear with the third planetary gear set sun gear.

Wherein, the transmission scheme involved in the present invention generates eight forward gears and one reverse gear by controlling the engagement of six torque transmission devices, so as to realize the speed change function.

Wherein, the above-mentioned three planetary gear sets are sequentially the first planetary gear set, the second planetary gear set, the third planetary gear set and the output shaft from the input end; the gears involved in the above-mentioned three sets of planetary gear sets are all helical Toothed.

Wherein, the first, second and third torque transmission devices are friction plate wet brakes.

Wherein, the fourth, fifth and sixth torque transmission devices are friction plate wet clutches.

Wherein, the large and small ring gears of the brake and the clutch need to be calculated according to the output torque of the matching power input device, and the present invention does not limit the specific models and specifications used.

The working principle of the structure of the present invention is summarized as follows: when all the torque transmission devices are in the disengaged state, the degree of freedom of the planetary gear set mechanism is 4, and there is no power transmission between the input member and the output member; when the second, third and fifth torque transmission When the device is in the locked state, the sun gear of the second planetary gear set is fixed, the planet carrier of the third planetary gear set is fixed, the speed of the planet carrier of the first planetary gear set is the same as that of the planet carrier of the third planetary gear set, and the degree of freedom of the planetary gear mechanism When it is reduced to 1, there is power transmission between the input and output members, and the ratio of the rotational speed of the input member to the rotational speed of the output member is the first-gear transmission ratio.

When the first, second, and fifth torque-transmitting devices are locked, the ring gear of the first planetary gear set and the planet carrier of the second planetary gear set are fixed, the sun gear of the second planetary gear set is fixed, and the first planetary gear set The speed of the planet carrier is the same as that of the planet carrier of the third planetary gear set, the degree of freedom of the planetary gear mechanism is reduced to 1, there is power transmission between the input and output members, and the ratio of the speed of the input member to the speed of the output member is the transmission ratio of the second gear.

When the second, fifth, and sixth torque transmission devices are in the locked state, the sun gear of the second planetary gear set is fixed, the planet carrier of the first planetary gear set rotates at the same speed as the planet carrier of the third planetary gear set, and the first planetary gear set The rotation speed of the planet carrier is the same as that of the ring gear of the second planetary gear set and the ring gear of the third planetary gear set, the degree of freedom of the planetary gear mechanism is reduced to 1, there is power transmission between the input and output members, and the ratio of the rotation speed of the input member to the rotation speed of the output member is Three gear ratios.

When the second, fourth, and fifth torque transmission devices are in the locked state, the sun gear of the second planetary gear set is fixed, the sun gear of the first planetary gear set is at the same speed as the planet carrier of the third planetary gear set, and the first planetary gear set The speed of the planet carrier is the same as that of the planet carrier of the third planetary gear set, the degree of freedom of the planetary gear mechanism is reduced to 1, there is power transmission between the input and output members, and the ratio of the speed of the input member to the speed of the output member is the transmission ratio of the fourth gear.

When the fourth, fifth, and sixth torque transmission devices are in the locked state, the sun gear of the first planetary gear set and the planet carrier of the third planetary gear set rotate at the same speed, and the planet carrier of the first planetary gear set and the planet carrier of the third planetary gear set The rotation speed is the same, the first planetary gear set planet carrier and the second planetary gear set ring gear and the third planetary gear set ring gear have the same speed, the degree of freedom of the planetary gear mechanism is reduced to 1, there is power transmission between the input and output members, and the input member The ratio of the rotational speed to the rotational speed of the output member is the fifth gear ratio.

When the second, fourth, and sixth torque transmission devices are in the locked state, the sun gear of the second planetary gear set is fixed, the planet carrier of the first planetary gear set rotates at the same speed as the planet carrier of the third planetary gear set, and the first planetary gear set The rotation speed of the planet carrier is the same as that of the ring gear of the second planetary gear set and the ring gear of the third planetary gear set, the degree of freedom of the planetary gear mechanism is reduced to 1, there is power transmission between the input and output members, and the ratio of the rotation speed of the input member to the rotation speed of the output member is Six gear ratios.

When the first, fourth, and sixth torque-transmitting devices are locked, the ring gear of the first planetary gear set and the planet carrier of the second planetary gear set are fixed, and the planet carrier of the first planetary gear set and the planet carrier of the third planetary gear set The rotation speed is the same, the first planetary gear set planet carrier and the second planetary gear set ring gear and the third planetary gear set ring gear have the same speed, the degree of freedom of the planetary gear mechanism is reduced to 1, there is power transmission between the input and output members, and the input member The ratio of the rotational speed to the rotational speed of the output member is the seventh gear ratio.

When the first, second, and fourth torque-transmitting devices are locked, the ring gear of the first planetary gear set and the planet carrier of the second planetary gear set are fixed, the sun gear of the second planetary gear set is fixed, and the first planetary gear set The rotation speed of the planet carrier is the same as that of the third planetary gear set, the degree of freedom of the planetary gear mechanism is reduced to 1, there is power transmission between the input and output components, and the ratio of the rotation speed of the input component to the rotation speed of the output component is the eighth gear transmission ratio.

When the second, third, and sixth torque transmission devices are in the locked state, the sun gear of the second planetary gear set is fixed, the planet carrier of the third planetary gear set is fixed, and the planet carrier of the first planetary gear set and the second planetary gear set The ring gear and the ring gear of the third planetary gear set have the same speed, the degree of freedom of the planetary gear mechanism is reduced to 1, there is power transmission between the input and output members, and the ratio of the speed of the input member to the speed of the output member is the reverse transmission ratio.

(3) Advantages

The transmission ratios of the corresponding gears can be obtained by simultaneously locking the three torque transmission devices following the shift logic sequence. The power system can realize a total of eight forward gear ratios and one reverse gear ratio, and the shift between adjacent gears All gears meet the simple shifting requirements of only changing one torque transfer device to achieve smooth shifting.

The multi-speed transmission can obtain eight forward gear ratios. After the number of gears in the transmission system is increased, the probability of the engine working under economical conditions is increased, which is conducive to improving the fuel consumption rate; more gears also reduce the The jump of the transmission ratio between adjacent gears is beneficial to reduce the shock of shifting and improve the riding comfort.

In addition, the basic components and torque transmission device of the planetary gear set of the multi-speed transmission have relatively low speed and torque, which is beneficial to reduce the wear between the meshing components, reduce the design size of components and devices, and further reduce the manufacturing cost .

Description of drawings

Fig. 1 is a structural schematic diagram of a specific embodiment of a nine-speed transmission according to the present invention.

reference sign

0 housing

1 first interconnection member

2 Second interconnection member

3 Third interconnection member

4 Fourth interconnection member

5 fifth interconnection member

6 Sixth interconnection member

7 Seventh interconnection member

03 First torque transmitting device

04 Second torque transmitting device

05 Third torque transmitting device

15 Fourth torque transmitting device

56 Fifth torque transmitting device

67 Sixth torque transmitting device

IN input shaft

OUT output shaft

P1 first planetary gear set

P2 second planetary gear set

P3 third planetary gear set

S1 1st planetary gear set sun gear

S2 second planetary gear set sun gear

S3 third planetary gear set sun gear

A1 Planetary carrier of the first planetary gear set

A2 Planetary carrier of the second planetary gear set

A3 Planetary carrier of the third planetary gear set

G1 1st planetary gear set 1st planetary gear

G10 1st planetary gear set 2nd planetary gear

G2 The planet gears of the second planetary gear set mesh with the sun gear

G3 third planetary gear set planetary gear

R1 First planetary gear set ring gear

R2 second planetary gear set ring gear

R3 third planetary gear set ring gear

Detailed ways

The following description is merely exemplary in nature and is in no way intended to limit the invention, application, or uses.

The present invention is a multi-speed transmission with a planetary gear structure, which includes a housing; an input member; an output member; first, second and third planetary gear sets; a first interconnection member; a second interconnection member; a third interconnection connecting member; the fourth interconnecting member; the fifth interconnecting member; the sixth interconnecting member; the seventh interconnecting member and the first, second, third, fourth, fifth and sixth torque transmission devices, between them The position connection relationship is: the first, second, and third planetary gear sets are arranged in sequence from the input end to the output end; the six torque transmission devices include three brakes and three clutches, and the first and second torque transmission devices are located at The second and third planetary gear sets are juxtaposed adjacent to the housing; the third torque-transmitting device is located on the right side of the third planetary gear set on the same side as the output member; the fourth, fifth and sixth torque-transmitting devices are located on the first and sixth Between the two planetary gear sets, the fourth torque transmission device is close to the center of rotation, and the fifth and sixth torque transmission devices are juxtaposed above the fourth torque transmission device. All the above-mentioned components are located in the housing.

First, embodiments of the multi-speed automatic transmission of the present invention have an arrangement of permanent mechanical connections between the elements of the three planetary gear sets. For example, the ring gear of the first planetary gear set is fixedly connected to the planet carrier of the second planetary gear set; the ring gear of the second planetary gear set is fixedly connected to the sun gear of the third planetary gear set. . .

Referring to FIG. 1, the transmission scheme includes an input member IN, a first planetary gear set P1, a second planetary gear set P2, a third planetary gear set P3, a housing 0, an output member OUT, a first torque transmitting device O3, a second Torque transmitting device 04 , third torque transmitting device 05 , fourth torque transmitting device 15 , fifth torque transmitting device 56 and sixth torque transmitting device 67 . In an embodiment of the invention, the three planetary gear sets P1, P2, P3 are all simple planetary gear sets, as described below.

The first planetary gear set P1 includes the first planetary gear set sun gear S1, the first planetary gear set planet carrier A1, the first planetary gear set ring gear R1 and the first planetary gear set planetary gears G1 and G10 (only the a set of planetary gears). The sun gear S1 of the first planetary gear set is fixedly connected with the input member IN through the first interconnection member 1; the ring gear R1 of the first planetary gear set is fixedly connected with the sixth interconnection member 6; the carrier A1 of the first planetary gear set is connected through the first The triple interconnecting member 3 is fixedly connected with the planet carrier A2 of the second planetary gear set P2.

The second planetary gear set P2 includes the second planetary gear set sun gear S2, the second planetary gear set carrier A2, the second planetary gear set R2, the second planetary gear set ring gear R2 and the second planetary gear set planetary gear G2 (only one set of each set of planetary gears is shown). The sun gear S2 of the second planetary gear set P2 is fixedly connected with the fourth interconnection member 4; the planetary carrier A2 of the second planetary gear set P2 is fixedly connected with the planetary carrier A1 of the first planetary gear set P1 through the third interconnection member 3; The ring gear R2 of the planetary gear set P2 is fixedly connected with the sun gear S3 of the third planetary gear set P3 through the seventh interconnecting member 7 .

The third planetary gear set P3 includes the third planetary gear set sun gear S3, the third planetary gear set carrier A3 and the third planetary gear set planetary gear G3 (only one of the planetary gears in this set is shown). The third planetary gear set P3 ring gear R3 is fixedly connected with the output member OUT through the second interconnection member 2; the third planetary gear set P3 planet carrier A3 is connected with the fifth interconnection member 5; the third planetary gear set P3 sun gear S3 It is fixedly connected with the ring gear R2 of the second planetary gear set P2 through the seventh interconnecting member 7 .

Input shaft IN is continuously connected to an engine (not shown) through a torque converter (not shown). Output shaft OUT is continuously connected to a final drive unit or transfer case (not shown).

The first planetary gear set P1 is adjacent to a torque converter (not shown), the second planetary gear set P2 is adjacent to the first planetary gear set P1 , and the third planetary gear set P3 is adjacent to the second planetary gear set P2 .

The shift operation of this embodiment will be described with reference to the shift logic diagram and the transmission ratio of each gear shown in Table 1 in the following column. The transmission is capable of transmitting torque from the input shaft IN to the output shaft OUT in eight forward speed or torque ratios and one reverse speed or torque ratio. With three engagements of the torque-transmitting mechanisms (shift elements), a transmission or torque ratio is achieved for each forward and reverse gear. As shown in Table 1, a truth table for various combinations of torque transmitting mechanisms that are activated or engaged to achieve various gear states. As shown in Table 1, an "x" represents that particular torque transmitting device (shift element) is engaged to achieve the desired gear state. When the fixed transmission ratios of the first planetary gear set P1, the second planetary gear set P2, and the third planetary gear set P3 are respectively 4.0000, -2.0000, -2.2663, the transmission of each gear of the transmission as shown in Table 1 is obtained ratio. For example, a transmission reverse function may be achieved by engaging the second torque-transmitting device 04 , the third torque-transmitting device 05 , and the sixth torque-transmitting device 67 . Similarly, eight forward ratios are achieved through different combinations of shift element engagements, as shown in Table 1.

The foregoing description of the operation and gear states of a six-speed transmission assumes that: firstly, all shift elements specifically mentioned in a given gear state are disengaged; secondly, shifting between adjacent gear states (i.e. During a change of gear state), a shift element that is engaged in both gear states will remain engaged.

The aspects of the invention are merely exemplary in nature and variations that do not depart from the invention are intended to be within the scope of the invention. Such variations are considered without departing from the spirit and scope of the invention.

The calculation method of transmission scheme transmission ratio is as follows:

1 The kinematic equations of the planetary gear mechanism are as follows:

2 Calculate the speed of each shaft, the kinematics formula can be regarded as M×N=A, the calculation method is as follows:

N＝(M ^T ×M) ^-1 ×M ^T ×A

The symbols in the formula are explained as follows:

N is the solution vector

M coefficient matrix

A constant term

n1 Speed of the third interconnecting member

n2 Speed of the fourth interconnection member

n3 Speed of the fifth interconnecting member

n4 Speed of the sixth interconnection member

n5 speed of the seventh interconnection member

n6 Speed of the first interconnecting member

n7 speed of the second interconnection member

i1 Fixed gear ratio of the first planetary gear set

i2 Second planetary gear set fixed gear ratio

i3 Third planetary gear set fixed gear ratio

a First torque-transmitting device engagement factor

b second torque transmitting device engagement factor

c Third torque-transmitting device engagement factor

d fourth torque transmitting device engagement factor

e Fifth torque transmitting device engagement factor

f Sixth torque transmitting device engagement factor

3 Transmission ratio calculation:

Explanation of the symbols in the formula:

i gear ratio

n1 Speed of the third interconnecting member

n2 Speed of the fourth interconnection member

Among them, in order to facilitate the calculation, the rotational speed of the other input shaft IN is 1, and the rotational speeds of other shafts change with the change of the input rotational speed. Through the above three formulas, the rotational speeds of each shaft in different gears and gear ratio.

Table 1 Shift logic matrix of scheme 1

The "x" indicates that the particular torque transmitting device (shift element) is engaged.

Claims (5)

1. A multi-speed transmission with a planetary gear structure, characterized in that: it includes a housing, an input member, an output member, the first, second and third planetary gear sets, the first, second, third, fourth, fifth 1, 6, and 7 interconnecting components and the first, second, third, fourth, fifth, and sixth torque transmission devices; the first, second, and third planetary gear sets are arranged in sequence from the input end to the output end; the first, second, and third The four, five and six torque transmission devices include three brakes and three clutches. The first, second and third torque transmission devices are located between the second and third planetary gear sets and are parallel to the housing; The fifth and sixth torque transmission devices are located between the first and second planetary gear sets, the fourth torque transmission device is close to the center of rotation, the fifth and sixth torque transmission devices are located side by side above the fourth torque transmission device, and the above-mentioned components are located within the housing; The housing is the shell of the planetary gear transmission, which is fixed and used to accommodate and support other components of the transmission, and its shape and structure are determined by the design layout; The input member is the input shaft of the planetary gear transmission, through which the output speed and torque of the engine are input into the transmission of the planetary gear transmission, and there is only one input member in the transmission, which is located in front of the first planetary gear set; The output member is the output shaft of the planetary gear transmission, through which the rotation speed and torque of the planetary gear transmission are output to the subsequent drive shaft, and there is only one output member in the transmission, which is behind the third planetary gear set; The first planetary gear set is a positive planetary gear set, which is composed of three basic components: the sun gear, the ring gear, and the planet carrier, and the sun gear, the planet carrier, and the ring gear are in sequence between the three. One planetary gear of the first planetary gear set is externally meshed with the sun gear, and the other planetary gear is internally meshed with the ring gear; The second planetary gear set is a negative planetary gear set, which is composed of three basic components: the sun gear, the ring gear, and the planet carrier, and the sun gear, the planet carrier, and the ring gear are in sequence from inside to outside among the three. The planetary gears of the second planetary gear set are externally meshed with the sun gear and internally meshed with the ring gear; The third planetary gear set is a negative planetary gear set, which is composed of three basic components: the sun gear, the ring gear, and the planet carrier, and the sun gear, the planet carrier, and the ring gear are in sequence from inside to outside among the three. The planetary gears of the third planetary gear set are externally meshed with the sun gear and internally meshed with the ring gear; The first interconnecting member is a connecting shaft, and the interconnecting member fixedly connects the sun gear of the first planetary gear set with the input member; The second interconnecting member is a connecting shaft, the interconnecting member fixedly connects the ring gear of the third planetary gear set with the output member; The third interconnecting member is a connecting shaft that fixedly connects the carrier of the first planetary gear set with the carrier of the second planetary gear set and is connected to the first torque transmitting device; the fourth interconnecting member is a connecting shaft connecting the second planetary gear set sun gear with the second torque transmitting device; the fifth interconnecting member being a connecting shaft connecting the third planetary gear set carrier with the third, fourth and fifth torque transmitting devices; the sixth interconnecting member is a connecting shaft connecting the first planetary gear set ring gear with the fifth and sixth torque transmitting devices; The seventh interconnecting member is a connecting shaft that fixedly connects the ring gear of the second planetary gear set to the sun gear of the third planetary gear set and to the sixth torque transmitting device; The six torque transmission devices are all wet friction coupling elements, through the engagement of different torque transmission devices, the corresponding two components are connected together and have the same motion state; the six torque transmission devices can be selectively locked , to temporarily connect the corresponding two components; the first torque-transmitting device is selectively lockable to connect the first planetary gear set carrier and the second planetary gear set carrier with the housing; the second torque-transmitting device is selectively lockable to connect the sun gear of the second planetary gear set with the housing; the third torque-transmitting device is selectively lockable to connect the carrier of the third planetary gear set with the housing; the fourth torque-transmitting device is selectively lockable to connect the sun gear of the first planetary gear set with the carrier of the third planetary gear set; a fifth torque-transmitting device selectively lockable to connect the ring gear of the first planetary gear set with the carrier of the third planetary gear set; The sixth torque-transmitting device is selectively lockable to connect the first planetary gear set ring gear with the third planetary gear set sun gear. 2 . The multi-speed transmission with planetary gear structure according to claim 1 , wherein the transmission controls the engagement of six torque transmission devices to generate eight forward gears and one reverse gear to realize the shifting function. 3 . 3. The multi-speed transmission with planetary gear structure according to claim 1, characterized in that: the gears involved in the three sets of planetary gear sets are all helical toothed. 4. A multi-speed transmission with a planetary gear structure according to claim 1, characterized in that: the first, second and third torque transmission devices are friction plate wet brakes, and the fourth, fifth and sixth torque The transmission device is a friction plate wet clutch. 5. A multi-speed transmission with a planetary gear structure according to claim 1, characterized in that: the large and small ring gears of the brake and the clutch need to be calculated according to the torque output by the matched power input device, and there is no limit Specific use models and specifications.