An eight-speed automatic transmission mechanism

Abstract

The present application provides an eight-speed automatic transmission mechanism, including: an input shaft, an output shaft, an 11-bar two-degree-of-freedom separable planetary gear train, a plurality of transmission members, and a torque transmission device. The control of the working states of the clutches and brakes in the eight-speed automatic transmission mechanism of the present application is simple, meeting the "single conversion principle", only requiring a change in the working state of one clutch or brake, and the shifting is simpler and smoother. The eight-speed automatic transmission mechanism of the present application includes four basic planetary gear train units, three clutches, and three brakes, with a simple structure, high transmission efficiency, simple control of the clutches and brakes, no mutual interference between adjacent planetary gears, excellent comprehensive performance, and is beneficial to reducing the size, weight, and manufacturing cost of the automatic transmission.

Description

Technical Field

[0001] This application belongs to the technical field of vehicle transmission mechanisms, and more specifically, relates to an eight-speed automatic transmission mechanism. Background Art

[0002] An automatic transmission is one of the core devices of various automobiles and is the focus of competition among countries around the world. An eight-speed automatic transmission mechanism mainly consists of a planetary gear train, clutches, and brakes. With the improvement of people's living standards, the transmissions of automobiles have gradually switched from manual transmissions to automatic transmissions. The number of gears in automatic transmissions has gradually increased from the early two forward gears to the currently popular six forward gears, eight forward gears, or nine forward gears; the more gears an automatic transmission has, the smoother its gear shifting can be, and the better driving experience the driver can have. Therefore, the development trend of the number of gears in automatic transmissions has always been towards having more gears. Currently, the number of gears in the mainly applied hydraulic automatic transmissions on the market is mostly six, and eight-speed hydraulic automatic transmissions are mainly applied to mid- to high-end models, with the penetration rate showing an increasing trend year by year. At present, in existing eight-speed automatic transmissions, the sun gear and the ring gear are usually directly connected. Since the span between the sun gear and the ring gear is relatively large, the connected part requires a large processing cost and will cause redundant moment of inertia in the connected part, increasing the difficulty of shift control. Summary of the Invention

[0003] The purpose of this application is to provide an eight-speed automatic transmission mechanism to solve the technical problem of difficult shift control in existing eight-speed automatic transmissions.

[0004] To achieve the above purpose, the technical solution adopted in this application is: providing an eight-speed automatic transmission mechanism, including: an input shaft, an output shaft, an 11-bar two-degree-of-freedom separable planetary gear train, multiple transmission members, and a torque transmission device;

[0005] The 11-bar two-degree-of-freedom separable planetary gear train includes a first basic planetary gear train unit, a second basic planetary gear train unit, a third basic planetary gear train unit, and a fourth basic planetary gear train unit installed in sequence from front to back. Each basic planetary gear train unit includes a sun gear, a planet carrier, planet gears, and a ring gear;

[0006] The multiple transmission members include a first member, a second member, a third member, a fourth member, a fifth member, and a sixth member;

[0007] The torque transmission device includes a first clutch, a second clutch, a third clutch, a first brake, a second brake, and a third brake;

[0008] The planet carrier of the first basic planetary gear train unit is fixedly connected to the ring gear of the second basic planetary gear train unit to form the third component; the sun gears of the first basic planetary gear train unit and the second basic planetary gear train unit are fixedly connected to form the second component; the planet carrier of the second basic planetary gear train unit and the sun gear of the third basic planetary gear train unit are fixedly connected to form the fourth component; the planet carrier of the third basic planetary gear train unit and the ring gear of the fourth basic planetary gear train unit are fixedly connected to form the fifth component; the ring gear of the third basic planetary gear train unit and the planet carrier of the fourth basic planetary gear train unit are fixedly connected to form the output component, and the output component is connected to the output shaft;

[0009] The input shaft is respectively connected to the second component, the first component, and the fifth component through the first clutch, the second clutch, the third clutch;

[0010] The second component is connected to the first clutch, the third component is connected to the first brake, and the first component is connected to the second clutch and the second brake; the fifth component is connected to the third clutch, and the sixth component is connected to the third brake;

[0011] Three of the first clutch, the second clutch, the third clutch, the first brake, the second brake, and the third brake are selectively engaged to establish eight forward gear ratios and one reverse gear ratio between the input shaft and the output shaft.

[0012] Further, the input shaft is connected to the vehicle engine through a torque converter.

[0013] Further, the output shaft is connected to the vehicle drive wheels through a differential.

[0014] Further, the first clutch, the second clutch, and the third clutch are wet multi-disc clutches.

[0015] Further, the first brake, the second brake, and the third brake are wet multi-disc brakes.

[0016] Further, the characteristic parameters of the first basic planetary gear train unit, the second basic planetary gear train unit, the third basic planetary gear train unit, and the fourth basic planetary gear train unit are K1 = 1.4, K2 = 1.8, K3 = 1.5, K4 = 3 respectively.

[0017] Further, by engaging the first clutch, the first brake, and the third brake, a first gear transmission ratio is established between the input shaft and the output shaft;

[0018] By engaging the first clutch, the second brake, and the third brake, a second gear ratio is established between the input shaft and the output shaft;

[0019] By engaging the first clutch, the second clutch, and the third brake, a third gear ratio is established between the input shaft and the output shaft;

[0020] By engaging the first clutch, the third clutch, and the third brake, a fourth gear ratio is established between the input shaft and the output shaft;

[0021] By engaging the first clutch, the second clutch, and the third clutch, a fifth gear ratio is established between the input shaft and the output shaft;

[0022] By engaging the first clutch, the third clutch, and the second brake, a sixth gear ratio is established between the input shaft and the output shaft;

[0023] By engaging the first clutch, the third clutch, and the first brake, a seventh gear ratio is established between the input shaft and the output shaft;

[0024] By engaging the third clutch, the first brake, and the second brake, an eighth gear ratio is established between the input shaft and the output shaft;

[0025] By engaging the second clutch, the first brake, and the third brake, a reverse gear ratio is established between the input shaft and the output shaft.

[0026] Compared with the prior art, the present application has the following technical effects:

[0027] In the clutch and brake working state control of an eight-speed automatic transmission mechanism of the present application, it is simple and meets the "single conversion principle". Only the working state of one clutch or brake needs to be changed, and the gearshift is simpler and smoother.

[0028] An eight-speed automatic transmission mechanism of the present application includes four basic planetary gear train units, three clutches, and three brakes. It has a simple structure, high transmission efficiency, simple control of the clutches and brakes, no mutual interference between adjacent planetary gears, excellent comprehensive performance, and is beneficial to reducing the size, weight, and manufacturing cost of the automatic transmission. Brief Description of the Drawings

[0029] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a schematic structural diagram of an eight-speed automatic transmission mechanism provided by an embodiment of the present application.

[0031] Among them, the reference numerals in the figure are as follows:

[0032] 1. First member, 2. First planetary gear, 3. Second member, 4. Third member, 5. Second planetary gear, 6. Fourth member, 7. Third planetary gear, 8. Fifth member, 9. Output member, 10. Fourth planetary gear, 11. Sixth member, 12. Input shaft, 13. Output shaft, C1. First clutch, C2. Second clutch, C3. Third clutch, B1. First brake, B2. Second brake, B3. Third brake, PGT1. First basic planetary gear train unit, PGT2. Second basic planetary gear train unit, PGT3. Third basic planetary gear train unit, PGT4. Fourth basic planetary gear train unit. Detailed implementation manners

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the following further details the present application in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0034] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0035] It should be understood that the orientation or positional relationship indicated by the terms "length", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

[0036] Furthermore, the terms "first", "second", "third", "fourth", and "fifth" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", "third", "fourth", or "fifth" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more, unless otherwise specifically defined.

[0037] Please refer to Figure 1 , and a description will now be given of an eight-speed automatic transmission mechanism provided by an embodiment of this application.

[0038] In an embodiment of this application, an eight-speed automatic transmission mechanism of an embodiment of this application includes: an input shaft 12, an output shaft 13, an 11-bar two-degree-of-freedom separable planetary gear train, a plurality of transmission members, and a torque transmission device.

[0039] The 11-bar two-degree-of-freedom separable planetary gear train of an embodiment of this application includes a first basic planetary gear train unit PGT1, a second basic planetary gear train unit PGT2, a third basic planetary gear train unit PGT3, and a fourth basic planetary gear train unit PGT4 installed in sequence from front to back. Each basic planetary gear train unit (PGT1, PGT2, PGT3, PGT4) includes a sun gear, a planet carrier, planet gears, and a ring gear. Figure 1 Among them, 2, 5, 7, and 10 are the first planet gear, the second planet gear, the third planet gear, and the fourth planet gear of the first basic planetary gear train unit PGT1, the second basic planetary gear train unit PGT2, the third basic planetary gear train unit PGT3, and the fourth basic planetary gear train unit PGT4, respectively. The 11-bar two-degree-of-freedom separable planetary gear train of an embodiment of this application can be separated into two independent six-bar one-degree-of-freedom planetary gear trains. The first basic planetary gear train unit PGT1 and the second basic planetary gear train unit PGT2 form a six-bar one-degree-of-freedom planetary gear train, and the third basic planetary gear train unit PGT3 and the fourth basic planetary gear train unit PGT4 form another six-bar one-degree-of-freedom planetary gear train. This separable planetary gear train is obtained by combining two six-bar one-degree-of-freedom planetary gear trains with simple structures, which can simplify the design structure and is simple and convenient to assemble; in addition, while being able to obtain more gear ratios, the size, weight, and manufacturing cost of the automatic transmission can be reduced.

[0040] The plurality of transmission members of an embodiment of this application include a first member 1, a second member 3, a third member 4, a fourth member 6, a fifth member 8, and a sixth member 11.

[0041] The torque transmission device according to the embodiment of the present application includes a first clutch C1, a second clutch C2, a third clutch C3, a first brake B1, a second brake B2, and a third brake B3.

[0042] The carrier of the first basic planetary gear train unit PGT1 in the embodiment of the present application is fixedly connected to the ring gear of the second basic planetary gear train unit PGT2 to form the same component, that is, the third component 4; the sun gears of the first basic planetary gear train unit PGT1 and the second basic planetary gear train unit PGT2 are fixedly connected to form the same component, that is, the second component 3; the carrier of the second basic planetary gear train unit PGT2 and the sun gear of the third basic planetary gear train unit PGT3 are fixedly connected to form the same component, that is, the fourth component 6; the carrier of the third basic planetary gear train unit PGT3 and the ring gear of the fourth basic planetary gear train unit PGT4 are fixedly connected to form the same component, that is, the fifth component 8; the ring gear of the third basic planetary gear train unit PGT3 and the carrier of the fourth basic planetary gear train unit PGT4 are fixedly connected to form the output component 9, and the output component 9 is connected to the output shaft 13.

[0043] The input shaft 12 in the embodiment of the present application is respectively connected to the second component 3, the first component 1, and the fifth component 8 through the first clutch C1, the second clutch C2, and the third clutch C3. The second component 3, the first component 1, and the fifth component 8 can all be used as input components and are connected to the input shaft 12; the second component 3 is connected to the first clutch C1, the third component 4 is connected to the first brake B1, and the first component 1 is connected to the second clutch C2 and the second brake B2; the fifth component 8 is connected to the third clutch C3, and the sixth component 11 is connected to the third brake B3; three of the first clutch C1, the second clutch C2, the third clutch C3, the first brake B1, the second brake B2, and the third brake B3 are selectively engaged to establish eight forward gear ratios and one reverse gear ratio between the input shaft 12 and the output shaft 13.

[0044] The input shaft 12 in the embodiment of the present application is connected to the vehicle engine through a torque converter, and the power provided by the generator is transmitted to the input shaft 12 through the torque converter.

[0045] The output shaft 13 in the embodiment of the present application is connected to the vehicle drive wheels through a differential, and the output power is transmitted to the vehicle drive wheels.

[0046] The first clutch C1, the second clutch C2, and the third clutch C3 in the embodiment of the present application are wet multi-plate clutches. When the driving plate and the driven plate of the clutch are pressed under the action of hydraulic pressure, the clutch is engaged and in a working state. At this time, the transmission components connected to both ends of the clutch are engaged and have the same rotational speed; conversely, when the clutch is in a non-working state, the transmission components connected to both ends of the clutch are separated and have different rotational speeds.

[0047] The first brake B1, the second brake B2, and the third brake B3 in the embodiments of the present application are wet multi-disc brakes, which are used to connect the transmission member and the transmission housing. When the brakes are in the working state, the transmission member is engaged with the transmission housing, and the transmission member cannot rotate and is in the braking state.

[0048] The characteristic parameters of the first basic planetary gear train unit PGT1, the second basic planetary gear train unit PGT2, the third basic planetary gear train unit PGT3, and the fourth basic planetary gear train unit PGT4 in the embodiments of the present application are K1 = 1.4, K2 = 1.8, K3 = 1.5, and K4 = 3 respectively, so that each gear has a relatively high transmission efficiency. The characteristic parameter K of the basic planetary gear train unit is the tooth number ratio of the ring gear to the sun gear.

[0049] The eight-speed automatic transmission mechanism in the embodiments of the present application can achieve 9 different transmission ratios, that is, 9 gears, including 8 forward gears and 1 reverse gear. Each gear can be achieved by controlling the working states of the clutches and brakes. The transmission ratio of the automatic transmission mechanism is the rotation speed ratio of the input member to the output member.

[0050] Specifically, the following method can be used to achieve 9 different transmission ratios:

[0051] (1) The first gear is a reduction gear with a transmission ratio greater than 1. The first clutch C1, the first brake B1, and the third brake B3 are in the working state, and the other clutches and brakes are in the non-working state. Due to the action of the first clutch C1, the second member 3 and the input shaft 12 rotate together as a whole, and the second member 3 is the input member. Due to the action of the first brake B1 and the third brake B3, the third member 4 and the sixth member 11 are in the braking state, and their rotation speeds are 0. The power is input from the second member 3. In the second basic planetary gear train unit PGT2, the second member 3 drives the second planetary gear 5 to rotate, and then drives the fourth member 6 to rotate; in the third basic planetary gear train unit PGT3, the fourth member 6 drives the third planetary gear 7 to rotate, and then drives the fifth member 8 to rotate; in the fourth basic planetary gear train unit PGT4, the fifth member 8 drives the fourth planetary gear 10 to rotate. At this time, the third planetary gear 7 and the fourth planetary gear 10 rotate together to drive the output member 9 to rotate, and the power is transmitted to the output member 9. The rotation speed of the output member 9 is less than that of the second member 3, and it is in the lower first gear.

[0052] (2) The second gear is a reduction gear with a transmission ratio greater than 1. The first clutch C1, the second brake B2, and the third brake B3 are in the working state, and other clutches and brakes are in the non-working state. Due to the action of the first clutch C1, the second member 3 and the input shaft 12 rotate together as a whole, and the second member 3 is the input member. Due to the action of the second brake B2 and the third brake B3, the first member 1 and the sixth member 11 are in the braking state, and their rotational speeds are 0. In the first basic planetary gear train unit PGT1, the second member 3 drives the first planetary gear 2 to rotate, and then drives the third member 4 to rotate; in the second basic planetary gear train unit PGT2, the third member 4 and the second member 3 jointly drive the second planetary gear 5 to rotate, and then drive the fourth member 6 to rotate; in the third basic planetary gear train unit PGT3, the fourth member 6 drives the third planetary gear 7 to rotate, and then drives the fifth member 8 to rotate; in the fourth basic planetary gear train unit PGT4, the fifth member 8 drives the fourth planetary gear 10 to rotate. At this time, the third planetary gear 7 and the fourth planetary gear 10 rotate together to drive the output member 9 to rotate, and transmit the power to the output member 9. The rotational speed of the output member 9 is less than that of the second member 3, and it is in the second gear with a higher rotational speed than the first gear.

[0053] (3) The third gear is a reduction gear with a transmission ratio greater than 1. The first clutch C1, the second clutch C2, and the third brake B3 are in the working state, and other clutches and brakes are in the non-working state. Due to the action of the first clutch C1 and the second clutch C2, the second member 3 and the first member 1 are both input members, and the power is simultaneously input from the second member 3 and the first member 1 to drive the first basic planetary gear train unit PGT1 and the second basic planetary gear train unit PGT2 to rotate as a whole, thereby driving the fourth member 6 to rotate, and the rotational speed of the fourth member 6 is equal to that of the input shaft. Due to the action of the third brake B3, the sixth member 11 is in the braking state, and its rotational speed is 0. In the third basic planetary gear train unit PGT3, the fourth member 6 drives the third planetary gear 7 to rotate, and then drives the fifth member 8 to rotate; in the fourth basic planetary gear train unit PGT4, the fifth member 8 drives the fourth planetary gear 10 to rotate. At this time, the third planetary gear 7 and the fourth planetary gear 10 rotate together to drive the output member 9 to rotate, and transmit the power to the output member 9. The rotational speed of the output member 9 is less than that of the second member 3 and the first member 1, and it is in the third gear with a higher rotational speed than the second gear.

[0054] (4) The fourth gear is a reduction gear with a transmission ratio greater than 1. The first clutch C1, the third clutch C3, and the third brake B3 are in the working state, and other clutches and brakes are in the non-working state. Due to the actions of the first clutch C1 and the third clutch C3, the second member 3 and the fifth member 8 are both input members, and power is transmitted from the second member 3 and the fifth member 8. Due to the action of the third brake B3, the sixth member 11 is in the braking state with a rotational speed of 0. In the fourth basic planetary gear train unit PGT4, the fifth member 8 drives the fourth planetary gear 10 to rotate, and then drives the output member 9 to rotate, transmitting power to the output member 9. The rotational speed of the output member 9 is less than that of the fifth member 8, and it is in the fourth gear with a higher rotational speed than the third gear.

[0055] (5) The fifth gear is a direct gear with a transmission ratio equal to 1. The first clutch C1, the second clutch C2, and the third clutch C3 are in the working state, and other brakes are in the non-working state. Due to the actions of the first clutch C1, the second clutch C2, and the third clutch C3, the second member 3, the first member 1, and the fifth member 8 are all input members, and power is simultaneously transmitted from the second member 3, the first member 1, and the fifth member 8, driving the entire mechanism to rotate as a whole. Therefore, the rotational speeds of the input member and the output member are the same, and it is in the direct gear.

[0056] (6) The sixth gear is an overdrive gear with a transmission ratio less than 1. The first clutch C1, the third clutch C3, and the second brake B2 are in the working state, and other clutches and brakes are in the non-working state. Due to the actions of the first clutch C1 and the third clutch C3, the second member 3 and the fifth member 8 are both input members. Due to the action of the second brake B2, the first member 1 is in the braking state with a rotational speed of 0. In the first basic planetary gear train unit PGT1, the second member 3 drives the first planetary gear 2 to rotate, and then drives the third member 4 to rotate; in the second basic planetary gear train unit PGT2, the third member 4 and the second member 3 jointly drive the second planetary gear 5 to rotate, and then drive the fourth member 6 to rotate; in the third basic planetary gear train unit PGT3, the fourth member 6 and the fifth member 8 jointly drive the third planetary gear 7 to rotate, and then drive the output member 9 to rotate, transmitting power to the output member 9. The rotational speed of the output member 9 is greater than that of the second member 3 and the fifth member 8, and it is in the sixth gear with a higher rotational speed.

[0057] (7) The seventh gear is an overdrive gear with a transmission ratio less than 1. The first clutch C1, the third clutch C3, and the first brake B1 are in the working state, and other clutches and brakes are in the non-working state. Due to the actions of the first clutch C1 and the third clutch C3, the second member 3 and the fifth member 8 are both input members, and power is input from the second member 3 and the fifth member 8. Due to the action of the first brake B1, the third member 4 is in the braking state with a rotational speed of 0. In the second basic planetary gear train unit PGT2, the second member 3 drives the second planetary gear 5 to rotate, and then drives the fourth member 6 to rotate; in the third basic planetary gear train unit PGT3, the fourth member 6 and the fifth member 8 jointly drive the third planetary gear 7 to rotate, and then drive the output member 9 to rotate, transmitting the power to the output member 9. The rotational speed of the output member 9 is greater than the rotational speeds of the second member 3 and the fifth member 8, and it is in the seventh gear with a higher rotational speed than the sixth gear.

[0058] (8) The eighth gear is an overdrive gear with a transmission ratio less than 1. The third clutch C3, the first brake B1, and the second brake B2 are in the working state, and other clutches and brakes are in the non-working state. Due to the action of the third clutch C3, the fifth member 8 and the input shaft 12 rotate together as a whole, and the fifth member 8 is the input member, and power is input from the fifth member 8. Due to the actions of the first brake B1 and the second brake B2, the third member 4 and the first member 1 are in the braking state. At this time, both the first basic planetary gear train unit PGT1 and the second basic planetary gear train unit PGT2 are in the braking state with a rotational speed of 0. In the third basic planetary gear train unit PGT3, the fifth member 8 drives the third planetary gear 7 to rotate, and then drives the output member 9 to rotate, transmitting the power to the output member 9. The rotational speed of the output member 9 is greater than the rotational speed of the fifth member 8, and it is in the eighth gear with a higher rotational speed than the seventh gear.

[0059] (9) The 9th gear is the reverse gear. The second clutch C2, the first brake B1, and the third brake B3 are in the working state, and the other clutches and brakes are in the non - working state. Due to the action of the second clutch C2, the first member 1 and the input shaft 12 rotate together as a whole. The first member 1 is the input member, and the power is input from the first member 1. Due to the action of the first brake B1 and the third brake B3, the third member 4 and the sixth member 11 are in the braking state with a rotational speed of 0. In the first basic planetary gear train unit PGT1, the first member 1 drives the first planetary gear 2 to rotate, and then drives the second member 3 to rotate; in the second basic planetary gear train unit PGT2, the second member 3 drives the second planetary gear 5 to rotate, and then drives the fourth member 6 to rotate; in the third basic planetary gear train unit PGT3, the fourth member 6 drives the third planetary gear 7 to rotate, and then drives the fifth member 8 to rotate; in the fourth basic planetary gear train unit PGT4, the fifth member 8 drives the fourth planetary gear 10 to rotate. At this time, the third planetary gear 7 and the fourth planetary gear 10 rotate together, driving the output member 9 to rotate, and transmitting the power to the output member 9. The rotational speed direction of the output member 9 is opposite to that of the first member 1, being in the reverse gear.

[0060] The relationships between the transmission ratios and characteristic parameters of each gear in the embodiments of this application are shown in Table 1.

[0061] Table 1 Relationships between the transmission ratios and characteristic parameters of the mechanism

[0062]

[0063] To make each gear have a relatively high transmission efficiency, the characteristic parameters of the four basic planetary gear train units in the mechanism are respectively K1 = 1.4, K2 = 1.8, K3 = 1.5, and K4 = 3. Calculated from the relationships between the transmission ratios and characteristic parameters of the mechanism in Table 1, the transmission ratios of each gear are respectively 5.1, 2.9, 1.8, 1.3, 1, 0.8, 0.7, 0.6, - 3.7. The implementation methods of each gear are summarized in Table 2.

[0064] Table 2 Implementation methods of the 9 gears of the mechanism

[0065]

[0066] “ - ” in the table indicates “none”.

[0067] An eight-speed automatic transmission mechanism according to an embodiment of the present application is composed of an 11-bar two-degree-of-freedom separable planetary gear train (PGT1, PGT2, PGT3, PGT4), three clutches (C1, C2, C3), three brakes (B1, B2, B3), an input shaft 12 and an output shaft 13. The working state control of the clutches and brakes in the embodiment of the present application is simple and meets the "single conversion principle", that is, when switching between two adjacent forward gears, only the working state of one clutch or brake needs to be changed, and the gearshift is simpler and smoother.

[0068] An eight-speed automatic transmission mechanism according to an embodiment of the present application includes four basic planetary gear train units, three clutches and three brakes, has a simple structure, high transmission efficiency, simple control of the clutches and brakes, no mutual interference between adjacent planetary gears, has excellent comprehensive performance, and is beneficial to reducing the size, weight and manufacturing cost of the automatic transmission.

[0069] The above embodiments only represent several implementation manners of the present application, and the description thereof is relatively specific and detailed, but should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. An eight-speed automatic transmission mechanism, characterized in that Comprising: An input shaft, an output shaft, an 11-bar two-degree-of-freedom separable planetary gear train, a plurality of transmission members, and a torque transmission device; The 11-bar two-degree-of-freedom separable planetary gear train includes a first basic planetary gear train unit, a second basic planetary gear train unit, a third basic planetary gear train unit, and a fourth basic planetary gear train unit sequentially installed from front to back. Each of the basic planetary gear train units includes a sun gear, a planet carrier, planetary gears, and a ring gear; The plurality of transmission members includes a first member, a second member, a third member, a fourth member, a fifth member, and a sixth member; The torque transmission device includes a first clutch, a second clutch, a third clutch, a first brake, a second brake, and a third brake; The planet carrier of the first basic planetary gear train unit is fixedly connected to the ring gear of the second basic planetary gear train unit to form the third member; the sun gear of the first basic planetary gear train unit and the sun gear of the second basic planetary gear train unit are fixedly connected to form the second member; the planet carrier of the second basic planetary gear train unit and the sun gear of the third basic planetary gear train unit are fixedly connected to form the fourth member; the planet carrier of the third basic planetary gear train unit and the ring gear of the fourth basic planetary gear train unit are fixedly connected to form the fifth member; The ring gear of the third basic planetary gear train unit and the planet carrier of the fourth basic planetary gear train unit are fixedly connected to form an output member, and the output member is connected to the output shaft; The input shaft is respectively connected to the first clutch, the second clutch, the third clutch, the second member, the first member, and the fifth member; The second member is connected to the first clutch, the third member is connected to the first brake, and the first member is connected to the second clutch and the second brake; The fifth member is connected to the third clutch, and the sixth member is connected to the third brake; Three of the first clutch, the second clutch, the third clutch, the first brake, the second brake, and the third brake are selectively engaged to establish eight forward gear ratios and one reverse gear ratio between the input shaft and the output shaft; The first member is fixedly connected to the ring gear of the first basic planetary gear train unit, and the sixth member is fixedly connected to the sun gear of the fourth basic planetary gear train unit.

2. The eight-speed automatic transmission mechanism according to claim 1, characterized in that The input shaft is connected to a vehicle engine through a torque converter.

3. An eight-speed automatic transmission mechanism according to claim 1, characterized in that, The output shaft is connected to vehicle drive wheels through a differential.

4. An eight-speed automatic transmission mechanism according to claim 1, characterized in that, The first clutch, the second clutch, and the third clutch are wet multi-plate clutches.

5. An eight-speed automatic transmission mechanism according to claim 1, characterized in that, The first brake, the second brake, and the third brake are wet multi-plate brakes.

6. An eight-speed automatic transmission mechanism according to any one of claims 1-5, characterized in that, The characteristic parameters of the first basic planetary gear train unit, the second basic planetary gear train unit, the third basic planetary gear train unit, and the fourth basic planetary gear train unit are K1 = 1.4, K2 = 1.8, K3 = 1.5, and K4 = 3 respectively.

7. The eight-speed automatic transmission mechanism according to claim 6, wherein By engaging the first clutch, the first brake, and the third brake, a first gear ratio is established between the input shaft and the output shaft; By engaging the first clutch, the second brake, and the third brake, a second gear ratio is established between the input shaft and the output shaft; By engaging the first clutch, the second clutch, and the third brake, a third gear ratio is established between the input shaft and the output shaft; By engaging the first clutch, the third clutch, and the third brake, a fourth gear ratio is established between the input shaft and the output shaft; By engaging the first clutch, the second clutch, and the third clutch, a fifth gear ratio is established between the input shaft and the output shaft; By engaging the first clutch, the third clutch, and the second brake, a sixth gear ratio is established between the input shaft and the output shaft; By engaging the first clutch, the third clutch, and the first brake, a seventh gear ratio is established between the input shaft and the output shaft; By engaging the third clutch, the first brake, and the second brake, an eighth gear ratio is established between the input shaft and the output shaft; By engaging the second clutch, the first brake, and the third brake, a reverse gear ratio is established between the input shaft and the output shaft.

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