Transmission for electric vehicle and control method thereof

Abstract

The present invention provides a transmission for an electric vehicle. The transmission for an electric vehicle may include: a first planetary gear set; a first motor configured to input power to a first rotating element of the first planetary gear set; a differential configured to receive power output from a second rotating element of the first planetary gear set; a second motor configured to selectively provide power to a third rotating element of the first planetary gear set; a second planetary gear set including a first rotating element directly connected to the differential and a second rotating element configured to selectively receive power from the second motor; and a third planetary gear set including a third rotating element directly connected to the third rotating element of the second planetary gear set, a fixed second rotating element, and a first rotating element directly connected to a selected output shaft of the differential.

Description

Technical Field

[0001] The present invention relates to a transmission that can be installed in an electric vehicle and a control method thereof. Background Art

[0002] An electric vehicle, which is a vehicle provided with the power of an electric motor as a driving force, does not emit exhaust gas and thus can contribute to reducing environmental pollution in large cities.

[0003] Improvements in various technologies are required to achieve popularization of electric vehicles, and in particular, a technology capable of significantly increasing the driving distance on one charge is required.

[0004] To increase driving distance, it is necessary to achieve the maximum climbing performance and maximum speed performance required of the vehicle while improving energy efficiency (driving distance per unit power, km / kWh) by reducing the size and capacity of the motor installed in the electric vehicle. To this end, a transmission is installed in the electric vehicle.

[0005] For the above reasons, a transmission mounted in an electric vehicle has a simple structure, does not cause shift shock, and generates little heat.

[0006] The information disclosed in this Background section of the present invention is only for enhancement of understanding of the general background of the present invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art. Summary of the Invention

[0007] Various aspects of the present invention are directed to providing a transmission for an electric vehicle and a control method thereof, wherein the transmission for an electric vehicle is configured to provide multiple speed ratios to reduce the capacity of a motor, achieve maximum climbing performance and maximum speed performance required of the vehicle, improve the energy efficiency of the vehicle with a relatively simple structure and small weight, prevent gear shift shock, significantly reduce heat generation, and implement a torque vectoring function to improve the high-speed cornering performance of the vehicle.

[0008] According to an exemplary embodiment of the present invention, a transmission for an electric vehicle includes: a first planetary gear set; a first motor, configured to input power to a first rotating element of the first planetary gear set; a differential, configured to receive power output from a second rotating element of the first planetary gear set; a second motor, configured to selectively provide power to a third rotating element of the first planetary gear set; a second planetary gear set, including a first rotating element connected to a differential housing of the differential and a second rotating element configured to selectively receive power from the second motor; and a third planetary gear set, including a third rotating element connected to the third rotating element of the second planetary gear set, a fixed second rotating element and a first rotating element connected to a selected output shaft, the selected output shaft being any one of the output shafts of the differential.

[0009] A first clutch and a second clutch can be connected to the first planetary gear set, the first clutch being configured to selectively connect the third rotating element of the first planetary gear set to the transmission housing, and the second clutch being configured to directly connect two of the three rotating elements of the first planetary gear set to each other.

[0010] The first planetary gear set may include a first sun gear directly connected to the first motor as an input element, a first planet carrier directly connected to the differential housing as an output element, and a first ring gear connected to the first clutch, and the second clutch may connect the first sun gear and the first ring gear to each other.

[0011] The second motor may be connected to the first ring gear of the first planetary gear set via a third clutch.

[0012] The second rotation element of the second planetary gear set may be connected to the second motor via a fourth clutch.

[0013] The ratio of the number of teeth of the second sun gear of the second planetary gear set to the number of teeth of the second ring gear of the second planetary gear set and the ratio of the number of teeth of the third sun gear of the third planetary gear set to the number of teeth of the third ring gear of the third planetary gear set may be the same as each other.

[0014] According to various exemplary embodiments of the present invention, a transmission for an electric vehicle includes: a first planetary gear set; a first motor, configured to input power to a first rotating element of the first planetary gear set; a differential, configured to receive power output from a second rotating element of the first planetary gear set; a second motor, configured to selectively provide power to a third rotating element of the first planetary gear set; and a compound planetary gear set, installed between a differential case and a selected output shaft of the differential to distribute the power provided from the second motor to the differential case and the selected output shaft, and to make the directions of the torque distributed to the differential case and the selected output shaft opposite to each other, the selected output shaft being any one of the output shafts of the differential.

[0015] The compound planetary gear set may include: a second planetary gear set, including a first rotating element connected to the differential housing of the differential and a second rotating element configured to be connected to the second motor; and a third planetary gear set, including a third rotating element connected to the third rotating element of the second planetary gear set, a fixed second rotating element and a first rotating element connected to a selected output shaft.

[0016] According to various exemplary embodiments of the present invention, a transmission for an electric vehicle includes two or more motors, two or more clutches and one or more planetary gear sets and has two or more gears, wherein a first motor is connected to a first rotating element of a first planetary gear set, a third rotating element of the first planetary gear set is selectively connected to a transmission housing via a first clutch, a second rotating element of the first planetary gear set is connected to an output shaft, a second motor is connected to the third rotating element of the first planetary gear set, including a second clutch connecting any two elements of the first planetary gear set, and allowing transmission control by the second motor.

[0017] The second motor may be always connected to the third rotation element of the first planetary gear set via a speed reducer.

[0018] According to various exemplary embodiments of the present invention, a control method for a transmission of an electric vehicle includes: in a low-speed driving state in which the first clutch is engaged and the first motor is driven, the controller releases the first clutch after controlling the second motor to provide the same torque as the torque of the third rotating element of the first planetary gear set supported by the first clutch to the third rotating element of the first planetary gear set; the controller reduces the speed of the first motor and increases the speed of the second motor while maintaining the torque of the first motor and the torque of the second motor constant so that the speeds of the three rotating elements of the first planetary gear set are synchronized with each other; and after engaging the second clutch, the controller releases the torque of the second motor while maintaining the speed of the first motor to form a high-speed driving state.

[0019] The controller may engage the third clutch before providing torque from the second motor to the third rotation element of the first planetary gear set, and release the third clutch after engaging the second clutch.

[0020] After engaging the fourth clutch, the controller may be configured to control the second motor to apply torque in opposite directions to the differential case and the selected output shaft to perform torque vectoring control.

[0021] The control method may further include: in a high-speed driving state in which the second clutch is engaged and the first motor is driven, the controller releases the second clutch after increasing the torque of the second motor to the first clutch torque while maintaining the speed of the first motor; the controller reduces the speed of the second motor to 0 and increases the speed of the first motor while maintaining the torque of the first motor and the torque of the second motor constant; and the controller releases the torque of the second motor after engaging the first clutch to form a low-speed driving state.

[0022] The controller may engage the third clutch before releasing the second clutch and increasing the torque of the second motor, and release the third clutch after releasing the torque of the second motor.

[0023] After engaging the fourth clutch, the controller may be configured to control the second motor to apply torque in opposite directions to the differential case and the selected output shaft to perform torque vectoring control.

[0024] According to various exemplary embodiments of the present invention, a control method for a transmission of an electric vehicle includes: in a low-speed driving state in which the first clutch is engaged and the first motor is driven, the controller releases the first clutch after controlling the second motor to provide the same torque as the torque of the third rotating element of the first planetary gear set supported by the first clutch to the third rotating element of the first planetary gear set; the controller reduces the speed of the first motor and increases the speed of the second motor while maintaining the torque of the first motor and the torque of the second motor constant so that the speeds of the three rotating elements of the first planetary gear set are synchronized with each other; and after engaging the second clutch, the controller releases the torque of the second motor while maintaining the speed of the first motor to form a high-speed driving state.

[0025] The control method may further include: in a high-speed driving state in which the second clutch is engaged and the first motor is driven, the controller releases the second clutch after increasing the torque of the second motor to the first clutch torque while maintaining the speed of the first motor; the controller reduces the speed of the second motor to 0 and increases the speed of the first motor while maintaining the torque of the first motor and the torque of the second motor constant; and the controller releases the torque of the second motor after engaging the first clutch to form a low-speed driving state.

[0026] The method and apparatus of the present invention have other features and advantages that will become apparent or set forth in more detail in the accompanying drawings and the following detailed description, which are incorporated herein and which together serve to explain certain principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of a transmission for an electric vehicle according to an exemplary embodiment of the present invention;

[0028] Figure 2 is a description Figure 1 a table of transmission operating modes;

[0029] Figure 3 It shows Figure 1 Flowchart of a method for controlling a transmission to shift from a low gear to a high gear;

[0030] Figure 4 It shows Figure 1 The motor characteristic diagram of the transmission shifting from low gear to high gear;

[0031] Figure 5 It is shown in Figure 3 Table showing the torque change process of the motor and clutch during the gear shift process;

[0032] Figure 6 is a description Figure 1 A curve diagram of the process of the transmission shifting from a low gear to a high gear;

[0033] Figure 7 It shows Figure 1 Flowchart of a method for controlling a transmission to shift from a high speed gear to a low speed gear;

[0034] Figure 8 It shows Figure 1 The motor characteristic diagram of the transmission shifting from high gear to low gear;

[0035] Figure 9 It is shown in Figure 7 Table showing the torque change process of the motor and clutch during the gear shift process;

[0036] Figure 10 It shows Figure 1 a table showing the rotational speed of each section of the transmission when the fourth clutch is engaged and the second motor is stopped;

[0037] Figure 11 It shows Figure 1 a table showing the rotational speed of each section in the transmission in a state in which the fourth clutch is engaged and the second motor is driven at a speed of 100 RPM;

[0038] Figure 12 By using the lever diagram of the second planetary gear set and the third planetary gear set Figure 10 Status and Figure 11 A diagram describing the torque vectoring control function by comparing the states of FIG.

[0039] Figure 13 is a schematic diagram of a transmission for an electric vehicle according to another exemplary embodiment of the present invention;

[0040] Figure 14 According to an exemplary embodiment of the present invention Figure 13 A schematic diagram of adding a speed reducer to the transmission in FIG; and

[0041] Figure 15 It is for the sake of Figure 6 A diagram describing a process of shifting from a low gear to a high gear in a general transmission for an electric vehicle according to the prior art is provided by comparison with a graph of .

[0042] It should be understood that the accompanying drawings are not necessarily drawn to scale and present a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as incorporated herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

[0043] In the drawings, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. DETAILED DESCRIPTION

[0044] With reference now to various embodiments of the present invention in detail, examples of embodiments are shown in the accompanying drawings and are described below. Although the present invention will be described in conjunction with exemplary embodiments of the present invention, it will be understood that this description is not intended to limit the present invention to those exemplary embodiments. On the other hand, the present invention is intended not only to encompass exemplary embodiments of the present invention, but also to encompass various alternatives, modifications, equivalents and other embodiments that may be included within the thought and scope of the present invention as defined by the appended claims.

[0045] Hereinafter, a transmission for an electric vehicle and a control method thereof according to exemplary embodiments of the present invention are described with reference to the accompanying drawings.

[0046] Reference Figure 1, a transmission for an electric vehicle according to an exemplary embodiment of the present invention includes: a first planetary gear set PG1; a first motor MG1, which inputs power to a first rotating element of the first planetary gear set PG1; a differential DF, which receives power output from a second rotating element of the first planetary gear set PG1; a second motor MG2, which provides power to a third rotating element of the first planetary gear set PG1; and a compound planetary gear set CG, which is installed between a differential case of the differential DF and a selected output shaft as any one of the output shafts of the differential DF to distribute the power provided from the second motor MG2 to the differential case and the selected output shaft, and to make the directions of the torques distributed to the differential case and the selected output shaft opposite to each other.

[0047] That is, according to an exemplary embodiment of the present invention, the output speed of the power input from the first motor MG1 is changed by the first planetary gear set PG1, and then the power can be output through the differential DF, the second motor MG2 applies appropriate torque to the third rotating element of the first planetary gear set PG1 to achieve smooth shifting without shifting shock, and the power provided from the second motor MG2 is distributed through the compound planetary gear set CG to implement a torque vectoring control function.

[0048] Note that the output shafts of the differential DF are respectively provided with a right output shaft OR and a left output shaft OL, and the output shaft selected from the right output shaft OR and the left output shaft OL to receive the power supplied from the second motor MG2 is referred to as a "selected output shaft". Figure 1 A case where the right output shaft OR is the selected output shaft is shown, but according to an exemplary embodiment of the present invention, the left output shaft OL may of course also become the selected output shaft.

[0049] A first clutch CL1 , which may fix the third rotation element to the transmission case CS, and a second clutch CL2 , which may directly connect two of the three rotation elements to each other, are connected to the first planetary gear set PG1 .

[0050] That is, the first planetary gear set PG1 includes a first sun gear S1 directly connected to the first motor MG1 as an input element, a first planet carrier C1 directly connected to the differential DF as an output element, and a first ring gear R1 connected to the first clutch CL1, and the second clutch CL2 can connect the first sun gear S1 and the first ring gear R1 to each other.

[0051] In the first planetary gear set PG1, switching can be performed between a state in which the output speed of power is reduced through the first planetary carrier C1 when the first sun gear S1 is driven by the first motor MG1 in a state in which the first clutch CL1 is engaged to fix the first ring gear R1 and the power is output through the differential DF, and a state in which the first clutch CL1 is released and the second clutch CL2 is engaged to rotate all the rotating elements of the first planetary gear set PG1 together so that the power transmitted from the first motor MG1 is output as is through the differential DF, so that the input power can be output at a speed equal to or less than a predetermined speed.

[0052] Meanwhile, the second motor MG2 may be connected to the first ring gear R1 of the first planetary gear set PG1 through the third clutch CL3 to selectively transmit power to the first ring gear R1.

[0053] The compound planetary gear set CG includes: a second planetary gear set PG2, including a first rotating element directly connected to the differential housing of the differential DF and a second rotating element receiving power from the second motor MG2; and a third planetary gear set PG3, including a third rotating element directly connected to the third rotating element of the second planetary gear set PG2, a second rotating element fixed to the transmission housing CS, and a first rotating element directly connected to the selected output shaft.

[0054] That is to say, according to Figure 1 In an exemplary embodiment, it can be considered that the second planetary gear set PG2 forming the compound planetary gear set CG is constructed to distribute the power provided from the second motor MG2 to the differential case and the selected output shaft, and the third planetary gear set PG3 is constructed to reverse the direction of the power distributed to the selected output shaft so that the directions of the torque distributed to the differential case and the selected output shaft are opposite to each other.

[0055] The second carrier C2 as the second rotation element of the second planetary gear set PG2 is connected to the second motor MG2 through the fourth clutch CL4, and the third carrier C3 as the second rotation element of the third planetary gear set PG3 is fixed to the transmission case CS.

[0056] In addition, the ratio of the number of teeth of the second sun gear S2 of the second planetary gear set PG2 to the number of teeth of the second ring gear R2 of the second planetary gear set PG2 and the ratio of the number of teeth of the third sun gear S3 of the third planetary gear set PG3 to the number of teeth of the third ring gear R3 of the third planetary gear set PG3 are set to be the same as each other.

[0057] According to an exemplary embodiment of the present invention, the second planetary gear set PG2 and the third planetary gear set PG3 are implemented by substantially identical planetary gear sets having the same number of teeth of gears as each other.

[0058] Note that, Figure 1 The controller CLR in the ECU 2 may control the first motor MG1 , the second motor MG2 , the first clutch CL1 , the second clutch CL2 , the third clutch CL3 , and the fourth clutch CL4 , and may be implemented by a transmission control unit (TCU) or the like.

[0059] Figure 13 A transmission for an electric vehicle according to another exemplary embodiment of the present invention is shown. The transmission is a transmission for an electric vehicle that includes two or more motors, two or more clutches, and one or more planetary gear sets and has two or more gear positions. The transmission has the following configuration: a first motor MG1 is connected to a first rotating element of a first planetary gear set PG1; a third rotating element of the first planetary gear set PG1 is selectively connected to a transmission case CS via a first clutch CL1; a second rotating element of the first planetary gear set PG1 is connected to an output shaft OUT; a second motor MG2 is always connected to the third rotating element of the first planetary gear set PG1; a second clutch CL2 is included that connects any two elements of the first planetary gear set PG1; and transmission control can be performed via the second motor MG2.

[0060] In fact, it can be considered that according to Figure 13 The configuration of the exemplary embodiment is based on Figure 1 The configuration of the exemplary embodiment is different in that the compound planetary gear set CG is removed and the second motor MG2 is directly connected to the first planetary gear set PG1. The first rotating element of the first planetary gear set is the first sun gear S1, the second rotating element is the first planet carrier C1, and the third rotating element is the first ring gear R1.

[0061] Figure 14 A transmission for an electric vehicle according to another exemplary embodiment of the present invention is shown. Figure 14 The configuration of the exemplary embodiment is based on Figure 13 The configurations of the exemplary embodiments are substantially the same as each other. Figure 14 The configuration of the exemplary embodiment is based on Figure 13 The configuration of the exemplary embodiment of FIG. 5 is different only in that the second motor MG2 is always connected to the third rotation element of the first planetary gear set PG1 through the speed reducer.

[0062] In addition to the above differences, Figure 13 and Figure 14 An exemplary embodiment of Figure 1 The exemplary embodiments of the present invention are basically the same, so the description of Figure 13 and Figure 14 A detailed description of exemplary embodiments of the present invention is provided.

[0063] The description is performed as Figure 1 A process of transmission control of a transmission for an electric vehicle according to an exemplary embodiment of the present invention is shown constructed as shown.

[0064] Reference Figure 3 、 Figure 4 、 Figure 5 and Figure 6 , a control method for shifting a transmission from a low-speed gear (first gear) to a high-speed gear (second gear) includes: in a low-speed driving state in which the first clutch CL1 is engaged and the first motor MG1 is driven, the controller CLR releases the first clutch CL1 after controlling the second motor MG2 to provide the same torque as the third rotating element of the first planetary gear set PG1 supported by the first clutch CL1 to the third rotating element of the first planetary gear set PG1 (S10); the controller CLR reduces the speed of the first motor MG1 and increases the speed of the second motor MG2 while maintaining the torque of the first motor MG1 and the torque of the second motor MG2 constant so that the speeds of the three rotating elements of the first planetary gear set PG1 are synchronized with each other (S20); and after the controller CLR engages the second clutch CL2, releases the torque of the second motor MG2 while maintaining the speed of the first motor MG1 to form a high-speed driving state (S30).

[0065] Hereinafter, this process will be described in more detail.

[0066] In the first speed state corresponding to the low gear, when the first clutch CL1 is engaged, the output speed of the power provided from the first motor MG1 to the first sun gear S1 is reduced, and the power is output to the differential DF through the first planetary carrier C1, so the first clutch CL1 fixes the first ring gear R1 of the first planetary gear set PG1.

[0067] At this time, if Figure 4 As shown, the first motor MG1 provides a torque T_MG1a that is relatively smaller than T_MG1b to the first sun gear S1.

[0068] To shift to the second speed state corresponding to a high gear, the torque applied to the first ring gear R1 to release the first clutch CL1 while maintaining the state of the first ring gear R1 fixed is referred to as "first clutch torque T_CL1." The second motor MG2 is controlled to generate the first clutch torque T_CL1, and then the first clutch CL1 is released, thereby starting a first torque phase in which the torque of the second motor MG2 changes while the speed of the first motor MG1 remains unchanged.

[0069] Therefore, the torque of the first motor MG1 and the torque of the second motor MG2 are maintained, the speed of the first motor MG1 decreases and the speed of the second motor MG2 increases to start an inertia phase of synchronizing the rotation speeds of all rotation elements of the first planetary gear set PG1.

[0070] Therefore, when the second clutch CL2 is engaged, since all the rotating elements of the first planetary gear set PG1 are meshed with each other to rotate as a whole, the power supplied from the first motor MG1 is output to the differential DF at a speed ratio of 1:1, and in this state, the second torque phase of maintaining the speed of the first motor MG1 and releasing the torque of the second motor MG2 begins, thereby completing the shift to the second speed state corresponding to the high gear.

[0071] In the second torque phase, as described above, the speed of the first motor MG1 is maintained and the torque of the second motor MG2 is released, so that the torque of the first motor MG1 increases.

[0072] The torque of the first motor MG1 can be increased to Figure 4 T_MG1b in . It can be considered that Figure 4 The shifting process shown describes the following process: the transmission according to an exemplary embodiment of the present invention shifts from the state of T_MG1a outputting the maximum torque in the first speed state to the state of T_MG1b outputting the maximum torque in the second speed state, thereby realizing the shifting between two points on the isodynamic curve of the first motor MG1.

[0073] Note that the torque provided by the second clutch CL2 to maintain a state in which all rotation elements of the first planetary gear set PG1 are engaged with each other to rotate integrally is referred to as a second clutch torque T_CL2 .

[0074] The above shifting process can be explained by Figure 6 The curve diagram in . Figure 15 As shown, in a conventional transmission according to the prior art, the torque outputted through the differential DF is reduced during a period corresponding to the first torque phase according to the exemplary embodiment of the present invention, so that the shifting quality is deteriorated. Figure 6 As shown, in the transmission according to the exemplary embodiment of the present invention, the output torque is maintained without significant change before and after the shift, so that excellent shift quality can be ensured without shift shock.

[0075] Furthermore, in conventional transmissions for electric vehicles, heat generation due to the clutch playing a major role in gear shifting is a major issue in developing transmissions. However, in an exemplary embodiment of the present invention, the second motor MG2 plays a major role in gear shifting, thereby preventing gear shift shock and clutch heating, and significantly improving the durability of the clutch and transmission.

[0076] Meanwhile, in the first torque phase, the third clutch CL3 is engaged before torque is supplied from the second motor MG2 to the third rotation element of the first planetary gear set, and in the second torque phase, the third clutch CL3 is released after the second clutch CL2 is engaged.

[0077] That is, the third clutch CL3 can be engaged only when shifting gears to provide power from the second motor MG2 to the first planetary gear set PG1 to perform the above-mentioned actions, and in other states the third clutch CL3 can be released, and the fourth clutch can be engaged as needed to control the second motor MG2 to realize the torque vectoring control function.

[0078] Torque vectoring is a technology that actively controls the driving torque output from the differential DF to the output shafts on both sides to effectively reduce understeer when the vehicle is driving on high-speed curves or on uneven roads where the friction coefficients of the right and left drive wheels relative to the ground are different, thereby improving the vehicle's handling performance and stability. Figure 1 In an exemplary embodiment, after engaging the fourth clutch CL4 , the controller CLR may control the second motor MG2 to apply torque in opposite directions to the differential case and the selected output shaft to perform torque vectoring control.

[0079] At the same time, refer to Figures 7 to 9 , a control method for shifting a transmission from a high-speed gear (second gear) to a low-speed gear (first gear) includes: in a high-speed driving state in which the second clutch CL2 is engaged and the first motor MG1 is driven, the controller CLR releases the second clutch CL2 after increasing the torque of the second motor MG2 to the first clutch torque while maintaining the speed of the first motor MG1 (S50); the controller CLR reduces the speed of the second motor MG2 to 0 and increases the speed of the first motor MG1 while maintaining the torque of the first motor MG1 and the torque of the second motor MG2 constant (S60); and the controller CLR releases the torque of the second motor MG2 after engaging the first clutch CL1 to form a low-speed driving state (S70).

[0080] Hereinafter, this process will be described in more detail.

[0081] In the second speed state corresponding to a high gear, the second clutch CL2 is engaged and all rotating elements of the first planetary gear set PG1 rotate at the same speed. In this state, to shift to the first speed, the controller CLR increases the torque of the second motor MG2 to the first clutch torque T_CL1 while maintaining the speed of the first motor MG1.

[0082] That is, the torque of the second motor MG2 is increased so that the second motor MG2 provides torque corresponding to the first clutch torque T_CL1 , which is torque to be applied to the first ring gear R1 , to achieve the first speed state by fixing the first ring gear R1 .

[0083] The torque of the first motor MG1 decreases as the torque of the second motor MG2 increases, so that the speed of the first motor MG1 is maintained when the torque of the second motor MG2 increases as described above.

[0084] In fact, this process corresponds to the first torque stage in transmission control and is expressed as Figure 8 The torque of the first motor MG1 is reduced from T_MG1b to T_MG1a.

[0085] When the torque of the second motor MG2 increases to the first clutch torque, the second clutch CL2 is released.

[0086] Therefore, the torque of the first motor MG1 and the torque of the second motor MG2 are maintained constant, and an inertia phase in which the speed of the second motor MG2 decreases to 0 and the speed of the first motor MG1 increases begins.

[0087] When the speed of the second motor MG2 becomes 0, the first clutch CL1 is engaged to fix the first ring gear R1 and then the torque of the second motor MG2 is released to start the second torque phase, thereby completing the shift from high gear to low gear.

[0088] Even during the shifting process, the output torque remains substantially constant, eliminating shift shock and ensuring excellent shift quality, ultimately contributing to improved vehicle marketability. Furthermore, since the clutch involved in the shifting does not heat up, the durability of the clutch and transmission is improved.

[0089] Even in this case, in the first torque phase, the third clutch CL3 is engaged before torque is supplied from the second motor MG2 to the first ring gear R1, and in the second torque phase, the third clutch CL3 is released after the torque of the second motor MG2 is released.

[0090] As described above, the transmission for an electric vehicle according to an exemplary embodiment of the present invention provides two gear ratios (a low gear and a high gear), thereby achieving maximum climbing performance requiring relatively high torque and maximum speed performance requiring relatively high speed power while improving energy efficiency by reducing the weight of the vehicle even when using the first motor MG1 having a relatively small capacity.

[0091] Furthermore, after the second motor MG2 generates the first clutch torque T_CL1 or the second clutch torque T_CL2, when the first clutch CL1 and the second clutch CL2 are engaged and released, a state with little friction and little heat generation can be achieved in theory. Therefore, heating of the transmission and clutch can be prevented, and durability can be improved.

[0092] at the same time, Figure 10 、 Figure 11 and Figure 12 is described by Figure 1 Schematic diagram of the transmission implementing the torque vectoring control function. Figure 10 It shows Figure 1 A table of the rotational speed of each part in the transmission in a state where the fourth clutch CL4 is engaged and the second motor MG2 is stopped.

[0093] That is, when the second motor MG2 is not driven and the speed of the second motor MG2 is 0, the speeds of the left output shaft OL and the right output shaft OR of the differential DF are both 3000.

[0094] Note that the rotation speed of each portion is determined under the assumption that the number of teeth of the second ring gear R2 is 60, the number of teeth of the second sun gear S2 is 30, the number of teeth of the third ring gear R3 is 60, and the number of teeth of the third sun gear S3 is 30.

[0095] Figure 11 It shows Figure 1 4 is a table of the rotational speed of each part in the transmission in a state where the fourth clutch CL4 is engaged and the second motor MG2 is driven at a speed of 100 RPM.

[0096] That is, when the second motor MG2 is driven at 100 RPM, the speed of the left output shaft OL of the differential DF becomes 3300, and the speed of the right output shaft OR becomes 2700. Therefore, each of the speed deviation from the differential case of the differential DF to the right side and the speed deviation from the differential case of the differential DF to the left side becomes 300 RPM, thereby achieving torque vectoring control.

[0097] Figure 12 By using the lever diagram of the second planetary gear set and the third planetary gear set Figure 10 Status and Figure 11 The diagram for describing the torque vectoring control function is compared with each other. Figure 12 In, it means Figure 10 The solid line of the state and Figure 11 The dotted line shows the state where torque vectoring control is performed.

[0098] Note that, Figure 12The situation is shown where the speed of the third sun gear S3 connected to the right output shaft OR of the differential DF is reduced by 300RPM relative to the speed of the second sun gear S2 connected to the differential case, so although not shown, the left output shaft of the differential DF is increased by 300RPM relative to the speed of the differential case according to the construction and operation of the differential DF.

[0099] As described above, in the transmission according to an exemplary embodiment of the present invention, the second motor MG2 participates in gear shifting to achieve smooth gear shifting when the third clutch CL3 is engaged, and implements the torque vectoring control function when the fourth clutch CL4 is engaged, thereby improving the driving stability of the vehicle when driving on high-speed curves.

[0100] Meanwhile, in addition to the torque vectoring control, according to the exemplary embodiment Figure 13 and Figure 14 The gear shift control of the transmission Figure 1 The shift control of the transmission is basically the same, so it will be omitted Figure 13 and Figure 14 A detailed description of the gear shift control of the transmission.

[0101] According to an exemplary embodiment of the present invention, multiple speed ratios can be provided to reduce the capacity of the motor, achieve the maximum climbing performance and maximum speed performance required by the vehicle, improve the energy efficiency of the vehicle with a relatively simple structure and small weight, increase the driving distance on a single charge, prevent gear shift shock, significantly reduce heat generation and realize torque vector control to improve the high-speed cornering performance of the vehicle.

[0102] For convenience of explanation and accurate definition in the appended claims, the terms "up," "down," "inside," "outside," "upwardly," "downwardly," "front," "back," "rear," "inside," "outside," "inwardly," "outwardly," "inner," "outside," "interior," "exterior," "interior," "outside," "forwardly," and "rearwardly" are used to describe the positions of features of the exemplary embodiments shown in the figures. It will be further understood that the term "connect" or its derivatives refers to both direct and indirect connections.

[0103] The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. The foregoing descriptions are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to enable those skilled in the art to make and utilize the various exemplary embodiments of the invention and various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the appended claims and their equivalents.

Claims

1. A transmission for a vehicle, comprising: A first planetary gear set includes three rotating elements, namely, a first rotating element, a second rotating element, and a third rotating element; a first motor connected to the first rotating element of the first planetary gear set and inputting power to the first rotating element of the first planetary gear set; a differential connected to the second rotating element of the first planetary gear set and receiving power output from the second rotating element of the first planetary gear set; a second motor selectively providing power to the third rotating element of the first planetary gear set; a second planetary gear set including a first rotating element connected to a differential case of the differential and a second rotating element selectively receiving power from the second motor; as well as A third planetary gear set includes a third rotating element connected to the third rotating element of the second planetary gear set, a fixed second rotating element, and a first rotating element connected to a selected output shaft, which is one of the output shafts of the differential.

2. The transmission for a vehicle according to claim 1, further comprising: a first clutch selectively connecting the third rotating element of the first planetary gear set to a transmission housing; as well as The second clutch selectively directly connects two of the three rotating elements of the first planetary gear set to each other.

3. The transmission for a vehicle according to claim 2, wherein: The first planetary gear set includes a first sun gear as a first rotating element of the first planetary gear set, a first planet carrier as a second rotating element of the first planetary gear set, and a first ring gear as a third rotating element of the first planetary gear set and selectively connected to the first clutch, and The second clutch selectively connects the first sun gear and the first ring gear to each other.

4. The transmission for a vehicle according to claim 3, wherein The second motor is selectively connected to the first ring gear of the first planetary gear set via a third clutch.

5. The transmission for a vehicle according to claim 4, wherein The second rotation element of the second planetary gear set is selectively connected to the second motor through a fourth clutch.

6. The transmission for a vehicle according to claim 3, wherein The ratio of the number of teeth of the second sun gear of the second planetary gear set to the number of teeth of the second ring gear of the second planetary gear set and the ratio of the number of teeth of the third sun gear of the third planetary gear set to the number of teeth of the third ring gear of the third planetary gear set are the same as each other.

7. A transmission for a vehicle, comprising: A first planetary gear set includes three rotating elements, namely, a first rotating element, a second rotating element, and a third rotating element; a first motor connected to the first rotating element of the first planetary gear set and inputting power to the first rotating element of the first planetary gear set; a differential connected to the second rotating element of the first planetary gear set and receiving power output from the second rotating element of the first planetary gear set; a second motor selectively providing power to the third rotating element of the first planetary gear set; as well as a compound planetary gear set installed between a differential case and a selected output shaft of the differential to distribute power provided from the second motor to the differential case and the selected output shaft, and to make directions of torque distributed to the differential case and the selected output shaft opposite to each other, the selected output shaft being one of the output shafts of the differential.

8. The transmission for a vehicle according to claim 7, wherein The compound planetary gear set includes: a second planetary gear set including a first rotating element connected to the differential case and a second rotating element selectively connected to the second motor; and The third planetary gear set includes a third rotating element connected to the third rotating element of the second planetary gear set, a fixed second rotating element, and a first rotating element connected to the selected output shaft.

9. A control method for a transmission for a vehicle according to claim 5, the control method comprising: In a first gear driving state in which the first clutch is engaged and the first motor is driven, the controller releases the first clutch after controlling the second motor to provide the same torque to the third rotating element of the first planetary gear set as the torque used by the first clutch to support the third rotating element of the first planetary gear set; the controller reducing a speed of the first motor and increasing a speed of the second motor while maintaining the torque of the first motor and the torque of the second motor constant so as to synchronize speeds of the three rotating elements of the first planetary gear set with each other; and The controller, after engaging the second clutch, releases the torque of the second motor while maintaining the speed of the first motor to establish a second-speed driving state.

10. The control method according to claim 9, wherein: The controller engages the third clutch before providing torque from the second motor to the third rotation element of the first planetary gear set, and releases the third clutch after engaging the second clutch.

11. The control method according to claim 9, wherein: After engaging the fourth clutch, the controller controls the second motor to apply torque in opposite directions to the differential case and the selected output shaft to perform torque vectoring control.

12. The control method according to claim 9, further comprising: In the second gear driving state in which the second clutch is engaged and the first motor is driven, the controller releases the second clutch after increasing the torque of the second motor to the first clutch torque while maintaining the speed of the first motor; the controller reducing the speed of the second motor to 0 and increasing the speed of the first motor while maintaining the torque of the first motor and the torque of the second motor constant; and The controller releases the torque of the second motor to form the first-speed driving state after engaging the first clutch.

13. The control method according to claim 12, wherein: The controller engages the third clutch before releasing the second clutch and increasing the torque of the second motor, and releases the third clutch after releasing the torque of the second motor.

14. The control method according to claim 12, wherein: After engaging the fourth clutch, the controller controls the second motor to apply torque in opposite directions to the differential case and the selected output shaft to perform torque vectoring control.

15. A control method for a transmission for a vehicle, wherein a first motor is connected to a first rotating element of a first planetary gear set, a third rotating element of the first planetary gear set is selectively connected to a transmission case via a first clutch, a second rotating element of the first planetary gear set is connected to an output shaft, a second motor is connected to the third rotating element of the first planetary gear set, a second clutch selectively connects two of the three rotating elements of the first planetary gear set, and transmission control is enabled by the second motor, the control method comprising: In a first gear driving state in which the first clutch is engaged and the first motor is driven, the controller releases the first clutch after controlling the second motor to provide the same torque to the third rotating element of the first planetary gear set as the torque used by the first clutch to support the third rotating element of the first planetary gear set; the controller reducing a speed of the first motor and increasing a speed of the second motor while maintaining the torque of the first motor and the torque of the second motor constant so as to synchronize speeds of the three rotating elements of the first planetary gear set with each other; and The controller, after engaging the second clutch, releases the torque of the second motor while maintaining the speed of the first motor to establish a second-speed driving state.

16. The control method according to claim 15, further comprising: In the second gear driving state in which the second clutch is engaged and the first motor is driven, the controller releases the second clutch after increasing the torque of the second motor to the first clutch torque while maintaining the speed of the first motor; the controller reducing the speed of the second motor to 0 and increasing the speed of the first motor while maintaining the torque of the first motor and the torque of the second motor constant; and The controller releases the torque of the second motor to form the first-speed driving state after engaging the first clutch.

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