KR102348126B1 - Hybrid power train - Google Patents

Abstract

The present invention relates to a hybrid powertrain comprising an engine, a motor, an automatic transmission having a plurality of planetary gear sets and a plurality of friction elements, and a hybrid controller. The hybrid controller is configured to rotate the motor in a reverse direction in a state in which the automatic transmission engages a forward gear when receiving a reverse signal, and each friction element can include a plurality of friction plates. At least one friction element among the plurality of friction elements can be configured such that the number of friction plates is smaller than the number of friction plates determined on the basis of a reverse torque input when a vehicle is traveling backward, and the number of friction plates is greater than the number of friction plates determined based on a forward torque input when the vehicle is traveling forward. According to the present invention, the overall volume of the automatic transmission can be reduced.

Description

Hybrid powertrain {HYBRID POWER TRAIN}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid powertrain, and more particularly, to a hybrid powertrain that executes reverse driving of a vehicle by reverse rotation of a motor.

Hybrid vehicle means to drive the vehicle by efficiently combining two or more different types of power sources. means the vehicle being driven.

These hybrid vehicles are futuristic vehicles that can reduce exhaust gas and improve fuel efficiency by adopting a motor as an auxiliary power source as well as an engine. is in progress

A hybrid vehicle typically uses an engine and a motor. At a low speed, a motor having a relatively good low-speed torque characteristic is used as a main power source, and at a high speed, an engine having a relatively good high-speed torque characteristic is used as a main power source. Accordingly, the hybrid vehicle has excellent effects in improving fuel efficiency and reducing exhaust gas because the engine using the fossil fuel is stopped in the low speed section and the motor is used.

In addition, the driving device for a hybrid vehicle is an EV (Electric Vehicle) mode, which is a pure electric vehicle mode that uses only the rotational power of the motor for driving, and HEV (Hybrid Electric Vehicle) that uses the rotational power of the motor as an auxiliary power while using the rotational power of the engine as the main power. Mode, an engine mode using only the engine torque, and the like are driven in a plurality of driving modes, and the mode is converted from the EV mode to the HEV mode or the engine mode by starting the engine.

The hybrid vehicle may be classified into various structures such as a series type, a parallel type, and a hybrid type. Among them, in a TMED (Transmission Mounted Electric Drive) type of parallel hybrid vehicle, a motor is connected to an automatic transmission, and an engine clutch capable of switching between the EV mode and the HEV mode is installed between the engine and the motor. As with the engine, the motor always rotates only in the forward direction, and as the automatic transmission engages the reverse gear, the propulsion shaft rotates in the reverse direction, thereby executing reverse driving of the vehicle.

The automatic transmission may include a plurality of planetary gear sets and a plurality of friction elements, and may be configured to selectively engage any one gear stage among a plurality of forward and reverse gears through a selective fastening combination of the plurality of friction elements. In the conventional automatic transmission, the reverse gear ratio may be lower than that of the first forward gear ratio, and thus the operating line pressure of the friction element coupled when the reverse gear of the automatic transmission is engaged is increased or It is possible to increase the number of friction disks in the friction element. In addition, if there is a restriction on the total length of the automatic transmission, the overall gear ratio or the final gear ratio of the planetary gear sets may be increased to increase the reverse gear ratio, so that the climbing performance is a design goal when the forward stage of the automatic transmission is engaged. It could exceed , and fuel efficiency was lowered.

Matters described in this background section are prepared to enhance understanding of the background of the invention, and may include matters that are not already known to those of ordinary skill in the art to which this technology belongs.

The present invention has been devised in consideration of the above points, and the number of friction plates, torque capacity, final gear ratio, and line pressure of at least one friction element among a plurality of friction elements by executing backward running of the vehicle by reverse rotation of the motor. The purpose is to provide a hybrid powertrain that can reduce the back.

The present invention for achieving the above object is a hybrid powertrain including an engine, a motor, an automatic transmission having a plurality of planetary gear sets and a plurality of friction elements, and a hybrid controller, wherein the hybrid controller receives a reverse signal When the automatic transmission is configured to rotate the motor in the reverse direction in a state in which the forward gear is engaged, each friction element may include a plurality of friction plates. At least one friction element among the plurality of friction elements, wherein the number of friction plates is smaller than the number of friction plates determined on the basis of the reverse torque input when the vehicle is traveling in reverse, and the number of friction plates is input during the forward driving of the vehicle It may be configured to be larger than the number of friction plates determined based on the forward torque.

According to an embodiment, the at least one friction element is configured to have a torque capacity lower than a reference torque capacity, and the reference torque capacity may be a torque capacity determined when the automatic transmission engages the reverse gear. The torque capacity of the at least one friction element is a value obtained by subtracting the surplus torque capacity from the reference torque capacity, and the surplus torque capacity is the maximum among the gear ratio ratio of the forward/reverse gear and the torque ratio of the reverse/forward gear to the friction element. It may be a torque capacity determined based on the reciprocal of the value.

According to another embodiment, the at least one friction element is configured to have a final gear ratio lower than a reference final gear ratio, and the reference final gear ratio may be a final gear ratio determined when the automatic transmission engages the reverse gear. The final gear ratio of the at least one friction element is a value obtained by subtracting the final surplus gear ratio from the reference final gear ratio, and the surplus final gear ratio is among the gear ratio ratio of the forward/reverse gear and the torque ratio of the reverse/forward gear to the friction element. It may be the final gear ratio determined based on the reciprocal of the maximum value.

According to another embodiment, the at least one friction element is configured to have a line pressure lower than a reference line pressure, and the reference line pressure may be a line pressure determined when the automatic transmission engages the reverse gear. The line pressure of the at least one friction element is a value obtained by subtracting the surplus line pressure from the reference line pressure, and the surplus line pressure is a ratio of the gear ratio of the forward/reverse gear and the torque ratio of the reverse/forward gear to the friction element. The line pressure may be determined based on the reciprocal of the maximum value.

According to the present invention, the reverse driving of the vehicle can be performed by rotating the motor in the reverse direction while the automatic transmission engages the forward gear. In addition, by performing reverse driving of the vehicle in a state in which the automatic transmission is not engaged with the reverse gear, it is possible to sufficiently secure the reverse climbing performance of the vehicle, and it is possible to relatively reduce the number of friction plates or friction surfaces of the friction elements. Weight can be reduced, which in turn can reduce the overall volume of the automatic transmission.

In addition, according to the present invention, it is possible to improve the fuel efficiency of the vehicle by reducing the torque capacity and the final gear ratio of the friction element compared to the prior art.

And, according to the present invention, by reducing the line pressure of the friction element compared to the prior art, it is possible to improve the pump power loss load and the transmission load, and thereby, the vehicle fuel efficiency can be improved. In addition, it is possible to reduce the cost by eliminating hydraulic components such as FSV for separating the reverse gear and the forward gear of the automatic transmission.

1 is a configuration diagram illustrating the configuration of a hybrid powertrain according to an example of the present invention.
2 is a configuration diagram illustrating the configuration of an automatic transmission according to an embodiment of the present invention.
3 is a view showing the configuration of a friction element according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. For reference, sizes of components, thicknesses of lines, etc. shown in the drawings referenced to describe the present invention may be expressed somewhat exaggeratedly for convenience of understanding. In addition, the terms used in the description of the present invention are defined in consideration of the functions in the present invention, and thus may vary according to user, operator intention, custom, and the like. Therefore, the definition of this term should be made based on the content throughout the present specification.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, or order of the elements are not limited by the terms. In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Referring to FIG. 1 , a hybrid powertrain 1 according to an embodiment of the present invention may include an engine 2 , a motor 3 , and an automatic transmission 4 .

The engine 2 may be controlled by an engine controller 5 (ECU). The operation of the engine 2 can be controlled by the engine controller 5 sending a control command to the throttle valve, fuel injector, variable valve timing device, or the like. A starting motor 2a such as a hybrid starter generator (HSG) may be connected to the engine 2 through a pulley mechanism.

The motor 3 may be a synchronous motor generator in which a permanent magnet is embedded in a rotor and a stator coil is wound around a stator, and the motor 3 may be controlled by the motor controller 6 . The operation of the motor 3 can be controlled by the motor controller 6 sending a control command to the motor 3 .

The clutch 9 may be mounted between the engine 2 and the motor 3 , and the engine 2 is to be disconnected and connected to the motor 3 by engagement and disengagement of the clutch 9 . can

The automatic transmission 4 may be configured to switch gears according to a driver's intention (vehicle speed, an opening degree of an accelerator pedal, etc.). The automatic transmission 4 may be controlled by a transmission controller 7 (TCU). The automatic transmission 4 may be connected to the differential gear 4b through the propulsion shaft 4a, and power output from the automatic transmission 4 may be transmitted to the differential gear 4b through the propulsion shaft 4a.

The engine controller 5 , the motor controller 6 , and the transmission controller 7 may be connected to the hybrid controller 8 , and the hybrid controller 8 manages the energy consumption of the entire vehicle and drives the vehicle with the highest efficiency. It can be configured to

The hybrid controller 8 controls the operation of the engine 2 according to the control command of the engine controller 5 , the operation control of the motor 3 according to the control command of the motor controller 6 , and engagement and disengagement of the clutch 9 . It is configured to execute control, shifting of the automatic transmission 4 through a control command of the transmission controller 7 , and the like.

The engine 2 can rotate only in the forward direction P, the motor 3 can selectively rotate in the forward direction P and the reverse direction R, and the propulsion shaft 4a is rotated in the forward direction P and the reverse direction ( R), and the automatic transmission 4 may be configured to selectively engage a plurality of forward gears.

The conventional hybrid powertrain is configured such that the engine and the motor rotate only in the forward direction, and the propulsion shaft 4a rotates in the reverse direction as the automatic transmission 4 engages the reverse gear.

On the other hand, according to the present invention, the reverse signal is transmitted to the hybrid controller 8 by the driver operating the shift lever in reverse, and the hybrid controller 8 operates the motor 3 with the automatic transmission 4 engaged with the forward gear. can be controlled to rotate in the reverse direction R, whereby the driving shaft 4a rotates in the reverse direction R so that the vehicle can be run backwards. In particular, according to the present invention, when the motor 3 rotates in the reverse direction R, the automatic transmission 4 engages the first forward stage, thereby sufficiently securing the backward climbing performance.

Meanwhile, although FIG. 1 illustrates a TMED type hybrid powertrain in which the engine 2 and the motor 3 are connected through the clutch 9, the present invention is not limited thereto, and the FMED type hybrid powertrain, power branch type It can be applied to various types of hybrid powertrains, such as hybrid powertrains.

2 is a view showing an example of the automatic transmission 4 . The automatic transmission 4 illustrated in FIG. 2 is a forward 6-speed and reverse 1-speed automatic transmission.

Referring to FIG. 2 , the automatic transmission 4 includes an input shaft 11 , an output gear 12 , and one or more planetary gear sets PG1 , PG2 , PG3 disposed between the input shaft 11 and the output gear 12 . ) and a plurality of friction elements 21 , 22 , 31 , 32 , 33 may be included.

The plurality of friction elements 21 , 22 , 23 , 31 , 32 , 33 includes a first clutch 21 , a second clutch 22 , a third clutch 23 , a first brake 31 , a second brake ( 32) and the third brake 33 may be included.

According to an embodiment of the present invention, the first clutch 21 may be an overdrive clutch (OD/C), and the second clutch 22 is the automatic transmission 4 in 3 forward gears, 5 forward gears, and reverse gear. It may be a clutch (35R/C) that engages when fastening, the third clutch 23 may be a one-way clutch (OW/C) that restricts the rotational direction, and the first brake (B1) is a shift lever may be a low reverse brake (LR/B) that operates in combination when the automatic transmission (4) engages the first forward and reverse gears when it is located in the parking position or the neutral position, and the second brake (B2) may be an underdrive brake UD/B, and the third brake B3 may be a brake 26/B coupled at the second and sixth stages.

The plurality of planetary gear sets PG1, PG2, PG3 includes a first planetary gear set PG1 connected to the output gear 12, a second planetary gear set PG2 connected to the first planetary gear set PG1, A third planetary gear set PG3 connected to the second planetary gear set PG2 may be included.

The first planetary gear set PG1 includes a first sun gear S1 , a first carrier C1 , and a first ring gear R1 . The first sun gear S1 may be selectively connected to the transmission case 13 through the second brake 32 , the first carrier C1 may be connected to the output gear 12 , and the first ring gear R1 . may be connected to the third ring gear R3 of the third planetary gear set PG3.

The second planetary gear set PG2 includes a second sun gear S2 , a second carrier C2 , and a second ring gear R2 . The second sun gear S2 may be connected to the third brake 33 and the second clutch 22, and the second carrier C2 may be connected to the third carrier C3 of the third planetary gear set PG3. and the second ring gear R2 may be connected to the first carrier C1 of the first planetary gear set PG1 . The third brake 33 may selectively connect the second sun gear S2 and the transmission case 13 , and the second clutch 22 may selectively connect the second sun gear S2 and the input shaft 11 . .

The third planetary gear set PG3 has a third sun gear S3, a third carrier C3, and a third ring gear R3. The third sun gear S3 may be connected to the input shaft 11, and the third carrier C3 is the second carrier C2, the first clutch 21, and the first brake of the second planetary gear set PG2. 31 ), and the third clutch 23 , and the third ring gear R3 may be connected to the first ring gear R1 of the first planetary gear set PG1 . The first clutch 21 may selectively connect the third carrier C3 and the input shaft 11 , and the first brake 31 and the third clutch 23 may include the third carrier C3 and the transmission case 13 . ) can be optionally connected.

Referring to FIG. 3 , each friction element 21 , 22 , 23 , 31 , 32 , 33 may include a plurality of friction plates 41 and a plurality of pressure plates 42 , and each friction plate 41 . may come into contact with the adjacent pressure plate 42 by the movement of the piston 45 , and the piston 45 may be configured to return to its original position by the return spring 46 . As each friction plate 41 comes into contact with the pressure plate 42 , a friction surface 43 may be formed between the friction plate 41 and the pressure plate 42 .

The prior art 6-speed forward and 1-speed reverse automatic transmissions have a common friction element that is commonly coupled when fastening the reverse end and the forward end of the automatic transmission. For example, in the 6-speed forward and 1-speed reverse automatic transmissions shown in FIG. 2 , the second clutch 22 which is a 35/R clutch and the first brake 31 which is a Lowry bus (LR) brake are the common friction elements 22, 31) is applicable.

In the prior art 6-speed forward and 1-speed reverse automatic transmissions, the gear ratio of each stage is set as shown in Table 1 below.

gear ratio of each stage 1st stage 2nd stage 3 tier 4 tier 5 tier 6 tier retrospective 4.639 2.826 1.841 1.386 1.000 0.772 -3.385

According to the prior art 6-speed forward and 1-speed reverse automatic transmission, the ratio of the forward gear ratio/reverse gear ratio is referred to as X, and X is greater than 1. For example, as shown in Table 1, the ratio (X) of the first forward gear ratio/reverse gear ratio is 4.639/3.385 = 1.370. Each forward gear ratio is a gear ratio set when the automatic transmission engages each forward gear, and the reverse gear ratio is a gear ratio set when the automatic transmission engages the reverse gear.

In the prior art 6-speed forward and 1-speed reverse automatic transmissions, the torques responsible for friction elements in each stage are set as shown in Table 2 below.

Talk in charge 1st stage 2nd stage 3 tier 4 tier 5 tier 6 tier retrospective friction element LR/B(31) 2.348 0.000 0.000 0.000 0.000 0.000 -4.385 35R/C(22) 0.000 0.000 0.349 0.000 -0.295 0.000 1.000 OD/C(21) 0.000 0.000 0.000 0.701 1.295 1.000 0.000 UD/D(32) 1.291 1.291 0.841 0.386 0.000 0.000 0.000 26/B(33) 0.000 0.535 0.000 0.000 0.000 -0.228 0.000 Print -4.639 -2.826 -1.841 -1.386 -1.000 -0.772 3.385

According to the prior art 6-speed forward and 1-speed reverse automatic transmissions, the ratio of the reverse gear torque/forward gear torque with respect to the common friction elements 22 and 31 may be referred to as Y. The reverse gear torque is the torque that the common friction element is in charge of when the automatic transmission engages the reverse gear, and the forward gear torque is the torque that the common friction element is responsible for when the automatic transmission engages the forward gear. For example, as shown in Table 2, the ratio (Y) of the first forward gear/reverse gear torque with respect to the second clutch 22 is 4.385/2.348 = 1.868, and the first three gears for the first brake 31 The ratio (Y) of the load torque/reverse gear torque is 1.000/0.295 = 3.390.

As described above, in the conventional 6-speed forward and 1-speed automatic transmissions of the prior art, the torque capacity of each common friction element 22 and 31, the final automatic transmission, so as to sufficiently secure the reverse climbing performance when the reverse gear is engaged. The gear ratio and the line pressure acting on each common friction element 22 and 31 may be determined to be relatively large.

In the present invention, the automatic transmission 4 does not engage the reverse gear because the reverse travel of the vehicle can be executed by the reverse rotation of the motor 3 . That is, when the motor 3 rotates in the reverse direction R in a state in which the automatic transmission 4 engages the forward stage, such as forward 1st gear, 3rd forward gear, etc., the propulsion shaft 4a can rotate in the reverse direction R, and , thus the vehicle may be driven backward.

The motor input torque of the automatic transmission 4 is referred to as Ti, and when the automatic transmission 4 engages the reverse gear, the torque of the common friction elements 22 and 31 is referred to as Tr, and is expressed as Tr = Ti × Y can be

Each torque capacity Tc is defined by [Equation 1] below.

Here, n is the number of friction surfaces 43 .

According to an embodiment, the friction coefficient μ may be 0.09 to 0.13.

According to the embodiment of the present invention, each friction element 21 , 22 , 23 , 31 , 32 , 33 must have a torque capacity Tc greater than a torque Tr input to each friction element (Tc > Tr). can be transmitted normally.

The torque input to the common friction elements 22 and 31 when the vehicle travels in reverse _{is referred to as a reverse torque T r_REV} , and the torque input to the common friction elements 22 and 31 when the vehicle travels forward is a forward torque. (T _{r_FWD)} .

According to the automatic transmission of the prior art, the torque capacity T _c1 of each common friction element 22 , 31 is greater than the reverse torque T _{r_REV} and the forward torque T _{r_FWD} , and the reverse torque T _{r_FWD} is the forward torque (T _{r_FWD} ) may be set larger than (T _c1 > T _{r_REV} > T _{r_FWD} ).

In contrast, according to the present invention, the torque capacity (T _C ) of each common friction element (22, 31) is smaller than the reverse torque (T _{r_REV} ), it can be set larger than the _{forward torque (T r_FWD ) (T r_REV} > T _c > T _{r_FWD} ). According to an embodiment of the present invention, the friction plate 41 or friction surface 43 of each common friction element 22, 31 is smaller than the number of friction plates or friction surfaces determined based on the _{reverse torque T r_REV,} It may be configured to be larger than the number of friction plates or friction surfaces determined based on the forward torque (T _{r_FWD ).}

According to one embodiment, since the automatic transmission 4 of the present invention does not engage the reverse gear, the common friction elements 22 and 31 do not need to consider the reverse climbing performance, and accordingly, the torque of the common friction elements 22 and 31 The capacity Tc may be configured to be lower than the reference torque capacity T1. Here, the “reference torque capacity T1” may be the torque capacity of the common friction elements 22 and 31 determined when it is assumed that the automatic transmission engages the reverse gear. Specifically, the torque capacity Tc of each common friction element 22 and 31 may be a value obtained by subtracting the surplus torque capacity T2 from the reference torque capacity T1 (ie, Tc = T1 - T2). The surplus torque capacity (T2) is the reciprocal of the maximum value among the forward gear ratio/reverse gear ratio ratio (X) and the ratio of the reverse gear torque/forward gear torque to the friction elements 22 and 31 (Y) It may be determined based on /(MAX[X, Y]).

According to another embodiment, since the automatic transmission 4 of the present invention does not engage the reverse gear, the common friction elements 22 and 31 do not need to consider the reverse grade performance, and thus the automatic transmission 4 when the vehicle is traveling in reverse. ) of the final gear ratio (Z) may be configured to be lower than the reference final gear ratio (Z1). Here, the "reference final gear ratio Z" may be the final gear ratio of the common friction elements 22 and 31 determined when it is assumed that the automatic transmission engages the reverse gear. Specifically, the final gear ratio Z of the automatic transmission 4 may be a value obtained by subtracting the surplus final gear ratio Z2 from the reference final gear ratio Z1 (ie, Z = Z1 - Z2). The surplus final gear ratio (Z2) is the reciprocal of the maximum value among the forward gear ratio/reverse gear ratio ratio (X) and the ratio of the reverse gear torque/forward gear torque to the friction elements (22, 31) (Y) It may be determined based on /(MAX[X, Y]).

According to another embodiment, since the automatic transmission 4 of the present invention does not engage the reverse gear, the common friction elements 22 and 31 do not need to consider the reverse climbing performance, and thus the common friction elements 22 and 31 The line pressure W may be configured to be lower than the reference line pressure W1 . Here, the “reference line pressure W1” may be the line pressure of the common friction elements 22 and 31 determined when it is assumed that the automatic transmission engages the reverse gear. Specifically, the line pressure W of each common friction element 22 and 31 may be a value obtained by subtracting the surplus line pressure W2 from the reference line pressure W1 (ie, W = W1 - W2). The surplus line pressure (W2) is the reciprocal of the maximum value among the forward gear ratio/reverse gear ratio ratio (X) and the ratio of the reverse gear torque/forward gear torque to the friction elements 22 and 31 (Y). It may be a line pressure determined based on /(MAX[X, Y]) For example, the reference line pressure W1 is 20 bar, the surplus line pressure W2 is 5 bar, and the The line pressure (W) is 15 bar.

According to the present invention, the reverse driving of the vehicle can be performed by rotating the motor in the reverse direction while the automatic transmission engages the forward gear. In addition, by performing reverse driving of the vehicle in a state in which the automatic transmission is not engaged with the reverse gear, it is possible to sufficiently secure the reverse climbing performance of the vehicle, and it is possible to relatively reduce the number of friction plates or friction surfaces of the friction elements. Weight can be reduced, which in turn can reduce the overall volume of the automatic transmission.

In addition, according to the present invention, it is possible to improve the fuel efficiency of the vehicle by reducing the torque capacity and the final gear ratio of the friction element compared to the prior art.

And, according to the present invention, by reducing the line pressure of the friction element compared to the prior art, it is possible to improve the pump power loss load and the transmission load, and thereby, the vehicle fuel efficiency can be improved. In addition, it is possible to reduce the cost by eliminating hydraulic components such as FSV for separating the reverse gear and the forward gear of the automatic transmission.

The above description is merely illustrative of the technical spirit of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains.

Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

1: Hybrid Powertrain
2: engine
3: Motor
4: automatic transmission
5: engine controller
6: Motor controller
7: Transmission controller
8: Hybrid controller
9: Clutch
11: input shaft
12: output gear
21, 22, 23, 31, 32, 33: friction element
PG1, PG2, PG3: Planetary Gear Set

Claims (7)

A hybrid powertrain comprising an engine, a motor, an automatic transmission having a plurality of planetary gear sets and a plurality of friction elements, and a hybrid controller,
The hybrid controller is configured to rotate the motor in the reverse direction in a state in which the automatic transmission engages the forward gear when receiving the reverse signal;
each friction element comprising a plurality of friction plates;
At least one friction element among the plurality of friction elements is selected based on a number of friction plates in which the number of friction plates is smaller than the number of friction plates determined based on a reverse torque input during reverse driving of the vehicle, and a forward torque input during forward driving of the vehicle. A hybrid powertrain configured to be larger than the number of friction plates determined by The method according to claim 1,
the at least one friction element is configured to have a torque capacity lower than a reference torque capacity;
The reference torque capacity is a torque capacity determined when the automatic transmission engages the reverse gear. 3. The method according to claim 2,
The torque capacity of the at least one friction element is a value obtained by subtracting the surplus torque capacity from the reference torque capacity. A hybrid powertrain whose torque capacity is determined based on the reciprocal of the value. The method according to claim 1,
the at least one friction element is configured to have a final gear ratio lower than a reference final gear ratio;
The reference final gear ratio is a final gear ratio determined when the automatic transmission engages the reverse gear. 5. The method according to claim 4,
The final gear ratio of the at least one friction element is a value obtained by subtracting the final surplus gear ratio from the reference final gear ratio, and the surplus final gear ratio is among the gear ratio ratio of the forward/reverse gear and the torque ratio of the reverse/forward gear for the friction element. Hybrid powertrain, the final gear ratio determined based on the reciprocal of the maximum value. The method according to claim 1,
the at least one friction element is configured to have a line pressure lower than a reference line pressure;
The reference line pressure is a line pressure determined when the automatic transmission engages the reverse gear. 7. The method of claim 6,
The line pressure of the at least one friction element is a value obtained by subtracting the surplus line pressure from the reference line pressure, and the surplus line pressure is a ratio of the gear ratio of the forward/reverse gear and the torque ratio of the reverse/forward gear to the friction element. Hybrid powertrain with line pressure determined based on the reciprocal of the maximum value.

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