KR101325823B1 - Control method of continuously variable transmission for vehicle - Google Patents

Abstract

The present invention relates to a control method of a continuously variable transmission for a vehicle having a sub-speed transmission together with a belt-type continuously variable transmission. According to an embodiment of the present invention, a belt-type continuously variable transmission is connected to the belt-type continuously variable transmission and shifts forward. A control method for a continuously variable transmission for a vehicle comprising a first transmission stage and a second transmission stage including a second transmission stage having a smaller transmission ratio than the first transmission stage, wherein the mode is shifted when the mode is shifted. The target transmission ratio of the sub-transmission is determined by the actual transmission ratio of the continuously variable transmission, and the continuously variable transmission control method for a vehicle which can prevent the shift shock when the mode is shifted is closely controlled by changing the transmission ratio changes of the belt-type continuously variable transmission and the secondary transmission. Is provided.

Description

Control method of continuously variable transmission for vehicle

The present invention relates to a control method of a continuously variable transmission for a vehicle. More particularly, the present invention relates to a control method of a continuously variable transmission for a vehicle including a sub transmission.

The belt type continuously variable transmission (hereinafter referred to as `` variator '') has two pulleys which can change the groove width and a belt wound between the pulleys, and the groove width of the pulley is changed by the hydraulic pressure supplied to each pulley. It is a transmission that can change the speed ratio without change by changing.

The variator can use the operating point of the engine in a more efficient condition than the conventional stepped transmission, so it can be expected to improve the fuel economy of the vehicle, and in a vehicle equipped with a continuously variable transmission, by increasing the transmission range, the better power performance and efficiency Can be obtained.

However, in order to enlarge the shift range in the existing variator, the diameter of the pulley may be increased, but in this case, the efficiency of the variator may be deteriorated because the size of the variator is increased.

Therefore, in Korean Patent Registration No. 10-0490639 (Patent Document 1), the transmission range of the vehicle is configured by changing the speed change stage of the sub transmission according to the driving conditions by installing two or more forward transmissions at the front end or the rear end of the variator. Is expanding.

At this time, when the sub transmission shifts the mode conversion from the first gear (low speed mode) to the second gear (high speed mode), a shift shock occurs as the entire transmission ratio of the continuously variable transmission including the variator and the sub transmission changes.

Accordingly, it is necessary to control the transmission ratio of the variator in the opposite direction to the direction in which the transmission ratio of the secondary transmission changes, i.e., to the lower stage, so that the entire transmission ratio is kept constant.

The same applies to the case where the sub transmission shifts from the second gear to the first gear, and the transmission ratio of the variator is changed from the low gear to the high gear so that the overall gear ratio is kept constant.

Conventionally, the target value of the variator transmission ratio was calculated from the change of the sub transmission transmission ratio at the time of mode conversion shift, and the variator was shifted to the low stage or high stage.

However, at this time, since the shift speed of the variator is slower than the shift speed of the secondary transmission, the shift of the variator does not reach the target value even when the shift of the secondary transmission ends, so that the entire transmission ratio is not kept constant. have.

Patent Document 1: Korean Patent Registration No. 10-0490639

The present invention has been made to solve the above problems, in one embodiment of the present invention, the target transmission ratio of the sub-transmission is determined by the actual transmission ratio of the variator during the mode conversion shift, and the target transmission ratio of the sub-transmission and An object of the present invention is to provide a continuously variable transmission control method for a vehicle in which an operating oil pressure of a secondary transmission is controlled by feedback control using an error of an actual transmission ratio.

It is also an object of the present invention to provide an adaptive feedback control method in which the gain value of the feedback control is adjusted by the feedback error value of the sub transmission transmission ratio, the feedback error value of the variator transmission ratio, and the degree of gear change of the sub transmission.

According to a preferred embodiment of the present invention, a belt-type continuously variable transmission, and the belt-type continuously variable transmission, including a first speed change stage and a second speed change speed smaller than the first speed change gear as the forward speed change stage. A control method of a continuously variable transmission for a vehicle comprising a transmission, wherein a target transmission ratio of the secondary transmission is determined by an actual transmission ratio of the belt type continuously variable transmission when a mode shift is performed in which the secondary transmission is performed. A control method is provided.

In this case, it is preferable to obtain a target transmission ratio of the sub transmission by dividing the total target transmission ratio of the transmission including the belt continuously variable transmission and the sub transmission by the actual transmission ratio of the belt continuously variable transmission.

The shift ratio of the belt continuously variable transmission is feedback-controlled through a PI controller using an error between a target transmission ratio and an actual transmission ratio of the belt continuously variable transmission.

In addition, the change of the transmission ratio of the sub-transmission is feedback controlled through the PI controller using an error between the target transmission ratio and the actual transmission ratio of the sub-transmission.

In this case, the transmission ratio error of the belt-type continuously variable transmission, the transmission ratio error of the sub-transmission, and the shift progress degree of the sub-transmission is input to a gain scheduler, the PI controller of the PI controller for controlling the shift ratio of the sub-transmission by the gain scheduler. The gain value is adjusted.

On the other hand, control of a continuously variable transmission for a vehicle comprising a belt continuously variable transmission, and a secondary transmission including a first transmission stage and a second transmission stage having a smaller gear ratio than the first transmission stage as a forward shift stage. A method comprising: setting an overall target speed ratio setting step of setting a transmission ratio of the belt-type continuously variable transmission and the sub-transmission as a whole target transmission ratio according to a driving state of a vehicle; A mode conversion determining step of determining whether the overall target speed ratio changes across the mode conversion speed ratio; A sub-transmission shift determination step of determining a method of changing a shift stage of the sub-transmission when the total target shift ratio changes across a mode conversion shift ratio; An inertia phase determination step of determining whether an input speed of the sub transmission is changed by the shift stage change determined in the sub transmission shift determination step; A variator shift characteristic setting step of setting a target shift characteristic of the belt-type continuously variable transmission when it is determined as an inertia phase in the inertia phase determination step; And a cooperative control step of changing the speed ratio of the sub-transmission and changing the speed ratio of the belt-type continuously variable transmission in a direction opposite to the direction in which the speed ratio of the sub-transmission is changed. do.

According to a method of controlling a continuously variable transmission for a vehicle according to an embodiment of the present invention, the variator and the sub-transmission are controlled by a PI controller, and in particular, by using a gain scheduler in the sub-transmission control, the transmission ratio of the variator and the sub-transmission By using the adaptive PI controller in consideration of the progress of the gear change, the shift of the variator shift and the sub-transmission are closely controlled with each other, thereby preventing shift shock during the mode shift shift.

1 is a schematic configuration diagram of a continuously variable transmission for a vehicle according to an embodiment of the present invention.
2 is a block diagram showing an internal configuration of a transmission controller according to an embodiment of the present invention.
3 is a diagram illustrating a shift map of a continuously variable transmission for a vehicle according to an exemplary embodiment of the present invention.
Figure 4 is a flow chart of a continuously variable transmission control method for a vehicle according to an embodiment of the present invention.
FIG. 5 is a view showing changes in target speed ratio and actual speed ratio of the variator and the sub transmission in the inertia phase. FIG.
Figure 6 is a block diagram showing a PI control method of the variator and the sub-transmission according to an embodiment of the present invention.

Hereinafter, a preferred embodiment of a continuously variable transmission control method for a vehicle according to an embodiment of the present invention will be described with reference to the accompanying drawings. In this process, the thicknesses of the lines and the sizes of the components shown in the drawings may be exaggerated for clarity and convenience of explanation.

In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention or custom of the user, the operator. Therefore, definitions of these terms should be made based on the contents throughout this specification.

In addition, the following embodiments are not intended to limit the scope of the present invention, but merely as exemplifications of the constituent elements set forth in the claims of the present invention, and are included in technical ideas throughout the specification of the present invention, Embodiments that include components replaceable as equivalents in the elements may be included within the scope of the present invention.

In addition, in the following description, it turns out previously that the "speed ratio" of a certain transmission points to the value obtained by dividing the input rotational speed of the said transmission by the output rotational speed of the said transmission.

Example

1 is a schematic configuration diagram of a continuously variable transmission for a vehicle according to an embodiment of the present invention, Figure 2 is a block diagram showing the internal configuration of a transmission controller according to an embodiment of the present invention.

The vehicle has an engine 1 as a power source, and the output rotation of the engine 1 is a torque converter 2 having a lock-up clutch, a first gear train 3, a continuously variable transmission (hereinafter, a transmission) 4 The second gear train 5 is transmitted to the driving wheel 7 through the longitudinal reduction gear 6. The second gear train 5 is provided with a parking mechanism 8 for locking the output shaft of the transmission 4 so as not to rotate mechanically at the time of parking.

In addition, the vehicle includes an oil pump 10 driven by using a part of the power of the engine 1 and a hydraulic control circuit 11 for supplying the oil pump 10 to each part of the transmission 4 by adjusting the oil pressure from the oil pump 10. And the transmission controller 12 which controls the hydraulic control circuit 11 is provided. At this time, the hydraulic control circuit 11 and the transmission controller 12 constitute a shift control means.

The transmission 4 includes a belt type continuously variable transmission (hereinafter referred to as a `` variator '') 20 and a sub transmission 30 installed in series in the variator 20.

For example, the sub transmission 30 may be directly connected to the output shaft of the variator 20 as shown in FIG. 1, or may be connected to another transmission or power transmission mechanism (for example, a gear train). good. Alternatively, the sub transmission 30 may be connected to the front end (input shaft side) of the variator 20.

The variator 20 has a primary pulley 21, a secondary pulley 22, and a V belt 23 wound therebetween. Each of the pulleys 21 and 22 is provided with a fixed cone plate, a movable cone plate disposed with the sheave surface facing the fixed cone plate, and forming a V groove between the fixed cone plate, and the movable cone plate. It is provided with the hydraulic cylinders 23a and 23b which are provided in the back surface of a board, and displace the movable cone board in an axial direction. At this time, if the hydraulic pressure supplied to the hydraulic cylinders 23a and 23b is adjusted, the width of the V groove is changed to change the contact radius between the V belt 23 and the respective pulleys 21 and 22 to change the speed ratio of the variator 20. Will change steplessly.

The sub transmission 30 is a transmission of two or more forward stages (for example, two forward and one reverse stages), for example, a Lavigno planetary planetary gear mechanism 31 which connects carriers of two planetary gears, A plurality of frictional fastening elements (Low brake 32, High clutch 33, Rev brake 34) connected to a plurality of rotating elements constituting the Lavigno type planetary gear mechanism 31 and changing their linkage state. It is provided.

When the supply hydraulic pressure to each of the frictional engagement elements 32 to 34 is adjusted to change the engagement and release state of each frictional engagement element 32 to 34, the speed change stage of the sub transmission 30 is changed.

For example, when the low brake 32 is engaged and the high clutch 33 and the Rev brake 34 are released, the speed change stage of the sub transmission 30 becomes one speed. When the high clutch 33 is fastened and the low brake 32 and the rev brake 34 are released, the speed change stage of the auxiliary transmission 30 becomes two speeds in which the speed ratio is smaller than one speed. In addition, when the Rev brake 34 is engaged and the low brake 32 and the high clutch 33 are released, the speed change stage of the sub transmission 30 becomes reverse. On the other hand, in the following description it will be expressed as the "low speed mode" that the gear stage of the sub-transmission 30 is 1 speed, and the gear stage of the secondary transmission 30 is expressed as "high speed mode".

As shown in FIG. 2, the transmission controller 12 connects the CPU 121, the storage device 122 made of RAM / ROM, the input interface 123, the output interface 124, and the mutual connection thereof. It consists of a bus 125.

The input interface 123 includes an output signal of the throttle opening amount sensor 41 for detecting the opening amount APS of the throttle valve of the engine 1, and an input rotation speed of the transmission 4 (rotational speed of the primary pulley; Npri The output signal of the rotational speed sensor 42, the output signal of the vehicle speed sensor 43 for detecting the running speed VSP of the vehicle, and the oil temperature sensor 44 for detecting the oil temperature of the transmission 4 The output signal, the output signal of the inhibitor switch 45 for detecting the position of the transmission select lever, and the like are input.

The memory 122 stores a shift control program of the transmission 4 and a shift map (see FIG. 3) used in the shift control program. The CPU 121 reads and executes a shift control program stored in the memory device 122, generates and processes a shift control signal by arithmetic processing various signals input through the input interface 123, and generates the shift control signal. Is output to the hydraulic control circuit 11 through the output interface 124. Various values used by the CPU 121 in arithmetic processing and the arithmetic result are stored in the memory device 122.

The hydraulic control circuit 11 is composed of a plurality of hydraulic fluid control valves. The oil pressure control circuit 11 controls a plurality of oil pressure control valves based on the shift control signal from the transmission controller 12 to switch the oil pressure supply path, and at the same time, transmits oil pressure generated by the oil pump 10 to the transmission 4. Supply to each site of. Thereby, the speed ratio of the variator 20 and the speed change stage of the sub transmission 30 are changed, and finally, the speed change of the transmission 4 is performed.

The transmission efficiency of the variator 20 is best when the speed ratio is 1.0. This is because when the shift ratio of the variator 20 shifts from 1.0 to the side in which the transmission ratio becomes large (hereinafter referred to as 'the transmission ratio side') or the side in which the transmission ratio becomes smaller (hereinafter referred to as the 'transmission ratio small side'), the contact radius with the V belt 23 becomes Since the amount of increase in friction between the pulley and the belt in the pulley being reduced is greater than the amount of friction decrease between the pulley and the belt in the pulley in which the contact radius with the V belt 23 is increased, the friction between the pulley and the belt as a whole is increased. This is because the delivery efficiency of the variator 20 deteriorates.

In consideration of the transmission efficiency characteristics of the variator 20, the transmission controller 12 uses the driving conditions of the vehicle (vehicle speed VSP) so as to increase the frequency of use in the vicinity of the transmission ratio 1.0 where the variator 20 has the best transmission efficiency. ), Primary pulley rotational speed (Npri), throttle opening amount (APS)], and the variator 20 and the sub transmission 30 are shifted.

3 is a diagram illustrating a shift map of a continuously variable transmission for a vehicle according to an exemplary embodiment of the present invention.

In this shift map, the operating point of the transmission 4 is determined based on the vehicle speed VSP and the primary pulley rotational speed Npri. The inclination of the line connecting the operating point of the transmission 4 and the zero point of the shift map indicates the speed ratio of the transmission 4. At this time, the transmission ratio of the transmission 4 is the total transmission ratio (TotalRatio) obtained by multiplying the transmission ratio of the variator 20 by the transmission ratio of the sub transmission 30.

Then, the primary pulley target rotational speed is determined by the vehicle speed VSP and the throttle opening amount APS, and when divided by the output speed of the current transmission 4, the total target transmission ratio TotalRatio_Tar is obtained.

3 shows only a partial line (APS = 4/8) as an example. However, in this shift map, a shift line is set for each throttle opening amount APS, similar to the shift map of a conventional belt type continuously variable transmission. The shift of the transmission 4 is performed in accordance with the shift line selected according to the throttle opening amount APS.

When the transmission 4 is in the low speed mode, the transmission 4 shifts between the low speed mode lowest line obtained by maximizing the transmission ratio of the variator 20 and the low speed mode highest line obtained by minimizing the transmission ratio of the variator 20. can do. At this time, the operating point of the transmission 4 moves in the A area and the B area.

On the other hand, when the transmission 4 is in the high speed mode, the transmission 4 is between the high speed mode lowest line obtained by maximizing the transmission ratio of the variator 20 and the high speed mode highest line obtained by minimizing the transmission ratio of the variator 20. You can shift. At this time, the operating point of the transmission 4 moves in the B area and the C area.

The speed ratio of each speed change stage of the auxiliary transmission 30 is set so that the speed ratio corresponding to the low speed mode highest line (low speed mode maximum speed ratio) becomes smaller than the speed ratio corresponding to the high speed mode lowest line (high speed mode minimum speed ratio). Accordingly, the low speed mode range, which is the range of the overall transmission ratio of the transmission 4 that can be taken in the low speed mode, and the high speed mode range that is the range of the overall transmission ratio of the transmission 4, which can be taken in the high speed mode, partially overlap, When the operating point of (4) is in the B area between the high speed mode lowest line and the low speed mode highest line, the transmission 4 can select any of the low speed mode and the high speed mode.

In addition, on this shift map, the mode conversion shift line (1-2 shift line of the subtransmission) for shifting the sub transmission 30 is set between the high speed mode lowest line and the low speed mode highest line.

The overall speed ratio (hereinafter referred to as 'mode conversion speed ratio (MCratio)') corresponding to the mode shift transmission line is a middle value between the minimum speed ratio of the high speed mode and the maximum speed ratio of the low speed mode. Divided by 2.

Then, when the operating point of the transmission 4 crosses the mode change shift line, that is, when the total transmission ratio TotalRatio of the transmission 4 changes across the mode change shift line, the transmission controller 12 controls the mode change shift. Is done. In this mode conversion shift control, the transmission controller 12 shifts the sub transmission 30 and changes the transmission ratio of the variator 2 in the direction opposite to the direction in which the transmission ratio of the sub transmission 30 changes.

For example, when the total transmission ratio (TotalRatio) of the transmission (4) becomes smaller than the mode conversion transmission ratio (MCratio), the transmission controller 12 shifts the speed of the sub transmission 30 from 1 speed to 2 speeds. Is changed (sub transmission 1 to 2), and the speed ratio of the variator 20 is changed to the speed ratio side. On the contrary, when the total transmission ratio (TotalRatio) of the transmission (4) becomes smaller than the mode conversion transmission ratio (MCratio), the transmission controller 12 changes the speed of the sub transmission 30 from 2 speeds to 1 speed. (Sub transmission 2 to 1 shift), and the speed ratio of the variator 20 is changed to the speed ratio small side.

At the time of mode shift, changing the transmission ratio of the variator 20 in the opposite direction to the change of the transmission ratio of the sub transmission 30 is according to the change in the input rotation caused by the step of the entire transmission ratio of the transmission 4. This is to suppress the feeling of discomfort.

4 is a flowchart of a method for controlling a continuously variable transmission for a vehicle according to an exemplary embodiment of the present invention. Hereinafter, a stepless transmission control method for a vehicle according to an exemplary embodiment of the present invention will be described with reference to FIG. 4.

Operation status information reading step ( S10 ):

In the operation state information reading step (S10), the transmission controller 12 receives the primary pulley rotation speed Npri, the secondary pulley rotation speed Nsec, the transmission output speed No, the vehicle speed VSP, and the throttle opening amount from various sensors. (APS) receives and reads information on the engine torque Te.

The overall target speed ratio setting step ( S20 ):

Using the information acquired in the operation state information reading step S10, that is, the primary pulley rotation speed Npri and the vehicle speed VSP, and the shift map stored in the storage device 122 (see FIG. 3), The total target speed ratio TotalRatio_Tar, which is the speed ratio to be achieved next, is calculated from the driving state of.

mode  Transform judgment step ( S31 , S32 ):

In the transmission controller 12, it is determined whether the entire transmission ratio of the transmission 4 crosses the mode conversion transmission ratio MCratio. This determination is made by comparing the total target speed ratio with the mode conversion speed ratio.

Sub transmission  Shift judgment step ( S41 , S42 ):

When the total target speed ratio TotalRatio_Tar of the transmission 4 passes the mode conversion speed ratio MCratio, a mode conversion shift occurs, and the method of changing the speed of the sub transmission 30 is determined. For example, if it is determined that the total target transmission ratio is smaller than the mode conversion transmission ratio (S31), it is determined that the speed change stage of the auxiliary transmission 30 should be changed from one speed to two speeds (S41). In addition, if it is determined that the total target speed ratio is greater than the mode conversion speed ratio (S32), it is determined that the speed change stage of the auxiliary transmission 30 should be changed from 2 speeds to 1 speed (S42).

On the other hand, in the mode conversion determination step (S31, S32), if the total target transmission ratio is the same as the mode conversion transmission ratio, since the transmission controller 12 does not change the shift stage of the sub transmission 30, the ordinary of the variator 20 is normal. Only phosphor shift is performed.

That is, the target speed ratio of the variator 20 is set (S80), and the shift of the variator 20 is controlled (S90).

Innershire Phase ( Inertia Phase ) Judgment step ( S51 , S52 ):

It is determined whether the secondary pulley rotational speed Nsec, which is the input speed of the sub transmission 30, is an inertia phase that is actually changed by the shift of the sub transmission 30.

If it is not the inertia phase, the process returns to the above-described sub transmission shift determination step, and if it is the inertia phase, the process proceeds to the next step.

Variator  Shifting property setting step ( S61 , S62 ):

When the inertia phase is determined in the inertia phase determination steps S51 and S52, the gear ratio that the variator 20 must achieve after the mode conversion shift is completed, based on the total target gear ratio and the gear ratio after the shift of the sub transmission 30. The variator target transmission ratio is calculated.

And based on the deviation of the present transmission ratio and the target transmission ratio of the variator 20, when the transmission of the sub transmission 30 is completed, so that the transmission ratio of the variator 20 becomes the target transmission ratio of the variator 20. The target shift characteristic of (20) is set, and the target shift time of the variator 20 such as the target shift time of the variator 20 and the shift speed increase / decrease by the throttle opening degree change amount ΔAPS and the sub transmission input speed Nsec. You can set the property.

At this time, the target transmission time of the sub transmission 30 may be a fixed value, may be changed according to the vehicle speed VSP, the engine torque Te, the sub transmission 30 input speed Nsec, and the variator ( The speed ratio of 20 may be calculated based on the total speed ratio and the speed ratio of the speed change stage of the sub transmission 30.

Cooperative control phase ( S71 , S72 ):

In the cooperative control step, the shift of the sub-transmission 30 and the shift of the variator 20 are started by the transmission controller 12.

That is, when the speed change stage of the sub transmission 30 is changed from 1 speed to 2 speed, the speed ratio of the variator 20 is changed to the transmission ratio side (S71), and the speed change stage of the sub transmission 30 is 1 to 2 speed. If the speed is changed, the speed ratio of the variator 20 is changed to the speed ratio small side (S72).

At this time, by shifting the variator 20 in accordance with the shift characteristics set in the variator shift characteristic setting steps S61 and S62, the shift of the variator 20 is completed at the same time as the shift of the sub transmission 30 is completed.

5 and 6 illustrate the details of such cooperative control. FIG. 5 is a view illustrating changes in target speed ratios and actual speed ratios of the variator and the auxiliary transmission in the inertia phase, and FIG. 6 is a view of the present invention. Fig. 1 is a block diagram showing a PI control method of the variator and the sub-transmission according to the embodiment.

The variator 20 feeds back to the PI controller using an error Errv of the target shift ratio Rtarv of the variator 20 and the actual shift ratio Rreav of the variator 20. -back) control.

At this time, the sub transmission 30 obtains the target transmission ratio Rtarc of the sub transmission 30 by dividing the actual transmission ratio Rreav of the pre-calculated variator 20 by the total target transmission ratio TotalRatio_Tar, and the variator 20 Like the transmission ratio control, the feedback is controlled by the PI controller using the actual transmission ratio Rreac and the error Errc of the sub transmission 30.

At this time, for accurate control of the sub transmission 30, using the error (Errc) of the sub-transmission 30, the error of the variator 20, the progress of the gear change of the sub-transmission 30 (Hsyc) Implement the control to adjust the gain value of the PI controller by a scheduler (Gain Scheduler).

1: engine
4: Transmission
10: oil pump
11: hydraulic control circuit
12: transmission controller
20: variator
21: primary pulley
22: secondary pulley
23: V-belt
23a, 23b: hydraulic cylinder
30: sub transmission

Claims (6)

A control method of a continuously variable transmission for a vehicle comprising a belt continuously variable transmission and a secondary transmission including a first transmission stage and a second transmission stage having a smaller transmission ratio than the first transmission stage as a forward shift stage. In
In the mode change shift in which the sub transmission is made, the target transmission ratio of the sub transmission is determined by the actual transmission ratio of the belt type continuously variable transmission.
Changing the speed ratio of the belt continuously variable transmission, the stepless transmission control method for a vehicle, characterized in that the feedback is controlled through the PI controller using the error of the target speed ratio and the actual speed ratio of the belt continuously variable transmission.
The method according to claim 1,
And a target transmission ratio of the secondary transmission by dividing an entire target transmission ratio of the transmission including the belt continuously variable transmission and the secondary transmission by the actual transmission ratio of the belt continuously variable transmission.
delete The method according to claim 1,
Changing the speed ratio of the sub-transmission, feedback control via a PI controller using the error between the target speed ratio and the actual speed ratio of the sub-transmission.
The method of claim 4,
The shift ratio error of the belt continuously variable transmission, the shift ratio error of the sub-transmission, and the shift progress degree of the sub-transmission are input to a gain scheduler, and the gain value of the PI controller controlling the shift ratio change of the sub-transmission by the gain scheduler. Stepless transmission control method for a vehicle, characterized in that the adjustment.
A control method of a continuously variable transmission for a vehicle comprising a belt continuously variable transmission and a secondary transmission including a first transmission stage and a second transmission stage having a smaller transmission ratio than the first transmission stage as a forward shift stage. In
A total target speed ratio setting step of setting a speed ratio of the belt-type continuously variable transmission and the entire sub transmission to a total target speed ratio according to a driving state of a vehicle;
A mode conversion determining step of determining whether the overall target speed ratio changes across the mode conversion speed ratio;
A sub-transmission shift determination step of determining a method of changing a shift stage of the sub-transmission when the total target shift ratio changes across a mode conversion shift ratio;
An inertia phase determination step of determining whether an input speed of the sub transmission is changed by the shift stage change determined in the sub transmission shift determination step;
A variator shift characteristic setting step of setting a target shift characteristic of the belt-type continuously variable transmission when it is determined as an inertia phase in the inertia phase determination step; And
And a cooperative control step of changing the speed ratio of the sub-transmission and changing the speed ratio of the belt-type continuously variable transmission in a direction opposite to the direction in which the speed ratio of the sub-transmission is changed.

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