KR19980017021A - Skip shift control method of automatic transmission - Google Patents

Abstract

In the case of skipping at the second speed when driving at four speeds, the speed response response is increased without passing through the three speed shift stages. Third and fourth provided for port conversion of the pressure control valve to turn off and on the first and second solenoid valves for performing port conversion of the shift control valve, respectively, and to generate a control pressure at an initial duty value set at power on; The solenoid valve is duty-controlled according to the rate of change of turbine speed over time, and when the power is turned off, the third and fourth solenoid valves set when the power is turned off while the first and second solenoid valves are turned off. Skip shift control method in which the third and fourth solenoid valves are synchronously completed by duty control after a predetermined time since the start of the shift at the initial duty rate Provided.

Description

Skip shift control method for automatic transmission

1 is a view showing the hardware configuration of the shift control unit of the hydraulic control apparatus according to the present invention.

2 is a view showing a hydraulic system of the hydraulic control apparatus according to the present invention, and a hydraulic circuit diagram showing a process of skipping shifting from four speeds to two speeds at power-on.

3 is a flowchart for explaining a shift control operation of the hydraulic control apparatus according to the present invention.

4 is a diagram showing the relationship between the first solenoid valve and time in the control according to FIG.

FIG. 5 is a diagram showing a relationship between a second solenoid valve and time in the control according to FIG.

FIG. 6 shows the relationship between the third solenoid valve and time in the control according to FIG.

FIG. 7 is a view showing a relationship between a fourth solenoid valve and time in the control according to FIG.

8 is a view showing a variation of oil pressure according to a shift time in the control according to FIG.

9 is a view showing a hydraulic system of the hydraulic control apparatus according to the present invention, and a hydraulic circuit diagram showing an initial process of skipping shifting from four speeds to two speeds at power off.

10 is a diagram showing a hydraulic system of the hydraulic control apparatus according to the present invention, wherein the hydraulic circuit diagram shows a terminal process of skipping shifting from four speeds to two speeds at power off.

FIG. 11 is a view showing a relationship between a first solenoid valve and time during control according to FIG.

FIG. 12 is a view showing a relationship between a second solenoid valve and time in the control according to FIG.

FIG. 13 is a view showing a relationship between a third solenoid valve and time in the control according to FIG.

FIG. 14 is a view showing a relationship between a fourth solenoid valve and time in the control according to FIG.

FIG. 15 is a view showing a variation of oil pressure according to a shift time in the control according to FIG.

FIG. 16 is a view for explaining a process of performing a conventional shift control by skipping from the fourth speed to the second speed.

The present invention relates to a shift control method of an automatic transmission for a vehicle, and more particularly, a shift shifting speed can be directly shifted to 2 speeds without passing through 3 speeds when skipping from 4 speeds to 3 speeds. The present invention relates to a skip shift control method capable of 4-2 skip control between all the sections by varying the control according to the driven conditions, and capable of independent control.

The automatic transmission for a vehicle has a torque converter and a multistage transmission gear mechanism connected to the torque converter, and a hydraulically operated friction element for selecting one of the gear stages of the transmission gear mechanism according to the driving condition of the vehicle. It is included.

The hydraulic control system of an automatic transmission for a vehicle has a function of operating a hydraulic pressure generated from an oil pump by selecting a friction element through a control valve.

The hydraulic control system is a pressure control means for adjusting the oil pressure generated from the oil pump, manual and automatic shift control means for forming a shift mode, and a hydraulic pressure for adjusting the shift feeling and responsiveness to form a smooth shift mode when shifting Control means, damper clutch control means for actuating the damper clutch of the torque converter, and hydraulic distribution means for distributing an appropriate hydraulic supply to each friction element.

The hydraulic control means adjusts the supply line pressure, the torque converter supply pressure, the solenoid valve supply pressure, and the like acting on the friction element. The hydraulic pressure substantially affects the feeling of shifting.

In order to facilitate the understanding of the present invention, a process of performing a skip shift from the fourth speed to the second speed in the conventional hydraulic control apparatus will be described with reference to FIG. 16.

It includes a torque converter 100 for receiving torque from the engine and converting the torque to the transmission side, and an oil pump 102 for generating and discharging the oil necessary for the torque converter and the shift stage control and oil for lubrication.

A pressure regulating valve 106 generated from the oil pump 102 to make the hydraulic pressure flowing along the conduit 104 at a constant pressure, and a torque converter control valve for regulating the pressure of the torque converter and the lubricating oil at a constant pressure ( 108, and a flow path that can be supplied to the damper clutch control valve 110 to increase the power transmission efficiency of the torque converter.

And some of the oil generated from the oil pump 102 is a reducing valve 112 to maintain the pressure at all times lower than the line pressure, and a manual for switching the flow while operating in conjunction with the position of the selector lever in the driver's seat A flow path that can be supplied to the valve 114 is configured.

The constant hydraulic pressure reduced in the reducing valve 14 constitutes a flow path that can be used as a control pressure of a high-low pressure valve (not shown) which minimizes the driving loss of the oil pump by lowering the line pressure in the high speed stage. In addition, some of the hydraulic pressure is supplied to the pressure control valve 116 to constitute a flow path that can be used as a control pressure.

A part of the hydraulic pressure supplied to the pressure control valve 116 makes a flow path that can use the control pressure of the N-R control valve 118 to reduce the shift shock when the mode is changed from the neutral range to the reverse range.

The first solenoid valve S1 and the second solenoid valve which are controlled on / off by the transmission control unit TCU in the pipeline 120 through which hydraulic pressure flows when the manual valve 114 is in the travel D range. The shift control valve 122 which switches a flow path by the action of S2 is connected, and is comprised so that hydraulic pressure may be supplied.

The first pipe line 124 is in communication with the pipe line 120 is configured to supply the hydraulic pressure to the pressure control valve 116, the shift control valve 122 is a second speed pipe 126, 3 The fast pipe path 128 and the four speed pipe path 130 are connected to each other so as to supply control hydraulic pressure to the plurality of shift valves for respective shift stage control.

That is, the second speed pipe 126 is configured to be supplied to the left end port of the 1-2 shift valve 132 to control the valve, and the third speed pipe 128 is a 2-3 / 4-3 shift valve ( It is configured to be supplied to the left end port of the 134 to control the valve, the four-speed pipeline 130 is supplied to the left end port of the end clutch valve 136 and the rear clutch release valve 138 to control each valve It is configured to be controlled.

On the other hand, the pressure control valve 116 is configured such that the flow path switching can be performed by the third solenoid valve (S3), the damper clutch control valve 110 is the flow path by the fourth solenoid valve (S4) It has a configuration that can switch.

The hydraulic pressure supplied to the pressure control valve 116 is controlled by the third solenoid valve S3 to change the flow path so that the ND control reduces the shift shock when the selector lever is selected as the driving range. The flow path is configured to supply hydraulic pressure to the rear clutch path C1 which is the first friction element through the valve 140.

The above-mentioned rear clutch release valve 138 is installed in the flow path connecting the ND control valve 140 and the rear clutch path C1 to supply hydraulic pressure to the rear clutch or to discharge the supplied hydraulic pressure. do.

In addition, the pressure control valve 116 constitutes a flow path capable of supplying hydraulic pressure to the kick-down servo C2 which is a second friction element acting as a reaction force element of the second speed via the 1-2 shift valve 132.

In addition, some of the hydraulic pressure via the 1-2 shift valve 132 passes through the 2-3 / 4-3 shift valve 134 and the front clutch C3 which is a third friction element acting as a third speed input element. And a flow path that can be supplied to the release side chamber of the kick-down servo C2, and some of the hydraulic pressure controls the end clutch valve 136 so that the hydraulic pressure flowing to the third speed pipe 128 is fourth. It constitutes a flow path that can be supplied to the end clutch (C4) which is a friction element.

When the manual valve 114 is in the reverse range, the fifth friction element C5 acting as a reaction element in the reverse shift stage via the 1-2 shift valve 36 is supplied with the hydraulic pressure supplied to the reverse first control pipe 142. The second control conduit 144 is connected to the manual valve 114 for the operation of the third friction element C3 acting as an input element.

The second friction element C2 is provided with a kick-down switch 146 installed in the actuating side chamber and is turned off when the hydraulic pressure is supplied to the actuating side chamber h1, and is controlled to be on when the actuating side chamber h2 is supplied. It is configured to transmit the signal to the electronic control unit (TCU).

This hydraulic control device is a transmission of a power train having three clutch means for transmitting rotational power by hydraulic control, two brake means, and a compound planetary gear device applying a one-way clutch that can only rotate in one direction structurally. However, control can be performed.

Since such a power train can be used, a description of the configuration of the power train is omitted. However, it will be described which clutch means or brake means act on each shift stage.

In the driving range D1, the rear clutch C1 acts by hydraulic control and the one-way clutch restricts rotation in the opposite direction to the input. In the second speed, the rear clutch C1 transmits power and kicks down servo. At C3, the rear clutch C1, the front clutch C3 and the end clutch C4 act as input elements, and at the fourth speed, the end clutch C3 and the kick-down servo With the action of C2), the shift stage control is realized.

In the conventional hydraulic control device configured as described above, the hydraulic pressure of the fourth speed line 130 acting on the left port of the rear clutch release valve 138 when the skip shift is made at the second speed in the traveling (D) range four speed state is performed. Since the hydraulic pressure acting on the front clutch C3 is released to the right port of the rear clutch release valve 138, the spool of the valve moves to the left side in the drawing.

That is, the hydraulic pressure acting on the front clutch C3 pushes the valve spool of the rear clutch release valve so that the hydraulic pressure can be supplied to the rear clutch C1 at the same time, and the end clutch valve 136 through the third speed line 128. ), The hydraulic pressure is supplied to the end clutch (C4) to temporarily pass through the third speed.

At this time, the operating pressure of the front clutch is supplied to the release side chamber (h2) of the kick-down servo (C2) to release the operation of the kick-down servo.

After such control, the second solenoid valve S2 is controlled to be off, thereby releasing the hydraulic pressure flowing to the third speed line 128, so that the operating pressure of the end clutch C4 is quickly released, and simultaneously with the end clutch C3, The hydraulic pressure of the chamber on the release side of the kick-down servo C2 is released.

That is, during shifting from the third to the second speed, the operating pressure is released quickly without controlling the end clutch, and the back pressure is controlled by the pressure of the kick-down servo using the front clutch.

This control method has a problem of slow shift response since it shifts through 4 speeds when changing from 4 speeds to 2 speeds, and common control is performed regardless of driven conditions, that is, power on or off. Skip control is impossible, and when shifting from 4 to 3 speeds using the front clutch pressure when shifting, the rear clutch is operated without control and the end clutch is released quickly when shifting from 3 to 2 speeds. There is no

The present applicant has proposed a hydraulic control system capable of skipping shift in Korean Patent Application No. 94-7330. This system has a disadvantage in that the shift response is slow because it has to pass through the third speed when performing the shift shift from 4 to 2 speeds. There is this.

A hydraulic control system for solving this problem is proposed by the present applicant in Korean Patent Application No. 95-25936.

However, the hydraulic control system of Korean Patent Application No. 95-25936 does not disclose a control method in which a skip shift is performed from four speeds to two speeds according to a driven condition.

The present invention has been invented to solve the problems of the prior art as described above, the object of the present invention is to speed up the shift response when skipping shifting from the fourth to the second speed, driven conditions (power on / off state) According to the present invention, a shift control method of an entire transmission is possible by changing a shift shift, and a vehicle capable of independent control through an end clutch release control and a rear clutch operation control is provided.

In order to solve the problems of the prior art as described above, in the present invention, the control pressure, which is in communication with the manual valve and determines the shift stage according to the opening ratio and the vehicle speed of the throttle valve at the position of the selector lever, is 1 speed, 2 speed, and 3 speed. A shift control valve that can be supplied in each of the four speeds and four speeds; a reducing valve that generates a stable reference control pressure by generating a hydraulic pressure lower than the line pressure at all times; and a clutch and a brake to improve the feeling of shifting during shifting. A method of performing a skip shift from four speeds to two speeds in a hydraulic control apparatus of an automatic transmission for a vehicle including a transmission control unit for controlling one or more pressure control valves for generating a control pressure for controlling the coupling of the engine, the engine rotation After sensing the opening degree of the number and the throttle valve, it is determined whether it is in a power-on state, and the judgment value in said step In the case of ON, the steps of turning off and turning on the first and second solenoid valves for performing port conversion of the shift control valve, respectively, and for converting the port of the pressure control valve for generating a control pressure to improve the feeling of shifting at power-on, respectively. 3) varying the duty ratio of the third solenoid valve according to the rate of change of the turbine speed according to the time conversion of the solenoid valve; and the end operating at four speeds while supplying hydraulic pressure to the rear clutch after the above step. It provides a skip shift control method of an automatic transmission for a vehicle comprising the step of releasing the hydraulic pressure of the clutch.

In the case where it is determined that the power-off state is determined from the step of determining the power-on state, turning off all of the first and second solenoid valves for performing the port change of the shift control valve; Determining an initial duty ratio of the third and fourth solenoid valves related to the first and second duty cycles, changing the duty ratios of the third and fourth solenoid valves set at power-off, and after a predetermined time has passed since the start of the shift, Controlling the solenoid valve in the off state and the second solenoid valve in the on state, and activating the rear clutch and releasing the end clutch according to the duty ratio of the third and fourth solenoid valves. Provides a skip shift control method.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram illustrating control unit hardware of the present invention, and an ignition coil Ic for detecting an engine speed is connected to an input terminal of a transmission control unit RCU. This ignition coil outputs two pulses per revolution, and the engine speed is calculated.

In addition, a throttle position sensor TPS is connected to another input terminal to detect an opening ratio of the throttle valve, and a pulse generator Pg is connected to another input terminal to detect the rotational speed of the output shaft.

The output terminal of the transmission control unit (TCU) is electrically controlled so that the first solenoid valve (S1) and the second solenoid valve (S2) for controlling the port change of the shift control valve 28, and the first, The third solenoid valve S3 and the fourth solenoid valve S4 for controlling the port change of the two pressure control valves 20 and 22 are connected.

2 is a diagram illustrating a process of skipping shifting from 4 speeds to 2 speeds when powering on as a hydraulic control system according to the present invention. In the neutral (N) range, the hydraulic pressure related to shifting is substantially changed. It is also not supplied to the valve.

The electronically controlled hydraulic control system controls the shift stage by switching the flow paths of the respective valves by the action of solenoid valves that are on / off controlled or duty controlled by a transmission control unit (TCU) that receives the opening of the throttle valve and the vehicle speed signal. Is performed.

Such a hydraulic control system includes a torque converter 2 for receiving power from an engine and converting the torque to a transmission side, and an oil pump for generating and discharging the oil necessary for the torque converter and the shift stage control and oil for lubrication. ).

A pressure regulating valve 8 generated from the oil pump 4 to make the pressure of the oil flowing along the conduit 6 constant, and a torque converter control valve 10 regulating the pressure of the torque converter and the lubricating oil constant. ) And a flow path that can be supplied to the damper clutch control valve 12 for increasing the power transmission efficiency of the torque converter.

And some of the oil generated from the oil pump (4) is a reducing valve 14 to always maintain a lower pressure than the line pressure, and a manual for switching the flow path while operating in conjunction with the position of the selector lever in the driver's seat The flow path that can be supplied to the valve 16 is configured.

The constant hydraulic pressure reduced in the reducing valve 14 constitutes a flow path that can be used as a control pressure of the high-low pressure valve 18 which minimizes the driving loss of the oil pump by lowering the line pressure in the high speed stage. In addition, some of the hydraulic pressure is supplied to the first pressure control valve 20 and the second pressure control valve 22 to constitute a flow path that can be used as the control pressure.

And the lip nut of hydraulic pressure supplied to these twelfth, pressure control valve is making a flow path that can use the control pressure of the N-R control valve 24 to reduce the shift shock when the mode is changed from the neutral range to the reverse range.

The first solenoid valve S1 and the second solenoid valve S2 which are controlled on / off by the transmission control unit in the pipeline 26 through which the hydraulic pressure flows when the manual valve 16 is in the travel D range. The shift control valve 28 which switches a flow path by the function of the communication is connected so that hydraulic pressure may be supplied.

The shift control valve 28 is connected to the second speed pipe 30, the third speed pipe 32, and the fourth speed pipe 34 to supply control hydraulic pressure to the plurality of shift valves for the respective shift stage control. It is configured to be.

That is, the second speed pipe 30 is supplied to the left end port of the 1-2 shift valve 36 so as to control the valve, and the third speed pipe 32 is a 2-3 / 4-3 shift valve ( It is configured to be supplied to the left end port of 38) to control the valve, the four-speed pipe 34 is 2-4 / 3- and the right end port of the 2-3 / 4-3 shift valve 38 described above. It is configured to be supplied to the left end port of the four shift valve 40 and the left end port of the end clutch valve 42 to control each valve.

On the other hand, the first pressure control valve 20 is configured such that flow path switching can be performed by the third solenoid valve S3, and the second pressure control valve 22 is constituted by the fourth solenoid valve S4. It has the structure which can switch a flow path.

The first speed pipe 44 is branched to the pipe line 26 connected to the manual valve 16, and is supplied to the first pressure control valve 20 and the second pressure control valve 22 while the third and fourth solenoid valves ( A flow path that can be supplied to the first friction element C1, which is an input element of the first speed, via the 2-4 / 3-4 shift valve 40 is controlled by the control of S3 and S4.

And the 1st pressure control valve 20 comprises the flow path which can supply hydraulic pressure to the 2nd friction element C2 which acts as a reaction force element of a 2nd speed | rate through the 1-2 shift valve 36.

In addition, some of the hydraulic pressure via the 1-2 shift valve 36 described above may be supplied to the end clutch C3 which acts as a third speed input element using the 2-3 / 4-3 shift valve 38. The hydraulic pressure supplied to the third friction element C3 is configured to be supplied to the port 46 of the accumulator 43.

And when the manual valve 16 is in the reverse range, the fourth friction element (C4) acting as a reaction element in the reverse shift stage via the hydraulic pressure supplied to the reverse first control pipe line 50 via the 1-2 shift valve 36 The second control conduit 52 is connected to the manual valve 16 for the operation of the fifth friction element C5 which acts as an input element.

The reverse second control conduit 52 is provided with a check valve 53 so as to delay the hydraulic release when releasing the hydraulic pressure to improve the feeling of shifting.

The second friction element C2 is provided with a kick-down switch 54 in the actuating side chamber and is turned off when the hydraulic pressure is supplied to the actuating side chamber h1 and controlled to be in an on state when supplied to the releasing side chamber h2. It is configured to transmit the signal to the electronic control unit (TCU).

In the figure, reference numeral S5 denotes a solenoid valve that controls the damper clutch control valve.

This hydraulic control device is a transmission of a power train having three clutch means for transmitting rotational power by hydraulic control, two brake means, and a compound planetary gear device applying a one-way clutch that can only rotate in one direction structurally. However, control can be performed.

Since such a power train can be used, a description of the configuration of the power train is omitted, and only a description will be given of which clutch means or brake means act on each shift stage.

At speed D, the speed is controlled by the rear clutch C1 and hydraulic control, and the one-way clutch restrains rotation in the opposite direction to the input. In the second speed, the rear clutch C1 transmits power and kicks down servo ( C2) provides the reaction force, at the third speed, the rear clutch C1, the front clutch C3, and the end clutch C4 all act as input elements, and at the fourth speed, the end clutch C3 and the kick-down servo C2. ), The shift stage control is realized.

In order to perform the skip shift to the second speed while traveling at the fourth speed in the conventional hydraulic control device made as described above, the following control is performed.

In other words, first, when the driving rate of the throttle valve is rapidly reduced in the running D range 4 speed state and a skip shift control is required at 2 speeds, the transmission control unit performs control as shown in FIG. 2 speed control is completed.

First, the transmission control unit receives the signal transmitted from the ignition coil Ic and the signal transmitted from the throttle position sensor TPS in steps 100 and 110, respectively, to determine whether the power is on. You will be judged.

In this case, if the determination value is the power-on state, in step 130, the first solenoid valve S1 and the second solenoid valve S2 are controlled to be in an off state and an on state, respectively.

That is, in the fourth speed state, the first solenoid valve S1 is turned on and the second solenoid valve S2 is turned off to perform these controls in reverse. (See FIGS. 4 and 5)

Then, the initial duty ratio of the fourth solenoid valve S4 is set (step 140), and in step 150, the duty ratio of the fourth solenoid valve is changed by the rate of change of the turbine rotation speed with time.

As a result of the skip shift, the hydraulic pressure supplied to the 3rd speed line 32 and the 4th speed line 34 is released by such control, so that the valve spool and the end clutch valve of the 2-4 / 3-4 shift valve 4 are released. The valve spool of 42 is moved to the left in the figure.

By this control, the operating pressure of the end clutch C4 and the release chamber h2 of the kick-down servo C2 are linked to the operation of the accumulator 43 and the above-mentioned 2-4 / 3-4 shift valve and 2- It is released through the discharge port Ex provided in the conduit connecting the 3 / 4-3 shift valve (step 160).

Accordingly, as shown in FIG. 2, the skip shift is performed in the second speed state in which the rear clutch C1 and the kick-down servo C2 operate without passing through the third speed (step 170).

In addition, if it is determined in the step 120 that the power off state, the transmission control unit in step 180 to control both the first solenoid valve (S1) and the second solenoid valve (S2) in the off state.

Accordingly, the valve spool of the 2-4 / 3-4 shift valve 40 is moved to the left side as shown in the drawing while the hydraulic pressure of the fourth speed line 44 is released, and the valve of the 2-3 / 4-3 shift valve 38 is The spool moves to the right as seen in the figure, and the valve spool of the end clutch valve 42 moves to the left as seen in the figure.

At this time, the third and fourth solenoid valves S3 and S4 are set to an initial duty value in step 190. The hydraulic pressure is supplied to the rear clutch C1 by this control, which corresponds to the clutch initial filling time. do.

At the same time, the fourth solenoid valve S4 forms a flow path through which the hydraulic pressure can be supplied to the operating side chamber h1 of the end clutch C4 and the kick-down servo C2 while being duty controlled in step 200.

By this action, the hydraulic pressure is supplied to the actuation side chamber h1 and the release side chamber h2 of the kick down servo C2 while communicating with the operating pressure of the end clutch C4 to terminate the operation of the kick down servo.

This is the action to release the end clutch, and thus the kick-down servo is released to turn on the kick-down switch 54. In this way, when the switch is turned on, shifting starts as the initial stage of shifting is completed. See figure 9.

When the initial stage is completed, and after a predetermined time has passed by determining whether a predetermined time has elapsed after the shift is started in step 210, the first solenoid valve S1 described above is kept off in step 220, The second solenoid valve S2 is controlled in an on state.

In operation 230, the third and fourth solenoid valves S3 and S4 are controlled at the duty rate set when the power is turned off.

By this control, the hydraulic pressure of the 3rd speed line 32 is released and the valve spool of the 2-3 / 4-3 shift valve 38 is moved to the left side in the drawing.

At this time, the hydraulic pressure of the kick-down servo C2 is controlled by the third solenoid valve S3 to release the operation of the end clutch C4 and the kick-down servo C2.

When the control is completed, the release chamber h2 of the kick-down servo C2 is released, and the kick-down servo is operated again to realize step 240, and the synchronization is completed in step 250, and the state of FIG. It constitutes a flow path.

As described above, the hydraulic control apparatus and the control method according to the present invention can speed up the shift response because it does not go through the third speed when shifting from the fourth to the second speed, and is driven on (power on, power off). It is possible to control differently according to the 4-2 skip shift control between the whole.

Claims (2)

Shift control in communication with the manual valve so that the control pressure, which determines the gear shift stage according to the opening ratio and the vehicle speed of the throttle valve at the position of the selector lever, can be supplied in each of the 1st, 2nd, 3rd and 4th speeds. A reducing valve for generating a stable reference control pressure by generating a hydraulic pressure lower than the line pressure at all times, and one or more pressure control valves for generating a control pressure for controlling the coupling of the clutch and the brake to improve the feeling of shifting during shifting. In a method in which the hydraulic control device of an automatic transmission for a vehicle including a transmission control unit for controlling performs a skip shift from four speeds to two speeds, After detecting the engine speed and the opening rate of the throttle valve, determining whether the engine is in a power-on state, Turning off and on the first and second solenoid valves for performing port conversion of the shift control valve, respectively, when the judgment value in the above step is power on; The duty ratio of the third solenoid valve for performing a port change of the pressure control valve to generate a control pressure at power-on to change the duty ratio of the third solenoid valve according to the rotation rate change ratio of the turbine according to the time conversion. Steps, And releasing the hydraulic pressure of the end clutch operating at four speeds while supplying the hydraulic pressure to the rear clutch after the above step. 2. The method of claim 1, further comprising: turning off all of the first and second solenoid valves for performing port conversion of the shift control valve when it is determined that the power-off state is determined from the power-on state; Determining an initial duty ratio of the third and fourth solenoid valves related to the port change of the pressure control valve at power off; Changing the duty ratio of the third and fourth solenoid valves set at power off; Controlling the first solenoid valve to the off state / second solenoid valve to the on state after a predetermined time has passed since the start of the shift; And operating the rear clutch and releasing the end clutch according to the duty ratios of the third and fourth solenoid valves.