KR20100118277A - Power off down shift control method for auto transmission - Google Patents

Abstract

PURPOSE: A method for controlling a power off down shift for an automatic transmission is provided to reduce an engine brake and a transmission impact by determining the state of a power off down shift by considering an output RPM change and a turbine RPM-engine RPM. CONSTITUTION: If a down shift signal is inputted, it is determined whether a transmission lever is a D range state or not(S10). If a transmission lever is a D range state, it is determined whether a power off state is checked. If the power off state is checked, it is determined whether the output RPM change is below a second preset value(S30). If the output RPM change is below the second preset value, it is determined whether a turbine-engine slip is below a third preset value(S40). If the turbine engine slip quantity is below a third preset value, the power off down shift is performed(S50). If the turbine-engine slip quantity exceeds a third preset value, the power off is determined.

Description

Power off down shift control method for automatic transmission {POWER OFF DOWN SHIFT CONTROL METHOD FOR AUTO TRANSMISSION}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission, and more particularly, to a power-off downshift control method for an automatic transmission in which a shift shock is suppressed when a downshift operation is made.

The automatic transmission sets an arbitrary target shift stage based on the shift pattern map table set according to the vehicle speed and the opening degree of the throttle valve, and then the hydraulic duty control controls various operating elements of the transmission gear mechanism, that is, the release clutch and By operating the clutch on the engagement side to automatically shift to the target shift stage, it provides convenience of operation.

As such, when the vehicle equipped with the automatic transmission providing convenience to the driver is traveling by another line, that is, in the driving state before the stop in which the vehicle is driven by inertia without driving the accelerator pedal, A lowering power off down shift occurs.

In addition, in the case of an automatic transmission vehicle, the vehicle is generally operated at a state in which the rotational speed of the turbine in the transmission is higher than the engine rotational speed (engine rotational speed Ne <turbine rotational speed Nt) while driving in the other line.

This is because the vehicle is driven by the inertia of the vehicle rather than the vehicle is driven by the power of the engine, this state is called an inertial driving state.

The automatic transmission according to the prior art has a state in which the engine speed Ne is higher than the turbine speed Nt and the engine speed Ne is higher than the turbine speed Nt when the power off-down shift is performed during inertia driving. When the vehicle drive system is reversed, the direction of the force is reversed, and the reverse of the driving force is generated, thereby causing a sense of engine brake and shifting shock due to a back lash of the drive system.

Therefore, there is a need for improvement.

The present invention has been made to solve the above problems, and an object thereof is to provide a power off down shift control method for an automatic transmission to suppress an engine brake feeling and a shift shock generated when a power off down shift is performed. .

In order to achieve the above object, the present invention, a shift lever determination step of determining whether the shift lever is in the D range state when the down shift signal is input; A power-off judging step of determining whether the shift lever is in the power-off state when the shift lever is in the D-range state; A first change rate determining step of determining whether the output RPM change rate is less than or equal to the second set value when the power is off; A first slip determination step of determining whether a turbine-engine slip amount is less than or equal to a third set value when the output RPM change rate is less than or equal to a second set value; And a switching step of performing a power-off down shift if the turbine-engine slip amount is equal to or less than a third set value; When the turbine-engine slip amount exceeds a third set value, the power-off determination step for the automatic transmission is provided.

In addition, in the shift lever determination step of the present invention, if the shift lever is not in the D range state, a step of maintaining the shift stage is provided.

In addition, in the power-off determination step of the present invention, when the amount of operation displacement of the accelerator pedal exceeds the first set value, it provides a power off down shift control method characterized in that the shift to the step of maintaining the shift stage.

The present invention may further include a second change rate determining step of determining whether the output RPM change rate is less than or equal to a fourth set value when the output RPM change rate exceeds a second set value in the first change rate determining step; And a second slip determination step of determining whether the turbine-engine slip amount is less than or equal to a fifth set value when the output RPM change rate is less than or equal to a fourth set value in the second change rate determining step; In the second slip determination step, if the turbine-engine slip amount exceeds a fifth set value, the power-off determination step for an automatic transmission is provided.

The present invention may further include a third change rate determining step of determining whether the output RPM change rate is less than or equal to a sixth set value when the output RPM change rate exceeds a fourth set value in the second change rate determining step; And a third slip determination step of determining whether the turbine-engine slip amount is less than or equal to a seventh set value when the output RPM change rate is equal to or less than a sixth set value; In the third slip determination step, if the turbine-engine slip amount exceeds a seventh set value, the power-off determination control method for an automatic transmission is provided.

In addition, in the third change rate determination step of the present invention, if the output RPM change rate exceeds the sixth set value provides a power off down shift control method for an automatic transmission, characterized in that for switching to the power off determination step.

The power off down shift control method for an automatic transmission according to the present invention performs a power off down shift in consideration of the output RPM change rate of the automatic transmission and the slip amount between the turbine RPM and the engine RPM when the down shift is performed while the vehicle is inertial driving. Since it is determined whether or not the engine RPM and turbine RPM is reversed, the power off down shift is performed to reduce the engine brake feeling and shift shock.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of a power off down shift control method for an automatic transmission according to the present invention.

In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of description.

In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or custom.

Therefore, definitions of these terms should be made based on the contents throughout this specification.

1 is a block diagram showing a power off down shift control apparatus for an automatic transmission according to an embodiment of the present invention, Figure 2 is a power off down shift control method for an automatic transmission according to an embodiment of the present invention is shown Flowchart.

1 and 2, in the power-off downshift control method for an automatic transmission according to an embodiment of the present invention, when a downshift signal is input, a shift lever determining step (S10) of determining whether a shift lever is in a D range state. And a power-off determination step (S20) of determining whether the shift lever is in the power-off state when the shift lever is in the D-range state, and a first change rate determination step (S30) of determining whether the output RPM is less than or equal to the second set value when the shift lever is in the power-off state. A first sleep determination step S40 of determining whether the turbine-engine slip amount is less than or equal to the third set value when the output change rate is less than or equal to the second set value; and a switching step of performing a power-down downshift if the turbine-engine slip amount is less than or equal to the third set value; (S50).

When the down shift signal is input, the position of the shift lever is detected from the shift lever detection sensor 90 to determine whether the vehicle is moving forward. When the shift lever is positioned at the N range even when the vehicle is moving forward, the driving force of the engine is automatically Since it is not being transmitted to the transmission, it is not necessary to change the shift stage, so it detects whether the shift lever is in the D range state.

When the shift lever is in the D-range state, it is determined whether the turbine RPM has a power-off state higher than the engine RPM, that is, whether the inertia of the vehicle is performed, which detects the displacement amount of the accelerator pedal that determines the engine throttle valve opening amount. The power-off determination step S20 is performed by detecting whether the brake pedal is operated to determine whether the vehicle is decelerating.

In the power-off judging step S20, it is determined whether the operation displacement amount of the accelerator pedal detected by the APS (Accelerator Pedal Sensor: 30, or less APS) is less than or equal to the first set value, and the brake pedal detects the brake pedal by the brake sensor 50. This operation is detected.

At this time, if the displacement amount of the accelerator pedal is less than or equal to the first set value, since the opening amount of the throttle valve is less than or equal to the predetermined value, the output of the engine is reduced, and the turbine RPM is maintained higher than the engine RPM. Since it is losing, it is determined that this state is a power off state.

If the APS value is less than the first set value and the brake pedal is operated in the power-off determination step S20, the first change rate determining step S30 is performed to determine whether the output RPM change rate of the automatic transmission is less than or equal to the second set value.

The first change rate determining step (S30) detects the output RPM change rate of the automatic transmission by the RPM sensor 70 to determine whether the output RPM is less than or equal to the second set value, thereby considering the output RPM change rate of the automatic transmission to power off down. Decide whether to proceed with the shift.

When the output RPM change rate of the automatic transmission is less than or equal to the second set value in the first change rate determination step (S30), the first slip determination step (S40) is performed to determine whether the turbine-engine slip amount is less than or equal to the third set value. If the turbine-engine slip amount is less than or equal to the third set value in step S40, the switching step S50 is started in which the power-off down shift is started.

Here, since the method for determining the turbine-engine slip amount can be easily implemented by those skilled in the art having recognized the technical configuration of the present invention, specific drawings and descriptions thereof will be omitted.

As described above, the power off down shift is determined in consideration of the APS value, the brake pedal operation, the output RPM change rate of the automatic transmission, and the turbine-engine slip amount, so that the engine RPM is higher than the engine RPM. The power off down shift can be made before a reversal occurs where the RPM of the turbine is higher than the turbine RPM. Therefore, it is possible to reduce the engine brake feeling and shift shock generated by performing the downshift operation during inertia driving of the vehicle.

If the shift lever is in the N range or the R range in the shift lever determination step S10, the shift of the shift stage is not required, and thus the step S60 of maintaining the current shift stage is performed.

In addition, when the operation displacement amount of the accelerator pedal exceeds the first set value or the brake pedal is not operated in the power-off determination step S20, the step S60 of maintaining the shift stage is performed, so that the engine RPM exceeds the turbine RPM. This prevents the downshift from proceeding in the state.

In the first change rate determination step (S30), if the output RPM change rate exceeds the second set value, the second change rate determination step (S32) for determining whether the output RPM change rate is less than or equal to the fourth set value, and in the first change rate determination step (S32). If the output RPM change rate is less than or equal to the fourth set point, a second slip determination step S42 is performed to determine whether the turbine-engine slip amount is less than or equal to the fifth set point.

If the turbine-engine slip amount is less than or equal to the fifth set value in the second slip determination step (S42), since the turbine RPM is maintained at an inertia driving state higher than the engine RPM, the power off-down shift proceeds.

In addition, when the output RPM change rate exceeds the fourth set value in the second change rate determination step S32, the third change rate determination step S34 for determining whether the output RPM change rate is less than or equal to the sixth set value, and the output RPM change rate is the sixth set value If not, the third slip determination step S44 for determining whether the turbine-engine slip amount is less than or equal to the seventh set value is performed.

When the turbine-engine slip amount is less than or equal to the seventh set value in the third slip determination step S44, the turbine RPM is maintained at an inertia driving state higher than the engine RPM, and thus the power off-down shift is performed.

Therefore, in consideration of the output RPM change rate of the automatic transmission detected from the RPM sensor 70, it is determined whether the power-off down shift is progressed, and the output RPM change rate section in which the power off-down shift process is possible is divided into three sections. The turbine-engine slip amount corresponding to the section is set.

Thus, when the output RPM change rate of the automatic transmission belongs to the three sections, the switching step (S50) in which the power-off down shift is performed only when the slip amount of the turbine-engine corresponding to each section is satisfied.

When the output RPM change rate of the automatic transmission exceeds the sixth set value in the third slip determination step S44, the power off down shift does not proceed and the power off determination step S20 is performed and the power off down shift only when the above conditions are satisfied. Proceeds.

Also, when the output RPM change rate of the automatic transmission corresponds to three sections, that is, when the conditions of the second change rate determination step S32 and the third change rate determination step S34 are satisfied in the first change rate determination step S30. The turbine-engine slip amount corresponding to each change rate is determined. The turbine-engine slip amount exceeds the third set value in the first slip determination step S40 and the fifth set value in the second slip determination step S42. If the value exceeds the seventh set value in the third slip determination step S44, the power-off down shift does not proceed and the process is switched to the power-off determination step S20.

The shift lever determination step (S10) to the switching determination step (S44) is the first to seventh set value input to the control unit 10 APS (30), brake sensor 50, RPM sensor 70, And a value measured by the shift lever sensor 90, and when the power-off down shift is determined, the solenoid 80 that determines whether to supply hydraulic pressure to the friction element is driven according to the signal of the controller 10. Off-down shift is in progress.

When the power-down shift is performed by the above control method, the position of the shift lever, the APS value, whether the brake pedal is operated, the output RPM change rate of the automatic transmission, and the turbine-engine slip amount are taken into consideration. Since the shift stage switching operation is performed in a state of not being inverted higher than the turbine RPM, it is possible to provide a power off-down shift control method for an automatic transmission that reduces shift shock generated when the shift operation is performed.

Here, the output RPM change rate of the automatic transmission that can proceed the power off down shift can be changed to divide into more than three sections or less than three sections, which can be easily changed by those skilled in the art aware of the technical configuration of the present invention Since it can be carried out by the specific drawings or description of the other embodiments will be omitted.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. Will understand.

In addition, although the power off down shift control method for an automatic transmission of a vehicle has been described as an example, this is merely exemplary, and the power off down shift control method for an automatic transmission of the present invention may be used for a product other than the vehicle.

Therefore, the true technical protection scope of the present invention will be defined by the claims below.

1 is a block diagram illustrating a power off down shift control apparatus for an automatic transmission according to an embodiment of the present invention.

2 is a flowchart illustrating a power off down shift control method for an automatic transmission according to an embodiment of the present invention.

<Explanation of symbols on main parts of the drawings>

10: control unit 30: APS

50: brake sensor 70: RPM sensor

80: solenoid

Claims (6)

A shift lever determining step of determining whether the shift lever is in the D range state when a down shift signal is input; A power-off judging step of determining whether the shift lever is in the power-off state when the shift lever is in the D-range state; A first change rate determining step of determining whether the output RPM change rate is less than or equal to the second set value when the power is off; A first slip determination step of determining whether a turbine-engine slip amount is less than or equal to a third set value when the output RPM change rate is less than or equal to a second set value; And A switching step of proceeding a power off down shift if the turbine-engine slip amount is less than or equal to a third set value; And the turbine-engine slip amount is switched to the power-off judging step when the turbine-engine slip amount exceeds a third set value. The method of claim 1, And if the shift lever is not in the D range state in the shift lever determining step, maintaining the shift stage is performed. The method of claim 1, And in the power-off judging step, when the amount of operation displacement of the accelerator pedal exceeds a first set value, the shift-off stage is maintained. The method of claim 1, A second change rate determining step of determining whether the output RPM change rate is less than or equal to a fourth set value when the output RPM change rate exceeds a second set value in the first change rate determining step; And A second slip determination step of determining whether the turbine-engine slip amount is less than or equal to a fifth set value when the output RPM change rate is less than or equal to a fourth set value in the second change rate determining step; And in the second slip determination step, when the turbine-engine slip amount exceeds a fifth set value, the power-off determination step is switched to the power-off determination step. The method of claim 4, wherein A third change rate determining step of determining whether the output RPM change rate is less than or equal to a sixth set value when the output RPM change rate exceeds a fourth set value in the second change rate determining step; And A third slip determination step of determining whether the turbine-engine slip amount is less than or equal to a seventh set value when the output RPM change rate is equal to or less than a sixth set value; And in the third slip determination step, when the turbine-engine slip amount exceeds a seventh set value, the power-off determination step for the automatic transmission is characterized in that it is switched. The method of claim 5, And in the third change rate determining step, when the output RPM change rate exceeds a sixth set value, the power off determination step is switched to the power off determining step.

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