JP2004125106A - Speed change control method of automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed change control method of an automatic transmission capable of effectively preventing drawing shock of input rotation caused by increase of engine torque after synchronous decision during a power-off upshift. <P>SOLUTION: The number of input revolution of the automatic transmission is decreased to the number of input revolution in a high speed shift by increasing hydraulic pressure of an engaging element B1 at a designated slope. After detecting (synchronous decision) that the number of input revolution is decreased in a vicinal range of the number of input revolution at a high speed shift, sweep control is performed by increasing the hydraulic pressure of the engaging element B1 at a second slope. When the number of input revolution is only continued more than a designated time in a synchronous state, speed change control is complete by fastening the engaging element B1. When the number of input revolution is increased by increase of engine torque after synchronous decision, the sweep control is continued, and drawing shock is prevented accordingly. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a shift control method for an automatic transmission, and more particularly to a method for controlling an engagement element during an upshift.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-39346 [Patent Document 2] Japanese Patent Application Laid-Open No. 5-1582 Generally, an automatic transmission automatically shifts from a shift map according to operating conditions such as a vehicle speed and a throttle opening. The gear is determined, and the shift is performed by supplying or discharging the hydraulic pressure to or from the engagement element. In such an automatic transmission, for example, if the vehicle is running while depressing an accelerator pedal, the operating point determined by the vehicle speed and the throttle opening at that time crosses the upshift line of the shift map to shift to a higher gear. That is, a so-called power-on upshift is performed. If the accelerator pedal is suddenly returned while the vehicle is running while depressing the accelerator pedal, a so-called power-off upshift is performed in which the operating point crosses the upshift line of the shift map to shift to a higher gear. Here, a power-on upshift refers to performing an upshift while the throttle opening (accelerator opening) is opened to some extent, and a power-off upshift refers to performing an upshift when the throttle opening is almost fully closed. To do the shift.
[0003]
By the way, when performing an upshift, control is performed to engage the engagement elements with a predetermined time gradient so that the turbine speed gradually decreases. Generally, since the response of the hydraulic pressure is delayed with respect to the movement of the command current of the solenoid valve controlling the hydraulic pressure of the engagement element, the synchronization determination for determining the engagement timing of the engagement element in consideration of the delay in advance is performed at a high speed. It must be performed before the turbine speed drops to the stage turbine speed. In other words, it is customary to make a synchronization determination at the point in time when the turbine speed has decreased to a speed higher than the turbine speed of the high-speed stage by a predetermined value. After the synchronization determination, the sweep control for increasing the hydraulic pressure of the engagement element at a constant gradient is continued for a predetermined time, and thereafter, the engagement element is fully engaged to terminate the speed change control.
[0004]
[Problems to be solved by the invention]
In order to save fuel and prevent overheating of the catalyst, fuel cut control for shutting off fuel supply to the engine when the throttle is fully closed is widely performed. However, when a phenomenon such as fuel cut return that increases engine torque occurs during the sweep control after the synchronization determination of the power-off upshift, there is a problem that a turbine rotation pull-in shock occurs.
FIG. 7 shows an example of such a phenomenon, and shows the engine torque, the turbine speed, the command current and the oil pressure of the engagement element B1, and the time change of the vehicle body G during a power-off upshift.
When a power-off upshift speed change command is issued, the initial pressure is supplied to the engagement element B1 for a predetermined time after the play is reduced. This initial pressure is for causing the oil pressure to follow the current. Thereafter, the command current is increased so that the change rate of the turbine speed becomes the target value, and the hydraulic pressure of the engagement element B1 is increased. Eventually, when it is detected (synchronization determination) that the turbine speed has decreased to a value higher than the turbine speed of the high speed stage by a predetermined value (synchronization determination), the command current is increased at a predetermined gradient, and sweep control is performed for a certain time. Thereafter, the hydraulic pressure of the engagement element B1 is raised to the engagement state, and the shift is completed.
However, if the engine torque increases due to the return of the fuel cut during the sweep control, the slippage occurs in the engagement element B1, and the turbine speed increases again. However, since the synchronization determination has already been completed, the engagement elements are completely engaged after the sweep control for a certain period of time, and a pull-in shock of turbine rotation occurs.
[0005]
As a method for solving this problem, it is conceivable to lengthen the period of the sweep control. That is, it is a method of waiting for time until the turbine speed is stabilized. However, this method has a problem that the sweep control period is always long regardless of whether or not the engine torque increases during the sweep control, so that the shift time is also long.
[0006]
Patent Document 1 proposes a shift control method for preventing an engagement shock due to an undershoot during a power-off upshift. In other words, if it is determined that the input speed of the automatic transmission has dropped below a predetermined value higher than the input speed of the high speed stage by a predetermined value, the input speed is not changed until a predetermined time elapses from the synchronization determination. Is determined to be lower than the input speed of the high speed stage. If the input speed after the lapse of a predetermined time is equal to or higher than the input speed of the high speed stage, the engaging oil pressure of the engaging element is increased to increase the engaging element. When the input rotation speed becomes lower than the input rotation speed of the high-speed stage, the engagement hydraulic pressure of the engagement element is increased at a gentler gradient than the rising gradient at the time of engagement.
[0007]
Patent Document 2 proposes a control device for an engine and an automatic transmission in which the output of the engine is reduced at the time of upshifting. That is, when the rate of change of the turbine rotation speed becomes negative, the shift end turbine rotation speed is predicted, and the end rotation speed of the fuel cut control is calculated based on this. Therefore, the end rotation speed of the fuel cut control is calculated at the stage immediately before or immediately after the turbine rotation speed largely changes, and the end rotation speed of the fuel cut control is accurately determined regardless of the state of the subsequent change in the turbine rotation speed. This makes it possible to predict and accurately terminate the fuel cut control.
[0008]
However, the methods described in Patent Literatures 1 and 2 cannot effectively prevent a turbine rotation pull-in shock due to an increase in engine torque after the above-described synchronization determination.
The above phenomenon occurs not only at the time of the off-upshift but also at the time of the on-upshift. For example, when an upshift is performed at a throttle opening of 20% and the throttle opening is rapidly increased to 80% after the synchronization determination, a turbine rotation pulling shock due to an increase in engine torque may occur. .
[0009]
Accordingly, an object of the present invention is to provide a shift control method for an automatic transmission that can effectively prevent a pull-in shock of input rotation due to an increase in engine torque after a synchronization determination during an upshift.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is directed to a shift control method for an automatic transmission that performs an upshift from a low gear to a high gear by supplying hydraulic pressure to a predetermined engagement element. Increasing the hydraulic pressure of the combined element at a first gradient to reduce the input speed of the automatic transmission to the input speed of the high speed stage, and wherein the input speed is within a range near the input speed of the high speed stage. Detecting that the input rotation speed has fallen to within the vicinity range; and increasing the hydraulic pressure of the engagement element at a second gradient when the input rotation speed has fallen within the vicinity range. Detecting that the state in which the input rotation speed is within the vicinity range continues for a predetermined time or more, and closing the engagement element and terminating the shift control when the state in which the input rotation speed is within the vicinity range continues for a predetermined time or more. And an automatic transmission having To provide a gear shift control method.
[0011]
When the upshift is started, the hydraulic pressure of the engaging element is increased at the first gradient, and the input speed of the automatic transmission is reduced to the input speed of the high speed stage. For example, feedback control may be performed using a change rate (decrease rate) of the input rotation speed as a target value. Eventually, when it is detected (synchronous determination) that the input rotational speed has fallen into a range near the input rotational speed of the high-speed stage, the hydraulic pressure of the engagement element is increased at the second gradient, and sweep control is performed. If the engine torque increases during the sweep control due to fuel cut return or the like, slippage occurs in the engagement element, and the input rotation speed increases again. In the present invention, only when the state where the input rotational speed is within the range close to the high-speed input rotational speed continues for a predetermined time or more, the engagement element is engaged and the shift control is terminated. That is, if the synchronization state is deviated even once during the sweep control, the timer is reset and the synchronization determination is repeated. Therefore, during the sweep control, when the engine torque increases due to the fuel cut return or the like and the input rotation speed increases again, the sweep control can be continued to prevent the input shock from being pulled in.
Further, when the engine torque does not increase during the sweep control, the synchronization state continues for a certain period of time or more, so that the sweep control is completed in a short time and there is no problem that the shift time becomes longer as in the related art. . That is, by extending the sweep control period only when there is an increase in the engine torque during the sweep control, both the reduction of the shock and the reduction of the shift time can be achieved.
[0012]
The control method of the present invention can be applied to any of a power-on upshift and a power-off upshift. However, when applied to a power-off upshift, the effect is great.
In the power-on state, the driver is willing to accelerate, so he can endure even a slight shock.However, if the input rotation is retracted in the power-off state, the driver may experience unexpected shocks. This is because it causes discomfort and discomfort. In the power-off state, the driver wants to maintain the current state or decelerate, whereas when the power-off upshift is performed, a feeling of popping out of the vehicle occurs. In the present invention, such a feeling of popping out is eliminated or suppressed. can do.
Note that the input rotation pull-in shock occurs during the power-off upshift, in addition to the above-described fuel cut return, when the air conditioner is turned off, and when the accelerator pedal is depressed.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a vehicle system equipped with an automatic transmission according to the present invention.
The output of the engine 1 is transmitted to a transmission mechanism 4 via a torque converter 3 of the automatic transmission 2, and the transmission mechanism 4 is connected to wheels (not shown) via an output shaft 5. The automatic transmission 2 includes an oil pump 6 driven by the engine 1 via a torque converter 3, and the discharge pressure of the oil pump 6 is sent to a hydraulic control device 7. The hydraulic control device 7 includes first to third solenoid valves 21 to 23 for speed change control. By controlling the solenoid valves 21 to 23 with the AT controller 20, various types of gears built in the speed change mechanism 4 are provided. The hydraulic pressure of the combined element is controlled in accordance with the traveling state, and a plurality of shift speeds described later are switched. Here, signals are input to the AT controller 20 from an engine speed sensor 24, a throttle opening sensor 25, a turbine speed (input speed) sensor 26, a vehicle speed sensor 27, a shift position sensor 28, and the like. May be input.
In the above-described embodiment, the three solenoid valves 21 to 23 for shifting control are provided in the hydraulic control device 7. However, solenoid valves for lock-up clutch control, line pressure control, and the like may be provided. .
[0014]
FIG. 2 shows an example of the transmission mechanism 4.
The transmission mechanism 4 includes an input shaft 10 to which engine power is transmitted via a torque converter 3, three clutches C1 to C3 and two brakes B1 and B2, which are friction engagement elements, a one-way clutch F, a Ravigneaux type planet. A gear device 11, a differential device 14, and the like are provided.
The forward sun gear 11a of the planetary gear set 11 and the input shaft 10 are connected via a C1 clutch, and the rear sun gear 11b and the input shaft 10 are connected via a C2 clutch. The carrier 11c is connected to a center shaft 15, and the center shaft 15 is connected to the input shaft 10 via a C3 clutch. The carrier 11c is connected to the transmission case 16 via a B2 brake and a one-way clutch F that allows only the forward rotation (engine rotation direction) of the carrier 11c. The carrier 11c supports two types of pinion gears 11d and 11e, the forward sun gear 11a meshes with a long pinion 11d having a long shaft length, and the rear sun gear 11b meshes with a long pinion 11d via a short pinion 11e having a short shaft length. . The ring gear 11f that meshes with only the long pinion 11d is connected to the output gear 12. The output gear 12 is connected to a differential 14 via an intermediate shaft 13.
[0015]
The transmission mechanism 4 realizes four forward speeds and one reverse speed as shown in FIG. 3 by operating the clutches C1, C2, C3, the brakes B1, B2, and the one-way clutch F. In FIG. 3, ● indicates the operating state of the hydraulic pressure. The B2 brake is engaged at the time of retreat and at the first speed of the L range. FIG. 3 also shows the operating states of the first to third solenoid valves (SOL1 to SOL3) 21 to 23. ○ indicates an energized state, and X indicates a non-energized state. This operation table shows the operation in the steady state.
[0016]
The first solenoid valve 21 is for B1 brake control, the second solenoid valve 22 is for C2 clutch control, and the third solenoid valve 23 is for both C3 clutch control and B2 brake control. The reason that the third solenoid valve 23 serves both for controlling the C3 clutch and for controlling the B2 brake is that the B2 brake does not operate in the D range and is used only for the engine brake control in the L range and the transient control in the R range. This is because they do not interfere with the C3 clutch operated in the D range.
Since the first to third solenoid valves 21 to 23 need to perform delicate hydraulic control, a duty solenoid valve or a linear solenoid valve is used. In this embodiment, the first solenoid valve 21 is a normally closed type, and the second and third solenoid valves 22 and 23 are a normally open type.
[0017]
The memory of the AT controller 20 stores a power-on and power-off determination value map during an upshift as shown in FIG. 4 in addition to the shift map. As is apparent from FIG. 4, when the engine speed is the same, the power-on state is determined when the throttle opening is large, and the power-off state is determined when the throttle opening is small. The off-up region is set to expand in a high engine speed region.
[0018]
FIG. 5 shows the engine torque, the turbine speed, the command current and the hydraulic pressure of the engagement element B1, and the time change of the vehicle body G during the power-off upshift from the first speed to the second speed in the automatic transmission 2. In particular, it shows a change when a phenomenon that the engine torque increases, such as fuel cut return during the sweep control, occurs.
When a power-off upshift speed change command is issued, backlash is performed for a predetermined time, and the initial pressure is supplied to the engagement element B1 for a predetermined time. The supply period of the initial pressure is a period for causing the hydraulic pressure of the engagement element B1 to follow the command current. Thereafter, when the hydraulic pressure of the engagement element B1 is feedback-controlled (gradient A) so that the turbine rotation speed becomes the target change rate, the turbine rotation speed starts to decrease. Eventually, when it is detected (synchronous determination) that the turbine speed has dropped to within the vicinity of the second speed turbine speed, sweep control of the hydraulic pressure of the engagement element B1 at a predetermined gradient B is started. In addition, the vicinity value in the synchronization determination may be, for example, about the turbine speed at the second speed ± 30 rpm.
If the engine torque increases during the sweep control due to a return from the fuel cut or the like, the turbine speed increases again, and the loss of synchronization is detected. In the present invention, the sweep control is not terminated unless the synchronization state continues for a certain period of time Δt. Therefore, if there is a loss of synchronization, the timer is reset. When the synchronization state continues for the predetermined time Δt or more, the command current is increased to the maximum value for the first time, the maximum hydraulic pressure is supplied to the engagement element B1, and the shift control ends. At the point of time when the engagement element B1 is completely engaged, the turbine speed is maintained in a synchronized state, so that a retraction shock does not occur and the shift can be smoothly finished. The fixed time Δt may be a period similar to the conventional sweep control period, and may be, for example, about 300 ms.
If the engine torque does not increase during the sweep control, the turbine speed does not increase again, and the sweep control ends in the fixed time Δt, so that the shift time does not become longer than in the conventional case. .
[0019]
FIG. 6 shows an example of a control method during a power-off upshift according to the present invention.
When the control is started, it is determined whether an upshift from the first speed to the second speed is possible (step S1), and if possible, it is determined whether the power is off (step S2). If it is determined that the vehicle is in the power-off area, a shift command from the first speed to the second speed is issued (step S3), the loosening of the engagement element B1 (step S4), and the initial pressure supply (step S5). ). Next, feedback control (gradient A) of the command current is started so that the turbine speed becomes the target rate of change (step S6), the oil pressure of the engagement element B1 is increased, and the turbine speed at the second speed is increased. A determination (synchronization determination) is made as to whether or not the number has fallen into the vicinity of the number (step S7). If it is determined in the synchronization determination that the synchronization state has not yet been reached, the feedback control is continued. If it is determined in the synchronization determination in step S7 that the state is the synchronization state, sweep control is subsequently performed (step S8). This sweep control is a control for increasing the command current at a predetermined gradient B and increasing the oil pressure of the engagement element B1. Then, the synchronization determination is performed again while performing the sweep control (step S9). When it is determined that the synchronization state is established, the elapsed time of the synchronization state is measured, and the elapsed time becomes equal to or longer than the fixed time Δt. Steps S8 and S9 are repeated until (Step S10). If the synchronization state is deviated even once during the fixed time Δt, the elapsed time is reset to 0 (step S11), and the synchronization determination is repeated while performing the sweep control.
Eventually, when the synchronization state continues for a predetermined time Δt or more, the sweep control is terminated and a termination process is performed (step S12), the engagement element B1 is completely engaged, and the shift is terminated.
[0020]
5 and 6, the power-off upshift from the first speed to the second speed has been described, but the same applies to other upshifts (1 → 3, 2 → 3, 3 → 4, 2 → 4). Further, the present invention can be applied not only to a power-off upshift but also to a power-on upshift. However, since the power-on upshift is performed in a state where the throttle opening is opened, the pull-in shock hardly occurs when the fuel cut is restored or the air conditioner is turned off. Rather, the present invention is effective against an engagement shock when the throttle opening is greatly opened while the power-on upshift is being performed while the throttle opening is relatively low.
[0021]
【The invention's effect】
As apparent from the above description, according to the present invention, after the synchronization determination at the time of the upshift, the sweep control is continued until the synchronization state continues for a certain period of time or more. When the input rotation speed increases again, the engagement element is not completely fastened until the input rotation speed is stabilized, and the pull-in shock of the input rotation can be reliably prevented.
Further, when the engine torque does not increase during the sweep control, the sweep control can be completed in a short time as in the related art, and there is no problem that the shift time becomes long. That is, by extending the sweep control period only when there is an increase in the engine torque during the sweep control, both the reduction of the shock and the reduction of the shift time can be achieved.
[Brief description of the drawings]
FIG. 1 is a system diagram in which an automatic transmission for a vehicle according to the present invention is mounted.
FIG. 2 is a skeleton diagram of a transmission mechanism of the automatic transmission of FIG.
FIG. 3 is an operation table of each friction engagement element and a solenoid valve of the transmission mechanism shown in FIG. 2;
FIG. 4 is a diagram showing a power on / off determination value during an upshift.
FIG. 5 is a time change diagram of an engine torque, a turbine rotation speed, a command current and an oil pressure of an engagement element B1, and a vehicle body G at the time of power-off according to the present invention.
FIG. 6 is a flowchart illustrating an example of a control method during a power-off upshift according to the present invention.
FIG. 7 is a time change diagram of the engine torque, the turbine speed, the command current and the oil pressure of the engagement element B1, and the vehicle body G at the time of the conventional power-off upshift.
[Explanation of symbols]
B1 engagement element 20 AT controller 21 B1 brake control solenoid valve

Claims (2)

In a shift control method for an automatic transmission that performs an upshift from a low gear to a high gear by supplying hydraulic pressure to a predetermined engagement element,
Increasing the hydraulic pressure of the engagement element at a first gradient to reduce the input speed of the automatic transmission to the input speed of the high speed stage;
A step of detecting that the input rotation speed has dropped to a range near the input rotation speed of the high-speed stage,
A step of increasing the hydraulic pressure of the engagement element at a second gradient when the input rotation speed falls within the vicinity range;
A step of detecting that the state in which the input rotation speed is within the vicinity range has continued for a predetermined time or more,
A step of engaging the engagement element and ending the shift control when the state in which the input rotational speed is within the vicinity range continues for a predetermined time or more. The shift control method for an automatic transmission according to claim 1, wherein the upshift is a power-off upshift.

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