JP4716743B2 - Shift control method and apparatus for automatic transmission - Google Patents

Description

The present invention relates to a shift control method and apparatus for an automatic transmission, and more particularly to shift control during power-off.

In general, an automatic transmission performs a shift by automatically determining a gear position from a shift diagram according to driving conditions such as a vehicle speed and a throttle opening. In such an automatic transmission, when the accelerator pedal is suddenly loosened while the accelerator pedal is being depressed, the throttle opening is almost fully closed at a high vehicle speed. The operating point exceeds the shift point and the gear is shifted to the high speed side. This is called an off-up shift.

In such an off-up shift, since the throttle is almost closed, it is in a power-off state, and the turbine rotational speed naturally falls. Generally, since the response of the hydraulic pressure is delayed with respect to the movement of the input current value of the solenoid valve that controls the hydraulic pressure of the friction engagement element, the synchronization determination for determining the engagement timing of the friction engagement element in advance in consideration of the delay It is necessary to perform the operation before the turbine speed drops to the high-speed turbine speed. In other words, the synchronization determination is usually performed at a rotational speed at which the turbine input rotational speed is higher by a predetermined value than the high-speed turbine rotational speed.

However, since the descending speed of the turbine rotational speed is not constant, it cannot be predicted whether or not the frictional engagement element on the engagement side is in a state immediately before the engagement at the time of synchronization determination. For example, when the descending speed of the turbine rotational speed is large and the friction engagement element does not reach the state immediately before the engagement at the time of synchronization determination, the turbine rotational speed falls below the turbine rotational speed of the high speed stage. This is called undershoot. If the hydraulic pressure is suddenly raised to fully engage the friction engagement elements after undershoot, a turbine rotation lifting shock is generated.

In order to solve such a problem caused by undershoot, in Patent Document 1, when undershoot occurs at the time of off-up, sweep control is performed so that the rising gradient of the hydraulic pressure of the friction engagement element becomes gentle, and the shock of lifting turbine rotation is shocked. A method of improving is disclosed. Further, in order to improve undershoot due to individual variations of the automatic transmission, a method of learning and controlling the initial hydraulic pressure of the friction engagement element is disclosed so that the amount of undershoot at the time of off-up is within a set range.

In the learning control method described above, whether to perform learning is determined based on whether it is off-up. However, even if it is off-up, in a slight reverse load state, the descending speed of the turbine rotation is gradual, and the undershoot amount is almost zero. Here, the original means the case where the individual variation of the automatic transmission has already been corrected. However, when the reverse load tendency becomes strong at the off-up, the turbine rotation descends faster, so that undershoot is likely to occur. For this reason, if the initial hydraulic pressure is learned and corrected with the off-up region including the slight reverse load state as the same learning region, there is a possibility of unstable shift control such as a shock occurring in the subsequent off-up shift. .
JP 2002-39346 A

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a shift control method and apparatus for an automatic transmission that can appropriately perform learning control of undershoot during off-up shift and can perform stable shift control.

In order to achieve the above object, an invention according to claim 1 is an automatic transmission that constitutes a predetermined shift stage by engaging or releasing a friction engagement element, and is based on engine speed and load information. set the power-on up-area and power-off up region by Dzu rather threshold while implementing shift control in accordance with each region is controlled to an appropriate amount by the learning control undershoot of an input rotation at power-off upshift In the control method, the step of determining whether the engine speed and the load information are on the power-off-up side from the threshold value, and when the engine speed and the load information are on the power-off-up side from the threshold value, Determining whether or not the learning execution determination value provided on the power-off-up side of the threshold is further on the power-off-up side, and When the engine speed and the load information are further on the power-off-up side than the learning execution determination value, the step of executing the learning control and the engine speed and the load information are determined by the threshold value and the learning execution determination value. And a step of prohibiting the learning control when in the intermediate region.

Invention, an automatic transmission that constitutes a predetermined gear stage by friction the coupling elements to engage or release, a power-on up by the threshold rather based on the load information and engine speed according to claim 2 In the shift control device that sets a region and a power-off region, performs shift control according to each region, and controls an undershoot of input rotation at the time of power-off to an appropriate amount by learning control. Also provided is a shift control device in which a learning execution determination value is provided on the power-off side, and a region between the threshold value and the learning execution determination value is set as a prohibited region of the learning control.

The undershoot amount of the input rotation can be varied by the initial hydraulic pressure of the friction engagement element, that is, the hydraulic pressure for bringing the friction engagement element piston into contact with the first clutch plate. Conventionally, since undershoot learning control is always performed at the time of off-up, the initial hydraulic pressure is unnecessarily corrected for learning, and a shift shock may occur at the subsequent off-up.
If there is a slight reverse load state even at the time of off-up, the difference between the engine torque and the torque input from the wheel side is small, so the rate of decrease in turbine speed is low. That is, since the turbine rotation is slowly lowered, almost no undershoot occurs when the rotational speed of the high speed stage is reached. Whether or not this is the case can be estimated from the engine speed and load information (for example, accelerator opening). Therefore, in claim 1, the learning execution determination value is provided on the off-up side of the on-up / off-up threshold, and the engine speed and the load information at the time of off-up are in a region between the threshold and the learning execution determination value. It is determined whether or not there is an off-up side with respect to the learning execution determination value, thereby determining whether or not learning control is to be performed.
That is, in a slight reverse load state (a state in which the undershoot is expected to be small) even in the off-up state, the learning control is prohibited, thereby preventing the initial hydraulic pressure from being unnecessarily learned and corrected. In a large reverse load state (a state in which undershoot is likely to occur), the undershoot is adjusted to an appropriate value by performing learning control.

In the learning control, the undershoot amount may be detected as in the conventional case, and the control amount may be updated according to the magnitude. The undershoot amount may be determined by the maximum amount of descent when the input rotational speed (for example, the turbine rotational speed) becomes lower than the high speed stage input rotational speed, or the input rotational speed is lower than the high speed stage input rotational speed. You may judge with the time integral value of the amount of descent until becoming a rise after becoming.
Although the power-on-up / power-off-up thresholds are set based on the engine speed and the load information, the input speed (turbine speed) may be used as information substituting for the engine speed. Further, as the load information, the accelerator opening, the intake pipe negative pressure, and the like can be used.
Further, in order to perform learning control of undershoot, the initial hydraulic pressure of the friction engagement element is used as a control amount. However, an input current of an electromagnetic valve that controls the friction engagement element corresponding to the initial hydraulic pressure may be used. A duty ratio may be used.

As described above, according to the first aspect, since the learning control prohibition area is provided on the power-off-up side from the power-on-up / power-off-up thresholds, the learning prohibition area can be easily determined from the engine speed and the load information. You can determine whether or not. For this reason, even under off-up, if a slight reverse load state is present, the undershoot is inherently small, so that correction by learning is prohibited, and unnecessary fluctuations in the control amount can be suppressed. As a result, stable shift control with less shock is possible.

Embodiments of the present invention will be described below with reference to examples.

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 the transmission mechanism 4 via the torque converter 3 of the automatic transmission 2, and the transmission mechanism 4 is connected to wheels (not shown) via the output shaft 5. The automatic transmission 2 includes an oil pump 6 driven by the engine 1 via the torque converter 3, and the discharge pressure of the oil pump 6 is sent to the 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 frictions built in the speed change mechanism 4 are provided. The hydraulic pressure of the engagement element is controlled according to the traveling state. Here, signals such as engine speed, throttle opening, turbine speed, vehicle speed, and shift position are input to the AT controller 20, but other signals may also be input.
In addition to the three solenoid valves 21 to 23 for speed change control, the hydraulic control device 7 may be provided with solenoid valves for lockup clutch control, line pressure control, and the like.

FIG. 2 shows an example of the speed change mechanism 4.
The speed change 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 mechanism 11 and a differential device 14 are provided.

The forward sun gear 11a and the input shaft 10 of the planetary gear mechanism 11 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 the 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 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 axial length, and the rear sun gear 11b meshes with the long pinion 11d via a short pinion 11e having a short axial length. . A ring gear 11f that meshes only with the long pinion 11d is coupled to the output gear 12. The output gear 12 is connected to the differential device 14 via the intermediate shaft 13.

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, ● represents the action state of hydraulic pressure. The B2 brake is engaged at the time of reverse and the first speed in the L range. FIG. 3 also shows 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 a steady state.

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 why the third solenoid valve 23 serves both for C3 clutch control and B2 brake control is that the B2 brake does not operate in the D range, but is used only in the engine brake control in the L range and the transient control in the R range. This is because it does 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 pressure control, duty solenoid valves or linear solenoid valves are used. In this embodiment, the first solenoid valve 21 is normally closed and the second and third solenoid valves 22 and 23 are normally open.

In addition to the shift diagram as shown in FIG. 4, the AT controller 20 also stores a power on / off determination map at the time of upshift shown in FIG.
The shift diagram shown in FIG. 4 is a shift diagram of the D range, where the solid line indicates the upshift line and the broken line indicates the downshift line.
The determination map shown in FIG. 5 is set by the engine speed and the throttle opening (accelerator opening), and the upper side of the threshold A (high accelerator opening side) is the power-on-up region and is lower than the threshold A. The side (low accelerator opening side) is the power-off area. Another threshold B is set below the threshold A, and this threshold B is a learning execution determination value. A region between the threshold A and the learning execution determination value B is an off-up but undershoot learning control prohibition region, and an area below the learning execution determination value B is off-up and undershoot learning control is performed. It is an area.
4 and 5 show a typical example, and the present invention is not limited to this figure.

The off-up shift method according to the present invention is the same as the method described in Patent Document 1 except for learning control. FIG. 6 shows an example of the off-up shift control from the first speed to the second speed. Is omitted.
Here, the turbine rotation speed, the input current of the B1 brake control solenoid valve 21, and the B1 brake pressure over time when undershoot occurs are shown.
In FIG. 6, the initial hydraulic pressure Pi of the B1 brake or the input current Ia of the solenoid valve 21 for outputting the initial hydraulic pressure is corrected by undershoot learning control described later.

7 and 8 show an example of undershoot learning control in the present invention. FIG. 7 is a flowchart for determining whether or not the learning control can be performed, and FIG. 8 is a flowchart showing an actual learning control method.
In FIG. 7, when starting, it is first determined whether or not an off-up shift command is output (step S1). This determination is made when the vehicle speed and the throttle opening exceed the upshift line of the shift diagram shown in FIG. 4, and the engine speed and the throttle opening (accelerator opening) are based on the threshold A of the determination map shown in FIG. Judge by being on the lower side.
When an off-up shift command is output, a learning execution determination value (accelerator opening) with respect to the engine speed is retrieved from the determination map shown in FIG. 5 (step S2), and the accelerator opening at the time of the shift command and learning execution determination are determined. The value is compared (step S3). If the accelerator opening is equal to or greater than the learning execution determination value, it is in the prohibited region of learning control in FIG. 5, so the learning execution flag is set to OFF (step S4), and if the accelerator opening is less than the learning execution determination value, 5, the learning execution flag is set to ON (step S5), and the process ends.
That is, even if it is off-up, if it is in a slight reverse load state, it is an area where undershoot hardly occurs. Therefore, learning is prohibited so that unnecessary learning correction is not performed.

In FIG. 8, it is first determined whether or not the learning execution flag is ON (step S6). If the learning execution flag is OFF, the following learning control is not performed. That is, the learning value is not urged to be updated in the region below the threshold B, and the learning result in the learning region below the threshold B is not reflected in the learning prohibited region. If the learning execution flag is ON, it is next determined whether an undershoot has occurred (step S7). For example, it is determined whether the maximum drop amount ΔT of the turbine rotational speed is 0 as the undershoot amount.
When the undershoot does not occur, the learning update amount is set to a predetermined value (negative value) (step S8), and a value obtained by adding the learning update amount to the previous value is set as a learning value (step S9). Specifically, a value obtained by subtracting a constant value from the previously output initial hydraulic pressure is used as the initial hydraulic pressure. Therefore, when no undershoot occurs, it is determined that the initial hydraulic pressure is too high, and the initial hydraulic pressure is corrected to be gradually lower.
On the other hand, if undershoot has occurred, the learning update amount is calculated by the following equation (step S10).
Learning update amount = gain x (undershoot amount-undershoot target value)
When the undershoot amount is larger than the target value, the learning update amount becomes a positive value, so the initial hydraulic pressure that is the learned value is corrected to a high value in step S9. On the other hand, when the undershoot amount is smaller than the target value, the learning update amount becomes a negative value, so the initial hydraulic pressure that is the learned value is corrected to a low value in step S9. Subsequent off-up control is performed using the corrected initial oil pressure.
By experiencing learning as described above, after experiencing several off-ups, the initial hydraulic pressure is updated to the optimum value, and the undershoot amount is controlled within a predetermined range. As a result, a stable shift without shock can be realized.

Steps S7 to S10 in FIG. 8 merely show an example of the learning correction method, and the method for suppressing undershoot is not limited to steps S7 to S10. For example, the method described in FIG. 9 of Patent Document 1 may be used. A dead zone can also be provided according to the amount of undershoot generated.
In the above embodiment, the off-up shift from the 1st speed to the 2nd speed, that is, the hydraulic control of the B1 brake has been described. The same applies to hydraulic control of elements.
The automatic transmission of the present invention is not limited to an automatic transmission having three clutches C1 to C3 and two brakes B1 and B2 as shown in FIG.

It is a system diagram carrying the automatic transmission for vehicles in the present invention. FIG. 2 is a skeleton diagram of a transmission mechanism of the automatic transmission of FIG. 1. 3 is an operation table of each friction engagement element and solenoid valve of the speed change mechanism shown in FIG. 2. It is an example of the shift diagram of the automatic transmission of FIG. It is a power on / off determination map at the time of upshift. It is a figure which shows an example of the off-up shift control from 1st speed to 2nd speed. It is a flowchart figure of an example which determines the implementation propriety of undershoot learning control. It is a flowchart figure which shows an example of undershoot learning control.

Explanation of symbols

B1 Brake (Friction engagement element)
20 AT controller 21 B1 solenoid valve for brake control

Claims (2)

An automatic transmission that constitutes a predetermined shift stage by engaging or releasing a friction engagement element,
With setting the power-on up-area and power-off up area by the threshold engine speed based rather on the load information, to implement the shifting control according to each region, the undershoot of the input rotation at power-off up In a shift control method for controlling to an appropriate amount by learning control,
Determining whether the engine speed and the load information are on the power-off side of the threshold value;
Determining whether the engine speed and the load information are on the power-off-up side from the threshold value, and determining whether or not the engine execution determination value provided on the power-off-up side is further on the power-off-up side than the threshold value; ,
Performing the learning control when the engine speed and load information are further on the power-off side than the learning execution determination value;
And a step of prohibiting the learning control when the engine speed and the load information are in a region between the threshold value and the learning execution determination value. An automatic transmission that constitutes a predetermined shift stage by engaging or releasing a friction engagement element,
With setting the power-on up-area and power-off up area by the threshold engine speed based rather on the load information, to implement the shifting control according to each region, the undershoot of the input rotation at power-off up In a shift control device that controls to an appropriate amount by learning control,
A learning execution determination value is set on the power-off-up side from the threshold value,
A speed change control apparatus characterized in that a region between the threshold value and the learning execution determination value is set as a prohibited region for the learning control.

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