JP3492295B2 - Shift control method for automatic transmission - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control method for an automatic transmission, and more particularly to a friction engagement element control method during an off-up shift.

[0002]

2. Description of the Related Art Generally, an automatic transmission automatically shifts gears by determining a shift stage from a shift diagram according to operating conditions such as vehicle speed and throttle opening. In such an automatic transmission, if the accelerator pedal is suddenly loosened while the vehicle is traveling while depressing the accelerator pedal, the throttle opening becomes almost fully closed at a high vehicle speed. The operating point exceeds the gear shift point and the gear is shifted to the higher gear. This is called an off-up shift.

In such an off-up shift, the throttle is closed, so that the power is off and the turbine speed naturally drops. 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 frictional engagement element, the synchronization determination that determines the engagement timing of the frictional engagement element in consideration of the delay in advance Must be performed before the turbine speed drops to the high speed stage. That is, it is customary to perform the synchronization determination at a turbine input rotational speed higher than the turbine rotational speed of the high speed stage by a predetermined value.

[0004]

However, since the descending speed of the turbine speed is not constant, it is not possible to predict whether or not the frictional engagement element on the engagement side is in a state immediately before engagement at the time of synchronization determination. FIG. 1 shows an off-up shift (for example, 1
Fig. 7 shows changes with time of the turbine speed, the input current of the solenoid valve, and the engagement hydraulic pressure of the friction engagement element at the time of (speed → second speed). The solid line in FIG. 1 is a case where the descending speed of the turbine speed and the engagement timing of the friction engaging element are well matched, and the friction engaging element is activated when the turbine speed drops to the turbine speed of the high speed stage. If it is completely engaged, there is no shock and the shift can be smoothly completed. The dashed line in FIG. 1 indicates that the turbine rotation speed drops faster than the turbine rotation speed of the high-speed stage because the frictional engagement element does not reach the state immediately before engagement when the synchronization is determined. (Hereinafter referred to as undershoot).
In this case, if the hydraulic pressure is suddenly raised in order to completely engage the frictional engagement element after undershooting, a lifting shock of turbine rotation occurs.

Japanese Unexamined Patent Publication No. 10-181386 discloses a system in which engine torque is feedback-controlled so that the turbine speed becomes a target speed during off-up gear shifting. In this case, the turbine rotation undershoot itself can be prevented, but integrated control of the engine and automatic transmission is required, and the control becomes complicated, and
The drawback is that the engines used are also limited.

Therefore, an object of the present invention is to provide a shift control method for an automatic transmission which can prevent an engagement shock due to an undershoot during an off-up gear shift by controlling an engagement hydraulic pressure of a friction engagement element. It is in.

[0007]

In order to achieve the above-mentioned object, the invention according to claim 1 is to apply an engagement hydraulic pressure to a predetermined friction engagement element in a state where the throttle opening is fully closed or near the fully closed position. Is a shift control method for an automatic transmission that upshifts from a low-speed stage to a high-speed stage by reducing the input rotational speed of the automatic transmission to a rotational speed that is higher than the input rotational speed of the high-speed gear by a predetermined value. A step of determining that it has descended,
When the input rotational speed is determined to have fallen below a high rotational speed by a predetermined value than the input rotational speed of the high gear, the input input speed during the period until a predetermined time from the determination of the high-speed stage During the process of detecting whether or not the rotational speed has become lower than the rotational speed, and during the period from the determination until a predetermined time has elapsed , when the input rotational speed is equal to or higher than the input rotational speed of the high speed stage, the engagement hydraulic pressure of the friction engagement element is a step of fastening the friction engagement element is raised to an upper <br/> fill force rotational speed until the expiration of a predetermined time from the determination is lower than the input rotation speed of the high gear
Can provide a step of the engagement oil pressure of the frictional engagement element is increased in gradual Do gradient from rising gradient during the fastening, a shift control method for an automatic transmission having a.

First, the synchronization determination is performed at a rotational speed at which the input rotational speed is higher than the rotational speed at the high speed by a predetermined value. If it is determined by the synchronization determination that the input rotation speed has dropped below the rotation speed that is higher than the input rotation speed of the high-speed stage by a predetermined value, then an undershoot occurs until the predetermined time elapses after the synchronization determination. It is detected whether or not. At a predetermined time from the synchronization judgment
During the period until the time elapses , when the input speed is equal to or higher than the input speed of the high speed stage, it is determined that the undershoot has not occurred, and the engagement hydraulic pressure of the friction engagement element is increased steeply as usual. The friction engagement element may be fastened. In this case, since the input rotation speed substantially matches the input rotation speed of the high speed stage, no shock occurs. On the other hand, synchronization judgment
If the input rotation speed becomes lower than the input rotation speed of the high speed stage (during undershoot) from the time until the predetermined time elapses (undershoot), if the hydraulic pressure of the friction engagement element is rapidly increased to the engagement state, With shock. Therefore, at the time of undershoot, the engagement hydraulic pressure of the friction engagement element is increased at a gentler gradient than the upward gradient at the time of engagement. That is, sweep control is performed. As a result, the lifting shock of the turbine rotation can be eliminated, and the shift can be smoothly completed. The input rotation speed in the present invention is the rotation speed of the input shaft of the automatic transmission, and in the case of the automatic transmission including the torque converter, corresponds to the turbine rotation speed.

According to a second aspect of the present invention, after the input rotation speed becomes lower than the input rotation speed of the high speed stage, the step of determining that the input rotation speed has changed from the decrease to the increase, and the input rotation speed from the decrease. After turning to increase, a step of determining whether or not the input speed of the high-speed stage is lower than the input speed of the high-speed stage by a predetermined value or more, It is desirable to further include the step of increasing the engagement hydraulic pressure of the friction engagement element to fasten the friction engagement element when the friction engagement element is raised. In other words, if the input rotation speed undershoots, it is determined that the input rotation speed has changed from falling to rising, and after that, it has risen to a rotation speed equal to or higher than a predetermined value lower than the input rotation speed of the high speed stage, that is, Perform resynchronization determination. By engaging the frictional engagement element by this resynchronization determination, the shift can be completed promptly and without shock.

When the input speed is lower than the input speed of the high speed stage, the maximum drop amount of the input speed or the input speed is lower than the input speed of the high speed stage. It is desirable to perform learning control of the initial hydraulic pressure of the friction engagement element so that the time integrated value of the amount of decrease until it rises is within the set range. The undershoot amount of the automatic transmission also varies depending on the individual variation. When the amount of undershoot is large, performing the control according to the present invention may delay the end of gear shift. The amount of undershoot can be changed by the initial oil pressure of the friction engagement element, that is, the oil pressure for bringing the piston of the friction engagement element into contact with the first clutch plate. It should be noted that the undershoot amount can be determined by the maximum drop amount of the input rotation speed or the time integrated value of the drop amount from the undershoot of the input rotation speed to the rise of the input rotation speed. Therefore, in claim 3, the initial hydraulic pressure is learned and controlled so that the amount of undershoot falls within the set range, thereby eliminating individual variations, realizing an automatic transmission with less engagement shock and less shift delay. is doing.

When the input rotation speed becomes lower than the input rotation speed of the high speed stage, the engagement hydraulic pressure of the frictional engagement element is continuously increased, and the input rotation speed is changed from decrease to increase. At this point, it is desirable to make the rising gradient of the engaging hydraulic pressure smaller than the rising gradient up to that point. In other words, after the input rotation speed becomes lower than the input rotation speed of the high speed stage, the input rotation speed is monitored, and after the time point when the input rotation speed changes from decrease to increase,
By further reducing the rising gradient of the engaging hydraulic pressure, it is possible to further reduce the shock of raising the turbine rotation speed.

[0012]

FIG. 2 shows an example of an automatic transmission according to the present invention. The automatic transmission 1 is provided with a speed change mechanism and a torque converter as described later, and the speed change mechanism is controlled to an arbitrary speed by a command from the AT controller 2. To the AT controller 2, the throttle opening sensor 3, the vehicle speed sensor 4, and the turbine rotation speed sensor 5 are input with the throttle opening, the vehicle speed, and the turbine rotation speed, respectively, and the shift position sensor 6 outputs "P" and "R". , "N", "D" and other shift position signals are input. The signal input to the AT controller 2 is not limited to the above signal. The AT controller 2 controls the shift control solenoid valves SOL1 to SOL3 according to the input signal.

FIG. 3 shows an example of the internal structure of the automatic transmission 1. The automatic transmission 1 includes a torque converter 20, an input shaft 21 to which engine power is transmitted via the torque converter 20, three clutches C1 to C3, two brakes B1 and B2, a one-way clutch F, and a Ravigneaux type planet. Gear mechanism 22, output gear 23, output shaft 24, differential device 2
5 and so on.

Forward sun gear 2 of the planetary gear mechanism 22
2a is connected to the input shaft 21 via a C1 clutch, and the forward sun gear 22a is connected to a transmission case 26 via a B1 brake. Further, the rear sun gear 22b is connected to the input shaft 21 via a C2 clutch. The carrier 22c is connected to the input shaft 21 via an intermediate shaft 27 and a C3 clutch. Further, the carrier 22c is connected to the transmission case 26 via a B2 brake and a one-way clutch F that allows only forward rotation (engine rotation direction) of the carrier 22c. The carrier 22c supports two types of pinion gears 22d and 22e, the forward sun gear 22a meshes with a long pinion 22d having a long shaft length, and the rear sun gear 22b meshes with a long pinion 22d via a short pinion 22e having a short shaft length. . A ring gear 22f that meshes only with the long pinion 22d is coupled to the output gear 23. The output gear 23 is connected to the differential device 25 via the output shaft 24.
Connected with.

FIG. 4 shows the operation of the clutches C1, C2, C3, the brakes B1, B2, and the one-way clutch F, and realizes four forward gears and one reverse gear. Figure 4
In the figure, ● indicates the operating state of hydraulic pressure. In addition, B
The two brakes are engaged at the time of reverse and at the first speed, but are engaged at the first speed only in the L range. In FIG.
Steady state operation of the third solenoid valves (SOL1 to SOL3) is also shown. ◯ indicates an energized state, and × indicates a non-energized state. The first solenoid valve SOL1 serves for B1 brake control, the second solenoid valve SOL2 serves for C2 clutch control, and the third solenoid valve SOL3 serves both for C3 clutch control and B2 brake control. The reason why the third solenoid valve SOL3 serves both for C3 clutch control and for B2 brake control is that the B2 brake is D, 2
This is because it does not operate in the range and is used only in the engine brake control of the L range and the transient control of the R range, and therefore does not interfere with the C3 clutch operated in the D range. Since the first to third solenoid valves SOL1 to SOL3 are required to perform delicate hydraulic pressure control, duty solenoid valves or linear solenoid valves are used.
Further, in this embodiment, the first solenoid valve SOL1
Is a normally closed type, and the second and third solenoid valves SOL2, 3 are normally open types.

Next, FIG. 5 shows the hydraulic control of the B1 brake (friction engagement element) when the gear is off-shifted from the first speed to the second speed.
Will be described with reference to. 6 and 7 show the turbine speed, the input current of the B1 brake control solenoid valve SOL1 and the time change of the B1 brake pressure when the control shown in FIG. 5 is carried out, and FIG. FIG. 7 shows a case where undershoot occurs.

When the control is started, the current gear is 1
It is determined whether or not the speed is high (step S1). If it is not the first speed, the process returns. Next, power off state,
That is, it is determined whether or not the throttle opening is fully closed or near the fully closed position (step S2). In the power-off state, the controller 2 determines a desired shift speed (second speed in this case) from the shift map according to the vehicle speed and the throttle opening at that time, and the solenoid valve SOL1 receives the shift command (OFF). An up command) is output (step S3). According to the output of the shift command, first, the solenoid valve is turned on for a certain period of time to reduce the rattling of the B1 brake (step S4), and then the solenoid current is kept constant to supply the initial hydraulic pressure of the B1 brake (step S5). ) Then, in order to gradually increase the engagement hydraulic pressure of the B1 brake, the solenoid current is increased at a constant gradient A (step S6).

The rattling period, the initial hydraulic pressure period, and the slope A period are control periods for bringing the B1 brake into a state immediately before engagement. That is, the rattling period is B
In order to quickly eliminate the gap (ineffective stroke) between the piston and the clutch plate for one brake, the solenoid current is kept ON for a certain period of time to rapidly move the piston toward the clutch plate. This backlash is implemented as needed. The initial hydraulic pressure is a period in which the piston is moved to a state where it makes contact with the first clutch plate as described above, and supplies a hydraulic pressure slightly higher than the return spring force to the B1 brake. The pressure of the initial hydraulic pressure is changed by the learning control described later, and the period thereof is changed depending on the operating state (for example, the length of time for which the turbine speed drops from the low speed stage to the high speed stage). The period of the gradient A is a period in which the piston, which has moved to the state of contacting the first clutch plate, is further pushed to move to the state immediately before the contact of all the clutch plates (the state immediately before the torque is generated). Increase the oil pressure with. The slope A and the period are always constant regardless of operating conditions.

The turbine speed starts to decrease due to the power off state. Therefore, it is determined whether or not the turbine rotational speed has dropped below a rotational speed that is higher than the rotational speed at the second speed by a certain value (step S7). That is,
Make a synchronization decision. The rotation speed at the time of performing the synchronization determination may be, for example, a value higher by 30 to 50 rpm than the turbine rotation speed at the 2nd speed.

In the synchronization determination, when it is determined that the turbines are synchronized, that is, when the turbine rotational speed drops below a rotational speed that is higher than the rotational speed at the second speed by a certain value, B1
In order to start the engagement of the brake, the solenoid current is increased at a constant gradient B (step S8). The slope B may be equivalent to the slope A above, but in this example A <
It is as B. The reason for this is to shorten the time until the end of gear shifting when undershoot is not detected, which will be described later.

Next, undershoot detection is performed (step S9). The undershoot detection is to detect whether or not the turbine speed is lower than the turbine speed at the 2nd speed, and is continuously performed for a certain period after the synchronization determination (step S10). This fixed period is, for example, about 100 to 300 msec. When the undershoot is not detected after a certain period of time after the synchronization determination, it means that the turbine speed has converged to the turbine speed at the second speed in the ideal state as shown in FIG. Therefore, it is determined that the shift can be completed, and the solenoid current is increased at a constant gradient C (step S11).
After continuing until a certain time has passed (step S1
2) Then, the B1 brake is engaged to end the shift (step S13). The gradient C of the solenoid current is control for engaging the B1 brake and is larger than the gradients A and B up to that point. The fixed period of C> A, B gradient C is a period for preventing the occurrence of an engagement shock, and it is also possible to immediately engage the B1 brake without providing the period of gradient C.

When an undershoot is detected within a certain period after the synchronization determination, as shown in FIG. 7, the solenoid current is increased at a constant gradient D (step S14) to suppress the undershoot B1. The engagement hydraulic pressure of the brake is continuously increased. Since the turbine speed is constantly monitored for a fixed period, if an undershoot is detected, the process can proceed to step S14 without waiting for the fixed period to end. The period of the gradient D is a period for reducing a reversal shock when the turbine speed described below changes from a decrease to an increase, and the gradient D may be equal to or smaller than the gradients A and B. At least smaller than the gradient C.

By increasing the solenoid current at the gradient D, the engagement hydraulic pressure of the B1 brake is gradually increased,
The point at which the turbine speed changes from falling to rising is detected (step S15). After the turbine speed is reversed to increase, the solenoid current is increased with a constant gradient E (step S16). The period of this gradient E is a period for alleviating the shock at the time of resynchronization, and in this embodiment, E <D.
Is set to. The reason is that the turbine speed is controlled to gradually increase and then gradually approach the second speed. In addition, the gradient E is the previous gradient D
It may be set equal to.

Next, a resynchronization determination is made, that is, it is determined whether or not the turbine rotation speed has risen above a rotation speed lower than the rotation speed at the second speed by a constant value (step S17). The rotation speed at the time of performing the resynchronization determination is, for example, a value lower than the turbine rotation speed at the time of the second speed by about 30 to 50 rpm. If it is determined in the resynchronization determination that the turbine rotation speed has increased from the rotation speed at the 2nd speed to a value lower than the rotation speed by a certain value, it is determined that the gear shift can be completed and the solenoid current is kept constant. Raise with gradient C (step S1
8) After continuing for a certain time (step S
19), the B1 brake is engaged, and the shift is completed (step S20). The control of steps S18 to S20 is the same as the control of steps S11 to S13, and steps S18 and S19 are omitted as needed and B1 is immediately set.
The brake may be engaged.

Even when the turbine speed undershoots as described above, the engaging hydraulic pressure of the B1 brake is not increased sharply as before (see FIG. 1), but the slopes B, D, E are increased. Since the sweep control for gently increasing the speed is performed, the shock of lifting the turbine speed can be eliminated, and the shift can be smoothly completed.

8 and 9 show a second embodiment of the present invention.
The undershoot amount of the automatic transmission also varies depending on the individual variation. When the amount of undershoot is too large, if the above-described sweep control is performed, it takes a long time to complete the shift. Therefore, in this embodiment, the initial hydraulic pressure (indicated by Pi in FIG. 8) of the friction engagement element is learned and controlled so that the amount of undershoot of the turbine speed during off-up falls within the set range. The initial hydraulic pressure Pi of the friction engagement element is a hydraulic pressure that moves the piston to a state in which it makes contact with the first clutch plate as described above. If this hydraulic pressure is changed, the state immediately before engagement of the friction engagement element at the time of synchronization determination is determined. Since it is possible to change, the amount of undershoot can also be changed. The initial oil pressure Pi
Is proportional to the solenoid current Ia, the initial oil pressure Pi can be controlled by the solenoid current Ia.

The undershoot amount is the maximum amount of decrease in turbine speed (indicated by ΔT in FIG. 8) or the time required for the amount of decrease from when the turbine speed becomes lower than the turbine speed of the high-speed stage to when the turbine speed rises. It can be defined by an integral value (shown by diagonal lines in FIG. 8). Specifically, the turbine rotation speed when the turbine rotation speed changes from a decrease to an increase is detected, and this rotation speed is set as the maximum decrease amount ΔT, or the turbine rotation speed is equal to or less than the turbine rotation speed at the second speed. The time integral from the point of time when it starts to rise may be calculated. By learning-controlling the initial hydraulic pressure of the friction engagement element so that the amount of undershoot falls within the set range in this manner, it is possible to realize a transmission that eliminates individual variations and eliminates shock and shift delay.

FIG. 9 shows an example of initial hydraulic pressure learning control.
In this example, the maximum decrease amount ΔT of the turbine speed is used as the undershoot amount. When the learning control starts, it is first determined whether or not an off-up gear shift command has been output (step S21). When the shift-up command for off-up is output, the initial hydraulic pressure (current value) Ia continues.
Is output (step S22). This initial hydraulic pressure Ia is
It is preset to a hydraulic pressure that causes undershoot. When the off-up is first experienced, the initial value of the initial hydraulic pressure Ia is output. However, after the off-up is experienced several times, the initial hydraulic pressure Ia is updated as described later, so that it is updated last time. The initial hydraulic pressure Ia may be output. Next, the maximum amount of decrease ΔT in turbine speed during undershoot is detected (step S23). Next, the maximum drop amount ΔT is compared with the set values Nmin and Nmax (step S24). If the maximum drop amount ΔT is within the set range, that is, if Nmin ≤ ΔT ≤ Nmax, the process ends without updating the initial hydraulic pressure Ia. On the other hand, if ΔT> Nmax, it is determined that the amount of undershoot is too large, and the initial hydraulic pressure Ia is added by a constant value α to the values up to that time to obtain the initial hydraulic pressure Ia.
Is updated (step S25). On the contrary, if ΔT <Nmin, it is determined that the amount of undershoot is too small, and the initial hydraulic pressure Ia is subtracted by a constant value α from the values up to that point to update the initial hydraulic pressure Ia (step S26). At the next off-up, the updated initial oil pressure Ia may be used to control the engagement oil pressure of the friction engagement element. In addition, in step S24, the maximum drop amount ΔT is compared with the upper and lower limit values, and if it is within the upper and lower limit values, the example is not updated, but it may be constantly updated so as to approach one set value. In this way, while the update of the initial hydraulic pressure Ia is repeated, the amount of undershoot is controlled within a predetermined range, and a stable gear shift without shock can be realized.

In the above-described embodiment, the off-up shift from the first speed to the second speed, that is, the hydraulic control of the B1 brake has been described, but other off-up shifts (for example, from the second speed to the third speed).
The same can be applied to the hydraulic control of the friction engagement element in the third speed to the fourth speed. The automatic transmission of the present invention is not limited to the automatic transmission having the three clutches C1 to C3 and the two brakes B1 and B2 as shown in FIG.

[0030]

As is apparent from the above description, according to the present invention, in the off-up shift, the undershoot of the turbine rotation is determined after the synchronization determination, and the engagement hydraulic pressure of the friction engagement element is engaged during the undershoot. Since it is made to rise at a gentler gradient than the rising gradient at the time, it is possible to eliminate the shock of lifting the turbine rotation at the time of undershoot,
This has the effect of smoothly ending the shift. In addition, since it is not necessary to perform integrated control of the engine and the transmission as in the conventional case, the control is simple and there is no restriction on the engine that can be used.

[Brief description of drawings]

FIG. 1 is a time change diagram of a turbine speed, a solenoid current, and an engagement hydraulic pressure during a conventional off-up shift.

FIG. 2 is a configuration diagram of an example of an automatic transmission according to the present invention.

FIG. 3 is a skeleton diagram showing a transmission mechanism of the automatic transmission of FIG.

4 is an operation table of each engagement element and solenoid valve shown in FIG.

FIG. 5 is a flowchart of an example of off-up shift control according to the present invention.

FIG. 6 is a time change diagram of turbine rotation speed, solenoid current, and engagement hydraulic pressure when undershoot does not occur.

FIG. 7 is a time change diagram of turbine rotation speed, solenoid current, and engagement hydraulic pressure when an undershoot occurs.

FIG. 8 is a time change diagram of turbine rotation speed, solenoid current, and engagement hydraulic pressure for explaining learning control.

FIG. 9 is a flowchart of an example of learning control.

[Explanation of symbols]

B1 brake (friction engagement element) SOL1 B1 brake control solenoid valve 2 controller

Claims (4)

(57) [Claims] 1. An automatic transmission for performing an upshift from a low speed stage to a high speed stage by supplying an engagement hydraulic pressure to a predetermined friction engagement element in a state where the throttle opening is fully closed or near the fully closed state. A shift control method, the step of determining that the input speed of the automatic transmission has dropped below a speed higher by a predetermined value than the input speed of the high speed stage; If it is determined that dropped by high below the rotational speed more predetermined value, the input rotational speed during a period until a predetermined time from the determination to detect whether or not lower than the input rotation speed of the high-speed stage During the process and until a predetermined time elapses from the determination , when the input rotation speed is equal to or higher than the input rotation speed of the high speed stage, the engagement hydraulic pressure of the friction engagement element is increased to fasten the friction engagement element. a step, a predetermined time after the determination When the input rotation speed until the over to is lower than the input rotation speed of the high speed stage, a step of the engagement oil pressure of the frictional engagement element is increased in gradual Do gradient from rising gradient during the fastening, the A shift control method for an automatic transmission having the same. 2. A step of determining that the input speed has changed from a decrease to an increase after the input speed has become lower than the input speed of the high speed stage, and the input speed has changed from a decrease to an increase. After that, a step of determining whether or not the input speed of the high-speed stage is lower than the input speed of the high-speed stage by a predetermined value or more, The shift control method for an automatic transmission according to claim 1, further comprising the step of increasing the engagement hydraulic pressure of the friction engagement element to fasten the friction engagement element. 3. When the input rotational speed becomes lower than the input rotational speed of the high speed stage, the maximum drop amount of the input rotational speed, or when the input rotational speed becomes lower than the input rotational speed of the high speed stage, starts to increase. 3. The shift control method for an automatic transmission according to claim 1, wherein the initial hydraulic pressure of the friction engagement element is learned and controlled so that the time integrated value of the amount of descent is within the set range. 4. When the input rotation speed becomes lower than the input rotation speed of the high speed stage, the engagement hydraulic pressure of the friction engagement element is continuously increased, and at the time when the input rotation speed is changed from decrease to increase. The shift control method for an automatic transmission according to any one of claims 1 to 3, wherein the rising gradient of the engaging hydraulic pressure is made smaller than the rising gradient up to that point.