JPH0921461A - Speed change control in automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a uncomfortable speed change feeling at the time of extremely low oil temperature by forbidding a speed change operation toward a low speed stage until a prescribed time has elapsed after the speed change operation toward a high speed stage was completed, when the discharging state of the hydraulic pressure is delayed more than a prescribed time from a frictional engagement element on the side on which the element is released at the time of a speed change. SOLUTION: When a speed change from a first speed stage to a second speed stage is to be achieved, first and second brake solenoid valves 35, 32 are put under the duty control of a controller 37, and by supplying the line pressure adjusted to a prescribed pressure to first and second brake servos 34, 31, the operation of first and second brakes 11, 12 can be controlled. At this time, if a down-shift to the first speed stage is performed at a very low temperature (e.g. oil temperature of -15 deg.C and below), the hydraulic pressure is supplied again before the discharge of the hydraulic pressure from the second brake 12 is thoroughly completed, because of the high viscosity of the oil or a delay of the motion of the second brake 12, resulting in excessive supply of the hydraulic pressure. To prevent this, the down-shift is forbidden for, for example, two seconds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention achieves a plurality of shift speeds by electronically controlling hydraulic pressures supplied to a plurality of friction engagement elements to selectively engage these friction engagement elements. The present invention relates to a shift control method for preventing deterioration of shift feeling at extremely low temperatures in the automatic transmission described above.

[0002]

2. Description of the Related Art An automatic transmission for a vehicle is a gear transmission by selectively supplying and discharging pressure oil to frictional engagement elements such as clutches and brakes to switch engagement states of clutches and brakes. Any of the rotating elements is connected to the transmission input shaft or is fixed to the transmission casing so that the gear ratio is automatically changed according to the operating state of the vehicle. In such an automatic transmission, in order to protect various devices and equipment and maintain a comfortable ride,
It is required that the shock during shifting is small. Therefore,
Various automatic transmissions have been proposed which are intended to reduce shift shock by appropriately electronically controlling pressure of pressure oil to a friction engagement element and its supply / discharge timing.
5-172231 and JP-A-6-331012).

In the conventional automatic transmission, when shifting from the current gear (eg, 1st gear) to the target gear (eg, 2nd gear), the 1st gear is achieved by a command from the controller according to a predetermined program. The frictional engagement element (release side frictional engagement element) being engaged is disengaged, and the frictional engagement element (coupling side frictional engagement element) that achieves the second speed is engaged, so that the transmission input shaft The rate of change of the rotation speed of is reduced to be equal to the target rate of change of the rotation speed,
The gripping operation of the release side friction engagement element and the coupling side friction engagement element is performed. As a result, the transmission path of the engine torque is switched from the release side frictional engagement element to the coupling side frictional engagement element. Hydraulic pressure is supplied to or discharged from each friction engagement element by changing the duty ratio of the solenoid valve from 0 to 10 according to a command from the controller.
It is controlled with the optimum hydraulic pressure by changing between 0%. When the duty ratio is 0%, the solenoid valve is continuously demagnetized, the hydraulic pressure is discharged, and the duty ratio is 10%.
In the case of 0%, the solenoid valve is continuously excited and the maximum hydraulic pressure is supplied.

FIG. 8 shows a time chart in the operation of re-grabbing the release side friction engagement element and the coupling side friction engagement element. As shown in the figure, in the re-holding operation of the disengagement side friction engagement element and the coupling side friction engagement element at the time of shifting from the first speed stage to the second speed stage, the solenoid valve of the disengagement side friction engagement element is operated. The duty ratio is set to 0% to discharge the hydraulic pressure (b), and the duty ratio of the solenoid valve of the coupling side friction engagement element is set to 10 based on the time until the release side friction engagement element starts slipping.
The supply of hydraulic pressure is started to 0% (c). This gives (a)
As shown by the solid line in Fig. 5, the hydraulic pressure starts to be supplied to the coupling side frictional engagement element at the timing when the discharge of the hydraulic pressure of the release side frictional engagement element is completed, and as shown in (d), The shift from the first gear to the second gear is achieved without changing the rotational speed at a predetermined change rate and without shock. Further, when shifting to the first speed after the shifting to the second speed is achieved, the duty ratio of the solenoid valve of the coupling side friction engagement element is set to 0% to discharge the hydraulic pressure (c), The duty ratio of the solenoid valve of the disengagement side frictional engagement element is set to 100% and the supply of hydraulic pressure is started (b). As a result, as shown by the solid line in (a), the hydraulic pressure is supplied to the release side friction engagement element again, and as shown in (d), the rotation speed of the input shaft is changed at a predetermined change rate. As a result, gear shifting from the second gear to the first gear is achieved without shock.

[0005]

In the conventional automatic transmission, since the friction engagement element is operated by hydraulic pressure, when the oil temperature is low, the oil discharge is delayed and the operating characteristics change. To do. In particular, during a gear shift operation at an extremely low temperature (for example, -15 degrees or less), the discharge of the hydraulic pressure of the disengagement side frictional engagement element is delayed as shown by the dotted line in FIG. 8 (a).
This is because the viscosity of the oil itself rises at low temperatures and it becomes difficult to discharge it, and because the oil sticks to the operating part of the release side frictional engagement element and hinders the discharge of oil and the operation of the operating part.
When shifting gears at extremely low temperatures, oil discharge is extremely slow. FIG. 9 shows the relationship between the return time S of the piston of the friction engagement element and the oil temperature when the hydraulic pressure is discharged. As shown in the figure, when the oil temperature becomes lower than -15 degrees, the piston return time S is significantly delayed. For this reason,
It can be seen that the discharge of the hydraulic pressure of the friction engagement element becomes extremely slow when the temperature is extremely low.

When the discharge of the hydraulic pressure of the friction engagement element becomes extremely slow, as shown in FIG. 8, immediately after the shift from the first speed stage to the second speed stage is achieved, the shift to the first speed stage is performed again. In this case, before the hydraulic pressure of the frictional engagement element on the release side is completely discharged during the shift to the second speed, the same frictional engagement element becomes the coupling side and the hydraulic pressure starts to be supplied. If the hydraulic pressure is supplied in a state where the hydraulic pressure is not completely discharged, the supply becomes excessive and a large shock occurs.

Such a situation can occur even in the case of upshifting, such as shifting from the first gear to the second gear, but in general, in an automatic transmission, the traveling situation of the vehicle in the case of upshifting. Since it is designed to shift according to
It is designed to be handled by electrical control. In the case of downshifting such as shifting from the 2nd gear to the 1st gear, the gear does not change frequently, such as when the accelerator pedal is suddenly depressed during low speed traveling, and the driver's intention is strong. Some shock is allowed.
For this reason, the current situation is that electrical control is not used. However, even if some shock is allowed, if the hydraulic pressure is excessively supplied, it will adversely affect the equipment and the like, resulting in a disadvantage in terms of durability.

[0008]

SUMMARY OF THE INVENTION A shift control method for an automatic transmission according to the present invention for solving the above-mentioned problems selects electronically the hydraulic pressures supplied to a plurality of friction engagement elements. In the automatic transmission configured to achieve a plurality of shift speeds by mechanically engaging, when the discharge state of hydraulic pressure from the friction engagement element on the release side at the time of shift is slower than a predetermined state. The shift to the low speed side is prohibited until a predetermined time elapses after the shift to the high speed side is completed.

Further, the determination when the discharge state of the hydraulic pressure is slower than a predetermined state is performed by whether or not the temperature state of the supplied hydraulic pressure is equal to or lower than a predetermined temperature state. Further, the determination when the hydraulic pressure discharge state is slower than a predetermined state is performed by the hydraulic pressure discharge pressure from the frictional engagement element that is released during the gear shift. Further, the predetermined time for prohibiting the shift to the low speed stage side is set stepwise according to the discharge state of the supplied hydraulic pressure. Further, the temperature state of the supply hydraulic pressure is an oil temperature obtained by directly detecting the temperature of the supply hydraulic pressure. Further, the state of the temperature of the supplied hydraulic pressure is set based on the temperature of the valve body of the automatic transmission, which is detected.

When the state of discharge of hydraulic pressure from the frictional engagement element that is released during shifting is slower than a predetermined state, that is,
If the temperature of the supplied hydraulic pressure is below a predetermined temperature at extremely low temperatures, or if the hydraulic discharge pressure from the friction engagement element on the release side does not decrease during gear shifting, the gear shifting to the higher gear side is performed. By prohibiting the shift to the low speed side until a predetermined time elapses after completion, the hydraulic pressure to the coupling side frictional engagement element is released after the hydraulic pressure from the release side frictional engagement element is sufficiently discharged. Supply.

The predetermined time for prohibiting the shift to the lower speed side is set stepwise so that the slower the discharge state of the supplied hydraulic pressure, the longer the predetermined time. Further, the state of the temperature of the supplied hydraulic pressure is determined by directly detecting the temperature of the supplied hydraulic pressure. Further, the state of the temperature of the supplied hydraulic pressure is determined by detecting the temperature of the valve body of the automatic transmission.

[0012]

1 is a schematic diagram of an automatic transmission to which a shift control method according to an embodiment of the present invention is applied.
Is a state of engagement of the frictional engagement element with respect to the shift stage, FIG. 3 is a main configuration of a hydraulic control device, FIG. A map showing an example of a pattern is shown.

The structure of the automatic transmission will be described with reference to FIG. In the illustrated automatic transmission, a crankshaft 1 of an engine (not shown) is integrally connected to a pump 3 of a torque converter 2, and the torque converter 2 includes a pump 3, a turbine 4, and a stator 6 connected to a case 5. It consists of The torque transmitted from the engine to the turbine 4 is transmitted by the input shaft 7 to a gear shift mechanism that is disposed at the rear of the turbine 4 and that achieves four forward gears and one reverse gear.

This gear speed change mechanism includes first to third three sets of clutches 8 to 10 as friction engagement elements, and first and second two sets of brakes 11 and 12 as friction engagement elements.
And two sets of first and second planetary gear mechanisms 13 and 14. The first planetary gear mechanism 13 includes a ring gear 15, a pinion 16, and a sun gear 17, and a carrier 18 that rotatably supports the pinion 16 and is also rotatable. Further, the second planetary gear mechanism 14 is arranged in series with the first planetary gear mechanism 13, and rotatably supports the ring gear 19, the pinion 20, the sun gear 21, and the pinion 20, and also rotates itself. And a carrier 22.

The sun gear 17 of the first planetary gear mechanism 13 is connected to the input shaft 7 via the first clutch 8, the carrier 18 of the first planetary gear mechanism 13 is provided with a gear 23, and the gear 23 outputs It meshes with the gear 25 of the shaft 24. A gear 26 is provided on the output shaft 24, and the gear 26 meshes with a gear 28 of the differential carrier 27, and the rotational force of the output shaft 24 is transmitted to the differential carrier 27. The ring gear 15 of the first planetary gear mechanism 13 is directly connected to the carrier 22 of the second planetary gear mechanism 14, and the ring gear 15 can be integrally connected to the case 5 by the second brake 12.

The carrier 22 of the second planetary gear mechanism 14 is connected to the input shaft 7 via the second clutch 9, and the sun gear 21 of the second planetary gear mechanism 14 is connected to the input shaft 7 via the third clutch 10. It The sun gear 21 can be integrally connected to the case 5 by the first brake 11.

The first to third clutches 8 to 10 and the first brake 11 and the second brake 12 which are friction engagement elements are
Each of the pumps 3 of the torque converter 2 is composed of hydraulic equipment including an engagement piston device or a servo device.
Pressure oil generated by an oil pump (not shown) connected to is selectively operated via a hydraulic control device (not shown). The hydraulic control device operates based on a command from the controller according to the position of the shift lever selected by the driver and the operating state of the vehicle (vehicle speed and throttle opening), and various gear stages are automatically operated. To be achieved.

In the present automatic transmission, how each friction engagement element works for each shift speed is as shown in FIG. In the figure, the mark ∘ indicates the engaged state by the hydraulic operation and the mark − indicates the released state. For example, shifting from the first gear to the second gear is performed by releasing the second brake 12 and engaging the first brake 11, that is, the second brake 1.
This is achieved by switching from 2 to the first brake 11.

The essential part of the hydraulic control system for achieving the shift from the first gear to the second gear will be described with reference to FIG. As shown in the figure, the second brake servo 31 that controls the operation of the second brake 12 is connected to a second pressure control valve 38 that regulates the line pressure via an oil passage 33.
The first brake servo 3 for controlling the operation of the brake 11
Similarly, a first pressure control valve 40 that regulates the line pressure is connected to 4 via an oil passage 36. The second brake solenoid valve 32 and the first brake solenoid valve 35 are in communication with the second pressure control valve 38 and the first pressure control valve 40, respectively. The duty solenoid valve 35 is duty-controlled based on a command from the controller 37. Therefore, the second brake solenoid valve 32 and the first brake solenoid valve 35 are duty-controlled by a command from the controller 37, whereby the second pressure control valve 38 and the first pressure control valve 40 set the line pressure to a predetermined pressure. Adjust the pressure to the second brake servo 3
It supplies to the 1st and 1st brake servo 34, and the operation | movement of the 2nd brake 12 and the 1st brake 11 is controlled. In the figure, 40 and 41 are the second brake 12 and the first brake 1.
1 is an accumulator arranged in the oil passages 33, 36 to the first brake 1 by the accumulators 40, 41.
2 and the pulsation of the pressure oil to the first brake 11 is absorbed.

When the duty ratio is 0%, the second brake solenoid valve 32 and the first brake solenoid valve 35 are continuously demagnetized and their operations are stopped, and the second brake servo 31 and the first brake are stopped. Hydraulic pressure is discharged to the servo 34. When the duty ratio is 100%, the second
The brake solenoid valve 32 and the first brake solenoid valve 35 are continuously energized, and the hydraulic pressure of the highest pressure is supplied to the second brake servo 31 and the first brake servo 34. Therefore, by controlling the duty ratio of the second brake solenoid valve 32 and the first brake solenoid valve 35 between 0% and 100% by the controller 37, the second brake servo 31 and the first brake servo 34 are controlled.
The hydraulic pressure can be adjusted and controlled with an appropriate pressure.

In the state where the first speed is achieved, the solenoid valve (not shown) for the first clutch 8 and the solenoid valve 32 for the second brake are excited (duty ratio 100%), and the line pressure is not reduced but the oil passage is reduced. Is supplied to 33 and the line pressure remains unchanged
The second servo 12 is supplied to the brake servo 31, and the second brake 12 is brought into the engaged state. Similarly, the first clutch 8 is engaged and the second clutch 9, the third clutch 10 and the first brake 11 are released.

When shifting from this state to the second speed, the shift is achieved by switching from the second brake 12 to the first brake 11. The situation of shifting to the second gear will be described based on FIG. As shown in (b), the duty ratio of the second brake solenoid valve 32 becomes 0% by the gear shift command to the second speed, and as shown in (a),
The hydraulic pressure supplied to the brake servo 31 starts to gradually decrease. When the hydraulic pressure decreases, the second brake 12 is disengaged and starts slipping. Based on the time until the second brake 12 starts slipping, as shown in (c), the solenoid valve for the first brake is The duty ratio of 35 is 10
It becomes 0%, and as shown in (a), the hydraulic pressure supplied to the first brake servo 34 gradually starts to rise and the first brake 11 is brought into the engaged state. In this way, the second brake 12 is released and the first brake 11 is brought into the engaged state, so that the shift from the first speed stage to the second speed stage is achieved.

In the above-described automatic transmission, at extremely low temperatures (oil temperature of -15 degrees or less), downshifting to the first speed stage is performed for 2 seconds after the shift from the first speed stage to the second speed stage is achieved. It is prohibited. That is, at extremely low temperatures, the discharge of hydraulic pressure becomes extremely slow, as shown by the dotted line in FIG. 8A, due to the viscosity of oil, the operation delay of the second brake 12, and the like. If the downshift to the first speed is performed in this state, as described above, the hydraulic pressure will be supplied to the second brake 12 again before the hydraulic pressure is sufficiently discharged from the second brake 12. Will be oversupplied. For this reason, downshifting to the first gear is prohibited for 2 seconds.
The operation of shifting to the first speed after the shift from the first speed to the second speed is achieved will be described with reference to FIG.

As shown in FIG. 4, when there is a gear shift command from the first gear to the second gear, the second brake 12 and the first brake 11 are gripped and the gear shift control is executed, and the input shaft is input. It is determined whether or not the shift from the first gear to the second gear has been completed by detecting the rotation speed of the. The shift control is executed until the shift is completed, and when it is determined that the shift from the first gear to the second gear is finished, the measurement of the elapsed time t from the end of the gear shift is started. After starting the measurement of the elapsed time t,
N ₀ and the throttle opening voltage V _TH are detected, and the gear position on the map is determined according to the detection result. FIG. 5 shows an example of a map for determining the shift speed. The determined gear is 1
If it is determined in step S1 whether or not it is a speed stage, and if it is determined to be other than the 1st speed stage, the gear shift is executed according to the conditions of each speed stage and the like.

[0025] If the gear position is determined to be 1st speed at step S1, detects the oil temperature T _O of the automatic transmission in the step S2. Oil temperature T _O of the automatic transmission of step S2 is or detects the oil pressure supplied to the friction engagement element directly (Claim 5), which is set based on the temperature of the valve body of an automatic transmission (the valve body) Temperature (Claim 6) is used. Also,
It is also possible to detect the temperature of the oil sent to the oil cooler. That is, the oil temperature T _O of the automatic transmission is detected by determining whether or not the temperature state of the supplied hydraulic pressure is a predetermined temperature state and determining whether the discharge state of the hydraulic pressure from the friction engagement element is later than the predetermined state. It is executed to determine whether or not (Claim 2).

[0026] After the oil temperature T _O of the automatic transmission is detected, whether the oil temperature T _O is -15 degrees or less is determined in step S3, it is determined that the oil temperature T _O is not below -15 ° In this case, since the temperature is not extremely low, the measurement of the elapsed time t from the end of the gear shift is ended and the gear shift control is executed by the gear shift command from the second gear to the first gear. The oil temperature T _O is -1 in step S3.
When it is determined that the angle is 5 degrees or less, the elapsed time t from the end of the shift is read in step S4. After reading the elapsed time t, it is determined in step S5 whether or not the elapsed time t is 2 seconds or more. If it is determined that the elapsed time t is less than 2 seconds, the vehicle speed N ₀ and the throttle opening voltage are determined again. Detect V _TH ,
The gear position on the map is determined based on the detection result. When it is determined in step S5 that the elapsed time t is 2 seconds or more,
That is, when it is determined that 2 seconds or more has elapsed (a predetermined time has elapsed) after the shift from the first gear to the second gear is completed, the measurement of the elapsed time t from the end of the gear shift is completed and the second gear is completed. The shift control is executed by the shift command from the first gear to the first gear.

Therefore, according to the shift control method described above,
2 after shifting from 1st gear to 2nd gear at extremely low temperature
Since the downshift to the 1st gear side is prohibited before the time of 2 seconds or more elapses, even if the discharge of the hydraulic pressure is extremely delayed due to the viscosity of the oil, the operation delay of the second brake 12, etc., it is 2 seconds or more. After the passage of time, the hydraulic pressure can be supplied to the second brake 12, and the hydraulic pressure will not be supplied again when the hydraulic pressure is not discharged from the second brake 12. Therefore, there is no possibility that the hydraulic pressure is excessively supplied at the time of downshifting to the first gear side and the device is adversely affected.

Another embodiment of the shift to the first speed after the shift from the first speed to the second speed has been achieved will be described with reference to FIG. In the example shown in FIG. 6, the time during which the downshift is prohibited is set stepwise according to the oil temperature (claim 4).

As shown in FIG. 6, when there is a gear shift command from the first gear to the second gear, the second brake 12 and the first brake 11 are gripped and the gear shift control is executed.
It is determined whether or not the shift from the first gear to the second gear is completed. The shift control is executed until the shift is completed, and when it is determined that the shift from the first gear to the second gear is finished, the measurement of the elapsed time t from the end of the gear shift is started. The measurement of the elapsed time t is started and the vehicle speed N ₀ and the throttle opening voltage V _TH
Is detected, and the shift speed on the map is determined according to the detection result. In step S6, it is determined whether or not the determined gear is the first gear. If it is determined that the gear is not the first gear, the gear shift is executed according to the conditions of each gear. Step S6
If it is determined that the gear position is the first gear in step S, step S
It detects an oil temperature T _O of the automatic transmission 7.

[0030] After the oil temperature T _O of the automatic transmission is detected, whether the oil temperature T _O is -5 degrees or less is determined in step S8,
When it is determined that the oil temperature T _O is not lower than −5 degrees, it is not a low temperature, so the measurement of the elapsed time t from the end of the gear shift is stopped and the gear shift command is issued from the second gear to the first gear. Execute control. If the oil temperature T _O is determined to be less than -5 degrees in step S8, it is set according to prohibition time t _a for prohibiting the shift to the first speed to the oil temperature T _O. That is, the oil temperature T _O is −
For 15 degrees or less, to set the prohibition time t _a at step S9 to 2 seconds, when the oil temperature T _O is less than -10 degrees beyond -15 degrees, sets the prohibition time t _a at step S10 in 1.5 seconds Then
Furthermore, when the oil temperature T _O exceeds −10 degrees and is −5 degrees or less,
Prohibition time in step S11 to set the t _a to 1 second.

In steps S9 to S11, the oil temperature T
After setting the prohibition time t _a in accordance with the _O, it reads the elapsed time t from the time of the shift end at step S12. After reading the elapsed time t, the elapsed time t is the prohibited time t _{a in} step S13.
It is whether the determination above, when the elapsed time t is determined to less than the inhibition time t _a, detects the vehicle speed N ₀ and the throttle opening voltage V _TH again, determine the gear position on the map by the detection result To do. In step S13, the elapsed time t is the prohibited time t
If it is determined to be equal to or greater than _a, i.e., when it is determined that the shift from the first speed stage to the second speed has exceeded the prohibition time t _a in accordance with the oil temperature from the end, from the time shift end After the measurement of the elapsed time t is completed, the shift control is executed by the shift command from the second speed stage to the first speed stage.

Therefore, according to the shift control method described above,
Because of the shift from the first speed to the low temperature to the second speed stage is not passed prohibition time t _a in accordance with the oil temperature from the completion prohibits downshift to the first speed stage, Ya viscosity of the oil Even when the discharge of the hydraulic pressure is delayed due to the operation delay of the second brake 12 or the like, the hydraulic pressure can be supplied to the second brake 12 in accordance with the delayed discharge state, and the hydraulic pressure is discharged from the second brake 12. The oil pressure will not be supplied again in a state where it is not. Therefore, there is no possibility that the hydraulic pressure is excessively supplied at the time of downshifting to the first gear side and the device is adversely affected.

Another embodiment of the shift to the first speed after the shift from the first speed to the second speed has been achieved will be described with reference to FIG. In the example shown in FIG. 7, the determination when the discharge state of the hydraulic pressure from the second brake 12 is slower than the predetermined state is performed by detecting the discharge pressure of the hydraulic pressure discharged from the second brake 12. This is an example (claim 3). Therefore, a pressure switch for detecting the discharge pressure of the second brake 12 is provided, and the pressure switch operates when the discharge pressure is a predetermined value (for example, 1 kgf / cm ² ) or more.

As shown in FIG. 7, when there is a gear shift command from the first gear to the second gear, the second brake 12 and the first brake 11 are gripped and the gear shift control is executed.
It is determined whether or not the shift from the first gear to the second gear is completed. The shift control is executed until the shift is completed, and when it is determined that the shift from the first gear to the second gear is finished, the measurement of the elapsed time t from the end of the gear shift is started. After the measurement of the elapsed time t is started, the vehicle speed N ₀ and the throttle opening voltage V _TH are detected, and the shift speed on the map is determined by the detection result.
Whether the determined shift speed is the first speed or not is step S1.
If it is determined in step 5 that the gear is not the first gear, the gear shift is executed according to the conditions of each gear. Step S15
If it is determined that the gear position is the first gear in step S, step S
At 16, the state of the pressure switch that detects the discharge pressure of the second brake 12 is read.

After the state of the pressure switch is read, it is determined in step S17 whether the pressure switch is operating. If it is determined that the pressure switch is not operating, the hydraulic pressure of the second brake 12 is discharged. Has been done enough 1
Since the pressure is lower than kgf / cm ² , it is estimated that the oil temperature is not low, the measurement of the elapsed time t from the end of the gear shift is completed, and the gear shift command from the second gear to the first gear is issued. Shift control is executed. If it is determined in step S17 that the pressure switch is operating, it is estimated that the oil temperature is low because the discharge pressure of the second brake 12 is delayed and the discharge pressure is 1 kgf / cm ² or more. The elapsed time t from the end is read. After reading the elapsed time t, it is determined in step S19 whether the elapsed time t is 2 seconds or more. If it is determined that the elapsed time t is less than 0.5 seconds, the vehicle speed N ₀ and the throttle opening voltage V _TH is detected, and the shift speed on the map is determined according to the detection result. When it is determined in step S19 that the elapsed time t is 0.5 seconds or more, that is, when it is determined that 0.5 seconds or more has passed (the predetermined time has elapsed) after the shift from the first gear to the second gear is completed. The measurement of the elapsed time t from the end of the shift is completed, and the shift control is executed by the shift command from the second gear to the first gear.

Therefore, according to the shift control method described above,
The discharge of the hydraulic pressure of the second brake 12 is delayed and the discharge pressure is 1 kg.
If f / cm ² or more, it is estimated that the temperature is low, and downshifting to the 1st gear side is prohibited until 0.5 seconds or more has elapsed after shifting from the 1st gear to the 2nd gear. Therefore, even if the discharge of the hydraulic pressure is delayed due to the viscosity of the oil or the operation delay of the second brake 12 at a low temperature, the hydraulic pressure can be supplied to the second brake 12 after 0.5 seconds or more. The hydraulic pressure will not be supplied again in the state where the hydraulic pressure is not discharged from the 2 brake 12.
Therefore, there is no possibility that the hydraulic pressure is excessively supplied at the time of downshifting to the first gear side and the device is adversely affected.

In the above embodiment, the downshift to the first speed side after shifting from the first speed stage to the second speed stage has been described as an example, but the same is applied to other shift speeds. can do.

[0038]

The shift control method for the automatic transmission according to the present invention is
When the discharge state of the hydraulic pressure from the friction engagement element that is released at the time of shifting is slower than the predetermined state, it is estimated that the temperature is low and the predetermined time elapses after the shift to the high speed side is completed. Since I tried to prohibit shifting to the low speed side until,
When the temperature of the supplied hydraulic pressure is below a predetermined temperature at extremely low temperatures, or when the hydraulic pressure discharge pressure from the frictional engagement element that is released during gear shifting does not drop, the gear shifting to the higher gear stage ends. The shift to the low speed side is not performed until a predetermined time elapses after the operation. As a result, the hydraulic pressure is not supplied to the friction engagement element again before the hydraulic pressure is sufficiently discharged from the disengagement side friction engagement element, and the hydraulic pressure is excessively supplied to cause a shift shock. It is possible to prevent adverse effects on equipment and devices.

Further, it is judged whether or not the state of the supplied hydraulic pressure is lower than a predetermined temperature state, that is, the hydraulic discharge pressure is lower than a predetermined value. Since it is performed depending on whether the temperature is high or whether the temperature of the supplied hydraulic pressure is lower than a predetermined value, it is possible to accurately estimate the low temperature. In addition, during the predetermined time when the shift to the low speed side is prohibited,
That is, since the oil temperature is set stepwise according to the oil temperature, it is possible to prevent the unshifted state from becoming longer than necessary.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an automatic transmission to which a shift control method according to an embodiment of the present invention is applied.

FIG. 2 is an operation element diagram showing an engagement state of a friction engagement element with respect to a shift speed.

FIG. 3 is a configuration diagram of a main part of a hydraulic control device.

FIG. 4 is a control flowchart of a shift control method according to an embodiment of the present invention.

FIG. 5 is a map showing an example of a shift pattern.

FIG. 6 is a control flowchart of a shift control method according to another embodiment of the present invention.

FIG. 7 is a control flowchart of a shift control method according to another embodiment of the present invention.

FIG. 8 is a time chart during shifting.

FIG. 9 is a graph showing the relationship between the return time of the piston of the friction engagement element and the oil temperature.

[Explanation of symbols]

 1 Crankshaft 2 Torque Converter 3 Pump 4 Turbine 5 Case 6 Stator 7 Input Shaft 8 1st Clutch 9 2nd Clutch 10 3rd Clutch 11 1st Brake 12 2nd Brake 13 1st Planetary Gear 14 2nd Planetary Gear 15 Ring Gear 16 Pinion 17 Sun gear 18 Carrier 19 Ring gear 20 Pinion 21 Sun gear 22 Carrier 23 Gear 24 Output shaft 25 Gear 26 Gear 27 Differential carrier 28 Gear 31 Second brake servo valve 32 Second brake solenoid valve 33 Oil passage 34 First brake servo 35 Solenoid valve for first brake 36 Oil passage 37 Controller

Claims (6)

[Claims] 1. An automatic transmission configured to achieve a plurality of shift speeds by electronically controlling hydraulic pressures supplied to a plurality of friction engagement elements to selectively engage the friction engagement elements, When the discharge state of the hydraulic pressure from the friction engagement element on the release side at the time of shifting is slower than the predetermined state, the shift to the low speed stage is continued until the predetermined time elapses after the shift to the high speed stage is completed. A shift control method for an automatic transmission, characterized by inhibiting shift. 2. The determination in the case where the discharge state of the hydraulic pressure is slower than a predetermined state is determined by whether or not the temperature state of the supplied hydraulic pressure is equal to or lower than a predetermined temperature state. 2. A shift control method for an automatic transmission according to 1. 3. The determination in the case where the hydraulic pressure discharge state is slower than a predetermined state is performed by the hydraulic pressure discharge pressure from the friction engagement element that is released during the gear shift. Item 2. A shift control method for an automatic transmission according to Item 1. 4. The automatic transmission according to claim 1, wherein the predetermined time period during which the shift to the low speed stage side is prohibited is set stepwise according to the discharge state of the supplied hydraulic pressure. Shift control method. 5. The shift control method for an automatic transmission according to claim 2, wherein the state of the temperature of the supplied hydraulic pressure is an oil temperature obtained by directly detecting the temperature of the supplied hydraulic pressure. 6. The automatic system according to claim 2, wherein the temperature state of the supplied hydraulic pressure is set on the basis of the temperature of the valve body of the automatic transmission by detecting the temperature of the valve body. Transmission shift control method.