JP2003042281A - Shift controller for vehicular automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shift controller for a vehicular automatic transmission sufficiently suppressing a shifting shock or the like even against disturbance such as vehicular braking even without providing a highly accurate control apparatus in clutch-to-clutch downshift control during coasting. SOLUTION: Since an oil pressure within a shifting period of a hydraulic frictional engagement device regarding a coast downshift is set in response to a minute vehicular driving state by an oil pressure setting means 120, an engagement pressure of the hydraulic frictional engagement device within the shifting period is suitably controlled. For example, an initial oil pressure PB11 of an engagement pressure PB1 of a brake B1 and an initial oil pressure PC11 of an engagement pressure PC1 of a clutch C1 regarding a clutch-to-clutch 4 to 3 downshift are suitably set within a 4 to 3 downshift period. By this, accuracy of engagement operation is secured irrespective of the disturbance such as the vehicular braking, and the shifting shock or the like is sufficiently suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for an automatic transmission for a vehicle, and more particularly to a technique for performing hydraulic control of a hydraulic friction engagement device involved in coast down shift while maintaining a minute driving state. It is about.

[0002]

2. Description of the Related Art When a downshift is performed during coasting such as coasting or decelerating a vehicle in which the accelerator pedal is not operated, the automatic transmission for a vehicle which maintains the vehicle in a weak engine brake state is downshifted. A shift control device has been proposed. For example, JP-A-11-287
This is the device described in Japanese Patent No. 317. According to this, the vehicle is always kept in a state in which a predetermined engine braking force is applied during the clutch-to-clutch downshift, so that excessive engine braking force or shift shock is generated even in the downshift to the low speed gear stage. There is an advantage that it is not generated.

[0003]

By the way, in clutch-to-clutch downshifting in an automatic transmission for a vehicle,
To release the frictional engagement device on the release side and engage the hydraulic frictional engagement device on the engagement side at the same time, blowing of the input rotary shaft of the automatic transmission and temporary drop in output torque (tie-up) Are likely to occur, and expensive equipment with extremely high control accuracy for the engagement pressure when releasing the disengagement side friction engagement device and the engagement pressure when engaging the engagement side hydraulic friction engagement device Because of the demand, a general device that can be realized for a general vehicle cannot obtain sufficient control response to a disturbance such as vehicle braking, and a shift shock or the like may not be sufficiently suppressed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to perform clutch-to-clutch down shift control during coasting even if a vehicle with high precision is not provided. Another object of the present invention is to provide a shift control device for an automatic transmission for a vehicle, in which a shift shock or the like is sufficiently suppressed even with respect to a disturbance such as braking.

[0005]

A first object of the present invention to achieve the above object is to provide a shift of an automatic transmission for a vehicle of a type that performs a coast down shift while maintaining a minute driving state. The control device includes hydraulic pressure setting means for setting the hydraulic pressure within the shift period of the hydraulic friction engagement device involved in the coast down shift according to the minute driving state.

[0006]

[Effects of the First Invention] With this configuration, the hydraulic pressure setting means sets the hydraulic pressure within the shift period of the hydraulic friction engagement device involved in the coast down shift according to the minute drive state. Since the engagement pressure of the hydraulic friction engagement device during the shift period is appropriately controlled, the accuracy of the engagement operation is ensured regardless of disturbance due to braking or the like, and shift shock or the like is sufficiently suppressed.

[0007]

According to another aspect of the first aspect of the present invention, preferably, the coast downshift is achieved by a release operation of the release side hydraulic friction engagement device and an engagement operation of the engagement side hydraulic friction engagement device. The clutch-to-clutch down shift is performed, and the hydraulic pressure setting means sets the initial hydraulic pressure of the release side hydraulic friction engagement device and the engagement side hydraulic friction engagement device. With this configuration, the release operation of the disengagement side hydraulic friction engagement device and the engagement operation of the engagement side hydraulic friction engagement device are simultaneously executed, so that relatively delicate hydraulic pressure control is required. Even in the clutch-to-clutch down shift, the accuracy of the engagement operation is ensured, and shift shock and the like are sufficiently suppressed.

[0008] Further, preferably, there is provided an input / output rotational speed state detecting means for detecting an input / output rotational speed state of a fluid type transmission provided between the automatic transmission and the engine, and the hydraulic pressure setting means. The initial hydraulic pressures of the disengagement side hydraulic friction engagement device and the engagement side hydraulic friction engagement device are set based on the input / output rotation speed state. In a hydraulic power transmission device such as a torque converter or a fluid coupling provided in a power transmission path between an engine of a vehicle and driving wheels, the input / output rotational speed state represents the driving state of the vehicle. Therefore, in this way, the initial hydraulic pressures of the disengagement side hydraulic friction engagement device and the engagement side hydraulic friction engagement device are set based on the input / output rotation speed state corresponding to the minute drive state. The accuracy of the engagement operation in the clutch-to-clutch coast downshift is easily ensured, and the shift shock and the like are sufficiently suppressed.

Further, preferably, when the vehicle is in a braking state, braking time correction means for correcting the engagement pressure of the engagement side frictional engagement device to increase in real time according to the deceleration state during braking is further provided. With this configuration, the engagement pressure of the engagement-side friction engagement device is corrected in real time during sudden braking, so that the engagement operation in the clutch-to-clutch coast downshift is irrespective of the torque fluctuation during braking of the vehicle. The movement is preferably performed, and the shift shock or the like is sufficiently suppressed.

[0010]

A second aspect of the present invention for attaining the above object is to provide an automatic transmission for a vehicle of a type in which a coast downshift is performed while maintaining a minute drive state. A shift control device for controlling a hydraulic pressure within a shift period of a hydraulic friction engagement device involved in the coast down shift according to the minute drive state, and a shift hydraulic control device for controlling the hydraulic pressure. And a learning control means for correcting the hydraulic pressure by learning.

[0011]

[Effects of the Second Invention] With this configuration, the shift hydraulic pressure control means sets the hydraulic pressure within the shift period of the hydraulic friction engagement device involved in the coast down shift according to the minute driving state. Since the engagement pressure of the hydraulic friction engagement device during the shift period is appropriately controlled, the accuracy of the engagement operation is ensured regardless of the disturbance due to braking or the like, and the shift shock or the like is sufficiently suppressed. . Further, the learning control means corrects the hydraulic pressure controlled by the shift hydraulic pressure control means by learning, so that variations due to individual differences and changes over time are eliminated, the accuracy of engagement operation is ensured, and shift shock and the like are sufficient. Suppressed to.

[0012]

[Another Aspect of the Second Aspect of the Invention] Here, preferably, an input / output rotational speed state detecting means for detecting an input / output rotational speed state of the fluid transmission provided between the automatic transmission and the engine. The shift hydraulic pressure control means sets the initial pressure within the shift period of the hydraulic friction engagement device based on the input / output rotational speed state. In a hydraulic transmission such as a torque converter or fluid coupling that is installed in the power transmission path from the vehicle engine to the drive wheels, the input / output rotation state such as the input / output rotation speed difference or the input / output rotation speed ratio is It represents the driving state of the vehicle. Therefore, with the above configuration, since the initial pressure is set based on the input / output rotational speed state corresponding to the minute drive state, the accuracy of the engagement operation in the coast downshift is ensured, and the shift shock or the like is prevented. Sufficiently suppressed.

Further, preferably, the coast down shift is a clutch-to-clutch shift achieved by disengagement of the release side hydraulic friction engagement device and engagement of the engagement side hydraulic friction engagement device, The learning control means determines the tie-up state of the clutch-to-clutch shift based on the blowing amount of the output rotation speed of the fluid transmission, and the engagement-side hydraulic friction engagement device according to the tie-up state. The engaging pressure of is corrected by learning. With this configuration, the release operation of the disengagement-side hydraulic friction engagement device and the engagement operation of the engagement-side hydraulic friction engagement device are performed at the same time, thereby achieving a relatively delicate hydraulic control. Even in the clutch-to-clutch down shift, which requires the clutch-to-clutch down shift, the tie-up state of the clutch-to-clutch shift is determined based on the blowing amount of the output rotation speed of the hydraulic transmission, and the engagement side is determined according to the tie-up state. Since the engagement pressure of the hydraulic frictional engagement device is corrected by learning, the accuracy of the engagement operation of the engagement side hydraulic frictional engagement device is ensured, and shift shock and the like are sufficiently suppressed.

Further, preferably, the learning control means is such that the blowing amount of the output rotation speed of the fluid type transmission is substantially zero, and the input shaft rotation speed of the fluid type transmission is the output shaft rotation. It is determined that the clutch-to-clutch shift is a strong tie-up on the basis of returning from the state of exceeding the speed to the state of exceeding the speed and then returning to the state of exceeding the speed again, and the blowing amount of the output rotation speed of the fluid transmission is substantially zero. What happened
Also, it is determined that the clutch-to-clutch shift is a weak tie-up based on the state in which the input shaft rotation speed of the fluid transmission is maintained higher than the output shaft rotation speed. In this way, since the two-step tie-up state is discriminated, fine learning correction can be performed, so that the accuracy of the engagement operation of the engagement-side hydraulic friction engagement device is further ensured. , Gear shift shocks are sufficiently suppressed.

Further, preferably, the learning control means is arranged such that the release side hydraulic friction engagement device is set such that the slip-out period of the release side hydraulic friction engagement device in the clutch-to-clutch shift is a preset period. The engaging pressure of is corrected by learning. With this configuration, the accuracy of the engagement operation of the disengagement hydraulic frictional engagement device is ensured, and the shift shock or the like in the clutch-to-clutch shift is sufficiently suppressed.

Further, preferably, the sudden braking state determining means for determining the rapid braking state of the vehicle, and the learning control means for learning when the rapid braking state determining means determines the rapid braking state of the vehicle. And learning prohibition means for prohibiting. In this way, the learning prohibiting means prohibits the learning by the learning control means at the time of sudden braking, so that the erroneous learning is prevented and the shift shock or the like due to the erroneous learning is sufficiently suppressed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings.

In the vehicle of FIG. 1, the output of the engine 10 is the torque converter 12, F as a hydraulic transmission.
It is adapted to be transmitted to drive wheels (front wheels) not shown via the automatic transmission 14 for F drive and the differential gear device 16. The torque converter 12 includes a pump impeller 20 connected to a crankshaft 18 of the engine 10, a turbine impeller 24 connected to an input shaft 22 of the automatic transmission 14, and a non-rotating member via a one-way clutch 26. And a lockup clutch 32 connected to the input shaft 22 via a damper (not shown).

The automatic transmission 14 is of a single pinion type which is arranged coaxially on the input shaft 22 and has a so-called CR-CR coupled planetary gear mechanism in which a carrier and a ring gear are connected to each other. A pair of first planetary gear device 40 and second planetary gear device 42, a set of third planetary gear device 46 coaxially arranged on a counter shaft 44 parallel to the input shaft 22, and a counter shaft 44 thereof. An output gear 48 fixed to the shaft end and engaged with the differential gear unit 16 is provided. The planetary gear devices 40, 42, 4
The carrier that rotatably supports the respective components of 6, namely, the sun gear, the ring gear, and the planet gears that mesh with them,
Selectively connected to each other by four clutches C0, C1, C2, C3, or three brakes B1, B2,
B3 selectively connects to the housing 28 which is a non-rotating member. Further, the two one-way clutches F1 and F2 are engaged with each other or with the housing 28 depending on the rotation direction thereof. Since the differential gear device 16 is configured symmetrically with respect to the axis (axle), the lower side is omitted.

A pair of first members arranged on the input shaft 22.
Planetary gear unit 40, second planetary gear unit 42, clutch C
0, C1, C2, brakes B1, B2, and one-way clutch F1 for the main transmission unit MG having four forward gears and one reverse gear.
And a set of the planetary gear device 46, the clutch C3, the brake B3, and the one-way clutch F2 arranged on the counter shaft 44 constitute an auxiliary transmission unit, that is, an underdrive unit U / D. In the main transmission unit MG, the input shaft 22 is connected to the carrier K2 of the second planetary gear device 42, the sun gear S1 of the first planetary gear device 40, and the sun gear S2 of the second planetary gear device 42 via the clutches C0, C1, and C2. Each is connected. First planetary gear device 40
Ring gear R1 and carrier K of the second planetary gear set 42
2, the ring gear R2 of the second planetary gear set 42 and the carrier K1 of the first planetary gear set 40 are connected to each other, and the sun gear S2 of the second planetary gear set 42 is not connected via the brake B1. Housing 28 that is a rotating member
The ring gear R1 of the first planetary gear device 40 is connected to the housing 28, which is a non-rotating member, via a brake B2.
Are linked to. Further, a one-way clutch F1 is provided between the carrier K2 of the second planetary gear device 42 and the housing 28 which is a non-rotating member. Then, the first counter gear G1 fixed to the carrier K1 of the first planetary gear unit 40 and the ring gear R of the third planetary gear unit 46.
The second counter gear G2 fixed to 3 is meshed with each other. In the underdrive portion U / D, the carrier K3 of the third planetary gear device 46 and the sun gear S
3 are connected to each other via a clutch C3, and a brake B3 and a one-way clutch F2 are provided in parallel between the sun gear S3 and the housing 28 which is a non-rotating member.

The clutches C0, C1, C2, C3 and the brakes B1, B2, B3 are hydraulic friction engagement devices which are engagement-controlled by hydraulic actuators such as multi-plate clutches and band brakes. By operating the hydraulic actuators to selectively engage the clutch C and the brake B,
As shown in FIG. 2, any one of the five forward speeds is established. In FIG. 2, “◯” means engagement, “Δ” means engagement only during driving, and “x” means disengagement. In FIG. 2, for example, the fourth gear and the fifth gear
The 4 → 5 shift or the 5 → 4 shift between the first gear and the second gear is achieved by engaging or releasing the clutch C3, and the 1 → 2 shift or the 2 → shift between the first gear and the second gear is performed. One shift is achieved by engaging or releasing the brake B1. But the second
2 → 3 shift or 3 → between the third gear and the third gear
The two shifts are the release of the brake B1 and the engagement of the clutch C0.
Alternatively, it is a so-called clutch-to-clutch shift that is achieved by releasing one of the clutch C0 and the engagement of the brake B1 and simultaneously engaging the other.
Also in the 3 → 4 shift or the 4 → 3 shift between the third gear and the fourth gear, the clutch C1 is released and the brake B1 is released.
Engagement, or release of brake B1 and clutch C1
Is a so-called clutch-to-clutch shift.

In FIG. 3, a throttle valve 52, which is driven and operated by a throttle actuator 50, is provided in an intake pipe of an engine 10 of a vehicle, and the throttle valve 52.
An ISCV valve 54 is provided in parallel with the ISCV valve 54 for controlling the engine speed N _E during idling. The opening θ of the throttle valve 52 is controlled so as to be increased according to the operation amount of the accelerator pedal 56. Further, the engine rotation speed sensor 58 for detecting the rotation speed N _E of the engine 10 and the intake air amount Q of the engine 10
Intake air amount sensor 60 for detecting the temperature, intake air temperature T _A
Of the intake air temperature sensor 62, the throttle sensor 64 for detecting the opening degree θ of the throttle valve 52, the counter rotation speed sensor 65 for detecting the rotation speed (counter rotation speed) N _C of the second counter gear G2, and the vehicle speed V. a vehicle speed sensor 66 which detects a cooling water temperature sensor 68 for detecting the cooling water temperature T _W of the engine 10, hydraulic oil temperature sensor 69 for detecting the working oil temperature T _oIL in the automatic transmission 14, a brake switch for detecting the operation of the brake 70, shift lever 72
Of the turbine impeller 24, that is, the turbine rotational speed _NT (= rotational speed N _IN of the input shaft 22, that is, the torque converter 12).
The turbine rotation speed sensor 75 for detecting the output shaft rotation speed of the engine is provided. From these sensors, the engine rotation speed N _E , the intake air amount Q, the intake air temperature T _A ,
Opening of the throttle valve theta, counter rotational speed N _C, the vehicle speed V, the engine coolant temperature T _W, working oil temperature T _OIL, operation state BK of the brake, the operating position of the shift lever 72 Psh,
A signal representing the turbine rotation speed N _T or the like is supplied to the engine electronic control unit 76 and the shift electronic control unit 78.

The electronic control unit for engine 76 includes a CPU,
A so-called microcomputer including a RAM, a ROM, and an input / output interface, the CPU processes an input signal according to a program stored in the ROM in advance while utilizing the temporary storage function of the RAM, and executes various engine controls. For example, the fuel injection valve 80 is controlled to control the fuel injection amount, the igniter 82 is controlled to control the ignition timing, and the opening degree θ of the throttle valve 52 is changed from an actual stored relationship shown in FIG. Based on the operation amount of the accelerator pedal 56, it is controlled so as to be increased in accordance with the increase. The ISC valve 54 is controlled to increase the idle speed control or the engine speed N _E by a predetermined amount.

The electronic shift control device 78 is also a microcomputer similar to that described above, and the CPU uses the temporary storage function of the RAM to process the input signal in accordance with the program previously stored in the ROM 79, and the hydraulic control circuit 84. Each solenoid valve or linear solenoid valve is driven. That is, for example, the gear shift determination of the automatic transmission 14 and the lock-up clutch 24 is executed based on the actual throttle valve opening θ and the vehicle speed V from the pre-stored gear shift diagram shown in FIG. Solenoid valve S4, solenoid valve SR, linear solenoid valve so that the gear stage and engagement state can be obtained.
Drives SLT, SL1, SL2, SL3, etc.

FIG. 6 is a diagram simply showing a main part of the hydraulic control circuit 84. In FIG. 6, the solenoid valve SR causes its output pressure to act on the 2-3 shift valve 100 via the relatively long oil passage 98 in accordance with a command from the electronic shift control device 78 to operate the 2-3 shift valve 100. The first and second speeds and the third and fifth speeds are selectively switched. The solenoid valve S4 is a 2-3 shift valve 100 whose output pressure is switched to the third speed to the fifth speed side in accordance with a command from the electronic shift control device 78.
To the 4-5 shift valve 102 via the
The shift valve 102 is selectively switched between the first speed to the fourth speed and the fifth speed. Sunawawachi, 4-5 forward range when a shift valve 102 is switched is the first speed through the fourth speed side push ie D range pressure P _D is supplied to the brake B3, 4-5
When the shift valve 102 is switched to the 5th speed side, the D range pressure P _{D of the} shift valve 102 changes to the clutch C3 and the accumulator A.
Supplied to C3. The linear solenoid valve SLT supplies its output pressure to the back pressure control valve 104 according to a command from the electronic shift control device 78, generates a back pressure corresponding to the output pressure, and supplies it to the back pressure port of the accumulator AC3. Let

The linear solenoid valve SL1 supplies its output pressure to the B1 control valve 106 in accordance with a command from the electronic shift control device 78, generates and regulates an engagement pressure P _B1 corresponding to the output pressure, and brakes. B1 and its accumulator AB1 are supplied. Linear solenoid valve
SL2 supplies its output pressure to the C0 control valve 108 via the 2-3 shift valve 100 which is switched by the solenoid valve SR in accordance with a command from the electronic shift control device 78, and the engagement pressure P corresponding to the output pressure is supplied. _C0 is generated and regulated to be supplied to the clutch C0 and its accumulator AC0. The linear solenoid valve SL3 supplies its output pressure to the C1 control valve 110 in accordance with a command from the electronic shift control device 78, generates and regulates an engagement pressure P _C1 corresponding to the output pressure, and the clutch C1 and its clutch C1. Supply to accumulator AC1. The engagement pressure P _C0 of the clutch _C0 and the engagement pressure P _C1 of the clutch C1 are supplied to the clutch C0 and the clutch C1 via the clutch pressure supply control valve 112 switched by the engagement pressure P _C1 .

FIG. 7 is a functional block diagram for explaining the main part of the control function of the electronic shift control device 78. The hydraulic pressure setting unit 120, which also functions as the shift hydraulic pressure control unit, makes the shift determination based on the actual vehicle state, for example, the vehicle speed V and the throttle opening θ or the accelerator pedal operation amount from the prestored relationship shown in FIG. The shift output means 122 outputs a shift output signal so that the determined shift is executed. For example, when the point indicating the vehicle state crosses the 5 → 4 downshift to the low speed side in the shift diagram of FIG. 5, it is determined to be the 5 → 4 downshift, and the solenoid valve S
The clutch C3 is released by switching the 4-5 shift valve 102 to the 4th speed side by 4. Also, FIG.
When the point indicating the vehicle state crosses the 4 → 3 downshift to the low speed side in the shift diagram, it is determined to be the 4 → 3 downshift, and the brake B1 is released to realize the 4 → 3 downshift. Engaging pressure P for engaging the clutch C1
Output (drive) signals for generating _B1 and P _C1 are output to the linear solenoid valves SL1 and SL3. The duty ratio of this output signal is changed, for example, as shown in FIG. Since the linear solenoid valves SL1 and SL3 are normally open type, they have characteristics such that the output pressures P _B1 and P _C1 are zero when the duty ratio of the signal supplied thereto is 100%.

The shift hydraulic control unit 120 includes a brake B, which is a disengagement side hydraulic friction engagement device, in order to suitably realize the 4 → 3 down shift during coasting.
Disengagement side engagement pressure control means 122 for controlling the engagement pressure P _B1 of No. 1
And an engagement side engagement pressure control means 124 for controlling the engagement pressure P _C1 of the clutch C1 which is an engagement side hydraulic friction engagement device, and 4
→ The rotation synchronization of the clutch C1 which is the completion of the 3 downshift is performed by, for example, turbine rotation speed N _T and counter rotation speed N _C.
Synchronization determination means 12 for determining based on the fact that
And 6 are provided. The disengagement side engagement pressure control means 122 and the engagement side engagement pressure control means 124 operate according to a preset program or a feedback control formula to control the engagement pressure P _B1 of the brake _B1 and the clutch C1 from the start of the shift to the end of the shift. The engagement pressure P _C1 is sequentially changed. For example, the disengagement side engagement pressure control means 122 determines the input / output rotational speed difference N _SLIP (= N _E −N _T ) of the torque converter 12 and the counter rotational speed N from the relationship stored in advance as shown in FIG. 8, for example. The drive signal DP for determining the release initial pressure P _B1I based on _C and maintaining the release initial pressure P _{B1I
Supply B1I} to linear solenoid valve SL1. Further, the engagement side engagement pressure control means 124 is also stored in advance so that the initial hydraulic pressure increases as the input / output rotational speed difference N _SLIP increases and the counter rotational speed N _C decreases, as shown in FIG. 8, for example. From the relationship _{thus established} , the initial engagement pressure P _C1I is determined based on the input / output rotational speed difference N _SLIP (= N _E −N _T ) of the torque converter 12 and the counter rotational speed N _C , and the release initial pressure P _C1I is determined. A drive signal D _C1I for maintaining the same is supplied to the linear solenoid valve SL3. In such a clutch-to-clutch 4 → 3 downshift, the engagement side clutch C1 is gradually engaged while the release side brake B1 is slid while the tie-up and the increase of the input shaft rotation speed are maintained below a predetermined amount. So that the brake B
1 and clutch C1 release initial pressure P (release side standby pressure) P
_B1I and the initial engagement pressure (engaging side standby pressure) P _C1I are maintained. The engagement side engagement pressure control means 124, when the synchronization determination means 126 determines the rotation synchronization of the clutch C1 which is the completion of the 4 → 3 downshift, outputs the drive signal D _C1 supplied to the linear solenoid valve SL3. By setting the duty ratio to 0%, the engagement pressure P _C1 of the clutch C1 is increased to a predetermined value, for example, the maximum value.

The input / output rotational speed state detecting means 128 detects the input / output rotational speed difference N of the torque converter 12 which is a fluid transmission device during coasting such as coasting of a vehicle.
_SLIP a (= N _E -N _T) is detected by calculation based on the engine rotational speed N _E and the turbine rotational speed N _T. The inertia phase determination means 130 determines the starting point of the inertia phase in the 4 → 3 downshift or its vicinity, for example, by detecting the rising start point of the engine rotation speed N _E or the turbine rotation speed N _T.
The period t _T from the output of the 4 → 3 downshift to the start point of the rise of the turbine rotation speed N _T corresponds to the torque phase of the 4 → 3 downshift. The vehicle speed detection means 132 detects the counter rotation speed N _C at the rotation speed of the vehicle speed V or other members that change in association with it, for example, the fourth speed or lower.

The minute drive state control means 134 is a vehicle
After the 4th to 3rd downshift output,
For example, the predetermined section up to the relationship of FIG. 9 stored in advance
Input / output rotation speed difference N_SLIPAverage value N_SLIPAVOn the basis of
Engine speed increase amount ΔN _E(R.p.m) determined
Then, the lift amount ΔN_EISC requirement to obtain
By outputting to the ISC valve 54, the vehicle is turned on.
Rolling speed N_EIs the turbine speed N_TSlightly above
It is in a minute drive state. The above relationship is the average value N_{SLIP AV}Is large
Engine rotation speed increase amount ΔN_EIs smaller
Since it is defined as follows,
Input / output rotational speed difference N during coast driving_SLIPIs almost one
Maintained at a fixed value. This minute drive state control means 134
Is after the output of 4 → 3 downshift during coasting.
In the 4 → 3 downshift, a rotating element such as
Turbine rotation speed N of bottle impeller 24_TChange (rise) opening
From the starting point of inertia phase, which is the starting point, minutely drive the vehicle
The minute drive control for bringing into a moving state is executed. Also, this
The minute driving state control means 134 is shown in FIG.
Actual vehicle speed V
Rotating speed N_CBased on the reduction rate of
Upper amount ΔN_EDetermine the reduction rate of the
Jin rotation speed lifting amount ΔN_EIn real time
It Therefore, within the 4 → 3 coast downshift period
While the vehicle is braking, the
Jin rotation speed lifting amount ΔN_EAs a result of being reduced
Force rotation speed difference N_SLIPIs continuously reduced.

The sudden braking state determining means 136 determines whether or not a rapid braking state of the vehicle has occurred by using, for example, a vehicle speed rate or deceleration calculated from the vehicle speed V, a brake pedal operating force, and a braking hydraulic pressure as reference determination values. Judgment is made based on exceeding. When the sudden braking state determining means 136 determines that the rapid braking state of the vehicle has occurred, the minute drive control stopping means 138 determines the engine rotation speed lifting amount ΔN _E as shown at time t ₂ in FIG. By setting 0 to 0, the minute drive control by the previous minute drive state control means 140, which has been already performed after the 5 → 4 coast downshift output, is immediately stopped. The minute drive control by the previous minute drive state control means 140 is similar to the minute drive control by the minute drive state control means 134.

The braking correction means 142 is, for example, as shown in FIG.
From the pre-stored relationship shown in Fig. 5, the braking correction value ΔP _C1B is determined based on the deceleration state such as the actual counter rotation speed N _C (vehicle speed) or its change rate (deceleration), and the engagement side engagement pressure control is performed. correcting the engagement pressure P _C1 of the clutch C1 in real time by adding the braking correction value [Delta] P _C1B to the engagement pressure P _C1 of the clutch C1 is controlled in unit 124. During braking, especially during sudden braking, the counter rotation speed N _C decreases with respect to the engine rotation speed N _E , and the difference between them N _SLIP becomes large, and the engagement pressure P _{C1 of the} clutch C1 becomes gentle during coasting ( Since the engagement pressure P _C1 which tends to be low) cannot be grasped, the correction value ΔP _C1 during sudden braking is added as described above. The above relationship is set so that the correction value ΔP _C1B during sudden braking increases as the counter rotation speed N _C decreases or the rate of change thereof increases, so that the clutch C1 can be easily grasped easily even during sudden braking. It has been experimentally determined in advance to obtain it.

The blowing condition determining means 144 is a 4 → 3 course
Torque converter generated during downshift
12 output shaft rotation speed, that is, turbine rotation speed N_Tof
Blowing amount Δ which is the temporary rise amount or the integral value of its area
N_TF(R.p.m) is the actual turbine speed N_TWhen
Third speed turbine speed N_TCalculated based on the difference between
And its blowing amount ΔN_TFIs the preset blow rate judgment value
It is determined whether or not it has exceeded. Tie-up state determination means 14
6 occurs within the 4 → 3 coast down shift period
Tie-up condition such as the engagement of the brake B1 and the clutch
C1 is engaged at the same time and the automatic transmission is
14 is temporarily locked and a relatively strong shock
Strong tie-up or weaker shock
Blowing amount ΔN
_TF, And the input shaft rotation speed and output of the torque converter 12
Judgment based on the change in relative magnitude relationship with the force shaft rotation speed
Set. The tie-up state determination means 146, for example,
Turbine rotation speed N_TIs a temporary rise in
Amount ΔN_TFIs almost zero and the torque converter 1
2 input shaft rotation speed, that is, engine rotation speed N_EBut
-Bin rotation speed N_TAfter exceeding from above,
Clutch tsuku based on returning to the state of exceeding again
Latch 4 → 3 Coast down shift is a strong tie-up
And the blowing amount ΔN_TFIs almost zero, and
Jin rotation speed N_EIs the turbine speed N _TMore than
Based on the continuation or maintenance of
It is determined that the downshift is a weak tie-up.

The engagement side learning control means 148 is provided with the blowing state determining means 144 and the tie-up state determining means 146.
In accordance with the blowing state determined by the blowing state determining unit 144 and the tie-up state determined by the tie-up state determining unit 146, a learning correction value is determined so that the tie-up does not occur, and the learning correction value is included. Based on the above, the learning correction is performed by correcting the engagement pressure P _{C1 of the} clutch C1 controlled by the shift hydraulic pressure control unit 120 at the next 4 → 3 coast downshift. For example, when a strong tie-up is determined, the engagement pressure P _{C1 of the} clutch _C1
For example corrected by subtracting the correction value [Delta] P _C1I1 preset in order to lower the engagement initial pressure (engagement side standby pressure) P _C1i from the standby pressure P _C1i of the clutch C1. Also,
If a weak tie-up is determined, the correction set to be smaller than the correction value ΔP _C1I1 in order to lower the engagement pressure P _{C1 of the} clutch C1, for example, the initial engagement pressure (engagement side standby pressure) P _C1I. corrected by subtracting the value [Delta] P _C1I2 from the standby pressure P _C1i of the clutch C1. When it is determined that the blowing amount ΔN _TF exceeds the blowing amount determination value, the blowing amount ΔN _TF
The preset correction value ΔN _C1I3 is set to the standby pressure P of the clutch C1 so that N _TF falls below the blow amount determination value, for example.
_Correct by adding to _C1I . By such learning correction, a slight blow of the turbine rotational speed N _T occurs during the 4 → 3 coast downshift and the shift shock is minimized regardless of the individual difference such as the friction coefficient of the clutch C1 and the change over time. It is maintained in a proper gear shift state.

The release side learning control means 150 is 4 → 3 down
Until the start of sliding of brake B1 within the gear shift period
Period, that is, 4 → 3 downshift output from the above turbine
Rotation speed N_TUntil the start point of rising (4 → 3 down change
Period of fast torque phase) t_TIs a preset target period t
_TMAnd the engagement pressure P of the brake B1_B1Learning
Correct by That is, the actual slip of the brake B1
Period t until start of delivery _TAnd target period t_TMDeviation is small
Based on the deviation from the preset relationship to be
Determine the correction value and brake at the next 4 → 3 downshift
Standby pressure (initial pressure) P of B1_B1IThe correction value ΔP_B1I1To
Correction is performed by adding or subtracting.

The learning prohibiting means 152, in the case where the sudden braking state determining means 136 determines the rapid braking state of the vehicle, prevents the occurrence of a shift shock due to erroneous learning, so as to prevent the occurrence of a shift shock. Both the learning operation by the learning control means 148 and the release side learning control means 150 are prohibited.

12, FIG. 13, FIG. 14, and FIG. 15 are flow charts for explaining the main part of the control operation of the electronic shift control device 78. FIG. 12 shows an engagement side engagement hydraulic pressure control routine corresponding to the engagement side engagement pressure control means 124, and FIG. 13 corresponds to the engagement side learning control means 148.
14 shows the engagement side engagement pressure learning correction routine of FIG. 14, FIG. 14 shows the release side engagement oil pressure control routine corresponding to the release side oil pressure control means 122, and FIG. 15 shows the release side learning oil pressure control routine of FIG. The release side engagement pressure learning correction routine is shown respectively.

In FIG. 12, at SA1, it is determined whether or not clutch-to-clutch downshift, for example, 4 → 3 downshift output has been started. If the determination of SA1 is negative, this routine is ended, but if the determination of SA1 is affirmative, in SA2, the input / output rotational speed difference of the torque converter 12 is determined from the relationship stored in advance as shown in FIG. Initial engagement pressure P _{C1I of the} clutch C1 based on N _SLIP (= N _E −N _T ) and the counter rotation speed N _C
Is determined and the initial engagement pressure P _C1I is maintained. Next, the engagement side learning correction routine of SA3 corresponding to the engagement side learning control means 148 is executed. The engagement side learning correction routine is shown in FIG.

In FIG. 13, in SA31, whether or not the vehicle drive state is appropriate for learning correction is determined based on the input / output rotational speed difference N _SLIP of the torque converter 12 that reflects the vehicle drive state. It is determined based on whether or not it is in a driving state. If this determination is negative, this routine is terminated, but if affirmative, SA32 for determining a strong tie-up is executed, and if the determination of SA32 is negative, a weak tie-up is determined. SA34 for executing is executed. The SA 32 and SA 34 correspond to the tie-up state determination means 146. When the determination in SA34 is negative, SA36 corresponding to the blown state determination means 144 is executed.

If the determination at SA32 is affirmative, it means that the strong tie-up has been determined. Therefore, if the strong tie-up is determined at SA33, the clutch C
Engaging pressure P _{C1 of 1,} for example, initial engaging pressure (engaging side standby pressure) P
_The preset correction value ΔP _{C1I1 for lowering C1I} is corrected by subtracting it from the standby pressure P _{C1I of the} clutch C1. If the determination at SA34 is affirmative, it means that the weak tie-up is determined, so at SA35, the engagement pressure P _C1 of the clutch C1, for example, the initial engagement pressure (engagement side standby pressure) P _C1I is lowered. For the above correction value Δ
The correction value ΔP _C1I2 set smaller than P _C1I1 is corrected by subtracting from the standby pressure P _{C1I of the} clutch C1. If the determination at SA36 is affirmative, the blowing amount ΔN _TF is larger than the predetermined value.
In A37, a correction value ΔP _C1I3 set in advance so that the blow amount ΔN _TF falls below the blow amount determination value, for example.
Is corrected by being added to the standby pressure P _C1I of the clutch C1.

Returning to FIG. 12, in the subsequent SA4, the operating oil is
The actual hydraulic oil temperature should be
Degree T_OILBased on the engagement pressure P of the clutch C1_C1Change of
Imming is corrected. And the braking correction hand
At SA5 corresponding to the step 142, depending on the braking condition of the vehicle,
Engagement pressure P of clutch C1_C1Is corrected in real time
It For example, from the relationship stored in advance shown in FIG.
Counter rotation speed N _COr based on the rate of change
Dynamic correction value ΔP_C1BIs determined and the engagement pressure of the clutch C1 is determined.
P_C1The correction value ΔP during braking_C1BIs added
Engagement pressure P of the clutch C1_C1Corrected in real time
To be done.

In FIG. 14, at SD1, it is determined whether or not clutch-to-clutch downshift, for example, 4 → 3 downshift output has been started. If the determination in SD1 is negative, the routine is terminated, but if the determination is affirmative, in SD2, the input / output rotational speed difference of the torque converter 12 is determined from the pre-stored relationship as shown in FIG. Based on N _SLIP (= N _E −N _T ) and the counter rotation speed N _C , the initial release pressure P _{B1I of the} brake B1 is released.
Is determined, and the release initial pressure P _B1I is maintained. Then, the release side learning correction routine of SD3 corresponding to the release side learning control means 158 is executed. The release side learning correction routine is shown in FIG.

In FIG. 15, in SD31, it is determined whether or not the vehicle is in the sudden braking state, which is a prerequisite for learning correction, based on, for example, braking hydraulic pressure, vehicle deceleration, counter rotation speed N _C , and the like. If this determination is negative, this routine is ended, but if the determination is affirmative, S
At D32, whether or not the vehicle drive state is appropriate for learning correction is determined based on the input / output rotational speed difference N _SLIP of the torque converter 12 that reflects the vehicle drive state. For example, whether or not the vehicle drive state is a minute drive state. It is judged based on. If this determination is negative, this routine is terminated, but if the determination is affirmative, SD33 is used to calculate the actual start-up period t _T of the 4 → 3 downshift, and then SD
At 34, a correction value is determined based on the deviation from the preset relationship so that the deviation between the actual start-up period t _T and the target period t _TM becomes small, and the next 4 →
Standby pressure (initial pressure) P of brake B1 during 3 downshift
The correction value [Delta] P _B1I1 is corrected by being added or subtracted to _B1I.

Then, returning to FIG. 14, in the subsequent SD4, the engagement pressure P of the clutch C1 is based on the actual hydraulic oil temperature T _OIL so that the influence of the decrease in the viscosity of the hydraulic oil is suppressed.
The change timing of _C1 is corrected.

As described above, according to the present embodiment, the hydraulic pressure setting means 120 sets the hydraulic pressure within the shift period of the hydraulic friction engagement device involved in the coast down shift according to the minute driving state of the vehicle. Therefore, the engagement pressure of the hydraulic friction engagement device during the shift period is appropriately controlled. For example clutch-to-clutch 4 → 3 initial oil pressure P _C1i of the engagement pressure P _C1 of the initial oil pressure P _B1I and the clutch C1 of the engagement pressure P _B1 of the brake B1 involved in down shifting properly within 4 → 3 downshift period Is set. For this reason, the accuracy of the engagement operation is ensured regardless of the disturbance due to vehicle braking or the like, and shift shock or the like is sufficiently suppressed.

Further, according to this embodiment, the automatic transmission 14
Converter provided between the engine and the engine 10
(Fluid type transmission) 12 input / output rotational speed difference N_SLIPIs a car
The vehicle engine braking condition or the vehicle driving condition
It is detected as a parameter that represents
The stage 120 has its input / output rotational speed difference N._SLIPBased on
Engagement pressure P of rake B1_B1Initial hydraulic pressure P_B1IAnd crutch
Engagement pressure P of C1_C1Initial hydraulic pressure P_C1ITo set
, The input / output rotational speed difference N corresponding to the minute driving state _SLIPTo
Based on clutch to clutch 4 → 3 downshift
Engaging pressure P of brake B1_B1Initial hydraulic pressure P_B1Iand
Engagement pressure P of clutch C1_C1Initial hydraulic pressure P_{C1 I}Is 4 → 3 da
It is easy to set because it is set properly within the shift period.
In clutch to clutch coast down shift
Engagement accuracy is ensured and gear shift shock etc. is sufficient
Suppressed to.

Further, according to this embodiment, the braking time correction means 142 for increasing and correcting the engagement pressure P _C1 of the clutch C1 which is the engagement side frictional engagement device in real time according to the engine braking state during braking is provided. , Which is further provided, and at the time of braking, the engagement pressure P _{C1 of} C1 which is the engagement side frictional engagement device.
Since the engagement pressure of the clutch is corrected to increase in real time, the engagement operation in the clutch-to-clutch coast downshift is suitably performed regardless of the torque fluctuation at the time of sudden braking of the vehicle, and the shift shock or the like is sufficiently performed. Suppressed.

Further, according to this embodiment, the learning control means (engagement side learning control means 148, release side learning control means 15).
0), the hydraulic pressure controlled by the shift hydraulic pressure control means 120 is corrected by learning, so that variations due to individual differences and changes over time are eliminated, the accuracy of engagement operation is secured, and shift shock and the like are sufficiently suppressed. To be done.

Further, according to the present embodiment, the engagement side learning control means 148 determines the tie-up state of the clutch-to-clutch 4 → 3 downshift based on the blowing amount of the output rotation speed of the fluid transmission. However, since the engagement pressure P _C1 of the clutch C1 which is the engagement side hydraulic friction engagement device is corrected by learning according to the tie-up state, relatively delicate hydraulic control is required. Even in the clutch-to-clutch 4 → 3 downshift, the accuracy of engagement operation of the clutch C1 is ensured, and shift shock and the like are sufficiently suppressed.

Further, according to this embodiment, the engagement side learning control is performed.
The means 148 determines the turbine rotation speed N. _TBlowing amount ΔN_TFBut
It has become almost zero, and the engine speed N_EBut that
Turbine rotation speed N_TAfter the value has exceeded the
Based on the return to the above condition,
It is determined that the gear change is a strong tie-up, and the turbine rotation
Speed N_TBlowing amount ΔN_TFIs almost zero, and
Engine rotation speed N_EIs the turbine speed N_TOver
The above-mentioned 4 → 3 down change
Since it is determined that the speed is a weak tie-up, 2
The tie-up state of the stage is identified and fine learning correction is possible
Clutch C during a 4 → 3 downshift
The accuracy of the engagement operation of No. 1 is secured, and shift shock etc.
Sufficiently suppressed.

Further, according to the present embodiment, the disengagement side learning control means 150 is the brake B1 which is the disengagement side hydraulic friction engagement device in the clutch-to-clutch 4 → 3 downshift.
Since the engagement pressure P _{B1 of the} brake B1 is corrected by learning so that the slip-out period t _T becomes a preset period t _TM , the engagement of the brake B1 which is the release side hydraulic friction engagement device is corrected. The accuracy of the combined operation is also ensured, and the shift shock in the clutch-to-clutch 4 → 3 downshift is sufficiently suppressed.

Further, according to the present embodiment, the learning is performed when the sudden braking state judging means 136 for judging the sudden braking state of the vehicle and the sudden braking state of the vehicle is judged by the sudden braking state judging means 136. Control means (engagement side learning control means 14
8. The learning prohibiting means 152 for prohibiting the learning by the release side learning control means 150) is further included. Therefore, the learning prohibiting means 152 prohibits the learning by the learning control means 148, 150 at the time of sudden braking. Therefore, erroneous learning is prevented, and shift shock or the like due to the erroneous learning is sufficiently suppressed.

Although one embodiment of the present invention has been described above with reference to the drawings, the present invention can be applied to other modes.

For example, the hydraulic pressure setting means 1 of the above-mentioned embodiment
In 20, the hydraulic control in the 4 → 3 downshift is described, but the hydraulic control in the 3 → 2 downshift may be performed. Further, the engagement side learning control means 148 and the disengagement side learning control means 150 also explained learning control of the engagement side hydraulic pressure and the release side hydraulic pressure in the 4 → 3 downshift, but the engagement in the 3 → 2 downshift. It may be a learning control of the hydraulic pressure on the side and the hydraulic pressure on the release side.

Further, although the minute drive state control means 134 of the above-mentioned embodiment is configured to use the ISC valve 54 to raise the engine rotation speed N _E by a predetermined amount,
It is configured to use another engine rotation speed adjusting device such as a throttle actuator 50 that drives the throttle valve 52, a fuel injection valve that adjusts the fuel injection amount to the engine 10, an ignition timing adjusting device that adjusts the ignition timing of the engine 10. It was okay.

Further, although the input / output rotational state detecting means 128 of the above-described embodiment detects the input / output rotational speed difference N _SLIP of the torque converter 12, it may detect the input / output rotational speed ratio. Good. In this case, the input / output rotation speed ratio is used _{instead of the} input / output rotation speed difference N _SLIP as a parameter indicating the minute drive state.

Further, the minute drive state control means 134 of the above-described embodiment, the engine rotation speed lifting amount N _{E is} calculated according to the decreasing rate (deceleration) of the counter rotation speed N _C corresponding to the vehicle speed V.
However, other parameters such as wheel rotation speed may be used instead of the counter rotation speed N _C.

Further, in the above-described embodiment, the inertia phase start point is determined by detecting the rising start point of the turbine rotation speed N _T , but the elapsed time t _EL from the 4 → 3 downshift output is previously determined. It may be determined by detecting that the set time T _T has elapsed.

Further, in the above-mentioned embodiment, the input / output rotational speed difference N _SLIP of the torque converter 12 is used.
A fluid coupling may be used instead of the torque converter 12.

Further, in the above-described embodiment, the minute drive control means 134 starts the minute drive control from the inertia phase start point after the 4 → 3 downshift output, but it is not necessarily from the inertia phase start point. Good 4 → 3
It may be any time after the downshift output.

Further, the automatic transmission 14 of the above-mentioned embodiment is
Other formats may be used. For example, the automatic transmission 14
Is for FF (front engine-front drive) and is configured to obtain the fifth forward speed, but may be configured to obtain the fourth forward speed or lower or the sixth forward speed or higher. It may be configured for (front engine-rear drive).

Further, in the above-described embodiment, the 4 → 3 downshift of the automatic transmission 14 has been described.
→ Other downshifts such as 2 downshifts may be used.

Although not exemplified one by one, the present invention can be carried out in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a skeleton diagram illustrating a configuration of an automatic transmission for a vehicle to which an embodiment of the present invention is applied.

FIG. 2 is an engagement operation chart for explaining engagement operations of clutches and brakes for establishing each shift speed of the automatic transmission of FIG.

3 is a block diagram illustrating a shift electronic control device or the like provided in a vehicle for controlling the automatic transmission of FIG. 1. FIG.

FIG. 4 is a diagram showing a relationship between an accelerator pedal operation amount and a throttle valve opening amount used for controlling a throttle valve opening amount by the electronic control device of FIG.

5 is a diagram showing a shift diagram used for shift control of an automatic transmission by the shift electronic control device of FIG. 3;

FIG. 6 is a hydraulic circuit diagram schematically illustrating a configuration of a main part of the hydraulic control circuit of FIG.

FIG. 7 is a functional block diagram illustrating an example of a control function of the electronic shift control device of FIG. 3 and illustrating a main part of the control function.

FIG. 8 is a diagram showing a relationship used for determining an initial hydraulic pressure in the engagement side engagement pressure control means or the release side engagement pressure control means of FIG. 7.

9 is a diagram showing a relationship used for determining an engine rotation speed lifting amount (ISC valve required amount) in the minute drive state control means of FIG. 7.

10 is a diagram showing a relationship used in the minute drive state control means of FIG. 7 to determine a reduction rate of an engine rotation speed lifting amount based on a turbine rotation speed reduction rate.

FIG. 11 is a diagram showing a relationship used for calculating a correction value at the time of braking in the braking time correction means of FIG. 7.

12 is a flowchart illustrating a main part of a control operation by the electronic shift control device of FIG. 3, showing an Apply side engagement hydraulic pressure control routine.

FIG. 13 is a flowchart illustrating a main part of a control operation by the electronic shift control device of FIG. 3, showing an Apply-side learning correction routine.

14 is a flowchart for explaining a main part of a control operation by the electronic shift control device of FIG. 3, showing a drain side engagement hydraulic pressure control routine.

15 is a flowchart illustrating a main part of a control operation by the electronic shift control device of FIG. 3, showing a drain side learning correction routine.

16 is a time chart explaining a main part of a control operation by the electronic shift control device of FIG.

[Explanation of symbols]

10: Engine 12: Torque converter (fluid type transmission) 14: Automatic transmission 120: Hydraulic pressure setting means (shift hydraulic pressure control means) 124: Engagement side engagement pressure control means 128: Input / output rotation speed state detecting means 136: Means for determining sudden braking state 142: Compensation means during braking 148: Engagement side learning control means (learning control means) 150: Release side learning control means (learning control means) 152: Learning prohibition means C1: Clutch (engagement side hydraulic friction engagement device) B1: Brake (release side hydraulic friction engagement device)

Continued front page    (72) Inventor Naoyuki Sakamoto             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Toshimitsu Sato             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Atsushi Ayabe             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Hiromichi Kimura             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Hideaki Ogasawara             10 Akane, Takane, Fujii-cho, Anjo City, Aichi Prefecture             N AW Co., Ltd. (72) Inventor Noboru Shibata             10 Akane, Takane, Fujii-cho, Anjo City, Aichi Prefecture             N AW Co., Ltd. (72) Inventor Mitsuhiro Nakamura             10 Akane, Takane, Fujii-cho, Anjo City, Aichi Prefecture             N AW Co., Ltd. F-term (reference) 3J552 MA02 MA12 MA26 NA01 NB01                       PA02 RA02 RA06 RA09 RA13                       RB12 RB20 RC12 SA03 SA07                       SA15 TA11 TA13 TB17 VA07W                       VA32W VA33W VA37W VA42W                       VA42Z VC01W VD11W

Claims (10)

[Claims] 1. A shift control device for an automatic transmission for a vehicle, wherein a coast downshift is performed in a state where a minute drive state is maintained, the hydraulic control being involved in the coast downshift according to the minute drive state. A shift control device for an automatic transmission for a vehicle, comprising: a hydraulic pressure setting means for setting a hydraulic pressure within a shift period of the friction engagement device. 2. The coast down shift is a clutch-to-clutch down shift that is achieved by a disengagement operation of a release side hydraulic friction engagement device and an engagement operation of an engagement side hydraulic friction engagement device. 2. The shift control device for an automatic transmission for a vehicle according to claim 1, wherein the setting means sets an initial hydraulic pressure of the release side hydraulic friction engagement device and the engagement side hydraulic friction engagement device. 3. An input / output rotational speed state detecting means for detecting an input / output rotational speed state of a fluid transmission provided between the automatic transmission and an engine, wherein the hydraulic pressure setting means is provided with the input / output rotational speed state detecting means. 3. The shift control device for an automatic transmission for a vehicle according to claim 2, wherein the initial hydraulic pressures of the disengagement side hydraulic friction engagement device and the engagement side hydraulic friction engagement device are set based on the rotational speed state. 4. The automatic vehicular vehicle according to claim 1 or 2, further comprising braking time correction means for increasing the engagement pressure of the engagement side frictional engagement device in real time according to the deceleration state when the vehicle is in a braking state. Gear change control device for transmission. 5. A shift control device for a vehicle automatic transmission of a type that performs a coast down shift while maintaining a minute drive state, the hydraulic control being involved in the coast down shift according to the minute drive state. A shift hydraulic pressure control means for controlling the hydraulic pressure of the friction engagement device within the shift period, and a learning control means for correcting the hydraulic pressure of the hydraulic friction engagement device within the shift period set by the hydraulic pressure setting means by learning. A shift control device for an automatic transmission for a vehicle, comprising: 6. An input / output rotational speed difference detecting means for detecting an input / output rotational speed difference of a fluid type transmission provided between the automatic transmission and the engine, wherein the shift hydraulic pressure control is performed by the input / output rotational speed difference detecting means. 6. The shift control device for an automatic transmission for a vehicle according to claim 5, wherein an initial pressure within a shift period of the hydraulic friction engagement device is set based on a rotational speed difference. 7. The coast down shift is a clutch-to-clutch shift in which the release side hydraulic friction engagement device is released and the engagement side hydraulic friction engagement device is engaged at the same time. The control means determines a tie-up state of the clutch-to-clutch shift on the basis of the blowing amount of the output rotational speed of the fluid transmission, and determines the engagement of the engagement-side hydraulic friction engagement device according to the tie-up state. 7. The shift control device for an automatic transmission for a vehicle according to claim 6, wherein the combined pressure is corrected by learning. 8. The learning control means, when the blowing amount of the output rotation speed of the fluid transmission is substantially zero, and the input shaft rotation speed of the fluid transmission exceeds the output shaft rotation speed. From the above, it is determined that the clutch-to-clutch shift is a strong tie-up on the basis of returning to the higher state after being once decreased, and the blowing amount of the output rotation speed of the hydraulic transmission has become substantially zero. 8. The vehicle according to claim 7, wherein the clutch-to-clutch shift is determined to be a weak tie-up on the basis that the state where the input shaft rotation speed of the fluid transmission is higher than the output shaft rotation speed is maintained. Shift control device for automatic transmission. 9. The learning control means sets an engagement pressure of the release-side hydraulic friction engagement device such that a slip-out period of the release-side hydraulic friction engagement device in clutch-to-clutch shift is a preset period. 8. The shift control device for an automatic transmission for a vehicle according to claim 7, wherein the correction is performed by learning. 10. A sudden braking state determining means for determining a rapid braking state of the vehicle, and learning for prohibiting learning by the learning control means when the rapid braking state determining means determines the rapid braking state of the vehicle. 6. The shift control device for an automatic transmission for a vehicle according to claim 5, further comprising prohibiting means.