JPH05332439A - Speed change control method of automatic transmission for vehicle - Google Patents

Abstract

(57) [Summary] [Purpose] The input hydraulic pressure is fed back to the operating pressure supplied to the frictional engagement element that establishes the high speed stage so that the input shaft rotational speed change rate matches the target value. A friction engagement element that increases toward the low speed gear synchronous rotation speed and completely disengages the high speed gear side friction engagement element after the input shaft rotation speed reaches the synchronous rotation speed while establishing the low speed gear. In the shift control method of the automatic transmission for a vehicle that engages with the gear shift gear, the shift is completed in a short time without causing a shift shock at the time of downshift. [Structure] During feedback control, the detected input shaft rotation speed Ntt1 and the target value N of the input shaft rotation speed change rate
The input shaft rotation speed Ntt2 after a predetermined time t2 from t't1 is predicted (S28), and when the predicted input shaft rotation speed is smaller than the low speed synchronous rotation speed (S30), the high speed side frictional engagement is performed. The hydraulic pressure of the element is forcibly reduced (S32).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control method for an automatic transmission for a vehicle, and more particularly to a shift control method suitable for power-on / downshift.

[0002]

2. Description of the Related Art An automatic transmission for a vehicle is provided with an input shaft to which a rotational force from an engine is input, an output shaft to output a driving force to a driving wheel side, and an input shaft between the input shaft and the output shaft. And a frictional engagement element such as a clutch or a brake that cooperates with the rotating element to control the rotation of the rotating element. here,
The friction engagement element is a hydraulic (hydraulic) actuated type, and this friction engagement element receives the supply of the hydraulic pressure whose pressure is controlled by the duty control based on the shift command according to the driving state of the vehicle. Thus, in the automatic transmission, the rotating element between the input shaft and the output shaft is appropriately selected, and the desired gear shift is automatically performed.

In the above-mentioned automatic transmission, when switching from the high speed stage to the low speed stage, the frictional engagement element on the high speed stage side (release side) is disconnected, and then the input shaft rotational speed is increased to the low speed stage synchronous rotational speed to synchronize. After confirming, the low speed stage side (coupling side) friction engagement element is engaged. More specifically, the engine is in a torque generation state (power-on state).
, The disengagement side frictional engagement element is temporarily disengaged, and the operating hydraulic pressure supplied to the disengagement side frictional engagement element is feedback-controlled from an appropriate point during the gear shifting operation to determine the input rotation change rate of the input shaft. While following the target rotational change rate, the rotational speed of the input shaft is increased toward the low-speed stage synchronous rotational speed, while the supply of operating hydraulic pressure to the coupling side friction engagement element is started. Then, when the input shaft rotation speed falls within a predetermined speed range with respect to the synchronous rotation speed, it is considered that the synchronization is completed, and then the hydraulic pressure of the disengagement side frictional engagement element is released to completely release the engagement. In order to completely engage the coupling side frictional engagement element, the maximum hydraulic pressure is supplied to it.

[0004]

By the way, when the input shaft rotation speed approaches the synchronous rotation speed, if the above-mentioned target rotation speed change rate is set to an extremely small value in order to avoid gear shift shock, the input shaft rotation speed is reduced. There is a problem in that the speed is excessively controlled, it takes a long time to reach the synchronization completion point, and the shift feeling is deteriorated such as a feeling of extension during the shift.

If the target rotational speed change rate is set to a high value,
Although the input shaft rotation speed reaches the synchronous rotation speed early, in order to engage the coupling side friction engagement element without causing a shift shock, it is necessary to reduce the target rotation speed change rate again before engagement. It is very difficult to control the output shaft torque. If the feedback control gain is set to a large value, hunting may occur depending on the system.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to automatically shift a vehicle in a short time without causing a shift shock during a downshift. It is to provide a shift control method for a transmission.

[0007]

In order to achieve the above-mentioned object, in the present invention, the operating oil pressure supplied to the friction engagement element for establishing the high speed stage is set to the target value of the input shaft rotational speed change rate. Feedback control to increase the input shaft rotation speed toward the low-speed stage synchronous rotation speed, and after the input shaft rotation speed reaches the synchronous rotation speed, complete engagement of the high-speed stage frictional engagement element. In the shift control method of the automatic transmission for a vehicle, in which the friction engagement element that establishes the low speed stage is engaged and the gear is downshifted, the input shaft rotation speed is detected and detected during the feedback control. Predict the input shaft rotation speed after a predetermined time from the input shaft rotation speed and the target value of the input shaft rotation speed change rate, and when the predicted input shaft rotation speed is smaller than the low speed stage synchronous rotation speed, high speed Shift control method for a vehicular automatic transmission, characterized in that forcibly reduces the hydraulic pressure on the side frictional engagement element is provided.

[0008]

When the input shaft rotation speed is feedback-controlled to a target value at which the rotation speed change rate is sufficiently small, a predetermined value is obtained from the detected input shaft rotation speed and the target value of the input shaft rotation speed change rate. The input shaft rotation speed after time can be predicted with high accuracy. Therefore, during feedback control of the input shaft rotation speed, the input shaft rotation speed after a predetermined time is predicted, and the predicted input shaft rotation speed and the low speed stage synchronous rotation speed are compared, and the predicted input shaft rotation speed is low. If the rotation speed is lower than the stage synchronous rotation speed, it is considered that the synchronization cannot be achieved at the predicted time point, and a measure is taken to accelerate the increase in the input shaft rotation speed. Feedback control of the operating oil pressure of the high-speed stage frictional engagement element to increase the input shaft rotation speed toward the low-speed synchronization speed means that the engine is in the power-on state. Forcibly reducing the operating oil pressure of the step friction engagement element means increasing the input shaft rotation speed.

[0009]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an example of an automatic transmission for a vehicle. In the figure, reference numeral 2 indicates an engine 2 which is a power source of the vehicle, and a crankshaft 4 of the engine 2 is directly connected to a pump 8 of a torque converter 6. The torque converter 6 is coupled to the case 16 via a pump 8, a turbine 10, a stator 12, and a one-way clutch 14. The one-way clutch 14 allows the stator 12 to rotate in the same direction as the crankshaft 4, but blocks rotation in the opposite direction.

The torque transmitted to the turbine 10 is transmitted to the input shaft 20 and is then transmitted from the input shaft 20 to the input shaft 2.
0 is transmitted to the gear transmission 22 arranged at the rear part of the transmission.
Here, the gear transmission 22 has a structure that achieves four forward gears and one reverse gear. The gear transmission 22 is
Three sets of clutches 24, 26, 28, two sets of brakes 30,
32, a set of one-way clutches 34, and a set of Ravigneaux type planetary gear mechanisms 36.

The planetary gear mechanism 36 is composed of a ring gear 38, a long pinion gear 40, a short pinion gear 42, and a carrier 48 that rotatably supports both of these pinion gears 40 and 42 and is also rotatable. The ring gear 38 is connected to the output shaft 50, and the front sun gear 44 is connected to the kickdown drum 5.
2. It is connected to the input shaft 20 via the front clutch 24. On the other hand, the rear sun gear 46 is connected to the input shaft 20 via the rear clutch 26. The carrier 48 includes a low reverse brake 32 and a one-way clutch 34 which are functionally arranged in parallel.
It is connected to the case 16 via the input shaft 20 and is connected to the input shaft 20 via a fourth speed clutch 28 arranged at the rear end of the transmission 22.

Here, the kick down drum 52 is
The kick down brake 30 can be fixedly connected to the case 16. The torque transmitted via the planetary gear mechanism 36 is transmitted to the output gear 60 fixed to the output shaft 50 so as to rotate integrally with the output shaft 50. Then, the output gear 60 passes through the idle gear 62 and the driven gear 64.
Is transmitted to the differential gear unit 72 to which the drive shaft 70 of the drive wheel is connected via the transfer shaft 66 and the helical gear 68 fixed to the driven gear 64.

Each of the above-mentioned clutches and brakes, which are frictional engagement elements, is included in a frictional engagement device provided with an engagement piston device, a servo device, or the like. This frictional engagement device is included in the torque converter 6. By being connected to the pump 8, it is operated by hydraulic pressure generated by an oil pump (not shown) driven by the engine 2. This hydraulic pressure is selectively supplied to each clutch and brake according to various operating conditions by a hydraulic control device described later. One gear is achieved. It should be noted that in Table 1, the mark “◯” indicates the engaged state of each clutch or the brake, and the mark “●” indicates that the rotation of the carrier 48 is stopped by the action of the one-way clutch 34.

[0014]

[Table 1] Next, in the gear transmission 22 shown in FIG. 1, an electronic hydraulic control device for achieving the gear stages shown in Table 1 will be described with reference to FIGS. 2 and 3. Note that FIG. 2 shows only the hydraulic control element portions that operate the front clutch 24 and the kickdown brake 30, and FIG. 3 shows the details of the front clutch 24. Since the entire structure and operation of this electronic hydraulic control device have been already known from Japanese Patent Laid-Open No. 58-46258, etc., description of hydraulic control elements for other brakes and clutches will be omitted.

The kickdown servo 31 as a reciprocating hydraulic actuator for controlling the operation of the kickdown brake 30 is slidably fitted in the housing defining the stepped cylinder hole 80 and the stepped cylinder hole 80. And a piston rod extending from the piston 59 to the outside of the housing, that is, an actuator rod 79. The tip of the actuator rod 79 is a kickdown brake 30, that is, an actuator rod 79. The brake shoe wound around the peripheral surface of the kick down drum 52 can be brought into contact with and engaged with the brake shoe. The piston 59 is formed by partitioning the first and second pressure chambers 82 and 83 into the stepped cylinder hole 80. As is apparent from FIG. 2, the first pressure chamber 82 is a step of the piston 59. It is defined between the surface and the stepped surface of the stepped cylinder hole 80.

Then, in the first pressure chamber 81 of the kickdown servo 31, the 1-2 shift valve 33 is provided through the oil passage 35.
Is connected, and the 1-2 shift valve 33 further includes
The shift control valve 37 is connected via the oil passage 41. An oil passage 83 is branched from the middle of the oil passage 35, and the oil passage 83 is connected to a 2-3 speed and a 4-3 speed shift valve (hereinafter, simply referred to as a 4-3 shift valve) 84. It is connected. The 4-3 shift valve 84 is further connected to bifurcated oil passages 85 and 86, and one of these two oil passages 85 is connected to the kick down servo 3
The first oil pressure passage 82 is connected to the first pressure chamber 82, and the other oil passage 86 is connected to the above-mentioned frot clutch 24. Although the front clutch 24 is schematically illustrated in FIG. 2, its details will be described later.

Here, the 1-2 shift valve 33 and the 4-3 shift valve 84 are spool type opening / closing valves which are opened and closed by the pressure supplied to the operation control ports 87 and 88, and the operation control ports The pressure to 87 and 88 is specifically introduced from a switching valve (not shown). For example, in the first gear, the 1-2 shift valve 3
The spool 55 of 3 is different from the case shown in FIG.
It does not receive the switching pressure through the operation control port 87 and is in the state of being displaced to the left end. So in this case,
The oil passage 35 communicates with the oil discharge port EX of the 1-2 shift valve 33, whereby the first pressure chamber 81 of the kickdown servo 31 is connected to the low pressure side. As a result, the piston 59 of the kick-down servo 31 is moved by the spring force of the compression coil spring 57 in the second pressure chamber 80, as shown in FIG.
The center is returned to the right, and the engagement of the kickdown brake 30 with the kickdown drum 52 is released.
At this time, the switching pressure is not supplied to the 4-3 shift valve 84 through the operation control port 88, so that the spool 89 is displaced to the left end as shown in FIG. .. Therefore, in this case, the oil passage 86 that communicates with the front clutch 24 includes the 4-3 shift valve 8
It is in a state of being connected to the low pressure side through the oil discharge port 90 of No. 4, and thus, the engagement of the front clutch 24 is released. In this case, since the oil passages 85 and 86 are always communicated with each other, the second pressure chamber 80 in the kickdown servo 31 is also connected to the low pressure side.

Further, in the second speed, the 1-2 shift valve 33 is switched to the illustrated switching position,
Further, the 4-3 shift valve 84 is also switched to the position shown. Therefore, in this case, when the pressure liquid is supplied to the first pressure chamber 81 of the kickdown servo 31 through the oil passages 41 and 35, the piston 59, that is, the actuator rod 79, moves leftward and kicks. The down brake 30 is engaged, while the pressure liquid in the front clutch 24 can be discharged through the oil passage 86 and the oil discharge port 90, whereby the front clutch 24 is discharged.
Will be released.

Further, in the third speed, the 1-2 shift valve 33 remains in the switching position shown in the figure, while the spool of the 4-3 shift valve 84 moves to the right. The oil passage 83 and the oil passages 85 and 86 are communicated with each other via the 4-3 shift valve 84, and the oil discharge port 90 is closed. In this case, the oil passage 83 is passed through the 1-2 shift valve 33.
The pressure fluid supplied to the front clutch 24 is supplied to the front clutch 24 via the 4-3 shift valve 84 and the oil passage 86, whereby the front clutch 24 reaches the engaged state. On the other hand, in the kickdown servo 31, the oil passages 86 and 85 are always in communication,
The pressure liquid supplied to the front clutch 24 is also supplied to the second pressure chamber 82 thereof, and at the same time, the pressure liquid of the same pressure is also supplied to the first pressure chamber 81 through the oil passage 35. .. In this case, the piston 5 of the kickdown servo 31
Since 9 is a stepped piston as described above, the piston 59 is displaced to the right along with the actuator rod 79 due to the difference in the pressure receiving areas at both ends thereof.
The engagement of the kick down brake 30 will be released. In this third speed state, the hydraulic pressure is also supplied to the fourth speed clutch 28 in the engaged state in preparation for shifting to the next fourth speed. In the third speed state, the clutch 28 is not involved in torque transmission regardless of the engaged state.

In the fourth speed, the 1-2 shift valve 33 is switched to the switching position shown in the figure, and the 4-3 shift valve 84 is also in the same manner as in the second speed. , Is switched to the position shown. Therefore, in this case, the kick down brake 30 is engaged and the front clutch 24 is disengaged. As shown in FIG. 3, a hydraulic multi-plate clutch is used for the front clutch 24, which has a large number of friction engagement plates 24a, and hydraulic oil is supplied from the oil passage 86 into the clutch 24 through a port 24b. Then, the piston 24c moves forward to frictionally engage the friction engagement plates 24a. On the other hand, when the hydraulic pressure supply from the oil passage 86 is cut off, the return spring 24d pushes the hydraulic oil to the oil passage 86 via the port 24b and the drain side via the check valve 24e. When the piston 24c returns, the frictional engagement between the frictional engagement plates 24a is released. Clutch 26, 2
8 and the like have the same structure as the clutch 24.

The shift control valve 37 is connected to an oil passage 61 at the left end of the shift control valve 37 as seen in FIG. 2 and an oil passage 63. The oil passage 61 is supplied with the control pressure obtained by adjusting the discharge pressure from the oil pump described above, and in the middle thereof, the hydraulic pressure supplied through the shift control valve 37 is opened and closed. An electromagnetic valve 67 for controlling the is inserted. This solenoid valve 6
The electronic control unit 7 is electrically connected to an electronic control unit (ECU) 65. The electronic control unit 65 controls the switching operation of the solenoid valve 67 by duty control. In addition, oil passage 6
An operating hydraulic pressure adjusted to a predetermined pressure is supplied to 3 from the above-mentioned oil pump. The hydraulic oil in the oil passage 61 is discharged to the low pressure side via the electromagnetic valve 67 that is opened / closed according to the duty ratio, so that the hydraulic pressure according to the duty ratio acts on the left end surface of the spool 69 of the shift control valve 37. Will be done. As a result, the shift control valve 37 regulates the hydraulic pressure from the oil passage 63 to generate the hydraulic pressure PKD in the oil passage 41.

Then, the electronic control unit 65 includes a solenoid valve 67.
In addition to controlling the opening and closing of the vehicle, a built-in gear change command output device that outputs a gear change command based on the operating state of the vehicle is included. The signal from the sensor or the detection device is input. For example, these sensors or detection devices include an engine rotation speed sensor that detects the rotation speed of the engine 2, a throttle valve opening sensor 103 that detects the throttle valve opening θ of the engine 2, and a rotation speed Nt of the input shaft 20. Input shaft speed sensor 101, output shaft speed sense of the driven gear 64 provided for detecting the rotational speed NO of the output shaft 50 corresponding to the vehicle speed, oil temperature detecting device for detecting lubricating oil temperature, select Lever selection position detection switch and auxiliary switch selection position detection device.

2, only the input shaft speed sensor 101, the throttle valve opening sensor 103, and the output shaft speed sensor 144 of the sensors and detection devices input to the electronic control unit 65 are shown. When a shift command to downshift the shift stage from the 4th speed to the 3rd speed is output, as is clear from Table 1, the kickdown brake 3
The 0 clutch must be disengaged while the front clutch 24 and the rear clutch 26 must be engaged. When the 4-3 shift command is output, as described above, the 1-2 shift valve 3
No. 3 is kept switched to the switching position shown in FIG. 2, and the 4-3 shift valve 84 is switched to the switching position in which its spool is moved to the right. By switching the shift valve 84, the engagement of the kick down brake 30 is released, and the input shaft 20 is separated from the output shaft 50 on the drive wheel side in the drive force transmission system. At this time, the rear clutch 26
The hydraulic pressure is supplied to the front clutch 24 when the pressure of the front clutch 24 does not slip due to the operation of the rear clutch control valve (not shown). Since the input shaft 20 is not yet in the engaged state, the input shaft 20 is still separated from the output shaft 50 on the wheel side in the driving force transmission system. As a result, when the engine 2 is in the power-on state, the input shaft 20
Increases its rotational speed. In this state, the electronic control unit 65 waits for the input shaft 20 to reach the predetermined rotation speed, as will be described later in detail. When the rotation speed reaches the predetermined rotation speed, feedback control of the working oil pressure supplied to the disengagement side kick-down brake 30 is started to prevent the rotation speed of the input shaft 20 from rising, and the working oil supplied to the coupling side clutch 24. While the feed rate of is also feedback-controlled, the rattling operation of the clutch 24 is performed. After confirming that the input shaft rotation speed Nt has reached the third speed synchronous rotation speed, the kick down brake 3
While the 0 clutch is completely released, the front clutch 24
Is completely engaged, and the 4-3 speed shift control is ended.

Next, the power-on downshift operation from the 4th speed to the 3rd speed executed by the electronic control unit 65 will be described in detail with reference to the drawings starting from FIG. The 4-3 shift down shift routine electronic control unit 65 first determines in step S10 of FIG. 4 whether or not a shift command for 4-3 power-on shift down is output, and this step is continued until this shift command is issued. Repeatedly execute and wait. When the shift command is output, the process proceeds to step S12, and the disengagement side frictional engagement element,
That is, the engagement of the kick down brake 30 is released.
When the engagement of the brake 30 is released, the input shaft 20 is disconnected from the output shaft 50 on the drive wheel side in the driving force transmission system, and the rotation speed of the input shaft 20 is the third speed synchronous rotation speed (this Since the gear ratio of the third speed is set to 1.0, the synchronous rotation speed starts increasing toward the output shaft rotation speed No).

The electronic control unit 65 controls the input shaft rotation speed Nt.
Is monitored, and the speed Nt is the predetermined rotation speed (K4 x No
) Wait for the number to increase (step S14). The predetermined rotation speed is set to a product value obtained by multiplying the output shaft rotation speed No by a predetermined value K4. When the input shaft rotation speed Nt exceeds the predetermined rotation speed (K4 x No), step S14 is performed.
If the determination result of is affirmative (Yes), the electronic control unit 6
5 starts feedback control of the hydraulic pressure supplied to the disengagement side kick down brake 30 and the coupling side front clutch 24 (step S16).

The feedback control of the kickdown brake 30 on the release side controls the rising speed of the input shaft rotation speed Nt so that the change rate Nt 'of the input shaft rotation speed Nt matches the target change rate Ni'. Feedback control of the hydraulic pressure supplied to the clutch 24 is performed. The feedback control method is not particularly limited, and conventionally known PID control can be applied. On the other hand, the target change rate Ni 'can be set to an appropriate value again according to the deviation ΔN between the input shaft rotation speed Nt and the third speed synchronous rotation speed. In this embodiment, as shown in FIG. 5, two types of target change rates Ni'1 and Ni'2 are prepared, and the initial target change rate Ni'1 is set to a high value, and the input shaft rotation speed is set. Nt is 3
The input shaft rotation speed Nt is set to a small value so that the input shaft rotation speed Nt gradually increases when approaching the high speed synchronous rotation speed. As a result, the input shaft rotation speed Nt rapidly increases first and then slowly increases toward the third speed synchronous rotation speed.

On the other hand, the feedback control of the coupling-side clutch 24 controls the supply speed of the hydraulic oil supplied to the clutch 24 so as to match the target value, whereby the aforementioned piston 24c of the clutch 24 is disabled. The stroke is controlled to be completed at a point slightly after the synchronization determination point. In this case, the feedback control method of the clutch 24 is not particularly limited.

Next, the electronic control unit 65 determines whether or not the input shaft rotational speed Nt has reached the above-mentioned synchronous rotational speed, and waits until the synchronous speed is reached (step S1).
8). The deviation ΔN between the input shaft rotation speed Nt and the third synchronous rotation speed is within a predetermined value range (| ΔN | ≦ n0, n0
Is, for example, 20 rpm),
The electronic control unit 65 determines that the input shaft rotation speed Nt has reached the third speed synchronous rotation speed.

When the input shaft rotation speed Nt reaches the synchronous rotation speed, the electronic control unit 65 releases the hydraulic pressure from the release-side kick-down brake 30 to completely release the engagement, while the coupling-side clutch 24 is released. Are completely engaged (step S19). This completes the shift control of the power-on downshift. Sync Prediction Routine Next, the sync prediction routine executed by the electronic control unit 65 will be described with reference to the flowchart shown in FIG. 6 and FIG. The synchronization prediction routine is executed every time the shift control of 4-3 power-on downshift is executed.

First, in step S20 of FIG. 6, the electronic control unit 65 determines whether or not the section in which the target change rate is set to the above-mentioned value Ni'1 has ended. If the result of this determination is negative, step S20 is repeatedly executed and waits until the end. When the section in which the target gear ratio is set to the value Ni′1 ends, the determination result of step S20 becomes affirmative, and the process proceeds to step S22 to start a timer (not shown) built in the electronic control unit 65. .. This timer is for measuring the elapse of t1 time as shown in FIG. 5, and the electronic control unit 65 waits for the elapse of t1 time by this timer (step S24).
The t1 time is set to an appropriate value together with t2 time described later in consideration of the optimum timing for detecting the synchronization of the input shaft rotation speed Nt.

When it is determined in step S24 that the time t1 has elapsed, the input shaft rotation speed Ntt1 at the time when the time t1 has elapsed is detected, and the input shaft rotation speed Ntt1 detected this time and the input shaft rotation speed Ntt1 detected last time are detected. The rotation change rate Nt't1 (= Ntt1-Ntt1-1) is calculated from -1 and -1 (step S26). Then, based on the obtained input shaft rotation speed Ntt1 and rotation change rate Nt't1, t2 is calculated based on the following equation.
Predict the input shaft rotation speed Ntt2 after a lapse of time (step S
28).

Ntt2 = Ntt1 + Nt't1 * t2 Next, the electronic control unit 65 determines whether or not the predicted input shaft rotational speed Ntt2 is lower than the third synchronous rotational speed (step S30). If this determination is negative, that is, if the input shaft rotation speed Ntt2 is predicted to be higher than the third-speed synchronous rotation speed at the time t2 has elapsed, the driver may feel a sense of extension during the gear shift. Then, the routine is finished.

On the other hand, if the determination result in step S30 is affirmative, it is predicted that the input shaft rotation speed Ntt2 will still be equal to or lower than the third speed synchronous rotation speed when t2 time has elapsed, and the driver is There is a risk of feeling a delay. In such a case, the process proceeds to step S32 and the duty ratio of the solenoid valve 67 is forcibly set to a small value by a predetermined value in order to reduce the hydraulic pressure supplied to the disengagement fourth speed clutch 28. Increase the rate of rotation change. As a result, the time required for the input shaft rotation speed Nt to reach the synchronous speed can be shortened.

In the shift control method of the present invention, the two friction engagement elements 24 and 30 as shown in FIG.
Not only is it applied to a configuration in which switching control is performed by 3, 84 and one solenoid valve 67, but also for each friction engagement element, a solenoid valve that controls the operating hydraulic pressure supplied to that friction engagement element is used. It goes without saying that the invention can also be applied to an automatic transmission provided with each.

[0035]

As is apparent from the above description, according to the shift control method of the automatic transmission for a vehicle of the present invention, the operating hydraulic pressure supplied to the friction engagement element for establishing the high speed stage is input. The input shaft rotation speed is detected during feedback control to increase the input shaft rotation speed toward the low speed stage synchronous rotation speed by matching the rate of change of the shaft rotation speed to the target value. Predict the input shaft rotation speed after a predetermined time from the target value of the input shaft rotation speed change rate,
When the predicted input shaft rotation speed is lower than the low speed synchronous rotation speed, the operating oil pressure of the high speed side frictional engagement element is forcibly reduced, so there is no shift shock during downshifting and stable operation. The shift can be completed in a short time, and the shift feeling can be improved.

[Brief description of drawings]

FIG. 1 is a skeleton diagram showing a power transmission path of an automatic transmission for a vehicle to which the method of the present invention is applied.

FIG. 2 is a hydraulic circuit diagram for controlling the operation of kickdown brake 30 and front clutch 24 shown in FIG.

FIG. 3 is a cross-sectional view showing details of a front clutch 24 shown in FIGS. 1 and 2.

FIG. 4 is a flowchart showing a control procedure of 4-3 power-on downshift.

FIG. 5 is a graph showing changes over time in an input shaft rotation speed Nt, a target rotation speed change rate Ni ′, and an actual rotation speed change rate Nt ′ during a 4-3 power-on downshift.

FIG. 6 is a flowchart of a synchronization prediction routine.

[Explanation of symbols]

 2 engine 20 input shaft 22 gear transmission 24 front clutch (friction engagement element) 30 kick down brake (friction engagement element) 31 kick down servo 33 1-2 shift valve 37 shift control valve 65 solenoid valve 84 4-3 shift valve

Claims (1)

[Claims] 1. The input hydraulic pressure supplied to a friction engagement element for establishing a high speed stage is feedback-controlled so that the input shaft rotational speed change rate matches a target value, and the input shaft rotational speed is synchronized with the low speed stage. After the input shaft rotational speed reaches the synchronous rotational speed, the frictional engagement elements that establish the low speed stage are engaged while the high speed stage side frictional engagement elements are completely disengaged. In a shift control method for an automatic transmission for a vehicle, the input shaft rotation speed is detected during the feedback control, and a predetermined value is detected from the detected input shaft rotation speed and a target value of the input shaft rotation speed change rate. Predict the input shaft rotation speed after time, when the predicted input shaft rotation speed is lower than the low speed stage synchronous rotation speed,
A shift control method for an automatic transmission for a vehicle, comprising: forcibly reducing the operating hydraulic pressure of a high speed gear side friction engagement element.