JPH05312261A - Method for controlling speed change in automatic transmission for vehicle - Google Patents

Abstract

PURPOSE:To prevent the occurrence of shocks in speed change when a first speed side clutch is turned on to carry out down-shift under the power-on condition while a second speed side clutch is disengaged. CONSTITUTION:Working oil pressure supplied to a second speed side clutch is released (step S74). When the start of down-shift is detected (affirmed in step S72) on the basis of rotational turbine speed Nt increased thereby, the duty ratio of a second speed (release) side solenoid valve is set to a value Dr0 to hold the working oil pressure in the second speed side at a predetermined value (step S78) until a predetermined time elapses, i.e., until the judging result in step S76 is affirmed. After the elapse of the predetermined time, advance is made to step 80 and the feed-back control of the second speed side clutch is started to increase the rotational turbine speed Nt toward a first speed synchronization speed N1 while adapting the change ratio of the rotational turbine speed Nt to coincide with a predetermined desired change ratio.

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 for an automatic transmission for a vehicle when a downshift is performed in a so-called power-on state.

[0002]

2. Description of the Related Art An automatic transmission mounted on an automobile is provided with a large number of friction engagement means such as hydraulic multi-plate clutches and hydraulic brakes. When the controller switches, the shift change of the automatic transmission is carried out. For example, when performing a downshift from the second speed to the first speed, the clutch that establishes the second speed (hereinafter referred to as the disengagement clutch) is disengaged and the clutch that establishes the first speed. (Hereinafter, referred to as coupling clutch)
Are engaged.

In this case, when the accelerator pedal in the driver's seat is depressed and the engine is in a so-called power-on state, when both clutches are disengaged, the rotational speed Nt of the input shaft of the automatic transmission is increased. Increases rapidly. Therefore, when performing the downshift in the power-on state, the controller first releases the operating hydraulic pressure of the disengagement side clutch and releases the engagement of this clutch to a predetermined position to increase the input shaft rotation speed Nt. wait.

When the actual start of the downshift is detected based on the increase of the input shaft rotation speed Nt, the controller starts the feedback control of the operating hydraulic pressure supplied to the disengagement side clutch, and the input shaft rotation speed Nt is The rate of change (Nt) 'is increased so as to match the predetermined target rate of change. As a result, a rapid increase in the input shaft rotation speed Nt is suppressed. After that, the controller operates the coupling side clutch at a predetermined timing to input the input shaft rotation speed Nt.
At the time point when the first rotation speed reached the first synchronous rotation speed, the engagement clutch was completely engaged and the downshift was completed.

The hydraulic pressure is supplied to each clutch via a solenoid valve whose duty ratio is controlled by a controller.

[0006]

However, in the above-described conventional shift control method, since the feedback control of the operating hydraulic pressure of the disengagement side clutch is started immediately after the start of the downshift is detected, the controller operates the disengagement side clutch. The duty ratio of the operated solenoid valve may be erroneously corrected.

That is, even if the controller supplies the control signal to the solenoid valve, the rise of the operating hydraulic pressure of the releasing side clutch is delayed due to a so-called hydraulic response delay phenomenon, and a predetermined amount of time is required before the piston of the releasing side clutch starts to move. There is a time lag. Therefore, since the controller monitoring the change in the input shaft rotation speed Nt does not immediately start changing the input shaft rotation speed Nt after operating the solenoid valve, it is determined that the operating hydraulic pressure of the disengagement side clutch is inappropriate. Make a mistaken judgment and continue to change the duty ratio of the solenoid valve.

Therefore, at the time when the piston of the disengagement side clutch actually starts to move, the duty ratio is set to a value larger than necessary, and as shown by the chain double-dashed line in FIG. There has been a problem that Nt and the output shaft torque fluctuate unstablely and a large shift shock occurs. The present invention has been made to solve the above-mentioned problems, and provides a shift control method for an automatic transmission for a vehicle, which is designed to prevent the occurrence of shift shock during a downshift operation in a power-on state. The purpose is to do.

[0009]

To achieve the above object, according to the present invention, the friction engagement means for establishing a high speed stage is disengaged while the friction engagement means for establishing a low speed stage is engaged. During downshift gear shift control to be combined, the hydraulic oil pressure supplied to the high-speed-stage friction engagement means is released, and when the downshift start is detected based on the rotational speed of the input shaft that increases, the high-speed-stage friction engagement mechanism is detected. Automatic transmission for a vehicle that starts feedback control of the operating hydraulic pressure supplied to the coupling means and increases the rotational speed of the input shaft toward the synchronous speed while matching the rate of change of the rotational speed of the input shaft with a predetermined target rate of change In a shift control method for a machine, when the downshift start is detected, the feedback control is started after the operating oil pressure of the high speed gear side friction engagement means is held at a predetermined value for a predetermined time. A.

[0010]

After setting the operating oil pressure of the high-speed-stage friction engagement means to a predetermined value (preferably set to an appropriate value each time by learning) that can slightly generate a transmission torque, A slight time lag occurs due to a so-called hydraulic response delay phenomenon until the high-speed-stage frictional engagement means actually moves to a position corresponding to hydraulic pressure.

According to the gear shift control method of the present invention, when the downshift start is detected, the operating oil pressure of the high speed gear side friction engagement means is held at a predetermined value for a predetermined time. The coupling means actually moves to the hydraulic pressure corresponding position. Then, after this movement is completed, the feedback control is started.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of an automatic transmission of an automobile that implements a hydraulic control method according to the present invention. Reference numeral 1 in the figure indicates an internal combustion engine, and the output of the engine 1 is transmitted to drive wheels (not shown) via an automatic transmission 2.

The automatic transmission 2 is composed of a torque converter 4, a gear transmission 3, a hydraulic circuit 5, a controller 40 and the like. The gear transmission 3 includes, for example, a gear train with four forward gears and one reverse gear, and a number of gear shift friction engagement means for performing gear shift operations by switching the gear ratio of the gear train. The shift friction engagement means is, for example, a hydraulic clutch or a hydraulic brake.

FIG. 2 is a partial configuration diagram of the gear transmission 3. A first drive gear 31 and a second drive gear 32 are rotatably arranged around the input shaft 3a. In addition, the input shaft 3a between the first drive gear 31 and the second drive gear 32,
Hydraulic clutches 33 and 34 are fixedly provided as gear shift friction engagement means. The drive gears 31 and 32 rotate integrally with the input shaft 3a by engaging the clutches 33 and 34, respectively.

The intermediate transmission shaft 35 arranged in parallel with the input shaft 3a is connected to the drive axle via a final reduction gear unit (not shown). A first driven gear 36 and a second driven gear 37 are fixedly mounted on the intermediate transmission shaft 35, and these driven gears 36 and 37 mesh with the drive gears 31 and 32, respectively. Therefore, when the clutch 33 and the first drive gear 31 are engaged,
The rotation of the input shaft 3a depends on the clutch 33, the first drive gear 3
1, transmitted to the first driven gear 36, the intermediate transmission shaft 35,
Thereby, for example, the first speed is established. Further, when the clutch 34 and the second drive gear 32 are engaged, the rotation of the input shaft 3a is caused by the clutch 34, the second drive gear 32,
It is transmitted to the second driven gear 37 and the intermediate transmission shaft 35, whereby the second speed is established, for example.

From the state in which the clutch 33 on the second speed side is engaged, while the engagement of the clutch 33 is released,
By engaging the clutch 34 on the high speed side, the automatic transmission 2
Shifts up from first gear to second gear. Conversely, by engaging the clutch 33 while releasing the engagement of the clutch 34 from the state in which the clutch 34 is engaged,
The automatic transmission 2 shifts down from the second speed to the first speed.

The clutches 33 and 34 are hydraulic multi-plate clutches. FIG. 3 shows a cross section of the clutch 33, which has a large number of friction engagement plates 50. When hydraulic oil is supplied into the clutch 33 from the oil passage 14 to be described later through the port 51, the piston 52 moves forward to frictionally engage the friction engagement plates 50. On the other hand, when pressed by the return spring 53,
When the piston 52 returns while discharging the hydraulic oil into the oil passage 14 through the port 51, the friction engagement between the friction engagement plates 50 is released.

In order to completely release the engagement of the clutch 33, each friction engagement plate 50 may be made to stand by at the standby position. At the standby position, a predetermined clearance required for the structure is provided between the friction engagement plates 50. Therefore, when engaging the clutch 33, first, each friction engagement plate 50 is moved by an ineffective stroke to a position where the above-mentioned clearance is substantially zero, that is, a position immediately before the friction engagement occurs. It is necessary to perform the filling operation.
Therefore, the rattling operation requires a rattling time.

The clutch 34 is also the clutch 33.
It is configured in the same manner as, and requires a predetermined play time. The hydraulic circuit 5 has a duty solenoid valve (hereinafter simply referred to as a solenoid valve) corresponding to each of the above-mentioned speed change friction engagement means, and each speed change friction engagement means, that is, each clutch or brake, is provided. Operate independently of each other.
Since each solenoid valve operates each clutch and brake in the same manner, the solenoid valve 11 for operating the clutch 33 will be described with reference to FIG. 4, and description of the other solenoid valves will be omitted.

FIG. 4 shows a part of the hydraulic circuit 5, which is equipped with a solenoid valve 11 capable of supplying hydraulic pressure to the hydraulic clutch 33. The solenoid valve 11 is a normally closed two-position switching valve, and has ports 11a to 11c at three locations. A first oil passage 13 extending to an oil pump (not shown) is connected to the first port 11a. A pressure adjusting valve (not shown) or the like is interposed in the middle of the first oil passage 13, and an operating hydraulic pressure (line pressure) adjusted to a predetermined pressure is supplied.

The second oil passage 14 extending to the hydraulic clutch 33 is connected to the second port 11b, and the third oil passage 15 extending to an oil tank (not shown) is connected to the third port 11c. These second and third oil passages 14,
Stops 16 and 17 are provided in the middle of 15, respectively. Further, the second oil passage 1 between the clutch 33 and the throttle 16
In the middle of 4, an accumulator 18 is connected.

The solenoid valve 11 is electrically connected to the controller 40, and the controller 40 controls the duty ratio at a predetermined cycle, for example, a control cycle of 50 hertz. When the solenoid 11e of the solenoid valve 11 is deenergized, the valve body 11f is pressed by the return spring 11g and the first port 11a is pressed.
And shuts off the second port 11b and the second port 1
1b and 3rd port 11c are connected. On the other hand, when the solenoid 11e is energized, the valve body 11f is
Lift against the spring force of the return spring 11g,
The first port 11a and the second port 11b are communicated with each other, and the second port 11b and the third port 11c are shut off.

The controller 40 includes a ROM (not shown),
It includes a storage device such as RAM, a central processing unit, an input / output device, a counter used as a timer, and the like. On the input side of this controller 40, various sensors, for example N
A t sensor 21, a No sensor 22, a θt sensor 23, a position sensor 24 of a select lever (not shown), etc. are electrically connected.

The Nt sensor 21 is a turbine rotation speed sensor for detecting the rotation speed Nt of the turbine of the torque converter 4 (that is, the input shaft of the gear transmission 3). The No sensor 22 is a transfer drive gear rotation speed sensor that detects a rotation speed No of a transfer drive gear (not shown). The controller 40
The vehicle speed V can be calculated based on this rotation speed No. The θt sensor 23 is a throttle valve opening sensor that detects a valve opening θt of a throttle valve arranged in the intake passage (not shown) of the engine 1. Further, the position sensor 24 is a sensor that detects the position of the automatic transmission 2 in the traveling mode selected by the select lever (not shown) arranged in the driver's seat. Each of these sensors 21 to 24 supplies a detection signal to the controller 40 at predetermined time intervals.

The controller 40 shifts the automatic transmission 2 in accordance with the control procedure stored in the storage device. That is, the controller 40 continues to monitor the signals from the Nt sensor 21, the No sensor 22, the θt sensor 23, and the like, and determines the shift speed suitable for the running state of the vehicle based on these signals. Then, for example, when recognizing the necessity of downshifting from the second speed to the first speed in the power-on state based on the vehicle speed V and the throttle valve opening θt, the controller 40 causes the second speed side (release side).
The clutch 34 and the first speed side (coupling side) clutch 33 are gripped and replaced.

FIG. 5 shows a control routine for downshifting from the second speed to the first speed in the power-on state, and the controller 40 repeatedly executes this routine when it recognizes the necessity of the downshift. In step S70 of FIG. 5, the controller 40 first determines whether or not the turbine rotation speed Nt is synchronized with the first synchronous rotation speed N ₁ . Specifically, as will be described later, the turbine rotation speed Nt increases and the first synchronous rotation speed N ₁ increases.
When the absolute value of the difference between and is reduced to a predetermined value (for example, 50 rpm) or less, the controller 40 detects that the synchronization between the turbine rotation speed Nt and the first synchronous rotation speed N ₁ is completed. Now, since the controller 40 has just detected the downshift command from the second speed to the first speed at time a in FIG. 6, the turbine rotation speed Nt is not synchronized with the first speed synchronous rotation speed N ₁ , Steps S70 to S7
Go to 2.

In step S72, the turbine rotation speed N
Whether t deviates from the second synchronous rotation speed N ₂ , that is,
It is determined whether or not the shift start point has been reached. Specifically, the rotation difference between each rotation speed Nt and N ₂ is a predetermined value ΔN.
When s ₁ (for example, 50 rpm) is reached, the controller 40
Detects out of synchronization between the turbine rotation speed Nt and the second synchronous rotation speed N ₂ . As described above, the controller 40, so immediately after detecting the downshift command to the second speed to the first speed, the turbine rotational speed Nt has not deviated from the rotational speed N ₂ second-speed synchronous, step from step S72 Proceed to S74.

At step S74, the disengagement clutch 34 is released.
The duty ratio of the solenoid valve (hereinafter, referred to as the release side solenoid valve) that supplies the working hydraulic pressure to 0 is set to 0% to disengage the release side clutch 34. In addition, the duty ratio of the solenoid valve (hereinafter, referred to as the coupling side solenoid valve) 11 that supplies the working hydraulic pressure to the coupling side clutch 33 is set to 100.
%, The rattling operation of the coupling side clutch 33 is performed, and thereafter, the duty ratio is set to the value Dka,
The clutch piston 52 is held at the standby position after the rattling operation is completed. The duty ratio Dka indicates the duty ratio of the coupling side solenoid valve 11 for holding the position of the piston 52 of the coupling side clutch 33, and is obtained experimentally, for example, and is stored in advance in the storage device. And
This value is appropriately updated each time by so-called learning.

Since the engine is in a power-on state now, when the disengagement clutch 34 is disengaged, the turbine rotation speed Nt starts to increase. The controller 40 repeatedly executes step S74 to perform the operation before the out-of-synchronization of the clutches 33 and 34, and waits for the start of the increase of the turbine rotation speed Nt. Turbine rotation speed Nt
When the determination condition of step S72 becomes affirmative (time point b in FIG. 6), the controller 40 starts the counter as the timer and then proceeds to step S76. Then, in step S76, it is determined whether or not the elapsed time of the counter has reached the predetermined time T1. This predetermined time T
1 is the time corresponding to the time lag due to the hydraulic response delay phenomenon from the start of the solenoid bias of the release side solenoid valve to the actual start of the movement of the piston of the release side clutch 34. This time T1 is obtained experimentally, for example, and is stored in advance in the storage device. Then, this time T1 is updated to an appropriate value each time by so-called learning.

Here, when the feedback control of the release side solenoid valve is started from the time point b in FIG. 6, the turbine rotation speed Nt does not immediately increase due to the hydraulic response delay phenomenon. It is erroneously determined that the working hydraulic pressure of 34 is insufficient.
In this case, the controller 40 increases the duty ratio of the disengagement side solenoid valve to increase the working oil pressure of the disengagement side clutch 34, as shown by the two-dot chain line in the figure, and as a result, the turbine rotation speed Nt increases. I'm blunt. Therefore, the controller 40 reduces the duty ratio to reduce the operating oil pressure, and the output shaft torque greatly increases and decreases. That is, in order to suppress the fluctuation of the output shaft torque during the downshift, the feedback control of the release side solenoid valve is prohibited until the piston of the release side clutch 34 actually starts moving to generate the transmission torque. Better to do.

Immediately after the determination result is affirmative in step S72 of FIG. 5, the elapsed time of the counter has not reached the predetermined time T1, so the determination condition of step S76 is negative, and the controller 40 proceeds to step S78. In step S78, the controller 40 sets the duty ratio of the release side solenoid valve to the predetermined value Dr0 and does not execute the feedback control. This prevents the duty ratio and the hydraulic pressure from increasing too much as shown by the chain double-dashed line in FIG. On the other hand, for the coupling side solenoid valve 11, the duty ratio is set to the value Dka, and the coupling side clutch 33 is continuously held at the standby position as in step S74.

This routine is repeatedly executed, and b in FIG.
When the time T1 elapses from the time point, the determination condition of step S76 becomes affirmative, and the controller 40 proceeds to step S80.
Proceed to (at time c in the figure) In step S80, the controller 40 gradually releases the engagement of the disengagement side clutch 34 while performing feedback control, and the turbine rotation speed Nt.
Is increased toward the _first synchronous rotation speed N ₁ so that the change rate (Nt) ′ matches a predetermined target change rate (after the time point c in the figure). The coupling side solenoid valve 11
For, the duty ratio is set to the value Dka and the holding of the coupling side clutch 33 at the standby position is continued.

Then, this routine is repeatedly executed,
After detecting that the turbine rotation speed Nt is synchronized with the first synchronous rotation speed N ₁ (Yes in step S70), the duty ratio of the release side solenoid valve is set to 0% and the duty of the coupling side solenoid valve 11 is changed. The respective rates are set to 100%, the disengagement side clutch 34 is completely disengaged, and the coupling side clutch 33 is completely engaged, and this downshift is completed (step S82).

In this embodiment, the case of performing the downshift from the second speed to the first speed in the power-on state has been described, but the mode of the downshift is from the second speed to the first speed. It is not limited to downshifts.

[0035]

As described above, according to the present invention, when the start of the downshift is detected based on the increase in the input shaft rotation speed, the operating oil pressure of the high speed stage side friction engagement means is set to a predetermined value for a predetermined time. Since the feedback control of the operating hydraulic pressure of the high speed side frictional engagement means is started after holding the value at, the fluctuation of the output shaft torque at the time of downshift is suppressed, and the excellent effect that the shift shock can be reduced can be achieved. ..

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an automatic transmission for a vehicle in which a shift control method according to the present invention is implemented.

FIG. 2 is a schematic configuration diagram showing a part of a gear train in the gear transmission of FIG.

FIG. 3 is a cross-sectional view showing the clutch of FIG.

FIG. 4 is a schematic configuration diagram showing a part of a hydraulic circuit for operating the clutch of FIGS. 2 and 3.

5 is a flowchart showing a control procedure of a downshift routine from second speed to first speed in a power-on state of the engine, which is executed by the controller shown in FIGS. 1 and 4. FIG.

6 is a diagram showing a relationship between a turbine rotation speed Nt and a duty ratio of a release side solenoid valve, etc. when the control procedure of FIG. 5 is executed.

[Explanation of symbols]

 1 Engine 2 Automatic Transmission 3 Gear Transmission 5 Hydraulic Circuit 11 Solenoid Valve 33 First Speed Side Clutch 34 Second Speed Side Clutch 40 Controller

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Katsuhiro Hatta 5-3-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation

Claims (1)

[Claims] 1. A frictional engagement means for releasing a high speed gear is disengaged, while a frictional engagement means for establishing a low speed gear is engaged. When the start of the downshift is detected based on the rotational speed of the input shaft which is increased by releasing the operating oil pressure being maintained, feedback control of the operating oil pressure to be supplied to the high speed stage side friction engagement means is started, and the input In a shift control method for an automatic transmission for a vehicle, which increases a rotational speed of an input shaft toward a synchronous speed while matching a rate of change of a rotational speed of a shaft with a predetermined target rate of change, when the downshift start is detected, a predetermined time is detected. Only after holding the operating oil pressure of the high speed gear side friction engagement means at a predetermined value,
A shift control method for an automatic transmission for a vehicle, comprising: starting the feedback control.