JP3142171B2 - Shift control method for automatic transmission for vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control method for a vehicular automatic transmission, and more particularly to a shift control method for performing a downshift when an engine is in a power off state.

[0002]

2. Description of the Related Art An automatic transmission mounted on an automobile is provided with a number of frictional engagement means such as a hydraulic multi-plate clutch and a hydraulic brake. Is changed by the controller, the shift change of the automatic transmission is performed.

For example, when downshifting the automatic transmission from the second speed to the first speed, the controller releases the engagement of a clutch for establishing the second speed (hereinafter referred to as a disengagement clutch) in accordance with a predetermined program. And a clutch that establishes the first speed (hereinafter, referred to as an engagement side clutch)
And the rotational speed Nt of the transmission input shaft
Is increased so that the rate of change (Nt) 'becomes equal to the rate of change of the target rotational speed, and a so-called clutch re-grip operation is performed.

In this case, when the accelerator pedal in the driver's seat is not depressed and the engine is in a so-called power-off state, the input shaft rotation speed Nt does not increase. Therefore, when the power-off state of the engine is detected, the controller starts the rapid release of the engagement of the release-side clutch, and then gradually increases the engagement of the engagement-side clutch to reduce the rotation speed Nt of the input shaft to the target rotation speed Nt. Increase along the speed change rate. After the rotational speed Nt has reached the synchronous rotational speed N ₁ of the first speed, the controller, the coupling clutch is fully coupled, had conducted downshift.

[0005]

However, in the downshift operation in the power-off state according to the above-described conventional shift control method, after the sudden release of the engagement of the disengagement side clutch is started, the engagement side clutch is gradually moved. Since the clutches are engaged, these clutches may be in a state where both clutches are released. In this case, there is a problem that the output shaft torque becomes substantially zero, the power train is in a neutral state, and the occupant has a feeling of idle running, and the shift feeling deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an automatic transmission for a vehicle which is designed to prevent a feeling of idle running during a downshift and improve a shift feeling. It is an object to provide a shift control method.

[0007]

According to the present invention, in order to achieve the above object, the engagement of the high-speed-stage frictional engagement means is released.
In a shift control method for an automatic transmission for a vehicle, in which the rotational speed of the input shaft is increased by engaging the low-speed-stage-side frictional engagement means , a downshift is performed .
At the time of execution, when the rotation speed of the input shaft decreases by a predetermined amount due to the disengagement of the high-speed side frictional engagement means , the engagement of the high-speed side frictional engagement means is feedback-controlled to reduce the rotation speed of the input shaft. Is to suppress.

[0008]

When [action] downshift when the driving state of the engine is in a power-off state Ru is implemented, the actual of the downshift
The lower speed side frictional engagement means is not engaged
In this state, the engagement of the high-speed-stage-side friction engagement means may be completely released, and the rotation speed of the input shaft may decrease. But
Reluctant, according to the speed change control method according to the present invention, when the rotation speed of the input shaft is reduced a predetermined amount, the engagement of high gear speed side frictional engagement means
The input shaft is feedback-controlled , and the input shaft is again coupled to the output shaft via the high-speed-stage-side friction engagement means.
Thus, a decrease in the rotation speed of the input shaft is suppressed . And low
Until the speed-stage friction engagement means starts engagement, the input
Good around the rotation speed where the shaft rotation speed has decreased by the specified amount.
It is held in. As a result, power down
At the time of shifting, the output shaft torque does not become almost 0,
The train never goes neutral
And the occupant is prevented from feeling idle.
You.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail 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 denotes an internal combustion engine, and the output of the engine 1 is transmitted to driving wheels (not shown) via an automatic transmission 2.

The automatic transmission 2 includes 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 of four forward steps and one reverse step, and a number of shift friction engagement means for shifting gears by switching the gear ratio of the gear train. The speed change 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, in which a first drive gear 31 and a second drive gear 32 are rotatably arranged around an input shaft 3a. The input shaft 3a between the first drive gear 31 and the second drive gear 32 has
Hydraulic clutches 33 and 34 are fixedly provided as speed change friction engagement means. The drive gears 31 and 32 rotate integrally with the input shaft 3a by engaging with the clutches 33 and 34, respectively.

An intermediate transmission shaft 35 arranged in parallel with the input shaft 3a is connected to a drive axle via a final reduction gear unit (not shown). A first driven gear 36 and a second driven gear 37 are fixed to the intermediate transmission shaft 35, and the driven gears 36 and 37 are engaged with the driving 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 is controlled by 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. When the clutch 34 and the second drive gear 32 are engaged, the rotation of the input shaft 3a is controlled by the clutch 34, the second drive gear 32,
The second driven gear 37 is transmitted to the intermediate transmission shaft 35, whereby, for example, the second speed is established.

From the state in which the first speed clutch 33 is engaged, the second
By engaging the high speed clutch 34, the automatic transmission 2
Shifts up from the first speed to the second speed. Conversely, by disengaging the clutch 34 from the state in which the clutch 34 is engaged and engaging the clutch 33,
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 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, being pressed by the return spring 53,
When the piston 52 moves backward while discharging the hydraulic oil into the oil passage 14 via the port 51, the friction engagement between the friction engagement plates 50 is released.

In order to completely disengage the clutch 33, each friction engagement plate 50 may be made to wait at the standby position. At the standby position, a predetermined clearance that is structurally required is provided between the friction engagement plates 50. For this reason, when the clutch 33 is engaged, first, each friction engagement plate 50 is moved by an invalid stroke to a position where the above-described clearance is substantially zero, that is, a position immediately before frictional engagement occurs. It is necessary to perform a filling operation.
Therefore, the backlash operation requires a backlash time.

Note that the clutch 34 is also
And a predetermined play time is required. The hydraulic circuit 5 has a duty solenoid valve (hereinafter simply referred to as a solenoid valve) corresponding to each of the above-described transmission friction engagement means, and each of the transmission friction engagement means, that is, each clutch and brake. Operate independently of each other.
In addition, since each solenoid valve operates each clutch and brake in the same manner, the solenoid valve 11 that operates the clutch 33 will be described with reference to FIG. 4, and the description of the other solenoid valves will be omitted.

FIG. 4 shows a part of the hydraulic circuit 5, which is provided 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 regulating valve (not shown) and the like are interposed in the middle of the first oil passage 13, and an operating oil pressure (line pressure) adjusted to a predetermined pressure is supplied.

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

The solenoid valve 11 is electrically connected to a controller 40, which controls the duty ratio at a predetermined cycle, for example, at a control cycle of 50 Hz. 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 the second port 11b, and the second port 1
1b communicates with the third port 11c. On the other hand, when the solenoid 11e is energized, the valve 11f
Lift against the spring force of the return spring 11g,
The first port 11a and the second port 11b are communicated, and the second port 11b and the third port 11c are shut off.

The controller 40 includes a ROM (not shown),
It contains a storage device such as a RAM, a central processing unit, an input / output device, a counter used as a timer, and the like. 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), and the like are electrically connected.

The Nt sensor 21 is a turbine rotational speed sensor that detects the rotational speed Nt of the turbine of the torque converter 4 (ie, the input shaft of the gear transmission 3). The No sensor 22 is a transfer drive gear rotation speed sensor that detects the rotation speed No of a transfer drive gear (not shown). The controller 40
The vehicle speed V can be calculated based on the rotation speed No. The .theta.t sensor 23 is a throttle valve opening sensor for detecting a valve opening .theta.t of a throttle valve arranged in the middle of an 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 a select lever (not shown) provided in the driver's seat. Each of these sensors 21 to 24 supplies a detection signal to the controller 40 every predetermined time period.

The controller 40 performs a shift change of the automatic transmission 2 according to a program 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 a gear suitable for the running state of the vehicle based on these signals. And, for example,
When the controller 40 recognizes the necessity of the downshift from the second speed to the first speed in the power-off state based on the vehicle speed V and the throttle valve opening θt, the controller 40 connects the second speed side (disengagement side) clutch 34 and the first speed An operation for gripping the high speed (coupling side) clutch 33 is performed.

FIG. 5 shows a control procedure of the downshift in the power-off state. When the controller 40 recognizes the necessity of the downshift from the second speed to the first speed in the power-off state, the controller 40 repeats this procedure. Execute.
First, in step S60 of FIG.
The turbine rotation speed Nt is determined whether or not synchronized with the rotation speed N ₁ first-speed synchronous. Specifically, when the difference between the turbine rotation speed Nt and the first-speed synchronization rotation speed N ₁ becomes smaller than a predetermined rotation speed (for example, 50 rpm), the controller 40 causes the turbine rotation speed Nt and the first-speed synchronization rotation speed N Detects that synchronization with ₁ has been completed. Now, since the controller 40 immediately recognizes the necessity of the downshift, the turbine rotation speed Nt and the first-speed synchronous rotation speed N ₁
Is not synchronized. Therefore, the determination condition in step S60 is negative, and the controller 40 proceeds to step S62.

In step S62, the determination condition (Nt> N
₂ + ΔNs ₂ ), the second of the turbine rotation speed Nt
Fast to detect the synchronization deviation from the synchronous rotational speed N _2. That is, when the turbine rotation speed Nt becomes higher than the rotation speed obtained by adding the predetermined rotation speed ΔNs ₂ (for example, 50 rpm) to the second speed synchronization rotation speed N ₂ , the controller 40 detects the loss of synchronization. As described above, the controller 40
Immediately after recognizing the necessity of the downshift, the determination condition is negative, and the controller 40 proceeds to step S6.
Proceed to 4.

In step S64, the controller 40
Performs the pre-synchronization operation of the clutches 33 and 34. This will be specifically described. At time a in FIG. 7, when the controller 40 recognizes the necessity of the downshift from the second speed to the first speed in the power-off state, the controller 40
First, the duty ratio of a solenoid valve (hereinafter, referred to as a release-side solenoid valve) that supplies the operating oil pressure to 4 is set to 0%, and after a lapse of a predetermined time, to a predetermined duty ratio.
Accordingly, as shown in FIG. 7, the operating oil pressure of the release-side clutch 34 is kept at a predetermined pressure value after abruptly decreasing, whereby the release-side clutch 34 is brought into a standby state after the engagement is rapidly released. Held in position.

When the disengagement of the disengagement side clutch 34 is completed, a solenoid valve (hereinafter, referred to as a connection side solenoid valve) 11 for supplying hydraulic pressure to the connection side clutch 33 is provided.
Is driven for a predetermined time at a duty ratio of 100% to perform a rattling operation of the clutch 33. After the rattling operation is completed at the time point c in FIG. The feedback control of the duty ratio of the coupling side solenoid valve 11 is performed so that the coupling side clutch 33 is gradually coupled to increase the turbine rotational speed Nt so as to be equal to the change rate. Then, while repeatedly executing the routine waits for the turbine rotational speed Nt is disengaging from the second-speed synchronous speed N _2.

At this time, when a state occurs in which both clutches 33 and 34 are both disengaged, the turbine rotational speed Nt decreases as shown by a two-dot chain line in FIG. In this embodiment, the occurrence of the reverse slip phenomenon is prevented by executing the routine of FIG. 6 described later. When the turbine rotation speed Nt is
When it is detected that the off-speed synchronous speed N ₂ (d point), i.e., the determination condition is satisfied in step S62, the controller 40, the release-side solenoid valve duty ratio 0% release side clutch is set to 34 Is completely released (step S66), and the above-described feedback control is continued to gradually engage the engagement side clutch 33. Thereby, the turbine rotation speed Nt increases along the predetermined target change rate.

[0028] When the turbine speed Nt is controller 40 that is synchronized with the first-speed synchronous speed N ₁ is detected (in FIG. 7 e point), the determination conditions step S60 is affirmative, the controller 40 Step S70
Then, the duty ratio of the release side solenoid valve is set to 0%, the engagement of the release side clutch 34 is completely released, and the duty ratio of the connection side solenoid valve 11 is set to 100%.
% And the coupling side clutch 33 is completely engaged.
Thereafter, this routine ends, and the downshift from the second speed to the first speed in the power-off state is completed.

On the other hand, as described above, when the clutches 33 and 34 are both disengaged and a reverse slip phenomenon occurs during the downshift from the second speed to the first speed in the power-off state, as described above. The controller 40 executes the routine of FIG. 6 to suppress the decrease in the turbine rotation speed Nt. That is, when recognizing the necessity of the downshift in the power-off state, the controller 40 repeatedly executes the routine of FIG. 6 to monitor the occurrence of the reverse slip phenomenon, similarly to the routine of FIG.

In step S80 of FIG. 6, as in step S62 of FIG. 5, the turbine rotational speed Nt is out of synchronization with the _second synchronous rotational speed N2 based on the determination condition (Nt> N ₂ + ΔNs ₂ ). Is detected. Immediately after the controller 40 recognizes the necessity of the downshift, this determination condition is negative, and therefore, the controller 40 determines in step S
Go to 82.

In step S82, the controller 40 determines whether or not the flag FLG has already been set to the value "1". In the first execution of this routine, the flag FLG has been reset, and the controller 40 determines in step S8
Proceed to 4. In step S84, the determination condition (Nt <N ₂₎
−ΔNs ₁ ) to detect the occurrence of the reverse slip phenomenon. That is, the rotation speed is smaller than the rotation speed obtained by subtracting the predetermined rotation speed ΔNs ₁ (for example, 50 rpm) from the second speed synchronization rotation speed N ₂ .
When the turbine rotation speed Nt decreases, the controller 4
0 detects occurrence of the reverse slip phenomenon. Controller 4
Immediately after 0 recognizes the necessity of a downshift, this determination condition is negative, and therefore, the controller 40 proceeds to step S86 and sets the flag FLG to a value of 0.
This routine ends.

On the other hand, as described above, the turbine rotational speed N
When t decreases and the determination condition of step S84 becomes affirmative (time b in FIG. 7), the controller 40 proceeds to step S9.
0, S92 is executed to perform feedback control of the release side solenoid valve. More specifically, step S90
Then, the turbine rotation speed Nt is changed to the rotation speed (N ₂ −ΔN
Determine the duty factor D of the release solenoid valve, which can be equal to s ₁ ). The controller 40 calculates, for example, a deviation ΔN between the rotation speed Nt and (N ₂ −ΔNs ₁ ), and determines a duty ratio D according to the deviation ΔN. The method of determining the duty ratio D is not particularly limited, and may be set by a conventionally known PID method.
Then, in step S92, the release-side solenoid valve is driven at the duty ratio D. As a result, the turbine rotation speed Nt is maintained near the rotation speed (N ₂ −ΔNs ₁ ), and the output shaft torque is prevented from becoming zero as shown by the two-dot chain line in FIG.

Thereafter, the controller 40 proceeds to step S
Proceeding to 94, the value FLG is set to 1 and the routine ends. Then, in the next execution of this routine,
Since the value of the flag FLG is set to 1, the controller 40 proceeds from step S82 to step S90, and performs the above-described feedback control of the release-side solenoid valve. This feedback control is continued in a section from time point b to time point d in FIG.

On the other hand, when the engagement of the coupling side clutch 33 is actually started at the time point c in the drawing, the turbine rotational speed Nt starts to increase. If the rotation speed Nt becomes larger than (N ₂ + ΔNs ₂ ) at the time point d in the figure, the determination condition in step S80 becomes affirmative, and the controller 40 proceeds to step S86 to reset the flag FLG, and then executes this routine. Terminates execution of.

Further, after the time point d in the figure, the turbine rotation speed Nt increases along the predetermined target change rate, so that the determination condition in step S80 is always affirmative. until the downshift by detecting the synchronization completion of the first-speed rotation speed N ₁ is finished, the controller 40 remains in repeatedly executed step S86.

In this embodiment, the downshift control from the second speed to the first speed in the power-off state has been described. However, the downshift mode is changed to the downshift from the second speed to the first speed. Of course, it is not limited.

[0037]

According to the present invention as described above, according to the present invention, Pas
At the time of downshift in the power-off state, when the rotation speed of the input shaft decreases by a predetermined amount , the engagement of the high-speed-stage-side friction engagement means is feedback-controlled, and the input shaft is again turned on.
Since coupled to form the output shaft side are to suppress so a reduction in the rotational speed of the input shaft, the power train without substantially zero output shaft torque during the downshift in the power OFF state
Is prevented from being in a neutral state, so that the occupant can be prevented from having a so-called idling feeling, and the shift feeling can be improved.

[Brief description of the 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 shown in FIG. 1;

FIG. 3 is a sectional view showing the clutch of FIG. 2;

FIG. 4 is a schematic configuration diagram showing a part of a hydraulic circuit that operates the clutch shown in FIGS. 2 and 3;

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

FIG. 6 is a flowchart showing a control procedure of a reverse slip phenomenon prevention routine executed by the controller shown in FIGS. 1 and 4;

FIG. 7 is a diagram showing a relationship between a turbine rotation speed Nt and a change in an operating oil pressure of each clutch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Gear transmission 5 Hydraulic circuit 11 Solenoid valve 33 2nd speed side clutch 34 3rd speed side clutch 40 Controller

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-190661 (JP, A) JP-A-63-214550 (JP, A) JP-A-2-46362 (JP, A)

Claims (1)

(57) [Claims] 1. The high speed step side frictional engagement means is disengaged ,
In a shift control method for an automatic transmission for a vehicle, in which a downshift is performed by increasing a rotation speed of an input shaft by engaging a low speed side frictional engagement means , when the downshift is performed, the high speed side friction is reduced. Engaging hands
When the rotation speed of the input shaft with the disengagement of the stage is reduced a predetermined amount, said feedback control of the engagement of high gear speed side frictional engagement device, which comprises suppressing the decrease in the rotational speed of the input shaft A shift control method for an automatic transmission for a vehicle.