JPH11223263A - Lock-up controller for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent useless early releasing while preventing an engine stall by releasing a lock-up clutch without delay during speed reduction. SOLUTION: A reduction speed ΔVSP is calculated as the changing amount of a car speed VSP (S1), and when the car speed VSP is higher, a reference reduction speed ΔVSPth is set larger (S2). When the reduction speed ΔVSP exceeds the reference reduction speed ΔVSPth (S3), a lock-up clutch is forcibly released (S4). The reference reduction speed ΔVSPth may be set according to the slip rate of the lock-up clutch or the transmission ratio of a transmission other than the car speed VSP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lock-up control device for an automatic transmission, and more particularly to a technique for avoiding engine stall during deceleration from a lock-up (directly connected) state.

[0002]

2. Description of the Related Art Conventionally, in an automatic transmission in which a torque converter is provided with a lock-up clutch, when decelerating from a lock-up state by the lock-up clutch, a control based on a steady characteristic according to a normal vehicle speed or the like is performed. Lock-up release may be delayed, leading to engine stall (hereinafter abbreviated as engine stall) .Therefore, there is a device provided with a means for forcibly releasing the lock-up state when the deceleration exceeds a certain value. (Japanese Unexamined Patent Application Publication No.
7950, JP-A-57-192668, etc.).

[0003]

However, in the conventional device, since the determination value of the deceleration for releasing the lock-up is a fixed value, the lock-up is released unnecessarily and quickly depending on the state of the vehicle. Conversely, there is a possibility that the lock-up release is delayed and the engine stall occurs because the release according to the deceleration does not function effectively.

For example, if the determination value of the deceleration is set in accordance with the deceleration from the low vehicle speed side, the lockup is released too early at the time of deceleration from the high vehicle speed side, and the lockup area is narrowed. Conversely, if the deceleration is set to match the deceleration from the high vehicle speed side, the lockup release is delayed at the time of deceleration from the low vehicle speed side, and the possibility of engine stall occurs, and the lockup occurs in all vehicle speed ranges. Cannot be properly released.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a lock-up control in accordance with deceleration so as to prevent an unnecessary stall of lock-up while avoiding occurrence of engine stall. Aim.

[0006]

According to the present invention, an input shaft and an output shaft of a torque converter interposed between an output shaft of an engine and an input shaft of a transmission are mechanically arranged. This is a lockup control device for an automatic transmission having a directly connected lockup clutch, and is configured as shown in FIG.

In FIG. 1, the deceleration detecting means detects the deceleration of the vehicle, and the reference deceleration setting means variably sets the reference deceleration according to the state of the vehicle. Then, the deceleration lock-up control means forcibly reduces the engagement force in the lock-up clutch when the deceleration becomes larger than the reference deceleration.

According to this configuration, the deceleration for forcibly reducing the engagement force of the lock-up clutch is not fixed, but is variably set in accordance with the state of the vehicle at that time. To perform the forcible decrease control of the fastening force. When the lock-up clutch is driven by hydraulic pressure to perform the engagement / disengagement operation, the control for decreasing the supply hydraulic pressure corresponds to the control for decreasing the engagement force. , The clutch is completely released, and a predetermined slip state is set.

According to a second aspect of the present invention, the deceleration-time lock-up control means brings the lock-up clutch into a completely released state. According to this configuration, when the deceleration becomes larger than the reference deceleration corresponding to the state of the vehicle, the lock-up clutch is completely released, and both the lock-up state (direct connection) and the slip lock-up state are released.

According to a third aspect of the present invention, the deceleration lock-up control means reduces the engagement force of the lock-up clutch to a predetermined engagement force. According to this configuration, when the deceleration becomes larger than the reference deceleration corresponding to the state of the vehicle, the deceleration is reduced to a predetermined fastening force lower than the previous fastening force. Here, the control for reducing the fastening force to a predetermined value includes a control for shifting from a complete lock-up state (completely directly connected) to a slip lock-up state, and a control for shifting the slip lock-up state to a state with a higher slip ratio. Shall be included.

According to a fourth aspect of the present invention, the reference deceleration setting means is configured to variably set the reference deceleration according to a vehicle speed as a state of the vehicle. According to this configuration, a different reference deceleration is set depending on whether the vehicle is decelerating from a high vehicle speed side or a low vehicle speed side. Specifically, the control is performed such that the reference deceleration is set to be larger at the higher vehicle speed side, and the deceleration from the lower vehicle speed side is reduced from the deceleration lower than at the time of deceleration from the higher vehicle speed side. It is good to be performed.

According to a fifth aspect of the present invention, the reference deceleration setting means variably sets the reference deceleration according to a slip ratio of the lock-up clutch as a vehicle state. According to this configuration, a different reference deceleration is set according to the slip ratio of the lock-up clutch. Specifically, since the engine brake does not act as the slip rate increases, the reference deceleration is set to be greater as the slip rate increases, so that the slip rate is small (complete when the slip rate = 0). At the time of deceleration from the direct connection state), it is preferable to perform control to decrease the fastening force from a lower deceleration than at the time of deceleration from a state where the slip ratio is large.

[0013] According to a sixth aspect of the present invention, the reference deceleration setting means is configured to variably set the reference deceleration according to a speed ratio of the transmission as a vehicle state. According to such a configuration, a different reference deceleration is set according to the speed ratio of the transmission. Specifically, the control is performed such that the reference deceleration is set to be larger on the high gear side, and when the vehicle is decelerated from the low gear side, the fastening force is reduced from a lower deceleration than when the vehicle is decelerated from the high gear side. It is good to do.

The transmission includes a continuously variable transmission in addition to a gear type stepped transmission.

[0015]

According to the first aspect of the present invention, the control for reducing the engagement force of the lock-up clutch for preventing engine stall can be performed at an appropriate deceleration for each state of the vehicle. There is an effect that the lock-up region can be widened and the fuel consumption performance and the like can be improved while avoiding occurrence of engine stall.

According to the second aspect of the invention, the lock-up clutch is completely released at the reference deceleration set for each state of the vehicle, so that the lock-up clutch is released prior to the release control based on normal steady-state characteristics. Is released, so that the engine stall due to the release delay can be reliably prevented. According to the third aspect of the present invention, the engagement force of the lock-up clutch is reduced to a predetermined value at the reference deceleration set for each state of the vehicle. There is an effect that can be avoided.

According to the present invention, it is possible to prevent the fastening force of the lock-up clutch from being weakened unnecessarily quickly at the time of deceleration from the high vehicle speed side, and to decrease the fastening force at the time of deceleration from the low vehicle speed side. There is an effect that it is possible to prevent the engine from stalling with a delay. According to the fifth aspect of the invention, in the slip lock-up state of the lock-up clutch, when the engine stall resistance is high, it is possible to avoid performing a control to weaken the fastening force unnecessarily and quickly, and to achieve the complete lock-up state. In a state close to, there is an effect that generation of engine stall due to control delay can be prevented.

According to the sixth aspect of the invention, it is possible to prevent the control for weakening the fastening force from being performed needlessly and quickly on the high gear side having high engine stall resistance, and to prevent the occurrence of engine stall due to control delay on the low gear side. effective.

[0019]

Embodiments of the present invention will be described below. FIG. 2 is a system configuration diagram of a vehicle drive system according to the embodiment. An automatic transmission 2 is connected to an output side of an engine 1 mounted on a vehicle (not shown). The automatic transmission 2 includes a torque converter 3 disposed on the output side of the engine 1, a gear transmission 4 connected via the torque converter 3, and transmitting the engine output torque via the torque converter 3. Speed change control for engaging and disengaging various friction elements (front clutch, rear clutch, brake band, lock-up clutch, etc.)
A solenoid valve group 5 for lock-up control, line pressure control, and the like. The solenoid valve group 5 includes:
It is composed of a lock-up solenoid, a shift solenoid A, a shift solenoid B, a line pressure solenoid, and the like.

The gear type transmission 4 may be replaced with a continuously variable transmission. Signals from various sensors are input to the automatic transmission control unit 6 that controls the solenoid valve group 5. As the various sensors,
A potentiometer-type throttle sensor 8 is provided in the intake system of the engine 1 and detects an opening TVO of a throttle valve 7 interlocked with an accelerator pedal (not shown). The output shaft of the automatic transmission 2 is provided with a vehicle speed sensor 9 that emits a pulse signal at every predetermined rotation angle of the output shaft. Further, an engine rotation sensor 10 (crank angle sensor) for detecting the rotation speed of the engine 1 is provided.

The control unit 6 for the automatic transmission comprises:
Based on the operation position signal of the select lever operated by the driver, for example, in a state where the select lever is in the drive range (D range), a map of a preset shift pattern is referred to and according to the throttle valve opening TVO and the vehicle speed VSP. Automatic shift control for automatically setting the first to fourth speed shift positions and controlling the gear type transmission 4 to the shift positions via the solenoid valve group 5 is performed.

The torque converter 3 has a structure shown in FIG.
A lock-up clutch 40 as shown in FIG. 1 is provided, and the input shaft and the output shaft of the torque converter 3 can be mechanically directly connected by the lock-up clutch 40. In FIG. 3, a lock-up plate 49 (hydraulic clutch) having a clutch facing 48 is provided integrally with the torsion damper 50, facing the inner wall 42a of the drive shaft 41 side portion of the case 42. The clutch hub 51 is spline-fitted, and the clutch hub 51 is spline-fitted to the driven shaft 44.

As a result, the lock-up plate 49 can move in the axial direction of the driven shaft 54, and the pressures P1, P of the pressure chambers 52, 53 formed on both sides of the lock-up plate 49.
Move according to 2. The pressure chamber 52 has a pressure passage 54b.
, A converter oil pressure (operating oil pressure) is supplied to the pressure chamber 53, and a converter oil pressure is supplied to the pressure chamber 53 via a pressure passage 54a.

Here, when P1> P2, the lock-up plate 49 moves leftward in FIG.
a, and a lock-up state (a clutch directly connected state) is established in which the drive shaft 41 and the driven shaft 54 are mechanically connected to each other, and when P2> P1, the lock-up plate 49 moves rightward in the figure. Then, the case 42 is separated from the inner wall 42a of the case 42 to be in a released state (torque converter state). Here, the supply of the converter oil pressure (operating oil pressure) to the pressure chambers 52, 53 via the hydraulic passages 54b, 54a is controlled by a lock-up solenoid 55 in the solenoid valve group 5. .

That is, by controlling the lock-up solenoid 55, the operation of the lock-up control valve 56 is controlled, and the converter hydraulic circuit connected to the lock-up control valve 56 is connected to the lock-up plate 49.
Is switched between the release side and the engagement side. Here, the duty of the lock-up solenoid 55 is controlled by the control unit 6,
When the OFF time is long, the converter oil pressure supplied from the oil pump 57 acts on the pressure chamber 53, and furthermore, the pressure chamber 53
Flows from the pressure chamber 52 into the pressure chamber 52, so that P2> P1 and the lockup is released (released state).
If the OFF time is short, the converter oil pressure
P1> P2, and the lock-up plate 49 is pressed against the inner wall 42a of the case 42 to be in a fastened state.
Further, the converter oil pressure P2 acting on the pressure chamber 53 is appropriately reduced based on the OFF time ratio, so that a half-clutch state (slip lock state) can be achieved.

The drive shaft 41 is connected to the output shaft of the engine 1, and the driven shaft 44 is connected to the input shaft of the gear transmission 4. The control unit 6 for the automatic transmission controls the throttle valve opening T
The engagement state of the lock-up clutch 40 is controlled through control of a lock-up solenoid with reference to a lock-up control map set in advance according to the VO and the vehicle speed VSP.

Further, in the present embodiment, the lock-up control according to the deceleration of the vehicle is performed prior to the lock-up control based on the lock-up control map. The flowchart of FIG. 4 shows a first embodiment of the lock-up control according to the deceleration of the vehicle. First, in S1 (deceleration detecting means), the deceleration of the vehicle is determined per unit time. Change amount ΔV of vehicle speed VSP
SP (ΔVSP = VSP before unit time-latest VSP)
Is calculated as ΔVSP = VSP before unit time−
Since the calculation is performed as the latest VSP, the ΔVSP is calculated as a positive value during deceleration and is calculated as a negative value during acceleration. The larger the ΔVSP, the greater the deceleration.

In S2 (reference deceleration setting means), the vehicle speed V
The reference deceleration ΔVSPth (> 0) is variably set according to the SP. Specifically, as shown in the figure, the higher the vehicle speed VSP is, the larger the value is set as the reference deceleration ΔVSPth. In S3, the deceleration ΔVSP calculated in S1 is compared with the reference deceleration ΔVSPth set in S2 according to the vehicle speed VSP.

Here, the deceleration ΔVSP is equal to the reference deceleration ΔV
When it is larger than SPth, that is, the reference deceleration ΔVSPth
When the vehicle speed is sharply reduced, the process proceeds to S4 (lock-up control means during deceleration). At this time, when the lock-up clutch 40 is controlled to the lock-up state (the clutch directly connected state) or the slip lock state, Forcibly control to release state. Specifically, the ON duty of the duty signal to be output to the lock-up solenoid 55 is forcibly changed to 0 (or the minimum value).

The control from the lockup state or the slip lockup state to the release state corresponds to controlling the engagement force of the lockup clutch 40 from a certain engagement force (> 0) to zero. The lock-up clutch 40 is released according to the lock-up control map if the vehicle speed decreases with deceleration.
If release control is performed after the vehicle speed falls below the judgment value,
Since there is a possibility that the release of the lock-up clutch 40 is delayed and the engine stalls, the lock-up clutch 40 is released at the time of sudden deceleration without waiting for a decrease in the vehicle speed to avoid the occurrence of engine stall.

Further, if the reference deceleration ΔVSPth for forcibly releasing the vehicle is set variably according to the vehicle speed VSP, the lock-up clutch 40 is released unnecessarily and quickly at the time of deceleration from a high vehicle speed where it is difficult to stall. Can be avoided, and when decelerating from a low vehicle speed where
The lock-up clutch 40 can be released early so that the engine stall can be avoided.

FIG. 5 is a flow chart showing a second embodiment of the lock-up control according to the deceleration of the vehicle. In S11, the deceleration ΔV is determined in the same manner as in S1.
Calculate SP. In S12, the reference deceleration ΔVSPth is variably set according to the slip ratio of the lock-up clutch 40. Specifically, as shown in the figure, the higher the slip ratio (the lower the fastening force), the more the reference deceleration ΔVS
A large value is set as Pth. The slip ratio can be obtained from the engine speed Ne and the turbine speed. The turbine speed can be calculated from the vehicle speed VSP and the gear ratio when no turbine sensor is provided.

At S13, the deceleration ΔVSP calculated at S11 is compared with the reference deceleration ΔVSPth set at S12 according to the slip ratio. If the deceleration .DELTA.VSP is larger than the reference deceleration .DELTA.VSPth, the process proceeds to S14 (lock-up control means for deceleration) and S4
Similarly, the lock-up clutch 40 is forcibly controlled to the released state.

When the slip rate of the lock-up clutch 40 is high, it is difficult to cause the engine to stall. Therefore, the forcible release control is not performed until a relatively large deceleration is reached, so that the lock-up region is enlarged and the slip rate is low. Sometimes (including the complete lockup state) it is easy to stall,
Forcible release control is performed from a relatively small deceleration to reliably prevent engine stall.

FIG. 6 is a flow chart showing a third embodiment of the lock-up control according to the deceleration of the vehicle. In S21, the deceleration ΔV is determined in the same manner as in S1.
Calculate SP. In S22, the reference deceleration ΔVSPth is variably set in accordance with the speed (gear ratio) of the gear transmission 4. Specifically, as shown in the figure, a larger value is set as the reference deceleration ΔVSPth toward the higher gear.
When the transmission 4 is a continuously variable transmission, as shown in FIG. 7, the reference deceleration ΔV is set according to the speed ratio at that time.
SPth may be set.

In step S23, the deceleration ΔVSP calculated in step S21 is compared with the reference deceleration ΔVSPth set in step S22 according to the shift speed (gear ratio). here,
If the deceleration ΔVSP is larger than the reference deceleration ΔVSPth, the process proceeds to S24 (lock-up control means during deceleration),
Similarly to S4, the lock-up clutch 40 is forcibly controlled to the released state.

Since it is difficult to stall when the gear is on the high gear side, the forced release control is not performed until a relatively large deceleration is achieved, thereby enlarging the lock-up area and causing the engine to stall easily on the low gear side. The forced release control is performed from a very small deceleration to reliably prevent the occurrence of engine stall. Note that the reference deceleration ΔVSPth may be determined by combining a plurality of parameters (vehicle speed, slip ratio, gear ratio) indicating the state of the vehicle for determining the reference deceleration ΔVSPth shown in FIGS. .

In the embodiment shown in FIGS. 4 to 6, when the deceleration .DELTA.VSP exceeds the reference deceleration .DELTA.VSPth, the lock-up clutch 40 is completely released. Instead of causing the engine to stall, a transition may be made to a predetermined fastening force state (predetermined slip lock state) in a low range where the engine stall can be avoided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the invention according to claim 1;

FIG. 2 is a system configuration diagram of a vehicle drive system according to the embodiment.

FIG. 3 is a sectional view showing the lock-up clutch in the embodiment in detail.

FIG. 4 is a flowchart showing a first embodiment of lockup control during deceleration.

FIG. 5 is a flowchart showing a second embodiment of the lockup control during deceleration.

FIG. 6 is a flowchart showing a third embodiment of the lockup control during deceleration.

FIG. 7 is a diagram showing control characteristics when a continuously variable transmission is provided.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Torque converter 4 Gear type transmission 5 Solenoid valve group 6 Control unit for automatic transmission 7 Throttle valve 8 Throttle sensor 9 Vehicle speed sensor 10 Engine rotation sensor

Claims (6)

[Claims] A lock-up control for an automatic transmission including a lock-up clutch mechanically directly connecting an input shaft and an output shaft of a torque converter interposed between an output shaft of an engine and an input shaft of a transmission. A deceleration detecting means for detecting a deceleration of the vehicle; a reference deceleration setting means for variably setting a reference deceleration according to a state of the vehicle; and the deceleration is larger than the reference deceleration. And a deceleration lock-up control means for forcibly reducing the engagement force of the lock-up clutch when the lock-up clutch is turned off. 2. A lock-up control device for an automatic transmission according to claim 1, wherein said deceleration lock-up control means brings said lock-up clutch into a completely released state. 3. The lock-up control device for an automatic transmission according to claim 1, wherein said deceleration lock-up control means reduces a lock-up clutch engagement force to a preset engagement force. 4. The apparatus according to claim 1, wherein said reference deceleration setting means variably sets said reference deceleration according to a vehicle speed as a state of the vehicle. Lock-up control device for automatic transmission. 5. The reference deceleration setting means according to claim 1, wherein said reference deceleration setting means variably sets said reference deceleration according to a slip ratio of said lock-up clutch as a vehicle state. A lock-up control device for an automatic transmission according to any one of the preceding claims. 6. The apparatus according to claim 1, wherein said reference deceleration setting means variably sets the reference deceleration according to a speed ratio of the transmission as a state of the vehicle. A lock-up control device for an automatic transmission according to claim 1.