JP2004322856A - Lockup controller for automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lockup controller capable of directly coupling a lockup clutch while suppressing shocks even deceleration of a vehicle is started, ensuring excellent drivability, increasing the chances of fuel cut, and enhancing the fuel economy. <P>SOLUTION: When deceleration of a vehicle is started with a torque converter in a non-direct coupling state, coupling of a lockup clutch is started to change the torque converter in a direct-coupling state. The throttle opening θth of an engine is reduced by a predetermined rate of change, and sudden reduction of engine speed Ne is suppressed before the direct coupling is completed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lock-up control device for an automatic transmission, and more particularly, to a control device for controlling a lock-up clutch of a torque converter when a vehicle is decelerated.
[0002]
[Related background art]
Conventionally, when the vehicle accelerates or runs at a constant speed, the lock-up clutch provided in the automatic transmission directly connects the torque converter, and lock-up control is implemented to prevent power loss and fuel consumption reduction due to slippage of the torque converter The lock-up control is also used when the vehicle is decelerating, and the direct rotation of the torque converter uses the driving force from the driving wheels to maintain the engine rotation speed in the fuel cut range, thereby controlling the fuel on the engine side. The cut period is extended to improve fuel efficiency.
[0003]
The lock-up control during vehicle deceleration requires that the lock-up clutch be directly engaged before the start of deceleration, and avoids the occurrence of shock when directly engaged after the sudden decrease in engine speed due to the accelerator closing operation. I have. For this reason, for example, when deceleration is started immediately after a gear shift or after a slightly stronger acceleration, the lock-up control is not performed, and the effect of improving fuel efficiency cannot be obtained.
[0004]
On the other hand, due to a delay in the response of the hydraulic pressure of the lock-up clutch, the engine rotational speed may suddenly decrease before the clutch engagement force is generated, and a shock may be generated at the time of direct connection. Reference 1).
In the lock-up control device described in Patent Document 1, a target throttle opening is set based on the turbine rotation speed at the time when the accelerator is closed to decelerate, and the throttle is fully closed based on the accelerator closing operation. The valve is maintained at the target throttle opening for a predetermined time, thereby suppressing a sudden decrease in the engine rotation speed and preventing a shock at the time of direct connection.
[0005]
[Patent Document 1]
JP-A-2002-144920 (FIG. 4)
[0006]
[Problems to be solved by the invention]
In the lock-up control device described in Patent Document 1, as the turbine rotation speed at the start of deceleration is higher, the target throttle opening on the open side is set to maintain a higher engine rotation speed (see FIG. 4). However, when the lock-up clutch is directly engaged after the start of deceleration of the vehicle using the lock-up control device, the occurrence of a shock cannot be prevented in the following situation.
[0007]
That is, when shifting from rapid acceleration to deceleration, the clutch direct connection is started while the turbine rotational speed is increasing following the engine rotational speed, that is, in a state where the difference between the engine rotational speed and the turbine rotational speed is large. At this time, in the lock-up control device, a small value is set as the target throttle opening based on the rising turbine rotation speed that is still low, so that the sudden decrease in the already increased engine rotation speed cannot be suppressed. As a result, there is a possibility that the problem of shock generation at the time of direct connection cannot be sufficiently solved.
[0008]
An object of the present invention is to suppress the shock even after the start of deceleration of the vehicle and directly connect the lock-up clutch, thereby ensuring good drivability and increasing fuel cut opportunities to achieve improved fuel economy. A lock-up control device is provided.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a lockup clutch capable of mechanically directly connecting a torque converter interposed between an engine and an automatic transmission and an input side and an output side of the torque converter is provided. And a lock-up control device of an automatic transmission having a lock-up control device for controlling the lock-up clutch based on a running state of the vehicle.The lock-up control device performs an accelerator closing operation when the torque converter is not directly connected. When the deceleration of the vehicle is started, the torque converter is switched to the direct connection state by the lock-up clutch, and the throttle valve provided in the intake passage of the engine is gradually changed at a predetermined rate from the throttle opening at the start of deceleration. Is controlled to the closing side.
[0010]
Therefore, when the vehicle starts to decelerate in response to the accelerator closing operation in the non-direct connection state of the torque converter, the torque converter is switched to the direct connection state by the lock-up clutch controlled by the lock-up control means, and the engine intake passage Is controlled to be closed at a predetermined rate of change.
As a result, the decrease in the engine rotation speed becomes slower than when the throttle valve is closed in response to the accelerator operation, and even when the direct connection of the torque converter is completed, the engine rotation speed is significantly lower than the turbine rotation speed. It can be kept close to the turbine speed without any trouble. Therefore, the direct connection of the torque converter is performed in a state where the engine rotation speed and the turbine rotation speed are close to each other, and the occurrence of a shock at the time of the direct connection is suppressed. Further, even when the vehicle is decelerated in the non-direct connection state, the torque converter is directly connected, so that the opportunity for executing the fuel cut on the engine side is increased.
[0011]
Since the throttle valve is controlled to gradually close at a predetermined change rate from the throttle opening at the start of deceleration irrespective of the turbine rotation speed, for example, the vehicle shifts from rapid acceleration to deceleration and the engine speed is reduced. Even when the turbine rotational speed that follows the speed is still low, the opening is controlled to an appropriate degree without being affected by the influence, and it is possible to reliably suppress a sudden decrease in the engine rotational speed.
[0012]
According to a second aspect of the present invention, in the first aspect, there is provided direct connection determination means for determining the completion of direct connection of the torque converter, and the lock-up control means determines a predetermined change when direct connection completion of the torque converter is determined by the direct connection determination means. The throttle control based on the rate is stopped and the throttle valve is closed.
Accordingly, when it is determined that the direct connection of the torque converter is completed, the control based on the predetermined change rate is immediately stopped and the throttle valve is closed, so that the deceleration according to the accelerator closing operation is obtained.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a lockup control device embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing the lockup control device of the present embodiment. An automatic transmission 2 of a torque converter type is connected to an engine 1 mounted on a vehicle (not shown), and the output of the engine 1 is input to the automatic transmission 2 via a torque converter 3 and varies according to the gear position of the planetary gear mechanism. Is output to the drive wheels after the gear is shifted. The torque converter 3 is provided with a lock-up clutch 4 that directly connects the pump impeller 3a side and the turbine runner 3b side. The lock-up clutch 4 and a speed-changing clutch and a brake in the automatic transmission 2 are connected to an automatic transmission. 2 is controlled by various solenoids 5a in a valve body 5 provided at a lower part of the valve body 2.
[0014]
In the vehicle interior, an input / output device (not shown), a storage device (ROM, RAM, BURAM, etc.) for storing control programs, control maps, and the like, a central processing unit (CPU), and an ECU 11 (engine Control unit) and an ATCU 12 (transmission control unit).
On the input side of the ECU 11, a throttle sensor 13 for detecting a throttle opening θth of the engine 1, an accelerator sensor 14 for detecting an accelerator operation amount θAcc by a driver, a vehicle speed sensor 15 for detecting a vehicle speed V, and an engine speed Ne are detected. An engine rotation speed sensor 16 and various other switches and sensors are connected. A throttle motor 17 for opening and closing a throttle valve 7 provided in an intake passage 6 of the engine 1 is provided on the output side of the ECU 11. Fuel injection valves, spark plugs, and other devices for each cylinder are connected.
[0015]
The ECU 11 executes control for operating the engine 1, such as fuel injection control and ignition timing control, based on each piece of detection information. For example, the target throttle opening tgtθth is obtained from the accelerator operation amount θacc and the vehicle speed V according to a map (not shown), and the throttle motor 17 controls the opening of the throttle valve 7 based on the target throttle opening tgtθth and the actual throttle opening θth. On the other hand, when the vehicle decelerates, a fuel cut for stopping the fuel injection is executed.
[0016]
On the other hand, on the input side of the ATCU 12, the throttle sensor 13, the accelerator sensor 14, the vehicle speed sensor 15, the engine speed sensor 16, the turbine speed sensor 18 for detecting the speed Nt of the turbine runner 3b, and the shift selected by the driver. A shift position sensor 19 for detecting a position (N, P, D range, etc.), and various other switches and sensors are connected. On the output side of the ATCU 12, various solenoids 5a of the automatic transmission 2 and others are connected. Devices are connected.
[0017]
The ATCU 12 sets the gear position based on the throttle opening θth and the vehicle speed V according to a map (not shown), and performs the shift control by switching the engagement state of the clutch and the brake by the solenoid 5a. The lock-up clutch 4 is engaged to prevent a power loss or a decrease in fuel consumption due to the slip of the lock 3, and in a region where the throttle opening θth is less than a predetermined value, the lock-up clutch 4 is extended to extend the fuel cut period during vehicle deceleration. Engage.
[0018]
Further, when the deceleration of the vehicle is started in a state where the torque converter 3 is not directly connected, the ATCU 12 cooperates with the ECU 11 to suppress the sudden decrease in the engine speed Ne and switch the torque converter 3 to the directly connected state. Is executed, thereby increasing the chance of fuel cut on the engine 1 side. Hereinafter, the control will be described in detail.
[0019]
When the deceleration of the vehicle is started in the non-direct connection state as described above, the ATCU 12 executes the direct connection control routine shown in FIG. 2 at a predetermined control interval, and first, in step S2, the solenoid for the lock-up clutch of the automatic transmission 2 The control duty of 5a is raised (lock-up control means). As a result, the lock-up clutch 4 increases the engaging force and shifts to a directly connected state with an increase in the hydraulic pressure.
[0020]
In the following step S4, an engine rotation reduction suppression command is output to the ECU 11 side, and in step S6, it is determined whether or not the direct connection is completed (direct connection determining means). For example, the determination of the direct connection completion is made based on the difference ΔN between the engine rotation speed Ne and the turbine rotation speed Nt, and when the difference ΔN becomes smaller than a predetermined value, it is determined that the direct connection is completed.
If the direct connection has not been completed yet, a NO (negative) determination is made in step S6, and the process returns to step S4. When the direct connection is completed, a determination of YES (affirmative) is made in step S6, the process proceeds to step S8, the control duty of the solenoid 5a is reduced, and a direct connection completion command is output to the ECU 11 in step S10, and then the routine is ended. .
[0021]
On the other hand, the ECU 11 executes the rotation reduction suppression routine shown in FIG. 3 at a predetermined control interval, and first determines in step S12 whether or not an instruction to reduce the engine rotation has been input from the ATCU 12 side. When the determination is NO, the process proceeds to step S14, executes the throttle control based on the normal target throttle opening degree tgtθth, and then temporarily ends the routine.
[0022]
If the determination in step S12 is YES, the process shifts to step S16 to determine whether a direct connection completion command has been input from the ATCU 12 side. When the determination is NO, the process proceeds to step S14, and when the determination is YES, the process proceeds to step S18, where the throttle opening θth is gradually reduced at a predetermined rate of change Δθ, and then the routine is terminated.
[0023]
Accordingly, the throttle opening θth is reduced with the rate of change Δθ by the processing in step S18 from the time when the engine rotation reduction suppression command is input from the ATCU 12 to the time when the direct connection completion command is input. Here, as the rate of change Δθ of the throttle opening θth, a value that ensures a deceleration that does not cause a driver who wants to decelerate to feel uncomfortable, and that reduces the engine speed Ne as slowly as possible is applied. Is done.
[0024]
According to the processing on the ECU 11 side and the ATCU 12 side, when the vehicle is started to decelerate while the torque converter 3 is not directly connected, lock-up control is executed as shown in FIG.
When the accelerator is fully closed by the driver and the vehicle starts to decelerate, the control duty of the solenoid 5a is raised on the ATCU 12 side, while the ECU 11 receives the command to suppress the decrease of the engine rotation on the ECU 11 side, and the throttle opening degree θth is reduced. It is reduced with the rate of change Δθ.
[0025]
Thereafter, the control duty of the solenoid 5a is lowered on the ATCU 12 side based on the determination of the direct connection completion, and the ECU 11 receives the direct connection completion command and returns to the normal throttle control. Therefore, the throttle opening θth corresponds to the accelerator fully closed. It drops sharply to the value equivalent to idle. When a predetermined fuel cut condition (for example, a predetermined vehicle speed or more while the vehicle is being decelerated) is satisfied, the ECU 11 starts the fuel cut by stopping the fuel injection.
[0026]
As described above, in the lock-up control device for the automatic transmission according to the present embodiment, the torque converter 3 is directly connected even when the vehicle is decelerated in the non-directly connected state, so that the engine 1 can execute the fuel cut. , Thereby improving fuel efficiency.
By the lock-up control described above, the decrease in the engine rotation speed Ne during the accelerator closing operation becomes slow, and even when the direct connection of the torque converter 3 is completed due to the increase in the hydraulic pressure, the engine rotation speed Ne decreases the turbine rotation speed Nt. The rotation speed is kept at around the turbine rotation speed Nt without dropping significantly. Therefore, the direct connection of the torque converter 3 is performed in a state where the engine rotation speed Ne and the turbine rotation speed Nt are extremely close to each other, and it is possible to suppress the occurrence of a shock at the time of the direct connection.
[0027]
In the present embodiment, since the throttle opening θth at the start of deceleration is used as a starting point and the throttle opening θth is sequentially reduced based on the rate of change Δθ, the engine speed Ne rapidly decreases regardless of the running state of the vehicle. Can be appropriately suppressed. That is, as described in [Problems to be Solved by the Invention], when the vehicle shifts from rapid acceleration to deceleration, the turbine rotation speed Nt that follows the engine rotation speed Ne is still low. When the throttle opening θth is set based on the turbine rotation speed Nt as described above, an excessively small throttle opening θth is applied. On the other hand, in the present embodiment, since the throttle opening θth is sequentially reduced from the start of deceleration regardless of the turbine rotation speed Nt, the sudden decrease in the engine rotation speed Ne is always ensured based on the appropriate throttle opening θth. The occurrence of a shock can be prevented by suppressing the occurrence of the shock.
[0028]
Moreover, since the throttle opening θth is continuously reduced based on the rate of change Δθ, the throttle opening θth set from the turbine rotation speed Nt at the start of deceleration is maintained for a predetermined time, as in the technique of Patent Document 1. The engine rotation speed Ne can be reduced more smoothly than in the case where it is applied, and this factor also contributes to the prevention of the occurrence of a shock at the time of direct connection.
[0029]
On the other hand, after the direct connection of the torque converter 3 is completed, the control immediately returns to the normal throttle control to rapidly reduce the throttle opening θth to a value equivalent to idle. Although the rate of change Δθ of the throttle opening θth is designed to secure a certain degree of deceleration as described above, the obtained deceleration is weaker than when a normal accelerator is fully closed. If the control is continued up to the idle equivalent value, the driver is given an impression that the deceleration is insufficient, but by immediately returning to the normal throttle control after the completion of the direct connection, the driver may feel uncomfortable due to the insufficient deceleration. Can be prevented beforehand.
[0030]
The embodiment has been described above, but aspects of the present invention are not limited to this embodiment. For example, in the above-described embodiment, the lock-up control device of the automatic transmission 2 having the planetary gear mechanism is embodied. However, if the automatic transmission is a torque converter type, the type of the transmission mechanism is not limited. For example, the present invention may be applied to a CVT type automatic transmission.
[0031]
Further, in the above embodiment, the change rate Δθ of the throttle opening θth is set as a fixed value. However, the change rate Δθ may be changed according to, for example, the engine rotation speed Ne or the vehicle speed V at the start of deceleration. Note that the change rate Δθ does not necessarily need to be changed linearly, but may be changed in a quadratic function or an exponential function, or the change rate Δθ may be changed in the middle of the engine rotation reduction suppression command. May be.
[0032]
Furthermore, in the above-described embodiment, the throttle opening is returned to the normal throttle in synchronization with the completion of the direct connection of the torque converter 3, but it is not always necessary to synchronize the throttle opening. May be returned.
[0033]
【The invention's effect】
As described above, according to the lock-up control device of the automatic transmission according to the first aspect of the invention, the shock can be suppressed and the lock-up clutch can be directly connected even after the start of deceleration of the vehicle, thereby ensuring good drivability. Thus, it is possible to increase the opportunity for fuel cut and achieve improvement in fuel efficiency.
[0034]
According to the lockup control device for an automatic transmission according to the second aspect of the present invention, in addition to the first aspect, the deceleration according to the accelerator closing operation is obtained to prevent the driver from feeling uncomfortable. Can be.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram illustrating a lockup control device according to an embodiment.
FIG. 2 is a flowchart illustrating a direct connection control routine executed by an ATCU.
FIG. 3 is a flowchart illustrating a rotation reduction suppression routine executed by an ECU.
FIG. 4 is a time chart showing a lock-up control situation when the vehicle is decelerated.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Torque converter 4 Lockup clutch 6 Intake passage 7 Throttle valve 11 ECU (Lockup control means)
12 ATCU (lockup control means, direct connection determination means)

Claims (2)

A torque converter interposed between the engine and the automatic transmission, a lock-up clutch capable of mechanically directly connecting the input side and the output side of the torque converter,
A lock-up control device for an automatic transmission having a lock-up control unit that controls the lock-up clutch based on a running state of the vehicle.
The lock-up control means switches the torque converter to the direct connection state by the lock-up clutch when the deceleration of the vehicle is started in response to the accelerator closing operation in the non-direct connection state of the torque converter, A lock-up control device for an automatic transmission, wherein a throttle valve provided in a passage is controlled to gradually close at a predetermined rate from a throttle opening at the start of deceleration. Direct connection determination means for determining the direct connection completion of the torque converter,
The lock-up control means stops throttle control based on the predetermined rate of change and closes the throttle valve when the direct connection determination means determines that the direct connection of the torque converter is completed. 2. A lock-up control device for an automatic transmission according to claim 1.

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