JP2001330142A - Control device for automatic transmission with lockup clutch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform proper release of a lockup clutch at the time of low speed running. SOLUTION: Ascent/descent control during execution is decided (S21), when the decision is NO, the release timing of a lockup clutch is set to an ordinary value Akm/h (S22). In the other hand, when the decision is YES, the release timing is set to a value Bkm/h higher than the ordinary value Akm/h (S23).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an automatic transmission with a lock-up clutch having a lock-up clutch directly connecting an input shaft and an output shaft, and releases the lock-up clutch when the vehicle speed falls below a lower limit vehicle speed. The present invention relates to a control device for an automatic transmission with an up clutch.

[0002]

2. Description of the Related Art Conventionally, an automatic transmission for automatically changing a gear ratio has been known, and is mounted on many automobiles. In this automatic transmission, a torque converter, which is a power transmission mechanism using a normal working fluid, is used, where slippage occurs and power transmission efficiency is reduced. Therefore, in a normal case, a lock-up clutch for directly connecting the input shaft and the output shaft of the torque converter is provided, and the input shaft and the output shaft are directly connected as necessary.

[0003] Japanese Patent Laid-Open Publication No. 2-72268 discloses such an automatic transmission with a lock-up clutch. Then, in the device of this publication, when the vehicle is decelerated, the lock-up clutch is engaged to increase the engine speed at this time. This allows the engine to cut fuel to relatively low speeds,
Fuel efficiency can be improved.

In addition, a continuously variable transmission (hereinafter referred to as CVT (Continuously Variable Ratio Tran
smission) is known. In this CVT,
Since the shift can be performed smoothly, the input shaft rotation speed can be arbitrarily set. Therefore, it is possible to maintain the engine speed up to a low vehicle speed and to engage the lock-up clutch. For this reason, the fuel cut region of the engine can be expanded, which is advantageous in improving fuel efficiency.

However, at low vehicle speeds in the CVT,
The speed ratio of the transmission is set to the low side in order to secure the power performance when re-acceleration is performed. Therefore, if the release vehicle speed of the lock-up clutch at the time of vehicle deceleration (lower limit vehicle speed at which the lock-up clutch is released) is set to be low, the deceleration may become large and a sense of incongruity may occur, or the engine may stall during sudden braking. .

Therefore, the release vehicle speed of the lock-up clutch is set as low as possible within a range where the driving performance is not deteriorated.

[0007]

Here, in the automatic transmission, for example, in order to ensure the driving performance when climbing a hill, when the vehicle is detected to be on an uphill road, control for correcting the gear ratio to the low side is performed. Is performed. On a downhill road, control is performed to correct the gear ratio to the low side in order to secure the engine braking force.

When such control is performed, the gear ratio is set lower than the normal gear ratio, so that the release timing of the lock-up clutch on the low vehicle speed side becomes inappropriate. There was a problem that it would.

That is, when the lock-up clutch is engaged up to a low vehicle speed despite the fact that the speed ratio is set to a lower side than the normal speed ratio, when the acceleration / deceleration operation is performed, the engine torque is reduced. Changes are transmitted directly to the automatic transmission. Then, as the gear ratio is set to the low side, the change in the driving torque increases. For this reason, the behavior of the vehicle becomes jerky, and the running feeling deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a control device for an automatic transmission with a lock-up clutch that can make the release timing of the lock-up clutch appropriate.

[0011]

The present invention is applied to an automatic transmission with a lock-up clutch having a lock-up clutch directly connecting an input shaft and an output shaft, and releases the lock-up clutch when the vehicle speed falls below a lower limit vehicle speed. In the control device for an automatic transmission with a lock-up clutch, when performing low-side control in which the speed ratio of the automatic transmission is lower than a normal speed ratio, the lower limit vehicle speed is reduced to the low side. It is characterized in that it is set higher than when control is not executed. With this configuration, when the vehicle is running at a low speed, the drive torque changes when an acceleration / deceleration operation is performed due to the lock-up clutch being engaged and the gear ratio being set to a large low side. And the running feeling can be prevented from deteriorating.

Further, it is preferable that the automatic transmission is a continuously variable transmission. In the continuously variable transmission, since the shift can be continuously performed, the lock-up clutch can be engaged up to a relatively low vehicle speed. For this reason, the control of the present invention becomes more effective.

[0013] Preferably, the low-side control is a control for determining a road surface gradient of a traveling road surface and increasing the lower limit input shaft rotation speed of the continuously variable transmission when it is determined that the road is an uphill road. It is.

Preferably, the low-side control is a control for increasing a lower limit input shaft rotation speed of the continuously variable transmission when determining a road surface gradient of a traveling road surface and determining that the road is a downhill. is there.

When the vehicle is going up or down a hill, control is performed to increase the speed ratio (low side) in order to increase the output torque or secure engine braking. In such a case, by increasing the lower limit vehicle speed, it is possible to prevent a change in the driving torque from being increased when the acceleration / deceleration operation is performed, thereby preventing the traveling feeling from deteriorating.

[0016]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[Overall Configuration of CVT] FIG. 1 is a diagram showing a schematic configuration of a vehicle drive device 1 of the present embodiment. The output of the engine 2 as a prime mover is transmitted to drive wheels 4 via a power transmission device 3 to drive the vehicle. The control unit 5 that controls the vehicle drive device 1 obtains predetermined control parameters of the engine 2 and the power transmission device 3 from predetermined parameters indicating the running state of the vehicle such as the operation state of the engine 2 and the operation state of the power transmission device 3. Is calculated. The control parameters are, for example, a throttle valve opening, a fuel injection amount, a gear ratio, and the like. By controlling these, the engine 2 and the power transmission device 3 are controlled to predetermined states.

FIG. 2 is a schematic configuration diagram of a power transmission device 3 including a CVT (continuously variable transmission). The output of Engine 2 is
Torque converter 10 as fluid transmission mechanism, forward / reverse switching mechanism 12, CVT 14, deceleration mechanism 16, differential device 18
To the drive shaft 20 to drive the vehicle.

Front cover 2 of torque converter 10
2 rotates by the power of the engine 2, and transmits this rotation to the pump impeller 24 and the oil pump 26. The oil pump 26 supplies a working fluid to a hydraulic control mechanism of each part of the power transmission device 3. This working fluid also functions as a lubricating oil. The pump impeller 24 transfers the working fluid filled in the torque converter 10 to the turbine liner 2.
8 to the turbine liner 28
Rotates. Turbine liner 28 is coupled for rotation with torque converter output shaft 30 so that rotation of turbine liner 28 is the output of torque converter 10. The working fluid that has passed through the turbine liner 28 passes through the stator liner 32 and is sent to the pump impeller 24. The stator liner 32 is supported via a one-way clutch 34. In a region where the input / output speed ratio of the torque converter 10 is relatively low (below the clutch point), the one-way clutch 34 is locked, and the stator liner 32
Is fixed. At this time, the stator liner 32 changes the direction of the working fluid sent from the turbine liner 28, and sends the working fluid toward the pump impeller 24 from behind the rotation thereof. As a result, the torque is amplified. When the speed ratio of the torque converter 10 exceeds the clutch point, the working fluid delivered from the turbine liner 28 flows so as to impinge on the back surface of the stator liner 32, whereby the one-way clutch 34 is released, and the stator liner 32 idles. I do. At this time, no torque amplification is performed, and the torque converter 10 functions as a fluid coupling.

The torque converter 10 has a lock-up clutch that directly connects the input shaft and the output shaft. The direct-coupled clutch plate 36 is disposed so as to face the front cover 22, and is connected to the torque converter output shaft 30.
It rotates integrally and is slidably supported in the axial direction. A torsional damper 38 that absorbs torsional shock and vibration is disposed between an outer peripheral portion that comes into contact with the front cover 22 and a central portion that is supported by the output shaft 30. At the time of the direct connection, the working fluid from the fluid pressure control circuit 40 controlled by the control unit 5 is supplied to the direct connection clutch plate 3.
The plate 36 slides rightward in the figure by this pressure and engages with the front cover 22. As a result, power is transmitted without using the working fluid. In order to release the direct connection state, the working fluid is supplied to the front side 44 of the direct connection clutch plate 36, and the pressure causes the plate 36 to slide leftward in the drawing and to be separated from the front cover 22.

The forward / reverse switching mechanism 12 is configured as a so-called double planetary type planetary gear mechanism having two rows of planetary gears. Sun gear 46 is coupled to torque converter output shaft 30. The two rows of planetary gears 48 are rotatably supported by a common carrier 50. The carrier 50 is coupled to the torque converter output shaft 30 via a forward clutch 52. Carrier 50 is also coupled to input shaft 54 of CVT 14. A reverse brake 58 is engageable with the ring gear 56.

During forward movement, the forward clutch 52 is engaged by the supply of working fluid from the fluid pressure control circuit 40, and the torque converter output shaft 30 and the CVT input shaft 54
Is directly connected. When the vehicle is moving backward, the forward clutch 52 is controlled to be released, and the reverse brake 58 is controlled to be engaged by the supply of working fluid from the fluid pressure control circuit 40. Thereby, the torque converter output shaft 30
And the carrier 50 rotate in opposite directions. That is,
The rotation direction is reversed before and after the forward / reverse switching device 12.

By releasing both the forward clutch 52 and the reverse brake 58, the power transmission device 3 is set in a neutral state.

The CVT 14 has an input pulley 60 that rotates integrally with the CVT input shaft 54, an output pulley 62, and a belt 64 wound around these pulleys 60, 62. The output side pulley 62 rotates the CVT output shaft 66 and sends power to the speed reduction mechanism 16.

The input side pulley 60 further includes a fixed sheave 6
8 and a movable sheave 70. These sheaves 6
8, 70 are arranged in parallel in the direction of the CVT input shaft 54,
The opposite surface is formed on the side of the cone or truncated cone. The movable sheave 70 rotates integrally with the CVT input shaft 54, while itself functions as a fluid pressure actuator, and moves in the axial direction by the supply control of the working fluid by the fluid pressure control circuit 40. By moving the movable sheave 70, the two sheaves 6 formed in a side shape such as the cone
The spacing between the 8,70 opposing surfaces is changed. Similarly to the input side, the output side pulley 62 also includes a fixed sheave 72 and a movable sheave 74 having substantially conical side surfaces facing each other.
The movable sheave 74 also moves in the axial direction by controlling the supply amount of the working fluid, whereby the distance between the two sheaves 72 and 74 is changed.

The belt 64 has an input side and an output side pulley 6.
0, 62 has a substantially trapezoidal cross-sectional shape that engages with the shape of the opposing surfaces of the fixed sheaves 68, 72 and the movable sheaves 70, 74, respectively.
74 so as to be sandwiched therebetween. Fixed sheave 6
By changing the distance between the movable sheaves 8 and 72 and the movable sheaves 70 and 74, the radius of rotation at the position where the belt 64 is wound around changes. In addition, when the rotation radius at the position where the belt 64 is wound changes on the input / output side, the speed ratio between the input / output shafts 54 and 66 of the CVT changes. Movable sheave 7
Since the positions of 0 and 74 can be continuously determined to be arbitrary positions, the speed ratio of the CVT 14 can take a continuous value in a predetermined range.

As shown in FIG. 2, in order to control the vehicle driving device 1, the control unit 5 includes a vehicle speed sensor 76 for detecting the speed of the vehicle, an NE sensor 78 for detecting the rotation speed of the engine 2, and a lever. A shift sensor 80 for detecting the selected shift position, a pedal sensor 82 for detecting the operation amount of the accelerator pedal, an input shaft speed sensor 84 for detecting the rotation speed of the CVT input shaft 54, a pedal switch for detecting the operation of the brake pedal. Signals from various sensors and switches such as 86 are input. The control unit 5 controls the torque converter 10 and the CVT 14 based on output values from these sensors and switches.

"Uphill / Downhill Control" Next, the control of the target input shaft rotation speed of the CVT 14 during uphill and downhill performed by the control unit 5 will be described with reference to FIG.

The control unit 5 first reads the detection values of various sensors (S11). Next, the target input shaft speed NINT is calculated based on the detected values of the various sensors (S12). The target input shaft rotation speed NINT is set to be higher as the vehicle speed is higher, and to be higher as the accelerator pedal operation amount is larger, and the controller 5 stores the target input shaft rotation speed NINT as a map.

Further, a road gradient is calculated based on the measured values of the various sensors (S13). This is calculated based on the actual acceleration obtained from the detected change in the vehicle speed, the engine output torque calculated from the accelerator pedal operation amount, and the like.

As described above, when the road surface gradient is detected, it is determined whether the road surface gradient (the absolute value of the calculated road surface gradient) is equal to or larger than a predetermined value (S14). If it is determined in step S14 that the road surface gradient is equal to or greater than the predetermined threshold value, the target input shaft rotation speed NINT is set to the predetermined lower limit guard value N.
It is determined whether it is greater than INTGD (S15).

If it is determined in S15 that the target input shaft speed NINT is equal to or lower than the predetermined lower limit guard value NINTGD, the target input shaft speed NINT is set to the predetermined lower limit guard value NINTGD (S16). On the other hand, if it is determined in S15 that the target input shaft speed NINT is larger than the predetermined lower limit guard value NINTGD, the target input shaft speed NINT is left as it is (S17), and the process ends.

Accordingly, when the road surface gradient is equal to or higher than the predetermined value, the target input shaft speed NINT is reduced to the lower limit guard value NI.
It is set to NTGD or higher, and does not become smaller. Then, the speed ratio of the CVT 14 is controlled such that the actual input shaft speed NIN matches the target input shaft speed NINT set in this way.

It is also preferable to provide two or more threshold values for the road surface gradient, and to provide two or more lower limit guard values according to the magnitude of these threshold values. Also, in this example,
Although the threshold value of the road surface gradient and the lower limit guard value are set according to the road surface gradient irrespective of whether the vehicle is climbing or descending, it is also preferable to change these values according to whether the vehicle is traveling uphill or downhill.

"Lockup Release Timing Control" Next, control of the lockup clutch release timing performed by the control unit 5 will be described. By engaging the lock-up clutch even at low speeds, fuel efficiency can be improved.However, as described above, the engine brake becomes too large during deceleration, or the engine stall occurs during sudden deceleration. There is a risk of occurring. Therefore,
In consideration of these, the lower limit speed L / Uoff vehicle speed at which the lockup clutch is turned off is set.

In the present embodiment, the control unit 5 changes the lower limit speed L / Uoff vehicle speed when climbing up or downhill.

That is, as shown in FIG. 4, it is determined whether or not the uphill control shown in FIG. 3 is being executed (S21). That is, when the target input shaft rotation speed NINT is equal to or lower than the lower limit guard value when climbing up or downhill, the target input shaft rotation speed NINT is controlled so as not to be lower than the lower limit guard value. When such control is being performed, the speed ratio of the CVT 14 is set to a low side as compared with the case where such control is not being performed.

When the lock-up clutch is engaged up to a low vehicle speed even if the speed ratio is set to a lower side than the normal speed ratio as described above, the engine torque is reduced when the acceleration / deceleration operation is performed. Is directly transmitted to the CVT 14. Then, as the gear ratio is set to the low side, the change in the driving torque increases. For this reason, the vehicle behavior becomes jerky, and the running feeling deteriorates.

Therefore, if the determination in S21 is NO, the L / Uoff vehicle speed is set to Akm / h (S
22). If YES in the determination in S21,
The L / Uoff vehicle speed is set to Bkm / h (S23).

Here, A <B is set. For this reason, during the execution of the uphill / downhill control, the off timing of the lock-up clutch can be set to a relatively high vehicle speed before the gear ratio is set to the low side to prevent the above-described problem from occurring. can do.

The above A and B are, for example, 15 km /
h, which is set to about 25 km / h.

"Lock-up release timing control when both accelerator and brake are depressed" In a vehicle having an automatic transmission such as the CVT 14, the brake pedal may be depressed while the accelerator pedal is depressed. When the lower limit speed L / Uoff for turning off the lock-up clutch is set to the aforementioned Akm / h at the time of depressing both the accelerator and the brake, when the accelerator pedal is released, the engine braking force increases. The change in the braking torque increases, and the driving feeling deteriorates.

Therefore, the control unit 5 changes the lower limit speed L / Uoff vehicle speed even when both the accelerator pedal and the brake pedal are depressed. This will be described with reference to FIG.

The control unit 5 first determines whether the accelerator pedal and the brake pedal are depressed (S3).
1). If the determination in S31 is NO, L / U
The off vehicle speed is set to Akm / h (S32). Also,
If the determination in S31 is YES, the L / Uoff vehicle speed is set to Bkm / h (S33).

Here, A <B is set. Thus, when both the accelerator and the brake are depressed, the lock-up clutch can be turned off at a relatively high vehicle speed, and the above-described problem can be prevented.

Further, instead of detecting both steps of the accelerator pedal and the brake pedal, if the accelerator is depressed and the vehicle is actually decelerating, the release timing of the lock-up clutch is set to a relatively high vehicle speed. May be set.

In the above embodiment, the torque converter is described as an example of the fluid transmission mechanism. However, the present invention can be similarly applied to other fluid transmission mechanisms, for example, a fluid coupling. Further, in the above-described embodiment, the description has been given by taking the continuously variable transmission as an example, but the present invention can be similarly applied to a stepped transmission in which the gear is changed by switching gears.

Further, in the above-described embodiment, as an example of low-side control for setting the speed ratio to a lower side than the normal speed ratio, up-downhill control is taken as an example. The lower limit speed L / Uoff vehicle speed at which the vehicle is turned off is set high, but the present invention is not limited to this. That is, other low-side control, for example, low-side control to set the speed ratio to a lower side than the normal speed ratio by setting a lower limit guard value of the target input shaft speed according to the temperature of the working fluid, The present invention can be similarly applied to other low-side control such as low-side control based on a manual operation of a driver.

[0049]

As described above, according to the present invention,
When the vehicle is running at a low speed, the change in drive torque increases when an acceleration / deceleration operation is performed due to the fact that the lock-up clutch is engaged and the gear ratio is set to a low side, Deterioration of running feeling can be prevented.

In particular, in the case of a continuously variable transmission, since the shift can be continuously performed, the lock-up clutch can be engaged up to a relatively low vehicle speed, so that the control of the present invention is more effective.

As the low-side control, there is a control at the time of going up a hill and a control at the time of going down a hill. In this case, the present invention is preferable.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an entire CVT system.

FIG. 2 is a configuration diagram of the system of FIG. 1;

FIG. 3 is a flowchart illustrating target input shaft rotation speed control during uphill and downhill.

FIG. 4 is a flowchart showing lock-up release timing control when going up and down a hill.

FIG. 5 is a flowchart showing lock-up release timing control when both the accelerator and the brake are depressed.

[Explanation of symbols]

 5 control part, 36 lock-up plate.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Katsumi Kono 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Tadashi Tamura 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Koji Taniguchi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kenji Matsuo 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F term (reference) 3J053 CB06 CB14 CB21 DA04 DA06 DA23 DA26

Claims (4)

[Claims] 1. An automatic transmission with a lock-up clutch, which is applied to an automatic transmission with a lock-up clutch having a lock-up clutch that directly connects an input shaft and an output shaft, and releases the lock-up clutch when the vehicle speed falls below a lower limit vehicle speed. In the control device, when performing low-side control that sets the speed ratio of the automatic transmission to a lower side than a normal speed ratio, the lower-limit vehicle speed is less than when the low-side control is not performed. Control device for an automatic transmission with a lock-up clutch set at a higher setting. 2. The control device for an automatic transmission with a lock-up clutch according to claim 1, wherein the automatic transmission is a continuously variable transmission. 3. The apparatus according to claim 2, wherein the low-side control determines a road surface gradient of a traveling road surface, and determines a lower limit input shaft rotation speed of the continuously variable transmission when it is determined that the road is an uphill road. Control device for an automatic transmission with a lock-up clutch, which is a control to increase the pressure. 4. The apparatus according to claim 2, wherein the low-side control determines a road surface gradient of a traveling road surface and, when it is determined that the vehicle is on a downhill road, a lower limit input shaft rotation speed of the continuously variable transmission. Control device for an automatic transmission with a lock-up clutch, which is a control to increase the pressure.