JP4310889B2 - Control device for automatic transmission with lock-up clutch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention 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 an automatic transmission with a lock-up clutch that releases a lock-up clutch when the vehicle speed becomes lower than a lower limit vehicle speed. The present invention relates to a control device.
[0002]
[Prior art]
Conventionally, automatic transmissions that automatically change gear ratios are known and are installed in many automobiles. In this automatic transmission, a torque converter that is a power transmission mechanism using a normal working fluid is used, where slip occurs and power transmission efficiency decreases. Therefore, normally, a lockup clutch that directly connects 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 Application Laid-Open No. 2-72268 discloses such an automatic transmission with a lock-up clutch. And in the apparatus of this gazette, the engine speed at this time is raised by engaging a lockup clutch at the time of vehicle deceleration. As a result, the fuel to the engine can be cut to a relatively low speed, and the fuel consumption can be improved.
[0004]
A continuously variable transmission (hereinafter referred to as CVT (Continuously Variable ratio Transmission)) capable of continuously changing a gear ratio is known. In this CVT, the speed change can be performed smoothly, so that the input shaft rotation speed can be arbitrarily set. Therefore, the engine speed can be maintained up to a low vehicle speed and the lockup clutch can be engaged. For this reason, the fuel cut area of the engine can be expanded, which is advantageous in improving fuel consumption.
[0005]
However, in CVT, at a low vehicle speed, the transmission gear ratio is set to the low side to ensure power performance when reacceleration is performed. For this reason, if the release vehicle speed of the lockup clutch at the time of deceleration of the vehicle (the lower limit vehicle speed at which the lockup clutch is released) is set low, there is a possibility that the deceleration becomes large and uncomfortable or an engine stall occurs during sudden braking. .
[0006]
Therefore, the release vehicle speed of the lockup clutch is set as low as possible within a range that does not cause deterioration in driving performance.
[0007]
[Problems to be solved by the invention]
Here, in the automatic transmission, for example, when it is detected that the road is an uphill road in order to ensure the driving performance at the time of climbing, control for correcting the gear ratio to the low side is performed. On the downhill road, control for correcting the gear ratio to the low side is performed in order to secure the engine braking force.
[0008]
When such control is performed, the gear ratio is set to be lower than the normal gear ratio, so that the lock-up clutch release timing on the low vehicle speed side described above becomes inappropriate. There was a point.
[0009]
That is, when the lockup clutch is engaged to a low vehicle speed even though the gear ratio is set to be lower than the normal gear ratio, the engine torque changes directly when the acceleration / deceleration operation is performed. To the automatic transmission. As the gear ratio is set to a large low side, the change in drive torque increases. For this reason, the vehicle behavior becomes jerky, and the running feeling is deteriorated.
[0010]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a control device for an automatic transmission with a lockup clutch that can make the release timing of the lockup clutch appropriate.
[0011]
[Means for Solving the Problems]
The present invention 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 an automatic transmission with a lock-up clutch that releases a lock-up clutch when the vehicle speed becomes lower than a lower limit vehicle speed. In the control device, when the accelerator and the brake are both depressed, the lower limit vehicle speed is set higher than when the accelerator and the brake are not depressed .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.
[0017]
“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 the drive wheels 4 via the power transmission device 3 to drive the vehicle. The control unit 5 that controls the vehicle drive device 1 determines 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 parameters, the engine 2 and the power transmission device 3 are controlled to a predetermined state.
[0018]
FIG. 2 is a schematic configuration diagram of a power transmission device 3 including a CVT (continuously variable transmission). The output of the engine 2 is transmitted to the drive shaft 20 via the torque converter 10 as a fluid transmission mechanism, the forward / reverse switching mechanism 12, the CVT 14, the speed reduction mechanism 16, and the differential device 18 to drive the vehicle.
[0019]
The front cover 22 of the torque converter 10 is rotated 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 the 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 sends the working fluid filled in the torque converter 10 to the turbine liner 28, and the turbine liner 28 rotates in response to this. The turbine liner 28 is coupled to rotate together with the torque converter output shaft 30, whereby the rotation of the turbine liner 28 becomes the output of the 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 an area where the input / output speed ratio of the torque converter 10 is relatively low (below the clutch point), the one-way clutch 34 is engaged and the stator liner 32 is fixed. At this time, the stator liner 32 changes the direction of the working fluid delivered from the turbine liner 28 and feeds the working fluid toward the rear from the rotational rear side of the pump impeller 24. This amplifies the torque. 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 strike the back surface of the stator liner 32, whereby the one-way clutch 34 is released and the stator liner 32 is idling. To do. At this time, torque amplification is not performed, and the torque converter 10 functions as a fluid coupling.
[0020]
The torque converter 10 has a lock-up clutch that directly connects the input shaft and the output shaft. The direct clutch plate 36 is disposed so as to face the front cover 22, and rotates integrally with the torque converter output shaft 30 and is supported so as to be slidable in the axial direction. A torsion damper 38 that absorbs shock and vibration in the torsional direction is disposed between the outer peripheral part that contacts the front cover 22 and the center part supported by the output shaft 30. At the time of direct connection, the working fluid from the fluid pressure control circuit 40 controlled by the control unit 5 is supplied to the back side 42 of the direct connection clutch plate 36, and the plate 36 slides to the right in the figure by this pressure, and the front cover 22 is engaged. 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 plate 36 slides in the left direction in the drawing and is separated from the front cover 22 by this pressure.
[0021]
The forward / reverse switching mechanism 12 is configured as a so-called double planetary 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 the forward clutch 52. The carrier 50 is also coupled to the input shaft 54 of the CVT 14. A reverse brake 58 can be engaged with the ring gear 56.
[0022]
At the time of forward movement, the forward clutch 52 is engaged by the supply of the working fluid from the fluid pressure control circuit 40, and the torque converter output shaft 30 and the CVT input shaft 54 are directly connected. During reverse travel, the forward clutch 52 is controlled to the released state, while the reverse brake 58 is controlled to be engaged by the supply of the working fluid from the fluid pressure control circuit 40. As a result, 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.
[0023]
Note that the power transmission device 3 is in a neutral state by releasing both the forward clutch 52 and the reverse brake 58.
[0024]
The CVT 14 includes an input-side pulley 60 that rotates integrally with the CVT input shaft 54, an output-side pulley 62, and a belt 64 that is wound around these pulleys 60 and 62. The output-side pulley 62 rotates the CVT output shaft 66 and sends power to the speed reduction mechanism 16.
[0025]
The input side pulley 60 further includes a fixed sheave 68 and a movable sheave 70. These sheaves 68 and 70 are arranged in parallel in the direction of the CVT input shaft 54, and their opposing surfaces are formed on the side surfaces of a cone or a truncated cone. While the movable sheave 70 rotates integrally with the CVT input shaft 54, the movable sheave 70 functions as a fluid pressure actuator and moves in the axial direction by controlling the supply amount of the working fluid by the fluid pressure control circuit 40. By the movement of the movable sheave 70, the distance between the opposing surfaces of the two sheaves 68, 70 formed in the side shape such as the cone is changed. Similarly to the input side, the output-side pulley 62 includes a fixed sheave 72 and a movable sheave 74 having opposing surfaces having a substantially conical side shape. The movable sheave 74 is also moved 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.
[0026]
The belt 64 has a substantially trapezoidal cross-sectional shape that engages with the shape of the opposed surfaces of the fixed sheaves 68 and 72 of the input side and output side pulleys 60 and 62 and the movable sheaves 70 and 74, and the fixed sheaves 68 and 72. Are held between the movable sheaves 70 and 74. As the distance between the fixed sheaves 68 and 72 and the movable sheaves 70 and 74 changes, the radius of rotation at the position where the belt 64 is wound changes. In addition, the speed ratio of the input / output shafts 54 and 66 of the CVT changes as the rotational radius of the position where the belt 64 is wound changes on the input / output side. Since the positions of the movable sheaves 70 and 74 can be determined continuously at arbitrary positions, the transmission ratio of the CVT 14 can take a continuous value within a predetermined range.
[0027]
As shown in FIG. 2, in order to control the vehicle drive device 1, the control unit 5 is selected by a vehicle speed sensor 76 for detecting the speed of the vehicle, an NE sensor 78 for detecting the rotational speed of the engine 2, and a lever. A shift sensor 80 that detects the shift position, a pedal sensor 82 that detects the amount of operation of the accelerator pedal, an input shaft rotational speed sensor 84 that detects the rotational speed of the CVT input shaft 54, a pedal switch 86 that detects the operation of the brake pedal, etc. Signals from various sensors and switches are input. The control unit 5 controls the torque converter 10 and the CVT 14 based on output values from these sensors and switches.
[0028]
"Control when climbing or descending"
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.
[0029]
The control unit 5 first reads detection values of various sensors (S11). Next, the target input shaft rotation speed NINT is calculated and calculated based on the read detection values of the various sensors (S12). The target input shaft rotational speed NINT is set to be higher as the vehicle speed is higher and higher as the accelerator pedal operation amount is larger, and the control unit 5 stores the map as a map.
[0030]
Furthermore, a road surface gradient is calculated based on the measured values of 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.
[0031]
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 greater than a predetermined value (S14). If it is determined in S14 that the road surface gradient is equal to or greater than a predetermined threshold value, it is determined whether the target input shaft rotational speed NINT is greater than a predetermined lower limit guard value NINTGD (S15).
[0032]
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.
[0033]
As a result, when the road surface gradient is equal to or greater than a predetermined value, the target input shaft rotational speed NINT is set to be equal to or greater than the lower limit guard value NINTGD and does not become smaller than that. The gear ratio of the CVT 14 is controlled so that the actual input shaft rotational speed NIN matches the target input shaft rotational speed NINT set in this way.
[0034]
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 magnitudes of these threshold values. Also, in this example, the road surface gradient threshold and the lower limit guard value are set according to the road gradient regardless of whether it is climbing or descending, but these values may be changed depending on the climbing slope. Is preferred.
[0035]
"Lock-up release timing control"
Next, the control of the release timing of the lockup clutch performed by the control unit 5 will be described. By engaging the lock-up clutch even at low speeds, fuel efficiency can be improved, but as mentioned above, the engine brake becomes too large during deceleration or engine stall occurs during sudden deceleration. There is a risk of occurring. In view of these, a lower limit speed L / Uoff vehicle speed for turning off the lockup clutch is set.
[0036]
In the present embodiment, the control unit 5 changes the lower limit speed L / Uoff vehicle speed when climbing or descending.
[0037]
That is, as shown in FIG. 4, it is determined whether the uphill / downhill control shown in FIG. 3 is being performed (S21). That is, at the time of climbing or descending, when the target input shaft rotational speed NINT is less than or equal to the lower limit guard value, control is performed so that it does not fall below the lower limit guard value. When such control is performed, the gear ratio of the CVT 14 is set to the low side as compared with the case where such control is not performed.
[0038]
In this way, even if the gear ratio is set to a lower side than the normal gear ratio, if the lockup clutch is engaged to a low vehicle speed, the engine torque changes when the acceleration / deceleration operation is performed. Directly transmitted to CVT14. As the gear ratio is set to a large low side, the change in drive torque increases. For this reason, the vehicle behavior becomes jerky, and the running feeling is deteriorated.
[0039]
Therefore, if the determination in S21 is NO, the L / Uoff vehicle speed is set to Akm / h (S22). If YES in S21, the L / Uoff vehicle speed is set to Bkm / h (S23).
[0040]
Here, A <B is set. For this reason, during the uphill / downhill control, the lock-up clutch can be turned off at a relatively high vehicle speed before the gear ratio is set to the low side, thereby preventing the above-described problems. can do.
[0041]
Note that A and B are set to about 15 km / h and 25 km / h, for example.
[0042]
"Lock-up release timing control when both accelerator and brake are depressed"
By the way, in a vehicle having an automatic transmission such as the CVT 14, the brake pedal may be depressed when the accelerator pedal is depressed. When the lower limit speed L / Uoff vehicle speed for turning off the lock-up clutch is set to the Akm / h when both the so-called accelerator and brake are depressed, the engine brake force increases when the accelerator pedal is released. The change in braking torque becomes large, and the running feeling is deteriorated.
[0043]
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.
[0044]
The controller 5 first determines whether the accelerator pedal and the brake pedal are depressed (S31). If NO in this determination of S31, the L / Uoff vehicle speed is set to Akm / h (S32). If YES in S31, the L / Uoff vehicle speed is set to Bkm / h (S33).
[0045]
Here, A <B is set. As a result, when the accelerator and the brake are both depressed, the lock-up clutch can be turned off at a relatively high timing, and the above-described problems can be prevented.
[0046]
Also, instead of detecting both depressions of the accelerator pedal and brake pedal, if the vehicle is actually decelerating even if the accelerator is depressed, set the release timing of the lockup clutch to a relatively high vehicle speed. Also good.
[0047]
In the above-described 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 such as fluid couplings. In the above embodiment, a continuously variable transmission has been described as an example. However, the present invention can also be applied to a stepped transmission that changes the gear position by switching gears.
[0048]
Furthermore, in the above-described embodiment, ascending / descending slope control is taken as an example of the low-side control for setting the gear ratio to the lower side than the normal gear ratio. Although the lower limit speed L / Uoff vehicle speed is set high, the present invention is not limited to this. That is, other low-side control, for example, low-side control for setting the gear ratio to be lower than the normal gear ratio by setting the 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 controls such as a low-side control based on a driver's manual operation.
[0049]
【The invention's effect】
As described above, according to the present invention , appropriate lockup clutch engagement control can be performed when both the accelerator and the brake are depressed.
[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 showing target input shaft speed control when climbing downhill.
FIG. 4 is a flowchart showing lockup release timing control during uphill / downhill.
FIG. 5 is a flowchart showing lockup release timing control when the accelerator and brake are both depressed.
[Explanation of symbols]
5 Control, 36 Lock-up plate.

Claims (2)

In a control device for an automatic transmission with a lockup clutch that is applied to an automatic transmission with a lockup clutch having a lockup clutch that directly connects an input shaft and an output shaft, and that releases the lockup clutch when the vehicle speed becomes lower than the lower limit vehicle speed.
A control device for an automatic transmission with a lockup clutch that sets the lower limit vehicle speed higher when the accelerator and the brake are both depressed than when both the accelerator and the brake are not depressed . The apparatus of claim 1.
The automatic transmission is a continuously variable transmission control device for an automatic transmission with a lock-up clutch.

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