JP5566156B2 - Automatic transmission lockup control method - Google Patents

Description

  The present invention relates to a lockup control method for an automatic transmission mounted on a vehicle such as an automobile.

  Conventionally, in a continuously variable transmission equipped with a torque converter in order to improve fuel efficiency, the input side of the torque converter connected to the crankshaft of the engine is directly connected to the output side connected to the continuously variable transmission mechanism. One having a lock-up device is known. Such a lockup device is generally operated when the vehicle speed becomes higher than a predetermined vehicle speed, that is, lockup is performed.

  For example, in Patent Document 1, in an automatic transmission having a torque converter including a lockup clutch, a slip operation region (and slip ratio) in which the slip rate is controlled to a target value from a so-called converter operation region that maximizes the slip rate in the lockup clutch. When the control of the lock-up clutch is shifted to the so-called lock-up operation region where the slip is minimized, the engagement pressure of the lock-up clutch is increased until the slip ratio reaches a predetermined ratio, and then the slip ratio reaches the target ratio. What is feedback controlled is shown.

  In a continuously variable transmission having such a lock-up clutch, the lock-up clutch is not sufficiently fastened when the lock-up is restarted by releasing the lock-up by decelerating and starting the acceleration run again. Therefore, a shock may occur when the lockup clutch is engaged. That is, the timing of shifting from the slip operation region to the lock-up operation region is determined by the difference between the engine rotation speed and the output speed of the torque converter. For example, after decelerating, the engine speed is increased again. In the driving state where the vehicle speed increases and the vehicle speed increases, an error occurs in the differential rotation speed due to the speed change operation of the continuously variable transmission, so that the transition timing is erroneously determined and the lockup clutch is engaged. When doing so, a shock is caused by fastening.

  This is because when the continuously variable transmission changes the gear ratio to a low speed side in such a running state, the differential rotational speed increased in the converter operating region is reduced, and the hydraulic pressure for operating the lockup clutch is still locked up. This is due to the fact that the slip in the lock-up operation region has been misunderstood, even though the pressure does not increase to the pressure required for the engine, that is, the pressure sufficient to draw the engine rotation. As described above, when only the differential rotation speed is monitored and the shift to the feedback control is determined, the lockup clutch is engaged from a state where the engagement pressure of the lockup clutch is lower than the pressure necessary for the engagement. When completely tightening, the hydraulic pressure changes to the side where it suddenly rises, and a shock is generated at the time of fastening.

JP-A-4-290675

The present invention focuses on the above points, and an object thereof is to reduce the shock that occurs at the time of lockup of the lockup device by improving the accuracy of determining the control switching timing of the lockup device.

  That is, a lockup control method for an automatic transmission according to the present invention includes an internal combustion engine having a throttle valve in an intake system, and an automatic transmission having a torque converter and a lockup device to which driving force of the internal combustion engine is inputted. The automatic transmission lock for controlling the operation of the lockup device by setting the lockup region for controlling the lockup device and the converter region up to the lockup region by at least the vehicle speed and the throttle opening degree This is an up-control method that detects the difference in rotation speed between the input speed and output speed of the torque converter and the gear ratio of the automatic transmission at the time of control transition from the converter area to the lock-up area. Lock-up device until the differential speed detected after the start of lock-up control reaches a value lower than the maximum value by a predetermined value The operating pressure for lock-up is raised, and the lock-up device is feedback-controlled so that it reaches the target differential rotational speed after the detected differential rotational speed reaches a value lower than the maximum value by a predetermined value. When it is determined that the gear ratio detected when the differential rotation speed reaches a value lower than the maximum value by a predetermined value, the start of feedback control is delayed for a predetermined time.

  According to such a configuration, after the lockup control is started, the detected differential rotational speed increases and the operating pressure for locking up the lockup device is increased until the detected value reaches a predetermined value lower than the maximum value. After the differential rotational speed reaches a value lower than the maximum value by a predetermined value, the lockup device is feedback-controlled so as to reach the target differential rotational speed. That is, the control is switched at the point in time when the detected rotational speed reaches a value lower than the maximum value by a predetermined value. When determining that the detected gear ratio has increased by a predetermined ratio when the detected differential rotation speed reaches a value that is lower than the maximum value by a predetermined value, the start of feedback control is delayed by a predetermined time, thereby switching the control Can be prevented from being erroneously determined, and a shock caused by lockup can be suppressed.

  The present invention is configured as described above, can accurately determine the control switching time of the lockup device, and can suppress a shock caused by the lockup.

The block diagram which shows the structure of the control system which implements embodiment of this invention. The flowchart which shows the control procedure of the embodiment. Action | operation explanatory drawing of the same embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a vehicle of this embodiment, that is, an automobile, is, for example, a spark ignition type multi-cylinder internal combustion engine (hereinafter referred to as an engine) 1 and a continuously variable transmission that is an automatic transmission connected to the engine 1. A machine (hereinafter referred to as CVT) 2 and an electronic control unit 3 that controls the operation of the engine 1 are mounted. Such a configuration of the automobile itself may be one that is well known in this field.

Various sensors are attached to the engine 1 in order to detect its operating state. Specifically, an idle switch, a water temperature sensor, an O ₂ sensor, a crank angle sensor, and the like (not shown) are provided, a rotation speed sensor 5 that detects the engine rotation speed, and an intake system provided for adjusting the intake air amount. A throttle opening sensor 6 for detecting the opening of the throttle valve is provided. A vehicle speed sensor 7 for detecting the vehicle speed is attached to the vehicle body, for example, on the base end side of the propeller shaft. As the configuration of each sensor itself in the engine 1 and the vehicle body, those well known in this field may be applied.

  The CVT 2 includes a torque converter 11 having a lock-up device 10 and a continuously variable transmission mechanism 12 using a belt, chain or roller on the output side of the torque converter 11. The lock-up device 10 itself may be known in this field, and controls a lock-up clutch that locks up the input side and the output side of the torque converter 11 and a hydraulic pressure for driving the lock-up clutch. And a lock-up solenoid valve 13. The lock-up device 10 operates the lock-up solenoid valve 13 when the vehicle speed falls within a set vehicle speed range, for example, when traveling at a low speed or traveling at a predetermined speed or higher, and locks the clutch clutch by hydraulic pressure of hydraulic oil. It works by connecting and locks up. The lock-up clutch in this embodiment is operated by the release side hydraulic pressure and the engagement (engagement) side hydraulic pressure, and the slip decreases as the engagement side hydraulic pressure exceeds the release side hydraulic pressure and the differential pressure between the two increases. When the engagement side hydraulic pressure becomes maximum and the release side hydraulic pressure becomes minimum, the engagement is completely completed. Therefore, in this embodiment, the hydraulic pressure of the hydraulic oil means the above-described differential pressure. In addition, the lock-up clutch is urged toward the side where the lock-up clutch is released by an elastic body such as a spring, for example, in addition to the one in which engagement and release are each performed by hydraulic pressure, and is locked up by hydraulic pressure of hydraulic oil. The thing of the structure which fastens a clutch may be sufficient.

  The CVT 2 includes a first rotation speed sensor 8 that detects the output rotation speed of the torque converter 11, a second rotation speed sensor 9 that detects the output rotation speed of the continuously variable transmission mechanism 12, and a position sensor that detects the position of the shift lever. (Not shown) is attached.

  The electronic control unit 3 is configured around a microcomputer 3a, and includes an input interface 3b, a memory 3c, and an output interface 3d. The input interface 3b receives the engine speed sensor 5, the throttle opening sensor 6, the vehicle speed sensor 7, the first engine speed sensor 8, the second engine speed sensor 9, a signal output from the position sensor, and the like. Information necessary for driving 1 and information necessary for grasping the traveling state of the vehicle are input. The output interface 3d outputs an injection signal for controlling the fuel injection valve, an ignition signal for the spark plug, a lockup signal for controlling the operation of the lockup solenoid valve 13 of the lockup device 10, and the like. Although not shown, a signal is output to the electronic control unit 3 from a sensor for detecting a gear ratio of the CVT 2 in order to control the CVT 2. As such a configuration for controlling the CVT 2, those widely known in this field can be applied.

  The memory 3c of the electronic control unit 3 stores a program for controlling the operation of the engine 1, a control program for the CVT 2, and various data for them. The lock-up control program of this embodiment sets the lock-up region for controlling the lock-up device 10 based on at least the vehicle speed and the throttle opening, and the converter region up to the lock-up region to operate the lock-up device 10. The control is to detect the difference in rotation speed between the input rotation speed and the output rotation speed of the torque converter 11 and the gear ratio of the continuously variable transmission mechanism 12 at the time of control transition from the converter area to the lockup area, and lock The operating pressure for locking up the lockup device 10 is increased until the differential rotational speed detected after the lockup control by the up device 10 is started reaches a value lower than the maximum value by a predetermined value, and the detected differential rotational speed is the maximum. After the value reaches a value lower than the predetermined value, the lockup device 10 is feedback-controlled so that the target differential rotation speed is reached It is programmed to delay the start of feedback control for a predetermined time when it is determined that the detected gear ratio has increased by a predetermined ratio when the detected differential rotation speed reaches a value lower than the maximum value by a predetermined value. ing. The control procedure of this embodiment will be described below with reference to FIG.

  This lock-up control program is used for the throttle opening degree of the lock-up control in the traveling state where the accelerator pedal is operated and the acceleration traveling is started from the traveling state in which the lock-up device is released by the deceleration traveling. Is executed when the vehicle speed exceeds a predetermined vehicle speed for the lock-up control by the acceleration, and thus when the lock-up control start condition is satisfied.

  The converter region is an operation region in which the torque converter 11 functions by maximizing the slip ratio, which is the ratio between the input rotation speed and the output rotation speed of the torque converter 11, and the lockup region is the torque converter 11 This is an operation region including a slip lockup region that functions until the slip ratio is minimized and a lockup region that functions while minimizing the slip ratio. The switching of these operation areas is performed by the operating pressure supplied to the lockup device 10. In the slip lock-up region, an operating pressure that changes at a predetermined rate of change is applied to the lock-up device 10, and the ratio between the input rotation speed and the output rotation speed of the torque converter 11 is changed at a constant rate, Sweep control for controlling the lockup device 10 to be in the lockup state, and feedback control for controlling the operating pressure so that the differential rotational speed between the input rotational speed and the output rotational speed of the torque converter 11 becomes the target differential rotational speed. Are executed by switching between and.

  First, in step S1, the input rotational speed and output rotational speed of the torque converter 11 are detected. Since the input rotational speed of the torque converter 11 is equal to the engine rotational speed, it is detected based on the signal output from the rotational speed sensor 5. The output rotational speed is output based on a signal output from the first rotational speed sensor 8.

  In step S2, a differential rotational speed is calculated from the detected input rotational speed and output rotational speed. The obtained differential rotation speed is temporarily stored in the memory 3c in order to detect the maximum value. The maximum value is determined by the differential rotational speed when the differential rotational speed changes from increasing to decreasing. If the differential rotational speed calculated this time is larger than the stored differential rotational speed, this differential rotational speed calculated this time When the differential rotational speed calculated thereafter is smaller than the differential rotational speed stored at the time of this calculation, the differential rotational speed stored at this time is set to the maximum value. The maximum value detected in this way is stored in the memory 3c separately from the differential rotation speed.

  In step S3, the lockup of the continuously variable transmission mechanism 12 is based on the output rotation speed of the torque converter 11 and the output rotation speed of the continuously variable transmission mechanism 12 detected based on the signal output from the second rotation speed sensor 9. The gear ratio after the start of control is detected.

  In step S4, it is determined whether or not the differential rotation speed has become a value lower than the maximum value by a predetermined value. That is, the maximum value stored in the memory 3c is compared with the differential rotation speed obtained this time, and it is determined whether or not the difference between the maximum value and the differential rotation speed is below a predetermined value. This point in time when the differential rotation speed becomes a value lower than the maximum value by a predetermined value is taken as a control switching point.

  In step S5, it is determined whether or not the detected gear ratio has increased by a predetermined ratio. That is, the CVT 2 controls the gear ratio so as to become the low speed side gear ratio when traveling at a low vehicle speed, and therefore is output from the output rotational speed of the torque converter 11 and the second rotational speed sensor 9. It is determined whether or not the speed ratio calculated from the output rotational speed of the continuously variable speed change mechanism 12 detected based on this signal has increased by a predetermined ratio compared to the speed ratio detected last time.

  In step S6, sweep control is executed. The sweep control is a control in which an operating pressure that changes at a predetermined change rate is applied to the lockup device 10 to change the lockup clutch from the released state to the engaged state. Therefore, during the sweep control, the lockup clutch rotates while slightly slipping.

  In step S7, the operating pressure of the hydraulic oil supplied to the lockup solenoid valve 13 is increased. Thereby, in the lockup device 10, the lockup clutch of the torque converter 11 is changed further toward the feedback control side during the sweep control, and the pull-in of the input rotation of the torque converter 11 is started.

  In step S8, it is determined whether or not a delay time has elapsed from the control switching point. The delay time is set longer as the throttle opening is higher and the vehicle speed is lower. Therefore, the delay time is set shorter as the throttle opening is lower and the vehicle speed is higher. As described above, the delay time is set based on the vehicle speed and the throttle opening at the time of the control switching point by creating a map with the throttle opening and the vehicle speed.

  In step S9, feedback control is performed so that the operating pressure supplied to the lockup solenoid valve 13 is controlled so that the detected differential rotational speed becomes the target differential rotational speed, and therefore the slip of the torque converter 11 is minimized (= 0). Run.

  Next, the operation of the embodiment will be described with reference to FIG. In addition, in the same figure, the operation | movement in the past was shown with the dashed-dotted line.

  In such a configuration, when the vehicle decelerates and re-accelerates, the lock described above is performed to perform lockup control when the throttle opening reaches a predetermined opening and the vehicle speed reaches a predetermined speed. Run the up control program. In this case, it is assumed that the engine speed increases and becomes a constant speed after the throttle opening is made constant. Until this re-acceleration is started, in other words, until lock-up control is executed (period until the engagement start time in the figure), the engine speed increases. However, the torque converter 11 operates in the converter region. The output speed of the torque converter 11 is low, and therefore the differential speed rapidly increases depending on the engine speed. Then, after the lock-up control is started (after the engagement start time in the figure), the output speed of the torque converter 11 hardly increases, and thus reaches a maximum value. Thereafter, since the CVT 2 shifts the gear ratio to the low speed side, the input rotational speed of the CVT 2 (the output rotational speed of the torque converter 11) gradually increases while the vehicle speed gradually increases.

  As described above, when the lockup control program is executed after the operation of the torque converter 11 in the converter region, the speed change ratio of the CVT 2 to the low speed side is changed during the execution of steps S1 to S4. Since the output rotational speed of the torque converter 11 gradually increases, the differential rotational speed decreases after reaching the maximum value. Here, if the differential rotational speed reaches the maximum value and does not become the value at the control switching point thereafter, the sweep control is performed from the start of the lockup control until the differential rotational speed reaches the value at the control switching point. carry out. During this time, the operating pressure is increased corresponding to the sweep control (steps S6 and S7), and the lockup device 10 is controlled in the direction in which the slip of the torque converter 11 is minimized.

  Thereafter, if the differential rotation speed becomes a value at the control switching point and the detected gear ratio increases by a predetermined ratio after the start of the lockup control (“Yes” in step S4 and step S5), the process from the control switching point When the time becomes equal to the delay time, in other words, when the sweep control is extended by the delay time, the control of the lockup device 10 is switched from the previous sweep control to the feedback control. After this, when the operating pressure is sufficiently increased by feedback control of the operating pressure so that the differential rotational speed becomes the target differential rotational speed in accordance with feedback control, therefore, the actual engagement side hydraulic pressure in the lockup clutch and the release are released. When the lockup actual differential pressure with the side hydraulic pressure rises to the vicinity of the differential pressure when the lockup clutch of the lockup device 10 is engaged, that is, fully engaged, the complete engagement of the lockup clutch is completed. In this case, needless to say, the engagement side hydraulic pressure is substantially maximized and the release side hydraulic pressure is substantially minimized.

  In this way, by switching the control from the sweep control to the feedback control by delaying from the control switching point by the delay time, the time when the lockup actual differential pressure increases to the vicinity of the differential pressure when the lockup clutch is completely engaged. Since the lock-up clutch can be completely engaged, the difference when the lock-up actual differential pressure is completely engaged at the end of the feedback control as in the conventional case shown by the one-dot chain line in FIG. The shock at the time of engagement caused by complete engagement in a state of being separated from the pressure can be suppressed.

  In the above embodiment, the CVT 2 as an automatic transmission has been described. However, a multi-stage transmission including a torque converter, a lockup device, and a gear transmission mechanism may be used.

Further, in the above-described lockup control program, the elapse of the delay time is used as the control switching condition in step S8. However, a switching condition other than the delay time may be set and combined to be used as the switching condition. . As a switching condition combined with the delay time,
(1) The rate of change of the input rotational speed of the torque converter 11 is less than a predetermined rate of change,
(2) The ratio between the input rotational speed and the output rotational speed of the torque converter 11 is less than a predetermined rotational speed ratio;
(3) The differential rotational speed exceeds a predetermined differential rotational speed,
Etc.

  These switching conditions include, for example, a combination of delay time and condition (1), delay time and conditions (1) and (2), conditions (1) and (3), and conditions (1), (2) and ( The combination with 3) may be combined as appropriate. In this case, for example, a correction coefficient is set when the condition (1) or the like is satisfied, and the actual delay time is determined by correcting the delay time using the correction coefficient, and substantially the same control as the above-described embodiment is performed. You may do.

  Thus, by setting a plurality of switching conditions, the delay time may be set shorter than that in the above-described embodiment. As a result, the time required for switching between the sweep control and the feedback control can be shortened, and the fuel consumption can be improved.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Continuously variable transmission 3 ... Electronic control unit 5 ... Rotational speed sensor 6 ... Throttle opening sensor 7 ... Vehicle speed sensor 10 ... Lock-up device 11 ... Torque converter

Claims (1)

In a vehicle comprising an internal combustion engine having a throttle valve in an intake system, and an automatic transmission having a torque converter and a lock-up device to which a driving force of the internal combustion engine is inputted,
A lockup control method for an automatic transmission that controls the operation of a lockup device by setting a lockup region for controlling the lockup device and a converter region up to the lockup region based on at least the vehicle speed and the throttle opening. And
At the time of control transition from the converter area to the lock-up area, the differential speed between the input speed and output speed of the torque converter and the gear ratio of the automatic transmission are detected,
Increase the operating pressure to lock up the lockup device until the differential speed detected after the start of lockup control by the lockup device reaches a value lower than the maximum value by a predetermined value,
After the detected differential rotation speed reaches a value lower than the maximum value by a predetermined value, the lock-up device is feedback-controlled so as to reach the target differential rotation speed,
If the gear ratio of the revolution speed difference of detected is detected when it reaches a predetermined value lower value from the maximum value to determine that it has increased a predetermined ratio delay the start of the feedback control a predetermined time, when the lock-up by the lock-up device the lock-up control method of.

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