JP4924494B2 - Shift control device for continuously variable transmission - Google Patents

Description

  The present invention relates to a transmission control device for a continuously variable transmission.

  In Patent Document 1, the ultimate transmission ratio, which is the final transmission ratio of the continuously variable transmission, is calculated using the target input rotational speed with the vehicle speed and the accelerator opening as parameters, and the output rotational speed calculated from the vehicle speed. Has been.

  The ultimate speed ratio is the speed ratio that should finally be reached, and is different from the speed ratio that the actual speed ratio should take immediately. If the ultimate transmission gear ratio is immediately set to the gear ratio of the continuously variable transmission, it will immediately respond to subtle movements of the accelerator and the like, resulting in vehicle characteristics that are very difficult to drive.

  Therefore, in Patent Document 1, an intermediate value called a target gear ratio is set. In Patent Document 1, a dynamic characteristic constant (time constant) for calculating the target speed ratio and the command speed ratio is determined in accordance with the deviation between the ultimate speed ratio and the target speed ratio (previous value).

This time constant is set relatively small on the downshift side in order to shift quickly. On the upshift side, the time constant is set relatively large in order to shift slowly.
Japanese Patent No. 3211697

  In Patent Document 1, when the accelerator is continuously operated such as ON, OFF, and ON, the continuously variable transmission is downshifted during the upshift.

  At this time, the ultimate transmission ratio is in the immediate downshift direction in response to the accelerator ON operation, and the time constant for determining the target transmission ratio also immediately takes a small time constant for downshifting (fast shifting). Suddenly changes in the downshift direction. However, the continuously variable transmission is in the middle of upshifting and cannot immediately start downshifting. As a result, the deviation between the target transmission ratio and the actual transmission ratio becomes large. Therefore, if compensation control for response delay is performed by changing the feedback gain or the like according to the deviation between the target transmission ratio and the actual transmission ratio, Since the deviation between the ratio and the actual transmission ratio becomes large, a sudden downshift is performed. For this reason, an actual gear ratio overshoot is incurred just before the end of the speed change of the continuously variable transmission, and there is a risk that the effect of this overshoot will cause a shift shock and a deterioration in fuel consumption.

  Accordingly, the present invention provides a continuously variable transmission control device for a continuously variable transmission that sets the ultimate transmission ratio steplessly in accordance with the traveling conditions and controls the target transmission ratio toward the ultimate transmission ratio. Has a shift state determining means capable of detecting whether the vehicle is upshifting or downshifting, and when downshifting the continuously variable transmission during upshifting, upshifting the continuously variable transmission Downshifting the continuously variable transmission at an intermediate transmission speed that is intermediate between the upshift transmission speed used for shifting and the downshift transmission speed used for downshifting the continuously variable transmission. It is a feature.

  According to the present invention, when the continuously variable transmission during the upshift is downshifted, the deviation between the target gear ratio and the actual gear ratio can be reduced by gradual movement of the target gear ratio. The overshoot of the actual gear ratio can be suppressed, the shift shock can be suppressed, and the fuel consumption can be improved.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, a CVT (continuously variable transmission) 3 is connected to the engine 1 via a torque converter 2. The CVT 3 transmits power to the drive wheels 4 and 4 via a final reduction gear (not shown) as in a general automobile.

  The engine 1 is controlled by an engine control unit 5. The CVT 3 is controlled by the CVT control unit 6. Specifically, the drive of an actuator (not shown) included in the CVT 3 is controlled by the CVT control unit 6 to control the gear ratio of the CVT 3.

  The CVT control unit 6 includes a torque converter output shaft rotational speed sensor 7 for detecting the rotational speed of an output shaft (not shown) of the torque converter 2, a vehicle speed sensor 8 for detecting the vehicle speed, an accelerator opening (accelerator pedal position). A signal from an accelerator opening sensor 9 that detects the amount of depression) is input.

  In the present embodiment, as shown in FIG. 2, the ultimate transmission ratio, which is the final transmission ratio of the CVT, is the output shaft calculated from the target input shaft rotational speed using the vehicle speed and the accelerator opening as parameters, and the vehicle speed. It is calculated using the rotation speed.

  Further, as shown in FIG. 3, the CVT control unit 6 calculates a target speed ratio for controlling the CVT 3 toward the ultimate speed ratio. The CVT control unit 6 determines a dynamic characteristic constant (time constant) for calculating the target speed ratio and the command speed ratio in accordance with the deviation between the ultimate speed ratio and the target speed ratio (previous value).

This time constant has characteristics as shown in FIG. That is, on the downshift side, the time constant is set to be relatively small in order to shift quickly. This is a driving force increasing direction with respect to the accelerator ON, because the reduction ratio needs to quickly follow. On the upshift side, the time constant is set relatively large in order to shift slowly. This is because the engine torque decreases in the direction of decreasing driving force and follows the accelerator OFF, so that the tracking of the reduction ratio may be slow. Further, CVT control unit 6, when the difference between the attained gear ratio and the target speed ratio is negative CVT3 is downshift, when the positive is judged to be in an upshift.

  Further, as shown in FIG. 5, the CVT 3 is shifted by operating the actuator described above with respect to the target gear ratio. At this time, compensation control for response delay is performed by changing the F / B gain or the like according to the deviation between the target gear ratio and the actual gear ratio.

  And in 1st Embodiment of this invention, when the driver | operator performs continuous operation of ON, OFF, and ON of an accelerator and the situation where a CVT3 is downshifted during an upshift occurs, the CVT3 is upshifted. The CVT 3 is downshifted at an intermediate speed that is intermediate between the upshift speed used for the downshift and the downshift speed used for the downshift of the CVT3. That is, the time constant used when down-shifting the CVT 3 during the up-shift and the time constant used when down-shifting the steady-state CVT 3 are separately used. More specifically, the time constant used for downshifting the CVT 3 during the upshift is set to be larger than the time constant used for downshifting the CVT 3 in the steady state. Furthermore, the time constant used when downshifting CVT3 during upshifting, the time constant used when upshifting steady state CVT3, and the time constant used when downshifting steady state CVT3, Set to an intermediate value.

  FIG. 6 is a comparative example of the first embodiment of the present invention described above. When a situation occurs in which the CVT 3 is downshifted during upshifting, the time constant used for downshifting the steady state CVT3 is shown. It is a timing chart which shows the behavior of various parameters at the time of using.

  In section A, an upshift is performed as the accelerator changes from ON to OFF. The target gear ratio indicated by the characteristic line b slowly decreases according to the upshift time constant. The actual gear ratio indicated by the characteristic line c decreases slightly later than that. Therefore, the time of the section A is generally longer, and the probability of depressing the accelerator during that time increases.

In the section B, the arrival speed change ratio indicated by the characteristic line a increases in synchronization with the accelerator fluctuation as the accelerator changes from OFF to ON, but the upshift is still continued in this section (the arrival speed change ratio and Until the actual gear ratio is met).

  In the section C, the ultimate transmission ratio and the target transmission ratio are reversed, and the downshift determination is performed. The time constant for determining the target gear ratio is calculated to be small for downshifting (fast shifting). The target gear ratio turns in the downshift direction, but does not directly exceed the actual gear ratio, so the upshift section continues.

  In section D, the target gear ratio and the actual gear ratio are reversed, and the actuator issues an upshift command. Here, since the actual speed ratio cannot be responded directly, a delay occurs in the actual speed ratio. In addition, in order to make up for this delay, compensation control for the response delay acts, and a sudden downshift occurs.

  In the section E, an overshoot of the actual gear ratio occurs, and a shift shock and deterioration of fuel consumption occur.

  On the other hand, in the first embodiment of the present invention, as shown in FIG. 7, when a situation occurs in which the CVT 3 is downshifted during the upshift, the time constant used when downshifting the steady state CVT3 is obtained. The target speed ratio indicated by the characteristic line d gradually changes, and the actual speed change indicated by the target speed ratio indicated by the characteristic line d and the characteristic line e. The deviation from the ratio can be reduced, and the overshoot of the actual transmission ratio indicated by the characteristic line e can be prevented. Note that characteristic lines a to c in FIG. 7 show the ultimate transmission ratio, the target transmission ratio, and the actual transmission ratio in FIG. 6 for reference.

  FIG. 8 is a flowchart showing the flow of control in the first embodiment described above.

  In step (hereinafter simply referred to as S) 10, the transmission mode of CVT 3 is determined. If it is determined that CVT is upshifting, the process proceeds to S11, and if it is determined that CVT is downshifting, S12 is performed. Proceed to

  In S11, when calculating the target gear ratio, a time constant for upshift is used. More specifically, since a relatively large time constant is used, the shift speed becomes relatively slow.

  In S12, it is determined whether the downshift is a downshift from the steady state or a downshift during the upshift. If the downshift is from the steady state, the process proceeds to S13, and the downshift during the upshift is performed. If there is, the process proceeds to S14.

  In S13, when the target gear ratio is calculated, the downshift time constant is used. Specifically, since a relatively small time constant is used, the speed change speed becomes relatively fast.

  In S14, the target gear ratio is calculated using a time constant for downshift during upshift. More specifically, a time constant that is larger than the time constant used when downshifting the CVT 3 in the steady state and smaller than the time constant for upshifting is used, and the shift speed is the same as that during upshifting and downshifting. Intermediate speed.

  In the first embodiment described above, the time constant for downshifting during the upshift is a constant value. However, the time constant may be gradually decreased toward the time constant used when downshifting the CVT 3 in the steady state. Is possible. In other words, in the first embodiment described above, the shift speed at the time of downshift during the upshift is a constant value, but gradually toward the shift speed for downshift when the CVT 3 in the steady state is downshifted. It is also possible to increase.

  Next, a second embodiment of the present invention will be described. In the second embodiment, when a situation occurs in which the CVT 3 is downshifted during the upshift, the actual speed ratio at that time is replaced with the target speed ratio, and the speed change speed of the CVT 3 becomes zero. The CVT 3 is downshifted at the downshift speed used when the CVT 3 is downshifted.

Oite to the second exemplary embodiment also, in the case of downshift CVT3 in upshifting, it is possible to reduce the deviation between the target speed ratio and the actual gear ratio, the overshoot of the actual speed ratio is suppressed Thus, the shift shock can be suppressed and the fuel consumption can be improved.

  FIG. 9 is a flowchart showing a control flow in the second embodiment.

  In S20, the shift mode of CVT3 is determined. If it is determined that CVT is upshifting, the process proceeds to S21, and if it is determined that CVT is downshifting, the process proceeds to S22.

  In S21, when calculating the target gear ratio, a time constant for upshifting is used. More specifically, since a relatively large time constant is used, the shift speed becomes relatively slow.

  In S22, it is determined whether the downshift is a downshift from a steady state or a downshift during an upshift. If the downshift is from a steady state, the process proceeds to S25, and the downshift during the upshift is performed. If there is, the process proceeds to S23.

  In S23 and S24, the actual gear ratio is replaced with the target gear ratio, the CVT gear shift speed is set to zero, and then the process proceeds to S25.

  In S25, when the target gear ratio is calculated, it is calculated using a time constant for downshifting. Specifically, since a relatively small time constant is used, the speed change speed becomes relatively fast.

  In S14, the target gear ratio is calculated using a time constant for downshift during upshift. More specifically, a time constant that is larger than the time constant used when downshifting the CVT 3 in the steady state and smaller than the time constant for upshifting is used, and the shift speed is the same as that during upshifting and downshifting. Intermediate speed.

  The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.

  (1) In a continuously variable transmission shift control device that sets a target transmission ratio steplessly in accordance with traveling conditions and controls a target transmission ratio toward the ultimate transmission ratio, the continuously variable transmission is upshifted In the case of downshifting the continuously variable transmission during upshifting, when the upshifting of the continuously variable transmission is carried out The continuously variable transmission is downshifted at an intermediate speed that is intermediate between the upshift speed to be used and the downshift speed to be used when the continuously variable transmission is downshifted.

  This allows the deviation between the target gear ratio and the actual gear ratio to be reduced by slowing down the movement of the target gear ratio when the continuously variable transmission during the upshift is downshifted. Overshoot is suppressed, shift shock can be suppressed, and fuel consumption can be improved.

  (2) In the transmission control device for a continuously variable transmission according to (1), the intermediate transmission speed is set to gradually increase toward the downshift transmission speed.

  (3) In a continuously variable transmission shift control device for setting a target transmission ratio steplessly in accordance with traveling conditions and controlling a target transmission ratio toward the ultimate transmission ratio, the continuously variable transmission is upshifted In case of having a shift state judging means capable of detecting whether the vehicle is in a downshift or downshifting, and downshifting the continuously variable transmission during the upshift, the actual gear ratio at that time is determined as the target gear ratio. After the shift speed of the continuously variable transmission becomes zero, the continuously variable transmission is downshifted at the downshift speed used when the continuously variable transmission is downshifted.

  This reduces the deviation between the target gear ratio and the actual gear ratio when down-shifting a continuously variable transmission that is upshifting, so that overshooting of the actual gear ratio is suppressed and shift shock is suppressed. In addition, the fuel consumption can be improved.

The system block diagram of the control apparatus of the continuously variable transmission which concerns on this invention. The block diagram for calculating a reaching gear ratio. The block diagram for calculating a target gear ratio. Characteristic diagram showing time constant map The block diagram for calculating an actual gear ratio. The timing chart which shows the behavior of the various parameters of a comparative example. The timing chart which shows the behavior of the various parameters in 1st Embodiment of this invention. The flowchart which shows the flow of control in 1st Embodiment of this invention. The flowchart which shows the flow of control in 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Torque converter 3 ... CVT
6 ... CVT control unit

Claims (2)

In a continuously variable transmission shift control device for setting a target transmission ratio steplessly in accordance with driving conditions and controlling a target transmission ratio toward the ultimate transmission ratio,
Shift state determining means capable of detecting whether the continuously variable transmission is upshifting or downshifting;
When downshifting the continuously variable transmission during an upshift, the upshift speed used when the continuously variable transmission is upshifted and the downshift used when the continuously variable transmission is downshifted A continuously variable transmission shift control device, wherein the continuously variable transmission is downshifted at an intermediate shift speed that is intermediate between the shift speed and the speed.   2. The transmission control device for a continuously variable transmission according to claim 1, wherein the intermediate transmission speed is set to gradually increase toward the downshift transmission speed.

Images