Method for operating a power-split transmission

Abstract

A method for operating a power-split transmission with at least two driving ranges and a continuously variable power branch, wherein switching from a first driving range to a second driving range is performed by actuating a first torque-transmitting, disengageable clutch in the opening direction until this disengageable clutch no longer transmits torque, and by actuating a second, engaging clutch in the closing direction until this engaging clutch transmits the torque, wherein the gear ratio in the continuously variable power branch of the power-split transmission is then kept constant during the driving range change, characterized in that if at least one driving requirement changes above a previously defined threshold during the driving range change, the switching from the first driving range to the second driving range is interrupted and the first clutch is actuated in such a way thatthat the transmission returns to the first driving range, and the ratio of the continuously variable power branch can be changed again.

Description

The invention relates to a method of operating a power split transmission of the type defined in more detail in the preamble of claim 1.Power split transmissions of the generic type have a continuously variable power branch, which can be designed, for example, as a hydrostatic power branch or an electrical power branch, and a mechanical power branch, which are summed via a summing transmission. In addition, these power split transmissions of the type in question have at least two driving ranges which can be shifted by means of clutches and within which the output rotational speed of the power split transmission can be varied continuously.DE102006055724A1 discloses a hydrostatic-mechanical power split transmission of the generic type in which the shift from a first driving range into a second driving range takes place at synchronous rotational speed in order to achieve a good shift quality without shift jerks. During the shift from one driving range to the other driving range, the transmission ratio in the continuously variable power branch is kept constant, so that the synchronization point is maintained during the shift. DE 196 41 723 A1 relates to a power split transmission with hydrostatic or mechanical continuously variable converter and a converter bypass which can be shifted at a plurality of transmission points. DE 10 2012 218 974 A1 relates to a method for shifting between transmission ranges of a power split transmission.The object of the present invention is to create a method for operating a power split transmission, by means of which a vehicle driver receives reproducible, comprehensible reactions of the vehicle to his specifications.The invention is achieved by a generic method also having the characterizing features of the main claim.The invention is based on the finding that a power split transmission keeps the transmission ratio constant in the continuously variable power branch until a shift from one range to the next range is completed. However, if the request of the vehicle driver changes precisely during the change from one range to the next range, for example, in that the vehicle driver suddenly releases the accelerator pedal and additionally actuates the service brake, for example, the vehicle driver awaits that the transmission changes the transmission ratio promptly in order thus to brake the vehicle. However, since a transmission ratio change is possible only after completion of the range shift, the method according to the invention includes the termination of a range shift depending on changed driving requirements.In order to illustrate the termination of a range shift in more detail, a range shift is first described which is carried out completely without termination. The range shift described is described as an upshift, for example from a first driving range into a second driving range, wherein a downshift, for example from the second into the first driving range, takes place in the reverse sequence.From data of an accelerator pedal or of a signal indicating another acceleration request, an electronic control unit recognizes that the driver request provides a further acceleration of the vehicle. From data of the current actual dynamics or from data of the current setpoint dynamics and the respective transmission ratio to the synchronization point, the electronic control unit calculates the time span until the synchronous rotational speed for changing the driving range is reached. Depending on this time duration, if further boundary conditions are fulfilled, the range clutch to be engaged is pre-filled with hydraulic fluid and subsequently actuated in the closing direction until it is closed. Upon closing the engaged range clutch, the electronic control unit recognizes that the drive range change is active. As long as the drive range change is active, the transmission ratio of the continuously variable power branch is first placed in the synchronization point and then kept active there. This maintaining of the transmission ratio constant is maintained until the electronic control unit recognizes that the drive range change is no longer active. The change of driving range is no longer active when a predefined time period has elapsed after the clutch to be disengaged is fully actuated in the opening direction. The time duration for the engagement of the clutch to be engaged is referred to as the first section. After a predefined time period has elapsed, during which the clutch to be engaged and the clutch to be disengaged are both actuated in the closing direction, the clutch to be disengaged is actuated in the opening direction. If the clutch to be disengaged is actuated in the opening direction, this is referred to as the second section of the shift. If the change in driving range is concluded and the transmission ratio is still in the region of the synchronization point, a further change in driving range is blocked for a defined time in order to prevent a continuous shift back and forth, so-called pendulum shifts. This time range is also referred to as a third section.If the driving demand now changes over a predefined threshold during this change in driving range, in which the transmission ratio of the continuously variable power branch is necessarily kept constant, the change in driving range is not completed but is discontinued and, depending on the section in which the change in driving range is located, the clutch to be disengaged is either not opened at all or, if it is already actuated in the opening direction, is closed again in order to leave the time window of the active change in driving range as quickly as possible in order to be able to change the transmission ratio of the continuously variable power branch again. The electronic control unit recognizes that a change in the driving request is present if during the shift from the first driving range into the second driving range either a reversing request is recognized or an angle of an accelerator pedal is changed via a predefined value and / or an internal combustion engine which drives the transmission exceeds a predefined depression and / or an external or internal output rotational speed request exceeds a predefined value and / or a setpoint gradient of the transmission exceeds a predefined value and / or a high-pressure control exceeds a predefined value and / or a driving range request or a driving range limitation, for example only driving range 1), is requested and / or the thrust control exceeds a predefined value.Further features can be seen from the description of the figures.The following are shown: FIG. 1 shows a time diagram of a complete range shift from a first driving range to a second driving range as an upshift; FIG. 2 shows a break of the driving range shift within the first section; FIG. 3 shows a change of the travel range in the second section; FIG. 4 shows a change of the travel range in the third section; and FIG. 5 shows a termination of the change in the driving range in the first section by detecting a setpoint output rotational speed change.FIG. 1 : Figure 1:The ordinate shows the course of the hydraulic pressure with which the clutch to be engaged and the clutch to be disengaged are acted. At this time, the clutch is in the closed state at high pressure and in the open state at low pressure. Closed state means that the clutch can transmit torque. The open state means that the clutch cannot transmit torque. The time profile is shown on the abscissa. Before the first section 1, the clutch to be engaged is pre-filled with hydraulic fluid, so that the pressure of the clutch 4 to be engaged is increased with respect to its base level. Likewise, before the first section 1, the pressure of the clutch 5 to be disengaged is at its maximum level or at a level at which the clutch to be disengaged is still closed in a force-locking manner. The pressure level does not necessarily have to correspond to the maximum pressure. At the beginning of the first section 1, the pressure of the clutch 4 to be engaged is increased to its closing level, whereby the clutch to be engaged is actuated in the closing direction. At the same time, the signal Drive range change is set active 6, which remains active until the end of the second section 2. While the signal Drive range change is actively set 6, the transmission ratio of the continuously variable power branch remains constant. At the end of the first section 1 and the beginning of the second section 2, the pressure of the clutch 5 to be disengaged is reduced, so that it is actuated in the opening direction. If the pressure of the clutch 5 to be disengaged is at its low level and a certain safety time period has elapsed, so that it is ensured that this clutch is safely in the open state, the end of the second section is reached. The transmission ratio of the continuously variable power branch no longer has to be kept constant after the end of the second section or the end of the signal Drive range change active 6. However, if the rotational speed continues to remain in a previously defined range near the synchronization point, the transmission is located in the third section 3.FIG. 2 : Figure 2:Except for the termination of the driving range, the numbering and description is identical to the representation in FIG. 1. If the driving request changes in the first section, so that the electronic control unit recognizes a termination intention and the shift for changing the driving range is still in the first section 1, a driving range change termination 7 takes place, in that the pressure of the clutch to be engaged is immediately reduced back to the base level and, when the base level and a safety time period are reached, the signal driving range change is actively switched off 6 again, so that a transmission ratio adjustment is immediately possible. Thus, the driving range change is significantly shortened, and the driving request can be immediately implemented. The vehicle driver thus receives a direct conversion of his request and thus a direct vehicle reaction.FIG. 3 : 3 : Figure 3 :If the electronic control unit recognizes that the vehicle driver wishes to carry out a reversal, for example, within the change in driving range, or the driving request changes in such a way that a break-off speed 7 is recognized and the change in driving range is in the second section 2, the old change in driving range 6 is broken off and the pressure of the clutch 5 to be disengaged is immediately increased again and the clutch to be disengaged is thereby immediately closed again via a shortened shift, as a result of which the signal Change in driving range 6 is again output actively and, after the expiration thereof, the transmission ratio can be adjusted again immediately.FIG. 4 : Figure 4: Figure 4:If the electronic control unit recognizes that an abort of the drive range change is desired and the vehicle is still in the third section, i.e. the rotational speed is still in the range of the synchronous rotational speed, but the previous drive range change is completely concluded, the shift locking time for pendulum prevention is canceled and the clutch to be disengaged is immediately filled again with pressure and is re-shifted via a shortened or even via a normal shift. As a result, the signal Drive range change active 6 is output again. A circuit as already described above takes place. As soon as the signal Drive range change active 6 is no longer output, the transmission can be implemented as recognized by the driver request. The vehicle thus responds more quickly, since a fast shift can be initiated as soon as the break is detected. This cancels the minimum time in the new driving range.FIG. 5 : 5 :The desired output rotational speed 8 is also shown as a termination criterion in this illustration. If the setpoint output rotational speed is smaller by an amount during an upshift, it is recognized that the driver does not wish to accelerate further and thus the shift is intended to be aborted. The setpoint output rotational speed can either be determined directly from the accelerator pedal, but it is also possible to obtain this information via an external variable, such as RTOS, for example. As long as the target output speed increases in one direction, nothing is stored, but when a change in the target output speed occurs, this value 10 is stored. If the setpoint output rotational speed 8 continues to move in the other direction, the difference 9 begins to increase further. If this difference 9 exceeds a specific value, the break detection becomes active and the change in driving range is broken off. Depending on which driving conditions are present, a rapid downshift or a normal downshift can take place.Reference numerals denote reference numerals1 First section 2 Second section 3 Third section 4 Pressure of the clutch 5 to be engaged Pressure of the clutch 6 to be disengaged Drive range change actively 7 Drive range change abort 8 Setpoint output rotational speed 9 Difference between maximum value and minimum value 10 Maximum value of the required setpoint output rotational speed 8 during a range change 11 Flag indicating that a shift abort has been detected

Claims

Method for operating a power split transmission having at least two driving ranges and a continuously variable power branch, wherein a shift is made from a first driving range to a second driving range by actuating a first torque-transmitting clutch to be disengaged in the opening direction until this clutch to be disengaged no longer transmits torque and actuating a second clutch to be engaged in the closing direction until this clutch to be engaged transmits the torque, wherein the transmission ratio in the continuously variable power branch of the power split transmission is then kept constant during the change of the driving range, characterized in that, if at least one driving request changes above a predefined threshold during the change of the driving range, the shift from the first driving range to the second driving range is interrupted and the first clutch is actuated in such a way that the transmission returns to the first driving range, and the transmission ratio of the continuously variable power branch can be changed again.Method according to Claim 1, characterized in that there is a change in the driving demand if a reversal demand is detected during the shift from the first driving range into the second driving range and / or an angle of an accelerator pedal is changed via a predefined value and / or an internal combustion engine which drives the transmission exceeds a predefined depression and / or an external or internal output rotational speed demand exceeds a predefined value and / or a setpoint gradient of the transmission exceeds a predefined value and / or a high-pressure control exceeds a predefined value and / or a driving range demand and / or a driving range limitation, for example only driving range 1, is requested and / or the thrust control exceeds a predefined value.Method according to Claim 1, characterized in that, in the case of a complete upshift from the first driving range into the second driving range, after the clutch to be engaged has been pre-filled, three sections are passed through one after the other, wherein in a first section the clutch to be engaged is actuated in the closing direction and thereby transmits torque, in a second section the clutch to be disengaged is actuated in the opening direction until virtually no torque is transmitted by this clutch to be disengaged and in a third section the change from the first driving range into the second driving range is concluded and the transmission ratio is still in a range of the synchronization point, wherein the transmission ratio of the transmission is kept virtually constant within the first and second sections.Method according to Claim 3, characterized in that, if the change in the at least one driving request above the predefined threshold within the first section is present, the clutch to be engaged is actuated in the opening direction, as a result of which the shift is aborted and, after a predefined time period, the transmission ratio in the continuously variable power branch is changed.Method according to either of Claims 3 and 4, characterized in that, if the change in the at least one driving request above the predefined threshold is present within the second section, the clutch to be disengaged is actuated in the closing direction and the clutch to be engaged is actuated in the opening direction, as a result of which the shift is aborted and the transmission ratio is adjusted after a predefined time period.Method according to one of Claims 3 to 5, characterized in that, if the change in the at least one driving request above the predefined threshold is present within the third section, the clutch to be disengaged is actuated in the closing direction and the clutch to be engaged is actuated in the opening direction, as a result of which the shift is aborted and the transmission ratio is adjusted after a predefined time period.Method according to one of the preceding claims, characterized in that the method is used for the termination of an upshift and / or for the termination of a downshift.

Images