Method for controlling drive torque during load changes

Abstract

The invention relates to a method (26) for controlling a drive torque (28) provided by a drive element (14) of a powertrain (10), which drive torque is transmittable to a driven element (20) via a torque transmission element (18), wherein during a load change process a torque transmission direction of a transmission torque (30), which is transmittable between the drive element (14) and the driven element (20) and which is applied at the torque transmission element (18), is reversed, and the load change process comprises a load change instant as a zero crossing of the transmission torque (30), the drive torque (28) being controlled in the load change process (32) in such a way that the drive torque (28) is set in relation to a dynamic transmission characteristic of a torque transmission path (17) between the drive element (14) and the driven element (20) including the torque transmission element (18) during the load change process (32), the dynamic transmission characteristic characterizing a correlation between the drive torque (28) and the transmission torque (30).

Description

Technical Field

[0001] This invention relates to a method for controlling drive torque during load changes. Background Technology

[0002] A method is described in DE 10 2010 014 193 A1, in which the transmission is tensioned by shifting gears in order to reduce the load during load changes.

[0003] A method is described in DE 10 2006 010 934 A1 in which a clutch is operated during a load change process. Summary of the Invention

[0004] The object of this invention is to perform load change processes in a protected and imperceptible manner. This is achieved by reducing the load on the powertrain caused by torque variations during the load change process.

[0005] At least one of the stated objectives is achieved through a method having the features of claim 1 for controlling the drive torque provided by the drive elements of the powertrain. Thus, load changes can be performed protectively and imperceptibly. The load occurring in the powertrain due to torque changes during load changes can be reduced. Driven elements can operate more reliably.

[0006] The powertrain can be located within the vehicle. The vehicle can be a hybrid vehicle or an electric vehicle. The drive element can be an electric motor. The torque transmission element can be a transmission and / or a clutch. The driven element can be a transmission output shaft, a differential, at least one axle, or at least one wheel.

[0007] At the moment of load change, the transmitted torque is preferably zero. The moment of load change can deviate from the zero-crossing of the drive torque. The deviation can be related to the dynamic transmission characteristics. During the load change process, from the traction operation that transmits the drive torque to the driven element to the inertial operation with the opposite torque transmission direction, the moment of load change can be after the zero-crossing of the drive torque in time.

[0008] During load changes, a change in intent can occur, through which a previously desired reversal of the torque transmission direction can be reversed or interrupted. For example, such a change in intent can occur when the accelerator pedal is moved from an operating position to an inactive position and then immediately moved back to an operating position.

[0009] In a preferred embodiment of the invention, it is advantageous that the drive torque is changed stepwise in the torque switching stages before the moment of load change during load variation, in such a way that the drive torque changes from a first torque value to at least a second torque value and from there to a third torque value. The torque difference between the first and second torque values ​​and / or between the second and third torque values ​​may be numerically half of the first torque value.

[0010] In a preferred embodiment of the invention, the drive torque is changed stepwise after the load change moment during load variation, in such a way that the drive torque changes at least to a fifth torque value starting from a fourth torque value and then to a sixth torque value starting from there in the torque switching stage. The torque difference between the fifth and fourth torque values ​​and / or between the sixth and fifth torque values ​​may be numerically half of the sixth torque value.

[0011] In a preferred embodiment of the invention, the change in drive torque is performed in more than two torque switching stages. The number of torque switching stages may be related to the initial drive torque.

[0012] The following preferred design of the invention is advantageous, wherein the time interval between at least two torque switching stages is set in relation to the dynamic transmission characteristics. Thus, the zero crossing of the drive torque can be close to the moment of load change in the transmitted torque.

[0013] In a particular design of the invention, it is advantageous that the dynamic transmission characteristics can be described by the cycle duration and the time interval can be set in relation to the cycle duration. Thus, the time delay in the transmission torque relative to the driving torque when the driving torque changes dynamically can be taken into account. The cycle duration can be related to the torsional stiffness and inertia in the torque transmission path.

[0014] In a particular embodiment of the invention, it is advantageous to set the time interval to half the cycle duration. Thus, the zero-crossing of the drive torque can be adapted to the moment of load change in the torque transmission.

[0015] In a preferred embodiment of the invention, the drive torque is changed with a predetermined torque gradient within a switching time window that includes the moment of load change during a load change. The torque gradient can be variable within a preset range during the switching time window. Alternatively, the torque gradient can be constant during the switching time window.

[0016] Alternatively, a torque window, including a zero-crossing torque for the transmitted torque, can be used. This torque window is defined by at least two preset torque values ​​for the drive torque. As long as the drive torque is within the torque window, the drive torque can change with a predetermined torque gradient. The torque gradient can be set constantly. The torque window can be preset by the switching time window and vice versa.

[0017] In a particular embodiment of the invention, it is advantageous to set the drive torque constantly from the start of the switching time window during the waiting time and / or after the end of the switching time window during the waiting time. Thus, the load change process can be performed protectedly at the moment of load change.

[0018] In an advantageous embodiment of the invention, the timing of load changes is detected in relation to changes in the rotational speed of the drive element. The start of a switching time window can be detected via a change in rotational speed. The end of a switching time window can also be detected via a change in rotational speed.

[0019] Other advantages and advantageous designs of the invention are evident from the accompanying drawings and illustrations. Attached Figure Description

[0020] The present invention is described in detail below with reference to the drawings. Detailed illustrations show:

[0021] Figure 1 A powertrain is shown for use in a specific embodiment of the invention for controlling drive torque.

[0022] Figure 2 A graph is shown when using a method for controlling drive torque according to another specific embodiment of the invention.

[0023] Figure 3 This illustration shows a partial flow diagram of a method for controlling drive torque according to another specific embodiment of the present invention. Detailed Implementation

[0024] Figure 1 A powertrain is shown for use in a specific embodiment of the invention for controlling drive torque. The powertrain 10 is, for example, located in a vehicle 12 and has a drive element 14, preferably configured as an electric motor 16. The drive element 14 can provide drive torque to drive the vehicle 12. The drive torque is transmitted to a driven element 20 via a torque transmission path 17, which includes a torque transmission element 18. The torque transmission element 18 is preferably implemented as a transmission 22 and the driven element 20 is implemented as a wheel 24.

[0025] If vehicle 12 is driven by drive element 14, the drive torque, as traction torque, is transmitted from drive element 14 to driven element 20 via torque transmission element 18. During load changes, the traction torque switches to inertial torque, which is transmitted from driven element 20 to drive element 14 via torque transmission element 18 as transmission torque 30. Load changes in the opposite direction, i.e., from inertial torque to traction torque, are also possible.

[0026] During load changes, the direction of torque transmission of the torque applied to the torque transmission element 18 is reversed.

[0027] Figure 2 A diagram is shown illustrating a method for controlling drive torque using another specific embodiment of the invention. A method 26 for controlling the drive torque 28 of the drive element can be implemented during vehicle operation and will be illustrated herein by a diagram showing the torque M in relation to time t. The vehicle is driven, for example, by a constant drive torque 28 as a traction torque until time t1. The transmission torque 30 until time t1 corresponds to the drive torque 28. From time t1, a load change process 32 is introduced, for example, because the vehicle should reduce its speed. The load change process 32 ends at time t4, from which point the drive torque 28 and the transmission torque 30 are inertial torques. The transmission torque 30 thus has a reversal of the torque transmission direction and crosses zero at the load change time t3.

[0028] If the drive torque 28 decreases at time t1 from the start of the load change process 32, for example due to a change in the acceleration preset 34 corresponding to the position of the vehicle's accelerator pedal, then the transmitted torque 30 follows the decrease with a time delay due to the dynamics of the changed drive torque 28 and the dynamic transmission characteristics of the torque transmission path between the drive element and the driven element, the torque transmission path including the torque transmission element.

[0029] In method 26, at time t1 at the start of the load change process 32, the drive torque 28 is set in relation to the dynamic transmission characteristics of the torque transmission path. Thus, the load change process 32 can be executed discreetly and safely. The drive torque 28 is changed stepwise in torque switching stages 36 at time t1 at the start of the load change process 32, in such a manner that the drive torque 28 changes from a first torque value M1 to a second torque value M2 at time t1, and then from there changes to a third torque value M3 at time t2, the third torque value still being the traction torque.

[0030] The drive torque 28 is then changed with a predetermined torque gradient 40 during the load change process 32, within a switching time window 38 that includes the load change time t3, starting from time t2, so as to perform the switching of the torque transmission direction as protectively as possible at the load change time t3. This change may be performed time-dependently with respect to the switching time window 38 and / or torque-dependently with respect to the torque window 42 that forms the switching time window 38.

[0031] The torque gradient 40 is constantly set between time t2 and time t4 within the switching time window 38, with a load change time t3 inserted between these times. Correspondingly, the torque gradient 40 is constantly set between a third torque value M3 and a fourth torque value M4 within the torque window 42. After the switching time window 38 ends at time t4, the drive torque 28 is constantly set to the fourth torque value M4 for a waiting time 44, which begins at time t4 and continues until time t5.

[0032] The drive torque 28 then changes stepwise during the load change process 32 after the load change time t3, and particularly after time t5, in such a way that the drive torque 28 changes from the fourth torque value M4 to the fifth torque value M5 starting from time t5 in the torque switching stage 36, and from there changes to the sixth torque value M6 starting at time t6.

[0033] The drive torque 28 is set by the torque switching stage 36 so that it can cross zero as much as possible even at the moment of load change when the transmitted torque 30 is zero. Here, the drive torque 28 is set in relation to the dynamic transmission characteristics of the torque transmission path by considering the period duration T that describes the dynamic transmission characteristics, which is a time change curve of the transmitted torque 30 characterized by a step response to a decrease of 48 in the drive torque 28.

[0034] During the load change process 32, two torque switching stages 36 are preferably set before the load change time t3 and two torque switching stages 36 are also set after the load change time t3. The time interval between the torque switching stage 36 at time t1 and the torque switching stage 36 at time t2 is preferably half the cycle duration T / 2. Thus, the zero crossings of the drive torque 28 and the transmitted torque 30 can be coordinated.

[0035] After the load change process 32, the time interval between the torque switching stage 36 at time t5 and the torque switching stage 36 at time t6 is preferably also set to half of the cycle duration T / 2.

[0036] The second torque value M2 corresponds specifically to half of the first torque value M1. The fifth torque value M5 corresponds specifically to half of the sixth torque value M6. The aforementioned setting of the drive torque 28 enables two-stage adjustment of the drive torque 28 in relation to the dynamic transmission characteristics of the torque transmission path.

[0037] Figure 3 A partial flow diagram of a method for controlling drive torque according to another specific embodiment of the invention is shown. Part of the flow diagram of method 26 describes possible ways to set the drive torque within a switching time window that includes moments of load change. In the first step 46, it is checked whether the applied drive torque is within a torque window, particularly between a third torque value and a fourth torque value. If this is not the case, then a reduction 48 of the drive torque to be set is achieved, for example, by using a torque level.

[0038] However, if the drive torque is within a torque window, for example, between the third and fourth torque values, then an inquiry is made regarding the current start or end of the switching time window 50. If the switching time window is already in effect, then a torque gradient limit 52 is applied to the drive torque, and the drive torque is preferably set constant.

[0039] However, if the time window starts or ends, then check 54 to see if a waiting time should be used. If the waiting time is active, then set the drive torque 56, where the drive torque is set constantly. If the waiting time ends, then cancel 58 the drive torque limitation.

[0040] Explanation of reference numerals in the attached figures

[0041] 10 Powertrain

[0042] 12 vehicles

[0043] 14 Driving Components

[0044] 16 Electric motors

[0045] 17 Torque Transmission Path

[0046] 18 Torque transmission elements

[0047] 20 Driven Components

[0048] 22. Transmission

[0049] 24 wheels

[0050] 26 methods

[0051] 28 Drive torque

[0052] 30 Transmitting torque

[0053] 32 Load Change Process

[0054] 34 Acceleration Preset

[0055] 36 Torque switching stages

[0056] 38 Switching Time Windows

[0057] 40 Torque Gradient

[0058] 42 Torque Window

[0059] 44 Waiting time

[0060] 46 steps

[0061] 48 Decrease

[0062] 50 Inquiries

[0063] 52 Restrictions

[0064] 54 Inspection

[0065] 56 Settings

[0066] 58 Cancel.

Claims

1. A method (26) for controlling a drive torque (28) provided by a drive element (14) of a powertrain (10), the drive torque being transmittable to a driven element (20) via a torque transmission element (18), wherein, during a load change, the torque transmission direction of the transmitted torque (30) transmitted between the drive element (14) and the driven element (20) and applied at the torque transmission element (18) is reversed, and the load change includes a load change moment (t3) as the zero crossing of the transmitted torque (30), the drive torque (28) during the load change... The process (32) is controlled in such a way that the drive torque (28) is set in relation to the dynamic transmission characteristics of the torque transmission path (17) including the torque transmission element (18) between the drive element (14) and the driven element (20) during the load change process (32), the dynamic transmission characteristics characterizing the correlation between the drive torque (28) and the transmission torque (30), the dynamic transmission characteristics being described by the period duration (T), the period duration characterizing the time-varying curve of the transmission torque (30) as a step response when the drive torque (28) decreases.

2. The method (26) according to claim 1. Its features are, The drive torque (28) is changed step by step in the torque switching stage (36) during the load change process (32) before the load change time (t3), in such a way that the drive torque (28) changes from a first torque value (M1) to at least a second torque value (M2) and from there changes to a third torque value (M3).

3. The method (26) according to claim 1 or 2. Its features are, The drive torque (28) changes stepwise during the load change process (32) after the load change time (t3) in such a way that the drive torque (28) changes from the fourth torque value (M4) to at least the fifth torque value (M5) and from there to the sixth torque value (M6) in the torque switching stage (36).

4. The method (26) according to claim 2 or 3. Its features are, The change in the drive torque (28) is performed in more than two torque switching stages (36).

5. The method (26) according to any one of claims 2 to 4. Its features are, The time interval is set between at least two torque switching stages (36) in relation to the dynamic transmission characteristics.

6. The method (26) according to claim 5. Its features are, The time interval can be set in relation to the duration (T) of the cycle.

7. The method (26) according to claim 6. Its features are, Set the time interval to half the period duration (T / 2).

8. The method (26) according to any one of the preceding claims. Its features are, During the load change process (32), the drive torque (28) is changed with a predetermined torque gradient (40) in a switching time window (38) including the load change time (t3).

9. The method (26) according to claim 8. Its features are, The drive torque (28) is set constantly from the start of the switching time window (38) within the waiting time (44) and / or from the end of the switching time window (38) within the waiting time (44).

10. The method (26) according to any one of the preceding claims. Its features are, The load change time (t3) is detected in relation to the rotational speed change of the drive element (14).

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