METHOD FOR SYNCHRONIZING TWO DRIVE ELEMENTS OF A POWERTRAIN OF A MOTOR VEHICLE, AND POWERTRAIN FOR A MOTOR VEHICLE

Abstract

A method for synchronizing a first drive element rotatable about an axis of rotation with a second drive element rotating about the axis of rotation at a target speed, of a powertrain of a motor vehicle, in which a synchronizing force is exerted on a synchronizing unit by an actuator. A speed, at which the first drive element rotates about the axis of rotation is adapted by the synchronizing unit to the target speed. The synchronizing force is increased during a first time span, so that the speed approaches the target speed. The synchronizing force is continuously reduced during a second time span following the first time span, before the speed corresponds to the target speed.

Claims

1-10 (canceled)

11. A method for synchronizing a first drive element rotatable about an axis of rotation with a second drive element rotating about the axis of rotation at a target speed, of a powertrain of a motor vehicle, comprising: a synchronizing force is exerted on the synchronizing unit by an actuator, whereby a speed, at which the first drive element rotates about the axis of rotation, is adapted by the synchronizing unit to the target speed, wherein the synchronizing force is increased during a first time span, so that the speed approaches the target speed, wherein the synchronizing force is continuously reduced during a second time span following the first time span, before the speed corresponds to the target speed.

12. The method as claimed in claim 11, wherein the synchronizing force is continuously reduced during the second time span in such a way that the speed further approaches the target speed.

13. The method as claimed in claim 12, wherein the synchronizing force is continuously reduced during the second time span in such a way that the speed further approaches the target speed until the speed corresponds to the target speed.

14. The method as claimed in claim 11, wherein the synchronizing force is continuously reduced during the second time span, before a mechanical unlocking phase begins, during which a synchronizer ring enables a sliding collar for a displacement of the sliding collar along the axis of rotation, whereupon the sliding collar is displaced along the axis of rotation in relation to the synchronizer ring and is thus engaged with corresponding gear teeth, to thus couple the drive elements in a formfitting and friction-locked manner with one another via the gear teeth and the sliding collar.

15. The method as claimed in claim 11, wherein the synchronizing force is increased during a third time span following the second time span.

16. The method as claimed in claim 15, wherein the synchronizing force is increased linearly during the third time span.

17. The method as claimed in claim 11, wherein as the first drive element, a gear wheel of a transmission is synchronized with the second drive element.

18. The method as claimed in claim 17, wherein the gear wheel is synchronized with the second drive element during a gear change of the transmission.

19. The method as claimed in claim 11, wherein a shaft, which is driven by at least one wheel of the motor vehicle, is used as the second drive element.

20. A powertrain for a motor vehicle, comprising: a first drive element rotatable about an axis of rotation, having a second drive element rotatable about the axis of rotation, having a synchronizing unit for synchronizing the first drive element with the second drive element, having an actuator, by which a synchronizing force can be exerted on the synchronizing unit to thus adapt a speed of the first drive element to a target speed of the second drive element by the synchronizing unit, and having an electronic processing unit, which is designed to control the actuator to thus set the exertion of the synchronizing force on the synchronizing unit, wherein the electronic processing unit is designed to control the actuator in such a way that: the synchronizing force increases during a first time span, so that the speed approaches the target speed; and the synchronizing force is continuously reduced during a second time span following the first time span, before the speed corresponds to the target speed.

Description

[0031] The single FIGURE of the drawing shows diagrams to illustrate a method according to the invention for synchronizing two drive elements of a powertrain of a motor vehicle.

[0032] A method for synchronizing a first drive element rotatable about an axis of rotation with a second drive element rotating about the axis of rotation at a target speed, of a powertrain of a motor vehicle, in particular an automobile, for example, a passenger automobile, will be explained hereafter on the basis of the FIGURE. In the scope of the method, for example, the second drive element rotates at the target speed about the axis of rotation, so that the second drive element has the target speed. In this case, the target speed is different from 0 and/or has a value different from 0.

[0033] The first drive element is stationary with respect to a rotation about the axis of rotation, for example, so that the first drive element initially does not rotate about the axis of rotation, for example. Furthermore, it is conceivable that the first drive element rotates at a speed, in particular at a speed different from 0, about the axis of rotation, wherein the speed is different, for example, from the target speed. In particular the speed is, for example, less than the target speed, so that, for example, the first drive element is accelerated in the scope of the synchronizing, and so that the speed of the first drive element is increased.

[0034] The FIGURE shows a plurality of diagrams 10, 12, 14, and 16, on the respective ordinate 18 of which the time t is plotted. The method is applied, for example, in a transmission of the powertrain. The powertrain comprises in this case the transmission and at least one drive motor, which can provide torques for driving at least one wheel of the motor vehicle and thus for driving the motor vehicle as a whole. The respective torque provided by the drive motor is transmitted, for example, via the transmission and at least one shaft to the at least one wheel, whereby the wheel can be driven by means of the torque. The method is carried out in particular during a drive of the motor vehicle, wherein the motor vehicle is driven along a roadway during the drive. In this case, the at least one wheel rolls on the roadway.

[0035] The transmission has, for example, a plurality of gears which can be engaged and/or shifted. A shifting and/or a gear change of the transmission is thus to be understood to mean that a first of the gears is disengaged and a second of the gears is engaged. In this case, for example, the first drive element is a gear wheel of the second gear, wherein the second drive element is, for example, the above-mentioned shaft, via which the wheel is drivable. In particular, the wheel is driven via the shaft by the drive motor in a traction operation of the drive motor. For this purpose, a torque flow takes place from the drive motor via the transmission to the shaft and via this shaft to the wheel. In the event of a gear change, for example, this torque flow between the drive motor and the shaft, in particular between the drive motor and the transmission, is interrupted, for example, by a starting element such as a friction clutch being opened. The shaft is then driven by the at least one wheel, for example, so that the shaft (second drive element) rotates at the target speed about the axis of rotation.

[0036] Since initially the first gear is or was, respectively, engaged and the first gear is disengaged and the second gear is engaged in the scope of the gear change, for example, the first drive element formed as the gear wheel of the second gear does not rotate about the axis of rotation, or the first drive element rotates at a lower speed than the target speed about the axis of rotation.

[0037] In the method for synchronizing the drive elements, a synchronizing force is exerted on a synchronizing unit by means of an actuator, whereby the speed at which the first drive element rotates about the axis of rotation is adapted by means of the synchronizing unit to the target speed. This means that a difference between the speed of the first drive element and the target speed of the second drive element is at least reduced, in particular canceled out. Since, for example, the speed is less than the target speed, the first drive element is accelerated by the second drive element via the synchronizing unit, whereby the speed of the first drive element is increased and the target speed is thus approached.

[0038] The synchronizing unit is designed, for example, as a friction synchronizing unit. In this case, the synchronizing unit comprises, for example, a carrier connected in a rotationally-fixed manner to the shaft, which is referred to as a synchronizer hub. The synchronizer hub has, for example, first gear teeth. Furthermore, the synchronizing unit comprises a sliding collar, which is partially arranged on the synchronizer hub and is displaceable along the axis of rotation in relation to the synchronizer hub. In this case, the sliding collar has second gear teeth, which are at least partially engaged with the first gear teeth. Furthermore, the synchronizing unit comprises, for example, at least one synchronizer ring, which has a first friction cone. Moreover, the synchronizing unit comprises a clutch body, which is connected, for example, in a rotationally-fixed manner to the gear wheel and has a second friction cone corresponding to the first friction cone. The first friction cone and the second friction cone form a cone friction clutch, which can be opened and closed by displacing the synchronizer ring along the axis of rotation in relation to the clutch body. In this case, for example, the synchronizer ring has, for example, third gear teeth, wherein the clutch body has fourth gear teeth. Since the sliding collar engages via its second gear teeth in the first gear teeth of the synchronizer hub, and since the synchronizer hub is coupled in a rotationally-fixed manner to the second drive element, the sliding collar is driven via the synchronizer hub and at the same time via the first gear teeth and the second gear teeth by the second drive element, which is driven by the at least one wheel. Therefore, the synchronizer hub and the sliding collar also rotate at the target speed about the axis of rotation. Before the synchronization, the clutch body and the first drive element are not coupled to the second drive element, so that they can rotate in relation to one another.

[0039] The synchronizer ring is, for example, at least indirectly coupled to the synchronizer hub, so that the synchronizer hub carries along the synchronizer ring. This means that the synchronizer ring is rotated via the synchronizer hub by the second drive element about the axis of rotation, so that the synchronizer ring also rotates at the target speed about the axis of rotation.

[0040] In the scope of the gear change, the drive elements are synchronized by exerting the synchronizing force on the synchronizing unit and in this case in particular on the sliding collar by means of the actuator. By means of the synchronizing force, the sliding collar and, at least indirectly via this, the synchronizer ring are displaced in the direction of the gear wheel and thus in the direction of the clutch body, which is connected in a rotationally-fixed manner to the gear wheel, along the axis of rotation, so that the first friction cone comes into contact with the second friction cone. Thus, for example, the clutch body and the gear wheel are at least approximately brought to the speed of the synchronizer ring. This takes place in particular in the scope of a pre-synchronization. In other words, the difference between the speed and the target speed is at least reduced by the pre-synchronization. If the sliding collar is displaced further, for example, in particular by means of the synchronizing force, in the direction of the gear wheel and the clutch body, the sliding collar, in particular its second gear teeth, thus comes into contact with the synchronizer ring, in particular with the third gear teeth. In this way, the synchronizer ring is pressed by means of the sliding collar particularly strongly against the clutch body, so that the first friction cone and the second friction cone are pressed together. In this way, for example, a friction cone clutch formed by the friction cones is closed or closed further, respectively. Firstly, for example, the synchronizer ring locks the sliding collar against a displacement of the sliding collar along the axis of rotation in the direction of the clutch body, in particular as long as the difference between the speed and the target speed has not yet been sufficiently reduced or canceled out.

[0041] If the difference between the speed and the target speed has been sufficiently reduced, in particular canceled out, so that, for example, the second drive element and thus the sliding collar have the same speed as the clutch body and thus the gear wheel, the synchronizer ring enables the sliding collar for its displacement along the axis of rotation along the clutch body, since then the synchronizer ring can be pivoted in relation to the sliding collar and in relation to the clutch body about the axis of rotation, by the sliding collar being displaced along the axis of rotation in the direction of the clutch body. Thus, for example, the second gear teeth of the sliding collar can be pushed through the third gear teeth of the synchronizer ring, in particular through tooth gaps of the third gear teeth of the synchronizer ring and in particular can be moved or pushed, respectively, into engagement with the fourth gear teeth of the clutch body. The second gear teeth of the sliding collar then engages both in the first gear teeth of the synchronizer hub and also in the fourth gear teeth of the clutch body, so that the second drive element is coupled in a formfitting and thus rotationally-fixed manner with the first drive element via the sliding collar and the clutch body.

[0042] The enabling of the sliding collar for its displacement along the axis of rotation in the direction of the clutch body is also referred to as a mechanical unlocking phase, unlocking procedure, mechanical unlocking procedure, unlocking, or mechanical unlocking, so that the synchronizing unit is designed, for example, as a locking synchronizing unit. The sliding collar can be interconnected by the unlocking, which is to be understood to mean that the sliding collar or its second gear teeth, respectively, is/are engaged with the fourth gear teeth.

[0043] To make the described synchronization of the drive elements and thus the gear change particularly comfortable and in particular smooth for occupants of the motor vehicle, it is provided in the method that the synchronizing force is increased during a first time span, so that the speed of the first drive element approaches the target speed of the second drive element. Before the speed corresponds to the target speed, in particular chronologically before the mechanical unlocking force, the synchronizing force is continuously reduced during a second time span following the first time span.

[0044] In the diagram 10, the target speed is identified by 20 and is illustrated by means of a dashed line. The target speed is also referred to as the synchronizing target speed. Furthermore, a curve 22 is plotted in the diagram 10, which illustrates the speed of the first drive element, in particular a time curve of the speed of the first drive element. Furthermore, a point in time t1 is plotted in the diagrams 10, 12, 14, and 16, at which the mechanical unlocking phase begins. In addition, a curve 24 is plotted in the diagram 10, which illustrates the synchronizing force, in particular its time curve. In this case, the first time span is identified by s1, wherein the second time span is identified by s2. It is particularly well recognizable on the basis of the diagram 10 that the at least essentially continuous reduction of the synchronizing force begins before the point in time t1 and thus before the mechanical unlocking phase, so that the synchronizing forceafter it was increasedis continuously reduced, before the unlocking takes place.

[0045] A curve 26 is plotted in the diagram 12, which illustrates a gear selector path. The gear selector path is a path over which a gear selector is moved, in particular by means of a further actuator or by means of the actuator. The first gear is disengaged and the second gear is engaged, for example, by means of the gear selector. In particular, the sliding collar is displaced in the described manner along the axis of rotation by means of the gear selector and is thus moved into engagement with the clutch body or the fourth gear teeth, respectively.

[0046] The actuator for exerting the synchronizing force can be designed as an electric or electromechanical actuator and/or as a pneumatic actuator and/or as a hydraulic actuator. In particular, the actuator can be designed as a hydraulic actuator, so that the synchronizing force is effectuated, for example, by means of a hydraulic fluid, in particular by means of a pressure of the hydraulic fluid. Thus, for example, the curve 24 illustrates a pressure, in particular a target pressure of the hydraulic fluid, by means of which the synchronizing force is finally effectuated.

[0047] A curve 28 is plotted in the diagram 14, which illustrates an interfering torque applied to the at least one wheel and/or acting on the at least one wheel. A curve 30 is plotted in the diagram 16, which illustrates a torque of the wheel. It is particularly well recognizable from the FIGURE that a harmonic or harmonized dissipation of the interfering torque illustrated by the curve 28 is implementable by the described setting of the synchronizing force, so that the method is designed as a method for harmonized interfering torque cessation during the synchronizing in the transmission. For example, at a point in time t2, which chronologically follows the point in time t1, for example, the first drive element reaches the target speed, which is also referred to as the synchronization speed. Before the speed of the first drive element corresponds to the target speed, i.e., before the speed reaches the target speed, the interfering torque on the wheel is at least reduced or is completely canceled out by the synchronizing force being reduced essentially continuously before the speed reaches the target speed and/or before the mechanical unlocking phase begins.

[0048] During the synchronizing, for example, the maximum permissible gradient, in particular of the curve 22, is limited as a function of the difference between the speed and the target speed during the approach of the speed to the target speed. The required synchronizing force to set, in particular to adjust, the limited and therefore required gradient is thus reduced. Due to the reduction of the synchronizing force, the first drive element to be synchronized accelerates significantly more slowly in comparison to methods in which the synchronizing force is not reduced, whereby the torque taken from the drive is reduced by the same amount. Thus, at the point in time t1 of the beginning of the mechanical unlocking phase, the interfering torque at the wheel is already dissipated enough that the torque-side decoupling of the accelerating drive element has a neutral effect in the torque balance. At the same time, a substantial increase of the synchronizing duration can be avoided by this measure, since the maximum gradient remains unchanged by the force-reducing measure. Particularly rapid and comfortable synchronization can thus be implemented.

[0049] It is recognizable from the FIGURE on the basis of the diagram 10 that a third time span s3 can follow the second time span s2, during which the synchronizing force is increased, in particular linearly. Therefore, possible designs of the curve 24 are illustrated in the diagram 10 by dashed lines 32, so that different embodiments of the curve 24 and thus different time curves of the synchronizing force are illustrated on the basis of the dashed lines 32.