CN106438990B

CN106438990B - Method for controlling a vehicle drive unit

Info

Publication number: CN106438990B
Application number: CN201610831160.XA
Authority: CN
Inventors: M·尤加; T·弗路维斯
Original assignee: AVL List GmbH
Current assignee: AVL List GmbH
Priority date: 2015-08-03
Filing date: 2016-08-02
Publication date: 2020-03-03
Anticipated expiration: 2036-08-02
Also published as: AT517078A4; DE102016114088A1; CN106438990A; AT517078B1

Abstract

The invention relates to a method for controlling a drive unit in a drive train of a vehicle, the drive unit having a vehicle transmission and a drive machine, the drive machine being connected to an output via different gears by means of a first clutch on a first transmission path and a second clutch on a second transmission path, the synchronization of the engine speed being carried out at least during a shifting process before torque is transferred from the first clutch to the second clutch, the drive connection between the drive machine and the first transmission path being separated by opening the first clutch during the torque transfer, and the drive connection between the drive machine and the second transmission path being established by closing the second clutch. In order to increase the driving comfort during the switching process, it is provided that the opening of the first clutch is monitored and, if an error is detected during the opening of the first clutch, the second clutch is closed until a defined slip limit is reached and, once the slip limit is reached, the second clutch is immediately opened again.

Description

Method for controlling a vehicle drive unit

Technical Field

The invention relates to a method for controlling a vehicle drive unit, comprising a vehicle transmission and a drive machine, wherein the drive machine is connected to an output via different gears by means of a first clutch on a first transmission path and a second clutch on a second transmission path, wherein at least during a shifting operation the synchronization of the engine speed is carried out before torque is transferred from the first clutch to the second clutch, wherein, during the torque transfer, the drive connection between the drive machine and the first transmission path is disconnected by opening the first clutch, and the drive connection between the drive machine and the second transmission path is established by closing the second clutch.

Background

EP 1507103 a1 discloses a method for shifting a transmission in the form of a dual clutch transmission, in which a first clutch on a first transmission path and a second clutch on a second transmission path connect the engine to the output via different gears. Before the shifting operation, the engine torque is transmitted via the first clutch to the output on a first transmission path, wherein the engaged gear of the first transmission path determines the transmission ratio. Taking this transmission ratio into account, a first output torque is provided on the shaft of the output. Before the shifting operation, the second clutch does not transmit torque, and the transmission path associated with the second clutch is accordingly unloaded. Due to the fact that there is no load, it is possible to engage or pre-select a gear in the second transmission path before the shifting operation. During a gear change, the preselected gear is the target gear, while the engaged gear of the transmission path leading to the load corresponds to the source gear.

During the gear change, there are phases in which the engine speed is synchronized and phases in which torque is transmitted from the first clutch to the second clutch. During the phase of synchronization, the engine is braked or accelerated until the engine speed corresponds to the speed of the second transmission path. During the phase of the torque transfer, the second clutch is closed, so that the torque transmitted by the second clutch, starting from zero torque, rises in such a way as to follow a certain curve. The torque transmitted by the first clutch is simultaneously reduced until it is zero. If the torque transfer phase is over, engine torque is transferred entirely by the second clutch.

The shifting process is an upshift, and the source gear has a larger gear ratio than the target gear. As long as the engine torque remains constant, the torque applied to the shaft of the output is reduced accordingly by the shifting process.

It is known to perform synchronization of engine speed during a gear shift process, either before or after torque is transferred from the first clutch to the second clutch. For a traction upshift and a propulsion downshift, the synchronization is carried out after a torque transfer by means of a corresponding actuation of the engaged clutch. For a forward upshift and a forward downshift, the synchronization is carried out before the torque transfer by means of the corresponding actuation of the clutch to be disengaged.

In a traction upshift, a higher torque than the input torque is set in the slipping clutch engaged in the torque transfer during synchronization in order to reduce the input speed in a controlled manner and to reduce the slip in the engaged clutch. In a forward downshift, a torque higher than the absolute value of the input torque is also set at the slipping clutch engaged in the torque transfer during synchronization in order to increase the input rotational speed and reduce the slip in the engaged clutch. In a traction downshift, a torque lower than the input torque is transmitted in a targeted manner to the clutch to be disengaged during synchronization in order to increase the input rotational speed and to cause a clutch slip (with the aim of reducing the clutch slip of the clutch to be engaged). In a push-type downshift, a torque lower than the absolute value of the input torque is transmitted in a targeted manner to the clutch to be disengaged during synchronization in order to reduce the input rotational speed and to cause a clutch slip (with the aim of reducing the clutch slip of the clutch to be engaged). This makes it possible to achieve a bumpless shift.

In the case of a propulsion upshift, however, it sometimes happens that the clutch to be disengaged is not opened without error, since the interacting clutch surfaces are still attached to one another in a completely pressureless state and transmit a torque that is higher than the absolute value of the input torque. The first clutch is therefore not usable for rotational speed synchronization because of the slip between the interacting clutch surfaces, which slip cannot be built up in this way. Without the preceding synchronization process, in the case of large rotational speed differences between the drive motor and the second clutch path, a clearly perceptible strong jerk can occur during the gear shift, which has an adverse effect on the driving comfort.

Disclosure of Invention

The object of the invention is therefore to improve the driving comfort during the switching process.

According to the invention, this is achieved by monitoring the opening of the first clutch and, if an error is detected in the opening of the first clutch (the synchronization of the rotational speed does not start as desired), closing the second clutch until a defined slip limit is reached.

Advantageously, the second clutch is preferably opened again immediately when a defined slip (Schlupf) is reached or exceeded.

Torque introduced through the second clutch is transferred to the first clutch via the transmission path and causes disengagement of the attached clutch surface of the first clutch.

Just after the second clutch is fully opened again, the torque on the first clutch is adjusted for synchronization of the engine speed.

If it is determined that the first clutch is not fully opened even if the closing force is fully released and therefore a slipping (slipping) operation of the first clutch cannot be achieved for carrying out the engine synchronization, the operating strategy is changed in that the second clutch is closed for a short time as an intermediate step until a defined clutch slip (slipping) on the first clutch is measured. Subsequently, the clutch torque of the second clutch is reduced to zero again. This measure is sufficient to disengage the attachment (sticking) of the first clutch. Thus, the first clutch can now be used again for the synchronization of the drive machine.

The method according to the invention is advantageously suitable for different types of vehicle transmissions in which a cross-shift from one friction clutch to another is effected. With such a transmission, shifts with uninterrupted tractive force can be achieved. For example, a dual clutch transmission or an automatic transmission with a torque converter or a starting clutch can be used as a vehicle transmission. The method is not limited to these transmission types.

Drawings

The invention is described in detail below with reference to non-limiting embodiments shown in the drawings. Wherein:

FIG. 1 schematically illustrates a transmission for implementing the present invention;

fig. 2a shows a rotational speed profile during a gear shift process using the method according to the invention;

fig. 2b shows a torque profile during a gear shift process using the method according to the invention.

Detailed Description

Fig. 1 shows a vehicle drive train 1 having a drive machine 2, which is currently designed as an internal combustion engine, a double clutch transmission 3 and an output 4. In the region of the two

transmission paths

5, 6 of the dual clutch transmission 3, a plurality of transmission ratios can be achieved by engaging and disengaging hydraulically actuatable shifting elements, which are preferably embodied as synchronizing elements and are not shown in detail in the figures. The

transmission input shaft

7 or 8 of the first or

second shift path

5 or 6 can be operatively connected to the drive machine via a first clutch 9 (in the illustrated exemplary embodiment a normally closed clutch) or a second clutch 10 (in the illustrated exemplary embodiment a normally open clutch) of a double clutch device 11, which is embodied as a frictionally engaged (locked) shifting element. At the transmission output, the

transmission paths

5 and 6 are operatively connected to a transmission output shaft 12, which in turn is connected to the output 4.

The drive machine 2 can be connected to the output 4 via a first clutch 9 on the first transmission path 5 and a second clutch 10 on the second transmission path 6 by different gears. Prior to the shifting operation, the engine torque on the first transmission path 5 is transmitted via the first clutch 9 to the output 4, wherein the engaged gear of the first transmission path 5 determines the gear ratio. In consideration of this transmission ratio, a first output torque is applied to the transmission output shaft 12 of the output 4. Before the shifting operation, the second clutch 10 does not transmit torque, and the transmission path 6 assigned to the second clutch 10 is unloaded. Due to the fact that there is no load, it is possible to engage or pre-select a gear in the second transmission path 6 before the shifting operation. During a gear change awaiting processing, the preselected gear is the target gear, while the engaged gear of the transmission path leading the load corresponds to the source gear.

In the case of a gear shift, which is shown by way of example in a push-type upshift, the drive torque is usually transferred from the first transmission path 5 to the second transmission path 6, the first clutch 9 being slowly disengaged and the synchronization of the drive machine 2 being carried out as a result of the slipping (slipping) operation of the first clutch 9. The open first clutch 9 is operated with slip in order to synchronize the drive machine 2 with the second transmission path 6. Subsequently, the second clutch 10 is closed and the first clutch 9 is fully opened to end the torque transmission from the first transmission path 5 to the second transmission path 6.

If the clutch surfaces of the first clutch 9 are never adhered to each other despite the decrease in the clutch-closing pressure, synchronization cannot be performed.

According to the invention, it is provided that the opening of the first clutch 9 is monitored, for example, with a suitable position sensor or by monitoring the engine speed. If it is determined that the clutch surfaces are stuck to each other, the operating strategy for the normal shifting process is changed by: the second clutch 10 is closed until a defined slip limit (slip limit) is reached and opened again shortly after the slip limit (slip limit) is reached. The torque applied to the second clutch 10 causes the clutch surfaces of the first clutch 9 to become detached, so that engine synchronization can be carried out in a conventional manner by controlling the torque on the first clutch 9. As soon as the synchronization process is finished, the second clutch 10 is completely closed and the first clutch 9 is completely open in order to transfer torque from the first transmission path 5 to the second transmission path 6.

Fig. 2a and 2b show the course of the rotational speed n and the torque Tq over time t during a gear change, for example from second gear to third gear. The gear shift is divided into a preparatory phase P1, a rotational speed phase P2, a torque phase P3 and a reestablishment phase P4.

Fig. 2a shows a profile of the rotational speed n of the drive shaft 2a of the drive machine 2, wherein in a rotational speed phase P2 an adjustment of the rotational speed n of the drive shaft from the rotational speed n5 of the second gear stage (of the first transmission path 5) to the rotational speed n6 of the third gear stage (of the second transmission path 6) is effected.

Fig. 2b shows a profile of the torque of the first clutch 9 Tq9 and a profile of the torque of the second clutch 10 Tq10 for a gear shift. The drive torque of the drive shaft 2a is denoted by Tq2, and its absolute value is denoted by Tq 2'.

In the preparatory phase P1, the second clutch 10 is filled and prepared for subsequent use. The closing pressure of the first clutch 9 is reduced to the attachment point a. The attachment point a is a point at which the torque Tq9 is equal to the absolute value Tq 2' of the driving torque Tq 2. If the closing pressure drops below the attachment point A, the clutch theoretically begins to slip (spin). After the end of the preparatory phase P1, a speed synchronization phase P2 is started, in which the first clutch 9 is operated with a defined slip. The speed synchronization phase P2 has at the beginning partial sections P21, P22 and P23. In the first partial range P21 of the rotational speed synchronization phase P2, a slip is attempted to be induced on the first clutch 9 by controlling the torque of the first clutch 9 in such a way that the first clutch 9 continues to open. If the attempt is not successful because the clutch surfaces of the first clutch 9 are attached to each other, the operating strategy is changed at the end of the first partial section in order to use the second clutch 10 as an impulse to force the first clutch 9 to disengage. For this purpose, in the second partial segment P22, the second clutch 10 is closed for a short time until a defined slip is generated and measured. Subsequently, in the third partial range P23, the second clutch 10 is opened again up to the contact point ("engagement point") in order to be able to achieve a speed synchronization of the drive shaft 2a with the target speed n6 of the second transmission path 6 in the fourth partial range P24 by corresponding actuation of the first clutch 9. After the speed synchronization phase P2, a torque transmission from the first clutch 9 to the second clutch 10 is effected in the torque phase P3. In the reestablishment phase P4, the torque transfer is ended and the second clutch is fully closed.

The method according to the invention is advantageously suitable for different types of vehicle transmissions, such as dual clutch transmissions, automatic transmissions or other transmissions (for example also automatic transmissions with a torque converter and a starting clutch or other transmission types, such as dual clutch transmissions, or countershafts in a corresponding design or all-wheel drives with a low gear ratio), in which a cross-shift from one friction clutch to another is effected. With such a transmission, shifts with uninterrupted tractive force can be achieved.

Claims

1. A method for controlling a drive unit in a vehicle drive train (1), having a vehicle transmission and a drive machine (2), wherein the drive machine (2) is connected to an output (4) via different gears by means of a first clutch (9) on a first transmission path (5) and a second clutch (10) on a second transmission path (6), wherein synchronization of the engine speed is carried out at least during a gear shift process before torque is transferred from the first clutch (9) to the second clutch (10), and wherein, at the time of torque transfer, a drive connection between the drive machine (2) and the first transmission path (5) is disconnected by opening the first clutch (9) and a drive connection between the drive machine (2) and the second transmission path (6) is established by closing the second clutch (10), characterized in that, for a push-on upshift, the opening of the first clutch (9) is monitored and, if an error is detected when opening the first clutch (9), the second clutch (10) is closed until a defined slip limit is reached.

2. Method according to claim 1, characterized in that the second clutch (10) is opened again when a defined slip is reached or exceeded.

3. Method according to claim 1, characterized in that the first clutch (9) is used for synchronization of the engine speed after the second clutch (10) has been fully opened.

4. Method according to claim 1, characterized in that the second clutch (10) is immediately opened again when a defined slip is reached or exceeded.