WO2008104148A1 - Method and device for controlling the clutches of a parallel transmission when shifting gears - Google Patents

Abstract

Disclosed is a method for controlling the clutches of a parallel transmission when shifting from a starting gear to a target gear. Said method, in which torque is transferred from the load-discharging clutch to the load-accepting clutch when shifting gears, encompasses the following steps: the transmissible torque of the load-accepting clutch is increased to the current engine moment; the transmissible torque of the load-discharging clutch is reduced; when shifting gears, the total torque comprising the transmissible torques of the load-discharging clutch and the load-accepting clutch is at least temporarily greater than the current engine moment, and the transmissible torque of the load-accepting clutch is greater than a threshold torque at which the torque of the load-accepting clutch is steadily increased from the initial torque transfer state to a final torque transfer state.

Description

 Method and device for controlling the clutches of a parallel transmission in a gear change

The application relates to a method and apparatus for controlling the clutches of a parallel shift transmission during a gearshift.

Such methods and devices are used to control clutches of automatic transmissions in automobiles. Such parallel gearbox or dual-clutch gearbox find because of the possible driving comfort gain, the possible fuel savings and the possible traction interruption-free gear changes increasingly use in vehicles.

In this case, various ways to torque transfer are known to open at a gear change associated with the old gear, initially fully closed clutch to close and the new gear associated, initially open clutch.

One example is, at the beginning of the gear change, the initially fully-engaged and power-outputting clutch associated with the old gear to be slipped into slipping operation, during which slipping operation progressively closes the load-accepting clutch associated with the new gear until it is approximately slip-free, and then fully open the power-outputting clutch. In this case, in the adjustment of the power-outputting clutch in slip operation usual, in addition, an engine intervention in order to avoid in particular a high rotation of the engine.

Another possibility for controlling the clutches of a parallel shift transmission in a gear change from an output gear into a target gear with torque transfer from a power-transmitting to the power-receiving clutch is described in DE 10 2005 037 515. In this case, the clutch associated with the load output gear is held in a non-slipping position, the transmittable torque of the new gear associated with the load-receiving clutch is increased to the instantaneous engine torque, and opened the old gear associated clutch. Another strategy is known from EP 1 507 103 B1. Starting from an initial state of the torque transfer, in which the power-outputting clutch transmits a drive torque in the adhesion state and the power-receiving clutch is open, to a final state of the torque transfer, in which the power-receiving clutch transmits the full drive torque, the engaging clutch builds torque capacity in the slip region and the power output clutch torque capacity off. In this case, in the initial phase of the torque transfer, the power-outputting clutch has a higher torque capacity than is necessary to maintain its adhesive state, wherein the torque capacity of the power-outputting clutch before the torque capacity of the power-receiving clutch reaches the full drive torque is reduced so far that the power-outputting clutch and the load-accepting Clutch both torque slipping transmitted a certain time.

On this basis, it is an object of the invention to provide a method and an apparatus for controlling the clutches of a parallel transmission in a gear change, which allows a simple way a quick gear change, possibly without engine intervention.

This object is achieved by a method having the features of claim 1. Preferred embodiments are given in the dependent claims. An apparatus for carrying out the method is specified in claim 7.

According to the solution of the invention is the gear change of an output gear in a target gear, in which a torque transfer from a power-outputting clutch to a power-receiving clutch, increases the transmittable torque of the power-receiving clutch up to the instantaneous engine torque and simultaneously reduced the transmittable torque of the power-outputting clutch. During the gear change, the total torque from the transmittable torques of the power-outputting clutch and the power-receiving clutch is at least temporarily greater than the instantaneous engine torque, wherein the power-receiving clutch is maintained in over-pressure. This ensures that no slippage occurs at one of the two clutches, for example, in Zughochschaltungen or push downshifts on the power output clutch. Conversely, the load-accepting coupling is liable for train downshifts and shear upshifts. Towards the end of the overlapping operation, it is then attempted to reduce the sum torque to approximately the instantaneous engine torque, so that through this Advantageous design can be controlled via emerging slip, whether the power-receiving coupling transmits the torque assumed by the controller. This reduction to the instantaneous engine torque is preferably accomplished by increasing the transmissible torque of the power-receiving clutch less, that is, at a lower pitch rate than in the initial phase of the overlap, wherein the rate of reduction or degradation rate of the transmissible torque of the power-outputting clutch is kept essentially unchanged throughout the overlap.

At the same time, it is possible to perform an engine intervention so that the rate of change of the instantaneous engine torque is limited while the speed change operation is being performed. In addition, preferably the rate of change of the clutch torque should be limited. As a result, it can be achieved that an influence of the output torque by the excessive concern of the power-receiving clutch is not perceived by the driver.

The invention will now be described by way of example with further details with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic diagram of a dual-clutch transmission with control device;

Fig. 2 is a diagram for explaining the method according to the invention, wherein a pull upshift is shown;

FIG. 3 shows an alternative shift strategy according to the method of the invention in a pull upshift; FIG. and

Fig. 4 shows a still further strategy in a pull upshift according to the inventive method.

According to FIG. 1, a double-clutch or parallel-shift transmission known per se has a drive shaft 6 which is driven, for example, by an internal combustion engine and which is non-rotatably connected to two input shafts 8 and 10. The torque flow from the drive shaft 6 in the input shafts 8 and 10 is selectively controllable via a respective clutch K1 and K2. Between the input shaft 8 and an output shaft 12, different ratios are switchable via pairs of wheels, of which only one is shown. Likewise, 12 different wheel pairs are switchable between the input shaft 10 and the output shaft, of which only one is shown. To actuate the clutches K1 and K2 are actuators 14 and - A -

16 provided. For switching the pairings of wheels, for example for producing a rotationally fixed connection between the arranged on the input shaft 8 or 10 wheel with the respective input shaft 8 or 10, which meshes with a respective, permanently connected to the output shaft rotatably connected to the wheel, actuators 18 and 20 are provided.

For controlling the actuators 14, 16, 18 and 20 is an electronic control device 26 with microprocessor and associated program and data storage, the outputs each one of the actuators and control the inputs 28 are connected to unillustrated sensors of the vehicle or vehicle powertrain, such as a sensor for detecting the position of an accelerator pedal, a sensor for detecting the engine speed or the rotational speed of the drive shaft 6, a sensor for detecting the rotational speed of the output shaft 12 or sensors for detecting the rotational speed of the driven vehicle wheels, a sensor for detecting the position of Getriebewählhebels etc .. The illustrated control device 26 may be connected via a bus system with other control devices of the vehicle, such as an engine control unit with which a power actuator of the engine is controlled. The actuators 14, 16, 18 and 20 may be designed, for example, as a hydraulic actuating cylinder, the pressure of which is controlled by a controlled by the control device 26 hydraulic system. The actuators may include electric motors as needed to drive an actuator. The position of the actuator can be advantageously detected by a sensor, so that the functional state is known in each case.

The torque which can be transmitted by the clutch is important for the function of a clutch and is stored as a curve in a memory of the control device 26, which indicates the transmittable clutch torque depending on the position of a clutch actuator, for example a clutch actuating lever. When changing the functional state of the clutch by wear and the like, the characteristic curve must be updated, which is done by homing, where certain points of the clutch are approached and the respective associated position of the actuator or actuator is detected and updated in the controller.

In the dual-clutch transmission shown in Fig. 1, in each case a gear can be engaged in the partial transmission, the clutch is open, while the effective ratio of the transmission is determined by the partial transmission, the clutch is closed. If, for example, a gear is engaged in the partial transmission 22 and the clutch K1 is closed, then this gear is for the transmission between the drive shaft and the output shaft 12 effective. At the same time, a new gear to be shifted can be engaged in the partial transmission 24. If the gear to be newly engaged is to take effect and the associated clutch K2 is closed, the clutch K1 must then be opened when shifting the transmission from the currently engaged gear into the gear to be newly engaged. If the clutch K2 takes over the torque transmission, if not at least one of the clutches K1, K2 slips simultaneously, destroys the transmission by overdetermination of the translations. Therefore, at least at times, when both clutches K1, K2 are inserted simultaneously, a slipping state is established, in which at least one of the two clutches K1. K2 is slipping.

In the method according to the invention it is thereby ensured that the power-receiving clutch, in the above example the clutch K2, is in a state of overpressing, while the power-outputting clutch, in the above example the clutch K1, reduces torque capacity at a rate which is between the initial state closed clutch and the final state with the clutch open is substantially constant. This means that at the beginning of the overlapping operation, the load-accepting clutch K2 continues to move as the power-outputting clutch K1 opens. This results in that the sum of the transmittable torques of the clutches K1, K2 is greater than an output torque MA of the drive or motor shaft 6.

Figure 2 shows an example of the design for a pull upshift. From a point in time t1, the load-accepting clutch K2 is initially closed further than would be necessary. This causes the clutch K2 to have a transmittable clutch torque MK2 that is greater than a limit torque MG at which the clutch K2 has a torque capacity increase rate that is constant between the initial and final state of the overlap. This also means that the total torque MS from the transferable clutch torque MK1 of the slipping state clutch K1 and the transferable torque MK2 of the clutch K2 is greater than the instantaneous engine torque MA. This is achieved in that the clutch K2 is further closed by suitable actuation of the actuators or actuators 14, 16 and the contact pressure is increased more than the increase in the limit torque MG (course with constant slope between fully open state of the clutch K2 and fully closed State of the clutch K2) corresponds. The slope is thus greater than that of the limit torque MG. At a later stage within the overlap, the rate at which the clutch torque MK2 of the clutch K2 is increased can be changed (starting from the time t1 'in FIG. 2), but still the transmittable torque of the clutch ment K2 is greater than the limit torque MG. By reducing the rate of increase of the transmittable torque MK2 of the power receiving clutch K2, the transmittable torque MK2 of the clutch K2 approaches the limit torque MG. Towards the end of the overlapping phase, starting from the time t2 in FIG. 2, the transferable torque MK2 of the clutch K2 is finally ground to the correct sum torque, that is MK1 + MK2 = MA, wherein the torque MK1 of the power output clutch K1 is from the beginning of the overlapping phase is reduced at the time t1 to the fully open state of the clutch K1 with a constant rate of degradation. The point at which the power-receiving clutch approaches or grinds to MG is characterized by the accuracy expectation that the controller 26 has of the torque estimate of the power-receiving clutch K2. At this time, slip is generated and kept constant by means of a slip control of the load-receiving clutch K2 or the power-outputting clutch K1, so that the torque can be adjusted with it.

At time t3, the clutch K1 is fully opened and the clutch K2 is fully closed, so that via the clutch K2, the torque is transmitted from the motor shaft 6 to the output shaft 12.

If the load-accepting clutch K2 transmits too little torque in the embodiment shown in FIG. 2, a control of the slip begins even before the actual grinding, namely at the instant t2 '. This is preferably done when a slip has already been detected before time t2, for example at time t2 'in FIG. 3.

The method according to the invention can also be used if there is already slip on the input shaft of the power-outputting clutch during the gear change at the beginning. For example, when multiple strategies for clutch control are stored in the controller 26 during the gear change operation, it may be first detected whether the input shaft of the power output clutch K1 is in the slipping state and, if so, the inventive strategy is applied. This is shown in FIG. 4. In this case, this slip of the power-outputting clutch K1 is reduced by way of a slightly increased gradient of the load-accepting clutch K2. However, the slip of the power-outputting clutch must not be too large, otherwise the time to reduce the slip tT would otherwise exceed the time required to reach the correct summation torque t2. Advantageously, the torque change of the clutch torque MK1, MK2 is limited during the entire gear change operation with torque transfer between a power-outputting clutch K1 and a power-receiving clutch K2, so that influencing the output torque by the excessive application of the power-receiving clutch K2 not perceived by the driver becomes.

Bezugszeicheniiste

drive shaft

motor shaft

Input shaft 0 Input shaft 2 Output shaft 4 Actuator 6 Actuator 8 Actuator 0 Actuator 2 Partial transmission

24 partial transmissions

26 control device

28 inputs

K1 clutch

K2 clutch

MK1 clutch torque

MK2 clutch torque

MG limit torque

MS total torque

MA motor torque t1 time t2 time t3 time t2 'time tr time

Claims

claims A method of controlling the clutches of a parallel shift transmission in a gear shift from an output gear to a target gear, wherein during the gear change a torque transfer from the power output to the power receiving clutch takes place, comprising the steps of Increasing the transmittable torque (MK2) of the power-receiving clutch to the instantaneous engine torque (MA); Reducing the transmittable torque (K1) of the power-outputting clutch; wherein during the gear change, the total torque (MS) of the transmissible torques of the power-outputting clutch (MK1) and the power-receiving clutch (MK2) at least temporarily greater than the instantaneous engine torque (MA) and the load-receiving clutch has a higher transmittable torque than one Limit torque (MG) corresponds, in which the torque of the power-receiving clutch evenly from the output state of the torque transfer, especially when the power-receiving clutch is open, to a final state of the torque transfer, especially when transmitting the full engine torque (MA) is increased. 2. The method according to claim 1, characterized in that in a final phase of the gear change, the total torque (MS) is reduced to the instantaneous engine torque. A method according to claim 2, characterized in that the sum torque is reduced to the instantaneous engine torque by reducing the rate of increase of the transmittable torque (MK2) of the power-receiving clutch at a substantially constant rate of reduction of the transmittable torque (MK1) of the power-outputting clutch. 4. The method according to any one of the preceding claims, characterized in that during the gear change, the rate of change of the clutch torque (MK1, MK2) is limited. 5. The method according to any one of the preceding claims, characterized in that the increasing of the transmittable torque of the power-receiving clutch and the reduction of the transmittable torque of the power-outputting clutch start simultaneously. 6. The method according to any one of the preceding claims, characterized in that the increase of the transmittable torque (MK2) of the power-receiving clutch is not continuous. 7. A device for controlling the clutches (K1, K2) of a parallel shift transmission (22, 24) in a gear change, comprising an electronic control device (26) for driving actuators (14, 16) of the clutches, wherein the control device with sensors for detecting Operating parameters of a vehicle is connected and controls the actuators (14, 16) by performing a method according to one of claims 1 to 6.