AT519291B1 - METHOD FOR CONTROLLING A SWITCHING PROCESS OF A HYBRID DRIVE - Google Patents

Abstract

The invention relates to a method for controlling a switching operation from a current gear to a target gear of a hybrid drive with at least one opening clutch and at least one closing clutch and with a first decision to select the sequence of adjustment of the torques of clutches and speeds of drive elements of a state for a current gear on a state of a target gear. The object of the invention is to provide a method which makes it easy to make a decision to control the switching process. The invention does not intervene in the specification of vehicle drive torque and distribution of the torques of the drive elements. According to the invention this is achieved in that a sign of a transmitted torque (Toff, trans) of the opening clutch is checked for whether a first switching sequence is possible.

Description

The invention relates to a method for controlling a switching operation of a hybrid drive, with at least two drive elements and with at least one opening clutch and at least one closing clutch and with a first decision to choose the sequence of adaptation of the torques of the clutches and speeds of the drive elements from a state in the current gear to a state of a target gear.

In conventional automatic transmissions, the shift operation is determined depending on the orientation of the magnitude of the input and the output torque. A distinction is made in the switching process between the types of train train-upshift, train-downshift and overrun upshift and overrun downshift. From the type of shift it is decided which sizes are adjusted first, the torque or the speed.

Certain types of hybrid drives, which are referred to in the literature as Dedicated Hybrid Transmission (DHT), in addition to the conventional hybrid modes also hybrid operation modes (gears) with continuously variable transmission ratio, ie a fixed gear corresponds to two mechanical degrees of freedom in the transmission.

For vehicles with hybrid drive now the orientation of the size of the input and the output torque is no longer a guarantee to distinguish between the different types of switching operation and make the right decision, especially since such transmissions usually have two input shafts.

It is no longer imperative that always takes place for the request to the output torque, the same torque transmission via the clutch. Depending on the distribution of the torque between the different types of drive can be transmitted by the clutch once a negative and once a positive torque to the output. This is problematic in that it is currently not possible to perform a switching operation smoothly.

In US 2015/0184740 A1 a method for controlling the switching operation is shown. For this purpose, a ratio between the individual transmitted torques is considered and decided on the basis of which the setting of the individual sizes after the switching operation. The disadvantage of this is that it takes decisions to make a complicated and expensive algorithm and the decision thus requires some computational effort and even leads to a delay. Furthermore, the risk of errors is increased.

From DE 102010008786 A1 and DE 102010021799 A1 methods for controlling switching operations of a hybrid drive are known. In each case, it is checked whether a switching sequence is completed using the approaching clutch or the outgoing clutch. This takes a lot of time and computing power. It can therefore come to the choice of the correct switching sequence to a delay.

The object of the invention is to provide a method which avoids these disadvantages and allows a simple decision to control the switching operation.

According to the invention this is achieved in that a sign of a transmitted torque of the opening clutch is checked for whether a first switching sequence is possible. Since only the sign of the torque is checked in this step, only a very simple algorithm is necessary and the computational effort is limited. In this case, the sign can be checked, for example, by means of a look-up table (LUT), a conversion table. In this case, the sign is compared with the entry in the LUT for a given division of the drive torque depending on a current gear and a target gear and so decided whether the first switching sequence is possible or not.

Under a first switching sequence understood here is the previous adjustment of the rotational speeds of the drive elements from a state in the current gear to a state of a target gear.

It is advantageous if it is checked in a possible first switching sequence, if a required torque of the closing clutch and a current slip speed have the same sign and if an adjustment of the input speed to the output speed is carried out so that the sign of the slip speed its orientation changes when the sign of the slip speed and the sign of the required torque of the closing clutch are different. This creates the advantage that a decision to properly adjust the speeds can be made quickly.

In this case, the required torque of the closing clutch is calculated, for example model based and compared the sign of the required torque of the closing clutch with the sign of the current slip speed.

It is advantageous if before the torque adjustment in the first switching sequence, the current slip speed has the same sign as the required torque of the closing clutch, which may possibly be ensured in the upstream phase of the speed adjustment.

A particularly favorable method provides that in a non-possible first switching sequence, a second switching sequence is selected. This makes it easy to decide between the first and the second switching sequence.

Under a second switching sequence understood here is the previous adjustment of the input torque to the output torque and the adjustment of the torques of the clutches and in the current gear to a state of a target gear.

In another embodiment, the assignment torque adjustment and speed adjustment to the first switching sequence and the second switching sequence can be reversed.

It can be quickly and easily checked whether an adjustment of the sizes before or during the circuit is necessary when checking whether a sign of the required torque of the closing clutch is equal to a sign of a current slip speed.

Another advantage of the invention is to perform the switching operation without changing the two predetermined in the hybrid drive strategy goals during the switching process. For both the desired drive torque of the vehicle, which is specified by the driver, as well as the desired division of the drive torque to the two drive elements are not changed during the switching operation.

As drive elements, both internal combustion engines, and electric motors can be seen, in which case any conceivable type of motor or combination thereof can be used in principle.

In a special case, it may be necessary for a smooth shift operation to make a change of a split of the torques of two drive elements before the shift itself is performed, so that the sign of the current slip speed changes its orientation when the sign of the Torque of the closing clutch is not equal to the sign of the current slip speed and when the switching operation is performed when the sign of the torque of the closing clutch corresponds to the sign of the current slip speed. Thereby, a necessary adjustment of the torques can be carried out, if necessary.

Reference to the non-limiting figures, the inventive method is explained in detail. FIG. 1 shows a decision diagram for the method according to the invention; FIG. FIG. 2 is a first diagram of rotational speeds of input waves versus time during a first switching sequence; FIG. Fig. 3 is a second diagram of requested (or required) clutch and

Drive source torques over time during the first switching sequence; FIG. 4 is a third diagram of a slip of a closing clutch during the first shift sequence; FIG. FIG. 5 is a fourth diagram of transmitted clutch torques over time during the first shift sequence; FIG. FIG. 6 is a fifth diagram of rotational speeds of input shafts versus time during a second switching sequence; FIG. FIG. 7 is a sixth graph of requested (or required) clutch and drive source torques over time during the second shift sequence; FIG. FIG. 8 is a seventh diagram of a slip of a closing clutch during the second switching sequence; FIG. and FIG. 9 is an eighth diagram of transmitted clutch torques over time during the second shift sequence.

FIG. 1 shows the sequence of a method according to the invention in a decision diagram. A start 1 of a process is triggered with the desire for a switching operation. In a first decision 2, it is checked whether it is possible to carry out a first switching sequence on the basis of an indication of a transmitted torque Toff, trans of an opening clutch and comparison with a target torque in a target gear (for example via an LUT or a model).

If the execution of the first switching sequence is possible and a first action 3 is set, that is, a first switching sequence is selected, a second decision 4 is subsequently made. In the second decision 4, it is checked whether a current slip speed s has the same sign as a required torque Ton, erf in a target gear of a closing clutch.

If the signs agree, a second action 5 is set. In the second action 5, the switching operation is performed. The slip speed s of the closing clutch is reduced until it is approximately zero, or corresponds to a predetermined residual slip speed.

If the signs of the current slip speed s and the required torque tone, erf do not match, in a third action 6, the adaptation of input speed to the output speed so that the slip speed s changes its orientation.

If in the first decision 2 the implementation of the first switching sequence is not possible, then a fourth action 7 is set and a second switching sequence initiated. In the second shift sequence, the adjustment of the input torque to the output torque is performed first and then the adjustment of the input speed to the output speed is performed.

It comes to a third decision 8, is checked to see whether a sign of the required torque Ton, erf the closing clutch equal to the sign of the current slip speed s. With the same sign, a fifth action 9 is initiated and the switching operation is performed.

If this condition does not apply, a sixth action 10 is initiated, in which a change of a distribution of torques of two drive elements is performed, so that without affecting the vehicle acceleration, the sign of the current slip speed s changes the orientation. Only then is the switching process carried out.

An example for carrying out the first switching sequence is shown in FIGS. 2 to 5. FIG. 2 shows a first diagram in which rotational speeds n are plotted over time t. Here, na denotes an input speed of a current gear, nr an input speed of a target gear and ne a speed of an internal combustion engine. FIG. 3 shows a second diagram in which torques over time t are indicated. Te stands for a torque of the internal combustion engine, Tm is a torque of an electric motor. Toff erf is a required torque of the opening clutch and tone, erf is a required torque of the closing clutch. In Fig. 4, a slip speed s is plotted against time, and in Fig. 5, a transmitted torque Tt over time is plotted, where Tofftrans denotes a transmitted torque of the opening clutch and tone, trans a transmitted torque of the closing clutch.

Before a first phase A, a sign of the transmitted torque of the opening clutch Tofftrans is checked. In a first embodiment, the sign is compared by means of a LUT with a sign necessary for the first switching sequence. The necessary sign for the first shift sequence is stored in the LUT as a function of the current gear and the target gear.

Before the first phase A, the transmitted torque Toff trans of the opening clutch is negative as shown in FIG. In the LUT, for example, now also a negative sign for the first switching sequence is stored. This results in the first decision 2, the first action 3 and the first switching sequence is executed.

In another embodiment, the sign is calculated via a model.

Furthermore, before the first phase A, the required torque Ton, erf is calculated model-based for the target gear of the closing clutch, as shown in FIG. 3, and the sign is compared with the sign of the slip speed s in FIG.

If these two signs match, an adjustment of the speeds of the closing clutch is performed so that the slip speed s is formed to zero, with a predetermined residual slip speed can be achieved.

If these two signs do not match, as shown in Fig. 4, a third action 6 is performed and the adjustment of the speeds in the first phase A of the closing clutch is such that the slip speed s its sign changes and to a predefinable Residual slip speed is controlled, as shown by the dotted line in Fig. 4. In the first phase A, the closing coupling is not yet pressed.

The dashed line in Fig. 4 shows the case that occurs when this condition of the same sign is disregarded. This results in a sudden change in the sign of the transmitted torque Ton, trans in the second phase B, as shown in Fig. 5 by the dashed line.

In a second phase B is a normal torque transfer, as it takes place according to the prior art for switching operations in conventional transmissions (automatic transmissions and dual clutch transmissions). In this case, the residual slip speed built up in the second phase B in the first phase A is maintained.

In a third phase C, as shown in Fig. 4, the slip speed s of the closing clutch is controlled to zero and then performed an over-pressing. Eventually there is still a provision for an externally given torque distribution.

FIGS. 6 to 9 show, analogously to FIGS. 2 to 5, the variables during, before and after the switching operation, when the second switching sequence is carried out.

After start 1 of the method, it is determined to the first decision 2 that the sign of the transmitted torque T0ff, trans of the opening clutch is not the necessary sign for the first switching sequence in the LUT, or is not equal to the calculated necessary sign , As a result, in the first decision 2, the second switching sequence is selected in the fourth action 7.

At the same time, the required torque Ton, erf is calculated model-based and its sign compared to the sign of the current slip speed s. If there is a match, in the third decision 8 the second switching sequence is started by the fifth action 9. If the signs do not match, the torque split is adjusted so that the sign of the transmitted torque Ton, trans changes. This guarantees that the current torque distribution is always greater than a critical split during the closing process for reversing the torque of the closing clutch.

In another embodiment, the torque distribution is changed so that the condition for the execution of the first switching sequence is met and this is subsequently performed.

In the first phase A, the predetermined torque distribution is compared with the critical torque distribution and adhered to a predetermined distance thereto. In the second phase B, the adaptation of the rotational speeds is carried out according to a standard routine. The adjustment of the speeds for conventional transmissions is known from the prior art. In the third phase C, the slip speed s is controlled controlled to zero and then there is a Überanpressung of the coupling halves of the closing clutch instead. If necessary, a return to the specified torque distribution takes place.

Claims (8)

claims 1. A method for controlling a switching operation of a hybrid drive, with at least two drive elements and with at least one opening clutch and at least one closing clutch and with a first decision (2) for selecting the sequence of adjustment of the torques of the clutches and speeds of the drive elements of a state in the current gear to a state of a target gear, characterized in that a sign of a transmitted torque (T0ff, trans) of the opening clutch is checked for whether a first switching sequence is possible. 2. The method according to claim 1, characterized in that it is checked in a possible first switching sequence, whether a torque required in a target gear (tone, erf) of the closing clutch and a current slip speed (s) have the same sign. 3. The method according to claim 2, characterized in that an adjustment of the rotational speeds of the drive elements in the state of a target gear is carried out so that the sign of the slip speed (s) changes its orientation when the sign of the slip speed (s) and the sign of the required Torque (tone, erf) of the closing clutch in a target gear are different. 4. The method according to claim 2 or 3, characterized in that the switching operation is performed with a first switching sequence when the current slip speed (s) has the same sign as the required torque (Ton erf) of the closing clutch in a target gear. 5. The method according to any one of claims 1 to 4, characterized in that in a non-possible first switching sequence, a second switching sequence is selected. 6. The method according to claim 5, characterized in that it is checked whether a sign of the torque required in a target gear (Ton, erf) of the closing clutch equal to a sign of a current slip speed (s). 7. The method according to claim 6, characterized in that a change of a distribution of the torques of the at least two drive elements is performed before the switching operation is performed, so that the sign of the current slip speed (s) changes its orientation when the sign of the transmitted Torque (tone trans) of the closing clutch is not equal to the sign of the current slip speed (s). 8. The method according to claim 6 or 7, characterized in that the switching operation is performed when the sign of the transmitted torque (tone trans) of the closing clutch corresponds to the sign of the current slip speed (s). For this 3 sheets of drawings