CN107208720B

CN107208720B - Method for determining a contact point of a hybrid disconnect clutch of a hybrid vehicle

Info

Publication number: CN107208720B
Application number: CN201680008271.9A
Authority: CN
Inventors: 拉夫·曼斯皮尔格; 马库斯·莱恩哈德
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2015-02-11
Filing date: 2016-01-20
Publication date: 2019-12-06
Anticipated expiration: 2036-01-20
Also published as: WO2016127982A1; DE112016000714A5; DE102016200689A1; CN107208720A; DE102016200689B4; KR102532027B1; KR20170115549A

Abstract

The invention relates to a method for determining a contact point of a hybrid clutch of a hybrid vehicle, wherein the hybrid clutch (4) disconnects or connects an internal combustion engine (2) and an electric motor (3) and the contact point (TP) is set while the hybrid vehicle is in operation. In a method for distinguishing between a faulty adjustment of a contact point and a self-regulation of a hybrid separating clutch, the contact point (TPn) determined during the contact point adjustment is checked for plausibility after the contact point adjustment by statistical methods before it is used further.

Description

Method for determining a contact point of a hybrid disconnect clutch of a hybrid vehicle

Technical Field

The invention relates to a method for determining a contact point of a hybrid clutch of a hybrid vehicle, wherein the hybrid clutch disconnects or connects an internal combustion engine and an electric motor, and the contact point is set during operation of the hybrid vehicle.

Background

DE 102010024941 a1 discloses a method for controlling a dual clutch transmission having at least two partial drive trains, wherein each partial drive train can be connected to an internal combustion engine via a clutch. When a vehicle comprising a dual clutch transmission is in motion, the contact point of the clutch is determined independently of the torque of the internal combustion engine. In this case, the contact point is determined when the vehicle starts to operate, and is adjusted during operation of the vehicle.

In a hybrid vehicle with a hybrid drive train, the running resistance can be overcome by converting electrical energy from two separate energy sources, such as fuel for an internal combustion engine and a traction battery for an electric motor, into mechanical energy. DE 102008030473 a1 discloses a method for determining a contact point of an automatic hybrid clutch in a hybrid drive train. The contact point of the hybrid clutch arranged between the internal combustion engine and the electric motor is determined in the off state of the internal combustion engine by slowly closing the hybrid clutch and evaluating the influence of the closed hybrid clutch on the electric machine of the electric motor rotating at a predetermined rotational speed. The hybrid clutch enables a purely electric drive of the hybrid vehicle in the open state, while the torque of the internal combustion engine is directed to the drive wheels in the closed state.

A further task of the hybrid disconnect clutch is to start the internal combustion engine. For this purpose, energy is transmitted to the stationary internal combustion engine and accelerated by a targeted increase in the torque of the electric motor and by closing the hybrid clutch. In this case, the torque transmitted by the hybrid clutch must be known precisely with regard to driving comfort in order to avoid undesirable vehicle accelerations, since the torque of the electric motor can also be transmitted to the drive wheels at the same time.

The contact points represent grid points of a clutch characteristic curve (curve of the clutch torque with respect to the hybrid disconnect clutch path). The adjustment of the contact point is required due to the change in the operation of the clutch during the operation of the hybrid vehicle. This modified clutch operation occurs in particular in the case of automatic adjustment of the clutch as a result of detected clutch wear.

In automatically controlled hybrid separating clutches, a particularly rapid change in the clutch characteristic is caused when the automatic control is carried out in the mechanical device used. In order to suppress such errors, the contact points currently detected according to the known method are not used over the entire range of the clutch characteristic curve but only in a certain part thereof. In this case, the old contact points are weighted more heavily, while the newly determined contact points are only weighted less heavily. As a result, a large error occurs between the requested torque and the adjusted torque.

Disclosure of Invention

The object of the present invention is to provide a method for determining a contact point, in which the error between the requested torque and the set torque at the hybrid separating clutch is reduced.

According to the invention, this object is achieved in that, after the contact point adjustment, the contact point determined during the contact point adjustment is checked for plausibility by statistical methods before it is used further. Statistical methods are considered for performing the plausibility check. The solution is distinguished by the ability to respond to changes by means of significantly different time constants and by the identification and avoidance of the use of erroneous contact points determined by means of a faulty adjustment. Such misadjustment may be caused by an error in signal transmission or by erroneous operation of the higher-order driving strategy. Thus, the accuracy of the contact point is improved when there is a rapid change in the clutch characteristic (e.g., when a self-adjustment of the clutch characteristic occurs). Thus, it is possible to distinguish by software whether the change in the contact point is due to a faulty adjustment of the contact point or due to a self-regulation of the hybrid disconnect clutch.

In one embodiment, a statistical variance is determined from a predetermined number of contact points determined in a plurality of contact point adjustments, wherein a self-adjustment of the hybrid separating clutch is concluded based on the determined statistical variance when there are reliable contact points, and a new contact point is set. The cause of the contact point adjustment of the hybrid separating clutch can be determined simply by the statistical variance, so that it can be determined whether the contact point actually needs to be readjusted.

In one embodiment, the determined statistical variance is compared to a variance threshold, wherein a faulty adjustment of the contact point is inferred if the variance threshold is exceeded, and a self-regulation of the hybrid separating clutch is inferred if the variance threshold is not exceeded. Small changes relative to the previously determined contact point are statistically very common. Through statistical analysis, the contact point approaches the actual physical value over multiple adjustments. By distinguishing between rapid mechanical changes and erroneous adjustments of the contact point due to self-adjustment of the hybrid disconnect clutch, the accuracy of the torque capacity of the controlled hybrid disconnect clutch can be guaranteed at any time without having to make small and very slow changes of the mechanical device with moderately restricted applications.

In one embodiment, the new controlled contact point is determined from an average of a predetermined number of previously determined contact points in the event of a detected self-regulation of the hybrid separating clutch. Since a reliable determination of the self-adjustment of the hybrid clutch is ensured, a more accurate contact point for further operation of the hybrid vehicle can always be set.

In one variant, in the event of a detection of an incorrect adjustment of the contact point, the contact point adjusted before the contact point adjustment is maintained. In this way, the erroneously determined contact point is discarded and disturbances during operation of the hybrid vehicle are eliminated.

In an alternative, in the event of a detection of an incorrect adjustment of the contact point, the contact point closest to the mean value is determined from a predetermined number of contact points and is adjusted to a new contact point. A smooth adjustment of the contact point is thus achieved, which can be attributed to the direct or immediate operating state of the hybrid separating clutch.

In a further alternative, in the event of a detection of an incorrect adjustment of the contact points, at least one contact point with the greatest statistical error is determined from a predetermined number of contact points, which contact point is not taken into account when determining the statistical variance. In this way, erroneously determined contact point values are not calculated at the time of adjustment. If the variance decreases when the values are recalculated, the average of the remaining calculated contact point values is taken as the new contact point.

In one variant, after each contact point adjustment, a difference between the determined contact point and a further contact point (determined during a previous contact point adjustment) is calculated and compared to a contact point difference threshold, wherein the statistical variance is determined only if the difference exceeds the contact point difference threshold. The contact point threshold comparison is an indication of whether there is a large change in contact point. Since the statistical method requires a large amount of calculation time, the statistical method is performed only when a large contact point change is predicted.

In one refinement, during the contact point adjustment, the contact point is determined by a slow actuation of the hybrid separating clutch from the open position to the closed state of the hybrid separating clutch when a defined torque increase is detected. Since the internal combustion engine is not moving during the adjustment of the contact point and only the electric motor is operating, the contact point is inferred from the torque increase, since the torque of the electric motor is then transmitted to the internal combustion engine.

In one embodiment, the contact point adjustment process is repeated in cycles. Such a repetitive cycle is necessary in order to respond to changes in clutch behavior during operation of the hybrid vehicle.

Drawings

The invention has a large number of embodiments. One of which is described in detail in connection with the illustrated drawings. The attached drawings are as follows:

Fig. 1 is a schematic diagram of a hybrid drive.

Fig. 2 is an embodiment of the method according to the invention.

Detailed Description

Fig. 1 shows a schematic diagram of a drive train 1 of a hybrid vehicle. The drive train comprises an internal combustion engine 2 and an electric motor 3. A hybrid separating clutch 4 is arranged directly or directly behind the internal combustion engine 2 between the internal combustion engine 2 and the electric motor 3. The internal combustion engine 2 and the hybrid clutch 4 are connected to each other via a crankshaft 5. The electric motor 3 has a rotatable rotor 6 and a stationary stator 7. The output shaft 8 of the hybrid clutch 4 is connected to a transmission 9, which comprises a connection not shown in more detail, for example a second clutch or a torque converter, which is arranged between the electric motor 3 and the transmission 9. The transmission 9 transmits torque generated by the internal combustion engine 2 and/or the electric motor 3 to drive wheels 10 of the hybrid vehicle. In this case, the hybrid separating clutch 4 and the transmission 9 form a transmission system 11, which is controlled by a clutch actuator 12, for example a hydrostatic clutch actuator.

in order to ensure that, when internal combustion engine 2 is restarted, electric motor 3 can provide sufficient torque from electric motor 3, which not only moves the hybrid vehicle via drive wheels 10 without losing comfort, but at the same time actually also starts internal combustion engine 2, a more accurate knowledge of the clutch characteristic curve of hybrid clutch 4 is required, which is the curve of the clutch torque with respect to the displacement of hybrid clutch 4. The intersection of the clutch characteristic curves is the contact point TP, which is understood to be the position of the hybrid separator clutch 4 at which the friction surfaces of the input or output part of the hybrid separator clutch (4) are in frictional contact with one another.

This contact point TP is particularly relevant for controlling the hybrid separating clutch 4. In this case, the contact point TP can be determined, for example, in a stationary internal combustion engine 2. In order to determine the contact point TP, the clutch torque rating applied to the hybrid separating clutch 4 is increased until a drive torque that can be associated with the clutch torque rating can be measured at the electric motor 3. In this case, it is a prerequisite that the hybrid disconnect clutch 4 is in an open state and then slowly closed under observation of the torque of the electric motor 3. In this case, the electric motor 3 is operated at a controlled rotational speed and therefore has a stable rotational speed. The hybrid separating clutch 4 starts to close until the friction surfaces of the input part and the output part of the hybrid separating clutch 4 are in frictional contact, and a minimum torque, which can be measured by a corresponding reaction of the electric motor 3, is transmitted to the electric motor 3. The corresponding reaction is a defined torque increase output by the electric motor 3. The position of the hybrid disconnect clutch 4 at which the defined torque increase occurs is referred to as the contact point TP.

The hybrid separating clutch 4 is designed in this case as an automatically adjusting clutch, which means that the separating path of the hybrid separating clutch 4 changes automatically when wear occurs. This change must be taken into account in the control of the hybrid separator clutch 4 in order to ensure reliable control. Fig. 2 shows an exemplary embodiment of the method according to the invention, in which it is determined statistically whether a change in the contact point TP is an incorrect adjustment of the contact point TP or a self-regulation of the hybrid separating clutch 4. For this purpose, a contact point adjustment is performed in step 100. Next, in step 110, the contact point TPn determined in the contact point adjustment is compared with the contact point TPn-1, which contact point TPn-1 was determined in the immediately preceding contact point adjustment. From these two contact points, the difference | TPn-1| is derived, which is compared to the contact point threshold STP. If the difference | TPn-TPn-1| is less than the contact point threshold STP, further control of the hybrid disconnect clutch 4 in step 120 retains the contact point TPn-1 on which control is based. However, if the difference | TPn-TPn-1| is greater than the contact point threshold STP, the determined contact point TPn is tested for trustworthiness. For the plausibility test, a statistical method is used, in which in step 130 an average value MTP is determined from predetermined contact points TPn-m that have already been determined in the contact point adjustment. The variance var (tp) of the individual contact points TPn-m with respect to the mean value MTP is then determined in step 140.

In step 150, the variance var (tp) is compared to a variance contact point threshold SV. If the variance var (tp) is less than the variance contact point threshold SV, a new contact point TPn for the further control of the hybrid disconnect clutch 4 is determined in step 160 from the contact points Tn-m on which the mean value MTP is based, wherein the new contact point TPn corresponds to the mean value MTP. If it is determined in step 150 that the variance var (tp) is greater than the variance contact point threshold Sv, the last contact point adjustment may be considered erroneous. The contact TPn is then discarded and the existing contact TPn-1 continues to be used (block 170). However, if the variance var (tp) is smaller, i.e. the individual contact points TPn-m have a smaller value spread with respect to the mean value MTP, it can be assumed that the self-regulation of the hybrid disconnect clutch 4 is carried out due to wear, so that the new contact point TPn is used for further control of the hybrid disconnect clutch 4.

In an alternative to block 170, instead of keeping the old contact point TPn-1 in error, the new contact point TPn +1 is calculated as follows: the contact point TPn-m closest to the mean value MTP serves as the new contact point TPn +1 on which the hybrid disconnect clutch 4 is controlled (block 180). In a further alternative (block 190), the contact point TPn-m is eliminated by the maximum statistical error derived from the calculation when the error adjustment is determined, and an average value MTP is calculated from the remaining contact points TPn-m +1, which is then used as the new contact point TPneu.

After adjusting the contact point TPn, a determination is made of additional contact points for a new contact point adjustment (block 100), and the process is repeated.

The solution shown describes a contact point TP which can be adjusted quickly in the event of a large change in the characteristic curve of the hybrid separating clutch 4, and which can reduce errors which are subject to high safety and process limitations with small deviations. In this way, it is possible to respond to changes in the contact point TP, in particular by means of significantly different time constants.

List of reference numerals

1 drive train

2 internal combustion engine

3 electric motor

4 hybrid disconnect clutch

5 crankshaft

6 rotor

7 stator

8 driven shaft

9 speed variator

10 driving wheel

11 Transmission system

12 clutch actuator

TP contact point

Mean MTP value

VAR (TP) variance

SV variance contact point threshold

STP contact point difference threshold

Claims

1. A method for determining a contact point of a hybrid disconnect clutch of a hybrid vehicle, wherein the hybrid disconnect clutch (4) disconnects or connects an internal combustion engine (2) and an electric motor (3), and the contact point (TP) is adjusted while the hybrid vehicle is running, characterized in that after the contact point adjustment, the contact point (TPn) determined during the contact point adjustment is statistically checked for plausibility before it is used further,

The statistical method is to determine a statistical variance (VAR (TP)) from a predetermined number of a plurality of contact points (TPn-m) determined in different contact point adjustments, wherein, based on the determined statistical variance (VAR (TP)), when a plausible contact point (TPn) is present, a self-regulation of the hybrid separating clutch (4) is deduced and the new contact point (TPn) is used.

2. Method according to claim 1, characterized in that the determined statistical variance (var (tp)) is compared with a variance threshold value (SV), wherein a faulty adjustment of the contact point (TPn) is deduced if the variance threshold value (SV) is exceeded and a self-regulation of the hybrid disconnect clutch (4) is deduced if the variance threshold value (SV) is not exceeded.

3. Method according to claim 1 or 2, characterized in that in the case of a detected self-adjustment of the hybrid disconnect clutch (4), the new adjusted contact point (TPn) is determined from the mean value (MTP) of a predetermined number of previously determined contact points (TPn-m).

4. Method according to claim 2, characterized in that in case an erroneous adjustment of the contact point (TPn) is detected, the contact point (TPn-1) adjusted before the contact point adjustment is retained.

5. Method according to claim 2, characterized in that in the case of a detection of a faulty adjustment of a contact point (TPn), the contact point closest to the mean value (MTP) is determined from a predetermined number of contact points (TPn-m) and is set as the new contact point (TPneu).

6. Method according to claim 2, characterized in that in the case of detection of a misadjustment of a contact point (TPn), at least one contact point with the greatest statistical error is determined from a predetermined number of contact points (TPn-m), which contact point is not taken into account when determining the statistical variance (var (tp)).

7. Method according to claim 1 or 2, characterized in that after each contact point adjustment a difference (| TPn-1|) between the determined contact point (Tn) and a further contact point (TPn-1) determined at the previous contact point adjustment is calculated, which difference is compared with a contact point difference threshold (STP), wherein the statistical variance (var (tp)) is determined only if the difference (| TPn-1|) exceeds the contact point difference threshold (STP).

8. Method according to claim 1 or 2, characterized in that, when a defined torque increase is detected, the contact point (TPn) is determined taking into account the torque of the electric motor (3) by slow operation of the hybrid disconnect clutch (4) from the open position to the closed state of the hybrid disconnect clutch (4) when making contact point adjustments.

9. the method of claim 1 or 2, wherein the contact point adjustment is repeatedly cycled.