DE102007056513B4 - Method for safely determining the speed of a motor vehicle - Google Patents

Abstract

Method for the reliable determination of the speed (v) of a motor vehicle, which is equipped with a dual-clutch transmission (1) and with a sensor AWS which detects an output speed NAus at an output of the dual-clutch transmission (1), independently of the switching state of the double-clutch transmission ( 1) derives the speed (v) of the motor vehicle, wherein the dual-clutch transmission (1) comprises: - a first input shaft (6) and a first partial transmission (9) having a first group of gears - a second input shaft (7) and a second one Partial transmission (10) with a second group of gears and - an output shaft (8) which rotates at the output speed NAus or at a speed NAus *, which is in fixed relation to the output speed NAus, characterized in that at two simultaneously engaged gears with the gear ratios IEin1, IEin2 or after having engaged the gears, carry out the following steps be carried: - the speed No1 the first input shaft (6) is detected by a first input shaft sensor EWS1; - The speed NEin2 of the second input shaft (7) is detected by a second input shaft sensor EWS2; The values NAus or NAus, NEin1 × IEin1 and NEin2 × IEin2 are compared with each other, and based on the comparisons, a faulty sensor is identified, as long as two of the three values agree that a single gear is engaged in the second partial transmission (10) in the first partial transmission (9) is inserted when the output speed NAus or the speed NAus * deviates from the value NEin2 × IEin2, and that in only one gear engaged in the first partial transmission (9) a gear in the second partial transmission (10) is inserted if the output speed NAus or the speed NAus * deviates from the value NEin1 × IEin1.

Description

The invention relates to a method for the reliable determination of the speed of a motor vehicle, which is equipped with a dual-clutch transmission.

In automatic transmissions, the vehicle speed is used for various processes in the transmission control, such. As the selection of the circuit diagram, the selection of the approach strategy or the detection of blocking wheels. For this reason, it is necessary to be able to reliably determine the vehicle speed at any time. The speed is usually determined via a sensor on the transmission output or via the ABS system. If the sensor provided for the speed determination fails completely due to an error or if it gives noticeably false signals, the speed must be determined in another way.

From the DE 34 47 626 C2 For example, a method is known in which, in the event of a disturbance of the vehicle speed signal or of the input shaft speed signal, the disturbed signal is replaced by a corrected signal calculated from the undisturbed other signal and from the transmission ratio. When disturbed, one of the two mentioned signals is interpreted as being smaller than a threshold value assigned to it, while at the same time the other signal is greater than a threshold assigned to it, whereby the transmission must not be in the neutral or neutral position.

In the DE 691 16 449 T2 There is disclosed a method of controlling a gearshift operation in which, after an instruction for shifting the transmission from an idle position to a position other than the idling position has been generated, the vehicle gearbox first shifts to a prescribed high gear position and then the vehicle speed is calculated from the rotational speed on the input side of the transmission or the gear ratio device while the transmission or the gear ratio is in the prescribed high gear position.

A disadvantage of the known from the prior art method is that a comparison of the signal of the speed sensor with the signal determined from the input shaft speed of the transmission and the gear ratio, although an error can be detected, the unique assignment of the error to one of the two sensors However, sometimes difficult on the input or output side of the transmission. In the in the DE 34 47 626 C2 described method is z. B. then replaced the wrong signal when the signal error is that too high a speed is displayed at a standstill.

In the DE 10 2004 039 273 In a dual-clutch transmission with two input shafts and two partial transmissions by sensors, the speeds of the two input shafts are determined. As far as a gear is engaged in each partial transmission, the measurement results of the two sensors can be compared taking into account the ratios of the engaged gears. However, even if deviations occur, an error can be detected here, but not assigned to a sensor.

From the EP 0 459 274 A2 a method is known, which are checked by means of three sensors, the speeds in a drive train of a motor vehicle. In this case, a first sensor detects the rotational speed of a motor shaft, a second sensor detects the rotational speed of a countershaft of a transmission, and a third sensor detects the rotational speed of a propeller shaft. By comparing the measurement results of the individual sensors, taking into account the gear ratios in the drive train, a defective sensor can be identified. The drive train must be closed. In this case, arranged between the engine shaft and transmission clutch of the drive train must be closed and a gear engaged in the transmission.

From the DE 34 47 626 C2 is also known to replace the measurement results of a sensor identified as defective by calculated values.

Accordingly, the determination of the vehicle speed according to the known from the prior art method can not always be done reliably.

The object of the present invention is to provide a method with which the speed of a motor vehicle equipped with a dual-clutch transmission can be reliably determined.

This object is achieved by a method having the features of claim 1. Advantageous embodiments of the method are the subject of the dependent claims.

A dual clutch transmission includes a first input shaft and a first partial transmission with a first group of gears, a second input shaft and a second partial transmission with a second group of gears and an output shaft which rotates with the output speed N _from or at a speed N _{Off *,} the to Output speed N _{Off is} in fixed ratio. From the detected via a sensor at an output of the double clutch transmission output speed N _{out of} or from the rotational speed N _{from *} the speed of the motor vehicle can be derived.

• – die Drehzahl N_Ein1 der ersten Eingangswelle wird durch einen ersten Eingangswellen-Sensor EWS1 erfasst;
• – die Drehzahl N_Ein2 der zweiten Eingangswelle wird durch einen zweiten Eingangswellen-Sensor EWS2 erfasst;
• – die Werte N_Aus bzw. N_Aus*, N_Ein1 × I_Ein1 und N_Ein2 × I_Ein2 werden miteinander verglichen, und anhand der Vergleiche wird ein fehlerhafter Sensor identifiziert, soweit zwei der drei Werte übereinstimmen.

The method according to the invention is now characterized in that the following steps are carried out with two gears engaged simultaneously with the gear ratios I _Ein1 , I _Ein2 or after the gears have been _engaged :

• The rotational speed N _{Ein1 of} the first input shaft is detected by a first input shaft sensor EWS1;
• - The speed N _{Ein2 of} the second input shaft is detected by a second input shaft sensor EWS2;
• The values N _Out or N _{Out *} , N _In1 × I _In1 and N _In2 × I _In2 are compared with each other, and from the comparisons a faulty sensor is identified as far as two of the three values agree.

If one of the three sensors is faulty, it can be uniquely identified by means of this "2-out-of-3 selection". Is z. For example, if the value N _Ein1 × I _{Ein1 deviates} from the value N _Aus or N _{Aus *} , and the value N _Ein2 × I _{Ein2 agrees} with the value N _Aus or N _{Aus *} , then the value is clearly Sensor EWS1 faulty, if one disregards the extremely unlikely event that there is an error in each of the two sensors EWS2 and AWS, which falsifies the values N _out or N _{out *} and the value N _Ein2 × I _{Ein2 to} the same extent.

If only one gear is engaged in the second partial transmission, the values N _Ein2 × I _Ein2 and N _Aus or N _{Aus * are first} compared according to the invention. If these two values deviate from each other, one of the two sensors EWS2, AWS is faulty. In order to identify the faulty sensor, the method provides that a gear is engaged in the first partial transmission, whereby now also the comparison of the two said values with the value N _Ein1 × I _Ein1 and thus an identification of the faulty sensor is possible.

Conversely, if only one gear is engaged in the first partial transmission and the values N _Ein1 × I _Ein1 and N _Aus or N _{Aus * differ from} each other, according to the invention a gear is engaged in the second partial transmission and the two values are compared with the value N _Ein2 × I _In2 , whereby the faulty sensor can be detected.

In an advantageous embodiment of the method according to the invention, upon identification of a faulty sensor, the speed detected by this faulty sensor is substituted by a calculated value which can be derived from the detected rotational speed of one of the other two sensors. In the case of an error in the sensor AWS can thus be ensured in particular that the space required for the derivation of the vehicle speed value of the output speed N _out and the rotational speed N _{Off *} is at all times reliably.

In the event that none of the three values N _Aus or N _Aus , N _Ein1 × I _Ein1 and N _Ein2 × I _{Ein2 coincides} with at least one other of these three values, the method provides for the decommissioning of the motor vehicle. In the absence of any agreement between the values, it can not be discriminated whether two or all three sensors are faulty. In particular, it is not to be decided whether the signal supplied by the sensor AWS, from which the vehicle speed is derived, is correct. The vehicle speed, in turn, is, as already said, required for various processes in the transmission control. If the vehicle speed is not available safely, the motor vehicle is thus shut down in order to avoid possible damage to the gearbox.

If the method according to the invention is to be applied from a situation in which no gear is engaged, for example because the vehicle is rolling down an incline without the gear engaged, then preferably the highest gear of the dual-clutch gearbox is initially engaged. This prevents a gear-damaging situation in which the vehicle speed is too high for the engaged gear.

Preferably, in the situation just described in the first or second partial transmission is minimally inserted in comparison to that in the other partial transmission already engaged gear next lower gear, so as not to damage the transmission.

In the following, the method according to the invention will be explained in more detail by means of an exemplary embodiment and with reference to the accompanying drawings. Show it:

1 a drive scheme of a dual-clutch transmission;

2 FIG. 3 is a flowchart for illustrating a sequence of the method according to the invention and FIG

3 FIG. 3: a further flow chart which represents a query routine in which the method according to the invention is embedded.

1 shows a drive diagram of a dual-clutch transmission, in its entirety with 1 is called and can be used for example as an automated manual transmission in a motor vehicle. It includes a first clutch 2 and a second clutch 3 , At an entrance side 4 of the dual-clutch transmission 1 there is an engine 5 ,

The first clutch 2 is a first input shaft 6 , the second clutch 3 a second input shaft 7 assigned. In the area of the first input shaft 6 is arranged a first input shaft sensor EWS1, which is the rotational speed N _{Ein1 of} the first input shaft 6 detected. Accordingly, in the region of the second input shaft 7 a second input shaft sensor EWS2 arranged, which is the rotational speed N _{Ein2 of} the second input shaft 7 detected.

Between the first input shaft 6 and an output shaft 8th is a first partial transmission 9 arranged, by the different ratios I _Ein1 between input shaft 6 and output shaft 8th can be realized. This partial transmission 9 carries the odd gears I, III, V, R. Further gear ratios I _Ein2 are through a second partial transmission 10 allows that between the second input shaft 7 and the output shaft 8th is provided and the straight gears II, IV, VI carries.

In the area of the output shaft 8th a sensor AWS is provided which detects an output speed N _out . From this output speed N _out can be independent of the switching state of the dual clutch transmission 1 derive the speed v of the motor vehicle. The vehicle speed v determined via the sensor AWS is used for various processes in the transmission control.

The following on the basis of 2 and 3 The inventive method described ensures that the vehicle speed v one with a dual-clutch transmission 1 equipped vehicle can be reliably determined at any time of the journey.

2 shows a flowchart illustrating the flow of the inventive method, wherein in the first partial transmission 9 a gear with the gear ratio I _Ein1 and in the second partial transmission 10 a gear with the gear ratio I _{Ein2 is} inserted. In one step 11 First, the values N _In1 × I _In1 and N _In2 × I _In2 are compared with each other. If these do not differ, will be in one step 12 the value N _Ein1 × I _{Ein1 is compared} with the value N _Aus . If these two values are the same, then it is a normal ride where all the sensors work and the process is ended. Will in step 12 a deviation of the two values determined from each other, so must due to the positive agreement in step 11 the sensor AWS be faulty, which detects the speed N _out . Accordingly, in one step 13 the value N _{out is} replaced by the value N _In1 × I _In1 before the procedure is terminated.

The values N _Ein1 × I _In1 and N _Ein2 × I _In2 already _disappear in step 11 from each other, so will in one step 14 the value N _Ein1 × I _{Ein1 is compared} with the value N _Aus . If these two values match, the sensor EWS2 is faulty and the speed N _Ein2 detected by this sensor becomes one step 15 is replaced by the value N _out / I _in2 before terminating the procedure. Will both in step 11 as well as in step 14 a deviation of the respectively compared values from each other determined, so is in one step 16 the value N _Ein2 × I _{Ein2 compared} with the value N _Aus . If these two values do not agree either, then there is a double error, ie at least two of the three sensors AWS, EWS1, EWS2 are faulty. Since it can not be decided which at least two sensors are faulty, the vehicle in this case becomes in one step 17 shut down and the process is terminated. The two in step 16 On the other hand, if the values compared with each other are the same, the sensor EWS1 is faulty and the rotational speed N _Ein1 detected by this sensor becomes one step 18 is replaced by the value N _off / I _on1 before terminating the process.

In 3 is a query routine 100 illustrated in the form of a flow chart in which the inventive method is embedded. Through this query routine 100 it is ensured that the necessary for the application of the method according to the invention condition of the insertion of two gears from any driving situation out is met.

In one step 101 is first queried whether a circuit is performed. If this is not the case, it will be in one step 102 checked if only one gear is engaged. If this is not the case, then it will be in one step 103 checked if no gear is engaged. If this is not the case, it will be in one step 104 queried whether gear position sensors indicate that two gears are engaged. If this is the case, two gears are engaged and a subroutine "normal drive" is called, whereby the method according to the invention is started and as in 2 can run described.

Will the in step 104 answered query with no answers, so must a gear in one of the two partial transmission 9 . 10 to have jumped out. In one step 105 this gear is re-engaged and the routine 100 will with step 101 restarted.

Will the in step 103 answered query answered yes, so is in any of the two partial transmission 9 . 10 a gear. In one step 106 Then the sixth and thus highest gear is engaged before the routine 100 with step 101 is restarted. At this restart of the routine 100 Now the query in step 102 answered with yes. In one step 107 it is checked whether the values N _Ein2 × I _Ein2 and N _Aus match. If this is the case, the two sensors AWS and EWS2 work without errors and the routine 100 can be restarted to continuously check the functionality of the sensors. _If the values N _Ein2 × I _Ein2 and N _Aus do not match, then one of the two sensors AWS, EWS2 is faulty. In order to identify the faulty sensor, in one step 108 the routine 100 another gear engaged, at least the next lower, to the partial transmission 9 . 10 not to harm. The routine 100 will then be restarted, but now due to the two in-going gears over the steps 101 . 102 . 103 . 104 to call the subroutine "normal ride". As described above, with the aid of this subroutine, the faulty sensor can be identified.

Will be in the routine 100 already in step 101 answered query after the implementation of a circuit with yes answered, so will in one step 109 checked whether one of the sensors AWS, EWS1, EWS2 is clearly defective. If this is not the case, the routine starts 100 again. Instruct the query in step 109 however, on a sensor defect, so in step 110 an action-specific reaction in which the signals can be frozen, substituted or ignored before the routine 100 is restarted.

LIST OF REFERENCE NUMBERS

1

Double clutch

2

first clutch

3

second clutch

4

input side

5

engine

6

first input shaft

7

second input shaft

8th

output shaft

9

first partial transmission

10

second partial transmission

EWS1

first input shaft sensor

EWS2

second input shaft sensor

N _Ein1

Speed of the first input shaft

N _Ein2

Speed of the second input shaft

I _ein1

Transmission ratio of the first partial transmission

I _ein2

Transmission ratio of the second partial transmission

AWS

Output shaft sensor

N _off

Speed of the output shaft

11-18

Process steps of the method according to the invention

100

scan routine

101-110

Query steps of the query routine 100

Claims (5)

Method for the reliable determination of the speed (v) of a motor vehicle which is equipped with a dual-clutch transmission ( 1 ) and a sensor AWS, which is connected to an output of the dual-clutch transmission ( 1 ) detects an output speed N _out , from which regardless of the switching state of the double clutch transmission ( 1 ) derive the speed (v) of the motor vehicle, wherein the dual-clutch transmission ( 1 ) comprises: - a first input shaft ( 6 ) and a first partial transmission ( 9 ) with a first group of gears - a second input shaft ( 7 ) and a second partial transmission ( 10 ) with a second group of gears and - an output shaft ( 8th ), The _* rotating at the output speed N _from or at a rotational speed N _of which is to output speed N _out in fixed relationship, characterized in that the at two simultaneously engaged gears with the speed ratios I _Ein1, I _Ein2 or after completion of loading The following steps are performed: - the rotational speed N _{Ein1 of} the first input shaft ( 6 ) is detected by a first input shaft sensor EWS1; The speed N _{Ein2 of} the second input shaft ( 7 ) is detected by a second input shaft sensor EWS2; The values N _out or N _out , N in ₁ x I in ₁ and N in ₂ x I in ₂ are compared with each other and from the comparisons a faulty sensor is identified, as _long as two of the three values agree that with only one gear engaged in the second one Partial transmission ( 10 ) a gear in the first partial transmission ( 9 ) is engaged when the output speed N _Aus or the speed N _{Aus *} deviates from the value N _Ein2 × I _Ein2 , and that with only one gear engaged in the first partial transmission ( 9 ) a gear in the second partial transmission ( 10 ) is set when the output rotational speed N _Aus or the rotational speed N _{Aus *} deviates from the value N _Ein1 × I _Ein1 . A method according to claim 1, characterized in that when identifying a faulty sensor detected by this faulty sensor speed is substituted by a calculated value, which can be derived from the detected speed of the two other sensors. A method according to claim 1 or 2, characterized in that the motor vehicle is shut down when none of the three values N _Aus or N _{Aus *} , N _Ein1 × I _Ein1 and N _Ein2 × I _{Ein2 coincides} with at least one other of these three values. Method according to one of claims 1 to 3, characterized in that at no engaged gear, the highest gear of the dual-clutch transmission ( 1 ) is inserted. Method according to one of claims 1 to 4, characterized in that in the first or second partial transmission ( 9 . 10 ) minimally a smaller neighbor passage is inserted.

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