Method for simplifying torque monitoring, in particular for hybrid drives

Abstract

In a method for controlling a vehicle drive unit having at least two individual drives and a vehicle control unit, a continuous torque comparison between a permissible torque M.sub.Zul and a further torque is performed by the control unit. The permissible torque M.sub.Zul is continuously compared to setpoint torques M.sub.setpoint,V and M.sub.setpoint,E for the least two individual drives.

Claims

1. A method for torque monitoring of a vehicle drive unit having at least a first drive and a second drive, comprising: ascertaining respective maximum permissible torques for each of the first and second drives in a calculation stage of a control unit; performing a continuous torque comparison in a comparison stage of the control unit (i) between a setpoint torque for the first drive and the ascertained maximum permissible torque for the first drive, and (ii) between a setpoint torque for the second drive and the ascertained maximum permissible torque for the second drive.

2. The method as recited in claim 1, further comprising: ascertaining a summed permissible torque for a combination of the first and second drives in the calculation stage; and ascertaining a summed setpoint torque for a combination of the first and second drives.

3. The method as recited in claim 2, wherein the summed setpoint torque for the combination of the first and second drives is compared to the summed permissible torque for the combination of the first and second drives in the comparison stage.

4. The method as recited in claim 1, wherein the first drive is an internal combustion engine and the second drive is an electric drive, and wherein the setpoint torques for the first and second drives are calculated within the vehicle control unit.

5. The method as recited in claim 1, wherein the setpoint torques for the first and second drives are calculated within the vehicle control unit in a first level which is a functional level, and wherein the setpoint torques for the first and second drives are compared to the ascertained respective permissible torques for the first and second drives in a second level which is a monitoring level.

6. The method as recited in claim 4, wherein the setpoint torques for the first and second drives calculated in the vehicle control unit are compared to respective actual torques of the first and second drives in respective control units assigned to the first and second drives.

7. The method as recited in claim 5, wherein, for the comparison to the ascertained respective permissible torques for the first and second drives, the setpoint torques for the first and second drives are obtained at tap points within the first level which is the functional level.

8. The method as recited in claim 5, wherein the setpoint torques for the first and second drives are transmitted to the comparison stage for continuous torque monitoring, wherein the comparison stage is provided in the second level which is the monitoring level.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows a comparison to be performed within the scope of continuous torque monitoring between permissible torque M.sub.Zul and actual torque M.sub.actual according to the related art.

(2) FIG. 2 shows continuous torque monitoring in which a torque comparison is performed between permissible torque M.sub.Zul and setpoint torque M.sub.setpoint.

DETAILED DESCRIPTION OF THE INVENTION

(3) The illustration in FIG. 1 shows a torque comparison between a permissible torque M.sub.Zul and an actual torque M.sub.actual in a hybrid drive within a vehicle control unit.

(4) A vehicle control unit 10 includes a first level, which is referred to as a functional level, and a second level, indicated by reference numeral 14, which is used as the monitoring level of the first level, reference numeral 12. Vehicle control unit 10 additionally also includes a third level (not shown in FIG. 1), which is used to secure a computer architecture.

(5) Setpoint values 18, in regard to an acceleration of a hybrid vehicle, for example, are transmitted via a gas pedal 16, which is used as the driver input transmission device, to vehicle control unit 10. Within the first level, identified by reference numeral 12, the functional level, a setpoint torque M.sub.setpoint is calculated in a calculation stage 20. Parallel thereto, a permissible torque M.sub.Zul is calculated in a calculation stage 22. The values calculated in calculation stage 20 for setpoint torque M.sub.setpoint, for setpoint torque value M.sub.setpoint,V 38, and setpoint torque value M.sub.setpoint,E 40 are transmitted to a hybrid drive 32, which includes an internal combustion engine 34 and at least one electric drive 36 in the example shown in FIG. 1. Internal combustion engine 34 represents a first torque source and electric drive 36 represents a second torque source.

(6) The values calculated in the second level, reference numeral 14, in calculation stage 22 for permissible torques M.sub.Zul are transmitted to a comparison stage 24. Comparison stage 24 includes an input 26 for the values of permissible torques M.sub.Zul as well as inputs 28 for the values of actual torques of both internal combustion engine 34 and the at least one employed electric drive 36. Hybrid drive 32 may also include two or more electric drives, of course. Actual torque M.sub.actual,V acknowledged via an acknowledgment 42 to comparison stage 24 by internal combustion engine 34, and actual torque M.sub.actual,E acknowledged via an acknowledgment 44 from the at least one electric drive 36 to comparison stage 24 are compared to one another in comparison stage 24 within the second level, reference numeral 14, within the scope of a torque comparison. If the actual torque exceeds the permissible torque, an error response 30 is initiated.

(7) According to the torque comparison shown in FIG. 1, the torque request of setpoint torques M.sub.setpoint,V 38 and M.sub.setpoint,E 40 are transmitted to hybrid drive 32 from vehicle control unit 10. Actual torques M.sub.actual,V 42 and M.sub.actual,E 44 actually output by hybrid drive 32 may deviate from setpoint torques M.sub.setpoint,V 38 and M.sub.setpoint,E 40, however, because the control units of both internal combustion engine 34 and the at least one electric drive 36 of hybrid drive 32 have intrinsic functionalities which increase torque, such as idling regulators, driving aids, and compensators for auxiliary systems, such as radiator fans which turn on, for example, and further electrical consumers which may be switched into the vehicle system of a motor vehicle, such as a rear windshield heater. These deviations, resulting because of the torque-increasing intrinsic functionality, have to be simulated in the calculation of permissible torque M.sub.Zul in the second level, i.e., the monitoring level, reference numeral 14, to prevent an erroneous response of the torque monitoring unit.

(8) FIG. 2 shows torque comparisons between permissible torques M.sub.Zul and setpoint torques M.sub.setpoint within the vehicle control unit.

(9) According to the method of the present invention, the torque values ascertained in calculation stage 20 for particular setpoint torques M.sub.setpoint,V 38 and M.sub.setpoint,E 40 are tapped at tap points 46 and 48 and the particular torque values for setpoint torques M.sub.setpoint,V 38 and M.sub.setpoint,E 40 are supplied within vehicle control unit 10 to comparison stage 24 via signal lines 50. In comparison stage 24, a torque comparison is performed between permissible torque M.sub.Zul in calculation stage 22 of second level, reference numeral 14, and the values ascertained in the first level, functional level, reference numeral 12, in calculation stage 20 for setpoint torques M.sub.setpoint,V 38 and M.sub.setpoint,E 40, without particular actual torque values (compare illustration in FIG. 1) M.sub.actual,V 42 and M.sub.actual,E 44 being taken into consideration. Deviations are thus eliminated, which may result because of torque-increasing intrinsic functionalities of hybrid drive 32, in particular of internal combustion engine 34 or of electric drive 36, so that an erroneous response of the torque monitoring unit may be precluded due to these effects.

(10) The complexity in development and adaptation of the torque monitoring unit may be significantly simplified by the signal flow according to the present invention shown in FIG. 2 within the scope of the method suggested according to the present invention. In particular, a complexity otherwise to be incurred in the second level, i.e., the monitoring level, reference numeral 14, in regard to the simulation of the complete torque intrinsic functionalities of internal combustion engine 34 and at least one electric drive 36 of hybrid drive 32 may be avoided. The simulation of the dynamic torque behavior of both internal combustion engine 34 and electric drive 36 in the second level, monitoring level 14, may also be bypassed following the approach suggested according to the present invention. Furthermore, the approach suggested according to the present invention offers the option of moving the comparison between setpoint torque and actual torque both in regard to internal combustion engine 34 and the at least one electric drive 36 into control units 35, 37 assigned to these units and accordingly moving this comparison out of vehicle control unit 10. An improvement of the modularization of the monitoring concept is thus achieved. A change in the drivetrain of a hybrid drive, given by the use of another electric drive 36, for example, does not require any changes in the first level, reference numeral 12, the functional level, or in the second level, reference numeral 14, the monitoring level.

(11) The continuous torque comparison suggested according to the present invention between setpoint torque M.sub.setpoint,V 38 and M.sub.setpoint,E 40 in comparison stage 24 and permissible torque M.sub.Zul in particular prevents the complexity incurred in replacing units of hybrid drive 32 in the second level, reference numeral 14 (monitoring level) in regard to an adaptation of the intrinsic torque functionality of either internal combustion engine 34 or the at least one electric drive 36. Furthermore, in regard to vehicle control unit 10, two additional interfaces which were necessary in the previous approaches for transmitting actual torque M.sub.actual,V 42 and M.sub.actual,E 44 within the scope of a torque comparison according to the illustration in FIG. 1 are no longer needed. Vehicle control unit 10 performs the torque comparison in comparison stage 24 for continuous torque monitoring between the first level, i.e., the functional level, reference numeral 12, and the second level, i.e., the monitoring level, reference numeral 14, because the values for setpoint torques M.sub.setpoint,V 38 and M.sub.setpoint,E 40 required for comparison in comparison stage 24 are already transmitted within vehicle control unit 10 from the first level, the functional level, into the second level, the monitoring level.

(12) FIG. 2 shows that permissible torques M.sub.Zul are ascertained for all drives, internal combustion engine 34 and the at least one electric drive 36. This means that for every drive present within hybrid drive 32, a separate permissible torque M.sub.Zul especially assigned to this drive is ascertained. Alternatively, a summed permissible torque M.sub.Zul may be ascertained in calculation stage 22, which results from the summation of permissible torques M.sub.Zul of the individual drives used in hybrid drive 32. Two embodiments of the torque comparison in comparison stage 24 result therefrom. On one hand—as shown in FIG. 2—an individual setpoint torque comparison of individual permissible torques M.sub.Zul to M.sub.setpoint,V 38 and M.sub.setpoint,E 40 and on the other hand a total setpoint torque comparison may be performed. In the total setpoint torque comparison, the sum of setpoint torques M.sub.setpoint,V 38 and M.sub.setpoint,E 40—in a hybrid drive 32 having two torque sources—are compared to summed permissible torque M.sub.Zul ascertained in calculation stage 22. Both variants are possible using the method suggested according to the present invention.