DE102005062871A1 - Multi-drive e.g. hybrid drive, controlling method for use in hybrid vehicle, involves determining reliable negative moment of power train, and comparing negative moment with actual effective moment or actual target moment of hybrid drive - Google Patents

Abstract

The method involves connecting a brake control unit and a vehicle control unit with each other by a vehicle-bus-system, and determining a reliable negative moment of a power train. The negative moment is compared with an actual effective-moment or to the actual target moment of a hybrid drive. The effective and the negative moments are read in a monitoring plane of the vehicle control unit. The negative moment marks a boundary between uncritical and critical moment ranges (36, 38) of a moment target range (30) of a hybrid drive.

Description

The The invention relates to a method for monitoring negative moments in hybrid vehicles equipped with a hybrid drive.

was standing of the technique

Out DE 103 20 017 A1 a control device for the drive unit of a motor vehicle is known, wherein the control device controls or controls the drive unit, in particular with regard to an output drive torque, and the drive unit is an internal combustion engine of a motor vehicle. In this case, the motor vehicle usually comprises a driver request transmission device which can be actuated by the driver of the motor vehicle, in particular an accelerator pedal which can be actuated with the foot. This is intended to deliver an output signal representing a momentary actuation state of the driver request transmission device. A control unit receives the output signal from the driver request transmission device and assigns to the received output signal at least one desired output variable, which is in particular a desired drive torque of the drive unit. The drive unit is controlled by the control device in such a way that an actual output quantity output by the drive unit approaches the desired output variable. Such control devices are known in various designs for common motor vehicle engines, in particular Otto engines and diesel engines, for example Bosch engine control systems with electronic accelerator pedal (EGAS).

Further It is known to detect continuous torque monitoring Malfunctions in control units perform. This serves to protect passengers in the vehicle and the Protection of external road users. Through continuous torque monitoring Should an unwanted acceleration of the vehicle be avoided. The core of continuous torque monitoring lies in a comparison an actual torque provided by the engine with a permissible moment. Normally, the actual torque is smaller than the permissible torque. If the actual moment is the allowed one Moment exceeds, there is a fault in the engine control unit and a leading to a safe vehicle condition error response is initiated. The supervision The engine control units usually takes place according to a three-level monitoring concept. The engine control itself, in particular the specification of the desired torque, takes place in the designated as a functional level first level. The second level (monitoring level) is executed as the continuous torque monitoring. In This level will depend, inter alia, on vehicle and vehicle Motor functions a permissible Moment determined and compared with an engine-actual torque. The second level is extensively secured by a third level, for example, by double storage of all variables, a cyclic RAM or ROM check, program sequence checks as well as command tests.

DE 197 39 565 A1 has a method for controlling the torque of a drive unit of a motor vehicle to the object in which the torque of the drive unit is set at least in accordance with the driver's request, the actual torque of the drive unit is determined and at least on the basis of the driver's request, a maximum allowable torque is determined , There is a torque reduction and / or limitation when exceeding the maximum allowable torque by the actual torque. In this case, at least one operating state is determined, in which the torque of the drive unit is increased by additional load. During this at least one operating state, the maximum permissible torque is increased. In particular, the permissible torque is thereby increased during operation with a cold drive unit and / or load-consuming consumers during operation.

The described from the prior art method of torque monitoring are not readily transferred to hybrid vehicles. In hybrid vehicles, at least one additional torque source (motor) is used in addition to an internal combustion engine. In most cases this is an electric drive. In the engine control or better vehicle control, the desired torque required by the driver, which is set, for example, by operating an accelerator pedal, must now be divided between the existing torque source, which comprises at least two motors. This is done as a function of numerous environmental variables, inter alia, with the aim of setting the most fuel-efficient operating point for all torque sources, ie drive motors. The core of the continuous torque monitoring mentioned above is the torque comparison in the second level, the monitoring level, in which a permissible moment of the second level (monitoring level) is compared with an actual torque in the second level (monitoring level). If the actual torque exceeds the permissible torque, a corresponding error reaction is initiated. The calculation of the permissible torque in the second level (monitoring level) maps the functionality of the first level, the functional level. In the second level (monitoring level), the calculations from the first level (function level) are carried out again, but greatly simplified to errors possibilities to reduce.

Core of previously implemented continuous torque monitoring is a torque comparison in the second level, ie the monitoring level, within which it is checked whether an actual torque of the second level, ie monitoring level, is smaller than an allowable torque M _zul , which is also in the second level , the monitoring level, is determined. If the actual torque is greater than the permissible torque M _zul , an error reaction is initiated in which, for example, the internal combustion engine of a hybrid drive is switched off via a few intermediate stages and the remaining, weakly negative drag torque of the internal combustion engine slowly brings the vehicle to a standstill. The weak negative drag torque of the internal combustion engine is caused by compression losses, engine friction and by a moment, which is generated by ancillaries, such as a high-pressure fuel pump. So far, the engine control unit can request moments in the entire torque range of the internal combustion engine. Critical to safety are only erroneously too high moments, which are detected in the context of a continuous torque monitoring. The leading to a vehicle deceleration negative moments of the internal combustion engine, however, are uncritical, since the amount is small and a faulty negative acceleration of the vehicle for the driver is relatively easy to control.

In However, hybrid vehicles add torque ranges of Moment adjuster, d. H. a at least one internal combustion engine and at least one electric drive. In the case of a parallel hybrid drive a simple addition of the torque adjustment ranges, in the case of power split hybrid drives is the formation of the resulting Moment more complex. The torque adjustment ranges of the control unit at Vehicle control are for the case of hybrid drives strong against a control of an internal combustion engine elevated, because of the at least one electric drive of the hybrid drive in the Able to provide a very strong negative moment. These Property is exploited in regenerative braking to the at the vehicle deceleration released energy in electrical energy storage, such as Example of the vehicle battery, caching. kick an error in the vehicle control on the one to a strongly negative Moment of electric drive leads, this turns out to be the driver's unintentional response Brakes. A hazard can both for enter the driver and the vehicle, so in terms of loss the driving stability or an overreaction of the Driver on the unintentional response of the brakes. A danger can also for hire other road users as it is due to unintentional Response of the brakes of a vehicle in front quickly come to a rear-end collision or a provoked evasive maneuver can. This type of fault occurs in the control of hybrid powertrains with respect to faulty high torque in conventional powertrains added.

Regarding the current solutions There is a need for hybrid drives in vehicle controls of hybrid vehicles in addition to faulty high torque through the to intercept previous continuous torque monitoring, therein also erroneously detect too low moments. Since the at least an electric drive of a hybrid drive due to the regenerative Braking, d. H. in the feeding of electrical energy into one Latch, an incentive to use the hybrid drive at Represents vehicles are caused by unintentional braking vehicle instabilities and an inherent threat other road users and the vehicle occupants effectively exclude.

presentation the invention

Following the proposed invention, a permissible negative summation torque is determined and checked whether the current negative total torque of the hybrid drive is greater than the permissible negative driveline torque. By comparing a determined permissible negative summation torque of the hybrid drive with the respective prevailing summation torque of the hybrid drive can be intercepted erroneously too low torque, whereby the occurrence of a critical vehicle condition can be effectively prevented. Is, for example, the permissible negative torque M _zul = -100 Nm, the actual torque of the at least one electric drive, for example, -200 Nm, the actual torque of the internal combustion engine 150 Nm, so there is a resultant torque of the hybrid drive from -50 Nm, which is above the permissible negative moment M _zul of -100 Nm. There is therefore no error here. However, in this example, if the actual torque of the internal combustion engine is 0 Nm, the actual torque of the at least one electric drive is -200 Nm, the resulting torque of -200 Nm exceeds the allowable torque of -100 Nm, resulting in occurrence of a critical driving condition could. By the method proposed according to the invention, however, this error case is excluded by continuous torque comparison. With the method proposed according to the invention, however, only the negative moment of the at least one electric drive can be continuously monitored.

Following the method proposed according to the invention, in particular a permissible negative drive train torque is formed. The negative driveline torque trq _{MIN, ZUL} is _requested by the vehicle _{control unit} via the vehicle bus system, for example via a CAN bus. The information about the negative drive train torque can be read into the second level, ie monitoring level, of the vehicle control unit and at the same time also in the first level, ie the functional level of the vehicle control unit. The permissible negative driveline torque trq _{MIN, ZUL} is then obtained as the sum of the requested torque and a negative offset according to the following relationship: trq MIN, ZUL = trq BRK, CAN + trq OFFS

Thus, in deviation from the usual signal way, according to which the signals of the brake pedal are processed by the brake control unit and are converted into a braking torque, which is divided on the actuator, the largest possible share be taken from the drive train. The proportion of the braking torque which is to be applied by the drive train is obtained from the drag torque of the at least one internal combustion engine and the negative torque which is applied by the at least one electric drive. This fraction of the braking torque to be applied by the drive _{train is} limited by the permissible negative drive train torque trq _{MIN, ZUL} according to the relationship given above.

drawings

Based In the drawings, the invention will be described in more detail below.

It shows:

1 The torque setting range of an internal combustion engine with a positive torque range and a negative torque range,

2 the torque setting range of an electric drive with symmetrical positive and negative torque ranges,

3 the torque adjustment range of a multiple drive, in particular a hybrid drive and

4 an assessment of the torque setting range of a hybrid powertrain with critical and uncritical torque ranges.

embodiments

1 shows the representation of a torque adjustment range of an internal combustion engine with positive and negative proportions.

A torque range 10 an internal combustion engine is characterized by a pronounced positive torque range 12 and a negative torque range 14 , According to the torque / speed characteristic, an internal combustion engine has a torque curve 18 on the off 1 emerges and is characterized by a maximum torque M _max . The maximum 20 the torque is usually in the middle speed range. An internal combustion engine may also generate a negative, ie braking, torque which is within the negative torque range 14 according to the diagram 1 lies. The weak negative torque of an internal combustion engine is also referred to as drag torque and arises due to compression losses of engine friction and a braking torque of a high-pressure fuel pump, to name just a few examples. This in 1 with reference number 16 identified engine drag torque brakes an internal combustion engine take the gas away, ie, for example, in a downhill driving, in which the driver of the vehicle takes his foot off the accelerator pedal and consequently no fuel is injected and the internal combustion engine, the vehicle in a downhill drive through the engine drag torque 16 slows. The absolute amount of engine drag torque 16 is considerably smaller than the absolute amount of the maximum torque 20 the internal combustion engine. The positive moment range 12 the internal combustion engine is the negative torque range by the curve trq _{ENG, MAX} 14 the internal combustion engine by the curve train trq _{ENG, MIN} limited. An engine control unit of a vehicle can have torques in the entire torque range 10 the internal combustion engine are, request. Critical to safety are only erroneously too high moments, which is why in modern engine control units, a continuous torque monitoring is implemented. The leading to a vehicle deceleration negative moments in the negative torque range 14 of the torque range 10 according to 1 are uncritical, because on the one hand the amount is small and a faulty negative acceleration for the driver of a vehicle is well manageable.

The representation according to 2 is a torque adjustment range of an electric drive refer.

A torque range 22 an electric drive shows a positive torque range 24 as well as a negative torque range 26 with respect to an axis of symmetry 28 , ie the zero moment M _{0 are} symmetrical. The course of the maxi malmomentes of the electric drive is indicated by trq _{ELM, MAX} , the minimum torque of the electric drive through the curve trq _{ELM, MIN} Compared to in 1 illustrated torque adjustment range 10 the internal combustion engine is the torque maximum of the torque of the electric drive trq _{ELM, MAX} at low speeds. Characteristic of an electric drive is the fact that the maximum moments generated by this, both in the positive torque range 24 as well as in the negative torque range 26 are symmetrical to each other, ie, and an electric drive can apply much higher negative moments compared to the drag torque 16 an internal combustion engine like in 1 shown.

From the illustration according to 3 shows that in a hybrid drive the torque ranges 10 respectively. 22 according to the 1 and 2 overlap. In the case of a parallel hybrid drive, the superposition is a simple addition of the torque ranges 10 and 22 If this is a power-split hybrid drive, the superimposition of the torque setting ranges follows 10 . 22 taking into account the coupling conditions of at least one internal combustion engine and at least one electric drive. From the illustration according to 3 shows that in the case of a multiple drive, such as a hybrid drive for a control unit of the vehicle control or the engine control unit with respect to a control of an internal combustion engine adjusts a greatly increased torque adjustment range. As shown in the illustration 3 is removable, includes a torque adjustment range 30 a hybrid drive a positive torque range 32 as well as a negative torque range 34 , The positive moment range 32 of the hybrid drive is limited by the sum maximum torque of the hybrid drive trq _{SUM, MAX} , the minimum torque of the hybrid drive by the curve trq _{SUM, MIN} . Due to the high initial torque of at least one electric drive of a hybrid drive, a high value for the total torque of the hybrid drive trq _{SUM, MAX} arises at low torques. Due to the decreasing maximum torque of the electric drive trq _{ELM, MAX} with increasing speeds, the maximum torque of the hybrid drive trq _{SUM, MAX} falls with increasing speed to assume its maximum value when reaching the maximum torque of the internal combustion engine M _MAX .

Since the electric drive as shown in 2 especially at low speeds can provide a strong negative, braking moment, corresponding to the negative torque range 26 of the electric drive in 2 There curve trq _{ELM, MIN} , has the negative torque range 34 of the hybrid drive as shown in FIG 3 a pronounced negative torque range 34 on. This property of a hybrid drive is exploited in regenerative braking. The energy released during the vehicle deceleration can be temporarily stored in this drive concept in electrical energy storage devices, such as the vehicle battery or other electrical energy storage devices. From the illustration according to 3 shows that the course of the minimum torque of the hybrid drive trq _{SUM, MIN} due to the negative torque range 26 of the electric drive (see illustration according to 3 ) the engine drag torque 16 the internal combustion engine in terms of absolute value significantly exceeds.

The representation according to 4 is to take an evaluation of the respective torque ranges of the torque adjustment range of a hybrid drive.

The in 4 illustrated torque adjustment range 30 a hybrid drive corresponds to the torque adjustment range 30 according to 3 , The positive moment range 32 of the hybrid drive is limited by the sum maximum torque of the hybrid drive trq _{SUM, MAX} , while the negative torque range of the hybrid drive is limited by the summation minimum torque of the hybrid drive trq _{SUM, MAX} . At low speeds are the respective torque ranges 32 . 34 of the hybrid drive dominated by the moment components of the electric drive. If a fault occurs in the vehicle control, which leads to strong negative moments of the electric drive, especially at low speeds, so this effect is the driver as an unintentional response of the brakes. Although the driver has not operated the brake pedal, the vehicle decelerates. This sudden deceleration of the vehicle can result in danger to both the driver and the vehicle due to a loss of driving stability, and to an overreaction of the driver. Furthermore, an unintended response of the brakes can also pose a danger to other road users, such as causing a rear-end collision and provoking an evasive maneuver. This type of failure is intercepted by multiple drives, such as hybrid drives, in order not to sacrifice the advantage of regenerative braking with energy buffering as an incentive to use hybrid drives. As shown in the illustration 4 shows, the torque adjustment range 30 the hybrid drive on both sides of a zero moment M ₀ an uncritical torque range 38 on. The uncritical moment range 38 The hybrid drive is characterized by weak positive or weak negative moments of both the internal combustion engine and the at least one electric drive bes marked. Within the uncritical torque range 38 the leading to a vehicle deceleration negative moments of both the internal combustion engine and the at least one electric drive are not critical, since they are seen from the absolute amount, small and a faulty negative acceleration for the driver is well manageable.

For hybrid drives, due to the circumstances set out above, care must be taken to ensure that critical ranges of torque 36 both in terms of the positive torque range 32 the hybrid drive and in particular with regard to the negative torque range 34 be monitored the hybrid drive. For this purpose, a permissible negative torque trq _{MIN, ZUL is} formed and _checked whether the currently prevailing actual torque of the hybrid drive is greater than the permissible negative torque trq _{MIN, ZUL} . Instead of checking the current actual torque of the hybrid drive, the current setpoint torque, ie the torque requirement for the individual drives of the hybrid drive can also be compared with the permissible negative torque trq _{MIN, ZUL} . This can be intercepted erroneously too low torque, which can prevent a critical vehicle condition of a vehicle with hybrid drive. Although negative moments can be requested by the driver to a lesser extent via the accelerator pedal, these negative moments are within the non-critical torque range 38 as shown in 4 , This can be done, for example, by simply removing the gas, resulting, for example, in the aforementioned engine drag torque 16 due to engine friction, the then occurring compression losses of the internal combustion engine and a moment of the high-pressure fuel pump adjusts. Only the operation of the brake pedal leads in hybrid drives to increased regenerative braking due to the high negative torque, which can make the electric drive of the hybrid drive. As a result, the signals of the brake pedal are processed as before by the brake control unit and converted into a corresponding braking torque. The braking torque can be divided among the actuators, for example by the largest possible proportion of the braking torque from the drive train, ie the engine drag torque 16 the internal combustion engine or a negative moment of the electric drive, is applied. The remaining part of the braking torque is applied in this case by the brakes.

The permissible negative driveline torque can be requested via the vehicle bus system, such as a CAN bus from the vehicle control unit. The negative driveline torque can be read within the vehicle control unit both in its level 1, ie functional level, as well as in its second level, ie the monitoring level. The permissible negative driveline torque is the sum of the requested torque, ie the negative driveline torque trq _{BRK, CAN} and a negative offset trq _OFFS . trq MIN, ZUL = trq BRK, CAN + trq OFFS

The negative offset trq OFFS _avoids a premature response of the torque _monitoring with small deviations in the torque calculation. In accordance with the permissible negative torque trq _{MIN, ZUL} determined in the above relationship, in the second level, the monitoring level of the vehicle control unit, both the current actual torque of the hybrid drive and the currently requested setpoint torque of a hybrid drive can be checked for impermissibly high negative torque values so that critical vehicle conditions a risk and thus a risk to the driver and passengers and a risk to external road users is excluded.

Claims (10)

Method for controlling a multiple drive, in particular a hybrid drive with at least one internal combustion engine and with at least one electric drive, a brake control unit and a vehicle control unit with a functional level and a monitoring level, wherein the brake control unit and the vehicle control unit via a vehicle-bus system are in communication, thereby in that a permissible negative torque trq _{MIN, ZUL of} the drive train is determined and continuously compared with the current actual torque or the current desired torque of the hybrid drive. Method for controlling a multiple drive according to claim 1, characterized in that the permissible negative torque trq _{MIN, ZUL is determined} with a negative driveline torque trq _{BRK, CAN} . Method for controlling a multiple drive according to claim 1, characterized in that the permissible negative torque trq _{MIN, ZUL} with a negative driveline torque trq _{BRK, CAN} and addition of a negative offset value trq _{OFFS is} determined. Method for controlling a multiple drive according to claim 2, characterized in that the current actual torque of the hybrid drive and the negative driveline torque trq _{BRK, CAN} are read into the monitoring level of the vehicle control unit. Method for controlling a multiple drive according to claim 2, characterized in that the requested target torque of the hybrid drive and the negative driveline torque trq _{BRK, CAN} are read into the monitoring level of the vehicle control unit. Method for controlling a multiple drive according to claim 2, characterized in that the negative driveline torque trq _{BRK, CAN is} read from the brake control unit and read in the monitoring level of the vehicle control unit. A method for controlling a multi-drive according to claim 1, characterized in that a detected in the brake control unit braking torque trq by the allowable negative torque _{MIN, SUP} is divided between the hybrid drive and the remaining part of the braking torque applied by the vehicle brakes. Method for controlling a multiple drive according to claim 7, characterized in that during braking, the permissible negative torque trq _{MIN, ZUL} by a motor _drag torque ( 16 ) and a negative moment ( 26 ) of the at least one electric drive of the hybrid drive is applied. Method for controlling a multiple drive according to claim 1, characterized in that the permissible negative torque trq _{MIN, ZUL} the limit between a non-critical torque range ( 38 ) and a critical torque range ( 36 ) of a torque range ( 30 ) of a hybrid drive marked. Method for controlling a multiple drive according to claim 1, characterized in that a permissible, negative torque trq _{MIN, ZUL of} the drive train is continuously compared with the negative torque of the at least one electric drive.