DE4324010A1 - Method for controlling the torque output of a hybrid drive driving a vehicle - Google Patents

Abstract

A method for controlling the torque output of a hybrid drive, comprising an internal combustion engine and an electric motor, driving a vehicle is described, in which the vehicle is driven either by the internal combustion engine or by the electric motor or by the internal combustion engine and the electric motor together. In order to improve the ride comfort, it is proposed, in those operating ranges in which the electric motor is involved in driving the vehicle, to control the hybrid drive essentially according to the characteristic of an internal combustion engine.

Description

The invention relates to a method for controlling the torque delivery of one from an internal combustion engine and an electrical system motor existing, a vehicle driving hybrid drive ge according to the preamble of claim 1.

From DE-PS 29 43 554 is a combustion engine and elec existing hybrid drive known, which is a vehicle depending on requirements either via the internal combustion engine or via the Drives electric motor or via both motors together.

The invention has for its object a method of im To indicate the preamble of the main claim described type, with which an improvement in driving comfort and a min change in fuel consumption is achievable.

The object is achieved by the features of the kenn drawing part of the main claim solved.

With the inventive method it is achieved that especially if the vehicle is only on the elec tromotor is driven, but also when the electric motor is only involved in the drive, the driving behavior compared to conventional drive with only one combustion engine not noticeably changed for the driver. This applies in particular special for the pushing operation of the vehicle, that is in the loading rich, in which happened with little or no load will. Here the electric motor takes a conventional ge controlled almost no braking torque, too  not at high speeds, which is due to more frequent and greater application of the service brake can be compensated got to. By contrast, with the method according to the invention, we always generates a braking and drive torque curve, as it is characteristic of a vehicle that is made of is ultimately driven by an internal combustion engine. So the driver must e.g. B. on a downhill run when pressing the Be drive brake does not distinguish whether the vehicle is currently off finally via the internal combustion engine or the electromo Tor or driven by both motors together. In all In cases he senses an increasing speed Braking torque. The driver must therefore change the Be drive type not used to a completely different drive behavior nen, but only the different performance of the Mo take gates into account. The lowest is an exception to this Speed range in which the electric motor reaches its maximum Mo ment generates what a good acceleration of the vehicle is actually desirable, even if the electromo gate is only involved in the drive. Also in electrical operation in Standstill of the vehicle, the electric motor not as the Ver internal combustion engine, operated at an idle speed where who saves energy and indirectly also fuel that can.

The embodiment according to claim 3 has the advantage that without that the driver notices something that supplies the electric motor energy storage during normal driving can be ensured with the training according to claim 4 is that in the event that the energy storage - z. B. after a long journey only in electrical mode - heavily discharged is that it can be recharged as quickly as possible, then however, if the energy storage device is only slightly discharged, reloading is carried out with the best possible efficiency can. However, with the configuration according to claim 5, if this should be necessary for the acceleration case, the drive torque of both motors of the hybrid drive Available.  

With the configuration according to claim 6, when the length the remaining distance until an external, stationary Ren energy source is approximately known, the vehicle in the predominant measure driven by the electric motor, so that the Nachla Energy storage via the stationary energy source can follow. In addition, the intervals at which the vehicle's fuel tank must be refilled, ver be enlarged.

In the drawing, the inventive method is based on a Embodiment explained in more detail.

In detail shows

Fig. 1 shows an embodiment of an apparatus for imple out the method according to the invention in a schematic representation,

Fig. 2, the operation of the designated in Fig. 1 with 14 electronic control unit,

Fig. 3a shows a map M = f (α) in the event that the vehicle is driven by both motors,

FIG. 3b is a map M = f (α) in the event that the vehicle is driven out finally by the electric motor,

FIG. 3c is a map M = f (α) in the event that the vehicle in the special mode 1 (SM1) is operated and

Fig. 3d shows a map M = f (α) in the event that the vehicle is operated in special mode 2 (SM2).

Fig. 1 shows a schematic diagram of a hybrid drive for a motor vehicle, which consists of a diesel engine 1, the crankshaft 3 (asynchronous) is coupled via an electrically switchable clutch 2 to the input shaft of an electric motor. The output shaft 6 of the electric motor 3 acts on the selectively lockable torque converter 4 of an automatic transmission 5 , the output shaft 7 in turn acts on the drive wheels 8 of the vehicle via a transfer case not explicitly shown in the drawing. The diesel engine 1 is supplied with fuel via a conventional fuel injection pump 9 . The fuel injection quantity is determined here according to the position of the control rod, which is likewise not visible in the drawing, the position of which in turn depends on the current speed n of the diesel engine 1 and on the current deflection of the adjusting lever 10 . The drive of the electric motor 3 takes place via an electrical energy store 11 and an interposed electronic converter 70 , which, depending on the control, either converts direct current into alternating current in the event of removal of electrical energy from the electrical energy store 11 (arrows 40 ) or in the case of feeding electrical energy Energy in the electrical energy storage (arrows 41 ) converts alternating current into direct current. The adjusting lever 10 of the injection pump 9 is actuated by an electrically operated servomotor 12 , which is controlled by an electronic control unit 14 via the control line 13 . Via the electronic Steuerein unit 14 , the clutch 2 between the selmotor 1 and electric motor 3 via the control line 15 and the converter 70 are also controlled via the control line 18 . The control unit 14 are also via the measured value line 71 a signal corresponding to the current state of charge of the electrical energy store 11 (determined via battery controller 72 (charge balance calculation)), via the sensor 19 and the measured value line 20 a current speed n _E output shaft 6 of the electric motor 3rd Which, when the clutch 2 is closed, is the same as the cure belwell speed n of the diesel engine 1 , corresponding signal and, via the sensor 21 and the measurement line 22, a signal corresponding to the current load specification by the driver (deflection α of the Fahrpe dals 23 ). Via line 24 , the electronic control unit 14 is supplied with the switch position of a manually operable switch S1, via which the driver can select whether the vehicle is driven solely by the electric motor 3 (switch position E) or whether hybrid operation or a drive via the Diesel engine 1 should finally be allowed (switch position H / V). Via the switch S2, the driver can choose between the three modes N, SM1 or SM2 in which the vehicle is to be driven in the event that the switch S1 is in its H / V position. The signal of the switch S2 is transmitted to the electronic control unit 14 via the line 25 . For the special mode SM2, a switching device S3 to be actuated by the driver is provided, by means of which he can enter a remaining travel distance RF to be expected, which is also transmitted to the electronic control unit 14 as a corresponding electrical signal via the line 26 . The operation of the vehicle in special mode SM2 will be explained in more detail later.

In FIG. 2, the operation of the electronic control unit 14 is explained in more detail. After switching on the ignition, the current values for the load specification (accelerator pedal deflection α) and the speed n _{E of} the electric motor (rotor speed) are read in via input block 27 . About the following block 28 , the position of the switch S1 to be operated by the driver is queried. If this is on H / V (H stands for Hybrid and V for Ver internal combustion engine), it is specified that the vehicle can be driven by internal combustion engine 1 and electric motor 3 as well as by the internal combustion engine 1 alone. So that in this case the internal combustion engine 1 can always be involved in the drive, block 29 outputs a signal by which the clutch 2 is closed, ie the torque of the diesel engine 1 is on the drive train of the vehicle and thus on transfer the drive wheels 8 . In the following branching block 30 , the position of the switch S2 to be actuated by the driver is queried. If this is in position N (normal), the hybrid drive is to be controlled in accordance with map A, which is shown in FIG. 3a and is explained in more detail below.

Map A (S1 = H / V and S2 = N)

This map A shows the qualitative relationship between the momentary load specification by the driver (accelerator pedal deflection α) and the torque M acting on the output shaft 6 of the electric motor 3 and thus indirectly on the drive wheels 8 at different speeds n _E. Here, a torque driving the vehicle (drive torque M +) is plotted in the positive part of the ordinate and a torque braking the vehicle (braking torque M-) in the negative region of the ordinate. Up to a limit value α _g , the vehicle is driven exclusively by the internal combustion engine 1 . The clutch 2 is therefore closed here, so that the torque of the internal combustion engine 1 is passed on to the drive wheels 8 . The electric motor 3 , ie its rotor rotates freely in this case. Diagram A shows that the curves of higher speeds are shifted towards smaller moments. In other words, this means that in areas with low load specifications, the braking torque acting on the drive wheels 8 from the diesel engine 1 is greater, the greater the speed n of the diesel engine 1 is. Likewise, it is also characteristic of an internal combustion engine 1 that, in areas of high load specification (large accelerator pedal deflections α), the torque given decreases again in the direction of higher engine speeds. The characteristic curve (n = 1000 1 / min) represents the idling range and constitutes an exception to the characteristics described above, in that in the event that there is no or only a minimal accelerator pedal deflection, engine standstill can only be prevented by that the motor delivers a minimum drive torque to overcome the internal friction. However, the torque given off to the drive wheels 8 is negligible. Likewise, an internal combustion engine reaches its maximum torque only in a medium speed range, so that the characteristic curve 30 extends far below the characteristic lines 31 and 32 at medium and high speeds even in areas of high load specifications. The control now provides for the vehicle to be driven exclusively via the internal combustion engine 1 below the limit value α _g . In the medium and high speed range, the torque acting on the drive wheels runs up to this limit value in accordance with the characteristic curves 31 or 32 or, depending on the speed, in accordance with a characteristic curve which lies between these two characteristic curves 31 and 32 . Above this limit value α _g , the drive torque on the drive wheels 8 would run according to the dotted continuation of the two characteristic curves 31 and 32 if the drive was driven exclusively by the internal combustion engine 1 . In order to have an increased torque available for acceleration, it is provided to switch on the electric motor 3 above the limit value α _g for the load specification, in such a way that the additional torque provided by the electric motor 3 starting from 0% at the limit value α _g up to 100% with maximum load specification α _max of the maximum torque that can be output by the electric motor 3 at the current speed increases linearly. This auxiliary torque is intended to compensate for the loss of acceleration due to the relatively high weight of the electrical energy store 11 and the electric motor 3 . At the drive according to map A is also useful if the vehicle z. B. is moved outside of metropolitan areas, so where the selmotor 1 experiences no or only ge ringing load changes over longer distances. Here, the internal combustion engine 1 can be operated in the area of its best efficiency. The electric motor 3 is then responsible for short-term maximum load requirements. B. provides for overtaking, with the linear increase in the additional electric motor torque with increasing load is achieved that the entire hybrid drive behaves in this area essentially like an internal combustion engine with more power. However, the diesel engine 1 always remains in the range of its maximum efficiency even in these load ranges.

However, if the vehicle is moved to areas in which changes in the load specification (frequent transient operation) can often be expected, e.g. B. in urban areas, the driver can switch to pure electrical operation E via switch S1. If this is the case (branching block 28 in Fig. 2), the output block 33 disengages the separating clutch 2 , and the diesel engine 1 is switched off. In this case, the electric motor 3 is controlled in accordance with the map B shown in FIG. 3b and described in more detail below (the actuation of the electric motor 3 takes place via the output block 34 ). The energy supply takes place via the electrical energy store 11 (see arrow 40 , FIG. 1).

Map B (S1 = E

As with map A, diagram B also shows the relationship between the current load specification (accelerator pedal deflection α) and the torque M acting on the drive wheels 8 at different speeds n _E , the torque M + (driving the vehicle) in the positive region of the ordinate. Drive torque) and negative range that the vehicle braking torque M- (braking torque) is plotted. It can be seen that the characteristics of the characteristic curves 35 to 37 from the middle (from approx. 2500 1 / min) up to the high speed range essentially correspond to those of the diesel engine 1 (see FIG. 3a). This applies in particular to the area of the braking torque. As with the diesel engine 1 , the braking torque (M-) increases with the speed n _E in the areas of low load specifications. A braking torque via the electric motor 3 is generated by switching the electric motor 3 to generator operation, the torque absorption being set by the electric motor 3 running in the generator area by correspondingly controlling the converter 70 . An exception to the characteristic curve characteristic for an internal combustion engine 1 is the range of low engine speeds n _E , in particular when the vehicle is at a standstill (n _E = 0 1 / min). In these areas, it is characteristic of an internal combustion engine 1 that the torque output is comparatively low, for which in a conventional drive via only an internal combustion engine, also a starting clutch or possibly a torque converter is unavoidable. In contrast to this, however, the electric motor 3 can deliver its greatest torque even at the lowest speeds. This is precisely what is desired for rapid acceleration of the vehicle from standstill; this is also because the nominal power of the electric motor 3 can be much smaller than that of the internal combustion engine and thus, at least during the starting acceleration, a similar driving impression (as well as climbing power) arises.

After corresponding control of the electric motor 3 via the output block 34 ( FIG. 2), the control branches to point 38 for re-entering the current values for α and n _E.

In the H / V (hybrid / combustion engine) operating mode, the driver can choose between two special operating modes SM1 (special mode 1 ) and SM2 (special mode 2 ) in addition to the normal operating mode N described above. This is done by setting switch S2 accordingly (see FIG. 1). If the request in block 39 ( FIG. 2) shows that the switch S2 is in the position SM1, the hybrid drive is actuated in accordance with the map C shown in FIG. 3c and described in more detail below.

Map C (S1 = H / V and S2 = SM1)

The relationship between the output from the electric motor torque and the load requirement (accelerator pedal position (α) is in the diagram of Fig. 3c shown nate in the positive range of the Ordi. Is the drive torque M + which will be abge by the electric motor 3, is applied. In this area, energy is thus taken from the electrical energy store 11 (arrows 40 , FIG. 1) and converted into drive energy by the electric motor 3. In the negative range, that moment M- is plotted which is recorded by the asynchronous machine when it is activated accordingly Converter 70 is operated in the generator area. In generator operation, the braking energy is fed back into the electrical energy store 11 (see arrows 41 , Fig. 1). The torque is shown here as a relative value, that is, the current absolute value of the torque in relation to the maximum possible torque at the respective accelerator pedal position α positive (drive range) as well as for the negative range (braking range). The control of the hybrid drive now provides for operating the electric motor 3 in the generator area up to a predetermined limit value α _g for the load specification and only above this limit α _g is the electric motor 3 used to deliver an additional drive torque for z. B. an improved acceleration of the vehicle, as is also the case during operation in normal mode N (see FIG. 3a). Here, too, the drive torque of the electric motor that is generated in addition to the torque of the diesel motor increases linearly, starting from 0% at the limit α _g to 100% of the maximum possible torque at the maximum load specification α _max . The size of the braking torque absorbed by the electric motor running in Ge generator operation, however, depends on the respective state of charge of the electrical energy store 11 . When the energy store 11 is maximally discharged, the maximum possible torque is recorded by the generator 3 (characteristic curve 42 ). However, if the energy storage 11 is only slightly discharged, then the electric motor 3 running in the generator area is driven such that it only absorbs a correspondingly reduced braking torque (characteristic curve 43 ). The position of the characteristic curve in the area below thus depends on how strongly the electrical energy store 11 is discharged. The ratio x _i / x _max corresponds to the discharge factor λ _{i of} the electrical energy store 11 . As the discharge factor λ _i increases, the torque that is branched off for the electric motor 3 running in the generator area increases. Of course, the controller in this special mode SM2 only allows the energy store 11 to be discharged up to a certain minimum limit. An impairment of the life of the energy store 11 by constant deep discharges and recharges with a high charging current is therefore not against.

Since, as described above, in this special mode SM1 up to a predetermined limit value α _g for the load specification of the electric motor 3 is driven in the generator area and accordingly suddenly the entire torque of the diesel engine 1 does not arrive at the drive wheels, the invention sees Ver drive up to the limit value α _{g to} compensate for this torque received by the electric motor 3 by an additional torque output by the diesel engine 1 . A signal for increasing the fuel injection quantity is thus supplied to the electric servomotor 12 arranged on the injection pump 9 by the electronic control unit 14, as a result of which the diesel engine 1 can deliver a higher torque. The additional fuel quantity is dimensioned in such a way that exactly the torque absorbed by the electric motor 3 running in the generator area is compensated for. The driver does not notice in the acceleration and braking of the vehicle what torque is currently being picked up by the electric motor 3 operated in the generator area. For him, the vehicle behaves exactly as if the vehicle were driven exclusively by a conventional internal combustion engine, even if the load specification was changed. This also applies to the range above the limit value α _g , in which, as in operating mode N (map A, FIG. 3a), an additional torque is added by the electric motor 3 to the torque of the diesel engine 1 , specifically with increasing load specification linearly increasing starting from 0% at α _g to 100% of the maximum torque to be produced by the electric motor 3 at the current speed at maximum load specification α _max .

If the request in block 39 ( FIG. 2) shows that the driver wants the special mode SM2, the control branches to the input block 44 . In this special mode SM2, the controller provides for the torque component provided by the electric motor 3 to be kept to a maximum in hybrid operation in order to achieve a maximum discharge of the electrical energy store 11 (of course only up to the minimum limit which is harmless for the energy store 11 ). This mode of operation is selected by the driver when he approximately knows how long the remaining travel distance RF is until a stationary energy source is reached for charging the energy store 11 . It is therefore intended that entered by the driver via the slide switch S3 rest via the input block 44 route RF read. Depending on this remaining travel distance RF, the hybrid drive or the electric motor is then driven in accordance with the map D shown in FIG. 3d. The load of the internal combustion engine 1 is controlled by the servo motor 12 so that the driver is familiar with the driving experience.

Map D (S1 = H / V, S2 = SM2, S3 = RF)

In this map too, the ordinate shows the torque M + output by the electromotor 3 in%, based on the torque 3 that can be given by the electric motor 3 at the respective load specification α. It can be seen that with increasing residual travel distance RF the torque level, which is contributed by the electromotor 3 for driving the vehicle, is always low.

In other words, this means that the amount he brought from the electric motor 3 in the vehicle driving total torque (total torque = torque of the diesel engine 1 + torque of the electric motor 3 ) is dimensioned at every accelerator pedal position and at every speed so that after driving the previously by the driver entered remaining driving distance RF of the electrical energy store 11 to the predetermined minimum (lowest limit) is discharged. The latter can then be recharged at the stationary energy source (connection to the power grid) after the remaining travel distance RF. The need for fuel for the selmotor 1 can thus be reduced to a minimum while traveling this remaining driving distance RF, and just so much that the diesel engine 1 can maintain a minimum operating temperature, which with regard to the effectiveness of a catalytic converter optionally arranged in the gas train or / and is sufficiently high with regard to heating the passenger compartment.

Finally, depending on the characteristic A, C or D, the servomotor 12 of the injection pump 9 and the electric motor 3 are controlled in a corresponding manner via the output block 45 ( FIG. 2). Following this, the control branches back to point 38 for new input of the current load specification α and speed n _E.

The invention is not limited to one as in the embodiment Example provided, hybrid drive of parallel design (Internal combustion engine acts directly on the drive axle). It is also conceivable, a hybrid drive of serial design (Internal combustion engine does not work - as with the parallel hybrid drive - directly on the drive axle, but drives a separate Ge nerator, which in turn the electric motor with electric Energy supplied as well as an electrical energy storage feeds) to control according to the invention. Likewise, the Mixed form of these two hybrid drive types, in which the Combustion engine either directly on the drive axis of the vehicle acts (parallel) or decoupled from the Drive axis to a generator for driving the electric motor drives (serial), according to the inventive method be recognized.

In a further embodiment of the invention, the braking torque of the internal combustion engine can be supplemented or replaced by a braking torque of the electric motor when the vehicle is pushing ( FIG. 3a); the latter would mean that the clutch between the internal combustion engine and the electric motor would be opened in push mode.

In a further embodiment of the invention, the electronic control unit ensures that the electrical energy store is not emptied in the case of permanent full gas according to FIG. 3a by the additional electrical torque being smoothly withdrawn after approximately 15 seconds (ramp 10 seconds). However, in order to be able to call up the full additional electrical torque even after 25 seconds with the accelerator pedal depressed on the mountain, a kick-down switch can be provided on the accelerator pedal, which also switches on the electric motor at full throttle.

It can also be provided that the electronic control unit for frequent acceleration aids by the electric motor ensures that the required charge in unaccelerated driving operation back in the electrical energy storage is fed to the existing or a predetermined charging stood by.

It is also conceivable for 90% of the capacity with a recharge not exceed the electrical energy storage, except with brake recuperation, because the charge is above 90% charge degree of efficiency due to the increased internal resistance of the electrical Energy storage drops.

Claims (7)

1. A method for controlling the torque output of a hybrid drive consisting of an internal combustion engine and an electric motor, driving a vehicle, in which method the vehicle is driven either via the internal combustion engine or via the electric motor or via the internal combustion engine and the electric motor, characterized in that that in those operating areas in which the electric motor ( 3 ) is involved in driving the vehicle, the hybrid drive is essentially controlled according to the characteristics of an internal combustion engine. 2. The method according to claim 1, characterized in that in the exclusively electromotive operation of the electromotor ( 3 ) is essentially controlled according to the characteristics of an internal combustion engine. 3. The method according to claim 1, characterized in that in hybrid operation up to a predetermined limit for the load specification of the electric motor ( 3 ) according to a pre-given characteristic ( 42 , 43 ) is operated in the generator area, the torque required for this by correspond appropriate increase in the torque of the internal combustion engine ( 1 ) is provided. 4. The method according to claim 3, characterized in that the amount of the branched for the running in the generator Elek tromotor ( 3 ) torque is dependent on the state of charge of the electric motor ( 3 ) supplying electrical energy storage ( 11 ) such that with increasing discharge factor (λ _i ) the branched torque increases. 5. The method according to any one of claims 1, 3 or 4, characterized in that in hybrid operation above a predetermined limit for the load specification by the electric motor ( 3 ) an additional drive torque is provided, which increases substantially linearly with the load specification . 6. The method according to claim 1, characterized in that the portion provided by the electric motor ( 3 ) is dimensioned in the sum torque corresponding to the respective load specification such that after covering a predeterminable remaining travel distance (RF) the electric motor ( 3 ) supplying electrical energy storage ( 11 ) is discharged to a predetermined minimum (minimum limit). 7. The method according to any one of claims 1 to 6, characterized, that in braking operation of the vehicle, the braking torque of the Ver internal combustion engine supplemented by a braking torque of the electric motor or is replaced.