DE29824319U1 - Control for parallel hybrid drive in motor vehicles - Google Patents

Description

Control for parallel hybrid drive in motor vehicles

. This is about hybrid drives with an internal combustion engine (V-engine) and an [electric machine (E-machine), which can not only drive, but also recover braking energy and feed it into a storage device (accumulator, formerly or also mechanical: flywheel)]. The V- and E-engine can drive in parallel, i.e. torque additively. And the E-machine is preferably firmly coupled to the drive shaft of the manual transmission, the V-engine can be separated via the clutch (as usual).

To describe the purpose and advantages of the control system according to the invention, I will first describe the hybrid drive , because the former is based on the latter and, although not new, is not "sufficiently" well known either. The view has often been expressed that the use of electric drives in city traffic is not particularly advantageous because it would only shift emissions from the vehicle to the power plant. But that is completely wrong: for this to happen, combustion engines would have to achieve approximately the efficiency of the system [power plant + electric motor +...] (approx. 1/3). Some manage this at full load, but in city traffic they are a long way from it!

As the following simple calculation shows:

The power requirement for 50 km/h in an average car

(1) is about 3.4kW («4.6PS) - Cs.Bl p.324ff: rolling resistance at 1000kg and a rolling resistance coefficient of 1.5^ : 150N ; air resistance at 2m ² frontal area and c _u =0.4: 93N ] . This results in an energy requirement of about 24MJ for 100km. The petrol consumption for this would be at an efficiency n=l approx. O ₃ 771 (-heating value 31.5MJ/I, see.Bl p. 232) ; at n=l/3 therefore approx. 0.77&KHgr;3=*2,_3| .

In fact, such cars need about 101, i.e. more than

4 times! Which means that their ( _CO2 ) emissions are about this factor higher than with a good electric drive.

The reasons for this are: a) The V-engine efficiency is much higher at partial load

worse than at full load. The smaller the proportion of the nominal torque that is required of the engine, the worse it is. And the above power requirement of only 3.4 kW shows that only a very small part of its potential is needed here. This also means that the engine temperature is too low, so that more combustion residues are produced, which impair the function of the engine (e.g. coking of injection nozzles) and increase wear.

b) In city traffic, a lot of braking is done and ultimately fuel is wasted.

Heating the brakes is wasted. c) Even when idling when the vehicle is stationary

(at traffic lights or in traffic jams) V-engines consume a lot of fuel and emit harmful gases, although no useful energy is generated.

These shortcomings, which make the V-engine seem rather unsuitable for city traffic, are largely avoidable with electric drives (see below). However, the energy storage takes up a lot of weight and space, whereas in petrol, for example, the energy is very concentrated: In order to obtain the approx. 1100 volts (kWh) of mechanical energy that can be obtained with a V-engine from 11 liters of petrol (see above) with an E-engine from a conventional lead battery, the latter must weigh approx. 60 kg! Therefore, it is advisable to use an electric motor in city traffic.

where energy requirements are relatively low (see (I)), to drive with electric propulsion

"""&ngr; . , (6b)

and to use a combustion engine for longer overland journeys.

-> Hybrid drive that offers the following advantages : '

1) Thanks to the E-drive, there are no emissions in the city, where they are higher due to the con —

zentratiqn of people and vehicles are particularly harmful.

2) No standstill losses, yet start-up without delay „

3) Braking energy can be recovered [and thus also potential energy (on gradients)]

And this is considerable." 2.B. in case (1) the kinetic energy at a speed of 50 km/h is sufficient to travel about 400 m at the same speed; in case (31) for 700 m, and at a speed of 70 km/h for 850 m.

4) On short journeys the V-engine does not suffer from not being able to "run on

<10) operating temperature" and the increased cold start consumption is eliminated.

5) When driving with low power requirements (e.g. when enjoying the scenery)

(11) If you want to climb or go downhill for a longer period of time, the above "partial load problems" (3) do not apply.

6) The E-motor is also useful when driving mjt_dem_y-rjqtqr: While with V-engines you always pay for a "power reserve" that is always ready immediately (for overtaking etc.) because of (3) with increased consumption (you have to stay below the consumption-favorable full load range the more power reserve you want), with the parallel hybrid drive you can use the electric motor

&ldquor; , , ~Y(12X

to use this power reserve (if its peak power is not too small compared to that of the V-engine) and thus operate the V-engine mostly in the fuel-efficient range close to full load; through small dimensions (see below) and selection of a high gear. And the small dimensions also reduce the weight and cost of the car and the effort required to meet emissions standards: The "lean-burn engine concept" without a regulated catalytic converter may be sufficient. Especially since the V-engine is much less often used at too low an operating temperature: Because it is not used for short journeys; and because it "comes up to temperature" much quicker, because its heat capacity is smaller and its load per weight is greater and more even.

&bull; <

7) You can save even more : tank size (201 is enough, see (48)), E- .

Starter and alternator, and you "don't need" to use a diesel engine (heavy and expensive), because it has significantly lower consumption than the Otto engine only in the partial power range and this is largely avoided with the hybrid drive (see (12) and (7)).

8) Redundancy : If one of the two engines fails, can you continue driving with the other one? (14)

9) With the E-fiotor you can use the "exhaust energy" of the V-fiotor and

_ ₍₁₅₎

This increases the efficiency of fuel use (see e.g. DE 13600252 Al): As is well known, in conventional turbochargers, the gas is only partially expanded after combustion in the cylinder: namely, only "in the same ratio" as it was previously compressed, _although it is now much hotter and therefore exerts a much higher pressure for the same volume. This pressure can be used to drive an exhaust turbine, which drives a generator, the electricity from which drives the above-mentioned electric motor. In this way, at full load, approximately 10...15% of the power of the turbocharger can be obtained.

Such a drive with two energy sources naturally requires increased effort in terms of control - particularly if it is to achieve the above advantages. Up to now, largely automated systems have been proposed for this, in which, for example, the V-motor is automatically activated depending on the speed or the load distribution on the V and E drive is "optimally" controlled on the basis of characteristic maps. I consider this to be unnecessary and inappropriate effort: the automatic system does not know the driver's parameters that are relevant to control (e.g. how far he wants to drive). And most drivers probably prefer to be in control themselves rather than being surprised by the actions of an automatic system.

In contrast, the control system according to the invention is very simple, both in terms of production and in terms of use, which differs only slightly from the usual: In addition to the usual, the "user interface" contains

not much more than a " V-Hotor switch " (on/off) that controls the electrical

Parts of the V-Hotor (e.g. ignition) are activated, when "Off" the clutch is locked in the "disconnected" state and the function of the accelerator pedal is switched, see below 35

4
The core of the control system according to the invention is the special function of the

Accelerator pedal , which depends on the position of the V-fiotor switch (1?) "At"V-

nqtqr_Ein" the pedal travel is divided into two similarly large areas, of which the first/front only controls the V-motor from idle to full load (where the &Egr; drive is not active), the second/rear only controls the E-motor (so that its torque is approximately proportional to the pedal travel beyond the boundary between the two areas) (where the V-motor remains constantly at full load). In this way the V-motor is always deprived of the largest possible share of the drive torque, which is usually optimal according to (3) (sa(26)). LJm the boundary to the [2nd

In order to make the acceleration in the area with additional E-drive perceptible, ₅ an increased spring stiffness should be provided for the pedal spring, for example by means of an additional pre-tensioned spring. On the other hand, with "V-engine off" the accelerator pedal only controls the E-engine, and this from the beginning of the pedal travel .

The division of the pedal travel (18) results in a problem if the effective characteristics of the pedal travel are the same as in a gasoline engine with simple throttle valve control [in which, at low speeds, the effective control range shrinks to the beginning of the pedal travel and the throttle torque hardly increases in the rear pedal travel range]: This would result in an unsightly "kink" in the effective function C at the boundary between the C2 ranges according to (18)], because in the 2nd range the drive torque increases strongly with the pedal pressure again]. This can be avoided by designing the [transmission of the pedal movement to the engine control] in such a way that over the entire pedal travel

the increase in drive torque per change in pedal travel is approximately the same (near action function) (as is usual with diesel engines).

In addition, the user is provided with a " charging switch "

Provision [which allows the power converter of the electric machine to switch it to generator mode? so that the current from the battery is reversed and charges it] with the positions "zero, charge" and possibly "quick charge". And displays for voltage, current and charge level of the battery. Because charging should not be fully automatic either, because such an automatic system would lack important information= So it is usually cheaper to charge at the socket (see (37)) "depending on the driver's plans: If he approaches a city with an almost empty battery, for example, quick charging with the V-Hotor is indicated" The pedal travel is also divided similarly (18): In the front-

r&n area is only electrically braked, ie the electric motor is like

(21) is switched to generator mode (for "anticipatory moderate braking, e.g. at red lights). In the rear area, the mechanical brakes are also activated (for heavy braking) .

The practical use looks advantageous as follows: After

After getting in, the first thing to do is turn the V-engine off (and disconnect the clutch)

(23) with electric drive. You shift gears as usual, but without the clutch.

If necessary, the V-engine can be started advantageously while driving with the help of the momentum

By upshifting at medium speed (approx. 50 km/h) (so that the transmission drive shaft does not rotate much faster than when the V-motor is idling), putting your foot in front of the clutch pedal and "taking your foot off the accelerator", switching the V-motor switch to "on" and quickly "letting the clutch come in". Then, with the V-motor running, you shift gears as usual using the clutch. And when the V-motor is out of operation, _you switch the V-motor _off by taking your foot off the accelerator, depressing the clutch and switching the V-motor switch to "off". For "electric braking" (22), a gear must be engaged; When the V-engine is running, you should press the clutch down so that the braking can continue until the car comes to a standstill. Should there be many people who attach importance to being able to start the V-engine as usual (which I consider to be superfluous)?

This can also be made possible with a small modification to the engine switch (17): there is an additional middle switch position "Start", which works like " On " (17), except that the accelerator pedal still works as if it were "Off" (19) &igr; So you can use it with the Egr; engine to start the V-engine (at idle) (this, however, places increased demands on the torque of the electric motor , an additional flywheel on its shaft may help).

In order to really achieve the potential advantages (7)ff with the hybrid drive and its control, some special features must be observed and accompanying precautions taken: 1) Since the operation of the V-engine at full load is the rule rather than the exception (Cs. (3) and (18)),

by fuel enrichment at full load "the last horsepower can be mobilized" (which is often done conventionally, also because the exhaust gas behavior at full load is not regulated) ° The fuel enrichment should not exceed the Ha8, where the efficiency is reduced by approx. 2"4 .

2) Speed limitation · To ensure that the V-engine does not run in the

If the engine is "stalled" at idle, a control system should be provided to stabilize the idle speed (which gives more gas when the speed falls below the setpoint). This also makes fuel enrichment at idle and low load (as is often provided for smooth engine running) superfluous. It is also sensible to limit the speed upwards in order to avoid the "throttle range" (where the [fill throttling by the intake] becomes excessive) which is unfavorable for consumption, and to make do with weaker valve springs (-» less friction).

3) The V-engine should be designed in such a way that it can also be used at low

(28)

speed works well with "full throttle" so that the Egr; engine can also be used here (with the accelerator pedal at the rear; see (18) and (12)). For this purpose, a constant pressure carburetor would be suitable as a Vei&mdash; carburetor. And to combat "running smoothness problems" one could increase the flywheel mass of the crankshaft; and/or reduce the maximum filling at low speed, e.g. by reducing the max. throttle valve opening (speed dependent) (see also (42)f).

4) The coupling must be designed for ["permanent separation" without excessive friction and wear]. (29)

5) The rolling resistance (and the friction in the drive train) should be reduced: This is not really important for conventional cars, because such a reduction hardly saves any fuel, because the [deterioration of the V-engine efficiency with decreasing load] (see (3)) counteracts this. But this is not the case here with electric drives; and electric energy is quite expensive (see (37)). And the potential for reduction is considerable: While the rolling resistance coefficient for cars is usually around 1.5°4 or higher (see (1)), trucks and bicycles reach around 0 _5° 4 (see Bl p. 324 and B3 p. 111), i.e. only a third! The power requirement for 50 km/h (see (D)) could be met with this and a weight reduction to 800kg and a

(31) Reduction of the c _u value to 0.3 by about half.

6) The efficiency ti _E of the electric machine should be above 0.9, even at partial load. (Otherwise, the use of braking energy in particular quickly becomes inefficient, because the energy "goes" through the machine several times.) This is achieved, for example, by the brushless electronically commutated direct current machine.

with ironless bell-shaped armature and permanent magnet system, which I proposed in my application DE 37 04 780 A1: In the 3rd example on page 7 of the description dated 28.2.90, the nominal power is 10kW, _{η ε} is 95> and the weight is 2kg (the use of an ironless bell-shaped armature has the advantage, among other things, that only minimal iron losses occur and none at all when idling because no remagnetization takes place). These machines also have the advantage that they are almost wear-free, so they are inexpensive in relation to their long service life and very reliable.

I don't think the often advocated use of machines with "Fejdschiyäching" (for constant rated power over a wide speed range) is particularly advantageous, because the manual transmission is there and most drivers are used to gear shifting and engines with a more or less constant maximum torque. In addition, if the battery is the power bottleneck, the above machine can also deliver higher torque at lower speeds.

7) The electric machine can also be used as a synchronization aid for the manual transmission, by automatically bringing the speed of the drive shaft to the correct value for the desired gear when changing gears. (The automatic system records the speeds of the input and output shafts of the manual transmission.) Advantageous in conjunction with an "up-down shift",

&ldquor; <35)

where the gear lever "only allows two movements", as is usual on motorcycles (and possibly a special lock or movement option for the reverse gear). This means that only two sensors are needed on the gear lever to tell the automatic system above which gear is required. And you can change gear quickly, easily and comfortably and accelerate accordingly.

8) A "battery mulato i&mdash; management " should (in cooperation with the electricity

; &ldquor; (36)

(e-bike inverters) limit the current during charging and discharging depending on the voltage and charge level, and in the case of chemical batteries also on the battery temperature and duration of the current (a short-term high current (approx. 15 s) is hardly harmful, but useful for acceleration). [This does mean that the drive power is reduced after approx. 15sec at "full throttle" but you can quickly get used to it. For example, as a cyclist you have much more power available for a short time (approx. 1000W) than permanently (approx. 200W) (B3 p.313).] The battery life has a great influence on the cost of electricity, because in these cases the battery costs outweigh the cost: Example: A battery with

12V ₅ 45Ah lasts 300 cycles and costs 160DM. Then you can take a total of 12X45#300/1000=162kWh from it, so the battery costs are IDfVkWh! More than the energy costs at a petrol price of 1.5DM/| Cs. (6) -»0.5DM/ kWh] ; and four times as much as that of electricity from the socket [which also shows that with the current taxation of the various energy sources, it is cheaper to charge the battery from the socket than with the V-engine, cf. (21)3 . The battery costs for 100km would therefore be with (1) approx. (1*24/3.6-) 6.7DM . And with reduced resistance according to (31) approx. 3.4DM . -»The electric drive is therefore also economically advantageous at 50 km/h!

9) You should not install an electric heater (except perhaps one for

the windows) Heating with electricity is generally quite wasteful, because about 2/3 of the primary energy is lost when it is generated in conventional thermal power plants. It is particularly expensive with battery power, see (37); especially since heating uses a lot of electricity. And for short journeys, heating is hardly effective anyway (even in conventional cars, where heat from the V-engine is available in abundance, it takes some time for the passenger compartment to warm up) and is hardly necessary (since the occupants are not exposed to the wind, moderate clothing is enough to avoid freezing).

And if you think that you cannot do without heating with an Egr; drive, then you should install a fuel-based one ("auxiliary heating").

10) To schedule the maintenance of the V-dotor, install

a revolution counter (lOOOkm^Sflill. revolutions).

11) In order to be able to attract the attention of pedestrians when driving without a horn, install a quieter signal in addition to the horn.

in volume and sound roughly equivalent to the noise of a V-engine.

The implementation of the control system according to the invention is largely simple using known technology. The simplest way is when the V-engine is controlled with ejector actuators (for example on the throttle valve): then you only need to attach a potentiometer or similar to an angle sensor to the accelerator pedal and the "division of the pedal travel" (18) and the "switching to (19)" can be carried out purely electronically.

(42) can be implemented electronically, e.g. simply using software. And the locking of the clutch (17) can also be implemented electromagnetically, similar to a bistable relay.

This electronic implementation also has the advantage that the "linearization of the transfer function between pedal travel and drive torque"

(20) the speed can also be easily taken into account: By using the map

of the V-riotof torque is determined as a function of the manipulated variable (e.g. throttle position) and the speed , and then during operation the control computer is allowed to set the manipulated variable value which, according to the characteristic map, results in the flow which is in the desired linear relationship to the respective pedal travel.

Even with a mechanical control of the V-engine, (18) and (19) are easy to implement: If it is done via a pull rod, for example, a pre-tensioned spring element can be integrated into it, which is positioned slightly above the

. ""■" C44)

Tensile force, which causes the return force of the motor actuator (eg throttle valve) to be maximal; i.e. when it has reached its maximum stop. So that, as desired, when the pedal is further depressed, the V-riotor remains constantly at full load and the potentiometer for the Egr; motor (is turned further. [This also achieves the increase in spring hardness for the "2nd range"] suggested in (18) .1

And for "V-motor switch to off" (see (17) and (19)) no change to the accelerator pedal mechanism is necessary if you use carburettors such as gas pressure boosters (see also (28)) that do not have an "acceleration pump" activated by the pedal movement (because then, when the V-motor is stationary, a movement of the throttle valve does not cause any damage). The clutch lock (17) can be transferred from the V-motor switch to the pedal using a Bowden cable. And the "transfer" of the E-Motoi control to the front pedal travel range (19) is done as with (42) e.g. using software.

As an alternative to the above solution with the spring element (44), one can also work with a cam mechanism which implements the transfer function between the pedal wheel and the throttle control element state, which bends into the constant function at full load. This would have the advantage that one can also roughly linearize the relationship between the pedal wheel and the V-engine torque at medium speed, cf. (20). And one could implement the cam mechanism, for example, with a cam disk on the accelerator pedal axis.

Finally, the design of an example in which the advantages of the inventive

(47) The following are examples of control systems according to the invention: A 4-person car, weighing about 800 kg, with a 20 kW V-engine (e.g. a 2-cylinder petrol engine with 500 cm ³ ) (sufficient for about 130 km/h with a low-resistance car (31.)), a 10 kW electric machine according to (33) with 20 kW peak power (15 sec) and 8-9 lead batteries with 12 V/45 Ah each (cf. (37)) (connected in series) («100 kg, 1500 DfI). (For battery voltage, deep cycle starter batteries are probably advantageous, because on the one hand a high peak current is important (approx. 200A when accelerating), and on the other hand a large amount of current can be drawn over the course of the service life (cf. (37)). For the on-board network (e.g. 12V), the battery voltage is advantageously reduced using a switching converter, see B2 Chapter 18.6.

The fuel consumption is calculated with reduced resistance according to (31), a payload of 100kg and an efficiency of the V-Hotor of 1/3

(48) at speeds of 50/90/120 km/h it is 1.3/2.7/4.5 1/100 km; at "50" electric drive is assumed and converted to petrol consumption with the assumption that the electricity was "generated from petrol" with an efficiency of 1/3 (6). And for a city cycle, where one stop is made per km (with braking energy recovery), it is about 0.251 higher, since the efficiencies of the electric motor and battery are each 0.9.

The " acceleration from 0 to 50" with electric drive is 6.3sec,

(49) from 0 to 100 with electric and V-engine drive in 12.6sec.

Key to symbols &ugr;. ä. s

Bold are keywords that indicate what the respective section is about and definitions; words in italics

Important statements and formulas are marked for reference with 5 numbers in parentheses on the right margin , in the text between the lines below the one in which the statement begins

Square brackets C. . ] indicate things that belong together or are inserted (ie, the one behind it is linked to the one before it); round brackets indicate insertions of lesser importance / additions 10 To visualize the structure and conceptual structure , spaces and blank lines are also used

Books : Bl° Bosch, Automotive Engineering Handbook, Düsseldorf 1991 B2s U.Tietze, Ch. Schenk: Semiconductor Circuit Technology, Berlin 1983 15 B3.° FRWhitt, DGWilson» Bicycling Science, HIT, Cambridge 1974

Claims (7)

1. Control of the [drive of a motor vehicle with a combustion engine (V-engine) and an electric machine (E-machine) arranged in functional parallel], characterized in that the pedal travel of the accelerator pedal is divided into two similarly large areas, of which the "first/front" only controls the V-engine from idle to full load (whereby the E-machine runs without driving) and the "second/rear" area only controls the E-motor (whereby the V-engine remains constantly at full load). 2) Control system for drive according to the preamble of claim 1, in which the V-engine can be functionally separated from the electric motor with a clutch, so that one can also drive with pure electric drive (with the V-engine stopped), characterized in that the user has a V-engine switch with the positions "on" and "off" at his disposal and that with "V-engine off" [the function of the accelerator pedal is switched so that the electric motor is controlled from the beginning of the pedal travel] and the clutch is locked in the separated state. 3. Control according to claim 1 or 2, characterized in that the effective function of the pedal travel is approximately linear, i.e. that the increase in the drive torque per change in pedal travel is approximately the same over the entire pedal travel. 4. Control according to claim 1 or 2, characterized in that the boundary to the second region of the pedal travel is made perceptible by an increased spring hardness of the pedal spring. 5. Control according to claim 1) or 2) or 3), characterized in that it is largely implemented electrically with an angle sensor (e.g. potentiometer) on the accelerator pedal and an electrical actuator on the V-engine (e.g. electrically driven throttle valve), so that the effective function of the pedal travel according to claim 1 and the "switching" according to claim 2 and the linearization according to claim 3 can be implemented purely electronically, e.g. by software. 6. Control according to claim 1 or 2, characterized in that it is implemented largely mechanically with respect to the V-engine with a pull rod between the accelerator pedal and the V-engine actuator, into which a pre-stressed spring element is integrated, which yields slightly above the tensile force which causes the maximum restoring force of the engine actuator. 7. Control according to claim 1) or 2) or 3), characterized in that it is implemented largely mechanically with respect to the V-engine with a cam gear between the accelerator pedal and the V-engine actuator, [e.g. with a cam disk on the accelerator pedal axis,] which implements the transfer function between pedal travel and engine actuator state, which bends into the constant function at full load (see claim 1)) and advantageously also linearizes the transfer function between pedal travel and V-engine torque for an average speed (see claim 3)).