DE4113386A1 - Combined power plant for motor vehicle - has specific fuel consumption, with drive from combustion engine and auxiliary unit, better than with combustion engine alone - Google Patents

Abstract

The combined power plant comprises a combustion engine and an auxiliary drive unit. The design power of the auxiliary drive is selected so that the specific fuel consumption with drive from the combustion engine and auxiliary unit is better than during drive from the combustion engine alone. The design power is defined by the intersection point of the curve of the actual specific fuel consumption of the combustion engine and curve of the permissible fuel consumption. ADVANTAGE - Fuel consumption is reduced, partic. in low speed ranges.

Description

The invention relates to a hybrid drive arrangement tion for motor vehicles with an internal combustion engine, egg ner auxiliary drive device, a device for Ab branches of excess power of the internal combustion engine in a memory assigned to the additional drive device, and with a higher-level control device for the Operation of the internal combustion engine and / or the operating mode the auxiliary drive device.

The invention is based on a prior art as he according to the order in DE-OS 23 09 680, 31 50 611 and 25 58 707 is described. The status of the Technology assumes that an electric motor has a Coupling or fixed to the output and a second drive via an internal combustion engine and a coup plunging which can be switched off. Further should be mentioned DE-OS 33 22 373 and DE-OS 38 42 632. Especially in The last two publications mentioned is considered a The main goal of hybrid drives is to reduce the Fuel consumption z. T. in certain local areas called sameness. DE-OS 38 42 632 is distinguished through a particularly complicated overall structure, because the hybrid drive presented there consists of a Nuclear power machine, an electric machine that both as Motor and generator can run a mechanical  Flywheel storage and a complex overlay ge drives with which the services are summed or divided can be. Especially that in DE-OS 38 42 632 he imagined hybrid concept appears for one drive in one Cars too complicated and therefore too expensive. With everyone else Documents from a much simpler hybrid concept run out (internal combustion engine and auxiliary drive device drive the vehicle via a gearbox), no instruction is given as to the performance of the Auxiliary drive device in relation to the performance of the Internal combustion engine should be so in the DE-OS 30 22 373 mentioned poor efficiency of the internal combustion engine machine is switched off and a purely electric drive is possible.

It is an object of the invention to provide a simple hybrid to design the drive train in which the fuel supply need especially in the low speed range (up to approx. 50 km / h) can be significantly reduced.

This object is achieved in that the design power (P _E ) of the additional drive device is chosen so that the specific fuel consumption for services below the design power (P _E ) device in the operation of the internal combustion engine and additional drive device is cheaper than when driving by the internal combustion engine alone , and that this design performance be determined by the intersection of the curve of the actual specific fuel consumption (b _eMOT ) of the internal combustion engine and the curve of the permissible specific fuel consumption (b _{e zul} ), the latter curve being defined by

are in it

b _{e corner} the minimum specific fuel consumption at the lowest mobile speed of the internal combustion engine,
η ₁ the efficiency for the conversion of the mechanical energy of the internal combustion engine into the storage energy,
η ₂ the efficiency for the conversion of the storage energy into the energy of the auxiliary drive device,
P the power called up,
P _{Eck is} the maximum power of the internal combustion engine at minimum operating speed.

With this solution principle, the auxiliary drive device is tion designed so that the operation of the internal combustion engine in the partial load range with very high specific fuel consumption can be switched off completely.

With all internal combustion engines, diesel or Otto, the area of low specific fuel consumption is close to the full load line. It is to be striven for by a corresponding automatic transmission that the engine always delivers its performance required by the customer with maximum torque and corresponding (low) speed. Reaches the internal combustion engine in this mode of operation, which is made possible by a higher-level control device for an internal combustion engine and a continuously variable transmission, its minimally drivable operating speed, so the customer must now go into part-load operation with even lower performance requirements. In today's vehicles and internal combustion engines, this is necessary for speeds below 70 to 100 km / h. In other words, especially in inner-city areas, the engine runs with a specifically high consumption and with corresponding environmental pollution. This high specific consumption of the internal combustion engine is avoided by the hybrid drive device shown. If the power desired by the customer is lower than the corner power of the motor shown in Fig. 2, there are two options:
1. When the memory is empty, the internal combustion engine continues to deliver its corner power, the excess power compared to the desired mileage is stored in an energy storage ( FIG. 3, case III)).
2. When the memory is full, the internal combustion engine is switched off and the power for the additional drive device is removed from the energy store ( FIG. 3, case VI)).

The invention is explained in more detail below using an example and in particular FIGS. 1 to 4. It shows:

Fig. 1 shows schematically a hybrid drive assembly,

FIG. 2a for explaining examples of a graph showing the running resistance performance over the vehicle speed,

Fig. 2b is a graph showing the engine output to the engine speed,

Fig. 3, a total power distribution diagram in connection with the described examples, and

Fig. 4 is a schematic representation of the specific consumption in a diagram.

The conversion of mechanical energy into storage energy cannot be carried out without losses. The conversion of storage energy back into mechanical energy also takes place with a corresponding degree of efficiency. It only follows from this that it does not make sense to design the additional drive device with the corner power of the internal combustion engine. The fuel consumption for this power is lowest when this power is directly available to the vehicle without further losses due to energy conversions. The performance of the additional drive device results from the b _e map of the internal combustion engine used and the conversion efficiency mechanical energy into storage energy η ₁ or storage into mechanical energy η ₂ . This performance essentially results from the intersection of two curves, which are shown in FIG. 4. One curve corresponds to the fuel consumption in direct operation only by an internal combustion engine (b _eMot ) and the second curve corresponds to the fuel consumption (b _ezul ) of a hybrid-powered vehicle. Consumption results for direct drive by an internal combustion engine

Q _d = _{Pb eMot} · t (G1)

For that equipped with a hybrid powertrain Vehicle consumption results from the corresponding Cycle operation, which consists of 2 parts.

• 1. Internal combustion engine is running, excess power is stored in the energy store ( FIG . 3, case III)).
  • 1. Internal combustion engine ( 1 ) → clutch ( 5 ) closed → → gear ( 3 ) → wheel ( 7 ),
  • 2. Internal combustion engine ( 1 ) → clutch ( 5 ) closed → → generator ( 2 ) → accumulator ( 4 ),
• 2. Storage is charged, internal combustion engine is switched off, vehicle is moved with storage energy ( FIG. 3, case VI)).
  Power flow: memory ( 4 ) → engine ( 2 ) → gearbox ( 3 ) → wheel ( 7 ).

Here fuel consumption arises only in the 1st part.

Q _t = P b · _{ECK eEck} · t₁ (G2)

and the storage energy

W _sp = (P _Eck - P) η₁ · t₁ (G3)

For the 2nd area, the energy from the storage taken, and there is no fuel consumption. Here applies

W _sp · η₂ = P · t₂ (G4)

Furthermore, the total operating time t for the desired performance from the two individual operating times t₁ and t₂ composed.

t = t₁ + t₂ (G5)

(G5) in (G4): W _sp = P / ₂ (t - t₁).

This equation equated with equation (G3) and resolved after t₁ results

If you use this value in equation (2), you can calculate the fuel consumption in cyclical operation, he results in  

The performance of the additional drive device now results from the characteristic diagram of the internal combustion engine when the direct consumption Q _d = Q _t . Equating these two consumptions allows the time t or the power P to be shortened and the equation mentioned in the claim results

Fig. 4 shows the two curves, which correspond to the direct consumption of a motor vehicle and the other side of a motor vehicle with a hybrid drive train.

The customer demands a higher performance than the design performance of the additional drive device, so it is for the Fuel consumption cheaper, this performance directly over to bring the gearbox to the wheels than the detour via to choose the memory. For performances less than that It is the design power of the additional drive device low-cost, cyclical, d. H. the engine with the Operate corner power, the excess power before save temporarily and then be the additional drive direction when the internal combustion engine is at a standstill Operate memory.

This results in:
1. High fuel savings at low speeds in city operations ( Fig. 1, case III + VI).
2. Storage of the thrust energy ( Fig. 1, case VII).

In today's vehicles, the fuel supply is switched off when the accelerator pedal is not depressed (no fuel consumption), but the kinetic energy of the vehicle is converted into thermal energy (friction in the internal combustion engine). With the hybrid drive train presented here, it is possible to improve this operating state by braking the vehicle using the additional drive device ( 2 ), which now works as a generator, and in this case the internal combustion engine ( 1 ) from the vehicle via the clutch ( 5 ). is uncoupled. This gives the customer the same driving experience as with today's vehicles, it slows down slightly when he releases the accelerator pedal completely, so there is no free-wheeling effect.
3. Because the additional drive device ( 2 ) is very much smaller than the internal combustion engine ( 1 ) (for the following numerical example <10% of the maximum output of the internal combustion engine), the moment of inertia of this machine can become very small, especially since it is possible due to the possible intermediate translation ( 6 ) ( Fig. 2) can also be designed very hochdre starting. This not only has structural parts (weight), but also the response behavior of the additional drive device is very fast, that is, the machine can be switched from generator operation to motor operation within a few msec and thus has the possibility in the so-called kickdown case ( Fig. 1, case IV) short-term to add an additional power to the drive train and thereby improve the acceleration. If it is designed as an electric machine, this small additional drive device can simultaneously take on the functions of generator (alternator) and starter ( FIG. 1, case I).

Numerical example

In Fig. 2, the driving resistance of a real vehicle is shown in the left diagram and a section of the b _e map of a turbo-diesel engine is shown in the right diagram.

The fuel consumption of the real vehicle results for the selected first example for v = 40 km / h according to equation ( 1 )

W _d / t = P b _eMot
= 3 kW 390 g / kWh = 1170 g / h

For the same vehicle with hybrid powertrain results fuel consumption according to equation (G6)

With

P _Ecl = 16 kW,
b _corner = 222 g / kWh,
η₁ = η₂ = 0.85

This gives this vehicle as an example selected speed a saving of approx. 27%. For the second example v = 70 km / h results from the equation (G1)

Q _d / t = 7.3 kW 238 g / kWh = 1738 g / h

and for Q _t according to (G6)

and an additional consumption of the hybrid drive of approx. 10%.

Claims (1)

Hybrid drive arrangement for motor vehicles, with an internal combustion engine ( 1 ), an additional drive device ( 2 ), a device for branching excess power ( 6 ) of the internal combustion engine into a memory associated with the additional drive device ( 4 ), and with a higher-level control device for the operation of the combustion Engine and / or the operating mode of the auxiliary drive device, characterized in that the design power (P _E ) of the auxiliary drive device is selected so that the specific fuel consumption for services below the design power (P _E ) is more favorable when operating the internal combustion engine and auxiliary drive device than when driven by the internal combustion engine alone, and that this design power is determined by the intersection of the curve of the actual specific fuel consumption (b _eMot ) of the internal combustion engine and the curve of the permissible specific fuel consumption (b _ezul ), the latter curve being defined by therein sindb _eEck the minimum specific fuel consumption in the klei nesten mobile speed of the internal combustion engine,
η ₁ the efficiency for the conversion of the mechanical energy of the internal combustion engine into the storage energy,
η ₂ the efficiency for the conversion of the storage energy into the energy of the auxiliary drive device,
P the power called up,
P _{Eck is} the maximum power of the internal combustion engine at minimum operating speed.