WO1995013201A1

WO1995013201A1 - Hybrid drive system for road vehicles

Info

Publication number: WO1995013201A1
Application number: PCT/CH1994/000213
Authority: WO
Inventors: Diego Jaggi
Original assignee: Esoro Ag
Priority date: 1993-11-08
Filing date: 1994-11-07
Publication date: 1995-05-18
Also published as: EP0677001A1; CH692609A5

Abstract

The proposed hybrid drive system for road vehicles is provided with an electric motor (1) which is connected directly to the drive wheels (9) via a fixed reducing gear box (2). An internal combustion engine (3) can be coupled directly to the said reducing gear box (2) via a clutch (4). A system control unit (10) with input elements (6) facilitates various running modes and charging of the battery (15) during the journey. This proposed system is a particularly simple, lightweight and efficient hybrid drive.

Description

Hybrid drive for road vehicles

The invention relates to a hybrid drive for street vehicles with an electric motor and an internal combustion engine connected in parallel. Previously known hybrid drives still have considerable disadvantages. Above all, they are very complex, expensive and relatively heavy and yet have limited performance in everyday use. Series hybrid systems require three machines: an internal combustion engine with a generator to generate electricity and an electric motor as a driving machine, all three of which have to be designed essentially for the nominal power of the drive and thus form an extremely heavy and expensive system. The performance of the electric motor and internal combustion engine cannot be added together. Known parallel hybrid drives, on the other hand, always require at least one complex multi-stage manual transmission or an automatic transmission with a torque converter. The electrical power is usually very limited and often not even sufficient for purely electrical, emission-free driving in agglomerations.

It is an object of the present invention to overcome the disadvantages of the known hybrid systems and to provide a drive which is distinguished by a low system weight, small space requirement, simple construction, low manufacturing and operating costs, high efficiency and good performance in the entire speed range. It should be particularly suitable for lightweight vehicles and enable emission-free, purely electric driving in agglomerations. According to the invention, this object is achieved by a hybrid drive according to claim 1. By direct mechanical connection on the one hand of the electric motor and on the other hand of the internal combustion engine to the common, simple fixed reduction gear and the transmission, the performance of both motors can be done in the simplest way and with the greatest possible efficiency on the drive wheels. The system control enables the optimal use of each engine individually and interconnected, depending on the driving speed and the currently desired drive power. With this hybrid concept according to the invention, with relatively small electric and internal combustion engines and traction batteries, sufficient power can be provided over the entire driving range with a correspondingly low weight and cost. In the medium speed range, the batteries can also be recharged again and again with the internal combustion engine excess power. The range for long journeys upland can thus be given essentially by the internal combustion engine consumption and its tank size. In this hybrid concept, the two engines complement each other optimally by bringing their respective strengths to bear. Both motors are therefore designed to be roughly the same strength, ie there are two main drive motors that are basically equivalent and not a main motor and an auxiliary motor. The electric motor 1 takes over all driving dynamic tasks in the highly dynamic lower speed range (driving and recuperative braking in the urban area). Thus, the possibilities of the electric motor, very good controllability, high efficiency - even in the partial load range - are optimally used. The internal combustion engine is not active in the lower driving speed range, in the urban area. In the medium speed range, the internal combustion engine is also used as uniformly as possible and in an efficient operating range, often in the full load range, for example when driving uphill faster. In the upper speed range (overland roads and on motorways), the combustion engine is mainly used in the full-load range.

The dependent claims relate to advantageous developments of the invention with particularly favorable ratios of the two motors with regard to outputs, Torques and reduction ratios as well as with other combination elements. The invention is explained in more detail below with the aid of examples and figures. 1 shows a hybrid drive according to the invention with

Standstill clutch; Fig. 2 shows a power curve of the electric motor and

Internal combustion engine as a function of speed; Fig. 3 shows a performance curve in a two-stage

Hybrid drive; Fig. 4 shows a torque curve of the electric motor and

Internal combustion engine as a function of speed; Fig. 5 shows an example with different

Reduction ratio of electric motor and

Internal combustion engine; Fig. 6 shows an example with switchable two-stage

Chain transmission; Fig. 7, the interaction of both drives on one

Driving example.

Fig. 1 shows schematically an inventive hybrid drive with an electric motor 1, which is connected to a fixed reduction gear 2. An internal combustion engine 3 can be directly coupled to a shaft of the fixed reduction gear 2 via a clutch 4. The output of the reduction gear leads via a clutch 5, which can be switched on and off at a standstill, to a transmission 7, for example with differential and half shafts, which transmits the drive power from both motors to the drive wheels 9. The entire power and function control is carried out by a system control 10, which also contains an electric motor control 16 and an internal combustion engine control 17. The system controller 10 is connected to the electric motor 1, internal combustion engine 3, clutch 4, battery 15 and to input elements 6, for example to an accelerator pedal 31, a brake pedal 32 and a program selector switch 12. The system controller 10 also serves as a generator for charging the electric motor 1 Travel battery 15 operable. This once as a recuperation brake, controlled via the brake pedal 32, and also when driving, when the internal combustion engine delivers more power in the optimal full-load range than is required for driving, the battery can be recharged with the excess power via the electric motor. Display devices 8 provide information about the state of charge of the battery 15 and about consumption and operating data of both motors 1, 3. The transmission 7 can be separated from the reduction gear 2 with an additional clutch 5 that can be switched at a standstill, for example in the form of a shift pinion. The internal combustion engine can then be started with the electric motor as a starter via a starter button 14, in order then to charge the battery 15 as a stationary generator machine with the internal combustion engine via the electric motor. This as a reserve solution if there is no mains connection for the charger 18 (operating mode SL: standstill charging).

With the program selection switch 12 e.g. The following additional, automatically running driving programs are set:

Electric drive mode E: Purely electric drive with recuperation function as an additional braking system. The internal combustion engine is switched off and disengaged.

Hybrid drive mode H: In the lower speed range, again purely electric driving, if an adjustable urban limit speed of, for example, 60 to 65 km / h is exceeded, the internal combustion engine 3 is automatically engaged and takes over the full driving performance as far as its performance is sufficient. Both motors are controlled by the setpoint generator (accelerator pedal) 31 in such a way that the desired total power PSOLL is achieved overall. If the desired power PSOLL is less than the possible full load power PVM of the internal combustion engine at this speed, the internal combustion engine is operated at partial load. At an adjustable minimum speed VMIN of, for example, 45 to 50 km / h, the combustion engine is automatically disengaged and switched off after a short standby time of, for example, 10 to 20 seconds. When the brake pedal 32 is actuated, the supply of fuel to the internal combustion engine is shut off and the electric motor switches over to generator operation as a recuperation brake. When switching from hybrid mode H to electric mode E, the supply of equipment to the internal combustion engine is always interrupted, disengaged and the latter switched off.

Hybrid drive charging mode HL: Here the combustion engine is not operated at partial load, but if the full load power PVM of the combustion engine is greater than the requested target power PSOLL, the excess power is always used to charge the battery, e.g. explained in Fig. 7.

2 shows an example of a curve of the full load powers P of the electric motor (PE) and the internal combustion engine (PV) as a function of the speed V for a hybrid drive with a fixed reduction stage. The briefly available maximum power or full load power PEM of the electric motor is very high at 20 kW in the lower speed range and only drops somewhat in the upper range. The continuous power PE of 9 kW can be used up to the maximum speed, here 120 km / h, and can be used over the entire speed range, for example for overtaking and on gradients. In the case of the internal combustion engine, the full load power VM also corresponds to the continuous power, which increases from about 60 km / h up to a maximum value of, for example, 11 kW in the area of the maximum speed. Curve R shows the power requirement for level travel, ie the driving resistance. The motors are designed and translated here so that the electric motor alone enables a gradeability of, for example, 20 25% with a full load and that the internal combustion engine delivers its maximum power in the range of the maximum speed, corresponding to the driving resistance R. Out of town, e.g. on mountain routes from approx. 50 km / h, the performance of both Motors added according to curve PE + PVM can be used. When driving flat, the power requirement R at medium speeds is significantly lower than the full load power PVM of the internal combustion engine. The resulting difference DP = PVM - R can then be used as a generator to recharge the battery by operating the electric motor. The area of application EM, VM of the two motors is also shown in the figure: for the electric motor EM from 0 to 80 km / h and, if required, up to a maximum speed of 120 km / h. The area of application of the internal combustion engine VM normally extends from 60 to 120 km / h, if necessary from the minimum speed VMIN of, for example, 50 km / h. The PEM2 and PVM2 curves show a different power rating with a higher internal combustion engine power according to curve PVM2 up to a maximum value of 14 kW, which also enables a higher maximum speed of approx. 130 km / h, corresponding to the higher driving resistance R. According to Curve PEM2 a reduced maximum power of 14 kW, for example. This corresponds to a design in which lower acceleration and climbing performance are required in the lower speed range. Accordingly, the battery size and weight can be reduced, for example, from 200 kg to 120 kg.

These engine designs refer to a lightweight vehicle from e.g. 500 - 600 kg empty weight.

3 shows the power curve for an example with two switchable fixed reduction stages 21, 22. Here stage 21 is designed for a maximum speed of 80 km / h and stage 22 for a maximum speed of 130 km / h. The gear ratio is therefore 1,625. In general, the reduction ratio from first to second stage is between 1.4 and 2, preferably in the range from 1.5 to 1.7. A higher gradeability or acceleration in the lower speed range is achieved by the electric motor and in the medium speed range up to 80 km / h by the internal combustion engine. Likewise, the possible reloading performance DP = PVM - R increased. With such a two-stage version, a greater overlap of the main application areas EM, VM of both motors is achieved and VMIN is reduced.

4 shows the torque curve M as a function of the speed for a fixed reduction stage. The permanent torque ME with relative value 1.0 and the short-term maximum torque MEM with maximum torque 2.0 of the electric motor are very high from standstill and decrease with increasing speed V from approx. 30 km / h in accordance with the performance curve of FIG. 2. Conversely, the full-load torque curve MVM of the internal combustion engine, e.g. increasing from 50 to 120 km / h up to a maximum value of 0.8 here and then falling. The usable added continuous torque MVM + ME of both motors, supplemented by the high maximum torque MEM of the electric motor in the lowest range, results in high values over the entire speed range with reserve for gradients and overtaking. The curves MEM2 and MEM3 show other design examples. For applications, especially in flat areas, the maximum torque can be e.g. Relativ¬ value 1.5 can be chosen smaller according to curve MEM2, while an application that requires high gradeability and acceleration to a maximum value of e.g. 2.5 is designed according to curve MEM3. The curve MVM 0.8 illustrates an example in which a speed reduction between the electric motor and internal combustion engine of e.g. 1: 0.8 is provided, so that at a speed of 120 km / h the electric motor e.g. 10,000 rpm and the internal combustion engine reached 8,000 rpm. Due to the shorter reduction, the maximum torque of the internal combustion engine related to the electric motor axis is increased to 1.0 (as in FIG. 5).

FIG. 5 shows such an example with a spur gear reduction gear 26, where a reduction of, for example, i = 0.8 is present between the electric motor shaft 27 and the common shaft 28. The internal combustion engine 3 is elastic Coupling 29 and connected to the shaft 28 via an electromagnetic coupling 4. Reduction gear 26 with clutch 4 and electric motor 1 form a compact unit.

As a further variant, an additional small, light and inexpensive generator 20 is firmly connected to the motor shaft 28 of the internal combustion engine 3. (This variant is also shown in FIG. 1.) The generator can also be attached on the other side between clutch 4 and engine 3. This combination thus acts as an additional small series hybrid drive. With the clutch 4 open, the internal combustion engine can run independently of the electric motor and drive the generator 20. So it is even at low speeds of e.g. 0 - 50 km / h, where the internal combustion engine is not used for traction, it is possible to generate electricity with the internal combustion engine via the generator for recharging the batteries or directly for feeding the electric motor 1. To illustrate this further possible operating mode, FIG. 2 shows the horizontal PGM with a performance of, for example 4 kW drawn. This corresponds to a fraction of the maximum internal combustion engine power PVM, the power ratio of generator to internal combustion engine PGM / PVM preferably being between 0.2 and 0.5. This means that if necessary, a range can be achieved in the very low speed range, which is only limited by the tank capacity.

FIG. 6 shows an embodiment with two fixed reduction stages 21, 22. This transmission is formed by two permanent chain drives 24, each with two sprockets. The adhesion switching between the two chain stages 21, 22 takes place via an electromagnetic switching clutch 23 on the electric motor shaft 27. The output shaft 30 carries a freewheel 35 of the slower chain drive 21. Instead of the freewheel, an electromagnetic clutch could also be used on the output shaft 30. The sprockets are light and fine graded interchangeable so that the reductions 21, 22 can be optimally designed for the desired main area of application of a vehicle.

FIG. 7 illustrates the optimally combined interaction of the two motors using a driving example, driven out of town in the HL = hybrid charging mode. The curve PVM shows the full load power of the internal combustion engine corresponding to the speed driven as a function of the travel time. PVM is roughly proportional to speed. The curve PSOLL corresponds to the desired power setpoint specified by the accelerator pedal 31. In the first part of the journey to T1, a higher output is required than the internal combustion engine can deliver at this speed: PSOLL> PVM, e.g. on a slope. In a subsequent downhill section up to T2, PSOLL = 0, but the internal combustion engine continues to run and charges the energy F2- into the battery via the electric motor. At T2, a high power PSOLL is required for overtaking and accelerating: area F3 +. From T3 e.g. in mode H only run with the VM as long as PSOLL <PVM. The energies F1 + and F3 + are thus taken from the battery 15, while the energy F2- is fed back (additive and subtractive switching of the two motors). This is monitored by means of a capacity indicator on the battery, so that the desired state of charge of the battery is always maintained (until the next mains charge). An optimized battery management that takes into account the state of charge and the characteristics of the battery can be integrated into the control program 11. If the battery is sufficiently charged, mode H, i.e. without reloading the area F2-. The motor control can also be directly influenced manually, e.g. by switching the combustion engine on and off at T2 or Tl. (selection of an operating mode M = manual)

A major advantage of the inventive hybrid concept is that the internal combustion engine, contrary to the parallel hybrid drives known to date, for starting and in the lower speed range up to VMIN, is not used. The internal combustion engine can thus be optimally designed for its limited area of application. This is possible in a particularly efficient way, for example with a simple, inexpensive and light two-stroke engine. In addition to petrol and diesel engines, other internal combustion engines such as Stirling engines or gas turbines can also be used - since the internal combustion engine only has to follow slowly changing load changes. Overall, the new hybrid concept results in a powerful and efficient, simple, light, compact and, above all, inexpensive drive.

Claims

claims

1. Hybrid drive for road vehicles with an electric motor (1) and a parallel-connected internal combustion engine (3), characterized in that the electric motor (1) via a fixed reduction gear (2), which has at most two switchable reduction stages (21, 22) , can be connected directly to the drive wheels (9), and that the internal combustion engine (3) can be directly coupled to a shaft of the fixed reduction gear (2) via a clutch (4), with a transmission (7) from the output of the reduction gear (2) to the drive wheels (9) and to a system control (10) which is connected to the electric motor (1), to the internal combustion engine (3), to the clutch (4) and to input elements (6), and that the electric motor is controlled by the system control (10) can be operated as a generator for charging a travel battery (15).

2. Drive according to claim 1, characterized in that the ratio of the maximum powers of the electric motor to the internal combustion engine PEM / PVM is between 1 and 1.8.

3. Drive according to claim 1, characterized in that the ratio of the maximum moments of the electric motor to the internal combustion engine MEM / MVM based on a common output shaft is between 1.5 and 3

4. Drive according to claim 1, characterized in that the reduction ratio of internal combustion engine to electric motor based on a common output shaft is between 0.7 and 1.

5. Drive according to claim 1, characterized in that between the transmission (7) and reduction gear (2) a further, switchable at standstill clutch (5) is provided.

6. Drive according to claim 1, characterized in that at least one accelerator pedal (31), a brake pedal (32) and an operating selector switch (12) are provided as input elements (6).

7. Drive according to claim 1, characterized in that the system control (10) is assigned a control program (11) with which various operating modes (E, H, HL) can be set via a selector switch (12).

8. Drive according to claim 7, characterized by a control program with an operating mode E for pure electric drive and an operating mode H for hybrid drive.

9. Drive according to claim 7, characterized by an operating mode HL in which the internal combustion engine delivers both the mileage and an excess power (DP) with which the electric motor is operated as a generator.

10. Drive according to claim 1, characterized by a two-stroke engine as an internal combustion engine. (3) whose fuel supply is controlled by the system controller (10).

11. Drive according to claim 1, characterized by an asynchronous motor as an electric motor (1).

12. Drive according to claim 1, characterized in that the reduction gear (2) has only one fixed reduction stage (21).

13. Drive according to claim 1, characterized in that the reduction gear (2) has two, via the system control (10) switchable fixed reduction stages (21, 22).

14. Drive according to claim 13, characterized in that the reduction ratio of the two stages (21, 22) to each other is between 1.4 and 1.8.

15. Drive according to claim 13, characterized in that the synchronization takes place when switching from one to the other reduction stage (21, 22) by controlling the electric motor via the system controller (10).

16. Drive according to claim 13, characterized in that both stages are constantly engaged and that the power flow can be switched from one stage (21) to the other stage (22) by means of a clutch (23).

17. Drive according to claim 13, characterized in that the switchover can be selected manually or can be carried out automatically under program control.

18. Drive according to claim 1, characterized in that an additional small generator (20) is arranged on the shaft (28) of the internal combustion engine (3).

19. Drive according to claim 18, characterized in that the generator (20) can also be used as a starter for the internal combustion engine.

20. Drive according to claim 18, characterized in that the ratio of the maximum powers of the generator (20) to the internal combustion engine (3) PGM: PVM is between 0.2 and 0.5.