The present invention relates to the control of the power available on an electric traction chain of a hybrid vehicle.
More precisely, the object thereof is a method for controlling the power available on the electric traction chain of a powertrain consisting of a combustion engine that can transmit the torque thereof to the wheels over various transmission ratios, of a first electric machine of a second electric machine linked alternately to the input shafts of the combustion engine or of the first electric machine in the powertrain, and of a supply battery for the electric machines.
The publication WO 2014/207332 describes a hybrid drive of this type, having several ratios, that are electric, combustion and hybrid, where the torques of the combustion engine and of at least one electric machine are added in the direction of the wheels. The combustion-generated torque is transmitted to the wheels over a “combustion” transmission ratio, and the traction torque of the main electric machine is done so over an “electric” ratio. During changes in the combustion transmission ratio in hybrid mode (combining the combustion and electric tractions), the torque of the combustion engine is interrupted. The torque of the secondary electric machine is then driven to synchronize the combustion engine with the new ratio thereof, while providing torque to the wheel via the main electric machine.
In practice, the electrical architecture of the vehicle, in particular the power available on the main electric machine, limits the input thereof. Retaining a purely electrical traction up to relatively high speeds, for example up to 80 km/h, is limited by the voltage level of the battery. The voltage is often too weak, even at full charge, to develop the entire desired traction electric power. The phenomenon worsens as the charge state decreases. When the powers of the two electric machines can be combined, the performances of the electric traction chain remain insufficient, despite the input of power of the secondary electric machine, which is limited by the voltage level.
Moreover, if there is little compensation for the interruption of the combustion torque during the combustion ratio changes, the driver and passengers of the vehicle feel this shifting like that of a robotized transmission having torque break.
It is therefore desirable to improve the performances of the electric traction chain, particularly on non-rechargeable hybrid vehicles, in order to have a higher power for pure electric driving, and in order to soften the torque break felt during the ratio changes on the combustion traction chain.
The aim of the present invention is to increase the available power, in order to raise the speed accessible for electric driving, and to soften the power gap during the combustion transmission ratio changes.
To this end, it proposes that the supply voltage for the electric machines is established by a DC voltage [ML1] converter, arranged between the terminals of the battery and those of the electric machines, which is able to impose on them a voltage equal to that of the battery, or a voltage that is greater than this.
This measure makes it possible to increase the power available on the electric traction chain, particularly at high speed.
In a particular embodiment of the invention, the voltage converter imposes the voltage of the battery on the electric machines, when the acceleration request of the driver through the accelerator pedal thereof remains weak, and imposes on them a voltage that is greater than this, when the driver requests a strong acceleration.
The DC voltage [ML2] converter, which is arranged between the terminals of the battery and those of the electric machines, can impose, according to required conditions, a voltage equal to that of the battery, or a voltage greater than this.
The present invention makes it possible to simultaneously solve the two technical problems cited, which are encountered, for example, on a motive power hybrid powertrain non-rechargeable on the electric network on the ground, with an on-board voltage of approximately 200 V, and a relatively low capacity, of a few hundred Wh.
The preferred use of this invention is on a powertrain consisting of a combustion engine linked to a first transmission input shaft which can transmit the torque thereof to the wheels over various transmission ratios, of a first electric machine linked to a second input shaft of the transmission, and of a second electric machine linked alternately to the first or to the second input shaft of the transmission.
According to the present invention, it is possible to increase the power available on the electric traction chain, particularly at high speed.
It will be better understood on reading the following description of a particular embodiment thereof, with reference to the appended drawings in which:
The transmission 1 of
The first jaw clutch 8, located on the secondary shaft 7, makes it possible to modify the ratio of the electric machine ME 2, independently of the rest of the transmission, in order to have two electric ratios EV1 and EV2. The second jaw clutch 9, located on the solid primary shaft 4, makes it possible to modify the ratio of the combustion engine 3 independently of the electric ratios, in order to establish two combustion ratios Th2 and Th4, independently of the electric ratio. The third jaw clutch 11, located on the transfer shaft 10, makes it possible to establish a third combustion ratio Th3, when it moves to the right in the diagram. It is possible to independently choose, at each instant, the ratio desired on the first electric machine ME 2 and that desired on the combustion engine unit Mth 3 and the second electric machine HSG 5. The combinations of the combustion ratios and of the electric ratios make it possible to produce hybrid ratios, denoted HEVxy, where x is the ratio of the combustion engine, and y is the ratio of the ME.
The curves of gear shifts of the transmission are grouped together in
In the intended use, it is possible to agree that the target ratio is always (regardless of the speed of movement) an electric ratio ZEV, once this ratio makes it possible to carry out the torque request of the driver. By default, the engaged ratio becomes the longest hybrid ratio, making it possible to carry out the request. Under these circumstances, the requested ratios can be distributed over a graph, like that of
The powertrain suffers from a power gap, during this gear shift. At 125 km/h, the power absorbed by the aerodynamics of the vehicle is approximately 25 kW. The power available for acceleration passes in reality from 80 kW to 10 kW during shifting. Such an acceleration drop (of 87%) gives the driver the impression that the vehicle thereof no longer accelerates, despite the torque provided by the main electric machine ME. The feeling thereof is one of a vehicle supplied with a robotized transmission having torque break.
The solution to these problems is via the control of the power available on the electric traction chain of this motive power powertrain, which mainly consists of the combustion engine Mth, of the two electric machines ME and HSG, and of the supply battery for the electric machines, wherein the main machine ME can transmit the torque thereof to the wheels over various transmission ratios, and the secondary electric machine HSG is alternately linked to the input shafts of the combustion engine or of the main electric machine ME.
As indicated above, the intention is to improve the performances of the electric traction chain of such a powertrain, in particular if it is mounted on a non-rechargeable hybrid vehicle. The aim is to have a higher power during prolonged driving under electric traction, and to soften the torque break felt by the driver and the users of the vehicle, during the gear shifts on the combustion traction chain.
The solution to this double problem is highlighted in
When the request of the driver, through the accelerator pedal thereof remains weak, the main electric machine ME can alone provide the traction of the vehicle, by being powered at the voltage of the battery 12. In this situation, the DC-DC converter 13 imposes, on the electric machines, the voltage of the battery Ubat. The secondary machine HSG does not provide power.
As soon as the driver requests a strong acceleration (cf.
The DC-DC converter 13 can also impose, on the electric machines, the voltage Udc higher than the battery voltage Ubat, during the combustion ratio changes.
The strategy applied during shifting is broken down into several steps. With reference to the case of shifting from the second to the third combustion ratio (Mth2 to Mth3) illustrated by the figures, these steps are as follows:
In summary, there is:
During shifting, the electric power provided by the HSG is transmitted to the main electric machine, which uses it entirely for the traction of the wheels. Without increasing the voltage via the converter, the ME would not have been able to have this energy input, and the acceleration level would have fallen due to the decrease in the combustion power during shifting, before going back up. With the temporary increase in the voltage, the acceleration level remains substantially constant.
The voltage converter can be integrated into the same housing as the ME and HSG inverters, but it can also be integrated into the pack of the traction battery. It is then possible to remove the battery connection relays, since the converter can provide the function of connecting/disconnecting the battery to/from the network. In this configuration, pre-charging the capacitor of the inverters can be carried out by the converter.
In conclusion, the invention results in a transient rise in the voltage of the high-voltage (HV) network during gear shifting. Thanks to the invention, the power provided by the first main electric machine ME, in series hybrid mode, and during the transmission ratio changes of the combustion engine Mth, is increased by operating the second electric machine HSG in regenerative mode. All of the electric power thereof is transmitted to the first main electric machine. It can use it to increase the electric power available for the electric machine in series hybrid mode, or to compensate for the reduction in torque to the wheel, caused by the temporary decoupling of the combustion engine.
Number | Date | Country | Kind |
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1656202 | Jun 2016 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/FR2017/050733 | 3/30/2017 | WO | 00 |