Preheating procedure before starting a combustion engine of a hybrid motor vehicle

Abstract

The invention relates to a preheating method before starting a heat engine (2) of a hybrid powertrain (1) comprising the heat engine (2), a water pump (3), an oil pump (4), a water / oil heat exchanger (5), and a high-voltage water heater (6), wherein, if the water and oil temperatures are below a first predetermined temperature threshold, the method comprises the following steps: Starting the high-voltage water heater (6); Activating the water pump (3) and the oil pump (4); If the heat engine (6) is started, exiting the method. (Fig. 2)

Description

Title of the invention: Method for preheating a thermal engine of a hybrid motor vehicle before starting Technical field of the invention

[0001] The invention relates, in general, to the technical field of managing the temperature of thermal engines. More specifically, the invention relates to a method for preheating a thermal engine within a hybrid motor vehicle before starting. State of the prior art

[0002] During start-ups and temperature increases of a cold thermal engine, an enrichment of injected fuel is carried out in order to obtain good operation of the thermal engine during these particular phases of its life. Such phases of life of the thermal engine result in occasional overconsumption of fuel. This leads to a dilution of the fuel in the oil contained in the thermal engine which is linked to poor combustion efficiency when cold. It should be noted that this phenomenon of dilution of the fuel in the engine oil is more significant when ethanol is used as fuel because its low calorific value results in higher enrichment factors when cold.Indeed, the problems of massive evaporation of ethanol, such as when the temperature of the thermal engine oil does not exceed 78°C, such as repeated starting and stopping of the engine leading to the repeated introduction of ethanol into the oil, leads to strong combustion instabilities and therefore to a high risk of stalling of the thermal engine accompanied by driving discomfort for a user of the motor vehicle: the evaporation of pure ethanol (i.e. close to 100% ethanol) takes place at 76-78°C, leading to a phenomenon of massive evaporation of ethanol in the engine oil.

[0003] These dilution phenomena are much more significant in the context of a hybrid motor vehicle, because the thermal engine, not operating continuously, starts several times from cold during the same journey, unlike a purely thermal motor vehicle whose thermal engine only starts once from cold at the start of the journey.

[0004] There is therefore a need to reduce dilution phenomena during cold starts of a thermal engine of a hybrid motor vehicle, in order to reduce after-sales service costs, the phenomena of stalling of the thermal engine and therefore to reduce the inconvenience of using the hybrid motor vehicle. Presentation of the invention

[0005] The invention aims to remedy all or part of the drawbacks of the state of the art by proposing in particular a solution making it possible to limit the dilution of the fuel in the engine oil of the thermal engine of a hybrid motor vehicle.

[0006] To do this, according to a first aspect of the invention, there is proposed a method for preheating before starting a heat engine of a hybrid powertrain comprising the heat engine, a water pump, an oil pump, a water / oil heat exchanger and a high voltage water heater, where, if the water and oil temperature values ​​are lower than a first predetermined temperature threshold, the method comprises the following steps of: a. Starting the high voltage water heater; b. Activation of the water pump and the oil pump; c. If the heat engine is started, exit the process.

[0007] According to one embodiment, if a traction battery of the hybrid powertrain is charging, the method starts if the charging of said traction battery is complete.

[0008] According to one embodiment, before step c), the method comprises a step bl) of stopping the high-voltage water heater, if the temperature values ​​of the water and the oil are greater than a second predetermined temperature threshold, greater than or equal to the first predetermined temperature threshold.

[0009] According to one embodiment, before step c) and after step b1), the method comprises a step b2) of restarting the high-voltage water heater, if the temperature values ​​of the water and the oil fall below a third predetermined temperature threshold, lower than the first predetermined temperature threshold, then returns to step b1).

[0010] According to one embodiment, the hybrid powertrain operating in ZEV mode, powered by a traction battery, the method starts if a value of a state of charge (SOC) of the traction battery is lower than a threshold of the state of charge (Sa) of the predetermined traction battery.

[0011] According to one embodiment, the threshold of the state of charge (Sa) is a function of a value of a current temperature of the heat engine.

[0012] According to one embodiment, the state of charge threshold (Sa) is greater than a determined threshold (Sh) from which the heat engine is started.

[0013] According to another aspect of the invention, there is provided a hybrid powertrain for a hybrid motor vehicle comprising a heat engine, a water pump and an oil pump, as well as a water / oil heat exchanger, a high-voltage water heater and a computer arranged so as to implement the method having at least one of the preceding technical characteristics.

[0014] According to one embodiment, the oil pump is a piloted oil pump.

[0015] According to yet another aspect of the invention, there is provided a hybrid motor vehicle comprising a hybrid powertrain having one of the preceding technical characteristics. brief description of the figures

[0016] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, which illustrate: • [Fig.l]: a chronograph illustrating an operation of the preheating process before starting a thermal engine according to the invention; • [Fig.2]: a schematic view of a hybrid powertrain in which implements the preheating method before starting a heat engine according to the invention.

[0017] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED description of an embodiment

[0018] With reference to [Fig. 2], a hybrid motor vehicle comprises, in a manner known per se, a hybrid powertrain 1, a traction battery and a fuel tank, in particular a petrol and / or ethanol tank. The hybrid powertrain 1 comprises, for its part, a heat engine 2, one or more electric machines 7 and a gearbox 8 transmitting the various engine torques to the wheels of the hybrid motor vehicle. In addition, the hybrid powertrain comprises an oil pump 4 and a water pump 3.

[0019] We will describe a method for preheating before starting a heat engine according to the invention, the hybrid powertrain 1 comprising a computer arranged to be able to implement said method for preheating before starting a heat engine according to the invention.

[0020] As a preliminary remark, the more fuel is injected into a cold thermal engine, the greater the risk of dilution of the fuel in the engine oil, especially if the thermal engine does not warm up completely with an oil temperature of between 100 and 120°C maximum. Indeed, there is poor vaporization of the cold fuel which must be compensated for by additional enrichments compared to hot fuel to ensure good combustion of the latter, due to poor combustion efficiency when cold. Thus, enrichments dependent on the water temperature impact the starting and restarting of the thermal engine 2 as well as its temperature increases. In operation of a thermal engine, the basic enrichments are dependent on the water temperature, because it is considered that a macerated temperature at x°C of the water equals the temperature of the engine oil.

[0021] For example, when the heat engine has a temperature of 0°C, at its start, an enrichment of the order of 0.478 (this is a multiplication coefficient of a nominal injection time [Ti], i.e. an additional injection time of 0.478xTi is added) this coefficient decreases progressively until reaching a value of 0 at a temperature of 80°C of the heat engine 2.

[0022] In order to ensure proper implementation of the preheating method before starting a heat engine according to the invention which will be described, it is important that, with the heat engine 2 off, the temperature of the oil is indeed equal to the temperature of the water. To this end, the hybrid powertrain comprises a water / oil heat exchanger 5 and the oil pump 4 is controlled (and not mechanical as is conventional for a heat engine). This makes it possible to circulate the engine oil, with the heat engine 2 off, and to ensure heat transfer between the water circuit and the oil circuit. In addition, the hybrid powertrain comprises a high voltage water heater 6 (HVWH for "High Voltage Water Heater" according to English terminology) making it possible to heat the water, with the heat engine 2 off.

[0023] In a first embodiment of the method for preheating a thermal engine before starting according to the invention, the hybrid motor vehicle is stationary and connected to a charging point for the traction battery. In this case, the method for preheating a thermal engine before starting according to the invention is implemented if the charging of the traction battery is complete and if the water temperature and the engine oil temperature are below a first predetermined temperature threshold (for example 40°C).

[0024] Therefore, in a first step, the method of preheating before starting a thermal engine according to the invention starts the HVWH 6 which is then supplied by the charging point directly so as not to discharge the traction battery.

[0025] Then, in a second step, the preheating method before starting a heat engine according to the invention activates the water 3 and oil 4 pumps. Thus, the water which is heated by the HVWH 6 in turn heats the oil via the water / oil heat exchanger 5.

[0026] In a third step, if the temperature values ​​of the water and the oil are greater than a second predetermined temperature threshold, greater than or equal to the first predetermined temperature threshold, the method for preheating before starting a thermal engine according to the invention switches off the HVWH 6, then cuts off the hybrid motor vehicle from the charging point.

[0027] In a fourth step, in a loop, if the temperatures of the water and the oil fall below a third predetermined temperature threshold (lower than the first predetermined temperature threshold), the preheating method before Starting a thermal engine according to the invention repeats the first step if the hybrid motor vehicle is still connected to a charging point.

[0028] In this embodiment, if we take the previous example of pure enrichment at a thermal engine temperature of 0°C at standstill, the water and the oil are heated between 40 and 50°C with the method of preheating before starting a thermal engine according to the invention which has just been described, an enrichment is of the order of 0.05, that is to say much less important than the 0.478 without use of the method of preheating before starting a thermal engine according to the invention. And the enrichment falls to zero for a thermal engine temperature of 80°C reached. The choice to heat to a thermal engine temperature between 40 and 50°C comes from the fact that if the temperature rise is too high, there will be a phenomenon of evaporation of the fuel, ethanol or gasoline in a non-starting thermal engine, in the case where said thermal engine is not sealed and the hybrid motor vehicle is in a confined space such as a garage.

[0029] In a second embodiment of the method for preheating before starting a thermal engine according to the invention, the hybrid motor vehicle operates in so-called “Zero emission” or ZEV mode, that is to say that only the electrical machine(s) 7 operate and the thermal engine 2 is stopped.

[0030] In this embodiment, the method for preheating a heat engine before starting according to the invention is implemented when the state of charge (SOC or "State of Charge" according to English terminology) of the traction battery approaches a determined holding zone, generally by the user of the hybrid motor vehicle, and therefore a start of the heat engine 2. In order to anticipate the start of the heat engine 2 at the start of the determined holding zone, a threshold value of the state of charge of the traction battery is predetermined which is a function of the current temperature of the heat engine 2, threshold value below which the method for preheating a heat engine before starting according to the invention is implemented.A second condition for implementing the preheating method before starting a heat engine according to the invention is: if the water temperature and the engine oil temperature are lower than a first predetermined temperature threshold.

[0031] Therefore, in a first step, the method of preheating before starting a thermal engine according to the invention starts the HVWH 6 which is then powered by the traction battery, while the hybrid motor vehicle is running in ZEV mode.

[0032] Then, in a second step, the preheating method before starting a heat engine according to the invention activates the water pump 3 and oil pump 4. Thus, as for the first embodiment of the preheating method before starting a heat engine according to the invention previously described, the water which is heated by the HVWH 6 in turn heats the oil via the water / oil heat exchanger 5.

[0033] In both embodiments of the method for preheating before starting a heat engine according to the invention, once the heat engine 2 has started, the method for preheating before starting a heat engine according to the invention is put on standby or is stopped.

[0034] An example of implementation of the second embodiment is illustrated in [Fig.l]. In this timing diagram, a user of the hybrid motor vehicle drives in ZEV 10 mode starting from a battery SOC value of 100%. It should be noted that this battery SOC value of 100% is purely illustrative, other starting battery SOC values ​​may be used, less than 100%, which is more often the case in real life conditions of the hybrid motor vehicle. In normal conditions, the battery SOC value decreases throughout the driving until it reaches the threshold value of the state of charge of the predetermined traction battery Sa. Therefore, if the oil and water temperature conditions are met, the method for preheating before starting a heat engine according to the invention in its second embodiment is implemented for a time 12.The value of the state of charge SOC continues to decrease until it reaches a value Sh indicating the start of the determined holding zone 30, determined holding zone 30 during which the thermal engine 2 starts 20 and the hybrid powertrain 1 is in hybrid mode allowing regulation of the value of the state of charge SOC of the traction battery around the value Sh of the state of charge SOC of the traction battery triggering the determined holding zone 30. It should be noted that the value Sa is greater than the value Sh.

[0035] It is clear from the above that the method for preheating a heat engine before starting according to the invention as described in its two non-limiting embodiments makes it possible to heat the oil and the water during the connection phases of the hybrid motor vehicle up to, for example, 50-60°C maximum (heat engine 2 stopped), and / or to heat the oil and the water during driving in ZEV mode when the traction battery has a state of charge SOC approaching the value of the threshold Sh of the state of charge SOC of the traction battery, to anticipate the starting of the heat engine 2, and / or to cyclically maintain a water and oil temperature around a predetermined threshold value (for example 50°C) after charging, during driving in ZEV mode to anticipate a start of the heat engine 2 depending on the wishes of the user of the hybrid motor vehicle and / or the chosen hybrid mode activated.

[0036] Thus the phenomena of dilution of the fuel in the harmful engine oil are reduced as well as the consumption of said fuel and therefore the associated polluting emissions.

[0037] Naturally, the invention is described in the foregoing by way of example. It is understood that the person skilled in the art is able to carry out different variant embodiments of the invention without departing from the scope of the invention.

[0038] It is emphasized that all features, as they emerge for a person skilled in the art from the present description, the drawings and the attached claims, even if concretely they have only been described in relation to other determined features, both individually and in any combinations, may be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

Claims

Claims

1. Method for preheating before starting a heat engine (2) of a hybrid powertrain (1) comprising the heat engine (2), a water pump (3), an oil pump (4), a water / oil heat exchanger (5) and a high-voltage water heater (6), characterized in that, if values ​​of the water and oil temperatures are lower than a first predetermined temperature threshold, the method comprises the following steps of: a. Starting the high-voltage water heater (6); b. Activating the water pump (3) and the oil pump (4); c. If the heat engine (6) is started, exiting the method.

2. Method according to claim 1, characterized in that, if a traction battery of the hybrid powertrain (1) is charging, the method starts if the charging of said traction battery is completed.

3. Method according to one of claims 1 to 2, characterized in that, before step c), the method comprises a step bl) of stopping the high-voltage water heater (6), if the temperature values ​​of the water and the oil are greater than a second predetermined temperature threshold, greater than or equal to the first predetermined temperature threshold.

4. Method according to claim 3, characterized in that, before step c) and after step bl), the method comprises a step b2) of restarting the high-voltage water heater (6), if the temperature values ​​of the water and the oil fall below a third predetermined temperature threshold, lower than the first predetermined temperature threshold, then returns to step bl).

5. Method according to claim 1, characterized in that, the hybrid powertrain (1) operating in ZEV mode, powered by a traction battery, the method starts if a value of a state of charge (SOC) of the traction battery is lower than a threshold of the state of charge (Sa) of the predetermined traction battery.

6. Method according to claim 5, characterized in that the threshold of the state of charge (Sa) is a function of a value of a current temperature of the heat engine (2).

7. Method according to one of claims 5 and 6, characterized in that the threshold of the state of charge (Sa) is greater than a threshold (Sh) determined at from which the heat engine (2) is started.

8. Hybrid powertrain (1) for a hybrid motor vehicle comprising a heat engine (2), a water pump (3) and an oil pump (4), characterized in that it further comprises a water / oil heat exchanger (5), a high-voltage water heater (6) and a computer arranged so as to implement the method according to one of claims 1 to 7.

9. Powertrain according to claim 8, characterized in that the oil pump (4) is a piloted oil pump.

10. Hybrid motor vehicle, characterized in that it comprises a hybrid powertrain (1) according to one of claims 8 to 9.

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