FR2951785A1 - METHOD FOR CONTROLLING THE AUTOMATIC STOP OF AN INTERNAL COMBUSTION ENGINE OF A MOTOR VEHICLE - Google Patents

Abstract

The invention relates to a method for controlling the automatic shutdown of a motor vehicle internal combustion engine when stopping conditions are met during a period of time greater than a delay time (Tempo), said combustion engine internal being equipped with a starter adapted to perform a plurality of startup cycles. According to the invention, the delay time is determined as a function of the number of start cycles (N) performed by the starter.

Description

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention generally relates to automatic stop and start systems for internal combustion engines of motor vehicles.

It relates more particularly to a method for controlling the automatic shutdown of an internal combustion engine of a motor vehicle when stopping conditions are met during a period of time greater than a delay time, said internal combustion engine being equipped a starter adapted to perform a plurality of startup cycles.

TECHNOLOGICAL BACKGROUND In order to reduce the fuel consumption of an engine, there are known automatic engine shutdown systems which make it possible, when an internal combustion engine is not used, to cut off the fuel supply of the engine. this engine.

Thus, during the phases of slowing down and / or stopping the vehicle, the engine stops, which reduces the volume of polluting emissions released by the engine, especially when the vehicle is stopped at a red light. Different systems, commonly referred to as Stop & Start, have already been proposed.

Document EP 1 028 022 in particular discloses a Stop & Start system which makes the automatic engine stop depending on different engine control parameters, such as the speed of the vehicle and the rate of depression of the brake pedal. In this document, the engine stop is automatically controlled when the brake pedal remains depressed for a predetermined period of time, provided of course that the vehicle is stopped. Injection pumps and reinforced starters of internal combustion engines are typically designed to perform approximately 350,000 engine start cycles, which is the number of starts that a delivery vehicle without a Stop & Start system performs in the course of time. his life. Beyond this number of starts, it is then common that these injection pumps and these reinforced starters fail. The disadvantage of Stop & Start systems is that they lead to a multiplication of the number of engine starts. More precisely, according to the use made of the vehicle, the number of engine starting cycles is multiplied by a coefficient of between 3 and 10. The injection pumps and the starters then arrive at the end of their life before the engine, so that it becomes necessary to replace them one or more times. This replacement operation being particularly expensive and generating waste, the benefit of reducing fuel and reducing polluting emissions is being questioned.

OBJECT OF THE INVENTION In order to overcome the aforementioned drawback of the state of the art, the present invention proposes a method making it possible to vary the frequency of the automatic engine stops to adjust the life expectancy of the starter and the engine. injection pump with that of the engine.

More particularly, according to the invention, a method as defined in the introduction is proposed, in which the delay time is determined as a function of the number of start cycles already performed by the starter. Thus, thanks to the invention, as long as the life expectancy of the starter and the injection pump is important, the Stop & Start system is used optimally, so as to reduce the fuel consumption of the engine. However, when the life expectancy of the starter and the injection pump decreases, it is expected to increase the delay time so as to reduce the frequency of stopping the engine. Thus the life expectancy of the starter and the injection pump is extended. The delay time can be increased indefinitely, so that in the long run, the motor stops only when the driver turns off the ignition. The goal is then that the starter is able to start the engine until it breaks.

Other advantageous and non-limiting features of the process according to the invention are the following: the duration of the delay increases continuously as a function of the number of start cycles; the delay time increases in steps according to the number of startup cycles; at each start of the internal combustion engine, a counter of at least one unit is incremented, the delay time being determined as a function of the counter; the delay time remains constant when the counter varies between 1 and a first determined threshold, then increases beyond this first threshold; the first threshold is between 1 and 200,000; - the starter being designed to perform a maximum number of startup cycles of the internal combustion engine, the first threshold is predetermined according to said maximum number; the first threshold is determined according to the urban, semi-urban or road use of the motor vehicle; - The delay time is determined also according to the urban, semi-urban or road use of the motor vehicle. DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description, with reference to the appended drawings, given by way of non-limiting example, will make it clear what the invention consists of and how it can be achieved. In the accompanying drawings: - Figure 1 is a schematic view of an internal combustion engine equipped with a computer adapted to implement a control method according to the invention; FIGS. 2A, 2B and 3 are representative curves of the evolution of the delay time as a function of the number of starts already performed by the motor of FIG. 1; and FIG. 4 is a diagram illustrating the various steps of implementing the control method according to the invention.

In the description, the terms "upstream" and "downstream" will be used in the direction of gas flow, from the point of sampling the fresh air into the atmosphere to the exit of the gases burned by a pot catalytic. Device In Figure 1, there is shown schematically an internal combustion engine 1 of a motor vehicle, which comprises a motor unit 10 provided with a crankshaft and four pistons (not shown) housed in four cylinders 11. This engine is here Compression ignition (Diesel). It could also be spark ignition (gasoline).

Upstream of the cylinders 11, the internal combustion engine 1 comprises an intake line 20 provided with an air filter 21 which filters the fresh air taken from the atmosphere. This intake line 20 further comprises a compressor 22 which compresses the fresh air filtered by the air filter 21, and a main air cooler 23 which cools this fresh compressed air. The intake line 20 opens into an air distributor 24 which brings fresh air into each of the cylinders 11 of the engine block 10. At the outlet of the cylinders 11, the internal combustion engine 1 comprises an exhaust line 30 of burnt gas. This exhaust line 30 comprises an exhaust manifold 31 into which the gases that have been previously burned into the cylinders 11 are discharged. This exhaust line 30 extends to burned gas oxidation means formed here by an auxiliary oxidation catalyst 33 and a catalytic converter 34. The exhaust line 30 further comprises, between the exhaust manifold 31 and the oxidation means, a turbine 32 which is rotated by the flow of burnt gas to operate the compressor 22. The internal combustion engine 1 further comprises a fuel injection line 40 in the cylinders 11. This injection line 40 comprises a fuel tank 41 and an injection pump 42 which is designed to take the fuel in the tank 41 in order to bring it under pressure into a distribution rail 43. This injection line also comprises four injectors 44, whose inlets communicate with the fuel. distribution garlic 43 and whose outputs open respectively into the four cylinders 11. The internal combustion engine 1 further comprises a starter 50, in this case an electric motor, adapted to rotate the crankshaft to start the engine. As shown in Figure 1, the starter 50 is rotatably connected to the crankshaft by a gear mechanism 51.

In order to control the various components of the internal combustion engine 1 and notably the starter 50 and the injectors 44, there is provided a computer 60 comprising a processor (CPU), a random access memory (RAM), a read only memory (ROM), converters analog-digital (A / D), and different input and output interfaces.

In its RAM, the computer 60 stores in particular a counter N corresponding to the number of startup cycles already performed by the starter 50. Thanks to its input interfaces, the computer 60 is adapted to receive input signals from different sensors. These input signals relate to the operation of the engine (engine load, engine speed, vehicle vehicle speed, brake pedal depressing rate Txfrein, Txacc accelerator pedal depressure rate, engine temperature). water, ...). By means of a predetermined mapping on a test bench and stored in its read-only memory, the computer 60 is adapted to generate, for each operating condition of the engine, output signals. Finally, thanks to its output interfaces, the controller is adapted to transmit these output signals to the various components of the engine, in particular the fuel injectors 44 and the starter 50. Conventionally, when the driver of the motor vehicle puts the ignition, the The computer 60 initiates and then controls the starter 50 and the fuel injectors 5 so that they start the engine. Once the engine has started, the computer 60 then increments the counter N by a unit No equal to 1, in order to update the number of start cycles performed by the starter 50. When the engine is started, the fresh air taken in the atmosphere through the inlet line 20 is filtered by the air filter 21, compressed by the compressor 22, cooled by the main air cooler 23, and then burned in the cylinders 11. At their exit from the cylinders 11 , the flue gas is expanded in the turbine 32, then treated and filtered by the auxiliary oxidation catalyst 33 and the catalytic converter 34 before being released into the atmosphere. The computer 60 then continuously measures the water temperature of the engine. During a cold start, as long as the water temperature remains below a temperature threshold, the computer 60 controls the fuel injectors 44 so that the engine remains constantly running, unless of course the driver turns off the ignition. When the water temperature exceeds this temperature threshold, which means that the engine is hot, the computer 60 implements a method for controlling the automatic shutdown of the internal combustion engine 1. Such a method, known as the The term Stop & Start, is designed to stop the engine 25 when the vehicle is stopped for a period of time to reduce the fuel consumption of the engine. More specifically, according to this method, the computer 60 controls the stopping of the injection of fuel into the cylinders 11, that is to say the stopping of the engine, when stopping conditions are met during a period of given time, referred to as the Tempo dwell time. According to a particularly advantageous characteristic of the control method in accordance with the invention, the delay time Tempo is determined as a function of the number of start cycles N already accomplished by the starter 50. FIG. of this control method. As shown in this figure, the computer 60 begins by reading the counter N and then deduces therefrom, from a predetermined abacus on a test bench and stored in its read-only memory, the delay time Tempo. This chart is shown schematically by a curve in Figure 2A. As this curve shows, the delay time T0 increases in steps according to the counter N. More precisely, as long as the counter N remains below a first threshold S1, the delay time T0 remains constant and equal to a first value, for example here 4 seconds. In other words, since the starter 50 still has a significant life expectancy, the delay time is optimally set so that the automatic shutdown of the engine is controlled so as to reduce its fuel consumption. When the counter N is between this first threshold S1 and a second threshold S2, the delay time T0 is adjusted to a second value strictly greater than the first, for example here 10 seconds. In other words, since the starter 50 has a life expectancy that is reduced, the delay time is set so that the automatic engine stop is controlled less frequently, in order to extend the life of the motor. starter life 50 compared to that of the rest of the engine. Finally, when the counter N is greater than this second threshold S2, the delay time Tempo is adjusted to a third value strictly greater than the second, here equal to 1000 seconds to simulate the infinite. In other words, since the life expectancy of the starter 50 is considerably reduced, the delay time is adjusted so that the engine stop is no longer controlled automatically, so that the starter 50 can continue to operate until 'in time that the engine breaks. The first and second thresholds S1, S2 are preferably predetermined on test bench and stored in the read-only memory of the computer 60. They are chosen according to the maximum number S3 of starts that the starter 50 is designed to perform. Here, these first and second thresholds S1, S2 are respectively equal to 150,000 and 250,000 startup cycles. These first and second thresholds S1, S2 may be predetermined depending also on the urban, semi-urban or road use for which the motor vehicle is designed.

We know that the frequency of stops of a commercial vehicle in the city will be higher than that of a family vehicle in the countryside. It is then likely that the commercial vehicle will perform 250,000 startup cycles while it is unlikely that the family vehicle will reach this number of startup cycles. It will therefore be necessary to give priority to the life of the starter 50 of the commercial vehicle by decreasing the value of its first threshold SI. It will however be advantageous to focus on reducing the fuel consumption of the family vehicle by increasing the value of its first threshold SI. It is also possible to vary this first threshold SI during the life of the engine, by determining the number of stops of the vehicle per kilometer traveled, by deducting the urban, semi-urban or road use that is actually vehicle, and reducing or increasing this first threshold SI according to the use deduced. As shown in FIG. 4, the computer 60 then acquires the instant vehicle vehicle speed, the brake pedal depressing rate Txfrein, and the rate of depression of the accelerator pedal Txacc (and / or the clutch pedal).

The conditions of automatic stopping of the vehicle can be related to various driving parameters of the motor vehicle. Here, the first condition is that the speed of the vehicle vehicle is less than a speed threshold Vo, for example 5 kilometers per hour. The second condition, cumulative with the first, is that the rate of depression of the brake pedal Txfrein is greater than a single depression, for example 10%. As long as these two stopping conditions are not met, the computer 60 continues to acquire the instantaneous speed of the vehicle V, the rate of depression of the brake pedal Txfrein, and the rate of depression of the pedal. Txacc accelerator (and / or clutch pedal).

When these two stopping conditions are met, the computer 60 starts a countdown to check that they remain together during the delay time Tempo. If this is not the case for example because the driver releases the brake pedal, the computer 60 stops the countdown.

If this is however the case, the computer 60 automatically controls the fuel injection stop in the cylinders, that is to say the stopping of the engine. The computer 60, which remains powered by the vehicle battery, then continues to acquire the rate of depression of the accelerator pedal Txacc (and / or the clutch pedal). When it exceeds a predetermined threshold signifying that the driver wishes to restart, for example equal to 5%, the computer 60 controls the starter 50 and the fuel injectors 44 so that they restart the internal combustion engine 1. The calculator 60 then increments the counter of a unit No to memorize the new engine start cycle that the starter 50 has just performed.

The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind. In particular, as shown in FIG. 2B, it will be possible for the Tempo delay time to increase with a greater number of steps. Moreover, as shown in FIG. 3, it is possible to provide that the time delay time Tempo increases not in steps, but on the contrary continuously as a function of the counter N. In this variant, the abacus stored in the computer's read-only memory is then designed in such a way that the delay time Tempo remains constant when the counter N is less than the first threshold S1, and so that it grows beyond this first threshold more and more rapidly until reaching the threshold infinity when the counter N exceeds the second threshold S2. In another variant, the delay time Tempo will be determined not only according to the counter N, but also according to the urban, semi-urban or road use of the motor vehicle. More specifically, the computer 60 can determine the number of stops of the vehicle per kilometer traveled, deduce the urban, semi-urban or road use that is actually made of the vehicle, and increase the delay time of for example 2 seconds if the use of the vehicle is urban or reduce the delay time of for example 1 second if the use of the vehicle is road. According to another variant, after each engine start, the counter N may be incremented by one or more than one unit No, depending on whether the engine was cold or not. Indeed, since a cold start is more difficult to achieve for the starter 50 hot start, we can plan to increment the counter N of two units for a cold start and a unit for a start hot.

Claims (9)

REVENDICATIONS1. A method of controlling the automatic shutdown of an internal combustion engine (1) of a motor vehicle when stopping conditions are met during a period of time greater than a delay time (Tempo), said internal combustion engine ( 1) being equipped with a starter (50) adapted to perform a plurality of starting cycles, characterized in that the delay time (Tempo) is determined as a function of the number of starting cycles (N) performed by the starter ( 50). 2. Method according to the preceding claim, wherein the delay time (Tempo) increases continuously as a function of said number of start cycles (N). The method of claim 1, wherein the delay time (Tempo) increases incrementally as a function of said number of start cycles (N). 4. Method according to one of the preceding claims, wherein at each start of the internal combustion engine (1), a counter (N) of at least one unit (No) is incremented, and in which the delay time ( Tempo) is determined according to the counter (N). 5. Method according to the preceding claim, wherein the delay time (Tempo) remains constant when the counter (N) varies between 1 and a first threshold (SI) determined, then increases beyond this first threshold. 6. Method according to the preceding claim, wherein said first threshold (SI) is between 1 and 200 000. 7. Method according to one of the two preceding claims, wherein, said starter (50) being designed to perform a maximum number (S3) of starting cycles of the internal combustion engine (1), said first threshold (SI) is predetermined according to said maximum number (S3). 8. Method according to one of the three preceding claims, wherein said first threshold (SI) is determined according to the urban, semiurban or road use of the motor vehicle. 9. Method according to one of the preceding claims, wherein the delay time (Tempo) is determined also according to the urban, semi-urban or road use of the motor vehicle.