FR3077102A1 - METHOD AND SYSTEM FOR COLD STARTING AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

The cold start method of an internal combustion engine comprises: a step (103) for activating a starter providing a first pair; a step (106) for activating an alternator starter providing a second pair; so as to add the second torque to the first torque to start said internal combustion engine, and - a step (102) for initializing a criterion ensuring not to execute said step (106) for activating the alternator starter before said step (103) of activation of the starter.

Description

Method and system for cold starting an internal combustion engine

The invention relates to a method of cold starting an internal combustion engine comprising a step of activating a starter providing a torque applied to the engine of a vehicle, in particular of a motor vehicle, to start it on control of a vehicle user.

The invention also relates to a system comprising the aforementioned starter and an alternator starter generally used for automatically restarting the internal combustion engine, following an automatic stop of sufficiently short duration so that the engine remains substantially at its nominal operating temperature. The alternator starter operating at a substantially nominal operating temperature of the internal combustion engine, is very happy to provide much less torque than is necessary for a cold start.

Generally, the starter and the alternator starter are used independently of each other, the first for voluntary cold starts and the second for automatic hot starts. The starter is then usually dimensioned to provide a sufficient torque value to start the internal combustion engine for a given type of engine and for all the conditions of use provided for vehicles equipped with this type of engine. For engines requiring a high torque such as diesel engines or for vehicles brought to start in very cold weather, the methods and systems usually implemented, require starters sized to values which have disadvantages in terms of cost, diversity and high weight.

In the prior art, the document FR2839119 indeed proposes to involve the starter of the cold start to support the alternator starter of automatic hot restart, in ace of detection of a bad start. However, this document does not make it possible to respond to the technical problem posed by dimensioning the starter to values sufficiently high to cold start the internal combustion engine under numerous conditions which may arise in a motor vehicle.

To remedy the drawbacks of the prior art, the subject of the invention is a method of cold starting an internal combustion engine comprising a step of activating a starter providing a first torque, characterized in that that he understands:

a step of activating an alternator starter providing a second torque so as to add the second torque to the first torque to start said internal combustion engine, and

a step for initializing a criterion ensuring that said step of activating the alternator starter is not executed before said step of activating the starter.

In particular, the starter is of the gear type.

In particular also, the alerno starter is of the belt type.

In particular, said criterion includes a time delay positioned in the initialization step.

More particularly, the starting process then comprises:

a step of decrementing said time delay, and

a step executed following the step of activating the starter, consisting of triggering said step of decrementation if said time delay is at a non-zero value, and consisting of triggering said step of activating the alternator starter if said time delay is at zero.

Particularly also, said criterion includes a starter supply voltage level previously measured in the initialization step.

More particularly, the starting process then comprises:

a step of posterior measurement of said voltage level, and

a step executed following the step of activating the starter, consisting in triggering said later measurement step if a difference between the measured voltage level and the previously measured voltage level is less in absolute value than a threshold of voltage drop, and consisting in triggering said step of activating the alternator starter if said difference between the voltage level subsequently measured and the voltage level previously measured is greater in absolute value than the voltage drop threshold.

Preferably, the starting method comprises a step of simultaneously deactivating the starter and the alternator starter if the internal combustion engine has started.

The invention also relates to a cold start system of an internal combustion engine comprising a starter capable of providing a first torque and an alternator starter capable of providing a second torque, characterized in that it comprises an onboard computer arranged to implement the starting process described above.

Advantageously, an implementation of the system allows the starter to be undersized to start the internal combustion engine by itself at least in the event of low outside temperature.

Advantageously also, it becomes possible to lighten both in terms of weight and cost, a motor vehicle comprising the cold start system described above.

Other characteristics and advantages of the invention will be better understood on reading the description of an embodiment which is in no way limitative, and illustrated by the appended drawings, in which:

- Figure 1 shows a system for implementing the invention;

- Figure 2 shows a process according to the invention which can be implemented on the system of Figure 1.

FIG. 1 illustrates a cold start system of an internal combustion engine (not shown) comprising a starter 1 connected on one of its terminals to the ground of a vehicle, in particular of a motor vehicle, and on the other of its terminals to a battery 6, in particular a so-called service battery, for delivering a nominal DC voltage of 12V, so as for example to make the starter 1 able to provide a first torque. The starter 1 is a conventional starter usually used for each cold start. The starter is for example of the gear type. In a manner known per se, the starter 1 then has a rotor end which engages on the internal combustion engine to drive it in rotation so as to start it cold, in other words when the engine has not yet reached its nominal operating temperature.

An on-board computer 5 controls the starter 1 by means of a relay control line 3, also known per se, in particular when a vehicle user starts the internal combustion engine locally by means of a button, d '' a key or remotely using a telecommunication device.

The system illustrated in FIG. 1 also includes an alternator starter 2, connected on one of its terminals to the ground of the vehicle, and on the other of its terminals to the battery 6, so as to make the alternator starter 2 suitable for get a second couple. The alternator starter is for example of the belt type. In a manner known per se, the alternator starter 2 then has a rotor end in permanent connection with the internal combustion engine, not excited to coast in a speed proportional to that of the engine, excited to the stator to supply via the rotor the second torque to the internal combustion engine, excited to the rotor to transmit via the stator to the battery 6 an energy taken from the internal combustion engine after starting if necessary. The second torque is generally provided to drive the internal combustion engine in rotation so as to restart it warm, in other words when the engine has already reached its nominal operating temperature, for example following a temporary stop at a crossroads or in a traffic jam.

The on-board computer 5 controls the alternator starter 2 by means of a command line 4 of the onboard network type, CAN, LIN or automotive Ethernet, known moreover per se, in particular for sending to the alernator starter 2 an excitation instruction in function of a stop or taxi mode determined by another computer or by another module of the on-board computer 5.

The on-board computer 5 hosts, or accesses in memory, a computer program comprising instructions which make it possible to implement the start-up method described below when the on-board computer 5 executes said computer program in real time.

The cold start process of an internal combustion engine illustrated in Figure 2 from a sequence start step

100 which references the sequence of instructions of the method among others within the computer 5, includes a standby step 101 which tests a cold start request signal from the user so as to loop back onto it. even in the absence of a cold start request (negative response to the test) and which directs the process to a step 103 in the event of a positive response validating a cold start request.

Step 103 consists in activating the starter 1 so as to provide the first torque to be applied to the internal combustion engine.

A step 106 consists in activating the alternator starter 2 to provide the second couple so as to add it to the first couple. Thus the sum of the two couples is used to start the internal combustion engine.

If the vehicle is in conditions favorable to allow starting of the internal combustion engine with an application of the only first torque, the second torque provided by the alternator starter 2 then simply relieves the starter 1 by allowing faster starting of the combustion engine internal.

If the vehicle is in unfavorable conditions to allow an internal combustion engine to be started with an application of the only first torque, for example by extreme cold or insufficient lubrication of the engine, the second torque provided by the alternator starter 2 then completes the first torque provided by starter 1.

Thus it is no longer necessary to size the starter 1 for starting the internal combustion engine alone, whatever the conditions of temperature and pressure of the lubricating oil. It becomes possible to undersize the starter 1 with respect to a use not benefiting from the process, to start the internal combustion engine, for example in the event of low outside temperature. It is sufficient to size the starter 1 to obtain a first torque which, added to the second torque provided by the alternator starter, makes it possible to start the internal combustion engine whatever the conditions under which the vehicle may be, for which provision is usually the starter.

It thus becomes possible to use the same starter 1 for heavy vehicles or with a diesel engine as for light vehicles or with a petrol engine for which the first torque is sufficient on its own when the engine starts. We can then make economies of scale in terms of supply.

A step 102 executed simultaneously or just before the step 103 consists in initializing a criterion ensuring not to execute the step 106 of activation of the alternator starter 2 before the step 103 of activation of the starter 1, or in other terms ensuring that step 103 is executed before, or at the latest simultaneously with, step 106 in a deterministic manner, independently of conditions external to the system.

For example, in the case of a starter type 1 with gears, it is avoided that the alternator starter 2 does not start to rotate the internal combustion engine before the drive of the pinion of starter 1.

For example, in the case of a belt-type alternator, it is avoided to initiate a belt slip resulting from the second torque which would not be sufficient to start the internal combustion engine which had remained before stopping for too long.

Different criteria can be used, alone or in combination.

For example, the criterion includes a time delay positioned in initialization step 102 at a value high enough to overcome the delays in communication and establishment of currents, and low enough not to block the starter 1 too long when stopped. to grill the windings. A value of the order of 10 ms gives a good order of magnitude of a satisfactory timeout value.

A step 104 executed following the step 103 of activation of the starter, consists in triggering the step 106 of activation of the alternator starter if said delay reaches its expiration period identifiable by a zero value, and in triggering a step 105 of decrementing the time delay if the time delay is at a non-zero value. Step 105 loops back to step 104 for a new verification of the decremented value of the timer. The decrement can correspond to a portion of the initial value and in this case several passages in steps 104 and 105 will take place before triggering step 106. The decrement can also correspond to the initial value, for example of 10 ms for a program execution cycle time of 10 ms, and in this case only one passage in step 105 will take place before triggering step 106.

In the latter case, a binary variable set to 1 in step 102 and set to zero in step 105, provides the same effect.

For example again, another criterion can be defined which includes a starter supply voltage level previously measured in initialization step 102, that is to say before the coupling of the starter 1 to the battery 6 does not causes the voltage to drop due to the current consumed by the starter.

Step 104 executed following step 103 of activation of the starter, then consists in triggering step 106 of activation of the alternator starter if a difference between the measurable voltage level after activation of the starter 1, and the voltage level previously measured in step 102, is greater in absolute value than a threshold representative of a minimum voltage drop during the effective activation of the starter 1. Step 104 triggers a step 105 of subsequent measurement of the voltage level, if a difference between the measured voltage level and the previously measured voltage level is less in absolute value than the voltage drop threshold. This criterion appears more robust than the previous one because it is based on an effective current consumption of the starter 1 to provide the first torque.

It is also possible to combine several of the criteria described above, or others, in each of the steps 102, 104 and 105 to better secure the sequence of steps 103 and 106.

Following step 106, a step 107 checks whether the internal combustion engine has started. In the event of a positive response, step 107 triggers a step 109 of simultaneous deactivation of the starter and the alternator-starter. In the event of a negative response, step 107 triggers a step 108 of verification of a maximum duration reached to avoid supplying the starter and the alternator starter for too long without being able to start the internal combustion engine. In the event of a positive response, step 108 directly triggers step 109 of simultaneous deactivation of the starter and the alternator-starter. If the answer is negative, step 108 loops back to step 107.

Thus it is possible to lighten the motor vehicle by equipping it with the cold start system which implements the above process, both in terms of manufacturing cost and weight and therefore energy consumption.

Claims (11)

1. Method for cold starting an internal combustion engine comprising a step (103) of activating a starter providing a first torque, characterized in that it comprises: a step (106) of activating an alternator starter providing a second torque so as to add the second torque to the first torque to start said internal combustion engine, and a step (102) for initializing a criterion ensuring that said step (106) of activation of the alternator starter is not executed before said step (103) of activation of the starter. 2. Starting method according to claim 1, characterized in that the starter is of the gear type. 3. Starting method according to one of claims 1 or 2, characterized in that the alerno starter is of the belt type. 4. Starting method according to one of claims 1 to 3, characterized in that said criterion comprises a time delay positioned in step (102) of initialization. 5. Starting method according to claim 4, characterized in that it comprises: a step (105) of decrementing said time delay, and a step (104) executed following the step (103) of activation of the starter, consisting of triggering said step (105) of decrementation if said time delay is at a non-zero value, and consisting of triggering said step ( 106) activation of the alternator-starter if said time delay is at a zero value. 6. Starting method according to one of claims 1 to 3, characterized in that said criterion comprises a level of supply voltage of the starter previously measured in step (102) of initialization. 7. Starting method according to claim 6, characterized in that it comprises: a step (105) for later measurement of said voltage level, and - a step (104) executed following the step (103) of activation of the starter, consisting of triggering said step (105) of posterior measurement if a difference between the voltage level posteriorly measured and the voltage level beforehand measured is less in absolute value than a voltage drop threshold, and consisting in triggering said step (106) of activation of the alternator starter if said difference between the voltage level subsequently measured and the voltage level previously measured is greater in absolute value at the voltage drop threshold. 8. Starting method according to any one of claims 1 to 7, characterized in that it comprises a step (109) of simultaneous deactivation of the starter and the alternator starter if the internal combustion engine has started. 9. Cold start system of an internal combustion engine comprising a starter (1) capable of providing a first torque and an alternator starter (2) capable of providing a second torque, characterized in that it comprises an on-board computer ( 5) arranged to implement the starting process according to any one of claims 1 to 8. 5 10. Cold start system according to claim 9, characterized in that the starter (1) is undersized to start the internal combustion engine at least in the event of low outside temperature. 10 11. Motor vehicle characterized in that it comprises a cold start system according to one of claims 9 or 10.