Method for starting a motor vehicle

Abstract

The invention relates to a method for starting a motor vehicle comprising an electric powertrain including at least one electric traction machine, a traction battery, and a high-voltage network electrically connecting the electric machine to the traction battery, as well as a starting control means (1). Following a preliminary step of receiving a starting request signal (12) from the starting control means, the method comprises the following steps: Measurement of a residual voltage value Vr in the high-voltage network; If the residual voltage value Vr thus measured is within a range delimited by two predetermined threshold voltage values ​​Vsb and Vsh, a delay is set before sending a starting authorization signal (32) to the electric powertrain; and, As soon as the delay has elapsed, conditional sending of the starting authorization signal to the electric powertrain. Figure 1

Description

Title of the invention: Method for starting a motor vehicle Technical field of the invention

[0001] The invention relates, in general, to the technical field of methods for starting powertrains.

[0002] In particular, the invention relates to a method for starting an electric powertrain comprising one or more electric machines. State of the prior art

[0003] Today, in a so-called "second generation" electric motor vehicle, when contactors of a traction battery are open, no voltage should be present on a high voltage network of said electric motor vehicle. However, on certain second generation electric motor vehicles, depending on a configuration of these electric motor vehicles (battery supplier, type of electric machine, etc.), a residual voltage of a few volts (generally around 12V) on the high voltage network (generally a network of 400V or more) may be observed.

[0004] The presence of this residual voltage can be due to different factors. First, it may be necessary for diagnostics, particularly on the high-voltage battery side. In this case, it is the battery itself that injects these few volts in order to be able to self-diagnose. Then, this residual voltage can also come from a "leak" from a 12V network to the high-voltage network. In this case, it is one of the systems connected to both the 12V network and the vehicle's high-voltage network (DC / DC converter, air conditioning compressor, electrical machine, etc.) that untimely injects these few volts into the high-voltage network.

[0005] It should be noted that the injected voltage is very low and does not present any risk to the system, the motor vehicle or its users. This voltage is very low and is of the order of 12V.

[0006] A particular life situation concerns a moment when a driver makes a request to start the electric powertrain (by acting on an ignition key or by pressing the start button with a brake pedal pressed) even though the computers of the electric motor vehicle have started a sleep phase and the voltage on the high voltage network is located in a particular voltage range (generally between 8 and 4V). The fact of requesting the activation of the electric powertrain in this specific voltage range has the consequence of putting one or more electric machines of electric powertrain traction in protection.

[0007] The falling asleep of the computers, in particular the falling asleep of a traction battery computer, causes a passive discharge of the high voltage network, the residual voltage will then drop until it is completely zero. This passive discharge lasts approximately seven to eight seconds (the time to go from 12V to 0V). Thus, the protection of one of the electrical machines occurs when, during this passive discharge, the residual voltage being in the aforementioned particular voltage range, the driver requests a start of the electric motor vehicle.

[0008] A protection of the electric machine takes place because during a phase of activation of the electric powertrain (which follows the request to start the latter by the driver), one or more electric machines have detected, during an activation phase, the presence of a voltage greater than a voltage threshold value while the contactors of the traction battery are not yet closed, therefore still open. This thus prevents the activation of the electric powertrain.

[0009] Therefore, in order to rehabilitate the electrical machine(s) in protection, the driver must turn off the electric motor vehicle and wait for all the computers in said electric motor vehicle to go to sleep, which can take at least two minutes. Without any alert indicating the status of the electric motor vehicle or what the driver should do, the latter will unfortunately think (wrongly) that the electric motor vehicle has broken down.

[0010] Document EPI221765 describes that, to facilitate the starting of the AC motor, a time delay is applied in order to wait until there is no more residual voltage. Statement of the invention

[0011] The invention aims to remedy all or part of the drawbacks of the state of the art by proposing in particular a solution allowing, in the particular life situation mentioned above, rapid starting of the electric powertrain while preventing at least one of the electric machines from going into protection mode.

[0012] To do this, according to a first aspect of the invention, a method is proposed for starting a motor vehicle comprising an electric powertrain comprising at least one electric traction machine, a traction battery and a high-voltage network electrically connecting the electric machine to the traction battery, as well as a starting control means. Following a preliminary step of receiving a start request signal from the starting control means, the method comprises the following steps: • Measurement of a residual voltage value Vr in the high voltage network; • If the residual voltage value Vr thus measured is included in an in interval delimited by two predetermined voltage threshold values ​​Vsb and Vsh, time delay for sending a signal authorizing the start of the electric powertrain; and, • As soon as the time delay has elapsed, conditional sending of a signal authorizing the start of the electric powertrain.

[0013] According to one embodiment, the voltage threshold value Vsb is less than or equal to the voltage threshold value Vsh.

[0014] According to one embodiment, the voltage threshold values ​​Vsb and Vsh are between 0 V and 12 V.

[0015] According to one embodiment, the voltage threshold value Vsb is approximately 4 V.

[0016] According to one embodiment, the voltage threshold value Vsh is approximately 8 V.

[0017] According to one embodiment, the time delay is of a predetermined duration t, especially between 3 and 5 seconds.

[0018] According to one embodiment, the time delay duration t lasts as long as the value of the residual voltage Vr remains within the interval delimited by the two voltage threshold values ​​Vsb and Vsh.

[0019] According to another aspect of the invention, there is provided a powertrain for a motor vehicle comprising a method for starting an electric powertrain having at least one of the preceding technical characteristics.

[0020] According to yet another aspect of the invention, there is provided a motor vehicle comprising a powertrain having one of the preceding technical characteristics. brief description of the figures

[0021] 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 schematic view of a simplified arrangement allowing the start-up of an electric powertrain; • [Fig.2]: a timeline illustrating an implementation of a process of starting an electric powertrain according to the invention when starting the electric motor vehicle is requested without starting the electric powertrain; • [Fig.3]: a timing diagram illustrating an implementation of the method for starting an electric powertrain according to the invention when starting the electric motor vehicle is requested with starting of the electric powertrain.

[0022] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED description of an embodiment

[0023] [Fig.l] illustrates a schematic view of a simplified arrangement allowing start-up of an electric powertrain. An electric motor vehicle comprises an electric powertrain, itself composed of one or more electric traction machines directly connected to the wheels via a gear train. The electric motor vehicle further comprises a traction battery, a high-voltage network electrically connecting the traction battery to the one or more electric machines of the electric powertrain. Furthermore, the electric motor vehicle comprises other devices electrically connected to the aforementioned high-voltage network, such as, for example, a DC / DC converter making it possible to support a 12 V network by the high-voltage network (powered by the traction battery) or an air conditioning compressor.

[0024] In addition, the electric motor vehicle comprises a vehicle computer 2 and the electric powertrain comprises a drive train computer 3. Finally, the electric motor vehicle comprises a means 1 for controlling a start of the motor vehicle, located in a passenger compartment of said electric motor vehicle. The means 1 for controlling a start of the motor vehicle is either a start button or a Neiman actuated by a start key, both known per se. The vehicle computer 2 receives a start request signal 12 from the control means 1. The start request signal 12 comes either from pressing the start button with a brake pedal pressed or not or if the start key turns within the Neiman to a “start” position.

[0025] From then on, the vehicle computer 2 sends a request 23 for activation of the electric powertrain to the computer of the traction chain 3. In return, the computer of the traction chain 3 sends, under conditions, to the vehicle computer 2 a signal authorizing activation 32 of the electric powertrain.

[0026] The computer of the traction chain 3 can, via the activation authorization signal 32: Authorize activation or Prohibit activation or Delay activation.

[0027] In addition, the computer of the traction chain 3 authorizes the activation of the electric powertrain to the vehicle computer 2, if said electric powertrain is in a safe state for starting, that is to say that: • the brake pedal is pressed, • a gear lever is in a Parking or Neutral position, • no fault is detected on the traction chain, whether on the side of the traction battery, of the electric machine(s) or other, and • the electric motor vehicle is fully “awakened” (all computers are communicating and initialized).

[0028] If one of the first three conditions above is missing, then starting the electric motor vehicle is prohibited. This has the consequence of not starting the electric motor vehicle even if the driver requests it via the control means 1. As long as the fourth condition above is not satisfied, starting the electric motor vehicle is then delayed.

[0029] However, within an electric motor vehicle, it is possible to observe a residual voltage Vr of a few volts on the high voltage network when the contactors of the traction battery are open, that is to say that the high voltage network is not supplied by said traction battery.

[0030] As a reminder, the presence of this residual voltage Vr can be due to different things. This residual voltage Vr can be caused directly by the traction battery which, even with the contactors open, can inject a little voltage into the high voltage network to self-diagnose. This residual voltage Vr can also be due to "leaks" from the electrical devices connected to the high voltage network. These leaks can therefore come either from the electrical machine(s), the DC / DC converter, the air conditioning compressor, etc.: from any component of the electric powertrain or the electric motor vehicle connected to the high voltage network.

[0031] This residual voltage Vr has a maximum value V. The value V is of the order of 12 V for example. During a sleep phase of the computers, in particular the drive train computer, this residual voltage Vr decreases to zero before the electric motor vehicle goes completely to sleep (no more computers communicate on dedicated networks).

[0032] While the contactors of the traction battery are open, a method for starting an electric powertrain according to the invention will come into operation here. Indeed, the method for starting an electric powertrain according to the invention, implemented in the computer of the traction chain 3, will in a preliminary step receive a signal corresponding to a request for activation 23 of the electric powertrain sent by the vehicle computer 2.

[0033] Then in a first step, then possibly regularly or continuously thereafter during an implementation of said method for starting an electric powertrain according to the invention, the method for starting an electric powertrain according to the invention measures a residual voltage value Vr present on the high voltage network.

[0034] Then in a second step, the method for starting an electric powertrain according to the invention checks whether this residual voltage value Vr is included in an interval delimited by two voltage threshold values ​​Vsb and Vsh predetermined beforehand by calibration. If this is the case, then the method for starting an electric powertrain according to the invention delays the activation (starting) of the electric powertrain and sends an activation authorization signal 32 of the electric powertrain to the vehicle computer 2, the activation authorization signal 32 then corresponding to a “stand-by” state. This “stand-by” state makes it possible to delay the activation of the electric powertrain of the electric motor vehicle.

[0035] The two voltage threshold values ​​Vsb and Vsh predetermined beforehand by calibration are less than or equal to a voltage value V of a maximum residual voltage Vr within the high voltage network, the contactors of the traction battery being in the open position. In practice, currently the voltage value V is of the order of 12 V. On the other hand, the low voltage threshold value Vsb is less than or equal to the high voltage threshold value Vsh. For example, the high voltage threshold value Vsh is approximately 8 V and the low voltage threshold value Vsb is approximately 4 V.

[0036] According to a first embodiment of the method for starting an electric powertrain according to the invention, the time delay is of a predetermined duration t, of the order of a few seconds, between three and five seconds for example. According to a second embodiment of the method for starting an electric powertrain according to the invention, the time delay as long as the residual voltage value Vr present on the high voltage network is included in the aforementioned interval, that is to say between the two predetermined voltage threshold values ​​Vsb and Vsh.

[0037] As soon as the residual voltage value Vr leaves this interval, either because the residual voltage Vr continues to be cancelled due to the sleep of the at least one computer(s) of vehicle 2 and of the powertrain 3 (exit from the bottom of the interval), or because an action by the driver on the control means 1 is detected; in fact, an action on the control means 1 (whether to start or not) triggers a wake-up of the electric motor vehicle, which will again cause the increase of this residual voltage Vr (exit from the top of the interval), the method for starting an electric powertrain according to the invention, in a third step, conditionally sends a signal authorizing the start of the electric powertrain.This shipment is conditional on the fulfillment of the three other conditions mentioned above (brake pedal pressed, gear lever in Parking or Neutral position, no fault detected on the powertrain).

[0038] We will now briefly describe, with reference to Figures 2 and 3, two examples of operation of the method for starting a powertrain. electric according to the invention which has just been described.

[0039] In the two illustrated timing diagrams, the electric motor vehicle is initially in a sleeping state, the residual voltage Vr is almost zero. Then at a time T1, the control means 1 is implemented without pressing the brake pedal. The electric motor vehicle wakes up and the residual voltage Vr increases to the voltage value V. Concerning the state of the contactors of the traction battery, the latter can then either close or remain open, this choice is configurable and depends on the configuration of the electric motor vehicle (suppliers of the traction battery, type of electric machine, etc.). Then at a time t2, the control means is again implemented to turn off the electric motor vehicle. From then on, the computer of the traction chain opens the contactors of the traction battery (if they were closed at the previous action of the control means 1 at the time T1).A self-diagnosis is carried out, the residual voltage Vr remains at the voltage value V until time t3 or the traction chain computer goes into sleep mode. The residual voltage Vr then decreases due to a passive discharge managed by the traction battery itself. During this decrease, the value of the residual voltage Vr enters the interval 10 delimited by the two predetermined voltage threshold values ​​Vsb and Vsh.

[0040] In the timing diagram of [Fig.2], at time t4, an action is again performed on the control means, while the value of the voltage Vr is in the interval 10, and there is no pressure on the brake pedal. From then on, the value of the residual voltage Vr increases again within the interval 10 and the method for starting an electric powertrain according to the invention will trigger a time delay for the conditional sending of an activation authorization signal 32 of the electric powertrain, and this, until a time t6 when the value of the residual voltage Vr leaves the upper part of the interval 10. At this time, the method for starting an electric powertrain according to the invention allows a conditional sending of an activation authorization signal 32 of the electric powertrain.The activation authorization signal 32 then corresponds to a “prohibited” state, because, at a minimum, no brake pedal has been pressed. But the electric motor vehicle is woken up and the residual voltage Vr presents and maintains a voltage value V. .

[0041] In the second example of the timing diagram of [Fig. 3], at time t5, an action is again performed on the control means, while the value of the voltage Vr is in the interval 10, and there is a press on the brake pedal. From then on, the value of the residual voltage Vr increases again within the interval 10 and the method for starting an electric powertrain according to the invention will trigger a time delay for the conditional sending of an actuation authorization signal 32 of the electric powertrain, and this, until a time t6 where the value of the residual voltage Vr leaves the upper part of the interval 10. At this time, the method for starting an electric powertrain according to the invention allows a conditional sending of an activation authorization signal 32 of the electric powertrain. The activation authorization signal 32 then corresponds to an “authorized” state, because the brake pedal is pressed. Assuming that the last two conditions seen previously are also fulfilled (gear lever in a Parking or Neutral position and no fault in the traction chain), the residual voltage Vr continues to increase up to a traction voltage value Vt where the residual voltage Vr becomes a traction voltage, of the order of 400 V for example. The electric motor vehicle is then completely awake and operational.

[0042] It appears that the implementation of the method for starting an electric powertrain according to the invention as just described, makes it possible to achieve a time delay for the activation in the interval 10 of value of the residual voltage Vr, the concomitant start request is secured, and it is not possible to put the electrical machine(s) of the powertrain into protection, thus preventing a long wait for the customer for the machine to be rehabilitated. This makes it possible to maintain the continuous availability of the powertrain since no rehabilitation is necessary and therefore to avoid the feeling of "failure" that the driver will otherwise perceive.

[0043] 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.

[0044] 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 they have been specifically described only 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 devoid of sense.

Claims

Claims

1. Method for starting a motor vehicle comprising an electric powertrain comprising at least one electric traction machine, a traction battery and a high-voltage network electrically connecting the electric machine to the traction battery, as well as a starting control means (1), characterized in that, following a preliminary step of receiving a start request signal (12) from the start control means, the method comprises the following steps: • Measurement of a residual voltage value Vr in the high-voltage network; • If the residual voltage value Vr thus measured is within an interval delimited by two predetermined voltage threshold values ​​V sb and Vsh, delaying the sending of a start authorization signal (32) of the electric powertrain;and, • As soon as the time delay has elapsed, conditional sending of the start authorization signal for the electric powertrain.;

2. Method according to claim 1, characterized in that the voltage threshold value Vsb is less than or equal to the voltage threshold value Vsh.

3. Method according to one of claims 1 to 2, characterized in that the voltage threshold values ​​Vsb and Vsh are between 0 V and 12 V.

4. Method according to one of claims 1 to 3, characterized in that the voltage threshold value Vsb is approximately 4 V.

5. Method according to one of claims 1 to 4, characterized in that the voltage threshold value Vsh is approximately 8 V.

6. Method according to one of claims 1 to 5, characterized in that the time delay is of a predetermined duration t, in particular between 3 and 5 seconds.

7. Method according to one of claims 1 to 5, characterized in that the time delay duration t lasts as long as the value of the residual voltage Vr remains within the interval delimited by the two voltage threshold values ​​V sb Vsh*

8. Powertrain for a motor vehicle comprising a

9. electric traction motor, characterized in that it further comprises a computer (2, 3) arranged so as to implement the method according to one of claims 1 to 7. Motor vehicle, characterized in that it comprises a powertrain according to claim 8.

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