EP2643842B1

EP2643842B1 - Method for piloting a relay on-board an automotive vehicle

Info

Publication number: EP2643842B1
Application number: EP10819725.2A
Authority: EP
Inventors: Roger Schmidt; Gilles Goumy
Original assignee: Renault Trucks SAS
Current assignee: Renault Trucks SAS
Priority date: 2010-11-26
Filing date: 2010-11-26
Publication date: 2014-11-19
Anticipated expiration: 2030-11-26
Also published as: EP2643842A1; WO2012069869A1

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a method for piloting a least one electromagnetic relay on-board an automotive vehicle, comprising electric power regulation means adapted to control the holding power available for the relay.

BACKGROUND OF THE INVENTION

Automotive vehicle are usually equipped with several electromagnetic relays, which are operated to open or close electrical circuits feeding various functions of the vehicle with electrical current. These relays are most often of the "normally open" type, and they are operated by electrical currents in order to close them and hold them in closed configuration to allow passage of electrical current. As the number of relays of a vehicle is quite high, it induces a high electrical energy consumption.
Document DE202006013422 discloses a method for piloting at least one electromagnetic relay according to the preamble of claim 1.
To reduce the electrical consumption of the relays, it is known from JP-A-2000/090797 to pilot relays with Pulse Width Modulation (PWM). This method consists in feeding the relays by pulses of current at a determined frequency instead of feeding the relays with a constant continuous current. PWM piloting reduces the electrical consumption of the relays and spares electrical energy. PWM piloting is one way of regulating the electric power of the pilot current fed to the relay.
Even if this method allows to save electric energy, it is not adapted to the various operating configurations of an automotive vehicle. When the engine of the vehicle is shut down, no more electrical energy is produced, then if a large number of relays are to be maintained closed, the energy consumption goes on and provokes a potentially harmful discharge of the electrical battery. In other operating configurations of the vehicle, the relays may need relatively high holding power in case vibrations or shocks occur while the vehicle moves.

SUMMARY

This invention aims at proposing a new method for piloting a relay on-board an automotive vehicle, which allows to adapt the electrical consumptions of relays on the basis of various operating configurations of the vehicle in order to save electrical energy and prevent damages on the battery of the vehicle.
To this end, the invention concerns a method for piloting at least one relay on-board an automotive vehicle comprising electric power regulation means adapted to control the holding power available for the relay. This method is characterized in that the electric power regulation means adjust the holding power to at least two intermediate and distinct levels inferior to a maximum value corresponding to the switching power of the relay, and superior to a threshold low value, on the basis of at least one parameter representing the state of the vehicle.
Thanks to the invention, the holding power of the relay can be adapted to the state of the vehicle. The invention allows to spare electrical energy and to prevent discharge of the battery of the vehicle when high holding powers are not needed.
According to further aspects of the invention which are advantageous but not compulsory, such a method may incorporate one or several of the following features:

At least one of the two intermediate levels is adjustable.
Both intermediate levels are adjustable.
A first intermediate level corresponds to a moving state of the vehicle, whereas a second intermediate level corresponds to a stopped state of the vehicle and whereas the holding power value of the first level is superior to the holding power value of the second level.
Each relay of the vehicle is piloted with the same intermediate level holding power values.
different relays of the vehicle are piloted with different intermediate levels of holding power determined on the basis of safety and/or operability criteria.
The first intermediate level is set to a value comprised between 75% and 90% of the switching power of the relay.
The second intermediate level is set to a value comprised between 50% and 75% of the switching power of the relay.
The holding power of the relay is adjusted on the basis of the operation state of the engine of the vehicle, and/or on the basis of the state of charge of a vehicle battery, and/or on the basis of the temperature of the relay or of its immediate surroundings.
The holding power of the relay is adjusted on the basis of the detection of the amplitude of vibrations occurring in the vehicle.
The electric power regulation means comprise voltage regulating means.
The electric power regulation means comprise pulse width modulation means.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in correspondence with the annexed figures and as an illustrative example, without restricting the objet of the invention. In the annexed figures:

Figure 1 is a schematic representation of an electric circuit of a vehicle with which the method of the invention can be implemented;
Figure 2 is a time versus voltage chart of a pulse width modulation in one method according to the invention;
Figure 3 is a time versus holding power chart representing different holding power levels of a relay with which one method according to the invention can be implemented.

DETAILLED DESCRIPTION OF SOME EMBODIMENTS

An automotive vehicle comprises various electrically powered equipments such as a windshield wiper system 10, an air conditioning system 20 and a light system 30. These systems are schematically represented on figure 1 and comprise electromagnetic relays adapted to switch on or switch off various functions. Electromagnetic relays may use an electromagnet to operate a switching mechanism mechanically. For the understanding of the figures, one relay is represented in each of systems 10, 20 and 30 with the respective references 101, 201 and 301.
Relays 101, 201 and 301 are adapted to open or close not shown electrical circuits in order to operate various functions such as activation of the windshield wipers, switching on of air conditioning modes or switching on of some lights of the vehicle. Although the relays could be of the "normally closed" type, it will be hereinafter assumed that they are of the "normally open" type, thereby requiring some holding power to be maintained in their closed state which is their forced state, but virtually no power to be maintained in their open state, which is their relaxed state. Switching of a relay from its relaxed state to its forced state requires a so-called switching pilot current having a switching power.
Each of the relays of the vehicle is fed with electrical pilot current by a power unit 2 of the vehicle. Power unit 2 comprises a battery 4 and an electric power regulation unit. The power regulation unit controls the amount of power of the pilot current. It can therefore control the switching of the relay and its holding in its forced state. The relays can be controlled by an alternate current, but it will be hereinafter considered that the relays are controlled by a direct pilot current. The power regulation unit controls the voltage and/or the intensity of the pilot current. For example, it will be a voltage regulating unit. The voltage regulating unit could simply deliver a continuous direct current at carious intermediate levels of voltage.
In the shown embodiment, the electric power regulating unit is embodied as a pulse width modulation unit 6, hereafter named PWM unit 6. PWM unit 6 is connected to battery 4 by an electrical feeding line 61.
PWM unit 6 is adapted to feed each of relays 101, 201 and 301 with respective electrical currents C101, C201 and C301 generated by PWM unit 6 on the basis of the operations to be realized by systems 10, 20 and 30.
The electrical currents provided to the relays may show a form as represented schematically on figure 2. The currents comprise pulses 80 of a determined width W80 separated by intervals 82 which have a width W82. The term "width" is understood with respect to the graphical representation of the current. Basically, it denotes a time duration. This profile determines a duty cycle DC, determined by the following formula: $DC = \frac{W 80}{W 80 + W 82}$

The calculation of duty cycle DC permits to determine the effective power of the pilot current provided to the relay, which equals the nominal power multiplied by duty cycle DC. The nominal power corresponds to the power which would be absorbed from battery 4 if each current comprised no intervals 82 and were a continuous current.
In fact, pulses 80 have a nominal voltage VN, and the width and periodicity of pulses 80 determine an effective power which is inferior to the nominal power. In a steady state, when the pilot current is controlled to maintain the relay in its forced state, the effective power corresponds to the holding power of each relay, which determines the "force" with which each relay is maintained in its closed position. By determining widths W80 of pulses 80 and widths W82 of intervals 82, one can adapt the holding power of the relays in order to save electrical energy.
The operation of relay 101 is hereafter described.
When relay 101 has to be switched, i.e. in the exemplified case to its closed position, electrical current C101 is provided with a switching power, here a closing power Pc, which corresponds to the nominal power of current C101 and to the highest portion of the curve on figure 3. At this instant, current C101 is for example a continuous current pulse with no intervals because relay 101 has to be closed firmly and as fast as possible.
Once closed, relay 101 is maintained in closed position by a holding power Ph which is inferior to closing power Pc. Holding power Ph can be set to two different intermediate levels of holding power Ph1 and Ph2.
Ph1 corresponds for example to the holding power provided to relay 101 when the engine of the vehicle is running, because vibrations may occur and loosen the closing contact of relay 101. This first intermediate level Ph1 is set by PWM unit 6 by creating intervals 82 in current C101. This is done by electronic components in a way well known by those skilled in the art. First intermediate level Ph1 has a holding power which is for example comprised between 75% and 90% of the value of closing power Pc of relay 101.
When the engine of the vehicle is shut down, it can be considered that relay 101 is not affected by vibrations. It needs therefore less holding power than if vibrations where still occurring. One can therefore reduce power consumption of relay 101 by reducing the effective power of current C101. PWM unit 6 sets holding power of relay 101 to a second intermediate level Ph2, which is inferior to first intermediate level Ph1. Second intermediate level Ph2 has for example a holding power comprised between 50% and 75% of the value of closing power Pc of relay 101.
As represented on figure 3, at a time t0 of the operations of relay 101, the power provided to relay 101 equals 100% of the nominal power of relay 101, which corresponds to the closing power Pc. After a predetermined period of time allowing to be sure that relay 101 is properly closed, the holding power can be reduced to first intermediate level Ph1 at a time t1.
At a time t2, the engine of the vehicle is shut down. This event is detected by an engine operation sensor 64 adapted to detect the operation phases of the engine. For instance, this sensor can be an engine speed sensor, or any other mean adapted to detect the operating state of the engine. Sensor 64 is adapted to transmit to PWM unit 6 information about the operation state of the engine thanks to an electronic signal S64. The electronic signal S64 representative of the operating state of the engine can be delivered by an electronic control unit based on a number of data, for example the data coming from an engine speed sensor.
Once it has been determined that the engine is shut down, the holding power of relay 101 is reduced from first intermediate level Ph1 to second intermediate level Ph2, by widening intervals 82 or by reducing width W80 of pulses 80.
According to the invention, determination of which intermediate level of pilot current is to be fed to the relay can be made on the basis of the engine operating state and/or on the basis of other parameters. For example, it can be taken into account the state of charge of the battery 4, and/or of the temperature of the relay or of its immediate surroundings. Indeed, vehicles often comprise a so-called electrical junction box or electrical centre in which can be found a number of relays. Such electric junction box is often a relatively closed enclosure where the temperature is susceptible to rise. Therefore, if a temperature sensor is provided in such an enclosure, it can be used to determine that at least a number of relays should be fed with a reduced holding power to limit the temperature increase in the box.
Preferably, the determination of holding power for each relay will be determined on the basis of a combination of parameters.
The method of the invention has been described for relay 101, but can also be implemented with relays 201 and 301, and with all the non represented relays the vehicle is equipped with.
According to another aspect of the invention, at least one of the intermediate levels Ph1 and Ph2 may be adjustable on the basis of the above mentioned parameters or of other parameters.
For instance, the vehicle may be equipped with a vibration sensor 66, adapted to measure vibrations at a given place in the structure of the vehicle and to transmit the results to PWM unit 6. This data may be transmitted thanks to an electronic signal S66. The vehicle can comprise various sensors of this kind, adapted to measure vibrations at different places in the structure of the vehicle. For instance, in case the vehicle moves on a damaged road, vibrations amplitudes are higher than if the vehicle moves on a good road, and relays need more holding power to be maintained in closed position. PWM unit 6 may then adapt first intermediate level to a value which prevents relays from opening, on the basis of the measures of vibration sensor 66.
PWM unit 6 may also be connected to a speed or acceleration sensor 68 which is adapted to transmit to PWM unit 6 data about the speed or the acceleration of the vehicle, in order to adapt first intermediate level Ph1 to the speed and/or the acceleration of the vehicle.
As mentioned above, the piloting of relays may be determined on the basis of the temperature of the relays. As represented on figure 1, each of relays 101, 201 and 301 may be equipped with a respective temperature sensor 111, 211 and 311 adapted to measure the temperature of the electronic component included in relays 101, 201 and 301. Temperature sensors 111, 211 and 311 are adapted to transmit to PWM unit 6 data concerning the temperature of the relays thanks to respective electronic signals S111, S211 and S311. The higher the effective power of a relay, the more the temperature of its electronic components rises. In case the temperature of a relay reaches a critical temperature, damages can occur, and then a failure of a subsystem of the vehicle can occur. In case a critical temperature, which depends on the type of electronic component used, is approached, this is detected by PWM unit 6 thanks to the temperature sensors and the holding power of the relay which approaches its critical temperature can be reduced, if possible.
For instance, in case relay 101 approaches a critical temperature, its holding power cannot be reduced in a too large proportion because relay 101 is used in windshield wiper system 10 of the vehicle which is a system involved with the safety of the passengers.
If relay 201 approaches its critical temperature, its holding power can be reduced, because the operating of air conditioning system 20 is less important for the safety of the passengers of the vehicle.
Preferably, in every use situation of the vehicle when the key is on and battery 4 provides electrical current, regardless of the operation state of the engine, the vibrations of the structure, the temperature or the safety-related importance, the holding power of all the relays of the vehicle is maintained to a value superior to a minimal holding power value Pmin.

Claims

Method for piloting at least one electromagnetic relay (101, 201, 301) on-board an automotive vehicle, comprising electric power regulation means (6) adapted to control the holding power (Ph) available for the relay (101, 201, 301), characterized in that the electric power regulation means (6) adjust the holding power (Ph) to at least two intermediate and distinct levels (Ph1, Ph2) inferior to a maximal value corresponding to the switching power (Pc) of the relay, and superior to a threshold low value (Pmin), on the basis of at least one parameter (S64) representing the state of the vehicle.
Method according to claim 1, wherein at least one of the two intermediate levels (Ph1, Ph2) is adjustable.
Method according to claim 2, wherein both intermediate levels (Ph1, Ph2) are adjustable.
Method according to one of the previous claims, wherein a first intermediate level (Ph1) corresponds to a moving state of the vehicle, wherein a second intermediate level (Ph2) corresponds to a stopped state of the vehicle and wherein the holding power value (Ph1) of the first level is superior to the holding power value (Ph2) of the second level.
Method according to one of the previous claims, wherein each relay (101, 201, 301) of the vehicle is piloted with the same intermediate level holding power values (Ph1, Ph2).
Method according to one of claims 1 to 4, wherein different relays (101, 201, 301) of the vehicle are piloted with different intermediate levels of holding power (Ph1, Ph2), determined on the basis of safety and/or operability criteria.
Method according to one of the previous claims, wherein the first intermediate level is set to a value (Ph1) comprised between 75% and 90 % of the switching power (Pc) of the relay (101, 201, 301).
Method according to one of the previous claims, wherein the second intermediate level is set to a value (Ph2) comprised between 50 % and 90 % of the switching power (Pc) of the relay (101, 201, 301).
Method according to one of the previous claims, wherein the holding power (Ph) of the relay (101, 201, 301) is adjusted on the basis of the operation state (S64) of the engine of the vehicle.
Method according to one of the previous claims, wherein the holding power (Ph) of the relay (101, 201, 301) is adjusted on the basis of the state of charge of a vehicle battery.
Method according to one of the previous claims, wherein the holding power (Ph) of the relay (101, 201, 301) is adjusted on the basis of the temperature of the relay or of its immediate surroundings.
Method according to one of the previous claims, wherein the holding power (Ph) of the relay (101, 201, 301) is adjusted on the basis of the detection (S66) of the amplitude of vibrations occurring in the vehicle.
Method according to one of the previous claims, wherein the electric power regulation means comprise voltage regulating means.
Method according to one of the previous claims, wherein the electric power regulation means comprise pulse width modulation means.