EP1964255A2

EP1964255A2 - Method for controlling an electromagnetic retarder

Info

Publication number: EP1964255A2
Application number: EP06841954A
Authority: EP
Inventors: Bruno Dessirier; Stéphane Hailly; Serge Newiadomy
Original assignee: Telma SA
Current assignee: Telma SA
Priority date: 2005-12-22
Filing date: 2006-12-15
Publication date: 2008-09-03
Also published as: WO2007080280A2; MX2008008348A; FR2895596A1; CN101322308A; FR2895596B1; BRPI0618537A2; US20090247354A1; WO2007080280A3

Abstract

The invention relates to a method for controlling an electromagnetic retarder comprising a current generator into which an excitation current is injected. The inventive method consists in determining a maximum allowable intensity (Im) of the excitation current to be injected into the stator primary coils of the retarder which includes a shaft bearing secondary windings and field coils which are supplied by the secondary windings, said primary coils and secondary windings forming the generator. The retarder includes a jacket inside which the field coils generate Foucault currents and a circuit for the liquid cooling of said jacket. More specifically, the invention consists in determining the maximum allowable intensity in real time, such as to reach a critical temperature of the cylindrical jacket and determining said critical temperature taking account of a temperature value of the coolant. The invention is suitable for retarders that are intended for vehicles such as heavy vehicles.

Description

Method of controlling an electromagnetic retarder

FIELD OF THE INVENTION

The invention relates to a method for controlling an electromagnetic retarder comprising a current generator.

The invention applies to a retarder capable of generating a deceleration resistant torque on a main or secondary transmission shaft of a vehicle that it equips, when this retarder is actuated.

STATE OF THE ART

Such an electromagnetic retarder comprises a rotary shaft which is coupled to the main or secondary drive shaft of the vehicle to exert on it the retarding resisting torque to assist in particular the braking of the vehicle.

The deceleration is generated with inductor coils fed with direct current to produce a magnetic field in a metal part made of ferromagnetic material, in order to reveal eddy currents in this metal part.

The inductor coils may be fixed to cooperate with at least one metal part of movable ferromagnetic material having a general appearance of disk rigidly secured to the rotary shaft.

In this case, these inductive coils are generally oriented parallel to the axis of rotation and arranged around this axis, vis-à-vis the disc, being secured to a fixed flange. Two successive inductive coils are electrically powered to generate magnetic fields of opposite directions. When these inductive coils are electrically powered, the eddy currents that they generate in the disc are opposed by their effects to the cause that gave birth to them, which produces a resistant torque on the disc and thus on the rotating shaft, to slow down the vehicle.

In this embodiment, the inductor coils are electrically powered by a current from the electrical network of the vehicle, that is to say for example from a battery of the vehicle. But to increase the performance of the retarder, we use a design in which a current generator is integrated in the retarder.

Thus, according to another known design of patent documents EP0331559 and FR1467310, the electrical supply of the inductor coils is provided by a generator comprising stator primary coils fed by the vehicle network, and rotor secondary coils integral with the rotary shaft. .

The inductor coils are then integral with the rotary shaft by being radially projecting, so that they rotate with the rotary shaft to generate a magnetic field ι in a fixed cylindrical jacket which surrounds them.

A rectifier such as a diode bridge rectifier is interposed between the secondary rotor windings of the generator and the inductor coils, for converting the alternating current delivered by the secondary windings of the generator into DC power supply of the inductor coils.

Two consecutive radial inductor coils around the axis of rotation generate magnetic fields of opposite directions, one generating a centrifugally oriented field, the other a centripetally oriented field.

In operation, the power supply of the primary coils allows the generator to produce the supply current of the inductor coils, which gives rise to eddy currents in the coil. fixed cylindrical jacket, to generate a resistant torque on the rotating shaft, which slows down the vehicle.

In order to reduce the weight and further increase the performance of such a gearbox, it is advantageous to couple it to the vehicle shaft via a speed multiplier, in accordance with the solution adopted in EP1527509.

The speed of rotation of the retarder shaft is then overdrive relative to the rotational speed of the transmission shaft to which it is coupled. This arrangement makes it possible to significantly increase the electric power delivered by the generator, and therefore the power of the retarder.

OBJECT OF THE INVENTION

The object of the invention is a method of determining the maximum allowable current of the excitation current of the primary coils of an electromagnetic retarder to improve its performance and reliability.

To this end, the subject of the invention is a method for determining, in a control box, a maximum allowable intensity of an excitation current to be injected in stator primary coils of an electromagnetic retarder comprising a rotary shaft bearing secondary windings and induction coils energized electrically by these secondary windings, the primary coils and the secondary coils forming a generator, this retarder comprising a fixed cylindrical jacket surrounding the inductor coils and in which the inductor coils generate eddy currents, and a circuit fluid circulation cooling system of this jacket, which method determines the maximum admissible intensity in real time, so that this maximum admissible intensity corresponds to at a critical temperature of the cylindrical jacket, and to determine this critical temperature by taking into account a temperature value of the coolant. Taking into account the temperature of the coolant makes it possible to increase the value of the critical temperature of the fixed cylindrical jacket, in particular when the coolant has a temperature which is low. Increasing criticism jacket temperature increases all the intensity of the excitation current, and hence, the ^"braking torque generated by the retarder.

The invention also relates to a method as defined above, in which the temperature of the cooling liquid corresponds to a measurement value resulting from a temperature probe located at the outlet of the cooling circuit.

The invention also relates to a method as defined above, of taking into account the flow of the cooling liquid to determine the critical temperature.

The invention also relates to a method as defined above, in which the maximum admissible intensity is determined in the control box from tables of digital values stored in this control box, these tables comprising representative values of the current maximum permissible for different operating conditions. The invention also relates to a method as defined above, consisting in determining the representative value of the coolant flow rate from the engine speed of a vehicle engine and a characteristic abacus of a driven water pump. by this heat engine, this water pump causing the circulation of the coolant. The invention also relates to a method as defined above, in which the significant value of the engine speed is derived from data transmitted by a CAN bus.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and with reference to the accompanying drawings which illustrate an embodiment thereof by way of non-limiting example. Figure 1 is an overall view with a local tear of an electromagnetic retarder to which the invention applies;

FIG. 2 is a schematic representation of the electrical components of the retarder for which the method according to the invention is intended;

FIG. 3 is a curve representative of the intensity of the excitation current as a function of the speed of rotation of the rotary shaft in order to obtain a current flowing in the inductor coils having a constant intensity;

FIG. 4 is a curve representative of the critical temperature of the cylindrical jacket as a function of the coolant flow rate;

FIG. 5 is a graph representative of the increase of the critical temperature as a function of the temperature of the coolant;

FIG. 6 comprises two curves of current intensity injected into the primary coils as a function of the temperature of the cylindrical jacket for two temperatures of the coolant.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In Figure 1, the electromagnetic retarder

1 comprises a main casing 2 of generally cylindrical shape having a first end closed by a cover 3, and a second end closed by a coupling part 4 by which this retarder 1 is attached to a gearbox case either directly or indirectly, here via a gear multiplier marked by 6.

This casing 2, which is fixed, contains a rotary shaft 7 which is coupled to a transmission shaft not visible in the figure, such as a main shaft for transmitting to the wheels of the vehicle, or secondary such as a secondary output shaft. of the gearbox via the speed multiplier 6. In a region corresponding to the interior of the cover 3 is located a current generator which comprises fixed or statoric primary coils 8 which surround rotor secondary coils, integral with the rotary shaft 7.

These secondary windings are symbolically represented in FIG. 2 and marked by reference numeral 5. These secondary windings 5 here comprise three separate windings 5A, 5B and 5C for delivering a three-phase alternating current having a frequency conditioned by the speed of rotation of the shaft. rotating 7.

A fixed inner liner 9 of cylindrical general shape is mounted in the main housing 2 being spaced radially slightly from the outer wall of the main housing 2 to define an intermediate space 10, substantially cylindrical, in which circulates a coolant of this jacket 9.

This main casing, which also has a generally cylindrical shape, is provided with a coolant intake duct 11 in the space 10 and a discharge duct 12 of the coolant out of this space 10.

The cooling circuit of the retarder can be connected in series with the cooling circuit of the engine of the vehicle that the retarder team. In this case, the input 11 is connected to the output of the heat engine, the output 12 being connected to the input of a cooling radiator of this circuit. This jacket 9 surrounds several induction coils 13 which are carried by a rotor 14 rigidly secured to the rotary shaft 7. Each induction coil 13 is oriented to generate a radial magnetic field, while having a generally oblong shape extending parallel to the tree 7.

In known manner, the liner 9 and the body of the rotor 14 are made of ferromagnetic material. Here the casing is a moldable aluminum-based part and seals intervene between the casing and the liner 9, the lid 3 and the part 4 are perforated.

The inductor coils 13 are electrically powered by the rotor secondary coils 5 of the generator via a rectifier bridge carried by the rotary shaft 7. This rectifier bridge may be that which is indicated by 15 in FIG. 2, and which comprises six 15A diodes. -15F, for rectifying the three-phase alternating current from the secondary windings 5A-5C in direct current. This bridge rectifier can also be of another type, for example being formed from MOSFET type transistors.

As can be seen in FIG. 1, the rotor 14 carrying the induction coils 13 has a general shape of a hollow cylinder connected to the rotary shaft 7 by radial arms 16. This rotor 14 thus defines an annular internal space situated around the shaft 7, this internal space being ventilated by an axial fan 17 located substantially at the junction of the lid 3 with the casing 2. A radial fan 18 is located at the opposite end of the casing 2 to evacuate the air introduced by the fan 17.

The biasing of the retarder consists in supplying the primary coils 8 with an excitation current coming from the electrical network of the vehicle and in particular from the battery so that the generator delivers a current at its secondary coils 5. This current delivered by the generator then feeds the inductor coils 13 so as to generate eddy currents in the fixed cylindrical jacket 9 to produce a resistive torque ensuring the slowing down of the vehicle. The excitation current is injected into the primary coils 8 by means of a control box described hereinafter.

The electric power delivered by the secondary windings 5 of the generator is greater than the electrical power supply of the primary coils 8, since it is the result of the magnetic field of the primary coils 8 and the work provided by the rotary shaft. In the embodiment of Figure 1, the shaft 7 of the retarder is connected to the transmission shaft of the vehicle wheels via the multiplier 6 acting on a secondary shaft of the gearbox connected to the main shaft of the -this.

This retarder comprises a control unit 19 represented in FIG. 2, which is interposed for example between a vehicle power supply source, and the primary coils 8. In the example of FIG. 2, the control unit 19 and the primary coils 8 are connected in series between a mass M of the vehicle and a battery supply Batt of the vehicle battery. As shown in this figure, a diode D is mounted across the primary coils 8 so as to prevent the flow of a reverse current in the primary coils.

The control unit 19 of the retarder is an electronic box comprising for example an ASIC type logic circuit operating at 5V, and / or a power control circuit capable of handling high intensity currents.

This control unit 19 comprises an input capable of receiving a control signal from the retarder, this signal being representative of a level of retarding torque requested from the retarder. The control unit 19 determines in real time an intensity The maximum permissible Im for the current to be injected in the primary coils 8. It then defines the value of the intensity Ie of the excitation current, starting from the maximum intensity Im and the value taken by the control signal.

The maximum permissible intensity Im of the excitation current Ie to be injected into the primary coils is determined in real time in the control box 19 from data and measurements representative of the temperature of the coolant at the outlet 12 , denoted Tr, and the flow rate of the coolant, noted D.

The intensity Im is a threshold value beyond which the temperature of the cylindrical liner 9 is too high and provokes the boiling of the cooling liquid, even if this circuit is capable of evacuating the heating power resulting from the currents. Foucault circulating in this shirt.

If the temperature of the jacket is located beyond the critical temperature Tc, the coolant boils, causing short-term failure of the electromagnetic retarder.

The temperature of the cylindrical jacket 9 depends mainly on the intensity of the eddy currents flowing in the cylindrical jacket 9. This is directly related to the intensity of the current, denoted If, which flows in the inductor coils 13. This current If itself has an intensity depending on the rotational speed Na of the rotary shaft 7, and the intensity of the excitation current Ie. In other words, for a constant intensity of the current If flowing in the inductor coils 13, the excitation current Ie injected into the primary coils 8 must decrease when the rotation speed Na of the rotary shaft 7 increases, as represented schematically in FIG.

The rotational speed Na of the rotary shaft 7 can come from a rotation speed sensor equipping the retarder, or be deduced from data available on a CAN data bus of the vehicle to which the housing 19 is connected. In this case, the factor of the speed multiplier 6 is stored in the control box 19 to enable the determination of the speed Na from the data of the CAN bus.

FIG. 4 is a graph representative of the critical temperature Tc (105 °) as a function of the flow rate D of coolant, for a coolant having a temperature Tr equal to one hundred and five degrees. As this graph shows, the higher the flow rate D, the higher the critical temperature Tc can be important.

The flow rate D of the coolant depends on the speed of rotation of a water pump driven by the engine of the vehicle, and which causes the circulation of the coolant. This flow rate results from the rotation speed of the heat engine, denoted Nt, and an abacus representative of the characteristic of this pump. Advantageously, the control unit 19 retrieves on the CAN bus the rotational speed Nt to determine the flow rate D from the pump chart stored in this control box 19.

The critical temperature Tc is in fact also dependent on the temperature Tr of the coolant: it can be even higher than the temperature Tr of the coolant is low, and without risk of boiling of the liquid of cooling. FIG. 5 is a graph representative of the correction C (Tr) to be applied at the temperature Tc (105 °) of the graph of FIG. 4 to take into account the temperature Tr of the cooling liquid at the outlet 12 of the cooling circuit. As can be seen in this graph, when the temperature Tr is eighty-five degrees, the critical temperature value Tc from the graph of FIG. 4 can be increased by forty-five degrees. five degrees. The correction C (Tr) to be applied is zero when Tr is greater than or equal to one hundred and five degrees.

The use of the data represented in the graphs of FIGS. 4 and 5 makes it possible to determine the critical temperature Tc as a function of the flow rate D, that is to say the rotation speed Nt of the heat engine and the temperature Tr of the liquid of cooling at the outlet 12 of the cooling circuit.

To do this, digital data corresponding to the graphs of FIGS. 4 and 5 are stored in the control box. The determination of Tc consists first of all in reading in a first table, from the flow D, or the rotation speed Nt of the heat engine, the critical temperature per cent-five degrees: Tc (105 °). Then, the fix C (Tr) to be applied is read in another data table corresponding to Figure 5, and is added to the temperature Tc (105 °). We thus have Tc = Tc (105 °) + C (Tr).

The determination of the maximum permissible intensity Im consists in first identifying a threshold value of the current If flowing in the inductive coils beyond which the heating power generated by the eddy currents resulting from If would cause a rise in temperature of the cylindrical jacket beyond the critical temperature Tc.

From this threshold value of the current If flowing in the inductor coils, and the rotation speed Na of the rotary shaft 7, the value of the maximum intensity Im of the excitation current is read in another data table. This other data table is representative of the current If as a function of the excitation current Ie and the rotation speed Na of the rotary shaft 7.

The corrective C (Tr) makes it possible to increase the operating temperature of the cylindrical jacket, by an additional forty degrees in the most favorable cases. This increase in temperature allows a significant increase in the intensity Im of the injected current, and therefore the retarding torque that the retarder is able to provide.

Fig. 6 is a graph showing the maximum allowable current for the excitation current as a function of the temperature of the jacket. The maximum admissible intensity is represented by a curve marked by Im (105 °) in the case of a coolant having a temperature Tr of one hundred and five degrees, and is represented by another curve marked by Im (85 °) ) corresponding to a case in which the coolant temperature is eighty-five degrees, thereby increasing the critical temperature Tc by forty degrees. A forty-degree increase in the critical temperature Tc may correspond to an increase in the maximum intensity of up to seventy-five percent.

In the embodiment presented above, the data is stored as independent data tables, but this data can also be stored in the control box 19 in the form of one or more crossed dynamic tables.

This facilitates the implementation of the piloting method according to the invention while providing flexibility allowing adaptability to different contexts of use.

Claims

A method for determining, in a control box, a maximum allowable intensity (Im) of an excitation current (Ie) to be injected into stator primary coils (8) of an electromagnetic resistor (1) comprising a shaft rotary electrode (7) carrying secondary windings (5) and induction coils (13) electrically powered by these secondary windings (5), the primary coils (8) and the secondary coils (5) forming a generator, this retarder (1) comprising a fixed cylindrical jacket (9) surrounding the inductor coils (13) and in which the inductor coils (13) generate eddy currents, and a liquid-circulating cooling circuit of this jacket, which method comprises determining the maximum permissible intensity

(Im) in real time so that this maximum admissible intensity corresponds to a critical temperature (Tc) of the cylindrical jacket (9), and to determine this critical temperature (Tc) taking into account a temperature value (Tr ) coolant.

2. The method of claim 1, wherein the temperature (Tr) of the coolant corresponds to a measurement value from a temperature sensor at the outlet (12) of the cooling circuit.

3. Method according to claim 1 or 2, comprising taking into account the flow (D) of the coolant to determine the critical temperature (Tc).

4. Method according to one of the preceding claims, wherein the maximum intensity (Im) admissible is determined in the control box (19) from tables of digital values stored in this control box (19), these tables comprising values representative of the maximum current (Im) admissible for different operating conditions.

5. Method according to one of the preceding claims, of determining the representative value of the flow rate (D) of the coolant from the speed (Nt) of a vehicle engine and a characteristic chart of a pump. water driven by this engine, this water pump causing the circulation of coolant.

6. The method of claim 5, wherein the significant value of the engine speed is derived from data transmitted by a CAJSF bus.