EP2499393A1

EP2499393A1 - Method and system for coupling an electrical machine to the running gear of a vehicle, notably a hybrid automotive vehicle

Info

Publication number: EP2499393A1
Application number: EP10798161A
Authority: EP
Inventors: Eric Schaeffer; Florian Galinaud
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2009-11-10
Filing date: 2010-11-03
Publication date: 2012-09-19
Also published as: WO2011058264A1; FR2952416A1; FR2952416B1

Abstract

In order to couple an electrical machine to the driving wheels of a vehicle when the vehicle is at a standstill, the method comprises two stages (54, 55) which are activated in parallel at the instigation of a coupling request: - a stage (54) of translationally bringing two clutch dogs closer together along a common axis of rotation, an upstream dog rotating as one with the electrical machine and a downstream dog rotating as one with the driving wheels; and a stage (55) of slaving the torque of the electrical machine to a set dog-coupling torque which starts at a zero value at the moment of the coupling request and which progressively increases, remaining below an electrical machine start-up value for long enough for the two clutch dogs to be brought translationally closer together into a position which the tops of the teeth of the two clutch dogs are coplanar, and exceeding said start-up value after said sufficient duration has elapsed.

Description

"Method and system for coupling an electric machine to a running gear of a vehicle, in particular a hybrid motor vehicle". The invention relates to a method and a coupling system of an electric machine on a running gear of a vehicle, in particular of a hybrid motor vehicle, when the vehicle is stationary.

The method and system are particularly suited to a hybrid vehicle that also uses a heat engine, so as to contribute the electric machine to the traction of the vehicle.

The document FR2723553 discloses, for example, a motor vehicle comprising a selective control system for operating separately or simultaneously the electric and thermal traction chains.

Document US5403244 discloses a direct transmission coupling electric vehicle power train using synchronization means based on friction plates of the clutch disc type. Couplings of the clutch type are generators of energy loss.

To increase the yield, the state of the art is geared towards jaw-type couplings. Thus the document FR20905438 describes a driving method implementing two jaw in which a force exerted in translation on one of the jaw to approach the other dog, is modulated according to different phases of approach.

An object of the present invention is to achieve a simplified coupling without clutch which does not require modulating a translational force, particularly when the vehicle is stationary.

To achieve this object, the invention relates to a method of coupling an electric machine with the wheels of a vehicle running gear when the vehicle is stationary, comprising two steps activated in parallel from a coupling request:

a step of approaching in translation of two claws along a common axis of rotation, an upstream clutch being integral in rotation with the electric machine and a downstream clutch being integral in rotation with the wheels; and

a torque control step of the electric machine on a torque linkage setpoint which starts from a zero value at a moment of the coupling request and which gradually increases so as to remain lower than a setting value of the electric machine for a time sufficient to bring the two claws in translation in a position in which the tooth tops of the two claws are coplanar and to exceed said rotational value beyond said time sufficient to achieve the interconnection.

In particular, the coupling torque setpoint follows a ramp of strictly positive steering coefficient and less than or equal to a drag torque exerted on the upstream clutch divided by said sufficient duration.

More particularly, the steering coefficient is substantially equal to 4 Nm / s.

Advantageously, the method comprises a step of switching the torque interconnection setpoint on a torque setpoint linked to a driver's will when the two jaw claws are detected fully engaged one in the other.

Preferably, the clutch torque setpoint is limited to a maximum value of tooth-to-tooth friction torque of the jaw claws.

The invention also relates to a coupling system of an electric machine with wheels of a running gear of a vehicle when the vehicle is stationary, comprising: an upstream clutch solidarity in rotation of the electric machine, a clutch downstream integral in rotation of the wheels and an actuator arranged to bring the two jaw in translation along a common axis of rotation; and

an electronic device arranged to receive a coupling request, to drive the actuator and to transmit to an electric generator supplying the electric machine, a torque interconnection setpoint which starts from a zero value at a time of receiving the coupling request and which gradually increases so as to remain below a value of rotation of the electric machine for a sufficient time to bring the two jaw in translation in a position in which the toothing of the two jaw teeth are coplanar and exceed said rotation value beyond said time sufficient to achieve the interconnection.

In particular, the electronic device comprises a steer coefficient strictly positive and less than or equal to a drag torque exerted on the upstream clutch divided by said sufficient time so as to follow a ramp to the torque linkage setpoint.

More particularly, the steering coefficient is substantially equal to 4 Nm / s.

Advantageously, the coupling system comprises an end-of-stroke engagement sensor of the claws one into the other, and the electronic device is arranged to switch said interconnection torque setpoint to a torque setpoint linked to a will driver when he receives from the sensor a signal indicating that the two claws are fully engaged one into the other.

Preferably, the electronic device comprises a limitation of the jaw torque setpoint to a maximum value of tooth-to-tooth friction torque of the jaw claws. The invention will be better understood, and other objects, features, details and advantages thereof will become more clearly apparent in the following explanatory description of a particular, currently preferred embodiment of the invention, given only by way of illustrative and non-limiting example, with reference to the accompanying schematic drawings; wherein :

- Figure 1 is a schematic view of a hybrid motor vehicle comprising a coupling system according to the invention;

FIG. 2 is a schematic view of the coupling system according to the invention;

Figure 3 shows the steps of a coupling method according to the invention;

Figures 4a and 4b are curves that show a behavioral evolution of the vehicle when the method according to the invention is implemented.

With reference to FIG. 1, a hybrid-type vehicle 10 comprises a power unit 11 arranged to drive two front wheels 14 of the vehicle 10, and a power unit 12 arranged to drive two rear wheels 44 belonging to one and the same rear drive train. vehicle 10. The powertrain (GMP) 11 comprises in a manner known per se, a heat engine here for purely illustrative purposes at the front of the vehicle. Power train 12 includes an electric machine

42 connected to the wheels 44 by a coupling mechanism

43.

FIG. 2 shows in more detail the power train 12 of FIG. 1. To lighten the figure so as to make it easier to understand, the axis 15 of the electric machine 42 and the axis 16 of the wheels 44 are schematically folded over a same axis 46 above which are simply represented the half-parts of the electric machine 42, the coupling mechanism 43 and a sensible block symbolized the two wheels 44. In the coupling mechanism 43, a dog clutch system comprises an upstream clutch 51 and a downstream clutch 52. The upstream clutch 51 is rotationally integral with a gearbox 45 connected to the output shaft of the electric machine 42. Downstream clutch 52 is integral in rotation with the wheels 44 via a differential mechanism to balance in a manner known per se, the torque between the wheels 44 of the rear axle, especially when they run at different speeds, for example in a turn.

The clutch 51 rotates about the axis 46 at a speed of rotation proportional to or equal to the speed of rotation of the electric machine 42 and transmits a torque proportional to the torque generated by the electric machine 42 while keeping the power supplied by the electric machine 42 to a yield factor near that results from the transmission losses between the electric machine 42 and the clutch 51. The transmission losses in the electric machine 42 and between the electric machine 42 and the clutch 51 can be represented by a drag torque of the upstream part of the dog 51.

The clutch 52 rotates about the axis 46 at a speed of rotation which is a function of the speed of the wheels 44. A torque applied to the dog clutch 52 is transmitted to the wheels 44. When the clutch 52 is disengaged from the clutch 51 as is shown in FIG. 2, the wheels 44 can rotate or not rotate independently of the speed of rotation of the electric machine 42.

The coupling mechanism 43 comprises an actuator 34 arranged to move the clutch 52 in translation along the axis 46. Each of the faces facing the jaws 51 and 52 is provided with teeth and cavities. The teeth of a dog are dimensioned to be housed in the cavities of the other dog. Thus, when the teeth of the clutch 52 face the cavities of the dog 51, as shown in Figure 2, the actuator 34 can engage the clutch 52 in engagement with the clutch 51 so as to make the claws 51 and 52 rotate in rotation about the axis 46. An on-off position sensor 32 is mounted in the coupling mechanism 43 to detect a fully engaged position of the clutch 52 in the clutch. dog 51.

The rotational independence of the jaws 51 and 52 makes the teeth of the dog 52 are not necessarily in front of the cavities of the dog 51 when the actuator 34 moves the dog 52 in translation along the axis 46. A difficulty appears when the vehicle is in a stopped situation, to engage quickly and smoothly jaw as soon as a coupling of the electric machine of the vehicle is requested by the driver. The mechanical architecture of the rear power train system, does not include a clutch and also does not include synchronizer. The only movement of the system is a translation of one or more jaws 51, 52, exerted or activated by the actuator 34. It is recalled that statistically, the failures of engagement in the systems of interconnection often occur because of a high probability of tooth-to-tooth contact of the claws before engaging them.

To remedy this problem, the rear powertrain comprises an electronic device 40 which allows, as we will explain now, a fine control of the torque of the electric machine 42 in combination with a sequential control of the actuator 34 of interconnection in order to reach a fast and smooth jerk that limits the number of failures or stops on dog. The device 40 is connected to the actuator 34 and the sensor 32, respectively by a pin 33 and a pin 31 of the connector of the coupling mechanism 43. The electronic device 40 is connected to the electric machine 42 by an electric generator 41 regulated by current. The electric generator 41 is for example supplied in a known manner from a battery, not shown. The device 40 furthermore comprises electronic digital or analog processing circuits arranged and / or programmed to execute the process steps explained now with reference to FIG.

As long as the vehicle 10 is stationary, the method according to the invention freezes the device 40 in a waiting step 50. FIG. 4a shows the time t on the abscissa and the rotation speeds Ω on the ordinate, respectively represented by the curve 2 for the wheel 44 and by the curve 1 for the electric machine 42. The vehicle being stationary, the curve 2 is constantly at zero. A temporal evolution of the behavior of the power unit 12 during the implementation of the method, is represented in FIG. 4b which carries the time t on the abscissa and various values V on the ordinate, among which a position of the actuator 34 of interconnection, a control signal of the actuator 34 and a torque control setpoint of the electric machine 42, respectively represented at 3, 4, 5 on the curves of FIG. 4b. Initially, the actuator 33 is in a maximum withdrawal position 3 which corresponds to a declutched state of the powertrain 12, the control signal 4 is zero and the torque control setpoint of the electric machine 42 is zero.

The method validates a transition 53 following a request for coupling of the electrical machine, for example from the driver and which results in a signal D emitted to the device 40 as shown in FIG. 2. A first vertical dotted line represents in FIGS. 4a and 4b, the instant at which the transition 53 is validated.

When the method validates the transition 53 following step 50, it activates in parallel a step 54 and a step 55.

In step 54, the method actuates the downstream clutch 52 towards the upstream claw 51. In the embodiment illustrated in FIG. 2, the device 40 sends a signal 4 in step on the pin 33 which puts the actuator 34 in translational movement to engage the clutch 52 in the dog clutch 51. After a relatively short response time, the actuator 34 is set in motion and pushes the clutch 52 of so that the withdrawal position 3 is gradually reduced until stopping at a moment b. The movement in translation stops at a moment b before reaching the total stroke of the clutch when the tops of the teeth of the two claws come into contact, thus preventing the introduction of teeth in the cavities of the opposite dog. The position 3 remains stationary over time until a moment d which allows the teeth of each dog to enter the cavities of the opposite dog.

In step 55, the method applies a torque setpoint along a ramp on the electrical machine 42. In the embodiment illustrated in FIG. 2, the device 40 sends a setpoint C * to the electric generator 41 which follows a ramp of slope sufficiently low that the electric machine 42 remains motionless in rotation until a time c after time b. The value of the slope of the ramp is calibrated so that the torque generated by the electric machine 42 is compensated by the drag torque of the upstream portion of the dog 51, at least for the time necessary to approach the clutch 52 of the dog 51 to put them in contact. The drag torque typically comprises the inertia torque of the electric machine 42 and transmissions to the clutch 51 and the various friction losses on bearings or in gears. The steepness coefficient of the slope is determined so that the generated torque is insufficient to move the electric machine 42 at least up to the instant b, that is to say to adjust the torque without rotating. the dog 51 as long as it is not in contact with the clutch 52. The guiding coefficient can be determined from of tests on a prototype specimen of the powertrain and / or by calculation as a function of the inertial forces, the losses and the powers involved. Sufficient time to bring the two jaw in translation in a position in which the vertices of teeth are in the same plane, is calculated according to the power of the actuator 34 and the distance separating this plane with the maximum retracted position, taking a margin of safety to take into account possible response times. It is also possible to statistically determine this sufficient duration previously on test bench by measuring on a representative number of tests, the time that separates the engagement of the actuator with a collision tooth on tooth in the plane where the tops of teeth of two jaws meet. The steering coefficient is then obtained by dividing the drag torque, measured or calculated, by the sufficient duration mentioned above by reducing it slightly so as to ensure the absence of rotation before contacting. The steering coefficient can also simply be adjusted by means of a real or virtual potentiometer during preliminary tests on a prototype representative of powertrains then produced in series. To give an order of magnitude, a value of the driving coefficient of 4 Nm / s proved to be perfectly suitable on a prototype test implemented by the inventors. This value can vary significantly depending on the type of powertrain implemented. The rotational speed 1 of the electric machine 42 remains zero thereafter although the applied torque continues to increase because it is then compensated by the friction forces tooth on tooth jaw.

At time c, the torque provided by the electric machine 42 is sufficient to start to put the electric machine 42 and the clutch 51 in rotation as represented by the upward slope of the speed 1 on the Figure 4a between instants c and d. The rotation of the clutch 51 from instant c moves the teeth of the dog 51 so as to put the teeth of the dog 51 vis-à-vis with the cavities of the clutch 52. The vis-à-vis teeth of each dog with the cavities of the opposite dog, causes a rapid movement of the actuator 34 and therefore of the clutch 52 in translation so as to put the teeth of the clutch 52 in position 3 of contact with the bottom of the cavities of the clutch 51. It will be noted that the evolution of the position 3 does not need to be measured and it suffices that the position sensor 32 behaves as a limit position detector of the clutch 52 when it is fully engaged. in the clutch 51. The torque ramp applied to the electrical machine 42 between instants a and d is particularly advantageous because the torque value between the instant a, and for safety measure generally beyond the instant b, is weak enough not to put the machine electric in rotation without having to know precisely the value of the instant b. Indeed, the moment b can evolve according to the wear of the parts or other uncontrolled event criteria. The evolution of the torque between instants b and c makes it possible to progressively overcome the tooth-to-tooth friction forces of the claws until the clutch 51 is rotated when it is in contact with the clutch 52 without having to know precisely the value. torque needed to overcome these friction forces. Indeed, the position of the teeth of the dog 51 relative to the position of the teeth of the claw 52 is perfectly random and the angular contact surface of the teeth one on the other may vary depending on the initial relative angular position of the jaws 51 and 52. The teeth of each clutch can just as easily be in front of the cavities of the opposite clutch without denaturing the process, simply superimposing moments b, c and d. The evolution of position 3 represented in FIG. 4b, a for the sole purpose of explaining the result of the actions of the process without having to be controlled, the torque ramp causing a self-adapting effect naturally passing by the value of torque that suits each situation that occurs among a multitude of situations presentation of claws that can occur.

A transition 56 is validated when the clutch 52 is fully engaged in the clutch 51. In the embodiment illustrated in FIG. 2, the all-or-nothing type sensor 32 makes it possible to detect an end of travel of the translational movement of the clutch. the actuator 34 which then validates the transition 56 in the device 40. The method activates a step 57 after validation of the transition 56 following the steps 54 and 55 which were executed simultaneously in parallel.

Step 57 cuts the torque setpoint C * and causes switching of the electric machine torque to a value that results from the driver's will. As represented by the downward slope of the rotational speed 1 in FIG. 4a, the dog 51 quickly reaches zero speed when the teeth of the dog 51 come into flank contact with the teeth of the clutch 52.

The torque clutch torque reference C * increases steadily and then vanishes in step from the maximum value reached when the jaw claws are engaged and in the absence of torque demand resulting from the driver's will.

In order to allow a sliding of the tops of teeth on one another when they abut in the same plane avoiding an excessive speed of rotation of the upstream dog when the tops of teeth arrive in front of the cavities of the downstream clutch, the torque reference C * is limited to a maximum value of friction torque tooth on tooth jaw. It is indeed better to avoid too much acceleration in rotation of the dog at the time of penetration of the teeth in the cavities of the opposite dog because such an acceleration would cause flanks on the sides of the teeth likely to cause damage.

In economic terms, the use of the electric machine control capabilities in both torque and speed, combined with a simplified actuator, simply controlled in all or nothing mode, can significantly reduce costs compared to systems more complex.

Although the invention has been described in connection with a particular embodiment, it is obvious that it is in no way limited and that it can be given many variations and modifications without departing from its scope or his mind. In particular, the electric powertrain can be mounted both at the front and rear of the vehicle, on a running gear identical or different from that on which is mounted the thermal power train. Although not shown in FIG. 2, a gearbox may also exist between the downstream claw and the wheels. The displacement of the downstream clutch can be replaced by a displacement of the upstream clutch.

Claims

A method of coupling an electric machine (42) with wheels (44) of a running gear of a vehicle when the vehicle is stationary, comprising two steps (54, 55) activated in parallel from a request coupling:

a step (54) for bringing two jaw claws (51, 52) in translation along a common axis (46) of rotation, an upstream clutch (51) being integral in rotation with the electric machine (42) and a downstream clutch being integral in rotation with the wheels (44); and

a step (55) for servocontrolling the electric machine (42) in torque to a torque setpoint (C *) for interconnection which starts from a zero value at a moment (a) of the coupling request and which progressively increases so as to remain lower than a value of rotation of the electric machine (42) for a sufficient time to bring the two jaw in translation in a position in which the tops of teeth of the two claws are coplanar and to exceed said value of rotation beyond said time sufficient to achieve the interconnection.

2. Coupling method according to claim 1, characterized in that said torque setpoint (C *) of interconnection follows a ramp of strictly positive direction coefficient and less than or equal to a drag torque exerted on the upstream clutch (51). divided by said sufficient time.

3. A method of coupling according to claim 2, characterized in that the director coefficient is substantially equal to 4 Nm / s.

4. Coupling method according to one of claims 1 to 3, characterized in that it comprises a step (57) of switching said torque setpoint (C *) interconnection to a torque setpoint related to a driver's will when the two jaw are detected fully engaged one into the other.

5. Coupling method according to one of claims 1 to 4, characterized in that the torque linkage setpoint is limited to a maximum value of tooth-to-tooth friction torque jaw.

A coupling system of an electric machine (42) with wheels (44) of a running gear of a vehicle when the vehicle is stationary, comprising:

an upstream clutch (51) integral in rotation with the electric machine (42), a downstream clutch (52) integral in rotation with the wheels (44) and an actuator (34) arranged to bring the two jaw claws (51, 52) closer together; translation along a common axis (46) of rotation;

an electronic device (40) arranged to receive a coupling request, to drive one actuator (34) and to transmit to a power generator (41) supplying the electric machine (42), a torque setpoint (C *) interconnection which starts from a zero value at a moment of reception of the coupling request and which increases gradually so as to remain lower than a value of rotation of the electric machine (42) for a sufficient time to bring the two claws in translation in a position in which the tops of teeth of the two jaw claws are coplanar and exceed said rotation value beyond said time sufficient to achieve the clutch.

Coupling system according to Claim 6, characterized in that the electronic device (40) has a strictly positive ramp coefficient and is less than or equal to a drag torque. exerted on the upstream dog (51) divided by said sufficient time so as to follow a ramp to the torque setpoint (C *) interconnection.

8. Coupling system according to claim 7, characterized in that the steering coefficient is substantially equal to 4 Nm / s.

9. Coupling system according to one of claims 6 to 8, characterized in that it comprises a sensor (32) end of engagement stroke jaw one into the other, and in that the electronic device (40) is arranged to switch said interconnection torque setpoint (C *) to a torque setpoint related to a driver's will when it receives from the sensor (32) a signal indicating that the two claws are fully engaged; one in the other.

Coupling system according to one of Claims 6 to 9, characterized in that the device

(40) has a limitation of the jaw torque setpoint to a maximum value of tooth-on-tooth friction torque jaw.