Method for controlling the disengagement of internal couplings from gears on transmission shafts, transmissions, and drivetrains

Description

[0001] The present invention relates to the control of powertrains of hybrid vehicles.

[0002] More specifically, it relates to a method for controlling the disengagement of the teeth of an internal transmission coupler, placed under the control of a shift actuator, to engage or disengage a transmission ratio of the torque supplied by a heat engine connected to the transmission input without a cut-off clutch.

[0003] It also relates to a transmission and a hybrid powertrain, composed of a thermal engine connected without a cut-off clutch to a first transmission input shaft, an electric machine connected to a second transmission input shaft, and at least one coupling toothed coupler on a speed pinion placed under the control of a shift actuator.

[0004] In most road vehicles, the transmission of energy from the engine to the wheel is done through a gearbox with multiple configurations.

[0005] Some hybrid vehicles have dog-clutch gearboxes, or "claws", without a cut-off clutch between the combustion engine and the gearbox.

[0006] From publication WO 2014 / 207332, a hybrid transmission of this type is known, having several electric, thermal and hybrid ratios, where the torques of the thermal engine and at least one electric machine are added towards the wheels. The thermal torque is transmitted to the wheels on a transmission ratio " thermal ", and that of the torque of the main electric machine on a report "electric".

[0007] We know of publication FR 3 018 486 disclosing a method for controlling the clearance of the teeth of an internal transmission coupler.

[0008] Publication US 2010203996 is known, disclosing a transmission control method without a cut-off clutch at the transmission input.

[0009] Internal combustion engines cannot operate at a certain speed. In conventional robotic or automated transmissions, a request to decouple the engine from the wheels is imposed on the clutch during braking, which risks causing the engine to stall. In the absence of a cut-off clutch at the transmission input, braking can place the engine in conditions that prevent it from operating normally, and possibly cause it to stall.

[0010] In the hybrid powertrains (GMP) mentioned above, the engagement and disengagement of the dog clutches is done through a strategy involving both the control of internal actuators of the transmission, and the control of the torque actuators of the vehicle (internal combustion engine and electric motor).

[0011] To ensure the gearbox gears disengage, it is necessary to reduce the residual torque at the dog clutch below a specific threshold for a sufficient period of time. In the event of sudden braking, the actuators concerned do not always have the capacity to achieve these objectives before the engine enters a degraded operating range.

[0012] When the engine speed is too low for normal operation, the internal combustion engine produces explosions that generate positive torque and regulate idle speed. These explosions cause shocks and vibrations, which impact the entire vehicle through the powertrain. They are very unpleasant for users.

[0013] The present invention aims to limit the shocks and vibrations transmitted to the drive train and to the vehicle, by degraded operation of the thermal engine, or by its stalling.

[0014] For this purpose, when the thermal engine enters a critical situation of risk of stalling when decelerating in a gear engaged: a first critical zone is determined as a function of the engine speed, in which the actuator is forced to disengage the gear to prevent stalling, and a second critical zone is determined as a function of the engine speed and its deceleration, in which the engine timing is controlled by prohibiting fuel injection.

[0015] Preferably, the first critical zone is an area in which the actuator has the ability to disengage the ratio depending on the resulting torque exerted by the rotating parts of the transmission, on the teeth of the coupler.

[0016] Preferably, the second critical zone is an area in which the actuator has no ability to disengage the gear, based on the resulting torque exerted by the rotating parts of the transmission on the teeth of the coupler.

[0017] In the proposed hybrid transmission and GMP, the shift actuator and the injection of the thermal engine are controlled according to this strategy.

[0018] The present invention will be better understood upon reading the following description of a non-limiting embodiment thereof, with reference to the appended drawings, in which: there Figure 1 schematically represents a Hybrid GMP architecture, fig 2 shows the forces involved on a dog gearbox coupler Figure 3 illustrates the proposed strategy.

[0019] Gearbox 1 of the Figure 1is for example of the "robotic" type. Its operation is that of a manual gearbox, but the gear changes are automated. The diagram shows an electric machine, called HSG (for high voltage alternator-starter) 2, a thermal engine 3 on a solid primary shaft 4. Another electric machine 5 called ME, more powerful than the first, is mounted on a hollow primary shaft 6. The secondary shaft of the gearbox 7 is connected to the differential (not shown), then to the wheels of the vehicle.

[0020] A first sliding clutch and dog clutch located on the secondary shaft 7 makes it possible to modify the ratio of the electric machine ME 5, independently of the rest of the gearbox to have two electric ratios EV1 and EV2. The second sliding clutch and dog clutch 8, located on the solid primary shaft 4, makes it possible to modify the ratio of the thermal engine 3 separately from the electric ratios, to establish two thermal ratios Th2 and Th4, independent of the electric ratio. The third sliding clutch and dog clutch 11 located on the transfer shaft 10 makes it possible to establish a third thermal ratio Th3, when it moves to the right on the diagram. It is possible to choose independently at any time, the desired ratio on the first electric machine ME and that desired on the thermal engine group Mth and the second electric machine HSG 2.The combinations of thermal and electrical ratios make it possible to create hybrid ratios.

[0021] On the Figure 2 , a toothed coupling, or straight dogs (also called clutches) of a gearbox has been schematically represented, like the couplers 8 and 11 of the Figure 1. The coupler 8, 11 has coupling teeth 12 secured to a sliding gear 14 linked in rotation to the shaft 1a (in dotted lines on the diagram), and sliding on the latter under the control of a fork 15 of the shift actuator (not shown). The axial movement of the sliding gear 14 determines the engagement or disengagement of a gear, by the coupling / uncoupling of its dogs 12 with the dogs 13 of a speed pinion (not shown) rotating on the shaft 1a. The sliding gear 14 is fixed in rotation on the shaft 1a. Its axial movement is carried out under the action of a fork 15, placed under the control of a shift actuator. The straight arrow f translates the force of the actuator to disengage a gear. The rotating arrow C1 illustrates the torque at the drive shaft imposed on the sliding gear. Rotating arrow C2 illustrates the torque on the drive shaft (not shown) that is imposed on the idler gear.The force resulting from the couples C1 and C2 on the dogs of the idler gear has a tangential component T, and a longitudinal component, which results in a friction force. l between dogs 12 and 13. The force l opposes the effort of the actuator, and can delay or slow down the disengagement of the gear. To ensure the disengagement of the dogs, the actuator exerts a force on a sliding lever 14 which has a sliding degree of freedom relative to the transmission shaft 1a.

[0022] The gearbox actuators have limited capacities, so it is necessary to limit as much as possible the resultant of the applied torques C1, C2, or better, to cancel them, to ensure the release of the dogs in the best conditions. However, the achievement of the torque instructions by the electrical machines and the thermal engine of the GMP, is itself limited in amplitude by the specific performances of these components. Finally, the approval constraints and their dynamic performances also limit the achievement of the torque instructions.

[0023] Under these conditions, there are situations where the disengagement of the dogs cannot be achieved: in some cases, the resultant of the torques does not decrease sufficiently to allow the movement of the player, in other cases, the resultant of the torques decreases sufficiently, but the period during which its value allows the movement of the player is too short, before the torque reverses and increases again in the opposite direction.

[0024] The method of the invention consists in controlling the disengagement of the teeth of the internal transmission coupler 8, 11, placed under the control of a shift actuator to engage or disengage a transmission ratio of the torque supplied by a thermal engine connected to the input of the transmission without a cut-off clutch. The proposed method is based on the detection of a critical situation. The detection is based on the observation of the engine speed, and its derivative. Without departing from the scope of the invention, the detection of a critical situation can also be based on an alert from the braking system.

[0025] When the thermal engine enters a critical situation of risk of stalling when decelerating in a gear engaged, a first critical zone is determined as a function of the engine speed ω thermal, in which the actuator is forced to disengage the gear to prevent stalling, and a second critical zone is determined as a function of the engine speed and its deceleration, in which the engine timing is controlled by prohibiting fuel injection.

[0026] Engine deceleration can be determined by the value of the derivative of its speed (dω / dt), or by the vehicle's braking system.

[0027] The general principle is to detect the two distinct critical zones, based on the observation of the engine speed and its deceleration: the first critical zone, where there is a risk of stalling and where the system has the capacity to disengage the wheel motor, and the second critical zone, where there is a risk of stalling and where the system does not have the capacity to disengage the wheel motor.

[0028] In the first zone, the response provided is to force the clutch release, overriding the general state instruction of the kinematic chain: in this zone the actuator has the capacity to disengage the gear according to the resulting torque exerted by the rotating parts of the transmission, on the teeth of the coupler.

[0029] In the second zone, this response consists of controlling the timing of the thermal engine by prohibiting fuel injection: in this zone, the actuator does not have the capacity to disengage the gear, depending on the resulting torque exerted by the rotating parts of the transmission on the teeth of the coupler.

[0030] In the particular case of a hybrid GMP without a cut-off clutch at the input of the transmission, such as that of the Figure 1 , the transmission combines the torque of the thermal engine and that of at least one electric machine over several distinct transmission ratios. The invention provides in this case the activation of the double strategy described: the first strategy called " anti-stall strategy ", and the second strategy called " timing strategy ", depending on the conditions encountered. As indicated above, the application areas of these two strategies can be determined by ranges of values of the engine speed ω, and its variation, as a function of time, preferably filtered. According to the illustration of the Figure 3 , we thus identify three operating zones, depending on the speed of the thermal engine ω, and its derivative dω / dt: a first zone A, called nominal operating zone, or "nominal mode"", where no particular strategy is applied, a second, intermediate zone B, of activation of the "anti-stall strategy", and a third zone C, for activating the “ timing strategy » .

[0031] The proposed transmission, illustrated by the Figure 1 , comprises at least one internal coupler 8, 11, placed under the control of a shift actuator to engage or disengage a transmission ratio of the torque supplied by a heat engine connected to the input of the transmission without a cut-off clutch.

[0032] In accordance with the invention, the passage actuator and the injection of the thermal engine are controlled according to the method described above.

[0033] In a particular embodiment, the couplers 8, 11 concerned have a sliding clutch 14 and a dog clutch 12.

[0034] The proposed hybrid GMP is composed of a heat engine connected without a cut-off clutch to a first transmission input shaft 4, an electric machine (ME) connected to a second transmission input shaft and at least one coupling toothed coupler 8, 11 on a speed pinion placed under the control of a shift actuator. According to the invention, the heat engine and the coupler actuators are controlled in accordance with the method described above.

[0035] Such a hybrid powertrain can include, in addition to a thermal engine and a main electric machine ME, an auxiliary electric machine HSG providing torque on the thermal ratios. The strategy described is then applicable under the following conditions: A " thermal report» is engaged, that is to say that the thermal engine is mechanically coupled to the wheels on a transmission ratio, whatever its state, in particular when the auxiliary electric machine is used to compensate for the torque hole during the transition between Z1 and Z2, when the thermal engine is switched off, and the derivative of the speed of the auxiliary electric machine HSG, dω / dt is in a first activation zone.

[0036] There " timing strategy » is applicable when: A " thermal report» is engaged, that is to say that the thermal engine is mechanically coupled to the wheels on a transmission ratio, whatever the state of the thermal engine, in particular when the auxiliary electric machine HSG used to compensate for the torque hole during the change between the two electric ratios, when the thermal engine is switched off, and the derivative of the speed of the auxiliary electric machine HSG, dω / dt is in a second activation zone, where the anti-lock braking system (ABS) is active.

[0037] The invention makes it possible to limit the impact shocks on the drive train, which can impact its reliability, as well as the inconveniences linked to these shocks for passengers.

Claims

1. Method for controlling a combustion engine (3) and the disengagement of the teeth of an internal transmission coupler (8), placed under the control of a gearshift actuator to engage or disengage a transmission ratio transmitting the torque supplied by the combustion engine connected to the input of the transmission without a decoupling clutch, wherein, when the combustion engine enters a critical situation in which there is a risk of stalling under deceleration in an engaged gear ratio, - a first critical zone, in which the actuator is forced to disengage the gear ratio in order to prevent stalling, is determined as a function of the speed (ω) of the combustion engine (3) and of its deceleration, characterized in that, when the combustion engine enters said critical situation in which there is a risk of stalling under deceleration in an engaged gear ratio: - a second critical zone, in which the stalling of the engine is managed by preventing the injection of fuel, is determined as a function of the speed (ω) of the combustion engine and of its deceleration.

2. Control method according to Claim 1, characterized in that the first critical zone is a zone in which the actuator has the ability to disengage the gear ratio as a function of the resultant torque exerted by the rotary parts of the transmission on the teeth of the coupler.

3. Control method according to Claim 1 or 2, characterized in that the second critical zone is a zone in which the actuator does not have the ability to disengage the gear ratio as a function of the resultant torque exerted by the rotary parts of the transmission on the teeth of the coupler.

4. Control method according to Claim 1, 2 or 3, characterized in that the deceleration of the engine is determined by the value of the derivative of its speed (dω / dt).

5. Control method according to Claim 1, 2 or 3, characterized in that the deceleration of the engine is determined by the braking system of the vehicle.

6. Control method according to Claim 4, characterized in that three operating zones are identified as a function of the speed (ω) of the combustion engine and of its derivative (dω / dt): - a first nominal operating zone (A), in which no particular strategy is applied, - a second intermediate operating zone (B) of activation of an anti-stall strategy corresponding to the first critical zone, and - a third operating zone (C) of activation of a stall strategy, corresponding to the second critical zone.