Control of the clutch of the dct transmission train in the crawl phase

Abstract

The present invention relates to a control device and a control method for controlling a DCT-type powertrain for a hybrid vehicle, said DCT-type powertrain comprising a first gearbox BV1 coupled to an engine assembly EM by a first clutch C1 and a second gearbox BV2 coupled to said engine assembly EM by a second clutch C2. The control device comprises a slip control component for controlling the slip of the first and second clutches C1 and C2 to ensure the distribution of the transmission of the drive power sent by the engine assembly EM between the first and second gearboxes BV1 and BV2 when the temperature of the first clutch C1 reaches a predefined temperature threshold.

Description

Technical Field

[0001] This invention claims priority to French application No. 2104398, filed on April 28, 2021, the contents of which (text, drawings and claims) are incorporated herein by reference.

[0002] This invention generally relates to the technical field of traction systems for hybrid vehicles, including DCT-type powertrains.

[0003] More specifically, this invention relates to the operation of two clutches in a DCT-type powertrain equipped in a hybrid vehicle during the engagement phase (also referred to as the creep phase). During this creep phase, the gliding of the clutches allows the vehicle to move smoothly at low speeds.

[0004] The present invention relates to a DCT-type powertrain (more specifically, an eDCT-type powertrain) equipped in a hybrid vehicle, wherein the driving energy of the hybrid vehicle is generated by two different power systems (i.e., a thermal engine that consumes fossil fuels, and an electric motor powered by an electrical energy storage assembly (which recovers the kinetic energy of the vehicle and / or recharges it by connecting the vehicle to an external electrical energy source).

[0005] The present invention also relates to any other type of hybrid vehicle equipped with a thermal engine and a non-thermal engine, wherein the non-thermal engine consumes energy stored in an energy storage component, the energy being capable of generating (as a substitute for or supplement to) driving energy generated by the thermal engine. The stored energy may be of an electrical, hydraulic, or pneumatic source. When the stored energy is electrical, the storage component may be a battery.

[0006] This invention is particularly applicable to the movement of hybrid vehicles at low speeds, such as the starting phase or creep phase of the vehicle (up to 10 km / h to 12 km / h). To enable the vehicle to move at low speeds, the vehicle has a so-called creep function, during which slippage occurs in the clutch system to adjust the torque transmitted from at least one of the vehicle's engines to at least one of the vehicle's wheel axles according to a speed setpoint triggered by the driver's foot on the vehicle's accelerator pedal. Background Technology

[0007] In the following description, the embodiment of the invention described is a hybrid vehicle, the drive power of which is alternatively or supplementally ensured by a thermal engine and an electric motor, the electric motor being supplied with electrical energy by a battery. The thermal engine and the electric motor form an engine assembly, the drive energy of which is transmitted to the front or rear axle by a DCT-type transmission. This embodiment of the invention was chosen to facilitate the description of the invention, but is not limited thereto. In fact, the invention can also be applied, for example, to vehicles in which drive energy is transmitted to more than one axle.

[0008] In known DCT-type transmissions for hybrid vehicles, a control device ensures the transmission of engine torque generated by a thermal engine, an electric engine, or both to the drive wheel axle. This control device manages: a first clutch that engages the engine assembly with a first gearbox and includes an odd-numbered gear ratio; and a second clutch that engages the engine assembly with a second gearbox and includes an even-numbered gear ratio.

[0009] In a conventional DCT transmission, a first gear ratio is engaged in the first gearbox, and the control mechanism manages the slippage of the first clutch to ensure the transmission of engine torque to the drive wheels and axles based on the pressure applied by the driver on the accelerator pedal. This slippage phase of the clutch is called the creep phase, which ensures smooth movement of the vehicle at low speeds. In a mechanical transmission, the slippage of the clutch is controlled by the pressure applied by the driver's left foot on the clutch pedal. The DCT transmission reduces the burden on the driver in operating the clutch. A second gear ratio can be engaged in the second gearbox to shift from the first gear ratio to the second gear ratio to increase the vehicle's speed, while the second clutch is disengaged and the second gearbox is inactive until this gear ratio changes.

[0010] During the creeping phase, slippage of the first clutch causes it to heat up. This can lead to overheating, which prevents optimal clutch operation. Summary of the Invention

[0011] The present invention aims to overcome, in whole or in part, the overheating problem of the clutch in a DCT transmission during the creeping phase.

[0012] Therefore, the objective of this invention is to limit the heat generated by the first clutch.

[0013] To this end, according to a first aspect of the present invention, a control device for operating a DCT-type transmission system is provided, the DCT-type transmission system comprising: a first gearbox connected to an engine assembly via a first clutch; and a second gearbox connected to the engine assembly via a second clutch. The control device includes a slip control component for controlling the slippage of the first clutch and the second clutch to ensure the transmission and distribution of drive power delivered by the engine assembly between the first gearbox and the second gearbox when the temperature of the first clutch reaches a predetermined temperature threshold.

[0014] Therefore, in order to transmit a portion of the drive power sent by the engine assembly, the second clutch engages, which limits the temperature of the first clutch from rising to the predetermined threshold.

[0015] Preferably, the gear ratio is engaged in each of the first and second gearboxes, and the slip control device manages the slip of the first and second clutches so that the drive power transmitted by the engine assembly is gradually transferred from the first clutch to the second clutch.

[0016] This management of clutch slippage allows the transmission of drive power from the two gearboxes to the same drive wheel axle, even though gear ratios with different reduction ratios are engaged in the first and second gearboxes.

[0017] Advantageously, the rotational speed of the engine shaft of the engine assembly is increased in order to increase the slippage of the first clutch and the second clutch.

[0018] Preferably, a first gear ratio is engaged in the first gearbox, a second gear ratio is engaged in the second gearbox, and the slip control device induces a creep phase during which the drive power of the engine assembly is transmitted through the slip of the first clutch, and when the first clutch reaches the predetermined temperature threshold, the drive power is transmitted through the slip of the first clutch and the second clutch.

[0019] This combination of features can limit the heat generated by the first clutch during the start-up or creeping phase.

[0020] According to a second aspect of the invention, a vehicle is provided, the vehicle including a DCT-type powertrain and a control device for operating the DCT-type powertrain as described above.

[0021] According to a third aspect of the present invention, a method for operating a DCT-type transmission system is provided, wherein the drive power of the engine assembly is transmitted to a first gearbox via the slippage of a first clutch, and when the temperature of the first clutch reaches a predetermined temperature threshold, the drive power is distributed between the first gearbox and the second gearbox via the slippage of the first clutch and the slippage of a second clutch.

[0022] By having a portion of the drive power transferred by the second clutch, the method can prevent the first clutch from overheating.

[0023] Preferably, the slippage of the first clutch and the second clutch is controlled so that the drive power transmitted by the engine assembly is gradually transferred from the first clutch to the second clutch.

[0024] Thus, despite the different gear ratios engaged in the gearbox, the slippage of the two clutches compensates for the difference in rotational speed between the engine shaft and the first primary shaft and the second primary shaft.

[0025] Advantageously, the rotational speed of the engine shaft of the engine assembly is increased in order to increase the slippage of the first clutch and the second clutch.

[0026] The significant increase in the rotational speed of the engine shaft can maintain the drive power transmitted to the drive wheel axle, regardless of the increase in losses caused by the slippage of the two clutches.

[0027] Preferably, after the second clutch is engaged and slipped, when the first clutch reaches a predetermined temperature threshold, the power of the engine assembly is gradually transferred from the first clutch to the second clutch until it is transmitted solely by the second clutch.

[0028] The gradual transfer of drive power from the first clutch to the second clutch manages the creep phase, thereby allowing the vehicle to start and smoothly transition between the first and second gear ratios.

[0029] Other features and advantages of the invention will become clearer from the following detailed description of non-limiting embodiments relating to different aspects of the invention. Attached Figure Description

[0030] This specification refers to the accompanying drawings, which are given only as non-limiting embodiments of the invention:

[0031] - Figure 1 The transmission system between the engine assembly and the drive wheel axle is schematically shown; and

[0032] - Figure 2 The evolution of key parameters during the creeping phase is illustrated using a graph. Detailed Implementation

[0033] Figure 1 A transmission device is shown that connects the engine assembly EM to the drive wheel axle TRM. The engine assembly EM includes a thermal engine MT, the output shaft AS of which (located downstream of the inertial flywheel VI) is connected to a primary clutch PC. An electric motor ME is connected downstream of the primary clutch. The primary clutch PC can rotatably engage or disengage the thermal engine MT and the electric motor ME. Thus, when the thermal engine MT is running, it drives the electric motor, which acts as an electric generator, to rotate and charge the battery. When the electric motor ME takes over from the thermal engine MT, the primary clutch disengages to relieve the electric motor ME of its load, and the electric motor does not drive the thermal engine MT. The primary clutch can be engaged so that the electric motor ME, together with the thermal engine, contributes to the movement of the vehicle.

[0034] At the output of the electric motor, the engine shaft AM rotatably connects the engine assembly EM to a first clutch C1 and a second clutch C2. The first clutch C1, in the engaged position, ensures the transmission of drive energy to a first gearbox BV1, which includes odd-numbered gear ratios (here, a first gear ratio, a third gear ratio, and a fifth gear ratio). The second clutch C2, in the engaged position, ensures the transmission of drive energy to a second gearbox BV2, which includes even-numbered gear ratios (here, a second gear ratio, a fourth gear ratio, and a sixth gear ratio). The first gearbox BV1 and the second gearbox are rotatably integrated with a driveshaft AT, which drives the drive wheel axle TRM to rotate.

[0035] A control device (not shown) for operating the DCT transmission system controls the actuation of the first clutch C1 and the second clutch C2 so that the driving energy from the engine component EM (based on the vehicle speed and the speed setpoint transmitted by the driver's right foot pressure on the accelerator pedal) is transmitted from the first gearbox BV1 or the second gearbox BV2 to the drive wheel axle TRM. When shifting to a higher gear ratio or downshifting to a lower gear ratio, the control device manages the slippage of the first clutch C1 or the second clutch C2 to avoid sudden or residual transmission changes in engine torque to the drive wheel axle.

[0036] When the vehicle is started, it is gradually moved, which is ensured by the slippage of the first clutch C1 connected to the first transmission BV1 (wherein the first gear ratio is engaged). The control device includes a control component (not shown) capable of controlling the slippage of the first clutch C1 so that the desired torque is transmitted to the drive wheel axle TRM during the starting or creeping phase. Slippage of clutch C1 during the creeping phase causes the temperature of the first clutch C1 to rise, which may cause the first clutch to overheat and degrade or simultaneously degrade its operation.

[0037] Figure 2 The operation of the control device (used to manage slippage of the first clutch C1 and the second clutch C2 during the creep phase) is illustrated using multiple graphs. A temperature threshold for the first clutch C1 is defined to prevent overheating exceeding this threshold. Figure 2 As shown by the curve "Temperature C1", when the first clutch C1 reaches the temperature threshold at time T0, the set value is transmitted to the control device, which initiates a torque transmission strategy from the first gearbox BV1 and the second gearbox BV2 to the drive wheel axle TRM, in which the second gear ratio is engaged. The triggering of this creep phase for the DCT transmission system is shown by the curve "Switching Trigger Strategy". Thus, during the creep phase, from time T0, the control device manages the slippage of the first clutch C1 and the second clutch C2 so that the drive power transmitted from the engine assembly EM to the drive wheel axle TRM is distributed between the first clutch C1 and the second clutch C2 until time T1, at which time the torque is primarily transmitted to the drive wheel axle TRM by the second clutch C2. Therefore, the drive power transmitted from the engine assembly EM gradually shifts from the first clutch C1 to the second clutch C2, ensuring a gradual increase in speed during the creep phase without abrupt transmission changes. The graphs “Torque transmitted by C1” and “Torque transmitted by C2” show the transfer of drive power from the first clutch C1 to the second clutch C2 to the drive wheel axle TRM between time T0 and time T1.

[0038] The slip control device manages the slip of the first clutch C1 and the second clutch C2 to follow a reduction ratio of a first gear ratio engaged in the first gearbox BV1 and a second gear ratio engaged in the second gearbox BV2, while ensuring that the vehicle moves at the speed desired by the driver (the evolution of which is shown by the curve "Vehicle Speed"). As an example, Figure 2The diagram shows the fluctuations in the rotational speeds of the first primary shaft AP1, the second primary shaft AP2, and the engine shaft AM over time. The rotational speed of the first primary shaft AP1 changes from 1000 tr / min to 1020 tr / min between time T0 and time T1 (see curve "Speed ​​AP1"), while the rotational speed of the second primary shaft AP2 increases, for example, with the initial speed associated with the drive of the wheels (which is increased via the second gearbox BV2) and the pre-engaged gear ratio, until the second primary shaft AP2 reaches 780 tr / min when the second clutch C2 is engaged (see curve "Speed ​​AP2").

[0039] like Figure 2 As shown, the slip control device of the control mechanism ensures that the slip of the first clutch C1 and the second clutch C2 can obtain the rotational speed of the first primary shaft AP1 and the second primary shaft AP2 (compatible with the rotational speed of the drive shaft AT). In parallel, the speed of the engine shaft AM is significantly increased to create a larger slip in the first clutch C1 and the second clutch C2. For example, as by… Figure 2 As shown by the curve “speed AM”, the rotational speed of the engine shaft AM changes from 1000 tr / min to 1500 tr / min between time T0 and time T1. In the same time interval, the rotational speed of the first primary shaft AP1 only increases from 1000 tr / min to 1020 tr / min and the rotational speed of the second primary shaft AP2 only reaches 780 tr / min.

[0040] exist Figure 2 Based on the curve diagram, and according to the method described below, the control device described above for controlling the DCT transmission system controls the slippage of the first clutch C1 and the second clutch C2, as well as the power transmission from the engine assembly EM to the drive wheel axle TRM.

[0041] During the creep phase, the slip control device manages the slippage of the first clutch C1 to transmit the drive power required to move the vehicle at the speed desired by the driver (its evolution is shown by the curve "Vehicle Speed") to the drive wheel axle TRM. The slippage of the first clutch C1 causes it to heat up (shown by the curve "Temperature C1"). At time T0, the first clutch C1 reaches a predetermined temperature threshold, triggering a limiting strategy to limit the heat generation of the first clutch C1, as shown by the curve "Switching Trigger Strategy". This triggering causes the slip control device to cause the second clutch C2 to slip in parallel with the first clutch C1. Between time T0 and time T1, the slippage of the first clutch C1 and the second clutch C2 is managed by the slip control device to distribute the drive power transmission to the drive wheel axle TRM between the first transmission BV1 and the second transmission BV2. The evolution of the engine torque transmitted from the first clutch C1 and the second clutch C2 to the drive wheel axle TRM is shown by the curves "Torque Transmitted by C1" and "Torque Transmitted by C2". Between time T0 and time T1, the engine torque transmitted by the first clutch C1 decreases until it becomes zero at time T1, while the engine torque transmitted by the second clutch C2 (which is zero at time T0) increases until time T1.

[0042] The clutch slip control device manages the slip of the first clutch C1 and the second clutch C2 to follow the rotational speeds of the first primary shaft AP1 and the second primary shaft AP2 (determined by the rotational speed of the drive shaft AT) required for the vehicle to move at a speed desired by the driver (shown by the curve "Vehicle Speed"). When the vehicle is in the acceleration phase, the rotational speed of the first primary shaft AP1 increases from 1000 tr / min to 1020 tr / min between time T0 and time T1, as shown by the curve "Speed ​​AP1". Simultaneously, the rotational speed of the second primary shaft AP2 between time T0 and time T1 converts the initial speed (increased via the second gearbox BV2) related to the drive of the wheels and the pre-engaged gear ratio until the second primary shaft AP2 reaches 780 tr / min when the second clutch C2 is disengaged, as shown by the curve "Speed ​​AP2". Between time T1 and time T0, the rotational speed of the engine shaft AM increases significantly compared to the rotational speeds of the first primary shaft and the second primary shafts C1 and C2. The rotational speed is changed from 1000 tr / min to 1500 tr / min to obtain greater slippage at the positions of the first clutch C1 and the second clutch C2. Thus, the significant increase in the rotational speed of the engine shaft AM maintains the drive power transmitted to the drive wheel axle TRM, regardless of the increased losses caused by the slippage of the two clutches C1 and C2.

[0043] The rotational speed values ​​mentioned above are given only in an illustrative manner to illustrate the management of clutches C1, C2 and engine assembly EM by the control device according to the strategy, which can prevent overheating of the first clutch C1 by distributing the drive power to be transmitted to the drive wheel axle TRM between the first clutch C1 and the second clutch C2.

[0044] As described above, different aspects of the present invention may be implemented in configuration variations that differ from the configurations described above, depending on the context.

[0045] Naturally, the present invention has been described above by way of example only. Of course, those skilled in the art can implement different embodiments of the invention without departing from its scope.

Claims

1. A control device for operating a DCT-type transmission system, the DCT-type transmission system comprising: The first gearbox (BV1) is connected to the engine assembly (EM) by a first clutch (C1); The control device includes a slip control component for controlling the slip of the first clutch and the second clutch (C1, C2) to ensure the transmission distribution of drive power sent by the engine assembly (EM) between the first gearbox and the second gearbox (BV1, BV2) when the temperature of the first clutch (C1) reaches a predetermined temperature threshold, with the gear ratio engaged in each of the first gearbox and the second gearbox (BV1, BV2); and the slip control component manages the slip of the first clutch and the second clutch (C1, C2) so that the drive power transmitted by the engine assembly (EM) is gradually transferred from the first clutch (C1) to the second clutch (C2), and the rotational speed of the engine shaft (AM) of the engine assembly (EM) is increased to increase the slip of the first clutch and the second clutch (C1, C2).

2. The control device for controlling a DCT-type transmission system according to claim 1, characterized in that, A first gear ratio is engaged in the first gearbox (BV1), a second gear ratio is engaged in the second gearbox (BV2), and the slip control device initiates a creep phase during which: - The drive power of the engine assembly (EM) is transmitted through the slippage of the first clutch (C1), and - When the first clutch (C1) reaches the preset temperature threshold, the drive power is transmitted through the slippage of the first clutch (C1) and the second clutch (C2).

3. A vehicle, characterized in that, The vehicle includes a DCT-type powertrain and a control device for operating the DCT-type powertrain according to any one of the preceding claims.

4. A control method for operating a DCT-type transmission system, wherein, The drive power of the engine assembly (EM) is transmitted to the first gearbox (BV1) via the slippage of the first clutch (C1). When the temperature of the first clutch (C1) reaches a predetermined temperature threshold, the drive power is distributed between the first gearbox (BV1) and the second gearbox (BV2) via the slippage of the first clutch (C1) and the slippage of the second clutch (C2). The slippage of the first clutch (C1) and the second clutch (C2) is controlled so that the drive power transmitted by the engine assembly (EM) is gradually transferred from the first clutch (C1) to the second clutch (C2). The rotational speed of the engine shaft (AM) of the engine assembly (EM) is increased to increase the slippage of the first clutch (C1) and the second clutch (C2).

5. The control method for controlling a DCT-type transmission system according to claim 4, wherein, After the second clutch (C2) is engaged and slipped, when the first clutch (C1) reaches a predetermined temperature threshold, the power of the engine assembly (EM) is gradually transferred from the first clutch (C1) to the second clutch (C2) until it is transmitted only by the second clutch (C2).

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