Method for shift control of a hybrid vehicle with a dual-clutch transmission

Abstract

Method for shift control of a hybrid vehicle with a dual-clutch transmission, wherein the method comprises: a burglary detection process (S10) of determining, by a control device (CLR), when an amount of burglary occurring during an inertia phase of power demand-free ramp-up is equal to or greater than a predetermined reference value; a response start procedure (S20) of starting a coordinated control of an internal combustion engine torque by means of a first coordinated torque, which is determined as a greater than an internal combustion engine model torque derived from a model and an internal combustion engine map torque obtained from a map, in response to a clutch slip, by the control device (CLR), in response to the fact that the magnitude of the dip is equal to or greater than the prescribed reference value; and a response holding process (S30) of determining a second coordinated torque to control an internal combustion engine and controlling an internal combustion engine torque until the inertia phase of the power-demand-free upshift is completed by the control device (CLR).

Description

[0001] The invention relates to a method for shift control for a hybrid vehicle with a dual-clutch transmission (DCT), and in particular a method for controlling upshifting without power demand.

[0002] Upshifting without power demand means shifting into a higher gear, which is carried out in a state where the accelerator pedal is released.

[0003] There are different types of hybrid drives. Among these is a mild hybrid system, which is designed so that an electric motor is always connected to a combustion engine and therefore performs combustion engine start, power support and regenerative braking.

[0004] A vehicle equipped with a mild hybrid drive can be controlled in such a way that regenerative braking is performed during upshifts when no power is demanded and the accelerator pedal is released, in order to maximize the regenerative braking function. In this case, the torque of an internal combustion engine and the regenerative braking torque of an electric motor act on the input shaft of a dual-clutch transmission (DCT).

[0005] Methods for switching control of the prior art are known from EP 2 239 175 B1 and DE 199 39 334 A1.

[0006] However, if both the regenerative braking torque from an electric motor and the torque of an internal combustion engine act on the input shaft of the DCT during power-demand-free upshifting, a severe drop in speed can occur, in which, during an inertia phase at the time of the initial operation of the power-demand-free upshifting, the speed of the internal combustion engine is lower than the speed of an engagement clutch which is connected to gears for a target shift stage.

[0007] Excessive shifting deteriorates the shifting feel and the driving behavior of a vehicle.

[0008] The invention provides a method for shift control for a hybrid vehicle with a dual-clutch transmission (DCT) which can immediately eliminate excessive hesitancy that can occur during the upshifting of a hybrid vehicle with a DCT when no power is required, thereby improving the shift feel and driving behavior and consequently increasing the marketability of the vehicle.

[0009] According to various aspects of the invention, a method for shift control for a hybrid vehicle with a dual-clutch transmission can be provided, wherein the shift control method comprises: a break-in detection step of determining (or ascertaining) whether the amount (or extent) of the break-in (e.g.of the speed drop), which occurs during an inertia phase of power-demand-free upshifting, is equal to or greater than a predetermined reference value, by a control device, a response start step of initiating coordinated control of an internal combustion engine torque by means of a first coordinated torque, which is determined as the greater of an internal combustion engine model torque obtained from a model and an internal combustion engine map torque obtained from a map, in response to a clutch slip, by the control device if the magnitude of the drop is equal to or greater than the prescribed reference value, and a response hold step of determining (or ascertaining) a second coordinated torque to control the internal combustion engine, and controlling an internal combustion engine torque until the inertia phase is completed, by the control device.

[0010] The model from which the internal combustion engine model torque is determined (or calculated) can be expressed as follows: Te_m=Tc_app+Je[(dSchlupf / dt)Ziel+dNi / dt]+α where Te_m represents a model internal combustion engine torque, T c_app a torque of an engagement-side clutch means, J e a moment of inertia of the internal combustion engine, slip means clutch slip (= Ne - Ni), Ne means a speed of the internal combustion engine, Ni means a speed of the engagement clutch, and α means a torque caused by inertia of a drive system.

[0011] The map used to determine the internal combustion engine map torque can be configured to determine the internal combustion engine map torque in response to clutch slip and a base input torque.

[0012] The second coordinated torque in the response hold step can be determined as follows: Te(t)=MAX{MAX[TQI_J,Te(t−1)+descent],MAP[slip,TQI_J]} where Te(t) means a coordinated torque in an instantaneous control cycle, Te(t-1) means a coordinated torque in a previous control cycle, TQI_J means a base input torque, descent (or shutdown) means an amount of torque reduced with a constant slope, slip means clutch slip (= Ne - Ni), Ne means a rotational speed of the internal combustion engine, and Ni means a rotational speed of an engagement-side clutch.

[0013] Following the response hold step, in order to cause the second coordinated torque to gradually approach a base input torque, the control device may perform a torque transfer step of determining a third coordinated torque, controlling the internal combustion engine torque based on the third coordinated torque, gradually increasing the torque of an engagement clutch, and gradually reducing the torque of a disengaging clutch until the disengaging clutch is disengaged.

[0014] The third coordinated torque in the torque transfer step can be determined as follows: Te(t)=MAX[TQI_J,Te(t−1)+descent] where Te(t) means a coordinated torque in an instantaneous control cycle, Te(t-1) means a coordinated torque in a previous control cycle, TQI_J means a base input torque, and descent (or shutdown) means an amount of torque reduced with a constant slope.

[0015] If the clutch slip is maintained at a predetermined reference slip value or lower for a predetermined reference holding period during the torque transfer step, the control unit can perform a shift completion step of completing the shift operation by increasing the torque of the engagement clutch, thus preventing the engagement clutch from slipping with respect to the base input torque.

[0016] The torque of the engagement clutch during the shift completion step can be determined as follows: TCapp(t)=TCapp(t−1)+{[|TQI_J*Factor(RPM,TQI_J)|−TCapp(t−1)] / [Target time−Phase time}] where Tc app (t) a torque of the engagement side clutch in an instantaneous control cycle means Tc app (t-1) represents a torque of the engagement side clutch in a previous control cycle, TQI_J represents a base input torque, target time represents a target period required to complete a torque phase, and phase time is an elapsed time taken for the torque phase.

[0017] The invention is explained in more detail with reference to the drawing. The drawing shows: Fig. 1 a view illustrating by way of example the construction of a hybrid vehicle with a dual-clutch transmission (DCT) to which the invention is applicable; and Fig. 2 a flowchart illustrating a method for shift control for a hybrid vehicle with a DCT according to an exemplary embodiment of the invention.

[0018] In the figures, the reference numerals refer to the same or equivalent parts of the present invention across the individual figures of the drawing.

[0019] The following describes in detail, with reference to the attached drawing, a method for the switching control of a hybrid vehicle with a DCT according to an exemplary embodiment of the invention.

[0020] Fig. Figure 1 is an exemplary view illustrating the design of a hybrid vehicle with a DCT to which the invention is applicable. The hybrid vehicle can have a mild hybrid drive in which power from an internal combustion engine E is transmitted via a first clutch CL1 and a second clutch CL2 to a first input shaft IN1 and a second input shaft IN2 of a DCT, respectively, and after a change in rotational speed is supplied via an output shaft OUT to drive wheels W, and in which the internal combustion engine E is connected to an electric motor M, which is configured to perform an internal combustion engine start, power assistance, and regenerative braking.

[0021] Furthermore, the hybrid vehicle also features clutch actuating devices CA for driving the first clutch CL1 and the second clutch CL2, shift actuating devices SA with select and shift functions for changing gears, and a control device CLR for controlling the clutch actuating devices CA and the shift actuating devices SA to automatically shift gears.

[0022] The CLR control unit receives information about the degree to which the driver depresses the accelerator pedal via an accelerator pedal position sensor (APS) and also receives information about the engine speed and torque, as well as the vehicle speed. Based on this information, the CLR control unit controls the clutch actuators (CA) and the shift actuators (SA), allowing the DCT to automatically shift gears depending on the vehicle's driving conditions.

[0023] The internal combustion engine is controlled by a separate internal combustion engine management system (EMS). Through communication with the EMS, the CLR control unit can receive information related to the internal combustion engine and request the EMS to control the engine's torque depending on the driving and shift conditions of the vehicle. The EMS can then control the internal combustion engine in response to this request.

[0024] The CLR control unit can be implemented as a transmission management system (TMS). Depending on an exemplary embodiment of the invention, the CLR control unit can be implemented as an integrated control system in which the EMS and the TMS are integrated. The electric motor can be configured such that it can be controlled by the TMS, the EMS, or a separate control unit in accordance with the internal combustion engine and the DCT.

[0025] During the shifting process, one of the first clutches, CL1, and the second clutch, CL2, disengage, while the other engages. This means that, depending on the shift situation, one of the two clutches is a disengaging clutch, which is disconnected from the combustion engine, and the other is an engaging clutch, which is brought into contact with the combustion engine.

[0026] With regard to the Fig. 2 comprises a method for shift control for a hybrid vehicle with a DCT according to an exemplary embodiment of the invention, a dip detection step S10 of determining whether the extent of the dip occurring during an inertia phase of power-demand-free upshifting is equal to or greater than a predetermined reference value by a control device, and a response start step S20 of starting a coordinated control of the internal combustion engine torque by means of a first coordinated torque, which is determined as the greater of an internal combustion engine model torque obtained from a model and an internal combustion engine map torque obtained from a map, in response to a clutch slip by the control device if the extent of the dip is equal to or greater than the prescribed reference value.and a response hold step S30 of determining a second coordinated torque to control the internal combustion engine, and of controlling the internal combustion engine torque until the inertia phase is completed by the control device.

[0027] This means that if a dip occurs, in which the internal combustion engine speed is lower than the speed of the engaging clutch during the inertia phase of the power-demand-free upshift, the invention detects the occurrence of the dip and controls the internal combustion engine torque to reduce the dip in the response hold step S30, thus preventing the dip from intensifying and eliminating it immediately. As a result, a deterioration in shift feel is prevented, and the vehicle's driving characteristics are improved.

[0028] The reference value can be set by design choices, such as the extent of the intrusion that needs to be eliminated in the response hold step S30.

[0029] This means that if it is desired to actively respond to even a small dip by means of the response hold step S30, the reference value can be set relatively small. Conversely, if it is desired to execute the response hold step S30 when a relatively large dip occurs, the reference value can be set relatively large.

[0030] The model from which the internal combustion engine model torque is determined is expressed by the following equation 1. Te_m=Tc_app+Je[(dSchlupf / dt)Ziel+dNi / dt]+α where Te_m represents a model internal combustion engine torque, T c_app a torque of the engagement-side clutch means, J ea moment of inertia of the internal combustion engine, slip means clutch slip (Ne - Ni), Ne means a speed of the internal combustion engine, Ni means a speed of the engagement clutch, (dslip / dt) Ziel a rate of change of the target slip, and α represents a torque caused by the inertia of the drive system.

[0031] The map used to determine the internal combustion engine map torque is configured to calculate the internal combustion engine map torque in response to the clutch slip and the DCT's base input torque. The internal combustion engine map torque can be expressed by the following equation: Combustion engine map torque=map[slip,TQI_J].

[0032] Here, the DCT's base input torque (TQI_J) is a base torque input from the internal combustion engine to the DCT. Specifically, the DCT's base input torque (TQI_J) is a base torque input when the EMS (Electric Vehicle System) automatically performs a determination in response to a signal from the APS (Automatic Power System) and controls the internal combustion engine based on this determination in the state where the CLR (Control Unit Reliability) does not instruct the EMS to control the internal combustion engine's torque depending on the vehicle's shift state. The DCT's base input torque includes the regenerative braking torque generated when the electric motor performs a regenerative braking function. The DCT's base input torque is simply referred to as the "base input torque."

[0033] That is, as in Fig. As shown in Figure 1, during an inertia phase of the power-demand-free upshifting in the hybrid drive, in which the combustion engine and the electric motor are always connected, a coordinated control of the combustion engine torque based on the combustion engine model torque, which is determined by the model described above, is immediately carried out according to the invention in order to prevent the drop in the speed of the combustion engine, which occurs as a result of the torque of the regenerative braking by the electric motor, from being amplified and to reduce the drop.

[0034] The coordinated torque used to perform the coordinated control of the internal combustion engine torque in the response start step S20 is the first coordinated torque, as described above. The first coordinated torque is determined to be the greater of the internal combustion engine model torque and the internal combustion engine map torque.However, since the internal combustion engine model torque, which is determined by inputting the rate of change of the target slip with which the control unit intends to control the drive model with the internal combustion engine and the clutch, reduces the dip in the initial stage of the control process responding to the dip faster than the internal combustion engine map torque, which is determined based on the clutch slip, the first coordinated torque can be determined as the internal combustion engine model torque when the response start step S20 has to be carried out.

[0035] Here, the "inertia phase" of the power-demand-free upshift refers to a synchronization process of changing the internal combustion engine speed from the speed of the disengaging clutch to the speed of the engaging clutch by reducing the torque of the disengaging clutch. The "torque phase," which follows the inertia phase, is a process of completing the shift by gradually increasing the torque of the engaging clutch while gradually reducing the torque of the disengaging clutch until the disengaging clutch is fully disengaged.

[0036] The second coordinated torque in the response hold step S30 is determined from the following equation 2. Te(t)=MAX{MAX[TQI_J,Te(t−1)+Descent(C)],MAP[Slip,TQI_J]} where Te(t) means a coordinated torque in the current control cycle, MAX means a function that inverts the largest value between two data points in the following bracket, Te(t-1) means a coordinated torque in the previous control cycle, TQI_J means a base input torque, Descent(C) means the amount of torque reduced with a constant slope C, MAP[Slip,TQI_J] means the internal combustion engine map torque determined by the clutch slip and the DCT's base input torque, Slip means a clutch slip (Ne - Ni), Ne means an internal combustion engine speed, and Ni means an engagement clutch speed.

[0037] This means that the second coordinated torque in the response hold step S30 is used to generate the coordinated torque used for the coordinated control of the internal combustion engine torque to approximate the base input torque by gradually reducing the coordinated torque from the first coordinated torque, which was used as an initial value for the coordinated control of the internal combustion engine torque in the response start step S20, with the constant slope C.

[0038] In other words, in the response start step S20, the control unit requests the EMS to significantly increase the torque of the internal combustion engine to the first coordinated torque, and in the response hold step S30, the additional torque of the internal combustion engine, which the control unit requests the EMS to increase, is gradually reduced to 0.

[0039] Here, the slope C can be set as the value by which the coordinated torque is linearly reduced from the first coordinated torque to the base input torque during the estimated time remaining until the completion of the inertial phase.

[0040] After determining that the gears for a target shift stage of power-requirement-free upshifting are fully engaged, and that the speed of the internal combustion engine and the speed of the engagement clutch have been approximately synchronized within a predetermined range of clutch slip, the control device is configured to determine that the inertia phase has been completed.

[0041] For example, in the case where the target shift stage is a fourth range, when the gears for the fourth range are fully engaged, and when the clutch slip is 50 rpm or less, the control device may be configured to determine that the inertia phase has been completed.

[0042] After the response hold step S30, in order to cause the second coordinated torque to gradually approach the base input torque, the control device performs a torque transfer step S40 of determining a third coordinated torque, controlling the torque of the internal combustion engine based on the third coordinated torque, gradually increasing the torque of the engagement-side clutch, and gradually reducing the torque of the disengaging-side clutch until the disengaging-side clutch is disengaged.

[0043] This means that the torque transfer step S40 essentially corresponds to the torque phase described above. The torque phase is a process of completing the shifting operation by fully disengaging the disengaging clutch and increasing the torque of the engaging clutch, in which the base input torque and the torque of the regenerative braking by the electric motor interact until the point where no slippage of the engaging clutch occurs.

[0044] In the exemplary embodiment of the invention, the torque phase is divided into the above torque transfer step S40 and a switching completion step S50, which will be described later.

[0045] The third coordinated torque in the torque transfer step S40 is determined by the following equation 3. Te(t)=MAX[TQI_J,Te(t−1)+Descent(E)] where Te(t) means a coordinated torque in the current control cycle, MAX means a function that inverts the largest value between two data points in the following bracket, Te(t-1) means a coordinated torque in the previous control cycle, TQI_J means a base input torque, and Descent(E) means the amount of torque reduced with a constant slope E.

[0046] This means that when the torque transfer step S40 starts, the coordinated torque used for the coordinated control of the internal combustion engine torque is gradually reduced with the constant slope E.

[0047] Of course, at the start of the torque transfer step S40, the coordinated torque in the preceding control cycle can be the second coordinated torque.

[0048] The second coordinated torque is controlled, as described above, such that it gradually approaches the base input torque during the response hold step S30. Therefore, the coordinated torque can approach the base input torque during the torque transfer step S40. At this point, the third coordinated torque is the base input torque. If the coordinated torque does not reach the base input torque by the time the response hold step S30 is completed, the third coordinated torque controls the coordinated torque so that it approaches the base input torque with a constant slope E.

[0049] Therefore, the slope E can be set as the value at which the coordinated torque is linearly reduced to the base input torque at the initial time of the torque transfer step S40 during the target period required to complete the torque phase.

[0050] If the clutch slip is maintained at a predetermined reference slip value or lower for a predetermined reference holding period during the torque transfer step S40, the control unit performs the shift completion step S50 of completing the shift operation by increasing the torque of the engagement clutch, thus preventing the engagement clutch from slipping with respect to the base input torque.

[0051] The reference slip value can be set as the value, e.g., 20 rpm, at which the internal combustion engine speed and the speed of the engagement clutch are synchronized with a small difference between them, in order to avoid the occurrence of shocks, even if the torque of the engagement clutch is significantly increased. The reference holding period can be set as the value at which it can be confirmed that the condition in which the clutch slip is held at or below the predetermined reference slip value is not temporary, but rather permanent.

[0052] This means that, in the exemplary embodiment of the invention, the torque phase is operated such that, when no further shift shock occurs, even if the torque of the engagement clutch is further increased during the torque transfer step S40, the process immediately transitions to the shift completion step S50, in which the torque of the engagement clutch is increased based on the following equation until the point where no slippage of the engagement clutch occurs, even when the regenerative braking torque is input into the DCT. This process is referred to as the "additional increase of the torque of the engagement clutch" in Fig. 2 expressed.

[0053] The torque of the engagement clutch in the shift completion step S50 is determined by the following equation 4: TCapp(t)=TCapp(t−1)+{[|TQI_J*Factor(Rotation speed,TQI_J)|−TCapp(t−1)] / [Target (H)−Phase time]} where Tcapp (t) a torque of the engagement-side clutch in the current control cycle means Tc app (t-1) means a torque of the engagement side clutch in the previous control cycle, TQI_J means the basic input torque, factor (speed,TQI_J) means a value determined via a characteristic map or formula according to the speed and the TQI_J, target time(H) means a target period H required to complete the torque phase, and phase time means the time used for the torque phase.

[0054] This means that the torque of the engagement clutch is determined by dividing the difference between the base input torque, which includes the torque of the regenerative braking, and the torque of the engagement clutch in the previous control cycle by the time remaining until the completion of the torque phase, and adding the value obtained by dividing the torque of the engagement clutch in the previous control cycle.

[0055] Furthermore, the difference between the base input torque and the torque of the engagement-side clutch in the previous control cycle can be increased or decreased by reflecting the vehicle speed and the intensity of the base input torque, i.e., by multiplying the base input torque by a factor determined taking into account the base input torque and the vehicle speed.

[0056] Therefore, a design such that the factor is determined by a function or characteristic map of the vehicle speed and the basic input torque may be desirable.

[0057] Furthermore, in the switching completion step S50, the coordinated torque is controlled by the third coordinated torque, so that the combustion engine torque approaches the base input torque until the inertia phase is completed.

[0058] As can be seen from the above description, in the method for shift control for a hybrid vehicle with a DCT according to an exemplary embodiment of the invention, it is possible to immediately eliminate excessive dipping, which can occur during the power-demand-free upshifting of a hybrid vehicle with a DCT, thereby improving the shift feel and driving behavior and consequently increasing the marketability of the vehicle.

Claims

[1] Method for shift control of a hybrid vehicle with a dual-clutch transmission, wherein the method comprises: a burglary detection process (S10) of determining, by a control device (CLR), when an amount of burglary occurring during an inertia phase of power demand-free ramp-up is equal to or greater than a predetermined reference value; a response start procedure (S20) of starting a coordinated control of an internal combustion engine torque by means of a first coordinated torque, which is determined as a greater than an internal combustion engine model torque derived from a model and an internal combustion engine map torque obtained from a map, in response to a clutch slip, by the control device (CLR), in response to the fact that the magnitude of the dip is equal to or greater than the prescribed reference value; and a response holding process (S30) of determining a second coordinated torque to control an internal combustion engine and controlling an internal combustion engine torque until the inertia phase of the power-demand-free upshift is completed by the control device (CLR). [2] Method according to claim 1, wherein the model from which the internal combustion engine model torque is determined is expressed as an equation: Te_m=Tc_app+Je[(dSchlupf / dt)Ziel+dNi / dt]+α where Te_m represents a model internal combustion engine torque, where T c_app a torque of an engagement-side clutch means, where J e a moment of inertia of the internal combustion engine means, where slippage means clutch slippage (= Ne - Ni), where Ne represents the rotational speed of the internal combustion engine, where Ni represents a rotational speed of the engagement-side clutch, and where α represents a torque caused by the inertia of a drive system. [3] Method according to claim 1 or 2, wherein the map used to determine the internal combustion engine map torque is configured such that it determines the internal combustion engine map torque in response to the clutch slip and a predetermined input torque. [4] Method according to any one of claims 1 to 3, where the second coordinated torque in the response holding process (S30) is determined from an equation: Te(t)=MAX{MAX[TQI_J,Te(t−1)+descent],MAP[slip,TQI_J]} where Te(t) represents a coordinated torque in an instantaneous control cycle, where Te(t-1) represents a coordinated torque in a previous control cycle, where TQI_J represents a predetermined input torque, where descent means an amount of torque that is reduced with a constant inclination, where slippage means clutch slippage (= Ne - Ni), where Ne represents the rotational speed of the internal combustion engine, and where Ni represents the rotational speed of an engagement clutch. [5] Method according to any one of claims 1 to 4, wherein after the response holding process (S30) in order to cause the second coordinated torque to approach a predetermined input torque, the control device (CLR) is configured to perform a torque transfer process (S40) of determining a third coordinated torque, controlling the torque of the internal combustion engine based on the third coordinated torque, increasing the torque of an engagement-side clutch, and reducing a torque of a disengaging-side clutch until the disengaging-side clutch is disengaged. [6] Method according to claim 5, wherein the third coordinated torque in the torque transfer process (S40) is determined as an equation: Te(t)=MAX[TQI_J,Te(t−1)+descent] where Te(t) represents a coordinated torque in an instantaneous control cycle, where Te(t-1) represents a coordinated torque in a previous control cycle, where TQI_J represents a predetermined input torque, and where descent means an amount of torque that is reduced with a constant inclination. [7] Method according to claim 5 or 6, wherein in response to maintaining the clutch slip at a predetermined reference value of slip or less for a predetermined reference holding period during the torque transfer operation (S40), the control device (CLR) is configured to perform a switching completion operation (S50) of completing the switching operation by increasing the torque of the engagement clutch, thus preventing the engagement clutch from slipping with respect to the predetermined input torque. [8] Method according to claim 7, where the torque of the engagement clutch in the shift completion process (S50) is determined as an equation: TCapp(t)=TCapp(t−1)+{[|TQI_J*Factor(RPM,TQI_J)|−TCapp(t−1)] / [Target time−Phase time}] where Tc app (t) a torque of the engagement side clutch in an instantaneous control cycle means, where Tc app (t-1) means a torque of the engagement side clutch in a previous control cycle, where TQI_J represents a predetermined input torque, where target time means a target period required for the completion of a torque phase, and where phase time means the time required for the torque phase.

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