CN111757995B

CN111757995B - Method for controlling a drive train and control device for a drive train

Info

Publication number: CN111757995B
Application number: CN201880090152.1A
Authority: CN
Inventors: T·M·H·K·拉海伊; K·S·赖斯
Original assignee: Nanjing Bangqi Automatic Transmission Co ltd
Current assignee: Nanjing Bangqi Automatic Transmission Co ltd
Priority date: 2017-12-29
Filing date: 2018-12-28
Publication date: 2022-11-15
Anticipated expiration: 2038-12-28
Also published as: BE1025869B1; WO2019129860A1; BE1025869A9; BE1025869A1; CN111757995A; BE1025869B9

Abstract

A control method for controlling a torque converter (TC/LUC) having a lock-up clutch unit includes providing a TC/LUC control signal (Pset) to the TC/LUC to set the TC/LUC (20) to a desired operating mode. The method includes a calibration procedure having the steps of: -causing the TC/LUC to gradually disengage from the engaged state prior to the calibration procedure if the feedback control is disabled; -enabling feedback control to determine a representative value of a feedback control signal that, in combination with a reference open loop control signal, causes the TC/LUC (20) to operate at a reduced slip rate, after detecting that the monitored slip rate of the TC/LUC exceeds a predetermined threshold value, -disabling feedback control and modifying the reference open loop control signal with a modification value based on the representative value.

Description

Method for controlling a drive train and control device for a drive train

Technical Field

The present invention relates to a control apparatus for a power train.

The invention further relates to a method for controlling a powertrain.

The invention further relates to a powertrain comprising such a control device.

The powertrain in a continuously variable transmission typically includes a torque converter/lock-up clutch (TC/LUC), a forward-neutral-reverse clutch (DNR), and a transmission. The transmission is typically provided as a drive belt mechanically coupling two pulleys. In the normal driving phase, all elements of the powertrain are preferably operated in a slip-free mode, since slip operation can lead to energy losses and thereby negatively impact fuel economy. Slip modes of the transmission should be avoided in particular, since this can lead to wear of the drive belt and/or the pulleys. This can be achieved by a high level of clamping. On the other hand, the clamping level, in particular of the drive belt, should not be set too high, since this would mean that the charging system supplies a drive current which does not have to be high to maintain this high clamping level, which is also not favorable for fuel economy. Additionally, increasing the level of clamping above that required for slip-free operation of the transmission tends to increase the transmission losses of the transmission and the wear of the transmission due to increased friction. Furthermore, it should be taken into account that the driving conditions may change suddenly, for example due to a road damage or a rapid braking of the vehicle. To avoid slippage of the transmission under such conditions, the LUC torque capacity should be set to a value lower than the torque capacity of the transmission. It is thereby achieved that the TC/LUC acts as a fuse in the case of an unexpectedly high torque to be transmitted, which absorbs the unexpected torque by slipping, thus avoiding slipping of the transmission. The LUC, which is typically designed as a wet clutch, can be operated in a continuous slip mode without damage.

US2003150683 discloses a control method for a powertrain comprising a continuously variable transmission and a clutch arranged in series therewith. The control method comprises the following procedures: the engagement pressure of the clutch is first reduced until slip occurs, and then increased to re-engage the clutch after slip is detected, and the engagement pressure of the clutch to be established is calculated by giving an excessive pressure to the engagement pressure at which the clutch is re-engaged, so that the amount of transmitted excessive torque of the clutch is set smaller than that of the continuously variable transmission. The control method involves a change in the setting of the clutch, which can be perceived by the driver or passenger in the vehicle and thus reduces driving comfort.

Disclosure of Invention

A first object is to provide a control arrangement for a powertrain in which the risk of discomfort due to varying clutch settings is reduced.

A second object is to provide a control method arranged to control a powertrain with a reduced risk of discomfort due to varying clutch settings.

A third object is to provide a powertrain comprising an improved control device.

According to said first object, an improved control device is provided.

The improved control apparatus includes a TC/LUC controller that provides a TC/LUC control signal for controlling an engagement state of a lock-up clutch of a torque converter. The TC/LUC controller includes an open-loop control section and a closed-loop control section. The TC/LUC control signal may be provided, for example, to a driver that generates an electric drive signal for a hydraulic control unit provided to actuate the TC/LUC. Alternatively, the TC/LUC may be actuated without an intervening hydraulic control unit, such as by one or more electromagnetic actuators directly coupled to the TC/LUC elements. The control device comprises a calibration facility for calibrating the TC/LUC controller. It may thereby be achieved that the operation of the TC/LUC controller is adapted to change in behavior over time, e.g. due to wear and temperature variations. The open-loop control section is configured to determine a nominal control signal value that is a raw estimate of the control signal expected to achieve the predetermined engagement state of TC/LUC.

The TC/LUC controller further includes a closed-loop control section. The control section is arranged to adapt the TC/LUC control signal to a value which minimizes a deviation between the actual engagement state and the predetermined engagement state when the closed-loop control section is enabled. Such a deviation may be detected, for example, as a slip ratio, e.g., a ratio between an input rotation speed and an output rotation speed, or a difference between the input rotation speed and the output rotation speed.

The control device is operable in a calibration mode comprising at least a first, a second and a third calibration phase.

In a first calibration phase, the feedback control section is disabled and the open loop control section gradually modifies the value of the TC/LUC control signal from an initial control signal value to a stop control signal value. The initial TC/LUC control signal value is the value of the TC/LUC control signal immediately prior to entering the calibration mode. Thus, if the feedback control section is disabled before entering the calibration mode, the initial TC/LUC control signal value is equal to the immediately preceding open loop control signal value. The latter may comprise a predetermined component that does not change over time and a calibration component determined in a calibration mode. Alternatively, the open loop control signal value may be provided as a single calibratable. The stop control signal value is a value of the TC/LUC control signal in the case where it is detected that the TC/LUC assumes a slip operation mode, for example, a value for which a slip of the TC/LUC becomes detectable, a value for which it is detected that the output rotational speed starts to differ from the input rotational speed. Alternatively, the predetermined slip ratio may be a slip ratio defined by a predetermined ratio between the output rotation speed and the input rotation speed.

After detecting the slip mode of operation, a second calibration phase is entered. Wherein the feedback control section is enabled to adapt the value of the TC/LUC control signal from the stop control signal value to an intermediate control signal value for which it is detected that the TC/LUC reaches the predetermined engagement state. The predetermined engagement state is typically the operating state of the TC/LUC at its slip limit (i.e., with the minimum engagement required to maintain slip-free operation at the current value of torque transmitted by the TC/LUC). Alternatively, the predetermined engagement state may be another engagement state that is regarded as a reference, for example, a state in which TC/LUC has a certain slip rate at the current value of the transmitted torque. Preferably, however, the predetermined engagement state to be achieved by the feedback control section is an operating state of TC/LUC at its slip limit, as this may minimise as much as possible the slip of TC/LUC during the calibration procedure.

A third calibration phase is then entered in which the feedback control section is disabled again and the calibration value is set to a value based on the difference between the intermediate control signal value and the nominal control signal value.

In this improved control arrangement, activating the feedback control section in the second calibration phase achieves a smooth but fast transition between the first calibration phase and the third calibration phase. This contributes to driving comfort.

This advantage is also achieved by the improved method of the present invention.

Furthermore, an improved powertrain is provided. An improved powertrain including a continuously variable transmission system including a torque converter/lock-up clutch (TC/LUC), a forward-neutral-reverse clutch (DNR) and a transmission further includes the improved control apparatus.

Drawings

These and other aspects are described in more detail with reference to the figures. Wherein:

fig. 1 schematically shows a powertrain in a vehicle;

FIG. 2 shows a portion of a controller for the powertrain in more detail;

3A-3C illustrate various signals and status indicators during operation;

4A-4C illustrate the controller in various operating states;

fig. 5 illustrates a control method.

Detailed description of the embodiments

Fig. 1 schematically shows a powertrain in a vehicle for transmitting power from a power source 10, such as an internal combustion engine or an electric motor, to wheels 70 of the vehicle. The powertrain shown in fig. 1 includes a torque converter/lock-up clutch (TC/LUC) 20, a forward-neutral-reverse clutch (DNR), a transmission 40, fixed gears 50, and a differential 60.TC/LUC 20 couples the output shaft of power source 10 to DNR 30 at a controllable slip ratio and torque ratio associated therewith (i.e., the ratio between the torque transmitted at its output and the torque received from power source 10 at its input). A DNR clutch 30 is provided to couple the TC/LUC 20 to the transmission 40. The DNR clutch 30 is controllable to assume one of a drive mode D corresponding to driving the vehicle in a forward direction, a reverse mode R in which the vehicle is driven in a reverse direction, and a neutral mode in which it maintains the transmission 40 decoupled from the TC/LUC 20. The transmission 40 transmits power delivered from the power source 10 through the TC/LUC and DNR clutches 30 to the wheels 70 via the fixed gear 50 and the differential 60 at a gear ratio selectable from a continuous range.

In the illustrated embodiment, the torque TC/LUC 20, DNR 30, and the setting or operating mode of the transmission 40 are provided by hydraulic pressureThe signal (i.e., the pressure of the hydraulic fluid). The hydraulic signal is supplied by a Hydraulic Control Unit (HCU) 80, and a feed flow P is supplied to the Hydraulic Control Unit (HCU) 80 by a pump 85 ₈₀ . In the illustrated embodiment, the state of TC/LUC 20 is determined by hydraulic pressure P ₂₀ The state of the DNR clutch 30 is controlled by the hydraulic pressure P ₃₂ And the state of the transmission is controlled by the hydraulic pressure P ₄₁ And P ₄₂ To set it. To this end, the hydraulic control unit 80 is in turn controlled by a Transmission Control Unit (TCU) 100. Alternatively, the state of various powertrain elements may be controlled by electrical signals, for example using electromagnetic actuation elements. The TCU 100 is further coupled to the engine control unit 90, for example via a bus (here CAN bus 95). The TCU is further configured to receive input signals from various inputs, such as a turbine speed signal (output speed of TC/LUC), a primary pulley speed corresponding to the DNR output speed, a secondary pulley speed at the output of the transmission 40, a secondary pulley pressure, and a tank temperature. Other input signals, such as from an accelerator pedal, a brake pedal (not shown), and sensor elements (e.g., speed sensor, temperature sensor, torque sensor, etc. (not shown)) may be received and monitored by the engine control unit 90 and communicated to the TCU 100 via the CAN bus 95.

FIG. 2 shows the TC/LUC controller C for controlling the state of the TC/LUC 20 in more detail ₂₀ . In this diagram, the component 115 instructs the conversion of the control signal Pset into a pressure P to be provided to the TC/LUC 20 to achieve its desired setting ₂₀ The element of (1). The TC/LUC controller C20 includes an open-loop control section OLC and a closed-loop control or feedback control section CLC. The operation of which is controlled by the main control unit 110.

Depending on the overall mode of operation, the main controller 110 may configure the TC/LUC controller C in various ways ₂₀ . The overall operating mode may be determined by the operating state of the vehicle (e.g., start, stop, accelerate from stop, smooth drive, brake), and may further be determined by a power setting (e.g., selected in a range from a low power mode to a high power mode).

In the illustrated embodiment, the master controlThe controller 110 determines the TC/LUC controller C ₂₀ The operation of (2). The main controller 110 typically also controls other parts of the driveline, such as the DNR 30 and the variator 40, as schematically indicated by the bold arrows S10, S30, S40 representing issued control signals and received status signals. The master controller 110 in turn interacts with the driver 5, for example, to receive driver input signals such as accelerator pedal pressure and brake signal pressure, transmission mode selection R/N/D, and the like. The master controller may also signal the status to the driver via a user interface. The main controller 110 may also request certain functionality from the ECU 90. In special situations, e.g. upon detection of an error such as a defect in the transmission, the master controller may become dominant and e.g. force the vehicle to travel only at a low speed (to stop at the side of the road, etc.).

An embodiment of the TC/LCU controller C20 is now described in more detail. As mentioned above, it includes an open-loop control section OLC and a closed-loop control or feedback control section CLC. In the illustrated embodiment, the open-loop control section has a nominal control signal generator 120 to generate a nominal control signal P indicative of a nominal control value estimated to achieve the predetermined engagement state _f . The predetermined engagement state is the following state of TC/LUC: in this state, it should be able to slip at a rate n specified by the main controller 110 _ref Transmits a reference torque M also specified by the main controller 110 _ref . Generally, the predetermined engaged state is a state in which TC/LUC is operating at its slip limit. In fact, the actual behavior of the TC/LUC will differ from these reference characteristics due to wear of the TC/LUC and temperature variations. A calibration signal P is provided for generating a calibration value _cal The calibration signal generator of (2). The open-loop controller OLC is configured to provide the open-loop control signal P with a value based on the nominal control value and on a calibration value _olc To control the TC/LUC in open loop mode. In the illustrated embodiment, this is achieved by summing the values in adder 122. The TC/LUC controller further comprises a closed-loop control section CLC arranged to provide a correction signal P in an active state of the closed-loop control section _c The correction signal P _c Indicating a correction value to changeThe value indicated by the open-loop control signal Polc in order to correct the deviation between the actual engagement state and the predetermined engagement state.

In the illustrated embodiment, the closed-loop control zone CLC includes a comparator 111 to issue an indication of slip rate n as specified by the main controller 110 _s,ref And the difference between the measured slip as determined by the slip rate monitor 116. The slip speed monitor may, for example, monitor the slip rate n _s Is determined as the difference n _e -n _t I.e. speed n at the input of TC/LUC _e And the rotational speed n at the output of the LUC _t The difference between them. An adaptation controller (such as a PI controller 112) is provided which issues a correction signal P _c The correction signal P _c Can be added to the open-loop control signal P _olc To obtain a control signal P _set . Control signal P _set May be converted into a control current which in turn controls a hydraulic control unit HCU 80, the hydraulic control unit HCU 80 generating a desired hydraulic signal P to the TC/LUC 20 in response to the control current ₂₀ . In FIG. 2, block 115 schematically represents the conversion to control current and the generation of a pressure signal P ₂₀ The combined functionality of (a).

The main controller 110 is configured to selectively enable a feedback control loop as schematically indicated by the switching element 113 controlled by the switching signal S113. Fig. 2 schematically illustrates the various computational steps as separate elements. For example,

adders

122, 123, and 114 are shown to combine the respective control signals. However, the controller need not actually be implemented in this manner. For example, various functionality in the controller may be performed in various ways.

Importantly, the open loop control section OLC can keep TC/LUC properly engaged in the locked mode. That is, during normal driving conditions, TC/LUC slip should be avoided, and TC/LUC can be used as a fuse in the driveline to avoid slip in the transmission in the event of an unexpectedly high torque occurrence. However, the behaviour of TC/LUC varies with time due to wear and temperature changes.

In order to maintain a reliable open loop control, the control device is operable in a calibration mode, which will be described in more detail with reference to fig. 3.

Fig. 3A-3C illustrate various signals and status indicators during operation of the control device. In FIG. 3A, solid line M ₂₁ Shows the actual torque capacity M that can be transferred by the TC/LUC 20 without slip _luc (Torque [ Nm)]) And a longer dotted line M ₂₂ Shows that the LUCU should be able to transmit the nominal value M of the torque without slip in the current situation, taking into account the safety margin value _ref . A shorter dashed line M slightly above the longer dashed line ₂₃ Indicating a value corresponding to a desired operation near the slip limit.

As becomes apparent from the example of fig. 3, in particular as shown in fig. 3A, at a point in time t ₀ Curve M ₂₁ Indicated actual torque capacity M _luc Substantially higher than what is expected given current circumstances. In order to avoid the risk of the transmission slipping, this means that the transmission drive belt must also be held at a tension that does not necessarily have to be high. If this is the case, the charging system supplies a drive current that is unnecessarily high to maintain the high clamping level, at the expense of additional fuel consumption. In addition, the transmission may suffer from increased wear and consume more power than is strictly necessary.

In FIG. 3B, curve P ₂₁ Showing the TC/LUC control signal P as a function of time _set The value of (c). In this case, the value is expressed as a pressure value (pressure [ bar ]) applied to the TC/LUC of the hydraulic control]). In this example, the engagement degree generally increases as the control signal value increases. In other embodiments, the engagement may generally decrease as the value of the control signal increases. Alternatively, the value of the TC/LUC control signal may be expressed as a voltage or a current, e.g. a value of a control voltage or a control current of a TC/LUC used to control a pressure value of a hydraulic pressure to control a hydraulic control, or a value of a control voltage or a control current of a TC/LUC used to control an electromagnetic operation.

Dotted line P extending over the entire width in FIG. 3B ₂₂ Is the value of the TC/LUC control signal that is initially expected to achieve an engaged state of the TC/LUC in which the TC/LUC is able to transmit a nominal value of the transmitted torque (M) operating at its slip limit _ref ). A shorter dotted line P slightly above the longer dotted line ₂₃ TC/LUC control signal P indicative of the torque actually required to achieve TC/LUC for delivering the torque while operating at its slip limit _set The value of (c).

FIG. 3C illustrates indicators for the status of TC/LUC. Straight line S ₂₄ (SW status) indicates a status where TC/LUC 20 is at a higher control level. Specifically, it indicates that it is desirable for TC/LUC to be in the locked mode at a higher control level during the time interval represented by the graph. Piecewise linear curve S ₂₅ The actual physical state of the TC/LUC 20 is schematically shown.

An exemplary control method for controlling the TC/LUC will now be described with reference to FIGS. 3A-3C introduced above. As can be seen in fig. 3A-3C, at t ₀ Extend to t ₁ During a first time interval of (3), control signal P _set Is applied with the control signal P _set Is a first feedforward component P _f And a calibration component P _cal Is predicted to achieve the transmission torque M operating at its slip limit _ref Necessary for the required nominal clamping, calibration component P _cal Is provided as a second feed-forward component to allow the TC/LUC to pass slip-free up to a predetermined threshold level M _luc The torque of (c). The lock-up clutch controller in this operating state is shown in fig. 4A.

As noted above, under the circumstances depicted in this example, the torque capacity M _luc Is set too high. From this operating state, the TC/LUC is locked and a calibration procedure may be initiated. Other requirements may be checked to determine whether a calibration procedure was initiated, such as whether a predetermined period of time has elapsed since a previous execution of the self-calibration procedure. If the lapse of the predetermined period of time is one of the conditions, in the event of a malfunction (unexpected occurrence of discontinuity such as high fuel consumption or torque transmission or slip rate is detected)In the case, the initiation of the calibration procedure may be performed before the predetermined lapse in time.

At a point in time t ₁ And as shown in fig. 4B, a calibration procedure is initiated. In this first phase of the calibration procedure, the component P is modified _mod Is added to the nominal control value. In fig. 2, this is schematically shown as a contribution P provided by the ramp signal generator 124 in the open loop control section OLC _mod . From being equal to the calibration signal P _cal Starting with the original value of the value of (b), modifying the component P _mod Is gradually changed as indicated by the inclination "a" in fig. 3, so as to cause the TC/LUC to gradually separate. It is assumed here that the degree of TC/LUC bonding is positively correlated with the signal Pset. Alternatively, the correlation may be negative, in which case a positive inclination will be applied to the modification component. At point in time t2, the control signal value Pset is reduced to a value at which TC/LUC operates at its slip limit. At another point in time t ₃ Where t is ₃ -t ₂ = f, the control signal having reached the stop value P for which a slip was actually detected _stop 。

At a point in time t ₃ Upon this detection, a second calibration phase is entered in which the feedback control mode is re-enabled, as shown in fig. 4C. In fig. 2, this means that the main controller 110 uses the control signal S ₁₁₃ To cause the switching element 113 to close. The feedback control section CLC gradually changes the value of the control signal Pset from the value P _f +P _mod (t ₃ ) Is adapted to set the TC/LUC to a value necessary for its predetermined engagement state (typically an engagement state in which the TC/LUC has a minimum degree of engagement required to maintain slip-free operation at the current value of the torque transmitted by the TC/LUC). Then, when the control signal P is fed back _c Has reached an intermediate value P _c,lock Time, control signal P _set And (4) stabilizing. The feedback component may be considered sufficiently stable if the change in the feedback component is less than a predetermined threshold (e.g., based on the estimated noise level) (e.g., a slip rate corresponding to zero slip or a predetermined minimum amount of slip). The intermediate value may for example be the control signal P during a time interval in which the feedback component is stabilized _set OfMean or median. Alternatively, the feedback component may be considered to be sufficiently stable upon expiration of the predetermined time interval. The predetermined time interval may be related to a time constant of the feedback loop (e.g., a time interval having a duration of 2 or 3 times the time constant). Although the feedback component may still exhibit variations that exceed the noise level, the intermediate value may be determined by basing the value on t ₃ And the value of the feedback component at a predetermined time interval after t4 extrapolates the feedback control signal P _c Is calculated. E.g. at time interval t ₃ -t ₄ As seen therein, the feedback controller rapidly reverts the TC/LUC 20 towards the no-slip mode of operation, while providing a smooth transition from low-slip operation to no-slip operation towards the end of the second phase.

A third calibration phase is then entered, in which the feedback control is disabled again, as shown in fig. 4A, and the calibration signal P _cal Is set. The updated calibration value is based on the intermediate value P _c,lock And a nominal control value P _f The difference between them. In one embodiment, the updated calibration value may be equal to the difference. In another embodiment, the updated calibration value is set to the sum of the difference and the additional value "B", as illustrated in fig. 3B. Difference P _c,lock –P _f Can be taken from the time point t ₄ Control signal P of _set Or may be a time point t ₄ Is required to modify the signal P _f To obtain a correction signal P of a predetermined engagement state _c . As described above, in the illustrated embodiment, the feedback control segment includes P _I The controller 112, i.e., the feedback control section, includes an integral action control component. In one embodiment, the output of the integral action control component may be used to determine the intermediate signal P _c,lock . This is advantageous because the signal is already free from noise due to the integrating action of the component.

This aspect is schematically illustrated by an update element 125, which update element 125 records a feedback component P _c By means of the feedback component P _c Reaches a predetermined engagement state. Based on the signal, furtherThe new element 125 updates the calibration signal P to be provided by the element 121 _cal 。

As best seen in FIG. 3B, at time point t ₅ At stage 3 of the calibration procedure, the updated calibration value is based on the intermediate value, with another component denoted "b" added as part of the feed forward signal. In this way, a safety margin is provided. It is achieved that normal torque variations due to minor road surface level variations do not immediately cause TC/LUC slip. As further shown in the middle graph, at the slave time point t ₄ To t _4a In the first phase of the third calibration phase of (a), the further component b is gradually increased from 0 to its final value according to a ramp denoted by c. At a point in time t _4a At this point, a plateau is reached, in which the calibration signal is maintained at the excessive modification value. Thus avoiding the discontinuity of the transmission behavior of the TC/LUC.

At a point in time t ₅ At, a new calibration period is initiated, wherein at a point in time t ₅ To t ₉ The phases of the calibration procedure at (a) correspond to the phases t, respectively ₁ To t ₄ 。

It is noted that the calibration procedure is basically performed in a locked mode of TC/LUC. Although this temporarily results in TC/LUC slip, this is done in a controlled manner. Accordingly, during the calibration procedure, the nominal control signal generator 120 is assuming the specified torque M _ref Generation of a nominal control signal P with zero slip transfer _f Even if the least amount of slippage occurs during the calibration procedure. In other operating states, the nominal control signal generator 120 may also be operated by considering a specified slip ratio n other than 0 _s,ref To calculate the nominal control signal P _f 。

It is noted that the graphs are not drawn to scale. For example, the time interval f may be substantially smaller than the time interval suggested by the figure. For example, the length f of the time interval for detecting the slip may be on the order of tens of milliseconds, e.g., 20 milliseconds, since it is primarily determined by the valve hysteresis and the slip detection debounce time. The timer for initiating a new calibration period may for example be set at a value g in the order of a few seconds to a few tens of seconds. The timer is provided to leave a time frame in which the TC/LUC is rendered compatible with the new operating point as specified by the external drive control signal.

FIG. 5 schematically illustrates a calibration routine in a control method for controlling the TC/LUC 20 arranged in series with the transmission 40 in a continuously variable transmission system. The control method provides a TC/LUC control signal P _set To set the TC/LUC 20 to the desired operating mode. The control signal is obtained by closed-loop control, open-loop control, or by a combination of open-loop and closed-loop control.

In step S0, it is determined whether a calibration procedure should be initiated. For example, it may be determined whether the TC/LUC is currently operating in a locked mode. If this is not the case, an intermediate step may be performed in which the TC/LUC is controlled to enter the locked mode of operation. It may further be determined whether the driveline is operating at a relatively low clamping level, such as a level denoted MIN or ECO. If the drive train is operating at a relatively high clamping level, an intermediate step may be performed in which the clamping level is reduced to a relatively low clamping level. It may also be verified whether a predetermined time interval has elapsed since completion of a previous calibration procedure. In some cases, this requirement may not exist or may be denied assuming a system failure is detected.

Assuming that it is decided in step S0 to initiate a calibration procedure, a first calibration phase is entered in step S1A, wherein an open loop based control signal is provided to the TC/LUC which causes the TC/LUC to gradually disengage from the engaged state prior to the calibration procedure, while monitoring the slip rate (ns) during said gradual disengagement. This process of gradual separation continues until a slip occurrence is detected in step S1B, i.e. a value of ns deviating from 0. In practice, this may mean that the slip rate exceeds the detection accuracy, i.e. the accuracy with which the slip rate is measured.

In step S2A, a second calibration phase is entered wherein feedback control is enabled to determine a representative value of a feedback control signal that, in combination with the open loop control signal, causes TC/LUC to operate at a reduced slip rate. This is typically an engaged condition in which the TC/LUC operates without slip. If it is determined in step S2B that this state is reached (no option), the control flow enters a third calibration phase.

In the third calibration phase in step S3, the feedback control is disabled. Instead, the feedforward control signal is modified with a modification value based on the representative value determined in the second calibration phase. The modification value may be gradually increased from an initial modification value equal to the representative value to an excessive modification value slightly higher than the initial modification value to avoid slipping of the TC/LUC due to the normal torque value change.

In step S4, a timer is activated to postpone a subsequent calibration procedure until after a predetermined time has elapsed. Optionally, there may be no timer and the calibration procedure may be initiated upon detection of a start condition indicating improper calibration of the drive train. Upon detection of such a condition, the operation of the timer may also be overruled.

It is noted that the calibration procedure described herein is particularly suitable for being applied in a low power mode of operation where the TC/LUC operates relatively close to its slip limit.

In the low power operating mode, a low clamping level is set for the TC/LUC and the transmission. This also means that the torque capacity of the transmission should not be set significantly higher than that of the TC/LUC, but just high enough to enable the TC/LUC to act as a torque fuse. In such operating modes, minor deviations in the actual state of these transmission components (e.g., due to production variations, wear, and temperature dependencies) can easily become dominant, such that the TC/LUC may inadvertently produce a maximum torque capacity, rather than the transmission. Accordingly, the calibration procedure is particularly relevant for low power modes of operation. If the driveline is operating in a higher power mode, a transition phase may be provided in which the degree of engagement of the TC/LUC is gradually reduced from a relatively high degree in the higher power mode to a relatively moderate degree in the lower power mode. In higher power operating modes, a larger margin may be applied between the torque capacity of the transmission and the torque capacity of the TC/LUC, so that the above-mentioned uncertainty in the actual state may be virtually ignored. For these modes of operation, manual calibration is sufficient.

It should be noted that the illustrative embodiments may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Although specific functions may be performed by respective dedicated functional elements, as an example, various functions may alternatively be performed by the same element at different points in time. Example embodiments may be implemented using a computer program product, such as a computer program tangibly embodied in an information carrier (e.g., in a machine-readable medium) for execution by, or to control the operation of, data processing apparatus (e.g., a programmable processor, a computer, or multiple computers). In an example embodiment, the machine-readable medium may be a non-transitory machine storage medium or a computer-readable storage medium.

Claims

1. A control device (80, 90, 100) for a powertrain comprising a transmission (40) and a torque converter having a lock-up clutch TC/LUC (20), the lock-up clutch TC/LUC (20) being arranged in series with a continuously variable transmission, the control device comprising a TC/LUC control signal (P) provided to control an engagement state of a lock-up clutch of the torque converter _set ) And comprising a calibration facility for calibration of the TC/LUC controller, wherein the TC/LUC controller comprises an open-loop control section (OLC) to determine the TC/LUC control signal (P) estimated to reach a predetermined engagement state _set ) Nominal control signal value (P) _f ) And wherein the TC/LUC controller further comprises a closed-loop control section (CLC) that, in an active state of the closed-loop control section, causes the TC/LUC controller to issue the TC/LUC control signal (P) having a value to minimize a deviation between an actual engagement state and the predetermined engagement state _set ) Wherein the control device is operable in a calibration mode comprising at least the following calibration phases:

-a first calibration phase, in which the closed-loop control section (CLC) is disabled and the open-loop control section is to be disabledThe value of the TC/LUC control signal is gradually modified from an initial open-loop control signal value until the TC/LUC control signal assumes a stop value (T) for which it is detected that the TC/LUC assumes a slip mode of operation _stop ) Said initial open loop control signal value being said TC/LUC control signal (P) immediately prior to entering said calibration mode _set ) The value of (a) is,

-a second calibration phase entered after said detection, wherein said closed-loop control section (CLC) is enabled to control said TC/LUC control signal (P) _set ) From the stop value (P) _stop ) Adapted to said TC/LUC to reach said determined intermediate value (P) of the predetermined engagement state _c,lock )，

-a third calibration phase entered after detection of said predetermined engagement state, wherein said closed-loop control section is disabled and said open-loop control section is dependent on said intermediate value (P) _c,lock ) And said nominal control signal value (P) _f ) The difference between them is calibrated.

2. The control apparatus according to claim 1, wherein the predetermined engagement state is a state having a minimum degree of engagement of the TC/LUC required to maintain a slip-free operation at a current value of torque transmitted by the TC/LUC.

3. Control arrangement according to claim 1 or 2, characterized in that the calibration facility calibrates the open-loop control section in its third calibration phase to provide a TC/LUC control signal (P) maintaining the TC/LUC in a stronger engagement state than the predetermined engagement state _set )。

4. The control apparatus of claim 3, wherein the calibration facility has a transition period and a plateau period in a third calibration phase thereof, the transition period enabling the open-loop control section to cause the engagement state of the clutch to gradually change from the predetermined engagement state to the stronger engagement state, the calibration facility causing the open-loop control section to maintain the clutch in the stronger engagement state in the plateau period.

5. The control apparatus of claim 1, wherein the closed-loop control section comprises an integral action control component, and wherein the intermediate value of the control signal is determined using the integral action control component.

6. A control method for controlling a torque converter having a lock-up clutch (TC/LUC) arranged in series with a transmission (CVT) in a powertrain includes providing a TC/LUC control signal (P) to the TC/LUC _set ) To control the engaged state of the TC/LUC, wherein the control signal is obtained by closed-loop control, open-loop control, or by a combination of open-loop and closed-loop control, the method comprising a calibration procedure having the steps of:

-providing an open loop based control signal to the TC/LUC with feedback control disabled, the open loop based control signal causing the TC/LUC to gradually disengage from an engaged state prior to the calibration procedure until it is detected that the TC/LUC assumes a slip mode of operation;

-after detection of said slipping mode of operation, enabling feedback control to determine said TC/LUC control signal (P) for which it is detected that said TC/LUC (20) assumes a predetermined engagement state _set ) Middle value of (P) _c,lock )，

-disabling feedback control and enabling open loop control to be based on the determined intermediate value (P) _c,lock ) And a predetermined nominal value (P) expected to achieve said predetermined engagement state _f ) The difference between them to control the engagement state of the TC/LUC (20).

7. The control method of claim 6 wherein the predetermined engagement state is a minimum degree of engagement of the TC/LUC required to maintain a slip-free operation at a current value of torque transmitted by the TC/LUC.

8. A control method according to claim 6 or 7, characterised in that the calibration procedure is initiated upon detection of an enabling condition requiring at least that the TC/LUC is in a locked mode.

9. The control method of claim 8, wherein the enabling condition comprises expiration of a predetermined time interval (g) that has elapsed since completion of a previous calibration procedure.

10. A control method according to claim 6, characterized in that the occurrence of slip is detected as a slip rate (n) _s ) As a function of the speed (n) at the input of the TC/LUC _e ) And the rotational speed (n) at the output _t )。

11. Control method according to claim 10, characterized in that the slip ratio (n) _s ) Is for the speed (n) at the input of the TC/LUC _e ) Subtracting the speed of rotation (n) at the output of the TC/LUC _t ) And the obtained value.

12. Control method according to claim 10, characterized in that the slip ratio (n) _s ) Is for the speed (n) at the input of the TC/LUC _e ) Divided by the speed of rotation (n) at the output of the TC/LUC _t ) The difference therebetween.

13. The control method of claim 6, wherein an integral action control component is used to determine the control signal for the closed-loop control, and an intermediate value of the control signal is determined using the integral action control component.

14. A powertrain in a continuously variable transmission system comprising a torque converter/lock-up clutch (TC/LUC), a forward-neutral-reverse clutch (DNR) and a variator, comprising a control device according to any one of claims 1 to 5.