Vehicle torsional vibration control method and device

Abstract

To address an issue that executing vibration control to control vibration by correcting output torque of an internal combustion engine when detecting torsional vibration in a drive system during non-lockup operation causes deterioration of fuel economy and an increase in an engagement shock when the vibration control overlaps with lockup clutch engagement operation.SOLUTION: When a difference between an engine rotation speed and a turbine rotation speed becomes equal to or less than a threshold (time t3) after lockup operation is started (time t2) by a lockup instruction, an engagement completion timer is started. When a predetermined delay time has elapsed (time t4), a fourth operation permission flag is turned on, and vibration control is permitted.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a torsional vibration damping technique for actively damping torsional vibrations occurring in a vehicle drivetrain by correcting the output torque of an internal combustion engine. [Background technology]

[0002] In a vehicle that runs by transmitting the output of an internal combustion engine to the drive wheels via a transmission, torsional vibrations can occur in the vehicle's drive system (powertrain) due to, for example, fluctuations in the output torque of the internal combustion engine, resulting in unpleasant behavior such as front-to-rear vibration of the vehicle body.

[0003] Patent Document 1 describes a torsional vibration damping control that detects or predicts the occurrence of such torsional vibration (called jerk in Patent Document 1) and cancels the torsional vibration by correcting the output torque of the internal combustion engine using a feedback method or a feedforward method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-77881 Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned conventional technology does not take into consideration the fact that the drivetrain includes a torque converter or a lock-up clutch, and vibration damping control is always performed regardless of the state of the lock-up clutch. As a result, unnecessary output torque correction can result in a deterioration in fuel economy, and the execution of output torque correction for vibration damping control during the lock-up clutch engagement operation can increase engagement shock. [Means for solving the problem]

[0006] This invention relates to a torsional vibration damping method for a vehicle, which damps torsional vibration in a drivetrain including an internal combustion engine, a stepped automatic transmission, and drive wheels by correcting the output torque of the internal combustion engine using a feedback system, comprising: The vibration damping control by the output torque correction is permitted on the condition that the lock-up clutch of the torque converter included in the stepped automatic transmission is in lock-up.

[0007] During lockup, the torque converter is essentially not functioning, which can lead to the risk of torsional vibration. Therefore, by enabling vibration damping control, vibration is damped by correcting the output torque when torsional vibration is detected. On the other hand, during non-lockup, torsional vibration is unlikely to occur due to the action of the torque converter, and unnecessary vibration damping control is not executed even if, for example, torsional vibration is erroneously detected. [Effects of the Invention]

[0008] According to this invention, by permitting vibration damping control on the condition that the lockup clutch is in lockup, shock caused by vibration damping control being executed simultaneously while the lockup clutch is engaged is eliminated, and deterioration of fuel economy due to output torque correction when the lockup clutch is not in lockup can be avoided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating the configuration of a drive system of a vehicle according to an embodiment of the present invention; [Figure 2] FIG. 4 is an explanatory diagram showing the relationship between the cooling water temperature and the first operation permission flag. [Figure 3] FIG. 4 is an explanatory diagram showing the relationship between a shift period and a second operation permission flag in a stepped automatic transmission. [Figure 4] FIG. 4 is an explanatory diagram showing the relationship between gear positions in a stepped automatic transmission and a third operation permission flag. [Figure 5] 6 is a time chart showing an example of the operation of the fourth operation permission flag and the like when the lockup clutch performs an engagement operation. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows the configuration of a drivetrain for a vehicle according to the embodiment. This embodiment is a rear-wheel drive vehicle. A transmission 2 is connected to an internal combustion engine 1, and the output of the transmission 2 drives drive wheels 4 via a final drive unit 3. The transmission 2 is a stepped automatic transmission. Although not shown in detail, the automatic transmission 2 includes a torque converter 21 having a lock-up clutch 22 and a stepped speed change mechanism 23 including a planetary gear mechanism and multiple friction engagement elements (clutches and / or brakes). The lock-up clutch 22 and speed change mechanism 23 of the automatic transmission 2 are controlled by an automatic transmission controller 5. For example, when a selector (not shown) selects the automatic shift range (the so-called D range), an appropriate gear is selected based on a predetermined shift map, with accelerator pedal depression and vehicle speed as parameters, and gears are automatically changed. A vehicle speed signal and an accelerator pedal depression signal are input to the automatic transmission controller 5 directly or indirectly via another controller.

[0011] The lock-up clutch 22 is a clutch mechanism that directly connects the input side (pump impeller) and output side (turbine runner) of the torque converter 21, and its engagement and disengagement are controlled based on various parameters including vehicle speed.

[0012] In one embodiment, the internal combustion engine 1 is a four-stroke, spark-ignition internal combustion engine, or so-called gasoline engine. The internal combustion engine 1 is controlled by an engine controller 6. The AT controller 5 and the engine controller 6 are connected to each other via an on-board network 7 (e.g., CAN communication) and transmit and receive necessary signals. The engine controller 6 receives detection signals from various sensors, such as a crank angle sensor 11 for detecting the engine speed, an air flow meter 12 for detecting the intake air amount corresponding to the load, a water temperature sensor 13 for detecting the coolant temperature, an accelerator position sensor 14 for detecting the accelerator pedal position (depression amount) operated by the driver, and an air-fuel ratio sensor 15 for detecting the exhaust air-fuel ratio, either directly or via other controllers. Based on these detection signals, the engine controller 6 optimally controls the fuel injection amount and injection timing of the fuel injection valve, the ignition timing of the spark plug, the throttle valve opening, and the like.

[0013] Here, the engine controller 6 detects the occurrence of torsional vibration in the drivetrain from fluctuations in the rotational speed of the crankshaft detected by the crank angle sensor 11. Then, to cancel out this torsional vibration, the engine controller 6 performs so-called active vibration suppression by correcting the output torque of the internal combustion engine 1 using a feedback method. In one embodiment, the output torque correction for vibration suppression is achieved by reducing the torque through ignition timing retardation.

[0014] Such output torque correction of the internal combustion engine 1 is a factor that deteriorates the fuel efficiency of the vehicle, so vibration damping control for torsional vibrations by output torque correction of the internal combustion engine 1 is permitted / prohibited according to predetermined conditions. When vibration damping control is not permitted (in other words, when it is prohibited), output torque correction is not performed even if the occurrence of torsional vibrations is detected.

[0015] Next, specific permission / prohibition of vibration suppression control in one embodiment will be described with reference to Figures 2 to 5. The final permission condition for vibration suppression control is the "AND" of several individual permission conditions (operation permission flags) below.

[0016] First, permission for vibration suppression control is limited by the coolant temperature. FIG. 2 shows the relationship between the coolant temperature (a) of the internal combustion engine 1 and the on / off state of a first operation permission flag (b), which indicates permission / prohibition based on the coolant temperature. When the first operation permission flag is on, execution of vibration suppression control by output torque correction for torsional vibration is permitted. As shown in the figure, when the coolant temperature is equal to or lower than a predetermined upper limit temperature TwH and equal to or higher than a predetermined lower limit temperature TwL, the first operation permission flag is on, and execution of vibration suppression control is permitted. In other words, when torsional vibration is detected from fluctuations in rotation speed, active vibration suppression is performed by correcting the output torque of the internal combustion engine 1.

[0017] The upper limit temperature TwH is set in accordance with a temperature condition where there is a large variation in the combustion torque of the internal combustion engine 1. In one embodiment, the upper limit temperature TwH is set to, for example, 40°C to 60°C, lower than the warm-up completion temperature of the internal combustion engine 1. Depending on the mode of the drive system including the internal combustion engine 1, the upper limit temperature TwH may be set higher than the warm-up completion temperature.

[0018] When the coolant temperature is lower than the upper limit temperature TwH, the combustion stability of the internal combustion engine 1 is low and the combustion torque varies greatly, which makes it easy for torsional vibrations to occur in the drivetrain. Therefore, by enabling vibration damping control, vibration damping is performed by correcting the output torque when torsional vibrations are detected. On the other hand, when the coolant temperature is higher than the upper limit temperature TwH, vibration damping control is not performed, even if torsional vibrations are erroneously detected, for example.

[0019] Furthermore, when the coolant temperature is lower than a lower limit temperature TwL, which is lower than the upper limit temperature TwH, the first operation permission flag is turned off. This lower limit temperature TwL is set to a temperature relatively lower than the temperature condition under which lockup of the lockup clutch 22 is prohibited. Therefore, when the coolant temperature is lower than the lower limit temperature TwL, torsional vibration can be suppressed by the action of the torque converter 21, and therefore vibration suppression control by output torque correction of the internal combustion engine 1 is prohibited.

[0020] Second, vibration damping control by output torque correction of the internal combustion engine 1 is prohibited during the shifting period of the transmission mechanism 23 of the automatic transmission 2. As shown in Fig. 3, the shifting in progress determination flag (a) is turned on when a shift command is output to the transmission mechanism, and is turned off when the shifting is completed. The second operation permission flag (b) is turned off during the shifting period from the start of the shifting to the completion of the shifting, and vibration damping control by output torque correction is prohibited.

[0021] If torsional vibration is detected during a gear shift and output torque correction of the internal combustion engine 1 is performed, there is a concern that gear shift shock may worsen. Therefore, during a gear shift, the second operation permission flag is turned off, and output torque correction is not performed.

[0022] Third, vibration suppression control is permitted only at specific gear positions where torsional vibration is likely to occur. Figure 4 shows the relationship between the gear positions (a) of the automatic transmission 2 and the third operation permission flag (b). As shown in Figure 4, the third operation permission flag is turned on when the automatic transmission 2 is in one or more predetermined gear positions.

[0023] When the gear position in the transmission mechanism 23 is different, the configuration of the drive system that is actually involved in torsional vibrations is different. Therefore, even if the combustion torque variation of the internal combustion engine 1 is the same, there may be gear positions where torsional vibrations occur significantly and gear positions where torsional vibrations do not occur very much. Therefore, by prohibiting output torque correction at unnecessary gear positions, deterioration in fuel economy is minimized. Note that the gear positions shown in FIG. 4 are merely an example.

[0024] Furthermore, in this embodiment, vibration suppression control is permitted on the condition that the lockup clutch 22 is in lockup. That is, a fourth operation permission flag is on when the lockup clutch 22 is in lockup, and the fourth operation permission flag is off when the lockup clutch 22 is not in lockup. FIG. 5 is a time chart showing an example of the operation when the lockup clutch 22 transitions from a released state to an engaged state, and shows, from top to bottom, (a) the fourth operation permission flag, (b) the engine speed (the rotational speed of the input side of the torque converter 21), (c) the turbine speed (the rotational speed of the output side of the torque converter 21), (d) the lockup command, (e) the engagement completion timer, and (f) the lockup determination flag. This example time chart shows the behavior when acceleration is performed from a released state of the lockup clutch 22, and lockup occurs when the vehicle speed and other factors satisfy predetermined lockup conditions.

[0025] That is, acceleration begins at time t1, and the engine speed and turbine speed gradually increase. Thereafter, at time t2, a predetermined lockup condition is met and a lockup command is output. This initiates the engagement operation of lockup clutch 22. After the engagement operation begins, as the torque transmission capacity of lockup clutch 22 gradually increases, the input-side engine speed and the output-side turbine speed gradually approach each other. The differential speed, which is the difference between the engine speed and the turbine speed (more specifically, its absolute value), is compared with a relatively small threshold value at which it can be assumed that lockup clutch 22 is nearly engaged.

[0026] At time t3, the differential rotation speed becomes equal to or less than the threshold value, and an engagement completion timer that measures a predetermined time is started at this time t3. The engagement completion timer is set with a predetermined time (i.e., delay time) required from when the differential rotation speed becomes the threshold value until when the engagement of lock-up clutch 22 can be considered complete.

[0027] At time t4, the engagement completion timer expires, and the lock-up determination flag is turned on. At the same time, the fourth operation permission flag is turned on.

[0028] Therefore, assuming that the other operation permission flags (the first operation permission flag based on the cooling water temperature, the second operation permission flag related to the shift period, and the third operation permission flag related to the gear stage) are already on, at time t4 when the differential rotation speed becomes below the threshold value and a predetermined delay time has elapsed, vibration damping control by output torque correction of the internal combustion engine 1 will finally be permitted.

[0029] Even when lock-up clutch 22 begins to engage, a certain degree of slippage is permitted until lock-up clutch 22 is fully engaged, so that generally, front-to-rear vibration of the vehicle body due to torsional vibration is unlikely to occur. Therefore, by not unnecessarily executing vibration suppression control by output torque correction, deterioration of fuel economy can be suppressed.

[0030] Furthermore, if output torque correction of internal combustion engine 1 is executed as vibration damping control during the engagement operation of lockup clutch 22, it may worsen the engagement shock of lockup clutch 22. In the above embodiment, vibration damping control is prohibited until time t4 when the differential rotation speed becomes equal to or less than the threshold value and the predetermined delay time has elapsed, so the timing of vibration damping control and the engagement operation do not overlap, and it is possible to avoid worsening of the engagement shock due to the two overlapping.

[0031] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, the conditions for permitting / prohibiting vibration suppression control indicated by the first to third operation permission flags other than the fourth operation permission flag related to lockup clutch 22 are optional and not necessarily required. Furthermore, some of these permitting / prohibiting conditions can be applied in appropriate combination with permitting / prohibiting conditions related to lockup. [Explanation of symbols]

[0032] 1...Internal combustion engine 2...Gearbox 3...Final reduction gear 4...Drive wheels 5...AT controller 6...Engine controller 21...Torque converter 22...Lock-up clutch

Claims

1. A method for damping torsional vibration of a vehicle, which damps torsional vibration of a drivetrain including an internal combustion engine, a stepped automatic transmission, and drive wheels by correcting output torque of the internal combustion engine using a feedback system, comprising: A method for damping torsional vibration of a vehicle, which permits vibration damping control by output torque correction on the condition that a lock-up clutch of a torque converter included in the stepped automatic transmission is in lock-up.

2. After the start of the engagement operation of the lock-up clutch, the vibration damping control is prohibited until the lock-up is completed.

2. The method for damping torsional vibration of a vehicle according to claim 1.

3. After the start of the engagement operation of the lock-up clutch, when a predetermined time has elapsed since the differential rotation speed of the lock-up clutch becomes equal to or less than a predetermined threshold, it is determined that the lock-up has been completed.

3. The method for damping torsional vibration of a vehicle according to claim 2.

4. The output torque correction is performed by retarding the ignition timing.

2. The method for damping torsional vibration of a vehicle according to claim 1.

5. When the cooling water temperature of the internal combustion engine is lower than a predetermined lower limit temperature, the vibration damping control by the output torque correction is prohibited, The lower limit temperature is set to a temperature lower than a lock-up prohibition temperature of the lock-up clutch.

2. The method for damping torsional vibration of a vehicle according to claim 1.

6. a predetermined upper limit temperature higher than the lower limit temperature is set, and when the cooling water temperature is higher than this upper limit temperature, vibration suppression control by the output torque correction is prohibited; The upper limit temperature is set in accordance with a temperature condition where the combustion torque of the internal combustion engine varies greatly.

6. The method for damping torsional vibration of a vehicle according to claim 5.

7. prohibiting vibration damping control by output torque correction during a shift from the start of shifting to the completion of shifting of the stepped automatic transmission; 2. The method for damping torsional vibration of a vehicle according to claim 1.

8. Furthermore, the vibration damping control by the output torque correction is permitted on the condition that the stepped automatic transmission is in one or more predetermined gear stages.

2. The method for damping torsional vibration of a vehicle according to claim 1.

9. a detection unit that detects occurrence of torsional vibration in a drivetrain including an internal combustion engine, a stepped automatic transmission, and drive wheels; a control unit that corrects an output torque of the internal combustion engine by a feedback method so as to damp the torsional vibration when the torsional vibration is detected; A torsional vibration damping device for a vehicle comprising: The control unit permits vibration damping control by output torque correction on the condition that a lock-up clutch of a torque converter included in the stepped automatic transmission is in lock-up.

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