Vehicle control device

Abstract

To provide a vehicle control device capable of appropriately suppressing vibration of a vehicle even when traveling on an ascent or descent.SOLUTION: An electronic control device 80 comprises: a vibration generation condition determination section 88 which determines whether all vibration generation conditions are satisfied; a resonance determination section 90 which determines whether an engine 12 and an automatic transmission 22 are in resonance when the vibration generation condition determination section 88 makes an affirmative determination; a slope estimation section 92 which estimates a slope of a road on which a vehicle 10 travels; and a resonance suppression control section 94 which places an LU clutch 36 into a slip state to suppress resonance when the resonance determination section 90 makes an affirmative determination. The resonance suppression control section 94 corrects a required slip period Tst and a target differential rotation speed Nst of the slip state of the LU clutch 36 in accordance with the estimated slope Slo. Accordingly, the slip state is increased on an ascent where vibration discomfort becomes significant and is decreased on a descent where the vibration discomfort is reduced, thereby appropriately suppressing vibration.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vehicle control device for suppressing vehicle vibration.

Background Art

[0002] Vehicles equipped with an engine, a transmission capable of selectively establishing a plurality of gear stages with different gear ratios, and a torque converter with a lock-up clutch for transmitting the torque of the engine to the transmission are well known. Patent Document 1 discloses a technique for suppressing vehicle vibration by controlling a lock-up clutch in a slip state for a short time when vehicle vibration caused by engine torque fluctuation is detected.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the slip control of the lock-up clutch for suppressing vehicle vibration has conventionally been premised on a flat road, and control amounts such as the period of the slip state and the slip amount are determined according to the acceleration estimated from the torque and vehicle speed. However, in the case of a slope road, since the acceleration changes according to the slope, there is a problem that even if the generated vibration level is the same, the sense of discomfort is different and the control is not appropriate according to the slope.

[0005] The present invention has been made against the background of the above circumstances, and an object thereof is to provide a vehicle control device capable of appropriately suppressing vehicle vibration even when driving on a slope road.

Means for Solving the Problems

[0006] The gist of the present invention is a control device for a vehicle including: (a) an engine, a transmission capable of selectively establishing a plurality of gear stages with different gear ratios, and a torque converter including a lock-up clutch for transmitting the torque of the engine to the transmission, and (b) a vibration generation condition determination unit that determines whether all of the vibration generation conditions consisting of the lock-up clutch being in an engaged state, a predetermined gear stage being established in the transmission, and an operating point determined according to the rotational speed and load of the engine belonging to a predetermined region are satisfied; a resonance determination unit that determines whether the engine and the transmission resonate when an affirmative determination is made by the vibration generation condition determination unit; a slope estimation unit that estimates the slope of the road on which the vehicle travels; and a resonance suppression control unit that puts the lock-up clutch in a slip state to suppress resonance when an affirmative determination is made by the resonance determination unit, and (c) the resonance suppression control unit corrects the duration and slip amount of the slip state according to the slope.

Advantages of the Invention

[0007] According to the present invention, the control device includes a vibration generation condition determination unit that determines whether all of the vibration generation conditions consisting of the lock-up clutch being in an engaged state, a predetermined gear stage being established in the transmission, and an operating point determined according to the rotational speed and load of the engine belonging to a predetermined region are satisfied; a resonance determination unit that determines whether the engine and the transmission resonate when an affirmative determination is made by the vibration generation condition determination unit; a slope estimation unit that estimates the slope of the road on which the vehicle travels; and a resonance suppression control unit that puts the lock-up clutch in a slip state to suppress resonance when an affirmative determination is made by the resonance determination unit, and the resonance suppression control unit corrects the duration and slip amount of the slip state according to the slope. As a result, since the duration and the slip amount are increased on an ascending slope where the discomfort with vibration increases and decreased on a descending slope where it decreases, vehicle vibration can be appropriately suppressed even when traveling on slopes.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Examples

[0010] FIG. 1 is a diagram for explaining the schematic configuration of a vehicle 10 to which the present invention is applied, and is also a diagram for explaining the main part of the control functions for various controls in the vehicle 10. In FIG. 1, the vehicle 10 includes an engine 12 as a power source, drive wheels 14, and a power transmission device 16 provided in the power transmission path between the engine 12 and the drive wheels 14. The power transmission device 16 includes a torque converter 20, an automatic transmission 22, etc. in a case 18 as a non-rotating member attached to the vehicle body. Further, the power transmission device 16 includes a propeller shaft 26 connected to the transmission output shaft 24 which is the output rotating member of the automatic transmission 22, a differential 28 connected to the propeller shaft 26, and left and right drive shafts 30 connected to the differential 28, etc.

[0011] The engine 12 is controlled such that the engine torque Te which is the output torque of the engine 12 is controlled by the engine control device 40 provided in the vehicle 10 being controlled by an electronic control device 80 described later.

[0012] The torque converter 20 is disposed in the power transmission path between the engine 12 and the automatic transmission 22, and is connected to the engine 12 via the crankshaft 32. The torque converter 20 includes a pump impeller 20p, a turbine impeller 20t, etc., and further includes a lock-up clutch (hereinafter referred to as the LU clutch) 36 that connects the pump impeller 20p and the turbine impeller 20t.

[0013] The automatic transmission 22 is connected to the torque converter 20 via the input shaft 34. The automatic transmission 22 is a known planetary gear type stepped transmission that includes, for example, a plurality of sets of planetary gear devices and a plurality of hydraulic engagement devices CB such as clutches and brakes, and can selectively establish a plurality of gear stages with different gear ratios.

[0014] The vehicle 10 includes an electronic control unit 80 as a controller of the vehicle 10.

[0015] Various signals etc. (for example, the engine rotational speed Ne (rpm), the turbine rotational speed Nt (= AT input rotational speed Ni), the AT output rotational speed No (rpm) corresponding to the vehicle speed V, the accelerator opening pap (%)) based on the detection values by the engine rotational speed sensor 60, the turbine rotational speed sensor 62, the output rotational speed sensor 64, the accelerator opening sensor 66, etc. provided in the vehicle 10 are respectively supplied to the electronic control unit 80. The accelerator opening pap corresponds to the required driving torque of the driver for the vehicle 10.

[0016] Various command signals (for example, the engine control command signal Se for controlling the engine 12, the hydraulic control command signal Sat for controlling the operating state of the engagement device CB, the hydraulic control command signal Slu for controlling the operating state of the LU clutch 36, etc.) are respectively output from the electronic control unit 80 to the engine control unit 40, the hydraulic control circuit 50, etc. provided in the vehicle 10.

[0017] The electronic control unit 80 functionally includes an engine control unit 82, a transmission control unit 84, an LU clutch control unit 86, a vibration generation condition determination unit 88, a resonance determination unit 90, and a gradient estimation unit 92. Further, the LU clutch control unit 86 functionally includes a resonance suppression control unit 94.

[0018] The engine control unit 82 controls the engine 12 so as to obtain the required engine torque Te. The engine control unit 82 calculates the required drive torque Tdem by applying the accelerator opening pap and the vehicle speed V to a predetermined drive force map. The engine control unit 82 outputs an engine control command signal Se to the engine control device 40 to obtain an engine torque Te that realizes the required drive torque Tdem.

[0019] The transmission control unit 84 executes transmission control of the automatic transmission 22. For example, the transmission control unit 84 determines the gear position POSsh of the automatic transmission 22 using, for example, a shift map that is a predetermined relationship. The transmission control unit 84 outputs a hydraulic control command signal Sat to the hydraulic control circuit 50 to switch the operating state of the engagement device CB so as to form the determined gear position POSsh.

[0020] The LU clutch control unit 86 determines the operating region by applying the vehicle running state represented by the required drive torque Trdem calculated from the actual vehicle speed V and the accelerator opening pap to a predetermined lock-up operation region map, and outputs a hydraulic control command signal Slu to the hydraulic control circuit 50 so that the operating state of the LU clutch 36 corresponding to the determined operating region is realized. The operating state of the LU clutch 36 is an open state in which the LU clutch 36 is released, a slip state in which the LU clutch 36 is slipped to a set slip amount, and an engaged state in which the LU clutch 36 is engaged.

[0021] FIG. 2 is a flowchart for explaining the main part of the control operation for suppressing vibrations of the vehicle 10 performed by the vibration generation condition determination unit 88, the resonance determination unit 90, the slope estimation unit 92, and the resonance suppression control unit 94, which are functionally provided in the electronic control device 80. FIG. 3 is an example of a time chart corresponding to the control operation of FIG. 2. Hereinafter, the control operation will be described with reference to FIG. 3 along the processing steps of FIG. 2.

[0022] In step S10 of FIG. 3 (hereinafter, steps will be omitted), the vibration generation condition determination unit 88 determines whether or not all of the "vibration generation conditions" under which the vehicle 10 vibrates due to resonance detected by the resonance determination unit described later are satisfied. The "vibration generation conditions" are: (A) the LU clutch 36 is in the engaged state; (B) the gear position POSsh of the automatic transmission 22 is within a predetermined gear position range POSshA; (C) the operating point determined by the engine rotational speed Ne and the engine load belongs to a predetermined region Ae; (D) the accelerator opening pap is equal to or greater than a predetermined opening papA; (E) the vehicle speed V is equal to or less than a predetermined speed Va. Note that depending on the vehicle conditions, the conditions (D) and (E) are not essential and are preferably selected according to the target vehicle.

[0023] If the determination in S10 is negative, this routine is terminated. If the determination in S10 is positive, that is, if the vibration generation condition determination unit 88 determines that the "vibration generation conditions" are satisfied, then in S20 corresponding to the resonance determination unit 90, it is determined whether or not the engine 12 and the automatic transmission 22 are in resonance. When the LU clutch 36 is in the engaged state, the crankshaft 32 of the engine 12 and the input shaft 34 of the automatic transmission 22 are fastened. In this state, if the frequency of the torque fluctuation of the engine 12 coincides with the torsional first natural frequency of the automatic transmission 22, the engine 12 and the automatic transmission 22 are in resonance. The resonance determination unit 90 calculates the rotational speed difference Ndt, which is the difference between the engine rotational speed Ne and the product of the AT output rotational speed No and the reduction ratio of the gear position POSsh, and determines whether or not resonance has occurred based on whether or not the absolute value of the rotational speed difference Ndt is equal to or greater than a predetermined threshold value Nlt. If resonance occurs, the resonance occurrence flag VF is set to ON (VF = 1).

[0024] When the determination at S20 is negative, this routine is terminated. When the determination at S20 is affirmative, that is, when the resonance determination unit 90 determines that resonance has occurred and the resonance occurrence flag is ON (VF = 1), in S30 corresponding to the resonance suppression control unit 94, the LU clutch 36 is put into a slip state, and resonance suppression control for suppressing resonance is started, and the suppression control flag SF is set to ON (SF = 1).

[0025] In FIG. 3, the period from time t0 to time t1 indicates the control operation up to the above S30. Vehicle vibration occurs at time t0, and since the absolute value of the rotational speed difference Ndt becomes equal to or greater than the threshold value Nlt at time t1, the resonance determination unit 90 determines that resonance has occurred (resonance occurrence flag VF = 1), and in response to this, the resonance suppression control by the resonance suppression control unit 94 is started (suppression control flag SF = 1).

[0026] Also, the operation from time t1 to time t3 in FIG. 3 corresponds to the control operation of the resonance suppression control executed by the resonance suppression control unit 94. During the period from time t2 to time t3 after a predetermined delay period Tdl determined in advance design-wise or experimentally from time t1 in FIG. 3, the LU clutch 36 is put into a slip state, thereby suppressing vehicle vibration. The duration of the slip state of this LU clutch 36 is set as the required slip period Tst. Also, the actual differential rotational speed Ns (= engine rotational speed Ne - turbine rotational speed Nt), which is the input / output rotational speed difference of the LU clutch 36 in the slip state, that is, the slip amount between the input and output, is controlled such that it becomes the set target differential rotational speed Nst by the resonance suppression control unit 94 outputting a hydraulic control command signal Slu to the hydraulic control circuit 50. In FIG. 3, the engine rotational speed Ne is shown by a solid line and the turbine rotational speed Nt is shown by a dashed-dotted line.

[0027] The aforementioned required slip period Tst is calculated by the following equation (1) including the correction coefficient αt, and the target differential rotational speed Nst is calculated by the following equation (2) including the correction coefficient αn. Required slip period Tst = Optimal required slip period Tsta × αt ···(1) Target differential rotation speed Nst = Optimal target differential rotation speed Nsta × αn ···(2) Here, the optimal required slip period Tsta and the optimal target differential rotation speed Nsta are the optimal values of the duration and differential rotation speed of the slip state required for suppressing vehicle vibration. For example, they are obtained in advance by design or experiment from the estimated acceleration calculated from the transition of the engine torque Te and vehicle speed V, respectively. Also, the correction coefficient αt and the correction coefficient αn are coefficients provided to appropriately correct the slip period and differential rotation speed according to other conditions.

[0028] Returning to FIG. 2, in S40 corresponding to the resonance suppression control unit 94, the slope of the road on which the vehicle 10 travels is estimated, that is, the estimated slope Slo is calculated. As shown in the upper right blowout in the drawing of FIG. 2, for example, the flat road acceleration Af obtained by dividing the driving torque applied to the vehicle 10 by the vehicle mass and the actual acceleration Ar obtained from the vehicle speed change ΔV in a predetermined period Δt are applied to the slope estimation map MAP1, and the estimated slope Slo is calculated.

[0029] Next, in S50 corresponding to the resonance suppression control unit 94, the above-described correction coefficient αt and correction coefficient αn corresponding to the estimated slope Slo calculated in S40 are calculated. As shown in the lower right blowout in the drawing of FIG. 2, the estimated slope Slo is applied to the slip period correction coefficient map MAP2 and the target differential rotation speed correction coefficient map MAP3, and the correction coefficient αt and the correction coefficient αn are calculated. Each map is configured to calculate a correction coefficient that is greater than 1 and increases as the absolute value of the slope of the uphill gradient increases because the discomfort to vibration becomes greater when the estimated slope Slo is a positive value, that is, an uphill gradient, and to calculate a correction coefficient that is less than 1 and decreases as the absolute value of the slope of the downhill gradient increases because the discomfort to vibration becomes smaller when the estimated slope Slo is a negative value, that is, a downhill gradient.

[0030] Next, in S60 corresponding to the resonance suppression control unit 94, an optimal required slip period Tsta and an optimal target differential rotation speed Nsta are obtained, and these, together with the correction coefficient αt and the correction coefficient αn calculated in S50, are applied to equations (1) and (2) to calculate a required slip period Tst and a target differential rotation speed Nst.

[0031] Then, resonance suppression control is performed from S70 to S90 corresponding to the resonance suppression control unit 94 (corresponding to the period from the time point t1 to the time point t3 in FIG. 3). At the time point t2, which is after a predetermined delay period Tdl from the time point t1 in FIG. 3, the LU clutch 36 is shifted to a slip state. Next, in the determination of S80, it is determined whether or not the required slip period Tst has ended. If the determination in S80 is negative, the process returns to S70 and the resonance suppression control is continued. If the determination in S80 is positive, the resonance suppression control ends, that is, the LU clutch 36 is shifted from the slip state to the engaged state, the suppression control flag SF is turned OFF (SF = 0), and this routine ends (see t3 in FIG. 3).

[0032] As described above, according to this embodiment, the electronic control device 80 includes a vibration generation condition determination unit 88 that determines whether all of the vibration generation conditions, which include the LU clutch 36 being in the engaged state, the gear position POSsh of the automatic transmission 22 being within a predetermined gear position range POSshA, and the operating point determined by the engine rotational speed Ne and the engine torque Te belonging to a predetermined region Ae, are satisfied; a resonance determination unit 90 that determines whether the engine 12 and the automatic transmission 22 resonate when a positive determination is made by the vibration generation condition determination unit 88; a gradient estimation unit 92 that estimates the gradient of the road on which the vehicle 10 travels; and a resonance suppression control unit 94 that, when a positive determination is made by the resonance determination unit 90, puts the LU clutch 36 in a slip state to suppress resonance. The resonance suppression control unit 94 corrects the required slip period Tst and the target differential rotation speed Nst according to the estimated gradient Slo. As a result, the required slip period Tst and the target differential rotation speed Nst are increased on an uphill gradient where the discomfort with vibration increases and decreased on a downhill gradient where it decreases, so that vehicle vibration can be appropriately suppressed even when driving on slopes.

[0033] Note that the above is merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0034] 10: Vehicle 12: Engine 20: Torque converter 22: Automatic transmission (transmission) 36: LU clutch (lock-up clutch) 80: Electronic control unit (control unit) 88: Vibration generation condition determination unit 90: Resonance determination unit 92: Gradient estimation unit 94: Resonance suppression control unit Ne: Engine rotational speed Nst: Target differential rotational speed POSsh: Gear position Slo: Estimated gradient (gradient) Te: Engine torque Tst: Required slip period (duration)

Claims

【Claim 1】 A control device for a vehicle, comprising: an engine; a transmission capable of selectively establishing a plurality of gear stages with different gear ratios; and a torque converter including a lock-up clutch that transmits the torque of the engine to the transmission, a vibration generation condition determination unit that determines whether all of the vibration generation conditions, which include that the lock-up clutch is engaged, that a predetermined gear stage is established in the transmission, and that an operating point determined according to the rotational speed and load of the engine belongs to a predetermined region, are satisfied; a resonance determination unit that determines whether the engine and the transmission resonate when a positive determination is made by the vibration generation condition determination unit; a gradient estimation unit that estimates the gradient of the road on which the vehicle travels; and a resonance suppression control unit that, when a positive determination is made by the resonance determination unit, puts the lock-up clutch in a slip state to suppress resonance, wherein the resonance suppression control unit corrects the duration and the slip amount of the slip state according to the gradient. A control device for a vehicle, characterized by the above.

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