Control device for four-wheel drive vehicle

Abstract

To provide a control device for a four-wheel drive vehicle, which can achieve both fuel consumption performance and NV performance by appropriately executing flex lock-up control.SOLUTION: A four-wheel drive vehicle is equipped with a torque converter that transmits engine torque to a transmission, a lock-up clutch that puts an input member and an output member of the torque converter in one of the states of engagement, disengagement, and slip-engagement, a front drive shaft that transmits the engine torque to front wheels, and a rear drive shaft that transmits the engine torque to rear wheels, and a control device for the four-wheel drive vehicle performs flex lock-up control to cause the differential rotation between the input member and the output member of the torque converter to follow a target differential rotation. The control device sets the target differential rotation based on the input rotation speed of the transmission, engine torque, and the rear input torque transmitted to the rear drive shaft, which are acquired in real time, and performs the flex lock-up control.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for a four-wheel drive vehicle, and more particularly to a control device for a four-wheel drive vehicle that executes flex lock-up control in a lock-up clutch of a torque converter.

Background Art

[0002] Patent Document 1 describes a control device for a power transmission device that includes a torque converter and a lock-up clutch, and executes acceleration flex control for controlling the differential rotation of the lock-up clutch to a target differential rotation during vehicle acceleration. The control device for the power transmission device described in Patent Document 1 sets a first target differential rotation and a second target differential rotation having a lower differential rotation than the first target differential rotation as the target differential rotation when executing the acceleration flex control, and determines an initial value of the second target differential rotation based on the first target differential rotation. Then, when a predetermined time has elapsed after starting the acceleration flex control, the second target differential rotation is gradually increased from the initial value so as to approach the first target differential rotation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The control device for a power transmission device described in the above Patent Document 1 controls a power transmission device (automatic transmission) mounted on a vehicle with front-wheel drive or rear-wheel drive, and executes acceleration flex control of a lock-up clutch. By executing the acceleration flex control by the control device for the power transmission device described in that Patent Document 1, it is possible to suppress noise and vibration such as stuffy sound, and to keep the differential rotation of the lock-up clutch low when executing the acceleration flex control. Therefore, it is possible to achieve a good balance between the fuel consumption performance and the NV performance of the vehicle. On the other hand, when such acceleration flex control (or flex lock-up control) is applied to a four-wheel drive vehicle that drives both the front and rear wheels, it may not be possible to achieve a good balance between the fuel consumption performance and the NV performance.

[0005] Generally, in a four-wheel drive vehicle, torque fluctuations in the front and rear drive shafts are factors causing stuffy sound and vibration. Therefore, various controls are designed in consideration of the input sensitivity to the torque of these front and rear drive shafts. For example, in the case of a vehicle characteristic where the input sensitivity of the torque of the rear drive shaft is higher than the input sensitivity of the torque of the front drive shaft, the control design of the flex lock-up control is performed on the premise that there is a certain torque input to the rear drive shaft. On the other hand, in a so-called standby type four-wheel drive vehicle, the input torque of the rear drive shaft becomes small in the standby state where it is in a two-wheel drive state, but the conventional flex lock-up control is not executed based on the real-time input torque of the rear drive shaft. Therefore, when the flex lock-up control is applied to a standby type four-wheel drive vehicle, the premise at the control design stage and the actual state of the rear drive shaft may deviate, and there is a possibility that the desired fuel consumption performance and NV performance cannot be obtained. The standby type four-wheel drive vehicle uses a viscous coupling or an electronically controlled coupling, etc., and in normal straight-ahead driving, it is in a two-wheel drive state with only the front wheels or the rear wheels, that is, the standby state. For example, when one of the front wheels or the rear wheels slips and a rotational difference occurs between the front and rear wheels, the coupling is engaged, or the coupling is engaged to drive in a four-wheel drive state.

[0006] The present invention has been conceived by paying attention to the above technical problems, and aims to provide a control device for a four-wheel drive vehicle that can achieve good fuel efficiency performance and NV performance for a four-wheel drive vehicle that performs flex lock-up control of a lock-up clutch provided in a torque converter.

Means for Solving the Problems

[0007] In order to achieve the above object, the present invention is equipped with an engine as a driving force source, a torque converter that transmits the output torque of the engine to a transmission, a lock-up clutch that places the input member and the output member of the torque converter in any one of an engaged state, a released state, and a slip engagement state, a front drive shaft that transmits the output torque to the front wheels, and a rear drive shaft that transmits the output torque to the rear wheels. In a control device for a four-wheel drive vehicle that executes flex lock-up control of the torque converter that causes the differential rotation between the input member and the output member to follow the target differential rotation, the four-wheel drive vehicle is controlled, and a controller that executes the flex lock-up control is provided. The controller sets the target differential rotation based on the input rotation speed, the output torque, and the rear input torque transmitted to the rear drive shaft, which are respectively calculated or acquired in real time, and executes the flex lock-up control.

Effects of the Invention

[0008] The control device for a four-wheel drive vehicle of the present invention controls a four-wheel drive vehicle equipped with a front drive shaft on the front wheel side and a rear drive shaft on the rear wheel side, and executes flex lock-up control of a lock-up clutch. By appropriately executing the flex lock-up control, the differential rotation of the lock-up clutch can be suppressed to a low level, and the loss in the torque converter can be reduced, thereby improving the fuel efficiency of a four-wheel drive vehicle having an engine as a power source. Further, in the control device for a four-wheel drive vehicle of the present invention, the input rotation speed of the transmission, the output torque of the engine, and the rear input torque transmitted to the rear drive shaft are acquired in real time, and the above-described flex lock-up control is executed based on these latest input rotation speed, output torque, and rear input torque. Therefore, it is possible to avoid the deviation between the control preconditions of the prior art and the actual rear input torque of the rear drive shaft, and appropriately execute the flex lock-up control. For example, even when a standby-type four-wheel drive vehicle is used as a control target, the flex lock-up control can be executed by appropriately reflecting torque fluctuations of the rear drive shaft based on the actual rear input torque.

[0009] Therefore, according to the control device for a four-wheel drive vehicle of the present invention, it is possible to appropriately execute the flex lock-up control of the lock-up clutch provided in the torque converter, and to achieve good balance between the fuel efficiency performance and the NV performance of the four-wheel drive vehicle.

Brief Description of the Drawings

[0010]

Figure 1

Embodiments for Carrying Out the Invention

[0011] Embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples of implementing the present invention and do not limit the present invention.

[0012] The four-wheel drive vehicle (4DW vehicle) to be controlled in the embodiment of the present invention is equipped with an engine (internal combustion engine) as a driving force source, and includes at least a torque converter, a lock-up clutch, a front drive shaft, and a rear drive shaft.

[0013] The torque converter transmits the output torque (engine torque) of the engine to an automatic transmission (AT). The lock-up clutch selectively sets the state between the input member and the output member of the torque converter to any one of engagement, release, and slip engagement. The front drive shaft transmits the engine torque to the front wheels. The rear drive shaft transmits the engine torque to the rear wheels.

[0014] The control device for a four-wheel drive vehicle in the embodiment of the present invention can control, for example, a "standby type 4WD vehicle" configured as shown in [FIG. 1] and [FIG. 6] of "Japanese Patent Application Laid-Open No. 2009-173436". The "standby type 4WD vehicle" shown in [FIG. 1] and [FIG. 6] of that "Japanese Patent Application Laid-Open No. 2009-173436" is a 4DW vehicle based on an FR (Front-engine, Rear-wheel Drive) vehicle in both cases, but may be a 4DW vehicle based on an FF (Front-engine, Front-wheel Drive) vehicle, for example.

[0015] Also, the 4DW vehicle to be controlled by the control device for a four-wheel drive vehicle in the embodiment of the present invention may have the same configuration as, for example, an "engine", "automatic transmission", "torque converter", and "lock-up clutch" as shown in [FIG. 1] and [FIG. 2] of the aforementioned "Patent Document 1", or an "engine", "transmission", "torque converter", and "lock-up clutch" as shown in [FIG. 1] of "Japanese Patent Application Laid-Open No. 2017-89781".

[0016] And the control device for a four-wheel drive vehicle in the embodiment of the present invention executes flex lock-up control of a lock-up clutch for the above-described 4WD vehicle. The flex lock-up control causes the differential rotation between the input member and the output member of the torque converter to follow the target differential rotation, and selectively sets the torque converter in any one of the engaged, released, and slip-engaged states. The details of the flex lock-up control can be described with reference to the control contents such as the "acceleration flex control" described in the above-mentioned "Patent Document 1" and the "acceleration flex control" and "deceleration flex control" described in "Japanese Patent Application Laid-Open No. 2017-89781".

[0017] FIG. 1 conceptually shows the schematic configuration of the 4DW vehicle to be controlled in the embodiment of the present invention and the content of the control executed by the control device for the four-wheel drive vehicle in the embodiment of the present invention. The 4DW vehicle (hereinafter, the vehicle) Ve shown in FIG. 1 includes a detection unit 1 and a controller 2 in order to execute the overall control of the vehicle Ve as the above-described "standby type 4WD vehicle" and the above-described flex lock-up control.

[0018] The detection unit 1 is a device or apparatus for acquiring various data and information necessary when controlling the vehicle Ve, and includes, for example, a power supply unit, a microcomputer, sensors, and input / output interfaces. In particular, the detection unit 1 in the embodiment of the present invention detects various data for executing the overall control of the vehicle Ve as the above-described "standby type 4WD vehicle" and the above-described flex lock-up control.

[0019] Specifically, the detection unit 1 includes an engine speed sensor 1a for detecting the engine speed, an AT input speed sensor 1b for detecting the turbine speed of the torque converter or the input speed of the automatic transmission (AT input speed), a throttle opening sensor 1c for detecting the opening of the throttle valve, an ignition timing sensor 1d for detecting the ignition timing of the engine, a fuel injection amount sensor 1e for detecting the fuel injection amount of the engine, and a valve timing sensor 1f for detecting the valve timing of the engine. In addition, the detection unit 1 has, for example, a wheel speed sensor (not shown) for detecting the vehicle speed, an accelerator position sensor (not shown) for detecting the operation amount of the accelerator pedal (depression amount, accelerator opening, etc.). The detection unit 1 is electrically connected to the controller 2 and outputs an electrical signal corresponding to the detection value or calculation value of the various sensors, devices, and apparatuses as described above to the controller 2 as detection data.

[0020] The controller 2 is an electronic control device mainly composed of, for example, a microcomputer, and controls the vehicle Ve in the embodiment of the present invention. In the example shown in FIG. 1, the controller 2 is composed of, for example, an engine-ECU 2a for controlling the engine, a 4WD-ECU 2b for controlling the vehicle Ve as a "standby type 4WD vehicle", and an AT-ECU 2c for controlling the automatic transmission and the lock-up clutch. Various data detected or calculated by the detection unit 1 described above are input to the controllers 2a, 2b, and 2c, respectively. The controllers 2a, 2b, and 2c perform calculations using the various input data and the data and calculation formulas stored in advance. Then, the controllers 2a, 2b, and 2c output the calculation results as control command signals, and as described above, are mainly configured to perform comprehensive control of the vehicle Ve as a "standby type 4WD vehicle" and execute the flex lock-up control in the embodiment of the present invention.

[0021] In FIG. 1, an example is shown in which the controller 2 is configured to be divided into the three controllers 2a, 2b, and 2c as described above. However, the controller 2 may be integrally configured from one or two controllers by grouping together the devices or apparatuses to be controlled or the control contents. Alternatively, the controller 2 may be configured from a plurality of controllers more than three, for each device or apparatus to be controlled or for each control content.

[0022] As described above, the control device for a four-wheel drive vehicle according to the embodiment of the present invention is configured to execute flexible lock-up control of a lock-up clutch for the purpose of achieving good fuel efficiency performance and NV performance.

[0023] Therefore, the controller 2 first acquires the engine torque, the rear input torque, and the AT input rotational speed, respectively. For example, in the example shown in FIG. 1, various detection data detected in real time by the detection unit 1 are input to the engine-ECU 2a. The engine-ECU 2a calculates the engine torque based on the input various detection data. Then, the calculated engine torque is input to the AT-ECU 2c.

[0024] Also, various detection data detected in real time by the detection unit 1 are input to the 4WD-ECU 2b. The 4WD-ECU 2b calculates the rear input torque (the torque transmitted to the rear drive shaft) based on the input various detection data. Then, the calculated rear input torque is input to the AT-ECU 2c.

[0025] Also, the AT input rotational speed (the input rotational speed of the automatic transmission) detected in real time by the AT input rotational speed sensor 1b is input to the AT-ECU 2c. Alternatively, the turbine rotational speed of the torque converter is converted into the AT input rotational speed and input to the AT-ECU 2c.

[0026] The AT-ECU 2c controls the automatic transmission (AT) and the lock-up clutch respectively. At the same time, the AT-ECU 2c executes flex lock-up control. For example, in the example shown in FIG. 1, based on the lock-up / flex area map A, area determination for determining the control state of the lock-up clutch is performed. In the lock-up / flex area map A, area determination thresholds A1, A2, and A3 are set according to the magnitude of the rear input torque, and based on these area determination thresholds A1, A2, and A3, the engine torque, and the AT input rotational speed, the control area of the lock-up clutch is determined. On the lock-up / flex area map A, if the operating point determined from the engine torque and the AT input rotational speed is to the lower right of the area determination threshold A1 (or A2, A3) selected based on the rear input torque at that time, it is determined as the lock-up area. If the operating point determined from the engine torque and the AT input rotational speed is to the upper left of the area determination threshold A1 (or A2, A3) selected based on the rear input torque at that time, it is determined as the flex area.

[0027] Also, when the AT-ECU 2c determines that the control area of the lock-up clutch is the flex area, it executes flex lock-up control. For example, in the example shown in FIG. 1, based on the flex target differential rotation map B, flex lock-up control is executed. In the flex target differential rotation map B, the target differential rotations B1, B2, and B3 of the lock-up clutch are set according to the magnitude of the rear input torque, and based on these target differential rotations B1, B2, and B3, the engine torque, and the AT input rotational speed, the target differential rotation in the flex lock-up control is calculated.

[0028] Then, the AT-ECU 2c controls the lock-up clutch based on the target differential rotation of the lock-up clutch calculated in real time as described above. That is, it executes flex lock-up control.

[0029] As described above, the control device for a four-wheel drive vehicle according to the embodiment of the present invention controls a four-wheel drive vehicle equipped with a front drive shaft on the front wheel side and a rear drive shaft on the rear wheel side, and executes flex lock-up control of a lock-up clutch. By appropriately executing the flex lock-up control, the differential rotation of the lock-up clutch can be suppressed to a low level, and the loss in the torque converter can be reduced, thereby improving the fuel efficiency of the four-wheel drive vehicle having the engine as a power source. Further, in the control device for a four-wheel drive vehicle according to the embodiment of the present invention, the AT input rotation speed, the engine torque, and the rear input torque are acquired in real time, and the above-described flex lock-up control is executed based on the latest AT input rotation speed, engine torque, and rear input torque. Therefore, it is possible to avoid the deviation between the control preconditions of the prior art and the actual rear input torque of the rear drive shaft, and appropriately execute the flex lock-up control. For example, even when controlling a "standby type 4WD vehicle", it is possible to appropriately reflect torque fluctuations of the rear drive shaft based on the actual rear input torque and execute the flex lock-up control.

[0030] Therefore, according to the control device for a four-wheel drive vehicle according to the embodiment of the present invention, it is possible to appropriately execute the flex lock-up control of the lock-up clutch provided in the torque converter, and it is possible to achieve good balance between the fuel efficiency performance and the NV performance of the four-wheel drive vehicle.

Description of Signs

[0031] 1 Detection unit 1a Engine rotation speed sensor (of the detection unit) 1b AT input rotation speed sensor (of the detection unit) 1c Throttle opening sensor (of the detection unit) 1d Ignition timing sensor (of the detection unit) 1e Fuel injection amount sensor (of the detection unit) 1f Valve timing sensor (of the detection unit) 2 Controller 2a Engine-ECU (of the controller) 2b 4WD-ECU (of the controller) 2c AT-ECU (of the controller) A Lock-up / Flexible Region Map A1, A2, A3 Region Judgment Threshold B Flexible Target Difference Rotation Map B1, B2, B3 Target Difference Rotation Ve Vehicle (Four-wheel drive vehicle)

Claims

【Claim 1】 A four-wheel drive vehicle control device that mounts an engine as a driving force source, a torque converter that transmits the output torque of the engine to a transmission, a lock-up clutch that places the space between the input member and the output member of the torque converter in any one of an engaged state, a released state, and a slip engagement state, a front drive shaft that transmits the output torque to the front wheels, and a rear drive shaft that transmits the output torque to the rear wheels, and executes flex lock-up control of the torque converter that causes the differential rotation between the input member and the output member to follow a target differential rotation, The four-wheel drive vehicle control device includes a controller that controls the four-wheel drive vehicle and executes the flex lock-up control, The controller, calculates or acquires the input rotation speed of the transmission, the output torque, and the rear input torque transmitted to the rear drive shaft, respectively, sets the target differential rotation based on the calculated or acquired input rotation speed, output torque, and rear input torque, and executes the flex lock-up control A control device for a four-wheel drive vehicle, characterized by the above.

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