Abstract: Front and rear wheels Tf, Tr of a motor vehicle driven by an engine 10 are connected through a differential control device 15 which is capable of varying the torque to transmit. When the turning radius of a predetermined one wheel or the motor vehicle is equal to or smaller than a predetermined turning radius, the transmission torque of the differential control device is decreased by a control device to prevent the tight-corner braking phenomenon from occurring. When the motor vehicle is stopped momentarily with the transmission torque being lowered, the control device maintains the transmission torque as it is, and the vehicle is then restarted with the transmission torque being lowered. Thus, when the motor vehicle which was stopped momentarily with a large steering angle is then restarted, the tight-corner braking phenomenon can be prevented from occurring from the beginning of the restarting.

Abstract: In a steering system 30, a transmission ratio R1 which is determined in dependence on the vehicle speed by reference to a transmission ratio decision map is multiplied with a first transmission ratio alteration gain g10 which is determined in dependence on the distribution of a traveling drive torque from an engine 11 to front wheels 14 and rear wheels 15, thereby to alter the ratio R1 of steering torque distribution from a steering handle 31 to the front wheels 14, whereby the variation of the steering feeling due to an increase or decrease in the distribution of the traveling drive torque to the front wheels 14 can be suppressed. Further, the transmission ratio R1 is multiplied with a second transmission ratio alteration gain g11 which is determined in dependence on the gradient of the road surface by reference to a second transmission ratio alteration map, thereby to alter the transmission ratio R1, whereby the variation of the steering feeling due to the variation of the gradient can also be suppressed.

Abstract: A driving force transmitting apparatus includes: a first torque-transmitting member having a cylindrical portion and provided with a spline tooth; a second torque-transmitting member positioned inside the cylindrical portion and arranged coaxially rotatably relative to the first torque-transmitting member; a main clutch with a spline tooth; an actuator unit for actuating the main clutch to be engaged; and a controlling device for controlling the actuator unit so as to pressurize the main clutch plate in such a manner that torque is not substantially transmitted between the first torque-transmitting member and the second torque-transmitting member when the engagement of the main clutch is judged to be unnecessary.

Abstract: An ECU estimates the temperatures of the heat generating portions provided in a drive force transmission system, or a transaxle, a rear differential, and a torque coupling, in correspondence with not only the rotational speed (the differential rotational speed) of each heat generating portion and the torque transmission rate of the torque coupling but also the outside temperature detected by an outside temperature sensor. If the estimated temperature of any of the heat generating portions exceeds a respective predetermined temperature, the ECU controls operation of the torque coupling to suppress overheating of the heat generating portion. That is, the temperature of each heat generating portion is accurately detected through a simplified structure and overheating of the heat generating portion is effectively suppressed.

Abstract: An IG-off-timer measures the time t_off from when an engine is stopped, or an ignition is turned off. An ECU sequentially memorizes an estimated temperature of each of heat generating portions as a memorized temperature. Immediately after the engine is re-started, the ECU sets an initial value of the estimated temperature of each heat generating portion in such a manner that the initial value reflects a temperature drop of the heat generating portion in the deactivation period of the engine. The temperature of the heat generating portion is thus accurately estimated even after re-starting of the engine. The heat generating portions are thus appropriately protected.

Abstract: A CPU computes a throttle opening degree increasing speed V?h and a steering wheel angular velocity V? based on a throttle opening degree ?h and a steering wheel angle ?. Based on the throttle increasing speed V?h and the steering wheel angular velocity V?, the CPU selects one of a first drive mode and a second drive mode. The CPU controls the power transmission ratio of a power transmitting device according to the selected drive mode. Therefore, the power transmission ratio of the power transmitting device is properly controlled in accordance with the degree of intention for acceleration of the driver, which is computed based on the throttle increasing speed V?h, and the turning speed of the steering wheel, which is computed based on the steering wheel angular velocity V?. Therefore, the drive mode is properly switched in accordance with the driving state of a four-wheel drive vehicle.

Abstract: The control system of a vehicle according to the present invention controls the transmission ratio of the steering angle of a steering wheel relative to a turning angle of front wheels based on a drive force distribution ratio. Thus, the performance of the tires on the front wheels can be used to almost maximum potential, providing effective prevention of understeering. The present invention provides a steering system that limits understeering effectively.

Abstract: In a steering system 30, a transmission ratio R1 which is determined in dependence on the vehicle speed by reference to a transmission ratio decision map is multiplied with a first transmission ratio alteration gain g10 which is determined in dependence on the distribution of a traveling drive torque from an engine 11 to front wheels 14 and rear wheels 15, thereby to alter the ratio R1 of steering torque distribution from a steering handle 31 to the front wheels 14, whereby the variation of the steering feeling due to an increase or decrease in the distribution of the traveling drive torque to the front wheels 14 can be suppressed. Further, the transmission ratio R1 is multiplied with a second transmission ratio alteration gain g11 which is determined in dependence on the gradient of the road surface by reference to a second transmission ratio alteration map, thereby to alter the transmission ratio R1, whereby the variation of the steering feeling due to the variation of the gradient can also be suppressed.

Abstract: A drive system control method and a drive power transmission control system for a four-wheel drive vehicle are provided for enabling the vehicle to operate selectively in an ordinary mode and an anti-vibration mode. In the ordinary mode, the connection force of a coupling device which is provided between front and rear wheel torque transmission axles is kept relatively high, and the front and rear wheel torque transmission axles are brought to connect prime drive wheels with secondary drive wheels, so that four-wheel drive traveling of the vehicle can be realized. The operation mode of the vehicle is switched from the ordinary mode to the anti-vibration mode where the secondary drive wheels slip when the vehicle begins to start in the ordinary mode. In the anti-vibration mode, the connection force of the coupling device is relatively weakened to substantially separate the front and rear wheel torque transmission axles from each other.

Abstract: An ECU, which functions as a driving force distribution control apparatus for a four-wheel drive vehicle, includes a CPU. The CPU controls a coupling for changing torque distribution of front and rear wheels. The CPU determines either of first and second torque distribution modes based on detection signals of a throttle opening sensor and steering angle sensor, which are operating parameters. In the second torque distribution mode, torque is distributed to the front and rear wheels more equally than in the first torque distribution mode. The CPU sets a duration for the second torque distribution mode when the second torque distribution mode is selected. Until the duration elapses, regardless of the operating parameters, the CPU continues the control of the coupling in the second torque distribution mode.

Abstract: A drive system control method and a drive power transmission control system for a four-wheel drive vehicle are provided for enabling the vehicle to operate selectively in an ordinary mode and an anti-vibration mode. In the ordinary mode, the connection force of a coupling device which is provided between front and rear wheel torque transmission axles is kept relatively high, and the front and rear wheel torque transmission axles are brought to connect prime drive wheels with secondary drive wheels, so that four-wheel drive traveling of the vehicle can be realized. The operation mode of the vehicle is switched from the ordinary mode to the anti-vibration mode where the secondary drive wheels slip when the vehicle begins to start in the ordinary mode. In the anti-vibration mode, the connection force of the coupling device is relatively weakened to substantially separate the front and rear wheel torque transmission axles from each other.

Abstract: Front and rear wheels Tf, Tr of a motor vehicle driven by an engine 10 are connected through a differential control device 15 which is capable of varying the torque to transmit. When the turning radius of a predetermined one wheel or the motor vehicle is equal to or smaller than a predetermined turning radius, the transmission torque of the differential control device is decreased by a control device to prevent the tight-corner braking phenomenon from occurring. When the motor vehicle is stopped momentarily with the transmission torque being lowered, the control device maintains the transmission torque as it is, and the vehicle is then restarted with the transmission torque being lowered. Thus, when the motor vehicle which was stopped momentarily with a large steering angle is then restarted, the tight-corner braking phenomenon can be prevented from occurring from the beginning of the restarting.

Abstract: A CPU computes a throttle opening degree increasing speed V?h and a steering wheel angular velocity V? based on a throttle opening degree ?h and a steering wheel angle ?. Based on the throttle increasing speed V?h and the steering wheel angular velocity V?, the CPU selects one of a first drive mode and a second drive mode. The CPU controls the power transmission ratio of a power transmitting device according to the selected drive mode. Therefore, the power transmission ratio of the power transmitting device is properly controlled in accordance with the degree of intention for acceleration of the driver, which is computed based on the throttle increasing speed V?h, and the turning speed of the steering wheel, which is computed based on the steering wheel angular velocity V?. Therefore, the drive mode is properly switched in accordance with the driving state of a four-wheel drive vehicle.

Abstract: A power distribution control device 42 calculates a low-? information magnitude, associated with the friction coefficient of the road surface, based on the slip rate and the vehicle acceleration operation magnitude. If the low-? information magnitude exceeds an addition evaluation threshold, the power distribution control device 42 adds the low-? information magnitude. If the low-? information magnitude does not exceed the addition evaluation threshold, the power distribution control device 42 subtracts a constant K from a counter. The power distribution control device 42 makes evaluates a road to have a low-? when the counter exceeds a low-? evaluation threshold.

Abstract: A four-wheel drive vehicle has front wheels and rear wheels driven by an engine, and a coupling for changing the distribution ratio of torque to the front wheels and the rear wheels. An ECU determines whether engine braking is being applied based on the vehicle speed V and the throttle opening degree Od. When determining that engine braking is being applied, the ECU temporarily performs the engine braking related control. The ECU controls the engaging force of the coupling such that the distribution ratio of torque to the front wheels and the rear wheels is changed to a more equalized state in the engine braking related control than that before the engine braking related control is started. Accordingly, the fixing force of the front wheels and the rear wheels is temporarily increased without delay when engine braking is applied.

Abstract: A four-wheel drive vehicle is provided with a drive power transmission device for controlling the connection degree of a front wheel axle driven by an engine with a rear wheel axle. A drive power distribution control device is responsive to a vehicle speed, a rotational difference between front wheels driven by the front wheel axle and rear wheels driven by the rear wheel axle, a throttle opening degree signal and the like and controls the drive power transmission device. The drive power distribution control device judges whether the vehicle is beginning to start or not and at the starting of the vehicle, controls the transmission rate of the drive power transmission device in dependence on the state or manner in which the vehicle is beginning to start.

Abstract: An ECU (21), which functions as a driving force distribution control apparatus for a four-wheel drive vehicle, includes a CPU (22). The CPU (22) controls a coupling (7) for changing torque distribution of front and rear wheels. The CPU (22) determines either of first and second torque distribution modes based on detection signals of a throttle opening sensor (32) and steering angle sensor (34), which are operating parameters. In the second torque distribution mode, torque is distributed to the front and rear wheels more equally than in the first torque distribution mode. The CPU (22) sets a duration for the second torque distribution mode when the second torque distribution mode is selected. Until the duration elapses, regardless of the operating parameters, the CPU (22) continues the control of the coupling (7) in the second torque distribution mode.

Abstract: A driving force distribution control apparatus and driving force distribution control method for a four-wheel drive vehicle which can quickly increase torque distribution to sub-drive wheels after a transmission has been shifted down. According to the apparatus and method, when it is determined that the transmission has been shifted down, an ECU controls a coupling capable of changing the torque distribution to the front wheels and rear wheels such that the torque distribution to the front wheels and rear wheels approaches a uniform state.

Abstract: A vehicle has a transmission apparatus that changes the distribution of power transmitted from a power source to a plurality of wheels. The method for distributing power of the vehicle includes detecting the temperature of a part located on a power transmission path between the power source and a wheel to which power is transmitted from the power source through the transmission apparatus, the heat of the part being increased as the power distribution ratio is increased; determining that the current state is a specific state in which the detected temperature reaches a previously set first reference temperature; and controlling the transmission apparatus to lower the power distribution ratio to the wheel from the transmission apparatus when the current state is determined to the specified state.

Abstract: A power distribution control apparatus determines a command value that corresponds to the driving state of a four-wheel drive vehicle. The vehicle includes a pair of front wheels and a pair of rear wheels, and a coupling device that changes the power distribution to the front wheels and the rear wheels. The control apparatus detects the differential rotation speed between the average rotation speed of the front wheels and the average rotation speed of the rear wheels. The control apparatus estimates the exothermic energy generated in the coupling device based on the product of the differential rotation speed and the command value. The control apparatus determines an optimum drive mode for the four-wheel drive vehicle based on the estimated exothermic energy and for selecting map data corresponding to the determined drive mode. The control apparatus determines the command value that corresponds to the driving state by using the map data.