Abstract: A vehicle drive force control system reduces front-wheel drive force and rear-wheel drive force during unstable running of a vehicle. The front-wheel drive force is reduced with an increase in the running instability, and the front-wheel and rear-wheel drive forces are controlled during low-speed vehicle turning while traction control is effected for at least one of the front wheels. The result is that the front-wheel drive force can be reduced with a decrease in friction coefficient &mgr; of a road surface, while the rear-wheel drive force can be reduced with an increase in turning angle of the vehicle and does not exceed the front-wheel drive force.

Abstract: A microcomputer-based electronic control system for a full time four wheel drive torque transfer case monitors the relative slip between the front and rear output shafts of the transfer case, and generates a signal to engage an electromagnetic clutch for a predetermined time period in the event a predetermined slip threshold is exceeded. The control system continuously interrogates two Hall effect sensors positioned over toothed wheels on the front and rear outputs of the transfer case. Tooth counts are stored in two numerical stacks (one for each sensor), the depth of which may be adapted to the requirements of the particular design. Upon detecting a tooth count, the system adds the count to the sensor's current stack register and pushes all of the registers of the other stack down one register. The last register is pushed out or deleted from the stack memory.

Abstract: A driving force control apparatus of a motor vehicle including a first set of drive wheels and a second set of drive wheels, e.g., front wheels and rear wheels, which are driven with respective driving forces that are controlled independently of each other. The control apparatus calculates an actual slip rate difference between a slip rate of the first set of drive wheels and that of the second set of drive wheels, and controls distribution of driving force between the first set of wheels and the second set of wheels, based on the slip rate difference.

Abstract: In a front wheel-and rear-wheel drive vehicle having a motor such as an engine to develop a mechanical energy and to drive either one of front road wheels or rear road wheels of the vehicle and another motor such as an electric motor to develop the mechanical energy and to drive the other of the front road wheels or the rear road wheels, a drive controller is provided to control a driving force of the other motor, a front-and-rear road wheel velocity difference detector is provided to detect a front-and-rear road wheel velocity difference (&Dgr;N) between the front and rear road wheels, a driver's vehicular acceleration intention detector such as an accelerator pedal depression sensor is provided to detect a manipulated variable (PS) representing a driver's vehicular acceleration intention, a target torque calculating section calculates a target torque outputted from the other motor in accordance with the detected front-and-rear road wheel velocity difference and the manipulated variable, another mo

Abstract: In case there occurs a wheel slip in either one of front left and right wheels or rear left and right wheels, a traction control through an engine output and a traction control through braking are implemented. Furthermore, in case the vehicle speed is slow, a final limited slip differential torque is set by adding a limited slip differential compensation amount according to a steering angle to a limited slip differential torque set according to an inputted torque and a front/rear differential rotation, and further adding thereto a limited slip differential compensation amount according to the vehicle speed for increasing the compensation.

Abstract: A vehicle driving arrangement is provided which has at least two driven wheels, the driving torques of which can be individually regulated by a control device, the control device being connected to a sensor arrangement comprising at least one sensor. Using such a driving arrangement, wheel slip is to be prevented. For that purpose, using a signal of the sensor arrangement, the control device continuously ascertains a maximum torque for each wheel, continuously ascertains the driving torque of each wheel and reduces the driving torque by the appropriate amount when the driving torque ascertained no longer complies with a predetermined limit of difference from the maximum torque.

Abstract: A transfer case control system or apparatus 10 is provided for use on a four-wheel drive vehicle of the type having a transfer case 32, a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 selectively generates a control signal which controls the amount of torque provided to driveshafts 22, 26. Controller 40 provides an improved torque adjustment “response” by automatically adjusting to the condition of the vehicle's tires.

Abstract: A vehicle drive force control system reduces front-wheel drive force and rear-wheel drive force during unstable running of a vehicle. The front-wheel drive force is reduced with an increase in the running instability, and the front-wheel and rear-wheel drive forces are controlled during low-speed vehicle turning while traction control is effected for at least one of the front wheels. The result is that the front-wheel drive force can be reduced with a decrease in friction coefficient &mgr; of a road surface, while the rear-wheel drive force can be reduced with an increase in turning angle of the vehicle and does not exceed the front-wheel drive force.

Abstract: A method of initiating a neutral tow feature in a four-wheel drive vehicle. To initiate the neutral tow feature, an input signal is received from at least one signal generating device. Thereafter, it is determined if the at least one signal indicates that a precondition has been met. If the precondition has been met, then the neutral tow feature is automatically engaged.

Abstract: An apparatus and a method for estimating a vehicle speed of a vehicle in which a driving state can be switched between a four-wheel drive (4WD) state and a two-wheel drive (2WD) state. The driving state of the vehicle can be determined based on one or more pieces of information. A controller calculates the vehicle speed based on a wheel speed of at least one non-driven wheel when it is determined that the vehicle is in the 2WD state. When it is determined that the vehicle is not in the 2WD state or when it cannot be determined that the vehicle is in the 2WD state, the controller calculates the vehicle speed based on the lowest one and/or the second lowest one of the wheel speeds of all of the wheels. Further, an apparatus and method for performing predetermined control, such as behavior control or traction control, that perform the control by using the estimated vehicle speed.

Abstract: A system for an automatic brake intervention control in an all-wheel-drive vehicle having an automatic brake control system, comprises a control device and separately actuatable brakes which are assigned to the individual wheels. The control device generates signals to control individual brakes as a function of wheel compression and rebounding travels or the wheel reaction forces detected at the individual wheels. Wheel signals are generated which correspond to the wheel suspension travels, the wheel reaction forces or quantities derived therefrom, and the wheel signals are supplied to the control device. The control device generates the signals for controlling the individual brakes at least as a function of the individual wheel signals present as input information.

Abstract: There is provided a driving force control system for a four-wheel drive vehicle. An automatic-mode transmitted torque is calculated based on operating conditions of the vehicle. When lock mode-executing conditions including operation of a lock switch by the driver are satisfied, a lock mode in which the engagement forces of the clutches are set to a lock-mode transmitted torque, including a lockable transmitted torque which can lock the front wheels and the rear wheels to each other. Further, the lock-mode transmitted torque is limited depending on a traveling condition of the vehicle such that the lock-mode transmitted torque is held below the lockable transmitted torque. When the automatic-mode transmitted torque is larger than the limited lock-mode transmitted torque during the lock mode, the engagement forces of the clutches are set to the automatic-mode transmitted torques.

Abstract: Provided is a braking force control apparatus for vehicles capable of performing appropriate vehicle braking even in a road-contactless state of a wheel. The braking force control apparatus is adapted to a four-wheel drive vehicle having a center differential for distributing and transmitting driving force to the front wheels and rear wheels and a braking system capable of exerting braking force on each of the front and rear wheels, based on voluntary switching between braking according to driver's brake-pedal actuation and forced braking independent of the brake-pedal actuation. It is determined whether the vehicle is in an engine brake state and it is then determined whether at least one of the wheels is in the road-contactless state.

Abstract: A driving force control system for a four-wheel drive vehicle is disclosed which enables the vehicle to smoothly start on a low-&mgr; road surface, and is capable to distributing just required amounts of driving forces to auxiliary drive wheels depending on an actual accelerating condition of the vehicle, thereby improving the response and fuel economy of the vehicle. The four-wheel drive vehicle includes front wheels as main drive wheels, and rear wheels as auxiliary drive wheels. The driving force control system controls engagement forces of electromagnetic clutches to thereby control the driving forces (torques) distributed to the rear wheels.

Abstract: A driving force control apparatus of a motor vehicle including a first set of drive wheels and a second set of drive wheels, e.g., front wheels and rear wheels, which are driven with respective driving forces that are controlled independently of each other. The control apparatus calculates an actual slip rate difference between a slip rate of the first set of drive wheels and that of the second set of drive wheels, and controls distribution of driving force between the first set of wheels and the second set of wheels, based on the slip rate difference.

Abstract: A method for controlling the speed of an off-the-road vehicle traveling on a gradient permits a constant downhill speed to be maintained. The vehicle speed can be set to a constant descending speed by an electronic system through active braking intervention, without requiring actuation of the brake by the driver. The vehicle in which the method is practiced has several forward speeds and one reverse speed within a low-range traveling phase. The constant descending speed is dependent upon the position of the gas pedal and upon the currently engaged gear of the low-range traveling phase. The method for use in off-the-road vehicles is particularly advantageous for situations in which the braking action of the engine on steep gradients is no longer sufficient to decelerate the vehicle.

Abstract: A four-wheel drive system for a motor vehicle includes a transfer case through which power is continually transmitted to a first drive wheel pair and a clutch that controls a magnitude of torque transmitted to a second drive wheel pair in accordance with an electric current duty cycle applied to the clutch by a control unit that produces an output duty cycle in response to a range selected by the operator, the vehicle speed, and the position of the throttle that controls a power source driveably connected to the input side of the transfer case.

Abstract: In the case that a brake controller is installed to a 4 wheel driven vehicle, braking force control should be carried out effectively enough so that running stability of the vehicle can be up-graded at cornering. The brake controller 40 calculates differential value of aimed yaw rate, differential value of predicted yaw rate on low friction road and deflection of the two differential values. And also it calculates deflection of real yaw rate and aimed yaw rate. Then the brake controller 40 determines aimed braking force and applies the aimed braking force to a selected wheel to carry out braking control. The torque distribution controller 70 receives control parameters and signals of status of brake control and carries out torque distribution control based on the parameters and signals through the hydraulic multi-plate clutch 21.

Abstract: An improved vehicle yaw control that does not require a yaw sensor, wherein the validity of an estimate of vehicle yaw is determined and used to select an appropriate control methodology. The vehicle yaw is estimated based on the measured speeds of the un-driven wheels of the vehicle, and various other conditions are utilized to determine if the estimated yaw rate is valid for control purposes. When it is determined that the estimated yaw rate is valid, a closed-loop yaw rate feedback control strategy is employed, whereas in conditions under which it is determined that the estimated yaw rate is not valid, a different control strategy, such as an open-loop feed-forward control of vehicle yaw, is employed. The validity of the estimated yaw rate is judged based on a logical analysis of the measured wheel speed information, braking information, and steering wheel angle. The measured speeds of the un-driven wheels are used to compute an average un-driven wheel speed and an average un-driven wheel acceleration.

Abstract: When an accelerator pedal is released, or when a brake pedal is depressed and if braking force is lower than a reference braking force corresponding to a braking force immediately before causing a wheel lock, differential limiting force of a center differential is set to a predetermined value so as to retain an under-steer condition while engine brake is applied. When the brake pedal is depressed and if braking force is higher than the reference braking force, differential limiting force of the center differential is set to zero so as to assist an anti-lock brake system. Further, the reference braking force can be determined according to a road friction coefficient, a grade of road, a lateral acceleration and the like. Further, the predetermined value of the differential limiting force may be a constant value or may be a value corresponding to a front-to-rear weight distribution ratio.

Abstract: An all wheel drive mechanism has a powertrain including an engine, transmission, front drive differential, a rear drive transfer gearing and a selectively operable rear drive mechanism. The rear drive mechanism has a housing, driven by the transfer gearing through a drive shaft. A pair of selectively engageable clutches, which are operable to connect the rear wheels to the housing, are disposed in the housing. A pair of pumps are assembled in the housing to provide operating fluid for the clutches. Each pump has one member secured for rotation with the housing and another member secured for rotation with respective rear wheel drive axles. An inlet of the pumps is controlled by a solenoid operated valve which is energized in response to an anti-lock brake system and traction control system of the vehicle. When energized, the valve connects the pumps to a reservoir such that fluid in the reservoir can be pumped to the clutches to enforce engagement thereof resulting in a drive path to the rear wheels.

Abstract: In a four wheel drive vehicle, when rear wheels which are principal drive wheels skid, first a traction control system is operated so as to reduce the drive power to the rear wheels. Thereafter the proportion of drive power apportioned to the front wheels which are auxiliary drive wheels is increased by a torque splitting control system. By doing this, skidding of a wheel due to delay in application of traction control is prevented.

Abstract: A working vehicle such as an agricultural tractor includes a control device having an accelerating drive mode to accelerate front wheels automatically to rotate faster than rear wheels when the front wheels are steered in excess of a fixed amount. When the rotating speed of an engine falls below a predetermined value, a shift to the accelerating drive mode is inhibited to avoid an engine stall.

Abstract: In a four wheel drive vehicle, a driving force distribution control apparatus estimates a road friction coefficient and controls a transfer clutch of a center differential based on the estimated road friction coefficient so that a driving force distribution on the rear wheel side becomes larger as the estimated road friction coefficient becomes small. An initial value of the road friction coefficient is established to be a low value such as 0.3 when a wiper switch is turned on, an outside air temperature is low, a traction control apparatus operates, an anti-lock brake control apparatus operates, a braking force control apparatus operates, a slip detecting apparatus detects a slip and a transmission control unit outputs a signal and is established to be an intermediate value such as 0.5 when an initial start judgment section judges an initial start of the engine after a long period of stop.

Abstract: A differential lock control system for controlling the locking of the various differential assemblies associated with a particular work machine wherein such system includes a first switch positionable to select any one or more of the differential assemblies for operation in their locked condition, a second switch actuatable to control the locking of the differential assemblies selected by the first switch, a ground speed sensor for determining the ground speed of the work machine, an optional steering pressure sensor for determining the steering effort required to turn the wheels associated with the front axle, and an electronic controller coupled to the first and second switches and to the respective sensors for receiving signals therefrom, the controller outputting a signal to actuate the locking mechanism of the differential assemblies selected by the position of the first switch when the controller receives a signal indicative of the second switch being actuated, and a signal indicative of the ground spee

Abstract: A driving torque control apparatus has a first differential restraining device which restrains a rotational speed differential between front-left and front-right wheels by adjusting driving torque to be transmitted from a power source mounted on a four-wheel drive vehicle to each of the front-left and front-right wheels, and a second differential restraining device which restrains a rotational speed differential between rear-left and rear-right wheels by adjusting driving torque to be transmitted from the power source to each of the rear-left and rear-right wheels. An adjustment of driving torque by the second differential restraining device is executed in preference to an adjustment of driving torque by the first differential restraining device.

Abstract: A braking control system for agricultural tractors comprises:of the type having a pair of front wheels and a pair of rear wheels with at least one pair being driven through a differential and wherein individual wheel brakes are individually controlled through a hydraulic braking control unit which in turn is controlled by an electronic control unit which causes the braking control unit to apply braking pressure to slow the wheels on the inside of the steering bend in response to signals received by a steering angle sensor.

Abstract: A method of monitoring the relative effective diameters of the tires and compensating therefor in a vehicle which includes a front driveshaft for transferring motive power to a front set of wheels and a rear driveshaft for transferring motive power to a rear set of wheels, each of the wheels having an effective diameter. Front and rear driveshaft values indicative of the rotational speed of each driveshaft are generated. A difference value indicative of a difference between said front and rear driveshaft values is then generated. A low pass filtered value is generated according to the relationship of Y.sub.1p =(1-.beta.)*U(k)+.beta.*Y.sub.1p (k-1). The low pass filtered value is monitored for a predetermined period of time to determine if one of the wheels has a smaller effective diameter than the other wheels.

Abstract: For automatically controlling a differential lock in drive axles of a motor vehicle, an arrangement has a lock coupling, an actuator for actuating the lock coupling, a plurality of rotary speed sensors associated with wheels of the vehicle for forming the rotary speed signal, a control unit for receiving the rotary speed signals and forming a control signal for controlling the actuator means, the control unit including computing means for computing a nominal rotary speed value associated with each of the wheels so that a computed nominal rotary speed value is determined continuously in dependence from a corresponding traveling condition, a first comparing unit for forming a difference rotary speed value from a comparison of a measured rotary speed value with the computed nominal rotary speed value, and a second comparing unit for forming the control signal so that when the difference rotary speed value exceeds a predetermined threshold value the lock coupling is engaged and when the difference rotary speed va

Abstract: In control apparatus and method for a four-wheel drive vehicle, when the vehicle in which two tire wheels having different radii from those of originally equipped tire wheels are mounted as either front tire wheels or rear tire wheels is running at a speed exceeding a reference speed (approximately, 40 km/h), a rate of distribution of an engine driving force between mainly driven tire wheels and auxiliarily driven tire wheels set on the basis of a rotation speed difference between the mainly and auxiliarily driven tire wheels (.DELTA.V.sub.W) is modified so that the driving force distributed to the auxiliarily driven tire wheels can be maintained constantly at its minimum limit so as to prevent a control hunting of the driving force distribution to the auxiliarily driven tire wheels based on the rotation speed difference from occurring.

Abstract: In an automobile having a pair of front wheels, a pair of rear wheels, a brake system for selectively braking each of the pairs of front and rear wheels, an engine, a transmission system including a speed change gear device for selectively providing a plurality of transmission gear ratios, a center differential device, a front differential device, and a rear differential device, the traction control device detects slipping conditions of each of the pairs of front and rear wheels, and controls the brake system so as to brake at least one of the pairs of front and rear wheels for execution of traction controls according to one of at least two separate traction control programs which are automatically changed over for execution according to selections of the transmission gear ratios of the speed change gear device for a relatively high speed driving or a relatively low speed driving.

Abstract: A method of controlling the amount of power delivered to the front driveshaft and to the rear driveshaft of a motor vehicle including the steps of generating a front driveshaft value indicative of the rotational speed of said front driveshaft and generating a rear driveshaft value indicative of the rotational speed of said rear driveshaft. A vehicle speed is generated based on the lower of said front driveshaft value and said rear driveshaft value. The amount of power delivered to said front driveshaft and to said rear driveshaft is controlled as a function of said vehicle speed.

Abstract: A four-wheel drive control system for an automotive vehicle equipped with a transfer including a friction clutch for distributing a driving force to rear wheels and front wheels under a control of an engaging force of the friction clutch.

Abstract: A traction control system for a four wheel drive vehicle including generating a first value corresponding to an average rotational speed of front wheels, generating a second value corresponding to an average of a rotational speed of rear wheels, comparing the first and second values, and generating a first signal corresponding to a difference between the first and second values, are provided. The first signal is used for transferring torque to the secondary axle if the rear wheels are rotating faster than the front wheels. The system also generates a second signal corresponding to a difference in speed between a first axle shaft and a second axle shaft of the front axle. The second signal is used for transferring torque to the other of the front axle shafts if the one of the secondary axle shafts is rotating faster than the other of the front axle shafts.

Abstract: A 4-wheel drive vehicle has a driving force control method in which a portion of a driving force for front wheels is distributed to rear wheels through clutches. In a 4-wheel drive state in which a driving force T.sub.p is distributed to rear wheels, for example, if the vehicle is turned leftwards to generate a difference W.sub.R -W.sub.L between left and right rear wheel speeds, it is ensured that a driving force T.sub.R distributed to the right rear wheel, which is an outer wheel during turning of the vehicle, is larger than a driving force T.sub.L distributed to the left rear wheel, which is an inner wheel during turning of the vehicle, thereby providing an enhancement in turning performance. As the difference W.sub.R -W.sub.L between the left and right rear wheel speeds is increased as a result of decreasing of the turning radius of the vehicle, the driving force T.sub.P (=T.sub.L +T.sub.R) distributed to the rear wheels is decreased to avoid an increase in travel resistance.

Abstract: A traction control system and method of a four-wheel drive vehicle comprises an engine control apparatus, a brake drive apparatus for automatically and independently applying brake to each of four wheels, wheel speed detecting means, vehicle speed detecting means, steering angle detecting means, yaw rate detecting means, target yaw rate calculating means, yaw rate deviation calculating means, slip amount calculating means for calculating an actual slip amount, reference slip amount storing means for memorizing a reference slip amount, target slip amount determining means for determining a target slip amount based on the reference slip amount, traction control judging means for outputting a traction control signal when a traction control is needed, target braking force calculating means, target engine torque calculating means. When a traction control is needed, the target slip amount determining means determine a target slip amount of a wheel needing the traction control.

Abstract: A driving-torque control system for a four-wheel-drive vehicle includes a transfer clutch employed in a transfer of the four-wheel-drive vehicle for varying a distribution ratio of driving torque between front and rear road wheels depending on a front-and-rear wheel revolution-speed difference. A calculation unit derives a command value of the engaging force of the transfer clutch from the front-and-rear wheel revolution-speed difference. A load-condition detection unit detects an input load condition of the transfer clutch, on the basis of the front-and-rear wheel revolution-speed difference and the command value of the engaging force. A comparing unit compares the input load condition detected by the load-condition detection unit with a predetermined threshold. A compensation unit compensates the engaging force of the transfer clutch so that the transfer clutch is held in a completely engaged state for a predetermined holding time duration, when the input load condition exceeds the predetermined threshold.

Abstract: A system for controlling a four-wheel drive for a motor vehicle comprises a drive mode switch for detecting a drive mode of the motor vehicle selectable between a two-wheel drive mode and a four-wheel drive mode. The four-wheel drive mode is selectable between a direct-coupled four-wheel drive mode. A an auto four-wheel drive mode, a controller controls the distribution of traction between main and secondary driving wheels. A traction transmission train distributes traction between the main and secondary driving wheels. The traction transmission train has an oil pressure supply system having a friction clutch and a solenoid.

Abstract: A four-wheel drive vehicle includes a transfer case for controlling the delivery of power between the front and rear wheels of the vehicle. A clutch in the transfer case controls the amount of power delivered to the front and rear wheels in response to a clutch PulseWidth Modulated (PWM) signal which is generated by an electronic powertrain controller. The powertrain controller receives a first signal which is indicative of the rotational speed of a front driveshaft, which transfers motive power from the transfer case to a pair of front wheels, and a second signal which is indicative of the rotational speed of a rear driveshaft, which transfers motive power from the transfer case to a pair of rear wheels.

Abstract: An active torque-split control system for a four-wheel-drive vehicle comprises a transfer clutch, and sensors for detecting a wheel-speed difference between a primary drive wheel and a secondary drive wheel, a throttle opening, a vehicle speed, depressed or undepressed states of a brake pedal. The system is capable of executing both a feedback control based on the wheel-speed difference and a feedforward control based on the throttle opening. The system is responsive to at least a feedback control signal from the feedback control system and an anticipating correction signal from the feedforward control system for determining a distribution ratio of driving torque of the secondary drive wheel to the primary drive wheel depending on the highest one of the feedback control signal value and the anticipating correction signal value.

Abstract: A control system for engaging, disengaging and re-engaging a front wheel drive in an agricultural vehicle includes a control circuit configured to receive signals representative of vehicle operating parameters and to generate control signals corresponding to the desired state (i.e. engaged or disengaged) of a front wheel drive engagement circuit. Sensors are associated with the rear wheels, rear service brakes, implement positioning circuit, the vehicle body and the front axle to provide parameter signals related to wheel speed, braking, implement position and vehicle speed. Control logic executed by the control circuit in a continuously cycled routine determines the desired state of the engagement circuit based upon all operating parameters. The control circuit applies an appropriate control signal to the engagement circuit causing engagement or disengagement in accordance with the desired state.

Abstract: In a driving force transfer apparatus for a part-time four-wheel drive vehicle with a fail safe structure, a high-speed gear range shift position and a low-speed gear range shift position in a high-speed and low-speed gear range position switching mechanism in a sub transmission are determined without special position sensors. In a case where the special position sensors are installed in the transfer apparatus, a shift position sensor diagnosis operation is effected so that a failure in either of a high-speed gear range position or low-speed gear range position sensor can easily be detected. If the failure in either of the position sensor occurs, a hydraulic (oil) pressure supply for providing a clutch pressure for a frictional clutch is made effective. Furthermore, a failure of either of revolution speed sensor detecting a first output axle revolution speed or detecting a second output axle revolution speed can also be detected. The first output axle is connected to mainly driven road wheels.

Abstract: In a torque distribution control system of a four wheel drive vehicle, it is important to distribute a driving force properly between front and rear wheels according to friction coefficient of road surface. Especially when a vehicle runs on roads with low friction coefficients of road surface, it is very important to estimate friction coefficients of the road surface which vary every moment and to control the driving force according to the estimated friction coefficients. The present invention provides the torque distribution control system with means for estimating friction coefficients of road surface every moment based on data from a steering angle sensor, a vehicle speed sensor and a yaw rate sensor and for reflecting them on the calculation of torque distribution between front and rear wheels. Furthermore, yaw moment calculating means are provided to prevent the vehicle from tack-in phenomenon by properly controlling left and right wheels.

Abstract: A traction control system for a fourwheel drive vehicle having a center differential comprises a brake pressure control apparatus, an engine output control apparatus, a differential limiting torque control apparatus, vehicle speed calculating means for calculating a reference vehicle speed of a vehicle, slip amount calculating means for calculating a slip amount of each wheel, target slip amount determining means for determining a front target slip amount of front wheels and a rear target slip amount of rear wheels, traction control determining means for determining to operate a traction control when the slip amount of the front wheels exceeds the front target slip amount or when the slip amount of the rear wheels exceeds the rear target slip amount, brake pressure calculating means for calculating a brake pressure so as to apply a brake to the wheels and engine output calculating means for calculating a target engine torque corresponding to a difference between the slip amount and the target slip amount, whe