JP2008517819A - All-wheel drive system - Google Patents

Abstract

The present invention relates to an all-wheel drive system for an automobile (10). The automobile (10) has a difference between an engine (12) and a pair of front wheels (16, 18) having drive shafts (24, 26) driven via a front wheel axle unit having a differential gear device (36). Between a pair of rear wheels (20, 22) having drive shafts (32, 34) driven via a rear wheel axle unit having a dynamic gear device (42), and between the front wheel axle unit and the rear wheel axle unit. A central differential gear device (38) provided, through front and rear propeller shafts (39, 28) extending from the central differential gear device to a front wheel axle unit and a rear wheel axle unit, respectively. The central differential gear unit (38) capable of transmitting torque from the engine (12) to the front wheel axle unit and the rear wheel axle unit, and the final drive gear of the front wheel axle unit is a rear wheel axle unit. In addition, the all-wheel drive system is associated with a central differential gear unit (38) and is associated with one or both of the front and rear propeller shafts (39, 28). It has a synchronizing means which can change a rotational speed.

Description

  The present invention relates to automobiles, and in particular, but not limited to, all-wheel drive systems in four-wheel drive vehicles.

  A recent trend in the development of all-wheel drive systems is to provide a means to influence the dynamic behavior of the vehicle by distributing the drive torque across the vehicle.

  With such a system, the dynamic behavior of the vehicle is monitored, and when it is detected that the dynamic behavior of the vehicle exceeds a predetermined limit, an intervention is made to change or influence the dynamic behavior.

  The first invention of the present invention operates through an engine, a pair of front wheels having a drive shaft driven via a front wheel axle unit having a differential gear device, and a rear wheel axle unit having a differential gear device. A center differential gear device provided between a pair of rear wheels having a driving shaft and the front wheel axle unit and the rear wheel axle unit, wherein the front wheel axle unit and the rear wheel axle unit are provided from the central differential gear device. In the all-wheel drive system for an automobile, comprising the central differential gear device that transmits torque from the engine to the front wheel axle unit and the rear wheel axle unit via front and rear propeller shafts extending to The final drive gear of the front wheel axle unit has a different gear ratio than the final drive gear of the rear wheel axle unit, and further, the system includes: Synchronizing means provided in association with the central differential gear mechanism, wherein the synchronizing means is operable to change the rotational speed of one or both of the front and rear propeller shafts. An all-wheel drive system is provided.

  By varying the gear ratio of the front and rear axle units, the front propeller shaft differs from the rear propeller shaft when the vehicle front and rear wheels have the same radius and are rotating at the same speed Rotates at speed. In a four-wheel drive vehicle where the driving force distribution is biased on the front wheels, the gear ratio of the front wheel axle unit is higher than the gear ratio of the rear wheel axle unit. Conversely, in a four-wheel drive vehicle in which the driving force distribution bias is applied to the rear wheels, the gear ratio of the front wheel axle unit is lower than the gear ratio of the rear wheel axle axle unit.

  In a preferred embodiment, the difference in effective gear ratio between the front wheel axle unit and the rear wheel axle unit is such that the final drive gear ratio of the front wheel axle unit is different from the final drive gear gear ratio of the rear wheel axle unit. Get it by making a ratio. In an alternative embodiment, the difference in effective gear ratio is obtained by providing an intermediate gear device intermediate the central differential gear device and one of the rear wheel axle unit and the front wheel axle unit. In such an embodiment, the intermediate gear device has a drop gear device provided between the central differential gear device and one of the front wheel axle unit and the rear wheel axle unit. The drop gear device may be provided between the central differential gear device and one of the front propeller shaft and the rear propeller shaft.

  The difference in gear ratio between the front wheel axle unit and the rear wheel axle unit can be a value in the range of 3% to 10%.

  The synchronization means may have a clutch mechanism operable to change the rotational speed of one or both of the front propeller shaft and the rear propeller shaft. The clutch mechanism preferably has a first state in which the front shaft and the rear propeller shaft can rotate relatively freely, and a second state in which the front propeller shaft and the rear propeller shaft are maintained at a specific rotation and cannot relatively rotate. It is possible to operate between. The clutch mechanism is operable to increase the rotational speed of the rear propeller shaft to approach the rotational speed of the front propeller shaft. As an alternative, the clutch mechanism is operable to reduce the rotational speed of the front propeller shaft to approach the rotational speed of the rear propeller shaft. As a further alternative, the clutch mechanism is operable to change the rotational speed of both propeller shafts.

  The synchronization means is preferably provided with a controller responsive to the dynamic state of the vehicle. The controller is provided with a number of sensors positioned to sense the operating characteristics of the vehicle. For example, one or more wheel speed sensors, lateral acceleration sensors, longitudinal acceleration sensors, steering input sensors, engine torque request sensors, and vehicle deflection (yaw) sensors may be provided as sensors. it can.

Another aspect of the invention provides a method for influencing or modifying the dynamic behavior of an all-wheel drive vehicle by allocating drive torque across the vehicle, the method comprising the following steps:
Engine, a pair of front wheels having a drive shaft driven through a front wheel axle unit having a differential gear unit, a pair of rear wheels having a drive shaft driven through a rear wheel axle unit having a differential gear unit A central gear device provided between the wheel, the front wheel axle unit and the rear wheel axle unit, through front and rear propeller shafts extending from the central differential gear device to the front wheel axle unit and the rear wheel axle unit. And a central differential gear device for transmitting torque from the engine to the front wheel axle unit and the rear wheel axle unit, respectively, wherein the final drive gear of the front wheel axle unit is the rear wheel axle. The system has a gear ratio different from that of the final drive gear of the unit, and the system further comprises synchronizing means provided in association with the central differential gear mechanism, A step for preparing a 該全 wheel drive vehicle having a structure with operable synchronizing means to vary one or both of the rotational speed of the front and rear propeller shafts,
Providing the vehicle with a plurality of sensors operable to monitor the dynamic behavior of the vehicle;
Providing a controller configured to receive input from a sensor, wherein the controller is provided with one or more vehicle dynamic behavior parameters;
Via one or more sensors, it is sensed whether the vehicle's dynamic behavior has reached or exceeded a predetermined parameter value in one or more of the one or more dynamic behavior parameters. And a step of operating the synchronizing means via the controller to change the rotational speed of one or both of the front propeller shaft and the rear propeller shaft.

  An embodiment of the invention will now be described with reference to FIG. The vehicle 10 has a transmission housing, that is, an engine 12 to which a gear box 14 is attached, and four wheels 16, 18, 20, and 22. Front wheel drive shafts 24 and 26 extend between the front wheels 16 and 18 and the transmission housing 14. The propeller shaft 28 extends from the gear box 14 to a rear wheel axle (rear axle) unit 30 having a differential gear device. The rear wheel drive shafts 32 and 34 are extended between the rear wheel axle unit 30 and the rear wheels 20 and 22. Therefore, the vehicle 10 can be regarded as having a theoretical front wheel axle and a rear wheel axle with the front and rear wheels 16, 18, 20, 22 attached.

  The transmission housing 14 has a gear box (not shown) provided with a composite forward gear and reverse gear. Further, the transmission housing 14 further includes a front wheel axle (front axle) unit 36 provided with a differential gear device provided between the front wheel drive shafts 24 and 26 and the central differential gear device 38. An internal drive shaft 39 extends between the front wheel axle unit 36 and the central differential 38. Both the central differential gear unit 38 and the rear wheel axle unit 30 are limited slip types and have clutch mechanisms 40, 42 operable to change the torque transmission through the respective differential gear unit.

  Furthermore, the vehicle 10 has a number of sensors operable to determine a predetermined operating state and position relating to the vehicle 10 and the vehicle control device. These sensors include a steering sensor 44 operable to measure the steering input by the driver via the steering wheel 45, acceleration sensors 46 and 48 relating to lateral and longitudinal acceleration, and a yaw (yaw). ) There is a sensor 50. Each wheel 16, 18, 20, 22 is provided with a wheel speed sensor 52, which is conveniently doubled as a sensor for the antilock brake device of the vehicle 10. Function. Furthermore, there are provided controllers 58 and 60 for controlling the operations of the mode switch 54, the engine torque request signal sensor 56, and the clutch mechanisms 40 and 42 of the center and rear wheel axle unit differential gear unit. The mode switch 54 and the sensors 44, 46, 48, 50, 52, 56 are connected to the central controller 62, and the central controller 62 is connected to the clutch mechanism controllers 58, 60.

  A feature of the present invention is the provision of axle units 36, 30 having front and rear differential gear units with different gear ratios, and in particular, a rear wheel axle unit having a lower gear than the front wheel axle unit 36. For example, if the gear ratio of the front wheel axle unit 36 is 3.7: 1, the gear ratio of the rear wheel axle unit is 3.52: 1.

  Next, the operation of the drive management system will be described. Looking first at the operation of the car 10 when the system is inactive, the gearbox is configured to divide and distribute the torque supplied between the axle units in a predetermined manner. For example, this torque distribution is 35% for the front wheel axle unit and 65% for the rear wheel axle unit. Other torque distributions may be utilized and it should be understood that the vehicle 10 is configured to vary the torque distribution between the axles depending on the road surface and driving conditions. Taking the vehicle 10 traveling at a constant speed as an example, both the wheels 16, 18, 20, 22 of the vehicle 10 are theoretically rotating at the same speed, provided that the rolling radius of the front wheels 16, 18 is the rear wheel. Is assumed to be identical to that of It will be understood that the rotational speeds of the propeller shaft 28 and the internal drive shaft 39 are different because the gear ratios of the differential gear units in the front and rear wheel axle units 36 and 30 are different. This difference in rotational speed between the shafts is absorbed by the presence of the central differential gear unit 38. Since the gear ratio of the rear wheel axle unit 30 is lower than that of the front wheel axle unit 36, the internal drive shaft 39 rotates faster than the propeller shaft 28 for a certain engine speed.

  The drive management system is activated by a mode switch. In an alternative embodiment, the drive management system may automatically operate whenever the vehicle is in service. When activated, the central control unit 62 is supplied with information about the dynamic state of the vehicle 10 from sensors 44, 46, 48, 50, 52, 56. The central control unit 62 can evaluate the dynamic state of the vehicle as determined by parameters preset by the sensors and can therefore determine whether intervention is necessary.

  A common characteristic in the performance of all-wheel drive vehicles is a tendency to understeer when accelerating at a corner, and this phenomenon is commonly referred to as power understeer. The drive management system of the present invention is operable to reduce the effect of such power understeer. If the central control unit 62 determines that the vehicle 10 is understeered, it sends a command to the clutch controller 58 for the clutch mechanism 40 of the central differential gear unit. The controller 58 operates the clutch mechanism 40 and, as a result, changes the rotational speed of the propeller shaft 28. The clutch mechanism 40 is completely engaged so that the speed of the propeller shaft 28 and the speed of the internal drive shaft 39 coincide with each other, or the initial speed of the propeller shaft 28 before the clutch mechanism 40 is operated is determined by the internal drive shaft 39 Is partially engaged to drive the propeller shaft 28 at a desired speed between

  It will be understood that the operation of the clutch mechanism 40 increases the speed of the propeller shaft 28 because the gear ratios of the front and rear axle units 36, 30 are different. As a result, the rotational speed of the rear wheels 20 and 22 is increased, so that the rear wheels 20 and 22 are driven harder than the front wheels 16 and 18. After being driven harder than the tires of the front wheels 16 and 18. The tires of the wheels 20, 22 have a reduced lateral load carrying capacity and therefore a net yawing moment is applied to the vehicle.

  The above example relates to the control of a car under power understeer. The drive management system of the present invention is not limited to other situations, such as, for example, oversteer lift-off, sudden steering input to avoid obstacles, and situations in throttle position changes during cornering. It should be understood that intervention is possible.

  The sensors 44, 46, 48, 50, 52, 56 continue to monitor the dynamic state of the vehicle 10, so the central control unit 62 can drive the rear wheels 20, 22 more intensely than the front wheels 16, 18. The effect on the dynamic state of the vehicle 10 can be determined. The central control unit 62 therefore coordinates the operation of the clutch mechanism 40 of the central differential, so that the vehicle changes the dynamic state of the vehicle as a result of intervention of the clutch mechanism 40 in the central differential gear unit, as well as, for example, the road surface. It is ensured that the change in the characteristics of the vehicle and the change in the steering input applied to the steering wheel 45 from the driver are taken into account.

  As described above, the rear wheel axle (rear axle) unit 30 is provided with a clutch mechanism 42 that can be operated via a command sent from the central control unit 62. The clutch mechanism operates to change the drive shaft torque distribution from the rear wheel axle unit 30 to the rear wheels 20 and 22. The operation of the clutch mechanism 42 is either separate or supplemented from the drive management system described above.

  The above-described system has been described to increase the speed of the propeller shaft 28 to drive the rear wheels 20, 22 more aggressively, thereby reducing the side load carrying capacity of the rear wheel tire. However, it should be understood that the operation of the system can be altered to change the speed of the internal drive shaft 39 to approximate the rotational speed of the propeller shaft 28. In such an embodiment, it should be understood that the rotational speed of the internal drive shaft 39 is reduced by the action of reducing the drive force on the front wheels 16,18. This results in an increase in the lateral load carrying capacity of the front tire that reduces understeer occurring in the vehicle.

  In the above-described embodiment, the differential gear devices 36 and 30 of the front and rear axle units having a gear ratio different from that of the differential gear device of the rear wheel axle unit 30 having a lower gear ratio than the differential gear device of the front wheel axle unit. Can also be used. It should be understood that the same effect can be achieved by means other than a differential gear arrangement for front and rear axle units having different gear ratios. For example, an intermediate drop gear can be provided in the gear box between the central differential 38 and the propeller shaft 28. Generally, such a drop gear has a gear ratio of 1: 1. However, for example, by changing the gear ratio of the drop gear to 1.08: 1, the net ratio that increases the gear ratio of the rear wheel axle unit 30 is increased. An effect is obtained.

  The embodiment of the invention described with reference to FIG. 1 relates to a four-wheel drive vehicle with a driving force bias applied to the front wheels, i.e., during this vehicle's normal operation, the engine torque is a larger percentage than the front wheels. Divided to join. It should be understood that the principles underlying the present invention are equally applicable to rear wheel drive biased vehicles in which a greater percentage of engine torque is supplied to the rear wheels than to the front wheels. In such an embodiment, the final drive gear in the front wheel axle unit has a lower gear ratio than the final drive gear in the rear wheel axle unit.

It is a diagrammatic explanatory view for explaining the principle of the all-wheel drive system of the present invention.

Claims (15)

  An engine, a pair of front wheels having a drive shaft driven through a front wheel axle unit having a differential gear device, and a pair of rear wheels having a drive shaft operating via a rear wheel axle unit having a differential gear device A central differential gear device provided between the front wheel axle unit and the rear wheel axle unit, the front and rear propeller shafts extending from the central differential gear device to the front wheel axle unit and the rear wheel axle unit. In the all-wheel drive system for an automobile provided with the central differential gear device that transmits torque from the engine to the front wheel axle unit and the rear wheel axle unit via the front wheel axle unit, the final drive gear of the front wheel axle unit includes: The gear ratio is different from the final drive gear of the rear wheel axle unit, and further, the system is associated with the central differential gear mechanism. A synchronization means provided by, all-wheel drive system is characterized in that a structure with operable synchronizing means so as to vary the rotational speed of one or both of the front and rear of the propeller shaft.   The difference in gear ratio between the front wheel axle unit and the rear wheel axle unit is obtained by setting the final drive gear ratio of the front wheel axle unit to a gear ratio different from the final drive gear gear ratio of the rear wheel axle unit. The all-wheel drive system according to claim 1.   A difference in gear ratio between the front wheel axle unit and the rear wheel axle unit is obtained by providing an intermediate gear device between the central differential gear device and one of the rear wheel axle unit and the front wheel axle unit. The all-wheel drive system according to claim 1.   The all-wheel drive system according to claim 3, wherein the intermediate gear device is a single gear provided between the central differential gear device and one of the front wheel axle unit and the rear wheel axle unit.   The all-wheel drive system according to claim 4, wherein the intermediate gear device is a single gear provided between the central differential gear device and one of the front propeller shaft and the rear propeller shaft.   The all-wheel drive system according to any one of claims 1 to 5, wherein a difference in gear ratio between the front wheel axle unit and the rear wheel axle unit is set to a value within a range of 3% to 10%.   The said synchronizing means shall have a clutch mechanism which can be operated so that the rotational speed of one or both of the said front propeller shaft and a back propeller shaft may be changed. All-wheel drive system.   8. The all-wheel drive system according to claim 7, wherein the clutch mechanism includes a first state in which the front propeller shaft and the rear propeller shaft can rotate relatively freely, and the front propeller shaft and the rear propeller shaft in a specific rotation. An all-wheel drive system capable of operating between a second state that is maintained and cannot rotate relative to each other.   9. The all-wheel drive system according to claim 7, wherein the clutch mechanism is operable to increase the rotational speed of the rear propeller shaft to approach the rotational speed of the front propeller shaft.   9. The all-wheel drive system according to claim 7, wherein the clutch mechanism is operable to reduce the rotation speed of the front propeller shaft to approach the rotation speed of the rear propeller shaft.   9. The all-wheel drive system according to claim 7 or 8, wherein the clutch mechanism is operable to change the rotational speeds of both the front propeller shaft and the rear propeller shaft.   The all-wheel drive system according to any one of claims 1 to 11, wherein the synchronization means includes a controller that responds to a dynamic state of a vehicle.   13. The all-wheel drive system according to claim 12, wherein the controller is provided with a number of sensors positioned to sense vehicle operating characteristics.   13. The all-wheel drive system according to claim 12, wherein the sensors include one or more wheel speed sensors, lateral acceleration sensors, longitudinal acceleration sensors, steering input sensors, engine torque request sensors, and vehicle yaw sensors. All-wheel drive system with In a method of affecting or modifying the dynamic behavior of an all-wheel drive vehicle by distributing drive torque across the vehicle, the following steps:
Engine, a pair of front wheels having a drive shaft driven through a front wheel axle unit having a differential gear device, a pair of rear wheels having a drive shaft driven through a rear wheel axle having a differential gear device A central differential gear device provided between the front wheel axle unit and the rear wheel axle unit, the front and rear propellers extending from the central differential gear device to the front wheel axle unit and the rear wheel axle unit. An all-wheel drive vehicle having the central differential gear device for transmitting torque from the engine to the front wheel axle unit and the rear wheel axle unit via a shaft, respectively, wherein the final drive gear of the front wheel axle unit is The rear wheel axle unit has a gear ratio different from that of the final drive gear, and the system is a synchronization means provided in association with the central differential gear mechanism. A step for preparing a 該全 wheel drive vehicle having a structure with operable synchronizing means so as to vary the rotational speed of one or both of the front and rear of the propeller shaft,
Providing the vehicle with a plurality of sensors operable to monitor the dynamic behavior of the vehicle;
Providing a controller configured to receive input from a sensor, wherein the controller is provided with one or more vehicle dynamic behavior parameters;
Sensing, via one or more sensors, whether the dynamic behavior of the vehicle has reached or exceeded a predetermined parameter value in one or more of one or more dynamic behavior parameters; ,
A dynamic behavior of an all-wheel drive vehicle, comprising: operating the synchronization means via the controller; and changing a rotational speed of one or both of the front propeller shaft and the rear propeller shaft. Modification method.

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