1. Field of the Invention
The present invention relates to a differential apparatus for vehicles.
2. Description of Relevant Art
There has been disclosed in Japanese Patent Application Laid-Open Publication No. 7-156681 a differential apparatus of an arrangement shown in FIG. 1, where it is designated by reference character 201.
The differential apparatus 201 includes a differential mechanism 207 for distributing drive power from an engine to a pair of left and right drive axles 203, 205, a pair of left and right drive power control mechanisms 215 each comprising a combination of a multi-plate clutch 211 and a speed change mechanism 213 for a serial connection between a differential casing 209 of the mechanism 207 and the left or right axle 203 or 205, and a hydraulic actuator 220 for actuating the clutch 211 to be internally coupled for the connection, and a hydraulic controller 230 for controlling the actuator 220 to have the clutch 211 coupled.
If the multi-plate clutch 211 of the left drive power control mechanism 215 is coupled, drive power distributed to the left axle 203 has its fraction fed back via the speed change mechanism 213 and that clutch 211 to the differential casing 209, with the more distributed drive power at the right axle 205 end. To the contrary, if the multi-plate clutch 211 of the right drive power control mechanism 215 is coupled, drive power distributed to the right axle 205 has its fraction fed back to via the speed change mechanism 213 and this clutch 211 to the differential casing 209, with the more distributed drive power at the left axle 203 end.
The controller 230 is thus adaptive for coupling the multi-plate clutch 211 of the left or right drive power control mechanism 215 to control a yaw momentum of a vehicle body, securing a stable straight forward travel as well as a comfortable steering to turn.
More specifically, when the vehicle body in travel has entered a yawing due to a slipping road wheel at the left or right axle 203 or 205 end, the drive power control mechanisms 215 are controlled to stop the slipping.
It therefore is impossible for the differential apparatus 201 to limit a developing difference at the differential mechanism 207 before the road wheel slips, and to effect a prevention of a wheel slippage before a development of yaw momentum on the vehicle body in a straight forward travel.
The respective multi-plate clutches 211, which are arranged between the differential casing 209 and the left and right axle 203, 205, might have been operated for a use of their frictional torque to limit a difference development at the differential mechanism 207. However, if the clutches 211 were both coupled for the difference limitation, those fractions of drive power fed back from the left and right axle 203, 205 ends would have canceled each other. Still worse, during such the limitation, the multi-plate clutches 211 should have stood with a big burden due to slippage, resulting in a reduced service life.
In addition, associated drive torque to be fed back is subjected to an amplification at the speed change mechanism 213 adversely affecting the vehicle body in performance, rendering control of difference limitation very difficult.
The differential apparatus 201 may involve a difference limiting mechanism, with an arrangement the more complicated, large sized, increased in weight and dear of cost.
There has been disclosed in Japanese Patent Application Laid-Open Publication No. 5-345535 another differential apparatus shown in FIG. 2, where it is designated by reference character 301.
The differential apparatus 301 comprises an input part 302 for inputting drive power from an engine, a differential mechanism 303 of a planetary gear type, and a drive power control mechanism 305.
The drive power control mechanism 305 includes a speed changing mechanism 313 as an integrated combination of a speed increasing mechanism 313a for transmitting a fraction of drive power of a left drive axle 307 to a first intermediate shaft 311, with an increased revolution speed, and a speed decreasing mechanism 313b for transmitting a fraction of drive power of the left axle 307 to a second intermediate shaft 315, with a decreased revolution speed. The control mechanism 305 further includes a hydraulically actuatable first multi-plate clutch 317 to be coupled for interconnection between the first intermediate shaft 311 and a right drive axle 309, and a hydraulically actuatable second multi-plate clutch 319 to be coupled for interconnection between the second intermediate shaft 315 and the right axle 309.
In other words, the drive power control mechanism 305 is adaptive for a serial connection between the left and right axles 307, 309 with the first and second multi-plate clutches 317, 319 controlled to be either coupled by a hydraulic controller 330 to achieve a secured stable straight forward travel as well as a comfortable steering to turn.
This differential apparatus 301 has similar issues to that differential apparatus 201.