| 摘要 |
A power transmission apparatus for a four-wheel drive vehicle has a first rotary shaft for transmitting drive force to front wheels of the vehicle, a second rotary shaft for transmitting drive force to rear wheels of the vehicle, and a hydraulic pump connecting the first and second rotary shafts and driven by a difference in rotational speed between the first and second rotary shafts to deliver hydraulic oil in an amount depending on the difference in rotational speed. A suction passage and a delivery passage is changed over in dependence on relative rotational direction of the first and second rotary shafts. An expansion chamber communicates with the suction passages and delivery through a restriction to temporarily suppress an increase in pressure of hydraulic oil delivered from the hydraulic pump, thereby suppressing transmission of a drive force by the hydraulic pump when the variation in relative rotation speed between the first and second rotary shafts is small.
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