Scroll expander with exhaust path thru bearings and a partition plate
A housing of a scroll type expansion machine includes: a suction port formed at a position on the opposite side to a drive shaft with a fixed scroll interposed therebetween; a discharge port formed on the side of a drive-side bearing closer to the tip end of the drive shaft; a low pressure chamber formed on the outer side of an orbiting-side scroll portion when viewed from the axial direction of the drive shaft; and a tip end-side low-pressure space being a space in which a sealing member is disposed, and has: a partition wall partitioning the tip end-side low-pressure space and the low-pressure chamber from each other; and a communication space communicating the tip end-side low-pressure space with the low-pressure chamber.
1. A scroll expander used in a Rankine cycle in which a working fluid circulates, comprising:
a housing formed of a front housing and a rear housing;
a drive shaft a base end of which is housed in the housing and a tip end of which projects out of the housing;
a fixed scroll fixed to a side closer to the base end of the drive shaft rather than to the tip end of the drive shaft inside the housing;
an orbiting scroll arranged on a side of the fixed scroll closer to the tip end of the drive shaft in a rotatable structure inside the housing;
a bearing arranged on a side of the orbiting scroll closer to the tip end of the drive shaft inside the housing and configured to support the drive shaft in a rotatable structure with respect to the housing via a plurality of rolling elements; and
a sealing member arranged on a side of the bearing closer to the tip end of the drive shaft inside the housing and configured to surround an outer peripheral surface of the drive shaft, wherein
the fixed scroll has a fixed-side scroll portion formed in a spiral shape when viewed from an axial direction of the drive shaft,
the orbiting scroll has an orbiting-side scroll portion formed in a spiral shape when viewed from the axial direction of the drive shaft and meshing with the fixed-side scroll portion,
the housing includes a suction port formed at a position on an opposite side to the drive shaft with the fixed scroll interposed between the suction port and the drive shaft and configured to introduce high-pressure working fluid from an external circuit, a discharge port formed on a side of the bearing closer to the tip end of the drive shaft and configured to discharge low-pressure working fluid to an external circuit, a low pressure chamber formed on an outer side of the orbiting-side scroll portion when viewed from an axial direction of the drive shaft, and a tip end-side low-pressure space being a space in which the sealing member is arranged,
the front housing is provided with a partition wall configured to partition the tip end-side low-pressure space and the low pressure chamber from each other, the partition wall being disposed at a position located between the tip end-side low-pressure space and the low pressure chamber when viewed from a radial direction of the drive shaft and located closer to the discharge port than the drive shaft when viewed from the axial direction of the drive shaft,
a communication space configured to communicate the tip end-side low-pressure space with the low pressure chamber is disposed at a position located between the tip end-side low-pressure space and the low pressure chamber when viewed from a radial direction of the drive shaft and opposed to the discharge port with a center of the drive shaft interposed between the position and the discharge port when viewed from the axial direction of the drive shaft; and
when the low-pressure working fluid that has moved from the communication space to the tip end-side low-pressure space flows to the discharge port, the low-pressure working fluid actively flows around the sealing member exposed in the tip end-side low-pressure space to actively cool the sealing member.
2. The scroll expander according to claim 1 , wherein
the partition wall is arranged on an outer side of the bearing in radial directions of the drive shaft.
3. The scroll expander according to claim 2 , wherein
the communication space is arranged on an outer side of the bearing in radial directions of the drive shaft.
4. The scroll expander according to claim 2 comprising
a rotation preventing mechanism configured to prevent the orbiting scroll from rotating, wherein
the rotation preventing mechanism includes a ball coupling including a plurality of balls arranged in a radial structure with a gap interposed between each pair of adjacent balls when viewed from the axial direction of the drive shaft, and
gaps formed between adjacent balls communicate the tip end-side low-pressure space with the low-pressure chamber.
5. The scroll expander according to claim 1 , wherein
the communication space is arranged on an outer side of the bearing in radial directions of the drive shaft.
6. The scroll expander according to claim 5 comprising
a rotation preventing mechanism configured to prevent the orbiting scroll from rotating, wherein
the rotation preventing mechanism includes a ball coupling including a plurality of balls arranged in a radial structure with a gap interposed between each pair of adjacent balls when viewed from the axial direction of the drive shaft, and
gaps formed between adjacent balls communicate the tip end-side low-pressure space with the low-pressure chamber.
7. The scroll expander according to claim 1 comprising
a rotation preventing mechanism configured to prevent the orbiting scroll from rotating, wherein
the rotation preventing mechanism includes a ball coupling including a plurality of balls arranged in a radial structure with a gap interposed between each pair of adjacent balls when viewed from the axial direction of the drive shaft, and
gaps formed between adjacent balls communicate the tip end-side low-pressure space with the low-pressure chamber.