Scroll expander with back pressure chamber

1. A scroll expander, comprising:

a housing; and

an expansion mechanism provided inside the housing and configured to expand a high-pressure fluid with an intake pressure to a low-pressure fluid with an exhaust pressure, the expansion mechanism comprising a fixed scroll and an orbiting scroll and defining therein an exhaust chamber, an intake chamber and a series of closed expansion chambers, wherein a back pressure chamber is provided on the expansion mechanism, and the back pressure chamber is in fluid communication with an intermediate pressure chamber of the series of expansion chambers which has an intermediate pressure lower than the intake pressure and higher than the exhaust pressure,

wherein at least one passage in fluid communication from the back pressure chamber to a low-pressure zone with the exhaust pressure is provided, and the passage is configured such that the passage is opened when a pressure in the back pressure chamber is less than a pressure in the low-pressure zone and the passage is closed when a pressure in the back pressure chamber is greater than or equal to a pressure in the low-pressure zone.

2. The scroll expander according to claim 1 , wherein the fixed scroll is capable of floating axially relative to the orbiting scroll.

3. The scroll expander according to claim 2 , wherein the back pressure chamber is provided at a back side of an end plate of the fixed scroll, and the back pressure chamber is sealed by a floating sealing ring.

4. The scroll expander according to claim 3 , wherein the low-pressure zone comprises a low-pressure area outside the expansion mechanism and the exhaust chamber of the expansion mechanism which is directly communicated with the low-pressure area, and the passage is provided in the end plate of the fixed scroll and is directly communicated with the low-pressure area or directly communicated with the exhaust chamber.

5. The scroll expander according to claim 1 , wherein a check valve capable of closing and opening the passage is provided at the passage such that the passage is opened when a pressure in the back pressure chamber is less than a pressure in the low-pressure zone and the passage is closed when a pressure in the back pressure chamber is greater than or equal to a pressure in the low-pressure zone.

6. The scroll expander according to claim 5 , wherein the passage comprises an orifice that opens into the back pressure chamber, and the check valve is provided at the orifice to close and open the orifice.

7. The scroll expander according to claim 6 , wherein the check valve comprises a valve plate and a valve stopper provided at the orifice, and the valve plate is provided as an elastically deformable valve plate fixed at one end or as an integrally movable valve plate, and the valve stopper is provided so that the valve plate is disposed between the orifice and the valve stopper.

8. The scroll expander according to claim 1 , wherein the back pressure chamber and the intermediate pressure chamber are in fluid communication through a breathing hole, and an inner diameter of the passage is larger than an inner diameter of the breathing hole.

9. The scroll expander according to claim 2 , wherein the back pressure chamber and the intermediate pressure chamber are in fluid communication through a breathing hole, and an inner diameter of the passage is larger than an inner diameter of the breathing hole.

10. The scroll expander according to claim 3 , wherein the back pressure chamber and the intermediate pressure chamber are in fluid communication through a breathing hole, and an inner diameter of the passage is larger than an inner diameter of the breathing hole.

11. The scroll expander according to claim 4 , wherein the back pressure chamber and the intermediate pressure chamber are in fluid communication through a breathing hole, and an inner diameter of the passage is larger than an inner diameter of the breathing hole.

12. The scroll expander according to claim 5 , wherein the back pressure chamber and the intermediate pressure chamber are in fluid communication through a breathing hole, and an inner diameter of the passage is larger than an inner diameter of the breathing hole.

13. The scroll expander according to claim 6 , wherein the back pressure chamber and the intermediate pressure chamber are in fluid communication through a breathing hole, and an inner diameter of the passage is larger than an inner diameter of the breathing hole.

14. The scroll expander according to claim 7 , wherein the back pressure chamber and the intermediate pressure chamber are in fluid communication through a breathing hole, and an inner diameter of the passage is larger than an inner diameter of the breathing hole.

15. The scroll expander according to claim 3 , wherein a spring assembly is provided in the back pressure chamber, and an upper end of the spring assembly abuts against the floating sealing ring, and a lower end of the spring assembly abuts against a bottom wall of the back pressure chamber.

16. The scroll expander according to claim 4 , wherein a spring assembly is provided in the back pressure chamber, and an upper end of the spring assembly abuts against the floating sealing ring, and a lower end of the spring assembly abuts against a bottom wall of the back pressure chamber.

17. The scroll expander according to claim 15 , wherein the spring assembly comprises at least one supporting element that abuts against the floating sealing ring and at least one elastic element that is provided below the supporting element and abuts against the bottom wall of the back pressure chamber.

18. The scroll expander according to claim 17 , wherein the supporting element is a ring-shaped sheet and the elastic element is a ring-shaped element with an uneven shape in the circumferential direction.