Two-stage rotary expander, expander-integrated compressor, and refrigeration cycle apparatus

1. A two-stage rotary expander comprising:

a first cylinder;

a first piston disposed rotatably in the first cylinder;

a second cylinder disposed concentrically with the first cylinder;

a second piston disposed rotatably in the second cylinder;

a shaft on which the first piston and the second piston are mounted;

a first vane, disposed slidably in a first vane groove formed in the first cylinder, for partitioning a space between the first cylinder and the first piston into a first suction space and a first discharge space;

a second vane, disposed slidably in a second vane groove formed in the second cylinder, for partitioning a space between the second cylinder and the second piston into a second suction space and a second discharge space;

an intermediate plate for separating the first cylinder from the second cylinder, the intermediate plate having a through-hole that communicates the first discharge space with the second suction space so as to form one expansion chamber; and

a variable vane mechanism comprising a stopper for changing a range of the movement of the first vane, the variable vane mechanism being configured to control movement of the first vane so that a ratio of a period P 2 to a period P 1 (P 2 /P 1 ) can be adjusted, where P 1 denotes the period during which the first vane is in contact with the first piston in the course of one rotation of the shaft, and P 2 denotes the period during which the first vane is spaced from the first piston in the course of one rotation of the shaft,

wherein the stopper constantly engages the first vane, and

there are more than two levels of the ratio (P 2 /P 1 ) to be set by the variable vane mechanism.

2. The two-stage rotary expander according to claim 1 , wherein the first vane is detached from the first piston in the course of expansion of a working fluid in the expansion chamber, so that a working fluid to be expanded is injected into the expansion chamber.

3. The two-stage rotary expander according to claim 1 ,

the variable vane mechanism further includes

an actuator for moving the stopper between a first position and a second position so as to change the range of the movement of the first vane continuously or in a stepwise manner,

wherein the first vane is movable within a first range when the actuator is in the first position, the first vane is movable within a second range when the actuator is in the second position, and the second range is shorter than the first range.

4. The two-stage rotary expander according to claim 3 , wherein

the actuator is a fluid pressure actuator, and

the fluid pressure actuator includes:

a main body that includes a portion working with the stopper, and determines, based on a pressure of a fluid, a position of the stopper with respect to a longitudinal direction of the first vane groove;

a pressure chamber in which the main body is placed; and

a passage for supplying the fluid to the pressure chamber.

5. The two-stage rotary expander according to claim 4 , wherein

the main body includes a slider disposed slidably in the pressure chamber to partition the pressure chamber into sections, and a spring provided in one section of the pressure chamber partitioned by the slider,

the stopper is integrated with or coupled to the slider,

the passage is connected to the other section of the pressure chamber partitioned by the slider, and

the position of the stopper with respect to the longitudinal direction of the first vane groove is determined based on a force applied to the slider by the fluid that has been supplied through the passage and a force applied to the slider by the spring.

6. The two-stage rotary expander according to claim 4 , wherein

the first vane has a recessed portion for receiving the stopper,

the pressure chamber of the fluid pressure actuator is formed adjacent to the first vane groove, and

one end of the stopper is fixed to the slider and the other end of the stopper is constantly inserted into the recessed portion so that the stopper extends from the pressure chamber to the first vane groove.

7. The two-stage rotary expander according to claim 3 , wherein

the actuator is an electric actuator, and

the electric actuator and the stopper are coupled together so that the position of the stopper with respect to the longitudinal direction of the first vane groove changes when the electric actuator is driven.

8. The two-stage rotary expander according to claim 3 , wherein

the actuator is a fluid pressure actuator,

the two-stage rotary expander further comprises a suction pipe and a pressure supply circuit configured to supply a working fluid, whose pressure is adjusted, to the fluid pressure actuator,

the pressure supply circuit comprises a pressure supply pipe branching from the suction pipe and connected to the fluid pressure actuator, and a throttle valve provided on the pressure supply pipe, and

the throttle valve is an opening-adjustable valve.

9. The two-stage rotary expander according to claim 8 , further comprising a discharge pipe, wherein the pressure supply circuit further comprises a fine passage branching from a portion of the pressure supply pipe between the throttle valve and the variable vane mechanism and connected to the discharge pipe.

10. The two-stage rotary expander according to claim 9 , wherein the fine passage comprises a capillary.

11. A two-stage rotary expander comprising:

a first cylinder;

a first piston disposed rotatably in the first cylinder;

a second cylinder disposed concentrically with the first cylinder;

a second piston disposed rotatably in the second cylinder;

a shaft on which the first piston and the second piston are mounted;

a first vane, disposed slidably in a first vane groove formed in the first cylinder, for partitioning a space between the first cylinder and the first piston into a first suction space and a first discharge space;

a second vane, disposed slidably in a second vane groove formed in the second cylinder, for partitioning a space between the second cylinder and the second piston into a second suction space and a second discharge space;

an intermediate plate for separating the first cylinder from the second cylinder, the intermediate plate having a through-hole that communicates the first discharge space with the second suction space so as to form one expansion chamber; and

a variable vane mechanism configured to control movement of the first vane so that a ratio of a period P 2 to a period P 1 (P 2 /P 1 ) can be adjusted, where P 1 denotes the period during which the first vane is in contact with the first piston in the course of one rotation of the shaft, and P 2 , denotes the period during which the first vane is spaced from the first piston in the course of one rotation of the shaft, and

an oil reservoir for storing oil for lubrication,

wherein the variable vane mechanism controls the movement of the first vane so that a confined volume of the expansion chamber can be adjusted by changing the ratio (P 2 /P 1 ), when a point in time when the first piston reaches a top dead center is a starting point of the period P 2 , and

the variable vane mechanism includes:

an oil chamber that communicates with the first vane groove so that the oil can be supplied to the first vane groove and the oil can be received from the first vane groove;

an oil passage, for supplying the oil in the oil reservoir to the oil chamber, and for discharging the oil in the oil chamber to the oil reservoir; and

an opening-adjustable valve provided in the oil passage so that a flow resistance of the oil passage can be increased or decreased.

12. The two-stage rotary expander according to claim 11 , wherein the variable vane mechanism is constructed to prevent the first vane from following movement of the first piston.

13. The two-stage rotary expander according to claim 11 , wherein

the oil passage includes a first oil passage provided with the opening-adjustable valve, and a second oil passage that communicates the oil chamber with the oil reservoir by a route different from the first oil passage,

the variable vane mechanism further includes a second valve provided in the second oil passage, and

a direction of flow of the oil in the second oil passage is limited substantially only to a direction from the oil chamber to the oil reservoir by the second valve.

14. The two-stage rotary expander according to claim 11 , wherein

the variable vane mechanism includes a coil for applying an electromagnetic force to the first vane to prevent the first vane from following the movement of the first piston, and

a timing of supplying electric current to the coil can be controlled externally.

15. The two-stage rotary expander according to claim 14 , wherein a supply of electric current to the coil is controlled based on a rotation angle of the shaft.

16. The two-stage rotary expander according to claim 11 , wherein

the variable vane mechanism includes an electric actuator for applying a load to the first vane to increase sliding friction between the first vane groove and the first vane, and

driving of the electric actuator can be controlled externally.

17. The two-stage rotary expander according to claim 11 , wherein

the opening-adjustable valve is a valve whose opening is adjusted according to a pressure of a control fluid,

the two-stage rotary expander further comprises a suction pipe and a pressure supply circuit configured to supply the control fluid, whose pressure is adjusted, to the opening-adjustable valve,

the control fluid is a working fluid used in the two-stage rotary expander,

the pressure supply circuit comprises a pressure supply pipe branching from the suction pipe and connected to the variable vane mechanism, and a throttle valve provided on the pressure supply pipe, and

the throttle valve is an opening-adjustable valve.

18. The two-stage rotary expander according to claim 17 , further comprising a discharge pipe, wherein the pressure supply circuit further comprises a fine passage branching from a portion of the pressure supply pipe between the throttle valve and the variable vane mechanism and connected to the discharge pipe.

19. The two-stage rotary expander according to claim 18 , wherein the fine passage comprises a capillary.