# US 2008/0184723 A1 · Multistage compressor

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- Number: US 2008/0184723 A1
- Document ID: US20080184723A1
- Status: Published application
- Kind: A1
- Application number: 12/010,784
- Filed: 2008-01-30
- Published: 2008-08-07
- Earliest claimed: 2007-02-02
- Assignees: Mitsubishi Heavy Industries, Ltd.
- Inventors: Hajime Sato; Yoshiyuki Kimata
- Web page: https://patentgrep.com/patent/US20080184723A1

## CPC

- F04C 23/008: {Hermetic pumps}
- B60H 1/3228: {characterised by refrigerant circuit configurations}
- F04C 28/06: specially adapted for stopping, starting, idling or no-load operation
- F04C 28/26: using bypass channels
- F25B 1/10: with multi-stage compression (with cascade operation F25B7/00)
- F25B 49/022: {Compressor control arrangements}
- F04C 18/0215: {where only one member is moving}
- F04C 18/356: with vanes reciprocating with respect to the outer member
- F25B 2400/13: Economisers
- F25B 2400/23: Separators
- F25B 2600/0261: external to the compressor
- F25B 2600/2509: Economiser valves
- F25B 2700/1933: Suction pressures
- F25B 2700/21151: at the suction side of the compressor
- F04C: ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS (engines F03C); ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- B60H: ARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
- F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS

## Abstract

To provide a multistage compressor including an injection circuit, which can continue high-efficiency and high-capacity operations even if the injection circuit is turned on/off in accordance with operating conditions. A multistage compressor includes a high stage side compressing mechanism suctioning the intermediate pressure refrigerant gas compressed with a low stage side compressing mechanism to perform two-stage compression, and an injection circuit for injecting an intermediate pressure refrigerant into the intermediate pressure refrigerant gas suctioned to the high stage side compressing mechanism, the high stage side compressing mechanism including a capacity control mechanism for bypassing a refrigerant gas that is being compressed to a suction side, the injection circuit including an on/off mechanism for performing on/off control of refrigerant injection, and the capacity control mechanism and the on/off mechanism being operated in conjunction with each other.

## Claims

### Claim 1

A multistage compressor, comprising:
a low stage side compressing mechanism and a high stage side compressing mechanism provided in a housing with the low stage side compressing mechanism compressing an intermediate pressure refrigerant gas and the high stage side compressing mechanism suctioning the compressed intermediate pressure refrigerant gas to perform two-stage compression; and
an injection circuit for injecting an intermediate pressure refrigerant extracted from a refrigerant circuit into the intermediate pressure refrigerant gas suctioned to the high stage side compressing mechanism,
the high stage side compressing mechanism including a capacity control mechanism for bypassing a refrigerant gas that is being compressed to a suction side,
the injection circuit including an on/off mechanism for performing on/off control of refrigerant injection, and
the capacity control mechanism and the on/off mechanism being operated in conjunction with each other.

### Claim 2 (depends on 1)

The multistage compressor according to claim 1, wherein if the on/off mechanism turns off the injection circuit, the capacity control mechanism controls a capacity of the high stage side compressing mechanism.

### Claim 3 (depends on 2)

The multistage compressor according to claim 2, wherein a capacity control rate of the capacity control mechanism at least under a condition that the on/off mechanism turns off the injection circuit is set to correspond to pressure ratio distribution obtained when the injection circuit is turned on with a full capacity.

### Claim 4 (depends on 1)

The multistage compressor according to claim 1, wherein the capacity control mechanism is forcedly turned on and the injection circuit is forcedly turned off at startup.

### Claim 5 (depends on 4)

The multistage compressor according to claim 4, wherein after the startup, the capacity control mechanism is turned on and the injection circuit is turned on, and then an operation is shifted to a full-load operation in which the capacity control mechanism is turned off and the injection circuit is turned on.

### Claim 6 (depends on 1)

The multistage compressor according to claim 1, wherein during a liquid flowback operation, the capacity control mechanism is forcedly turned on and the injection circuit is forcedly turned off.

### Claim 7 (depends on 1)

The multistage compressor according to claim 1, wherein the housing is an intermediate pressure housing in which an intermediate pressure refrigerant gas compressed with the low stage side compressing mechanism is discharged, an intermediate pressure refrigerant is injected from the injection circuit, and an intermediate pressure refrigerant gas is bypassed from the capacity control mechanism.

### Claim 8 (depends on 1)

The multistage compressor according to claim 1, wherein the high stage side compressing mechanism is a scroll compressing mechanism.