[Claim 1]
A twin rotary compressor that includes
an electric motor including a stator and a rotor,
5 a crankshaft that is rotated by the electric motor, the crankshaft including a
main shaft secured to the rotor, a first offset portion located on the main shaft, and a second offset portion located on the main shaft,
a first piston located on the first offset portion,
a second piston located on the second offset portion,
0 a first cylinder having a cylindrical through-hole in which the first offset portion
and the first piston are arranged to define a first compression chamber, and
a second cylinder having a cylindrical through-hole in which the second offset
portion and the second piston are arranged to define a second compression chamber,
the twin rotary compressor comprising
5 an injection passage through which refrigerant is injected into the first
compression chamber and the second compression chamber from a refrigerant pipe located outside the twin rotary compressor,
the injection passage including a first injection port located in the first
compression chamber, a second injection port located in the second compression
0 chamber, an injection inlet pipe connected to the refrigerant pipe, a first injection pipe
through which the refrigerant is supplied to the first injection port, a second injection
pipe through which the refrigerant is supplied to the second injection port, and an
injection muffler that is interposed between the injection inlet pipe and the first and
second injection pipes and has a larger inside diameter than do the first and second
5 injection pipes,
the first injection pipe and the second injection pipe being separately connected to the injection muffler. [Claim 2]

The twin rotary compressor of claim 1, wherein the first injection pipe and the
second injection pipe protrude upward into the injection muffler in lower part of the
injection muffler.
[Claim 3]
5 The twin rotary compressor of claim 2, wherein the injection inlet pipe protrudes
downward into the injection muffler in upper part of the injection muffler and is apart
from the first injection pipe and the second injection pipe protruding upward into the
injection muffler.
[Claim 4]
10 The twin rotary compressor of claim 2 or 3, wherein each of the first injection
pipe and the second injection pipe protrudes into the injection muffler by a protruding
amount corresponding to a length that enables injection of either one of gas
refrigerant and liquid refrigerant.
[Claim 5]
15 The twin rotary compressor of any one of claims 1 to 4, wherein the first
injection pipe and the second injection pipe each have a combination of L [m] and d
[m] given below that provides a supercharging rate a [%] expressed by a relational
equation (Eq. 1) given below and exceeding 100%:
a = K x (L/d5) ... (Eq. 1)
20 where a [%] satisfies a > 100 [%],
L [m] is a length of the first injection pipe or the second injection pipe, d [m] is an inside diameter of the first injection pipe or the second injection pipe, and
K [kg-m3/(s2-Pa)] is a coefficient that correlates with X, p, Q, and Pbase.
25 [Claim 6]
The twin rotary compressor of claim 5, wherein the first injection pipe and the second injection pipe each have a combination of L and d providing a that satisfies (amax + 1)/2 < a < amax, where amax is a maximum value of a. [Claim 7]

The twin rotary compressor of any one of claims 1 to 6, wherein the first injection pipe and the second injection pipe have different inside diameters. [Claim 8]
The twin rotary compressor of claim 7, wherein one of the first injection pipe
5 and the second injection pipe that has a smaller inside diameter than does an other
one of the first injection pipe and the second injection pipe has a shorter length than does the other one. [Claim 9]
The twin rotary compressor of any one of claims 1 to 8, wherein the first
10 injection pipe includes a connection portion connected to the first injection port, the
second injection pipe includes a connection portion connected to the second injection
port, and at least one of the connection portion of the first injection pipe and the
connection portion of the second injection pipe includes a connecting pipe having a
smaller inside diameter than does a corresponding one of the first injection pipe and
15 the second injection pipe.
[Claim 10]
The twin rotary compressor of claim 2 or any one of claims 3 to 9 as dependent
on claim 2, wherein the first injection pipe and the second injection pipe protrude into
the injection muffler by different protruding amounts.
20 [Claim 11]
The twin rotary compressor of claim 10, wherein one of the first injection pipe
and the second injection pipe that protrudes into the injection muffler by a larger
protruding amount than does an other one of the first injection pipe and the second
injection pipe has a shorter length than does the other one.
25 [Claim 12]
The twin rotary compressor of any one of claims 1 to 11, further comprising
a suction muffler connected to a pipe through which the refrigerant is supplied to the twin rotary compressor,
wherein the injection muffler has a volume that is 5% or more of a volume of
30 the suction muffler.

[Claim 13]
The twin rotary compressor of any one of claims 1 to 12, wherein the injection
muffler is secured to an outer circumferential surface of a hermetic container of the
twin rotary compressor.
5 [Claim 14]
A refrigeration cycle apparatus comprising
the twin rotary compressor of any one of claims 1 to 13.