Patent Description:
In general, a refrigerant circuit of an air-conditioning apparatus includes a compressor, a condenser, an expansion valve, and an evaporator. The air-conditioning apparatus is configured to suck, compress, and discharge refrigerant repeatedly by the compressor. Through repeated operation of the air-conditioning apparatus, the refrigerant is discharged in a pulsed manner, with the result that pressure of the refrigerant fluctuates. This phenomenon is called a pressure pulsation. There is a problem in that the pressure pulsation may be transmitted from the compressor through a discharge pipe of the compressor to an indoor-side heat exchanger, and cause resonance with the structure of the indoor-side heat exchanger, resulting in generation of noise. This noise is referred to as a pulsation noise.

Thus, in the refrigerant circuit of the air-conditioning apparatus, a muffler is mounted to a pipe extending from a discharge port of the compressor to the indoor-side heat exchanger to reduce the pulsation noise.

When basic characteristics of the muffler are taken into account, in order to enhance a muffling effect, a cross sectional area ratio of an expansion chamber of a muffler main body to a pipe connected to a muffler main body needs to be set large. In view of such circumstance, for example, there has been proposed a muffler employing a configuration in which an inner diameter of the muffler main body is set large so that the muffling effect is enhanced when the cross sectional area of the pipe is fixed (see, for example, Patent Literature <NUM>).

Further, in order to achieve downsizing of the muffler, there has been proposed a muffler downsized by changing a length and a diameter of an insertion pipe inserted into the muffler main body (see, for example, Patent Literature <NUM>). In the muffler according to Patent Literature <NUM>, a muffling property is enhanced by reducing an inner diameter of an inlet pipe connected to an inlet of the muffler main body before the inlet pipe enters the muffler main body, and by positioning a distal end of a portion of the inlet pipe, which is inserted into the muffler main body, at a center of the muffler main body. Thereby, Patent Literature <NUM> discloses a muffler according to the preamble of claim <NUM>.

In the muffler proposed in Patent Literature <NUM>, in order to enhance the muffling effect, the cross sectional area ratio of the expansion chamber of the muffler main body to the pipe connected to the muffler main body needs to be set large. Thus, there is a problem in that, when the inner diameter of the pipe connected to the muffler main body cannot be changed, the inner diameter of the muffler main body may disadvantageously increase.

In the muffler proposed in Patent Literature <NUM>, in order to downsize the muffler while the muffling effect is maintained, an inner diameter of the inlet pipe is reduced also before the portion which is inserted into the muffler main body, and a length of an inserted pipe portion which is inserted into the muffler main body is set large to reach the vicinity of the center of the muffler main body. However, there is a problem in that a pressure loss of the refrigerant may increase.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a muffler for an air-conditioning apparatus, which is downsized and has an enhanced muffling effect while the pressure loss of the refrigerant is suppressed to maintain efficiency of a heat exchange, and an air-conditioning apparatus including the muffler for an air-conditioning apparatus.

According to a first embodiment of the present invention, there is provided a muffler for an air-conditioning apparatus, as defined in claim <NUM>.

According to another embodiment there is proposed an air-conditioning apparatus comprising the muffler of the first embodiment, as defined in claim <NUM>.

According to the muffler for an air-conditioning apparatus of one embodiment of the present invention, the pressure loss of the refrigerant can be suppressed to be smaller than that of the related art while the muffling effect is maintained without increasing a size of the muffler main body, by positioning the distal end of the inlet pipe at the center of the length from the inlet to the outlet of the muffler main body and by setting the inner diameter of the inlet pipe on the distal end portion side smaller than the inner diameter of the inlet pipe on upstream of the distal end side.

<FIG> is a refrigerant circuit diagram for illustrating an air-conditioning apparatus during a heating operation according to Embodiment <NUM> of the present invention. In <FIG>, a four-way valve <NUM> is switched to the heating operation (see the solid line of <FIG>). During the heating operation, a compressor <NUM>, the four-way valve <NUM>, an indoor heat exchanger <NUM>, an expansion valve <NUM>, an outdoor heat exchanger <NUM>, and the four-way valve <NUM> are annularly connected through refrigerant pipes. Mufflers <NUM> are mufflers for an air-conditioning apparatus, and are connected to a refrigerant pipe extending from a discharge port of the compressor <NUM> to the four-way valve <NUM>, and connected to a refrigerant pipe extending from the four-way valve <NUM> to the indoor heat exchanger <NUM>. During the heating operation, the indoor heat exchanger <NUM> positioned on a discharge port side of the compressor <NUM> functions as a condenser to perform the heating operation.

<FIG> is a refrigerant circuit diagram for illustrating the air-conditioning apparatus during a cooling operation according to Embodiment <NUM> of the present invention. In <FIG>, the four-way valve <NUM> is switched to the cooling operation (see the solid line of <FIG>). During the cooling operation, the compressor <NUM>, the four-way valve <NUM>, the outdoor heat exchanger <NUM>, the expansion valve <NUM>, the indoor heat exchanger <NUM>, and the four-way valve <NUM> are annularly connected through the refrigerant pipes. The Mufflers <NUM> are connected to the refrigerant pipe extending from the discharge port of the compressor <NUM> to the four-way valve <NUM>, and connected to the refrigerant pipe extending from the indoor heat exchanger <NUM> to the four-way valve <NUM>. During the cooling operation, the indoor heat exchanger <NUM> positioned on downstream of the expansion valve <NUM> functions as an evaporator to perform the cooling operation.

<FIG> is an external view for illustrating a part of the refrigerant circuit of <FIG>, which is surrounded by the dotted line. Illustration is made of the mufflers <NUM>, the compressor <NUM>, the four-way valve <NUM>, and the refrigerant pipes connecting those devices, which construct the air-conditioning apparatus.

<FIG> is a sectional view for illustrating the muffler <NUM> of <FIG>. As is apparent from the descriptions of <FIG>, the muffler <NUM> is mounted to the refrigerant circuit of the air-conditioning apparatus, at least to the refrigerant pipe connected to the discharge port side of the compressor <NUM>. The muffler <NUM> includes a muffler main body <NUM>, an inlet pipe <NUM>, and an outlet pipe <NUM>. The muffler main body <NUM> is constructed of a tubular body in which an inlet small diameter portion 8a is connected through an enlarged diameter portion 8b to a large diameter portion 8c, and the large diameter portion 8c is connected through a reduced diameter portion 8d to an outlet small diameter portion 8e. The inlet pipe <NUM> is connected to the inlet small diameter portion 8a of the muffler main body <NUM>. The outlet pipe <NUM> is connected to the outlet small diameter portion 8e of the muffler main body <NUM>.

The inlet pipe <NUM> is inserted through the inlet small diameter portion 8a of the muffler main body <NUM> into the muffler main body <NUM>, and has an inserted pipe portion <NUM> having a length L<NUM> from a starting point 8bs of the enlarged diameter portion 8b of the muffler main body <NUM>. A distal end of the inserted pipe portion <NUM> is positioned at a center of a length from an inlet to an outlet of the muffler main body <NUM>. The inserted pipe portion <NUM> has an upper inserted pipe portion <NUM> and a lower inserted pipe portion <NUM>. The upper inserted pipe portion <NUM> is a portion of a length L<NUM> from the starting point 8bs of the enlarged diameter portion 8b of the muffler main body <NUM>. The upper inserted pipe portion <NUM> has an inner diameter equal to that of an upstream portion of the inlet pipe <NUM> with respect to the inlet small diameter portion 8a of the main body <NUM>. The lower inserted pipe portion <NUM> is a portion of a length L<NUM>, which is continuous with the upper inserted pipe portion <NUM>. The inner diameter of the lower inserted pipe portion <NUM> is set smaller than that of the upper inserted pipe portion <NUM>. Thus, as the inlet pipe <NUM>, there is employed a refrigerant pipe reduced in diameter at a portion of the lower inserted pipe portion <NUM>.

In the muffler <NUM> having the configuration described above, a ratio of an inner diameter D of the muffler main body <NUM> to an inner diameter D<NUM> of the lower inserted pipe portion <NUM> is set to satisfy D/D<NUM>><NUM>.

A length of the inserted pipe portion <NUM> is represented by L<NUM>. A length of the upper inserted pipe portion <NUM> of the inserted pipe portion <NUM> is represented by L<NUM>. A length of the lower inserted pipe portion <NUM> of the inserted pipe portion <NUM> is represented by L<NUM>. The relationship among those lengths is set to satisfy <NUM><L<NUM>/L<NUM><<NUM>.

As in the related-art muffler according to Patent Literature <NUM>, there is a problem in that, when a diameter of the inserted pipe portion <NUM> is reduced from the inlet (corresponding to the starting point 8bs of this embodiment) of the muffler main body <NUM> (that is, L<NUM>=<NUM> in this embodiment), a pressure loss of the refrigerant in the refrigerant circuit may increase, with the result that a heat exchange efficiency of the air-conditioning apparatus may be lowered. However, according to the present invention, the ratio of the inner diameter D of the muffler main body <NUM> to the inner diameter D<NUM> of the lower inserted pipe portion <NUM> is set to satisfy D/D<NUM>><NUM>, and a ratio of the length of the lower inserted pipe portion <NUM> to the length of the upper inserted pipe portion <NUM> is set to satisfy <NUM><L<NUM>/L<NUM><<NUM>. Thus, compared to the muffler in which the diameter of the inserted pipe portion <NUM> is reduced from the inlet of the muffler main body <NUM> as in Patent Literature <NUM>, the pressure loss can be reduced by <NUM>% to a maximum. In this comparison, both of this embodiment and Patent Literature <NUM> have the same values in the length L of the muffler main body <NUM>, the inner diameter D of the muffler main body <NUM>, the length L<NUM> of the inserted pipe portion <NUM>, and the inner diameter D<NUM> of the inlet pipe <NUM>. For example, in a general compact muffler for an air-conditioning apparatus, the inner diameter D of the muffler main body <NUM> is <NUM> to <NUM>, the length L of the muffler main body <NUM> is <NUM> to <NUM>, and the length L<NUM> of the inserted pipe portion <NUM> is <NUM> to <NUM>. In the muffler having the dimensions within those ranges, when the ratio of the inner diameter D of the muffler main body <NUM> to the inner diameter D<NUM> of the lower inserted pipe portion <NUM> is a fixed value, the ratio of the length L<NUM> of the lower inserted pipe portion <NUM> to the length L<NUM> of the upper inserted pipe portion <NUM>, which can be manufactured, satisfies in accordance with the present invention <NUM><L<NUM>/L<NUM><<NUM>. Under such a
condition, when the pressure loss of the muffler in this embodiment is compared to that of the muffler having the inserted pipe portion <NUM> reduced in diameter from the inlet of the muffler main body <NUM>, it is verified that the pressure loss is reduced by <NUM>% to <NUM>%. In the general compact muffler for an air-conditioning apparatus, as the ratio of the inner diameter D of the muffler main body <NUM> to the inner diameter D<NUM> of the lower inserted pipe portion <NUM> increases within a range of <NUM><D/D<NUM>, a muffling effect is enhanced. However, in that case, the pressure loss increases. Meanwhile, when the ratio of the length L<NUM> of the lower inserted pipe portion <NUM> to the length L<NUM> of the upper inserted pipe portion <NUM> is set to satisfy L<NUM>/L<NUM>=<NUM>, the pressure loss can be reduced by <NUM>%. Therefore, even when the ratio D/D<NUM> of the inner diameter D of the muffler main body <NUM> to the inner diameter D<NUM> of the lower inserted pipe portion <NUM> is set to be as large as <NUM>, there can be obtained a muffler having the pressure loss equivalent to that of the muffler in which the diameter of the inserted pipe portion <NUM> is reduced from the inlet of the muffler main body <NUM> while D/D<NUM>=<NUM> is satisfied.

Further, regarding the muffling effect of the mufflers <NUM>, as the ratio of the inner diameter D of the muffler main body <NUM> to the inner diameter D<NUM> of the lower inserted pipe portion <NUM> increases, a muffling amount increases. Therefore, when the ratio is set to satisfy D/D<NUM>><NUM> as defined in the present invention, the muffling effect is enhanced. Here,
when a refrigerant pipe in which a distal end side of the inserted pipe portion <NUM> is not reduced in diameter is employed as in the another related-art muffler (that is, L<NUM>=<NUM> in this embodiment), it is verified that, in order to obtain the muffling effect as in this embodiment, the inner diameter of the muffler main body <NUM> needs to be set about <NUM> times larger than that of this embodiment. That is, in this embodiment, the muffling effect can be enhanced by reducing the inner diameter of the lower inserted pipe portion <NUM> without increasing the size of the muffler main body <NUM>. Therefore, when the muffler <NUM> of this embodiment is employed, the muffler for an air-conditioning apparatus having an enhanced muffling effect can be introduced into an existing air-conditioning apparatus without newly designing a configuration of refrigerant circuit pipes of the air-conditioning apparatus.

Next, description is made of calculation results of the muffling effect of the muffler for an air-conditioning apparatus, which are calculated with the following conditions using an acoustic impedance.

<FIG> are graphs for showing muffling properties of the mufflers for an air-conditioning apparatus of the above-mentioned conditions (<NUM>) to (<NUM>). The calculation results of the muffling property are determined with certain conditions of the length L of the muffler main body <NUM>, the length L<NUM> of the inserted pipe portion <NUM>, the length L<NUM> of the upper inserted pipe portion <NUM>, the inner diameter D<NUM> of the upper inserted pipe portion <NUM>, and the length L<NUM> of the lower inserted pipe portion <NUM>. Specifically, the mufflers for an air-conditioning apparatus of the conditions (<NUM>) to (<NUM>) satisfy the length L of the muffler <NUM>=<NUM>, the length L<NUM> of the inserted pipe portion <NUM>=<NUM>, and the inner diameter D<NUM> of the upper inserted pipe portion <NUM>=<NUM>. The muffler for an air-conditioning apparatus of the condition (<NUM>) satisfies the length L<NUM> of the upper inserted pipe portion=<NUM>, and the length L<NUM> of the lower inserted pipe portion=<NUM>.

<FIG> is a graph for showing the muffling property of the muffler for an air-conditioning apparatus according to an example not covered by the present invention, of the above-mentioned condition (<NUM>). In the muffler for an air-conditioning apparatus of the above-mentioned condition (<NUM>), the inner diameter D<NUM> of the upper inserted pipe portion <NUM> and the inner diameter D<NUM> of the lower
inserted pipe portion <NUM> are equal.

<FIG> is a graph for showing the muffling property of the muffler for an air-conditioning apparatus of the above-mentioned condition (<NUM>). The muffler for an air-conditioning apparatus of the above-mentioned condition (<NUM>) satisfies D/D<NUM>=<NUM> by reducing the inner diameter D<NUM> of the lower inserted pipe portion <NUM> as compared to the muffler for an air-conditioning apparatus of the above-mentioned condition (<NUM>). When the calculation results of the muffling property in the cases of the above-mentioned condition (<NUM>) and the above-mentioned condition (<NUM>) are compared, it is found that the muffling amount increases without fluctuation of a frequency having the muffling effect. In addition, it is also found that the muffling effect is improved by about 8dB to a maximum (see <FIG>). That is, when D/D<NUM>><NUM> is satisfied as in the muffler for an air-conditioning apparatus of the above-mentioned condition (<NUM>), sufficient muffling effect can be obtained as compared to the case of the above-mentioned condition (<NUM>).

<FIG> is a graph for showing the muffling property of the muffler for an air-conditioning apparatus of the above-mentioned condition (<NUM>). The muffler for an air-conditioning apparatus of the above-mentioned condition (<NUM>) is set to satisfy D/D<NUM>=<NUM> by increasing the inner diameter D of the muffler main body <NUM> without changing the inner diameter D<NUM> of the lower inserted pipe portion <NUM>. When the calculation result of the muffling property in the case of the above-mentioned condition (<NUM>) is compared to the calculation result of the muffling property in the case of the above-mentioned condition (<NUM>), the muffling effects are substantially the same. That is, the muffling effect can be enhanced by reducing the inner diameter D<NUM> of the lower inserted pipe portion <NUM> without increasing the diameter of the muffler main body <NUM>.

<FIG> is a graph for showing the measurement results, with the mufflers for an air-conditioning apparatus of the above-mentioned conditions (<NUM>) and (<NUM>) each arranged on the discharge side of the compressor <NUM> in order to verify the efficacy of the muffling effect described above. A pulsation noise generated in the indoor heat exchanger due to a pressure pulsation is measured. When a comparison is made between a measurement result of the muffler for an air-conditioning apparatus as a reference and a measurement result of the muffler for an air-conditioning apparatus in which the inner diameter D<NUM> of the lower inserted pipe portion <NUM> is reduced, it is found that the pulsation noise is reduced. From this point of view, it is found that the high muffling effect can be obtained when an inner diameter ratio is set, as defined in the present invention, to satisfy
D/D<NUM>><NUM>.

Claim 1:
A muffler for an air-conditioning apparatus (<NUM>), comprising:
a muffler main body (<NUM>), having a tubular shape, in which an inlet small diameter portion (8a) is connected to a large diameter portion (8c) through an enlarged diameter portion (8b), and the large diameter portion (8c) is connected to an outlet small diameter portion (8e) through a reduced diameter portion (8d);
an inlet pipe (<NUM>) connected to the inlet small diameter portion (8a) of the muffler main body (<NUM>); and
an outlet pipe (<NUM>) connected to the outlet small diameter portion (8e) of the muffler main body (<NUM>),
the inlet pipe (<NUM>) having an inserted pipe portion (<NUM>) disposed in the muffler main body (<NUM>), the inserted pipe portion (<NUM>) being inserted into the muffler main body from the inlet small diameter portion (8a) and extending from a starting point (8bs) of the enlarged diameter portion (8b) to an inside of the muffler main body (<NUM>),
the inserted pipe portion (<NUM>) having an upper inserted pipe portion (<NUM>) positioned on an inlet side of the muffler main body (<NUM>) and a lower inserted pipe portion (<NUM>) positioned on an outlet side of the muffler main body (<NUM>),
wherein the upper inserted pipe portion (<NUM>) has an inner diameter equal to an inner diameter of the inlet pipe (<NUM>) on an upstream part of the inlet small diameter portion (8a), and
wherein the lower inserted pipe portion (<NUM>) has a distal end positioned at a center of a length from an inlet to an outlet of the muffler main body (<NUM>),
characterized in that
the lower inserted pipe portion (<NUM>) has an inner diameter smaller than an inner diameter of the upper inserted pipe portion (<NUM>),
wherein a ratio of an inner diameter D of the muffler main body (<NUM>) to an inner diameter D<NUM> of the lower inserted pipe portion (<NUM>) is set to satisfy D/D<NUM>><NUM>, and
wherein, when a length of the upper inserted pipe portion (<NUM>) is defined as L<NUM>, and a length of the lower inserted pipe portion (<NUM>) is defined as L<NUM>, a ratio of L<NUM> to L<NUM> is set to satisfy <NUM><L<NUM>/L<NUM><<NUM>.