JP2008151018A - Rotary type two-stage compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary type two-stage compressor capable of securing reliability of a vane tip end slide part without using a means such as expensive coating on a vane even when it is used in a cold region where high differential pressure and high speed rotation are required. <P>SOLUTION: The rotary type two-stage compressor includes an electric element, and a low-stage compression element and high-stage compression element driven by the electric element through a rotation shaft in a tightly closed container, and the tightly closed container is held at an intermediate pressure. The rotary type two-stage compressor is provided with a high stage vane provided on the high-stage compression element, to which a discharge pressure is applied on a back surface, of which at least a tip end part is subjected to nitriding treatment, and which slides in a diameter direction. The rotary type two-stage compressor is mounted on a heat pump type water heater, and operates so that a differential pressure between a high pressure and the intermediate pressure of the high-stage compression element × the number of rotations (MPa rps) becomes not more than 630 when it operates in the cold region of which an external temperature is not higher than -10°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotary two-stage compressor in which an electric element and a compression element driven by the electric element are provided in an airtight container.

  In recent years, the destruction of the global environment due to refrigerants has been regarded as a problem. Etc.) and other natural refrigerants are beginning to be used.

In compressors applied to refrigerant circuit devices such as heat-pump water heaters using alternative chlorofluorocarbons or natural refrigerants, especially compressors for CO2 refrigerant, an internal intermediate pressure two-stage compressor is applied because the operating pressure increases. There are some (see, for example, Patent Document 1).
JP 2003-89472 A

  However, in the internal intermediate pressure two-stage compressor as in Patent Document 1, the wear resistance at the vane tip of the compression element can be secured in a wide range by adopting the two-stage compression method. Has a problem that it becomes difficult to ensure the vane tip wear resistance of the compression element on the high stage side because the differential pressure on the high stage side of the compressor becomes large due to the high compression ratio operation.

  The present invention has been made to solve the above-described problems, and even in cold districts where high differential pressure and high speed rotation are used, the vane tip slides without using an expensive coating means or the like on the vane. An object of the present invention is to provide a rotary two-stage compressor capable of ensuring the reliability of the part.

  A rotary two-stage compressor according to the present invention includes an electric element in a sealed container, and a low-stage compression element and a high-stage compression element that are driven by the electric element via a rotating shaft. In the rotary type two-stage compressor in which the intermediate pressure becomes an intermediate pressure, a high-stage vane that is provided in a high-stage compression element, discharge pressure acts on the back surface, and at least the tip is subjected to nitriding treatment, slides in the radial direction. When the rotary two-stage compressor is installed in a heat pump water heater and is operated in a cold area where the outside air temperature is -10 ° C or lower, the differential pressure between the high pressure and the intermediate pressure of the high-stage compression element × rotation The operation is performed such that the number (MPa · rps) is 630 or less.

  The rotary type two-stage compressor according to the present invention is mounted on a heat pump type hot water heater and is operated in a cold region where the outside air temperature is -10 ° C. or lower, and the difference between the high pressure and the intermediate pressure of the high stage compression element. By operating so that the pressure x rotational speed (MPa · rps) is 630 or less, the reliability of the vane tip sliding portion can be secured without using expensive means such as coating on the vane.

Embodiment 1 FIG.
1 to 11 are diagrams showing Embodiment 1, FIG. 1 is an internal front view of a hot water supply unit 100 of a heat pump type hot water heater, and FIG. 2 is a view showing a refrigerant circuit 1 and a water circuit 8 of the heat pump type hot water heater. 3 is a longitudinal sectional view of the compressor 2, FIG. 4 is a diagram showing the relationship between the outside air temperature and the operating pressure of the heat pump water heater, and FIG. 5 is the relationship between the outside temperature of the heat pump water heater and the high step pressure and low step pressure. Fig. 6 is a diagram showing the relationship between the outside temperature of the heat pump type water heater and the rotation speed ratio, Fig. 7 is a diagram showing the relationship between the outside temperature of the heat pump type water heater and (high step pressure x number of revolutions), and Fig. 8 is a high stage. FIG. 9 is a diagram showing the configuration of the compression element 12b, FIG. 9 is a diagram showing the tip wear rate of the high stage vane 19b when a nitride vane is used for the high stage compression element 12b, and FIG. Fig. 11 is a diagram of the relationship between compressor displacement and hot water heating capacity. .

  The present embodiment relates to a rotary two-stage compressor 10 of a heat pump type hot water heater, but first, the heat pump type hot water heater will be briefly described.

  FIG. 1 shows an embodiment of a hot water supply unit 100 of a heat pump type hot water heater. The gas cooler 3 (hot water heat exchanger) is installed below the intermediate base 28 in the lower part of the hot water supply unit 100 of the heat pump type hot water heater.

  An air heat exchange chamber 24 having an evaporator 5 (air heat exchanger) and a blower 7 (propeller fan), a compressor 2 of a refrigerant circuit, and a heat pump type provided at a side of the air heat exchange chamber 24 A machine room 27 having an electrical appliance 26 and the like for controlling the operation of the hot water supply unit 100 of the water heater is installed on the intermediate base 28.

In the refrigerant circuit 1 shown in FIG. 2, a CO ₂ refrigerant having a low critical temperature is used as the refrigerant. The compressor 2 is driven by an electric motor (not shown) such as a built-in synchronous motor or induction motor, and compresses and discharges the suction refrigerant to a critical pressure or higher under general use conditions. The gas cooler 3 exchanges heat between the high-pressure gas refrigerant discharged from the compressor 2 and the hot water supply water in the water circuit 8.

  The high-pressure and low-temperature refrigerant that has exited the gas cooler 3 passes through the expansion valve 4 and flows into the evaporator 5. The low-pressure refrigerant that has flowed out of the evaporator 5 returns to the compressor 2.

  In the water circuit 8, a water circulation pump 9 is connected to a hot water storage tank (not shown), passes through the gas cooler 3 (water pipe side) from the bottom of the hot water storage tank, and then supplies water toward the top of the hot water storage tank. Circulate.

  The compressor 2 is a rotary two-stage compressor. The configuration will be described with reference to FIG. An electric element 11 and a compression element 12 driven by the electric element 11 via a rotating shaft 18 are provided in the sealed container 10a. The electric element 11 is located in the upper part in the sealed container 10a, and the compression element 12 is located in the lower part in the sealed container 10a.

  The compression element 12 includes a low-stage compression element 12a and a high-stage compression element 12b, and the low-stage compression element 12a and the high-stage compression element 12b are partitioned by an intermediate partition plate 17.

  The low-stage compression element 12a includes a low-stage cylinder 13a, a low-stage bearing 14a, a low-stage suction pipe 15a that communicates with a compression chamber of the low-stage cylinder 13a, and the like.

  In the low-stage compression element 12a, a low-pressure refrigerant gas is sucked into a low-stage cylinder 13a from a low-stage intake pipe 15a connected to a low-pressure side of a refrigeration cycle (not shown), and a rotary compression mechanism section (since it is a known one). Compressed and discharged into the sealed container 10a. Therefore, the inside of the sealed container 10a becomes an intermediate pressure.

  The intermediate-pressure sealed container 1a exits the sealed container 10a from the low-stage discharge pipe 16a, and enters the high-stage suction pipe 15b through an intermediate pressure connection pipe (not shown). In the high-stage compression element 12b, the intermediate-pressure refrigerant gas is compressed to a high pressure by the same rotary compression mechanism as the low-stage compression element 12a, and exits from the high-stage discharge pipe 16b to the high-pressure side of the refrigeration cycle (not shown).

  FIG. 4 is a relationship diagram between the outside air temperature and the operating pressure of the heat pump type hot water heater. The intermediate pressure in FIG. 4 is when the stroke volume ratio between the high-stage compression element 12b and the low-stage compression element 12a is 0.65. As shown in FIG. 4, it can be seen that when the outside air temperature decreases, the differential pressure between the high pressure and the intermediate pressure in the high-stage compression element 12b tends to increase. Since the discharge pressure (intermediate pressure) of the low-stage compression element 12a is determined by the stroke volume ratio (stroke volume ratio) between the high-stage compression element 12b and the low-stage compression element 12a, the high-stage compression element increases as the compression ratio increases. The compression ratio of 12b is unilaterally expanded.

  As shown in FIG. 5, in a cold district application where the outside air temperature is −10 ° C. or lower, the differential pressure between the high pressure and the intermediate pressure of the high-stage compression element 12 b increases, and may exceed 6 MPa, for example.

  In the heat pump type water heater, when the outside air temperature is lowered to ensure the hot water supply capacity, the rotational speed of the compressor 2 tends to increase. FIG. 5 shows the rotation speed ratio when the outside air temperature changes with the rotation speed when the outside air temperature is 20 ° C. as a reference. In cold district applications where the outside air temperature is −10 ° C. or lower, the rotational speed ratio becomes large. For example, at −10 ° C., the rotational speed ratio exceeds 1.5.

In general, the severity of sliding of machine parts is represented by a PV value. here,
P: Surface pressure (represented by the differential pressure between high pressure and low pressure in terms of compression elements)
V: sliding speed (increased as the number of rotations of the compressor 2 increases)
In addition, temperature has an effect. In a cold district application of −10 ° C. or lower, the discharge temperature becomes high, and the conditions become more severe.

  In the high-stage compression element 12b, the PV value representing the severity of sliding of mechanical parts is represented by high step pressure (difference between high pressure and intermediate pressure) × rotational speed. FIG. 7 is a relationship diagram of the high step pressure of the high-stage compression element 12b × the number of revolutions and the outside air temperature, and shows that the outside air temperature increases as the outside air temperature decreases. In particular, in a cold district application at -10 ° C. or lower, it increases rapidly.

  FIG. 8 is a configuration diagram of the high-stage compression element 12b. The high-stage cylinder 13b is provided with a high-stage rolling piston 20b fitted to the eccentric portion of the rotary shaft 18 and a high-stage vane 19b that is slid radially in the discharge pressure acting on the back surface. Forming a chamber. Among the sliding portions of the high-stage compression element 12b, the most severe sliding condition is the discharge pressure of the back pressure of the high-stage vane 19b. Therefore, the tip of the high-stage vane 19b and the high-stage rolling piston 20b It is a contact part.

  The high stage vane 19b was subjected to nitriding treatment, and the relationship between the differential pressure (difference between high pressure and intermediate pressure) × rotational speed (MPa · rps) and the high stage vane 19b tip wear rate was examined. Here, the nitriding treatment is a chemical surface hardening method of surface hardening heat treatment, in which nitrogen is diffused and penetrated from the steel surface to harden the steel surface. By this nitriding treatment, the hardness of the surface of the high stage vane 19b is set to 1000 to 1600 in terms of micro Vickers hardness, so that the wear resistance is improved as compared with the non-nitriding treatment. At this time, the nitride layer on the surface of the high stage vane 19b is 0.02 to 0.10 mm.

  FIG. 9 shows the result of nitriding the high stage vane 19b and examining the relationship between differential pressure (difference between high pressure and intermediate pressure) × rotational speed (MPa · rps) and tip wear rate of the high stage vane 19b. As shown in FIG. 9, the wear rate of the tip of the high stage vane 19b does not change greatly until the differential pressure × the number of rotations is around 630, but it is understood that the wear rate increases rapidly when the pressure exceeds about 630. Note that nitriding treatment may be performed on the high stage vane 19b at least at the tip of the high stage vane 19b.

  One method of setting the differential pressure × the number of revolutions (MPa · rps) to 630 or less is to set the number of revolutions of the compressor 2 to 100 rps or less under conditions where the outside air temperature is −10 ° C. or less. This is because, as shown in FIG. 10, the wear at the tip of the high stage vane 19b increases abruptly when the rotational speed is around 100 rps.

FIG. 11 shows the result of calculating the relationship between the displacement (cm ³ ) of the compressor 2 at a rotational speed of 100 rps and the hot water supply heating capacity (KW). Conditions are calculated with an outside air temperature of −20 ° C. and a volume efficiency of 85%. From FIG. 11, when the displacement is V and the heating capacity is Q,
Displacement amount V ≒ Heating capacity Q x 0.87 (1)
It is understood that there is a relationship.

If the rotation speed of the compressor 2 is set to 100 rps or less under the condition that the outside air temperature is −10 ° C. or less, the wear of the tip of the high stage vane 19b can be suppressed, but the capacity of the heat pump type hot water heater is reduced. Increase the displacement V of. Since the displacement amount V and the heating capacity Q have the relationship of the formula (1),
Displacement amount V> Heating capacity Q × 0.87 (2)
Set to be. Thereby, even if it sets the rotation speed of the compressor 2 to 100 rps or less, the heating capability Q in the cold district conditions whose external temperature of a heat pump type hot water heater is -10 degrees C or less is securable.

  Since a heat pump type hot water heater performs boiling using electric power, it is normally heated using late-night power during midnight hours (23: 00 to 7:00). However, when the outside air temperature is -10 ° C or less, if the differential pressure between the high pressure and the intermediate pressure of the high-stage compression element and the rotation speed (MPa rps) are operated at 630 or less, it is heated up in this midnight time zone. May be insufficient. This shortage needs to be compensated by driving outside midnight. Also, since the outside air temperature is extremely low from about 40:00 to 6:00 from early morning to dawn, it is necessary to compensate for the avoided time zone if operation is avoided in that time zone. Therefore, in cold district conditions where the outside air temperature is −10 ° C. or less, the operation ratio other than the late-night time zone (23: 0 to 7:00) is set to 20% or more. As a result, even if the outside temperature is −10 ° C. or less and the cold region is operated at a differential pressure between the high pressure of the high-stage compression element and the intermediate pressure × rotational speed (MPa · rps) at 630 or less, it can be heated up. it can.

  As described above, nitriding treatment is performed on the high stage vane 19b, and the operation is performed so that the differential pressure (difference between the high pressure and the intermediate pressure) × the rotation speed (MPa · rps) is within 630. Even in a cold region where the temperature is 10 ° C. or lower, wear at the tip of the high-stage vane 19b can be suppressed without using expensive means such as coating. The coating is, for example, a metal compound formed by physical vapor deposition, chemical vapor deposition, or plasma chemical vapor deposition, or amorphous carbon.

Fig. 5 shows the first embodiment, and is an internal front view of a hot water supply unit 100 of a heat pump type hot water heater. FIG. 3 shows the first embodiment and shows the refrigerant circuit 1 and the water circuit 8 of the heat pump type hot water heater. FIG. 3 shows the first embodiment and is a longitudinal sectional view of the compressor 2. It is a figure which shows Embodiment 1, and is a related figure of the external temperature and operating pressure of a heat pump type water heater. It is a figure which shows Embodiment 1, and is a related figure of the external temperature of a heat pump type water heater, high step pressure, and low step pressure. It is a figure which shows Embodiment 1, and is a related figure of the external temperature of a heat pump type water heater, and rotation speed ratio. It is a figure which shows Embodiment 1, and is a related figure of the external temperature of a heat pump type water heater and (high step pressure x rotation speed). FIG. 5 shows the first embodiment and is a configuration diagram of a high-stage compression element 12b. The figure which shows Embodiment 1, The figure is a longitudinal cross-sectional view of the internal pressure two-stage compressor 1 showing the high-stage vane 19b tip wear rate when a nitride vane is used for the high-stage compression element 12b. FIG. 5 shows the first embodiment, and is a diagram showing the relationship between the high stage vane 19b tip wear speed and the rotational speed. Fig. 5 shows the first embodiment, and is a diagram showing the relationship between the amount of displacement of the compressor and the hot water supply heating capacity.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Refrigerant circuit, 2 Compressor, 3 Gas cooler, 4a 1st expansion valve, 4b 2nd expansion valve, 5 Evaporator, 6 Internal heat exchanger, 7 Blower, 8 Water circuit, 9 Pump, 10a Airtight container, 11 Electric element, 12 compression element, 12a Low stage compression element, 12b High stage compression element, 13a Low stage cylinder, 13b High stage cylinder, 14a Low stage bearing, 14b High stage bearing, 15a Low stage suction pipe, 15b High stage suction pipe , 16a Low stage discharge pipe, 16b High stage discharge pipe, 17 Intermediate partition plate, 18 Rotating shaft, 24 Air heat exchange chamber, 26 Electrical equipment, 27 Machine room, 28 Intermediate base, 100 Hot water supply unit of heat pump type hot water heater.

Claims (4)

A rotary two-stage compressor having an electric element in a hermetic container and a low-stage compression element and a high-stage compression element driven by the electric element via a rotating shaft, wherein the inside of the hermetic container has an intermediate pressure In
A high-stage vane that is provided in the high-stage compression element, has a discharge pressure acting on the back surface, and is subjected to nitriding treatment at least at the tip, and slides in the radial direction,
When the rotary type two-stage compressor is mounted on a heat pump type water heater and is operated in a cold region where the outside air temperature is -10 ° C. or lower, the differential pressure between the high pressure and the intermediate pressure of the high-stage compression element × rotation A rotary two-stage compressor that is operated so that the number (MPa · rps) is 630 or less.   2. The rotary two-stage compressor according to claim 1, wherein the rotary air compressor is operated at a rotation speed of 100 rps or less under a condition where the outside air temperature is −10 ° C. or less. The total displacement V (cm ³ ) of the low-stage compression element and the high-stage compression element is relative to the heating capacity Q (KW) in a cold district condition where the outside temperature of the heat pump water heater is −10 ° C. or less. ,
Displacement amount V> Heating capacity Q × 0.87
The rotary two-stage compressor according to claim 1, wherein the rotary type two-stage compressor is set to be   The operating ratio other than the midnight time zone (23: 0 to 7:00) is set to 20% or more in the cold region condition where the outside air temperature is -10 ° C or less. Rotary type two-stage compressor.

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