JPH0575915B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to rotary compressors used in refrigerators and air conditioners, and particularly relates to inertial supercharging suitable for improving the performance of compressors in high-speed operating ranges. [Prior art] Conventional devices of this type are disclosed in Japanese Utility Model Application No. 57-40679, Japanese Utility Model Application No. 57-40680, Japanese Utility Model Application No. 57-40681, and Japanese Utility Model Application Publication No. 57-40681.
As described in Publication No. 57-40682, in order to change the length of the suction pipe, a U-shaped suction pipe is slidably fitted to both the suction pipe of the compressor and the pipe on the outlet side of the evaporator. A method of increasing the length of the suction pipe and connecting an intermediate chamber by providing an intermediate port opening in the middle of the suction chamber, a method of installing a delay element approximately equal to the frequency of the pulsating flow on the suction side etc. [Problems to be Solved by the Invention] However, in the methods disclosed in these publications, it is necessary to provide an additional device in order to generate pulsating flow. In the first example mentioned above, in order to make the U-shaped suction pipe slidable, a motor is required to drive it, and a seal is also required to prevent gas leakage, and the suction pipe etc. Machining precision is required. Second
In this example, if the operating conditions of the compressor deviate from the resonant frequency, the compressor acts as a dead volume, which actually reduces the efficiency of the compressor. In the third example, since a spring/mass system is used as the delay element, the resonant frequency band is narrow. Furthermore, these designs have long suction pipes, and focus on improving the volumetric efficiency on the low speed side of the compressor, with no particular consideration given to the high speed side. When the rotation speed of the compressor is controlled using an inverter, the volumetric efficiency decreases in the high-speed operating range due to pressure loss on the suction side, etc., as shown in FIG. Therefore, in order to obtain the necessary amount of refrigerant circulation, it is necessary to increase the theoretical capacity of the compressor or to increase the speed of the compressor. If the theoretical capacity is increased, the low speed side will be operated at a lower speed, leading to the problem of lower volumetric efficiency mainly due to leakage. or,
Increasing the speed of the compressor shortens the life of the bearings, which poses a problem in terms of reliability. Conventional technology has not taken these points into consideration, and the problem has been to operate the compressor at higher speeds. An object of the present invention is to improve volumetric efficiency in a high-speed operating range of a compressor in order to solve the above problems. [Means for solving the problem] A feature of the present invention for achieving the above object is a supercharging system comprising a compression mechanism, a buffer space container provided on the suction side of the compression mechanism, and a suction pipe. In a type compressor, the length of the suction pipe is determined so that the air column frequency of the first mode in the suction pipe is in sync with the maximum rotational speed of the compressor, and the suction pipe length is determined so that the air column frequency of the first mode in the suction pipe is in sync with the maximum rotation speed of the compressor, and the suction pipe is set so that the compressor's filling efficiency exceeds 1. Pipe flow resistance coefficient μ and inertial supercharging characteristic number
The cross-sectional area of the suction pipe was determined to satisfy Z ₀ . [Operation] The length of the suction pipe is determined so that the first mode air column frequency and the maximum rotational speed of the compressor are in sync, and the cross-sectional area of the suction pipe is determined so that the filling efficiency of the compressor exceeds 1. Since this is specified, the volumetric efficiency of the compressor can be improved. [Example] As shown in Fig. 1, the suction side of the rotary compressor includes an accumulator 10 for preventing liquid refrigerant from being sucked into the compressor, and an inlet connecting the accumulator outlet to the compressor suction port. pipe 12,
It consists of a compression mechanism section 3 and the like. Also, casing 1
Inside, a motor section 2, a cylinder 5, an upper bearing 6, a lower bearing 7, a roller 8, and a discharge port 9 are arranged as shown in the figure. When the compressor 13 is driven by the inverter drive device 14 shown in FIG. 9 and the shaft rotates, the volume of the suction chamber during the suction stroke changes as shown in FIG. 3. When entering the suction stroke, the pressure in the suction chamber decreases, so the refrigerant gas in the suction pipe begins to accelerate toward the compression mechanism. When gas flows, friction occurs on the inner surface of the pipe.
The accelerated refrigerant gas is given an inertial force, and the gas once sucked into the compression mechanism acts like a gas spring. Expressing this in the formula, d ² x/dt ² + r(dx/dt) ² = 1/ρ ₀ L _S (ρ ₀ −ρ(θ
)) becomes. Here, x: moving distance of the air column inside the suction pipe, r: resistance coefficient including pipe friction, restriction of the suction pipe, etc., _Lv : effective length of the suction pipe, and _ρ0 : gas density. When this is made dimensionless, d ₂ q/dθ ² +2μ(dq/dθ)+1/Z ₀ ² {q/(V(θ)
/V _h −1} =0. or,

It is [ ]. Here, A _S is the cross-sectional area of the pipe, V _h is the stroke volume, q = A _S · x / V _h , θ is the rotation angle of the shaft, ω is the rotation angular velocity of the shaft, and V (θ) is the rotation angle θ. The cylinder volume on the suction side at , a ₀ is the speed of sound. The inertial supercharging effect is a phenomenon in which the accelerated gas at the end of the suction stroke overcomes the gas spring action and frictional force due to inertial force and is pushed in extra, resulting in an improvement in the filling efficiency of the compressor. However, in order to maximize its effect, the value of q shown in the above equation, which is on the verge of confinement at the end of the suction stroke, must be large. The inertial supercharging characteristic number Z ₀ means the ratio of the rotational angular velocity of the shaft and the natural frequency when the gas spring and air column are considered as concentrated masses. The difference between a rotary compressor and a reciprocating compressor is that the suction stroke is completed in one revolution of 360 degrees, compared to a reciprocating compressor that completes the suction stroke with a shaft rotation angle of 180 degrees. Therefore, from the result of linearizing the third term in the above equation, for a reciprocating compressor, the optimum inertia supercharging characteristic number Z ₀ , which has a phase delay of 90° with respect to the excitation force, is around 0.5, and for a rotary compressor Then, when the flow resistance coefficient μ is small, it can be estimated that Z ₀ , which has a phase delay of 180° with respect to the excitation force, is optimally a value slightly larger than 1. The above equation is a nonlinear equation, and strictly speaking, it is necessary to solve it. The calculation results are shown in Figure 4. As the flow resistance coefficient μ increases, the inertial force itself decreases, so the effect of inertial supercharging disappears. Therefore, the flow resistance coefficient must be made as small as possible, and the effect can be expected when the filling efficiency q exceeds 1 and μ is less than 0.5. For example μ
= 0.5, the charging efficiency q does not exceed 1 by increasing the inertial supercharging characteristic number Z ₀ . Further, the range of the inertial supercharging characteristic number Z ₀ in which the inertial supercharging effect occurs may be approximately 0.6 or more. However, this alone is not sufficient to obtain the inertial supercharging effect, and as can be seen from the experimental results shown in Figure 5, the volumetric efficiency η _v peaks when the inertial supercharging characteristic number Z ₀ . There are conditions to indicate. In other words, in order to obtain a sufficient inertial supercharging effect, it is necessary to increase the pressure fluctuations in the pipe that occur due to periodic fluctuations in the suction stroke, and to use this together with the pulsation effect to increase the confining pressure at the end of the suction stroke. There is. The m-th natural frequency f _n of the intake pipe system is calculated as f _n = 2 m−, where the equivalent pipe length considering the stroke volume is L _v (L _v = L _S + V _h /A _S ) and the sound speed is a ₀ . 1/4L _v a ₀ . Letting the operating frequency of the compressor be n, its ratio is defined as the frequency ratio k, and when the experimental data in Figure 5 is organized with respect to the frequency ratio for the first mode of m = 1, it is as shown in Figure 6. It can be seen that this is effective when the frequency ratio is near 1. In this way, in order to obtain the inertial supercharging effect, (1) the flow resistance coefficient μ should be less than 0.5, (2) the inertial supercharging characteristic number Z ₀ should be 0.6 or more, and (3) the resonant frequency of the pipe system. It is necessary to keep the ratio of the primary mode of the compressor to the operating frequency of the compressor close to 1. Embodiments of the present invention will be described below with reference to FIGS. 7 and 8. The present invention can be applied to a rolling piston type rotary compressor, and has a stroke volume of 3
It is usually applied to small compressors of about cm ³ /rev to medium-sized compressors of about 50 cm ³ /rev used in air conditioners. Also, gas is normally used as refrigerant R in refrigerators.
-12 is used, and refrigerant R-22 is used in air conditioners. The simplest configuration for carrying out the present invention is a configuration in which a suction pipe having dimensions that satisfy the three conditions described in the [Operation] section is attached. Compressor rotational speed N _U and stroke volume aiming for inertial supercharging effect
Once V _h is determined and the cycle components are determined, the pressure conditions are determined, so the sound speed a is determined. The equivalent pipe length L _v must be L _v ~a/4n so that the ratio of the first-order mode resonance frequency and the rotational frequency of the compressor is approximately 1, and the flow resistance coefficient μ must be 0.5 or less. Must be. μ=r・(dq/dθ)・V _h /2A _S , (dq/dθ)〜1/2π, r=λ/L _v +ν√π/2・1
/√A _S , so if the suction pipe cross-sectional area A _S is the resistance coefficient at the entrance and exit of the pipe, λ, and the pipe friction coefficient is ν, then 0.5>V _h /4π[λ/A _S +ν√πL _S /2A _S ^3/2 ]. The larger the cross-sectional area A _S is, the _smaller the flow resistance coefficient μ becomes.
To make it larger than 0.6, A _S

[Formula] The value shall be less than or equal to the following. The structure of a compressor equipped with a suction pipe having such dimensions is shown in FIG. 7, and the volumetric efficiency is shown in FIG. 8. As shown by curve A, the volumetric efficiency exhibits a high value exceeding 100% at the set rotational speed N _U where the inertial supercharging effect is activated. The volumetric efficiency of a compressor equipped with a suction pipe that does not have a conventional inertial supercharging function is curve B.
As shown in , the rotation speed of the compressor decreases as the rotation speed increases due to pressure loss in the suction passage. The inertial supercharging effect peaks at the set rotational speed N _U , and the effect spreads to the high and low speed sides, so the volume is considerably reduced compared to when inertial supercharging is not performed over a wide range of rotational speeds. Can improve efficiency. Furthermore, the flow resistance coefficient μ must be less than 0.5, and the inertial supercharging characteristic number Z ₀ must be 0.6 or more. μ=r(dq/dθ)・V _h /2A _S ,

〔Effect of the invention〕

As described above, according to the present invention, the volumetric efficiency of the compressor, particularly in the high-speed operation range, can be significantly improved. As a side effect, the maximum rotational speed of the compressor can be significantly lower than when inertial supercharging is not applied, which not only improves the reliability of the compressor, but also improves the reliability of the compressor.
Since it operates in a region with better total adiabatic efficiency, compressor input can be reduced.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view of the compressor, Figure 2 is a diagram showing changes in efficiency with respect to rotational speed of the compressor, and Figure 3 is a diagram showing changes in efficiency with respect to rotational speed of the compressor.
FIG. 4 is a diagram showing the relationship between the inertial supercharging characteristic number and filling efficiency, FIG. 5 is a diagram showing the relationship between the inertial supercharging characteristic number and volumetric efficiency,
FIG. 6 is a diagram showing the relationship between frequency ratio and volumetric efficiency, FIG. 7 is a sectional view of a main part of an embodiment of the present invention,
FIG. 8 is a diagram showing the relationship between rotational speed and volumetric efficiency, and FIG. 9 is a diagram showing the structure of the cycle. DESCRIPTION OF SYMBOLS 1...Casing, 2...Electric part, 3...Compression mechanism part, 4...Cylinder, 5...Shaft, 6...
...Upper bearing, 7...Lower bearing, 8...Roller, 9
...Discharge chamber, 10...Accumulator, 11...
Discharge pipe, 12... Suction pipe, 13... Rotary compressor, 14... Inverter drive device, 15
...Condenser, 16...Expansion valve, 17...Evaporator.

Claims (1)

[Scope of Claims] 1. A supercharging compressor comprising a compression mechanism, a buffer space container provided on the suction side of the compression mechanism, and a suction pipe, in which a primary mode air column in the suction pipe is provided. The length of the suction pipe is determined so that the vibration frequency and the preset maximum rotation speed are synchronized, and the filling efficiency satisfies the flow resistance coefficient μ and inertial supercharging characteristic number Z ₀ of the suction pipe in a range exceeding 1. The cross-sectional area of the suction pipe is as follows:
A supercharging compressor characterized by having A _S. 2 In claim 1, the flow resistance coefficient μ is 0.5 or less, and the inertial supercharging characteristic number Z ₀ is 0.6.
A supercharging compressor characterized by the above.