KR101993791B1 - Counterweight of balanced-opposed type multi throw reciprocating compressor - Google Patents

Abstract

Disclosed is a crank shaft of an opposite type multi-cylinder reciprocating compressor. According to the present invention, the crank shaft of an opposite type multi-cylinder reciprocating compressor comprises: N-crank pins forming a phase difference of 360/N degrees; a plurality of webs connecting the crank pins to a main journal; and a pair of balance weights spaced from the crank pins, coupled to both end portions of the main journal, and having a phase difference of 180 degrees from each other. Accordingly, unbalance moments on the opposite type reciprocating compressor can be reduced. Moreover, the number and size of the balance weights can be reduced.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a crankshaft of an opposite multi-cylinder reciprocating compressor,

The present invention relates to a crankshaft of an opposed multi-cylinder reciprocating compressor, and more particularly to an opposed multi-cylinder reciprocating compressor which is configured to reduce the unbalance moment on the reciprocating reciprocating compressor, To a crankshaft.

Large reciprocating compressors are widely used for industrial, shipbuilding, air conditioning and refrigeration. However, since a mechanism for converting the rotational motion of the crankshaft into the reciprocating motion is applied, the imbalance force and the unbalance moment are applied to the compressor main body, and the vibration becomes serious.

To reduce the unbalance force and unbalance moment, research has been conducted to improve the balance weight design attached to the crankshaft of the reciprocating compressor or to reduce the vibration by changing the shape of the crankshaft. In addition, since the method of designing the balance weight varies according to the structure of the compressor such as the opposite type, the in-line type, and the V type, there are also studies considering the features and shapes of each structure.

Therefore, applicants of the present invention have studied an analytical approach to designing a crankshaft and a balance weight that minimizes the unbalance force and moment generated in a large multi-cylinder counterweight structure of a reciprocating compressor.

(0001) B. S. Ko, W. G. Hwang, K. W. Ahn, S. W. Park and S. M. Hee, 2003, "A Study on the Dynamic Characteristics of Reciprocating Compressors", Journal of the Korean Society for Noise and Vibration Engineering, pp. 478-485. (2000) SG Prak, HJ Lee, A. Abu, JY Lee and JE Oh, 2005, "Comparison of Vibration and Noise Characteristics for Reciprocating Air Compressor through the Change of Crankshaft Parameters", Journal of the Korean Society for Noise and Vibration Engineering , pp. 530-533.

It is an object of the present invention to provide a crankshaft of an opposed multi-cylinder reciprocating compressor which is configured to reduce the unbalanced moment on the reciprocating reciprocating compressor and to reduce the number and size of counterbalances.

According to the present invention, the above object is accomplished by a crankshaft comprising: N crank pins forming a 360 / N degree phase difference; A plurality of webs connecting the crank pin and the main journal; And a pair of counterbalances spaced apart from the crankpins and coupled to both ends of the main journal, the counterbalance having a phase difference of 180 degrees with respect to the crankpin.

N is 4, and the following equation is satisfied in the reciprocating motion of the piston, the piston rod, the crosshead and the connecting rod in conjunction with the rotational motion of the crank pin,

Here, ℓ ₁ is the distance to the outer crank pin from the crankshaft center, ℓ ₂ is the distance of the inner to the crank pin from the crankshaft center, ℓ _cw is the distance to the balance weight center from the shaft center, W _r are each W _cw is the centrifugal force of each balance weight, and? Is the phase angle of the balance weight.

N is 6, and the following equation is satisfied in the reciprocating motion of the piston, the piston rod, the crosshead, and the connecting rod in conjunction with the rotational motion of the crank pin,

Here, ℓ ₁ is the distance to the outer crank pin from the crankshaft center, ℓ ₂ is the distance of the inner to the crank pin from the crankshaft center, ℓ _cw is the distance to the balance weight center from the shaft center, W _r are each W _cw is the centrifugal force of each balance weight, and? Is the phase angle of the balance weight.

According to the present invention, by being coupled to both ends of the main journal by being separated from a pair of balanced additional crank pins having a phase difference of 180 degrees from each other, the unbalance moment applied to the reciprocating reciprocating compressor is reduced, It is possible to provide a crankshaft of an opposed multi-cylinder reciprocating compressor.

1 is a perspective view of a crankshaft of an opposed multi-cylinder reciprocating compressor in accordance with an embodiment of the present invention;
Fig. 2 and Fig. 3 are diagrams showing forces and moments acting on the crankshaft of the counter-rotating multi-cylinder reciprocating compressor of Fig. 1;
Fig. 4 and Fig. 5 are diagrams showing moments of the crankshaft of a conventional multi-cylinder reciprocating compressor without adding a balance according to the crankshaft angle and the crank angle of the counter-rotating multi-cylinder reciprocating compressor of Fig.
6 and 7 are views showing a force and a moment acting on a crankshaft of an opposed multi-cylinder reciprocating compressor according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the well-known functions or constructions are not described in order to simplify the gist of the present invention.

The crankshaft of the opposed multi-cylinder reciprocating compressor of the present invention is configured to reduce the unbalanced moment on the reciprocating reciprocating compressor and to reduce the number and size of counterweight.

FIG. 1 is a perspective view of a crankshaft of an opposed multi-cylinder reciprocating compressor according to an embodiment of the present invention, and FIGS. 2 and 3 are views showing a force and a moment acting on a crankshaft of the multi- FIGS. 4 and 5 are graphs showing moments of the crankshaft of the conventional multi-cylinder reciprocating compressor without adding a balance according to the crankshaft angle and the crank angle of the countercurrent multi-cylinder reciprocating compressor of FIG. 1. FIG. 6 and FIG. FIG. 6 is a view showing a force and a moment acting on the crankshaft of the reciprocating multi-cylinder reciprocating compressor according to another embodiment of the present invention.

Referring to Figure 1, the crankshaft 10 of an opposed multi-cylinder reciprocating compressor of the present invention is configured to reduce the unbalanced moment on the reciprocating reciprocating compressor and to reduce the number and size of counterbalances, 100, a main journal 200, a web 300, and a balance weight 400. [

N crank pins 100 are provided to form a 360 / N degree phase difference. An embodiment of the present invention is a crankshaft 10 of an opposite four-cylinder reciprocating compressor in which four crank pins 100 are provided to form a phase difference of 90 degrees (see FIG. 2) 6 shows a crankshaft 10 of an opposed six-cylinder reciprocating compressor in which six crank pins 100 are provided to form a phase difference of 60 degrees (see FIG. 6).

As shown in FIGS. 1 and 2, in an embodiment of the present invention, four crank pins 100 are provided to form a phase difference of 90 degrees. The plurality of webs 300 connect the crankpin 100 and the main journal 200. The balance weight 400 is separated from the crank pin 100 and is coupled to both ends of the main journal 200. The balance weight 400 has a phase difference of 180 degrees with respect to each other.

As shown in FIG. 1, the crankshaft 10 of the reciprocating four-cylinder reciprocating compressor according to an embodiment of the present invention is such that the balance weight 400 is positioned at both ends of the shaft at a constant phase angle.

The reason why the four crank pins 100 to which the pistons of the respective cylinders are mounted has a phase difference of 90 degrees is to minimize the torque fluctuation width due to the gas power generated in each cylinder.

Since the basic structure of the crankshaft 10 is opposed to each other, an unbalance force is generated when the sum of the masses of the pistons, the piston rods, the crossheads, and the connecting rods connected to the respective crankpins 100 are the same. I never do that. However, there is an imbalance in moment due to the difference in the distance to the point of action of each force based on the system center.

2 shows the force and moment acting on the crankshaft 10 equipped with the balance weight 400 according to a new balance weight design scheme in which the balance weight 400 is installed with a phase angle at both ends of the shaft. 3 is a diagram schematically illustrating various forces acting on the shaft (the main journal 200) viewed from the view 'A' direction of FIG.

F _x and F _y represent the components in the x and y directions, respectively. _{M 1, M 2, M 3} , M 4 represents the mass of the reciprocating motion is connected to each crank pin _{(100), a 1, a} 2, a 3, a 4 are mass reciprocates across the respective crankpin Respectively. Here, the number of the crank pin means the number of the crank pin. The reciprocating members include a piston, a piston rod, a portion of a connecting rod, a crosshead, and the like.

W _r is the centrifugal force of the rotating members which are caught by each crank pin. The rotating members include a crank pin 100 and a part of the connecting rod.

In Fig. 3, F _x1 and F _y1 are the component forces in the x and y directions acting on the crank pin 100, respectively, and M ₁ a ₁ is the inertia force of reciprocating members on the crank pin 100 (1) < / RTI >

Where W ₁ = M ₁ r? ² .

The resultant forces of the forces M ₁ a ₁ and W _r acting on the crankpin No. ₁ are expressed by the components in the x and y directions, respectively, as shown in [Equation 2] and [Equation 3].

The forces acting on the remaining three crank pins 100 can be expressed by the following equations (4) to (9) as in the case of the first crank pin (100).

Where W ₂ = M ₂ rω ² , W ₃ = M ₃ rω ² , and W ₄ = M ₄ rω ² .

2, in the design of the balance weight 400 of the crankshaft 10 according to the embodiment of the present invention, the balance weight 400 has the phase angle of the crank pin 100 and the phase difference of? And the second balance weight 400 is installed so as to have a phase difference of 180 degrees from the first balance weight 400. The forces due to the balance weight 400 can be calculated as shown in Equations (10) to (13) .

Where W _cω is the centrifugal force of each balance weight 400.

The moment components in the x and y directions of the moment acting on the crankshaft 10 based on the center point of the crankshaft system are obtained by Equation (14) and Equation (15), respectively.

2, ℓ ₁ is the distance from the center of the shaft to the center of the crank pin 100, and ℓ ₂ is the distance from the center of the shaft to the center of the crank pin 100 of No. 2 and No. 3 The distance, _c , represents the distance from the center of the shaft to the center of the balance weight (400).

the sum of the moments in the x direction and the y direction can be found by the following equation (16), and the average of the time is summarized by the following equation (17).

Here, b, c, d, f, and? Are as shown in the following equation (18).

In Equation (17), since all the terms except the last term are positive, the average value of the moments becomes minimum if the last term is minimum. In order for the last term of Equation (17) to be minimized, alpha + beta = 1.5 [pi], and the total moment average is then compiled as in Equation (20).

The f-number at which the moment is minimum is as follows,

The f value satisfying this condition is expressed by Equation (21).

In the above equation (18), since f = 2 _{l cω} W _cω , W _cω is finally set as shown in the following equation (22).

Further, the phase angle? Of the balance weight is summarized by the following equation (23) from the equation (19).

The new balance weight 400 design means for minimizing the unbalance moment in the design of the balance weight 400 of the crankshaft 10 of the opposed four-cylinder compressor according to an embodiment of the present invention is expressed by Equation (22) Can be represented by a balance weight 400 design having a balance weight centrifugal force and a weight balance phase angle expressed by Equation (23).

Case # 1 and case # 2 below show the result of calculating W _cω and α by substituting values into the respective variables of [Equation 22] and [Equation 23]. Table 1 shows the common values (Geometric data and related mass values) of each variable used in case # 1 and case # 2, and the values according to case # 1 and case # 2 (Piston mass of each case.

Notation Description Value Unit m _pr Piston rod mass 3.9 kg m _cr Connecting rod mass 12.1 kg m _ch Cross head mass 15.2 kg m _cp Crank pin mass 4.0 kg r Crank arm 37.5 mm L _c Connecting rod length 220 mm ℓ _c1 Length from con rod center to crank pin center 82.77 mm ℓ _c2 Length from con rod center to cross head pin 137.23 mm ℓ ₁ Distance from shaft center to Crank pin 1,4 387.5 mm ℓ ₂ Distance from shaft center to Crank pin 2,3 257.5 mm ℓ _cω Distance from shaft center to Counterweight 1,2 593.25 mm ω Rotating speed 600 RPM

Notation Description case # 1 case # 2 Unit m _p1 1st Piston mass 21.1 21.1 kg m _p2 2nd Piston mass 10.1 10.1 kg m _p3 3rd Piston mass 21.1 21.1 kg m _p4 4th Piston mass 8.1 10.1 kg

case # 1

Case # 1 is a case in which the pistons 1 and 3 have the same weight and the pistons 2 and 4 have different weights. The centrifugal force W _cω of the counterweight 400 which minimizes the moment is _calculated from W _cω = _764.1 [N] from the equation (22) and the phase angle α of the counterweight 400 from the equation (23) to α = 342 ° do.

4 is an illustration showing the comparison of moment (Mo) and case # 1 the moment (M _new) in the absence of additional balance according to the crank angle. The average of each of them is M _o = 1030.5 [Nm] and M _new = 650.4 [Nm], and case # 1 is the smallest. The variation range is -76.7 to +68.5% when the balance is not added, and -31.6% to +29.3% when the balance weight 400 is designed as the case # 1 of the embodiment of the present invention.

case # 2

Case # 2 is a case in which the weight of piston # 1 is the same as that of piston # 3, and the weight of pistons # 2 and # 4 are the same. The centrifugal force W _cω of the counterweight 400 which minimizes the moment is _calculated from W _cω = 780.4 [N] from the equation (22) and the phase angle α of the counterweight 400 from the equation [23] do.

5 is an illustration showing the comparison of moment (Mo) and case # 2 moment (M _new) in the absence of additional balance according to the crank angle. The mean of each case is the smallest case # 2 with M _o = 1048.3 [Nm] and M _new = 656.6 [Nm]. The variation range is -75.4 to +65.6% when the balance is not added, and -27.8% to + 26.0% when the balance weight 400 is designed as the case # 1 of the embodiment of the present invention.

Referring to FIGS. 6 and 7, in another embodiment of the present invention, six crank pins 100 are provided to form a phase difference of 60 degrees. The plurality of webs 300 connect the crankpin 100 and the main journal 200. The balance weight 400 is separated from the crank pin 100 and is coupled to both ends of the main journal 200. The balance weight 400 has a phase difference of 180 degrees with respect to each other.

Referring to FIG. 6, the crankshaft 10 of the reciprocating six-cylinder reciprocating compressor according to another embodiment of the present invention is configured such that the balance weight 400 has a constant phase angle at both ends of the shaft.

F _x and F _y represent the components in the x and y directions, respectively. _{M 1, M 2, M 3} , M 4, M 5, M 6 represents the mass of the reciprocating motion is connected to each crank pin _{(100), a 1, a} 2, a 3, a 4, a 5, a ₆ represents the acceleration of the reciprocating masses applied to each crank pin. Here, the number of the crank pin means the number of the crank pin. The reciprocating members include a piston, a piston rod, a portion of a connecting rod, a crosshead, and the like.

W _r is the centrifugal force of the rotating members which are caught by each crank pin. The rotating members include a crank pin 100 and a part of the connecting rod.

In Fig. 7, F _x1 and F _y1 are the component forces in the x and y directions acting on the crank pin 100, respectively, and M ₁ a ₁ is the inertia force of the reciprocating members on the crank pin 100 As shown in the following equation (24).

Where W ₁ = M ₁ r? ² .

The resultant force of the forces M ₁ a ₁ and W _r acting on the No. 1 crank pin 100 is expressed by the components in the x and y directions as shown in Equation 25 and Equation 26, respectively.

The forces acting on the remaining five crank pins 100 can be expressed by the following equations (27) to (36).

Here, W ₂ = M ₂ rω ² , W ₃ = M ₃ rω ² , W ₄ = M ₄ rω ² , W ₅ = M ₅ rω ² , and W ₆ = M ₆ rω ² .

6, in the design of the balance weight 400 of the crankshaft 10 according to another embodiment of the present invention, the first balance weight 400 has the phase angle of the crankpin No. 1 and the phase difference of? And the second balance weight 400 is installed so as to have a phase difference of 180 degrees from the first balance weight 400. The forces due to the balance weight 400 are calculated as shown in Equations 37 to 40 .

Where W _cω is the centrifugal force of each balance weight 400.

The moment components in the x and y directions of the moment acting on the crankshaft 10 based on the center point of the crankshaft system are obtained as shown in Equations (43) to (46).

6, ℓ ₁ is the distance from the center of the shaft to the center of the crank pin 100, and ℓ ₂ is the distance from the center of the shaft to the center of the crank pin 100 of No. 2 and No. 5 ℓ ₃ is the distance from the center of the shaft to the center of the crank pin (100), and ℓ _cω is the distance from the shaft center to the center of the balance weight (400).

The average value of the moments in the x and y directions with respect to time is summarized as shown in Equation (47).

Here, a, b, c, d, and e are as shown in the following equation (48).

In Equation (47), since all the terms other than the last term are positive, the average value of the moments becomes minimum if the last term is minimum. In order for the last term of Equation (47) to be minimum, alpha + beta = 1.5 [pi].

The c value at which the moment is minimum is as follows,

The c value satisfying this condition is expressed by Equation (51).

Since c = 2 _{l cω} W _cω in the above equation (48), W _cω is finally set as shown in (52).

Further, the phase angle? Of the balance weight is summarized by the following equation (53) from the equation (50).

The new balance weight 400 design means for minimizing the unbalanced moment in the design of the balance weight 400 of the crankshaft 10 of the opposed six-cylinder compressor according to another embodiment of the present invention can be expressed by Equation 52 Can be represented by a balance weight 400 design having a balance weight centrifugal force and a weighted phase angle expressed by (53).

According to the present invention, by being coupled to both ends of the main journal by being separated from a pair of balanced additional crank pins having a phase difference of 180 degrees from each other, the unbalance moment applied to the reciprocating reciprocating compressor is reduced, It is possible to provide a crankshaft of an opposed multi-cylinder reciprocating compressor.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is obvious to those who have. Accordingly, it should be understood that such modifications or alterations should not be understood individually from the technical spirit and viewpoint of the present invention, and that modified embodiments fall within the scope of the claims of the present invention.

10: Crankshaft
100: crank pin
200: Main Journal
300: web
400: Balance

Claims (3)

delete Four crank pins forming a phase difference of 90 degrees;
A plurality of webs connecting the crank pin and the main journal; And
And a pair of balance weights separated from the crank pin and coupled to both ends of the main journal and having a phase difference of 180 degrees with each other,
The piston, the piston rod, the crosshead, and the connecting rod reciprocatingly move in conjunction with the rotational motion of the crank pin,

Here, ℓ ₁ is the distance to the outer crank pin from the crankshaft center, ℓ ₂ is the distance of the inner to the crank pin from the crankshaft center, ℓ _cw is the distance to the balance weight center from the shaft center, W _r are each _Wherein W _cw is the centrifugal force of each balance weight, and? Is the phase angle of the balance weight. The crankshaft of the reciprocating multi-cylinder reciprocating compressor according to claim 1, Six crank pins forming a phase difference of 60 degrees;
A plurality of webs connecting the crank pin and the main journal; And
And a pair of balance weights separated from the crank pin and coupled to both ends of the main journal and having a phase difference of 180 degrees with each other,
The piston, the piston rod, the crosshead, and the connecting rod reciprocatingly move in conjunction with the rotational motion of the crank pin,

Here, ℓ ₁ is the distance to the outer crank pin from the crankshaft center, ℓ ₂ is the distance of the inner to the crank pin from the crankshaft center, ℓ _cw is the distance to the balance weight center from the shaft center, W _r are each _Wherein W _cw is the centrifugal force of each balance weight, and? Is the phase angle of the balance weight. The crankshaft of the reciprocating multi-cylinder reciprocating compressor according to claim 1,

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