JPH04321785A - Variable crank mechanism of scroll compressor - Google Patents

Abstract

PURPOSE:To reduce vibration noise and mechanical loss by slightly shifting the centrifugal force working line of a main balance weight from the center of an eccentric shaft to the side of a pivot pin and letting gas compression load work so that the eccentric shaft is rotated in the direction to enlarge its eccentric quantity. CONSTITUTION:The centrifugal force working line of a main balance weight 9 is slightly shifted from the center of an eccentric shaft 5 to the side of a pivot pin 4 so as to balance the rotary moment generated by the centrifugal force of a scroll 3 revolving around the center of the pivot pin 4 and the rotary moment generated by the main balance weight 9. An eccentric shaft 5 is rotated or slid until the clearance between laps become zero due to the component of force. Since a rotary scroll lap is thus made to be pressed to a fixed scroll lap at an approximate small constant force without depending upon revolution, a high efficient scroll compressor of small mechanical loss and leakage loss in a wide variable range can be realized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable crank mechanism that can be applied to scroll compressors for refrigeration and air conditioning, air use, and all other scroll compressors, and that improves performance by reducing leakage and mechanical loss.

0002

[Prior Art] The conventional variable crank mechanism is
As seen in No. 88645, it had a driven crank structure in which the centrifugal force of the main balance weight acted on a line connecting the center of the main shaft and the center of the eccentric shaft. Due to the design of balancing the inertia of the entire system, the centrifugal force of the main balance weight is greater than the centrifugal force of the orbiting scroll, so the eccentric shaft receives a force in a direction that reduces the radius of rotation. In order to offset this force and apply a force in the direction of increasing the turning radius, and to eliminate the radial gap between the wraps, the moment due to the gas compression load is used to increase the turning radius around the pivot pin. A force was applied that rotated the eccentric shaft in the direction of increasing the size.

[0003] In Japanese Patent Application Laid-Open No. 147389/1989, the main balance weight is divided into two parts in the driven crank structure, but this is intended to solve the problem of space.

0004

[Problem to be solved by the invention] In the conventional structure, the centrifugal force of the main balance weight directly acts on the eccentric shaft, creating an unbalance with the centrifugal force of the orbiting scroll, so the amount of unbalance varies depending on the rotation speed. Almost,
This centrifugal force cannot always be balanced with a constant gas compression load. Therefore, if a variable speed compressor is designed to have an appropriate lap contact load at high speed rotation, the centrifugal force will be small at low speed rotation, so the gas compression load will become too large and the lap contact load will increase. It may become excessive. If the wrap contact load becomes excessive, it may cause vibration and noise, increase mechanical loss and degrade performance, or increase wear on the wraps and reduce reliability.

The purpose of the present invention is to always balance the centrifugal force of the main balance weight with the centrifugal force of the orbiting scroll, so that a part of the gas compression load is applied in the direction of increasing the radius of rotation of the eccentric shaft, thereby increasing the rotation speed. To provide a highly efficient and highly reliable scroll compressor with little vibration, noise, mechanical loss, and little wear on the laps by keeping the lap contact load almost constant regardless of the fluctuation.

[0006]

[Means for solving the problem] The first method is to slightly shift the line of action of the centrifugal force of the main balance weight from the center of the eccentric shaft toward the pivot pin in the driven crank structure, and to create an orbiting scroll centered on the pivot pin. The rotational moment due to the centrifugal force of the main balance weight should be balanced with the rotational moment due to the main balance weight. Then, a gas compression load is applied so that the eccentric shaft rotates about the pivot pin in a direction that increases the amount of eccentricity.

[0007] The second method is to divide the main balance weight into two parts, attach one part to an eccentric shaft so that its centrifugal force balances the centrifugal force of the orbiting scroll, and the other part to a size that generates the remaining centrifugal force. and attach it to the main shaft. Then, by using a mechanism of a non-circular shaft and a hole that are fitted so that the eccentric shaft can slide in the radial direction relative to the main shaft, the sliding direction is tilted from the eccentric direction to the counter-rotational direction, and the gas compression load is A force is applied to increase the amount of eccentricity of the eccentric shaft.

[0008]

[Operation] In either structure, the acting force due to the gas compression load can be set arbitrarily, so it is set so that the orbiting scroll wrap is always pressed against the fixed scroll wrap with an appropriate force. By doing this, the gap in the radial direction between the orbiting scroll wrap and the fixed scroll wrap becomes zero, and leakage is reduced even at low speed rotation, so that high performance can be achieved. In addition, since the pressing force of the wrap is always at an appropriate level regardless of the rotation speed, vibrations and
Less noise. Additionally, there is less wear on the wrap.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a general hermetic scroll compressor. A compressor section consisting of a fixed scroll 2 and an orbiting scroll 3, a drive shaft consisting of a main shaft 4 and an eccentric shaft 5 for driving the orbiting scroll 3, a frame 6 for supporting the main shaft 4 and fixing the fixed scroll, and a frame 6 for supporting the main shaft 4 and fixing the fixed scroll; A driving electric motor is attached to the bottom, and these are housed together. The orbiting scroll 3 is restrained from rotating by the Oldham ring 7, and is driven to rotate by the eccentric shaft 5 as the main shaft 4 rotates. A main balance weight 9 and a sub-balance weight 10 are attached to the main shaft 4 in order to counteract the centrifugal force of the orbiting scroll and prevent vibrations from occurring. Gas is sucked in through the suction pipe 11, compressed in the compression chamber 12, discharged from the discharge port 13 into the discharge chamber, passes through the lower chamber 16, and is discharged from the discharge pipe 17 to the outside of the closed container. Oil 18 is supplied to the bearings and sliding parts from below the main shaft.

The relationship between the centrifugal forces of the orbiting scroll and the balance weight will be explained with reference to FIG. The drive shaft consists of a main shaft 4 and an eccentric shaft 5, and the centrifugal force Fc of the orbiting scroll 3 acts on the eccentric shaft. A main balance weight 9 is attached to the upper part of the main shaft 4 and a sub-balance weight 10 is attached to the lower part of the main shaft 4 in order to offset Fc. The centrifugal force of the main balance weight 9 is Fb, and the centrifugal force of the sub balance weight 10 is Fb.
s, the distance between the axial centers of gravity of the orbiting scroll 3 and the sub-balance weight 10 is Lc, and the distance between the axial centers of gravity of the main balance weight 9 and the sub-balance weight 10 is Lb, then the following relationship exists between these: .

[0011]

[Equation 1] Fb=Fc
+Fbs
(1)

0012

[Math. 2] Fc×Lc
=Fb×Lb
(2) Equation (2) is transformed as follows.

[0013]

[Math 3] Fb/Fc
=Lc/Lb(>1)
(3) As can be seen from equations (1) and (3), fb is larger than Fc.

A first embodiment of the present invention will be explained with reference to FIGS. 3 and 4.

FIG. 3 shows the assembly of the inventive parts of the first embodiment. The main shaft 4, eccentric shaft 5, and main balance weight 9 are constructed separately. A pivot pin 4b and a stopper hole 4b are provided in the upper part of the main shaft 4. First, the main balance weight 9 is combined with the main shaft 4. The main balance weight 9 has an elongated hole 9 with a width that fits the pivot pin 4b without a gap, and a length that is slightly longer than this.
b and an engagement hole 9c are provided. Assembly is performed by passing the pivot pin 4b through the elongated hole 9b. Next, the eccentric shaft 5 is assembled. The eccentric shaft 5 is provided with a pivot hole 5b, and the base portion 5a is provided with a main balance weight engagement pin 6c.
is placed facing downward. The pivot pin 4b is fitted into the pivot pin 4b, and the engagement pin 6c is fitted into the engagement hole 9c. The engagement pin 6c is further inserted into the stopper hole 4c. The diameter of the stopper hole 4c is slightly larger than the diameter of the engagement pin 6c, and the eccentric shaft 5 can rotate slightly around the pivot pin 4b.

The positional relationship of each part on a plan view and the action of force will be explained with reference to FIG. For convenience, the directions are defined by assigning symbols to x and y, respectively, as shown in the figure. Oc is the center of the principal axis 4. Os is the center of the eccentric shaft 5 and is located at a distance of the turning radius from Oc. It is now assumed that the main shaft 4 rotates clockwise. The pivot pin 4b and the pivoted hole 5b move Lsx in the +x direction with respect to Os,
It is located at the position Lsy in the +y direction.

Ob is the center of the main balance weight engagement pin 5c and the engagement hole 4c. Ob is located at a position Lbx in the +x direction from Oc and Os. Moreover, Ob is located in the -y direction relative to Os.

The centrifugal force Fc of the orbiting scroll acts on Os in the +y direction. When the gas compression load is divided into a swing orbit tangential load Fgt and a radial load Fgr, it acts as shown in the figure. The center of gravity of the main balance weight 9 is on a straight line passing through Os and Oc, but since the elongated hole 9b is restrained only in the x direction from the pivot pin 4b and not in the y direction, the centrifugal force Fb of the main balance weight 9 is Ob
It acts in the -y direction. Here, Lsx and Lbx
Set as follows.

[0019]

[Math. 4] Lbx/L
sx=Fc/Fb
(4) The moment of centrifugal force centered on Od is as follows, with the clockwise direction being positive.

1) The moment Mc due to the centrifugal force of the orbiting scroll + eccentric shaft is

[0021]

[Formula 5] Mc=Fc
×Lsx
(5)2) The moment Mb due to the centrifugal force of the main balance weight is

[0022]

[Formula 6] Mb=-F
b×Lbx
(6) From the relationship of equation (4), Mc+
Mb=0, and the loads due to centrifugal force acting on the eccentric shaft are balanced.

When the mass of the orbiting scroll is ms, the radius of rotation is ε, the mass of the balance weight is mb, and the radius of the center of gravity is e, Fc and Fb are expressed by the following equations.

[0024]

[Formula 7] Fc=ms
×ε
(7)

[0025]

[Formula 8] Fb=mb
×e
(8) Therefore, equation (4) can be expressed as follows.

[0026]

[Formula 9] Lbx/L
sx=ms×ε/(mb×e)
(9) On the other hand, the relationship between the moment due to the gas compression load is as follows.

1) Moment Mgt due to tangential load Fgt

[0028]

[Formula 10] Mgt=F
gt×Lsy
(10) 2) Moment Mgr due to radial load Fgr

00
29]

[Formula 11] Mgr=-
Fgr×Lsx
(11) When Mgt+Mgr is set to be positive, the eccentric shaft 5 receives a force in a direction that increases the amount of eccentricity. When the difference between the diameter of the stopper hole 4c and the diameter of the engagement pin 5c is set appropriately, the orbiting scroll wrap 3a shown in FIG. 1 is pressed against the fixed scroll wrap 2a,
The gap becomes 0. Expressing this condition in equations, equation (10), (
11), it can be expressed as follows.

[0030]

[Formula 12] Fgt×L
sy-Fgr×Lsx>0
(12) When formula (12) is transformed, it becomes as follows.

[0031]

[Formula 13] 1>Lsy
/Lsx>Fgr/Fgt
(13) If Lsx and Lsy are set so that Mgt+Mgr is as small as possible without becoming negative in the entire operating range required for the compressor, the pressing force of the wrap can be small and the gap can be reduced to 0. Usually, Fgr is smaller than Fgt, so Fgr/Fgt
<1, and the appropriate relationship between Lsx and Lsy can be expressed as follows.

[0032]

[Formula 14] Lsy/L
sx>Fgr/Fgt
(14) Therefore, the proper pivot pin 4
b and the position of the pivoted hole 5b, Lsx and L under the condition that the differential pressure between the discharge pressure and the suction pressure is the largest within the operating range.
It is sufficient to set it at an appropriate position where sy satisfies equation (19).

Next, a second embodiment of the present invention will be explained with reference to FIGS. 5 and 6.

FIG. 5 shows the assembly of the inventive parts of the second embodiment. The main shaft 4 and the eccentric shaft 5 are constructed separately. A rectangular drive shaft 4d is provided above the main shaft 4. An eccentric shaft 5 is attached to the main shaft 4. Eccentric shaft 5
is provided with a rectangular driven hole 5d which is fitted with the drive shaft 4d with a small gap in width and has a slightly larger gap in the direction perpendicular to this, and the base portion 5a has a main balance weight main portion. The mounting hole 9Aa of 9A is attached by a blind fit or the like. Further, the main balance weight sub-portion 9B is attached under the drive shaft 4d in a similar manner.

The positional relationship of each part on a plan view and the effect of force will be explained with reference to FIG. For the sake of convenience, the directions are defined here by assigning symbols to x and y, respectively, as shown in the figure. Oc is the center of the principal axis 4. Os
is the center of the eccentric shaft 5 and is located at a distance of the turning radius from Oc. It is now assumed that the main shaft 4 rotates clockwise. The sliding surfaces of the driving shaft 4d and the driven hole 5d are set to be slightly inclined with respect to the y-axis. The eccentric shaft 5 is movable in the direction of the sliding surface by the gap between the drive shaft 4d and the driven hole 5d.

The centrifugal force Fc of the orbiting scroll acts on Os in the +y direction. The gas compression loads are a swing orbit tangential load Fgt and a radial load Fgr. The centrifugal force Fb1 of the main balance weight main portion 9A acts on the eccentric shaft 5 in the -y direction. The centrifugal force Fb2 of the main balance weight sub-portion acts on the main shaft 4 in the -y direction. Fb1 and Fb
2 and the upper b of equation (1) are set as follows.

[0037]

[Formula 15] Fb1+F
b2=Fb
(15) Furthermore, Fb1 is set as follows so that the centrifugal force acting on the eccentric shaft is always balanced.

[0038]

[Formula 16] Fb1=F
c.
(16) Figure 7 shows the slope θ of the sliding surface of the drive shaft 4d and the driven hole 5d and the tangential load Fgt.
This shows the effect of y-direction component force of Fgt Fgt
y is expressed as follows.

[0039]

[Formula 17] Fgty=
Fgt×tanθ
(17) When θ is set so that Fgty is slightly larger than Fgr, the orbiting scroll wrap 3a shown in FIG. 1 is pressed against the fixed scroll wrap 2a with a small force, and the gap becomes zero. Furthermore, since Fgr is usually smaller than Fgt, Fgty does not need to exceed Fgt. Expressing the above relationship in a formula, we get

[0040]

[Formula 18] Fgt>F
gty>Fgr
(18) Substituting equation (17), equation (18) becomes,

[0041]

[Formula 19] Fgt>F
gt×tanθ>Fgr
(19) Transforming equation (19), we get

[0042]

[Formula 20] 1>tan
θ>Fgr/Fgt
(20) Therefore, the appropriate inclination angle θ of the sliding surface may be set to an appropriate value that satisfies equation (20) under conditions where the differential pressure between the discharge pressure and the suction pressure is the largest within the operating range.

Next, a third embodiment of the present invention is shown in FIG. In this embodiment, the drive mechanism has the same structure as the first embodiment, and the balance weight has the same structure as the second embodiment. In this example, the same effect can be achieved by setting the positions of the pivot pin and pivoted hole so as to satisfy equation (14), and designing the main balance weight so as to satisfy equations (15) and (16). The gains are clear.

[0044]

[Effects of the Invention] According to the present invention, the centrifugal force of the orbiting scroll and the eccentric shaft is constantly balanced, and the gas compression load is utilized which is almost constant regardless of the rotation speed as long as the pressure condition is constant. By applying a radial force to the eccentric shaft, the orbiting scroll wrap is pressed against the fixed scroll wrap with a small force, so the contact load on the wrap does not increase during high-speed operation, and it also prevents the contact load from increasing during low-speed operation. Since the pressing load is ensured, there will be no gaps between the wraps, and no leakage will occur. Therefore, it is possible to realize a highly efficient scroll compressor with small mechanical loss and leakage loss over a wide variable speed range. Furthermore, since the pressing load between the wraps is always appropriate, there is less vibration and noise, less wear on the wraps, and a quiet and highly reliable scroll compressor can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a general scroll compressor.

FIG. 2 is an explanatory diagram showing the relationship between the centrifugal force of the orbiting scroll and the balance weight.

FIG. 3 is a perspective view of an inventive part showing a first embodiment of the present invention.

FIG. 4 is a plan view showing the load and positional relationship of the first embodiment.

FIG. 5 is a perspective view of an inventive part showing a second embodiment of the present invention.

FIG. 6 is a plan view showing the load and positional relationship of the second embodiment.

FIG. 7 is a partial plan view showing the relationship between the inclination angle of the slide surface and the load in the second embodiment.

FIG. 8 is a perspective view of an inventive part showing a third embodiment of the present invention.

[Explanation of symbols]

3...Orbiting scroll, 4...Main shaft, 5...Eccentric shaft, 9...Main balance weight, 10...Sub balance weight.

Claims (1)

[Claims] 1. A fixed scroll member having a spiral wrap upright on an end plate and an orbiting scroll member are combined with the wraps facing each other and eccentrically arranged, and the orbiting scroll member is rotated without rotating on its axis to generate gas. In a scroll compressor that compresses are rotatably engaged, and the position of the pivot pin and the pivoted hole is on the outer circumferential side of a tangent to the orbit circle passing through the center of the eccentric shaft, and is in a plane connecting the center of the eccentric shaft and the center of the main shaft. The eccentric shaft is located at a position further advanced in the rotational direction, and an engaging pin that engages the main balance weight to apply centrifugal force is provided at the lower part of the eccentric shaft, and the center position of the engaging pin is the same as the center of the eccentric shaft. A variable crank mechanism for a scroll compressor, characterized in that the variable crank mechanism is shifted toward the center of the pivot pin from a plane passing through the center of the main shaft.