JPS6255028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing stress generated in the welded portion of a compressor in which a shell and a shell plate are assembled by welding when high internal pressure is applied.

Conventionally, there are devices shown in FIGS. 5 and 6 as common devices of this type. FIG. 5 is a cross-sectional view showing an example of a rotary compressor, and FIG. 6 is a vertical cross-sectional view of a main part thereof. In the diagram, 1 is Ciel, 2 is Ciel 1
3 is a weld bead for joining the outer surface of the open end of the shell 1 and the shell plate 2 with a fillet joint; 5 is a weld bead that penetrates the shell plate 2 and is rotatable; 6 is a drive mechanism for transmitting the driving force of an electric motor (not shown) to the crankshaft 5 via a pulley 6a; 7 is a drive mechanism provided in the shell 1 and driven by the crankshaft 5; It is a rotary compression element. The compression element 7 is a cylinder 8
A rotary piston 8a is provided therein, an eccentric portion 5a of a crankshaft 5 driven by a drive mechanism 6 is fitted into the rotary piston 8a, and the cylinder 8 is slidably fitted onto the outer peripheral surface of the rotary piston 8a. Vane 8
b is pressed by the coil spring 8c to form the compression chamber 11.
is divided into a low pressure side and a high pressure side. 1
6 is a suction port along the cylinder 8 in the radial direction;
This suction port 16 is connected to a suction pipe 17 extending into the shell 1. 18 is a discharge pipe connected to the compression chamber 11 via a discharge valve 18a.

The conventional rotary compressor has the above-mentioned configuration, and as the crankshaft 5 is rotated by the drive mechanism 6, the rotary piston 8a is inscribed in the cylinder 8 and rotates eccentrically along the inner circumferential surface of the cylinder 8. The refrigerant sucked into the suction port 16 from the suction pipe 17 enters the compression chamber 1.
1, this refrigerant is compressed from low pressure to high pressure by the rotation of the rotary piston 8a and the vanes 8b, and is discharged outside the compression element 7. Next, in the conventional compressor mentioned above, the pressure difference between the external pressure and the internal pressure of shell 1 (hereinafter referred to as internal pressure)
When this occurs, stress generated at the weld between the opening of the shell 1 and the shell plate 2 will be explained.

Fig. 1 is a schematic cross-section showing the compression element and the drive mechanism omitted, and in the figure 4 is the central axis of the shell 1, h
is the inside height of the compressor and r is the inside radius of shell 1. FIG. 2 is a stress model diagram schematically showing the stress (bending moment) generated in the weld when internal pressure is generated in the apparatus shown in FIG.
In the figure, p is the pressure difference between external pressure and internal pressure (hereinafter referred to as
It is simply written as internal pressure. ), t is the plate thickness of the shell, 9 is the stress component parallel to the central axis 4 of the shell 1 (hereinafter referred to as perpendicular) among the stress generated in the weld bead 3 when the internal pressure p acts on the shell 1 and the shell plate 10 is a stress component perpendicular to the compressor center axis 4 (hereinafter referred to as horizontal stress), l is the leg length of the weld bead 3 on the shell plate 2 side.

Next, the stress generated in the welded portion when internal pressure acts on the compressor will be explained using a simple model based on FIG. 2. As a result of a basic experiment using a compressor pressure test, it was found that the weakest part of the weld is the boundary between the weld bead 3 and the shell plate 2. Therefore, regarding the vertical stress 9 and horizontal stress 10 that occur at this boundary. think. Assuming that the stress is uniformly distributed at the boundary between the weld bead 3 and the shell plate 2, the vertical stress 9 is
r ² p/{(r+t+l) ² -(r+t) ² )}, and the horizontal stress 10 is given by 2rph/{(r+t+l) ²
−(r+t) ² }, so vertical stress 9/horizontal stress 10=r/2h. In a normal compressor, h>r, so r/2h<1
becomes. Further, the vertical stress 9 acts as a tensile stress on the boundary between the weld bead 3 and the shell plate 2, and the horizontal stress 10 acts as a shear stress on the boundary. In general, the fracture resistance of metal materials to shear loads is lower than that to tensile loads, and furthermore, as mentioned above, the stress value of shear stress is higher than that of tensile stress, so the horizontal stress acting on the weld bead 3 10 is
It is thought that this contributes more than the normal stress 9 acting on the weld bead to the destruction of the weld bead 3 and shell plate 2 in a compressor where internal pressure p acts. Although not specifically explained in the figure, when the shell thickness t is small, the shell 1 is distorted outward when the internal pressure p is generated in the compressor, and a large bending moment is generated at the root of the weld bead 3. act and cause destruction.

As described above, in conventional compressors, when high internal pressure occurs, significant shear stress and bending moment are generated at the boundary of the weld on the shell plate side. However, when the heat input is increased, the distortion of the shell plate becomes large, which deteriorates the characteristics of the compressor and causes cracks to occur in the welded parts.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by fitting a ring having an inner diameter equal to or smaller than the outer diameter of the member on the outer periphery of the shell, the shell and the shell plate can be fixed. The purpose is to reduce the shear stress and bending moment that occur in the welds.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, 12 is an O-shaped ring fitted around the outer periphery of the shell 1, and H is the distance between the lower end surface of the ring and the inner surface of the top of the shell. If the ring 12 is sufficiently thick, when internal pressure p occurs in the compressor,
Due to the rigidity of the ring 12, the shear load generated between the weld bead 3 and the shell plate 2 is approximately 2π.
rHp decreases. Moreover, since the shell 1 is restrained by the ring 12, even if high internal pressure occurs, the portion of the shell 1 below the ring 12 is prevented from deforming, and almost no bending moment acts on the weld bead 3.

However, the ring 12 and the shell plate 2
If the distance between the ring 12 and the weld bead 3 is made larger than 1/3 of the height of the shell 1, the reinforcing effect of the ring 12 will be low, and the deformation of the shell 1 between the ring 12 and the weld bead 3 will cause the ring 12 to The stress generated in the weld bead 3 is almost the same as that without the weld bead 3, and the stress generated in the weld bead 3 does not decrease. Furthermore, if the thickness of the ring 12 is made thinner than the plate thickness t of the shell, the reinforcing effect of the ring 12 will be low, and if it is made thicker than 5t, the rigidity of the ring 12 will exceed the required value, leading to an increase in weight.
The thickness of the ring 12 is preferably greater than or equal to t and less than or equal to 5 t, since this will adversely affect the welding process between the shell 1 and the shell plate 2.

Although the above embodiment has been described with one O-ring fitted around the outer periphery of the shell, the ring produces the same effect regardless of the shape, number, or method of fixing the ring. Figure 4 shows a ring with one slit 15 on the outer circumference of the shell.
FIG. In this case, since the welded portion 14 of the ring contracts, the tightening force of the ring acts strongly, the deformation resistance of the ring against internal pressure increases, and the reinforcing effect becomes even greater. Furthermore, although the above embodiments have been described with respect to a compressor, a pressure vessel having a welded structure may also be used, and the same effects as in the above embodiments can be obtained.

As mentioned above, by fitting the ring around the outer circumference of the shell, the compressor can withstand high internal pressure, and the welding heat input can be reduced to about 2/3 of the conventional one, so the shell plate This has the remarkable effect of reducing welding distortion to approximately 1/2 of that of conventional methods and improving compressor characteristics.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a conventional compressor with the compression element and drive mechanism omitted, Fig. 2 is a stress model diagram corresponding to the welded part of Fig. 1, and Figs. A schematic cross-sectional view and a schematic external view of the compressor according to the embodiment with the compression element and drive mechanism omitted, and FIGS. 5 and 6 are a cross-sectional view and a longitudinal cross-sectional view showing a conventional general compressor. 1...Ciel, 2...Ciel plate, 3...
Weld bead, 12...Ring, and the same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a device having a shell and a shell plate, a ring having an inner diameter equal to or smaller than the outer diameter of the shell is attached to the outer periphery of the shell by welding or shrink fitting, A pressure vessel such as a compressor, characterized in that at least one plate is fitted. 2. The shell according to claim 1, characterized in that the shell is constituted by a ring having at least one slit, at least one ring is attached to the shell, and the slit portion is joined by welding. Pressure vessels such as compressors. 3. Before welding the shell and shell plate,
2. A pressure vessel such as a compressor according to claim 1, wherein a ring is fitted in advance near a welded portion of the shell, and the shell, shell plate, and ring are integrally joined. 4. A pressure vessel such as a compressor according to claim 1 or 2, characterized in that the distance between the ring and the shell plate is 1/3 or less of the height of the shell. 5. Compression according to claim 1 or 2 or 3 or 4, characterized in that the thickness of the ring is greater than or equal to the thickness of the shell and less than or equal to 5 times the thickness of the shell. Pressure vessels such as machines.