CN1005039B

CN1005039B - Discharge valve of refrigeration compressor

Info

Publication number: CN1005039B
Application number: CN85101566.2A
Authority: CN
Inventors: 石岛小二; 左野文明; 和田文雄; 浅海和知
Original assignee: Mitsubishi Corp
Current assignee: Mitsubishi Corp
Priority date: 1985-04-01
Filing date: 1985-04-01
Publication date: 1989-08-23
Also published as: CN85101566A

Abstract

A discharge valve for a refrigeration compressor comprising a leaf spring 10 for biasing a deformable valve plate 9 for opening and closing a refrigerant discharge hole 8. The leaf spring has a central deformed portion that presses against the middle of the valve disc. When the discharge hole is initially opened, the free end 9a of the valve plate is not subject to spring force, thereby reducing the opening delay and improving the efficiency of the compressor.

Description

Discharge valve in refrigeration compressor

The present invention relates to a discharge valve for a rotary refrigeration compressor.

Fig. 1 to 4 show a rotary refrigeration compressor disclosed in japanese patent publication 57174773, in which a motor 2 and a compressor assembly 3 are installed in a closed casing 1, the compressor assembly 3 including a cylinder block 4, a crankshaft 5, a rotary piston 6, radially slidable vanes (not shown), and supporting end plates 7a and 7b closing opposite ends of the cylinder block 4 to form a compression chamber a and supporting the crankshaft. The support end plate 7a has a hole 8 for discharging the coolant from the compression chamber a to the space inside the casing. The valve plate 9 mounted on the support end plate 7a has a free end 9a for opening and closing the discharge hole 8. The leaf spring 10 is placed on and fixed to the valve plate and has a free end 10a for pressing the free end 9a of the valve plate towards the closed position. The valve retainer 11 fixes the opposite ends of the valve plate 9 and the leaf spring 10 to the support end plate 7a with bolts 12 (as shown in fig. 3). The leaf spring is bent at the middle 10b to generate a biasing force.

In operation, when the motor 2 is started, the crankshaft 5 is driven to rotate the eccentrically mounted pistons 6 and compress the coolant vapor in the cylinder block 4 as the volume of the compression chamber a changes. When the pressure in the compression chamber exceeds the sum of the pressure in the closed casing 1 and the biasing force of the leaf spring 10, the free ends of the valve plate 9 and the leaf spring deflect upward, opening the discharge hole 8, allowing the compressed coolant vapor to be discharged into the closed casing.

By varying the thickness or shape of the leaf spring 10 relative to the valve plate 9 or a combination of both, the natural frequencies of the leaf spring and the valve plate can be varied to reduce noise generated by frictional damping forces between the contact surfaces of the two.

With the above-described conventional coolant discharge valve structure, the opening time of the coolant discharge hole is delayed by a time interval due to the resistance exerted by the leaf spring. The pressure in the cylinder block 4 is thus higher than the pressure in the housing, resulting in the generation of a so-called "super valve", requiring additional driving power, reducing the efficiency of the compressor.

In view of the above-mentioned drawbacks of the prior art discharge valves, it is an object of the present invention to provide a coolant discharge valve which can improve the efficiency of a compressor, reduce operation noise, require no additional power, and do not generate "overshoots".

The object of the invention is achieved by a coolant discharge valve comprising a leaf spring biasing a valve plate, the leaf spring having a deflection portion generating a biasing force, but wherein the spring presses against a middle region of the valve plate, and the free end of the valve plate is not subjected to any spring force at the beginning of the opening of the coolant discharge orifice. This structure can reduce the delay of the opening time of the discharge hole at the free end of the valve sheet.

Fig. 1 is an axial sectional view of a general refrigeration compressor equipped with a discharge valve;

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1;

FIG. 3 is an enlarged cross-sectional view taken along line III-III of FIG. 2;

FIG. 4 is an exploded cross-sectional view of the coolant discharge valve of FIG. 3;

Fig. 5 is an enlarged cross-sectional view of a discharge valve of a refrigerant compressor according to the present invention;

FIG. 6 is an exploded cross-sectional view of the discharge valve shown in FIG. 5;

FIGS. 7 (A), 7 (B) and 7 (C) are graphical illustrations of the degree of deflection of the discharge valve plates of the present invention compared to the prior art;

fig. 8 and 9 are perspective views of leaf spring structures according to other embodiments of the present invention.

Fig. 5 to 7 show a coolant discharge valve according to a first embodiment of the present invention, in which a support end plate 7a has a conventional coolant discharge hole 8, and a valve plate 9 mounted on the end plate 7a has a free end 9a for opening and closing the discharge hole. The leaf spring 10 is arranged above the valve plate 9. The valve retainer 11 secures the valve plate and the opposite ends of the leaf spring to the end plate 7a with a bolt 12 (shown in fig. 5). The leaf spring has a free end 10a with a bent down portion at a mid-position 10b between the fixed and free ends. The curved portion has a pressing point 10c which presses it down against the end plate 7a at an intermediate position of the valve plate 9. When assembled as in fig. 5, the free ends 10a of the leaf springs bear against the lower surface of the valve retainer 11. Therefore, there is no spring force on the free end 9a of the valve plate, at least when the coolant discharge opening 8 is initially opened.

With this structure, the deflection of the valve plate 9 when the compressed coolant is discharged will vary from the three regions 51 to 33 (shown by solid lines in fig. 7 (C)) according to the magnitude of the air pressure of the compressed coolant as shown in fig. 7 (C).

When the pressure in the compression chamber a is equal to the pressure in the casing 1, i.e. when the air pressure f=0 of the compressed coolant, the valve plate 9 starts to deflect. In the region 51, the valve plate deflects without any biasing force of the leaf spring 10, as shown in figure (a). Subsequently, in the region 52 (condition of the part is shown as 7 (B)), the biasing force of the leaf spring acts on the valve plate, and the rate of deflection of the valve plate decreases as the coolant gas pressure increases. More specifically, the force of the leaf spring 10 acts on the valve plate 9 through the bent portion thereof. When the valve plate begins to deflect, no spring force acts on its free end 9a.

On conventional discharge valves, the valve plate is always biased by a leaf spring until the air pressure f=f of the compressed coolant. Deflection is initiated only when (as shown by the dashed line in fig. 7 (c)). The valve plate of the discharge valve of the present invention is not so often biased and therefore opens a bit earlier, thereby reducing or substantially eliminating "overshooting" of the opening pressure and concomitantly reducing the driving power of the compressor. Since no spring force acts on the free end of the valve plate when the valve plate starts to deflect, the flow rate of the coolant through the discharge hole is reduced, and thus noise caused by the coolant flowing through the discharge hole is also reduced. Since the free end of the leaf spring is pressed against the valve holder 11 and its pressing point 10c is pressed against the valve plate, it can reduce noise caused by frictional damping force generated at the contact point in the conventional structure.

The deflection portion of the spring in the previous embodiment includes a vertically curved intermediate step, but may also include a U-shaped slot as shown in fig. 8, or a rounded protrusion as shown in fig. 9. Also, the portion of the leaf spring extending from the pressure point 10c to the free end 10a may simply be omitted or eliminated, depending on the deflection characteristics of the particular spring used.

Claims

1. A discharge valve for a refrigeration compressor including a compression chamber a defined by an end plate 7 _a having a coolant discharge port 8, the discharge valve comprising:

(a) An elongated deformable valve plate 9 mounted to the end plate and having a free end 9 _a for placement over the discharge orifice to open and close the orifice,

(B) An elongated leaf spring 10 disposed above the valve plate,

(C) An elongated valve retainer 11 placed over the leaf spring,

(D) The valve holder 11 fixes the opposite ends of the valve plate 9 and the leaf spring 10 to the support plate 7 _a with bolts 12,

It is characterized in that the method comprises the steps of,

(E) The retainer is structured to form a space above the discharge orifice for the valve plate to deflect on and off, and

(F) A linearly biased deformation defined in the leaf spring in the space between the clamping end and the free end of the leaf to press the leaf toward the end plate to the closed position by a point located a distance from the discharge orifice between the discharge orifice and the clamping end of the leaf, while at the same time preventing deflection of the free end of the leaf upon initial opening of the discharge orifice, without contact between the leaf spring and the leaf adjacent the free end of the leaf and the discharge orifice, and with the leaf spring being displaced from the segment of the leaf between the clamping end and the point at which the spring is pressed.

2. The discharge valve of claim 1, wherein a free end of the leaf spring extends past the deformation portion and against a lower surface of the valve retainer above the discharge orifice.

3. The discharge valve of claim 2, wherein the spring deformation portion includes a stepped portion bent downward.

4. The discharge valve of claim 2, wherein the spring deflection portion includes a downwardly directed U-shaped slot.

5. The discharge valve of claim 2, wherein the spring deformation portion comprises a circular protrusion in a downward direction.

6. The discharge valve of claim 1, wherein the solid portion of the end plate supportingly contacts the valve plate at a pressing point below the valve plate.