HK1116847A - Compressor connecting rod bearing design - Google Patents

Description

Compressor connecting rod bearing design

Technical Field

[0001] The present invention relates to an improved compressor tie rod design for providing maximum surface area at the "big end" bearing that transmits the driving force to the piston while allowing pressurized lubrication to the "small end" or "piston pin bearing".

Background

[0002] Compressors are used in most applications to compress various fluids. One type of compressor is a reciprocating piston compressor. In a reciprocating piston compressor, a drive shaft rotates at least one eccentric. Each eccentric in turn drives a connecting rod, i.e. a piston connected by a piston pin. The connecting rod has a "big end" bearing, also typically housed on the eccentric. The opposite end of the connecting rod has a "small end" bearing which is typically received on a wrist pin, i.e., in turn received in the piston.

[0003] In these connecting rod bearings, a large amount of friction is encountered in transmitting the driving force to the piston. Thus, in the known prior art, lubricating oil is provided to the various moving surfaces in the compressor in order to facilitate movement of the piston and connecting rod. Typically, lubricating oil is forced into the lubricating oil channels inside the main shaft, which is distributed into the delivery holes for the eccentrics and the main bearings. This oil may also be communicated up through the tie rod to the "small end" bearings to lubricate the wrist pin and corresponding piston bearings.

[0004] The general construction of the connecting rod is a member formed by combining an upper half and a lower half, and then bolted or otherwise fixed to the eccentric to constitute a big end bearing. The prior art has used two main types of this big end bearing geometry. In the first type, there are no oil grooves at the bearing surface. In the second type, there is an oil groove around the full 360 degrees at the inner circumference of the bearing surface. In conjunction with these bearing designs, an oil lubrication passage is typically provided that extends up through the connecting rod to the small end bearing. In the first type of big-end bearing, the prior art sometimes does not provide sufficient lubrication to the small-end bearing surface. In a second type of big end bearing design, a more sufficient amount of lubrication oil is provided for the small end bearing.

[0005] Frequently, these big-end bearings are configured for use in a connecting rod with a "shell bearing" inserted into the big-end bearing. While the second big-end bearing design provides a more adequate and adequate lubrication flow, it still has its own drawbacks. In particular, the inner peripheral surface of the upper half of the bearing surface is a force transmitting surface for transmitting a force from the eccentric to the connecting rod. The oil grooves in these surfaces reduce the available area to support the oil film and result in a reduced film thickness that may be too thin to allow separation of the bearing and eccentric surfaces.

[0006] It would be desirable to overcome the deficiencies of the prior art as described above.

Disclosure of Invention

[0007] In the disclosed embodiment, the connecting rod has a big end bearing with an oil supply groove through at least most of its lower half and little or no oil supply groove in its upper half. In this way, there is still sufficient lubrication oil provided up through the connecting rod to the small end bearing surface, while the large end bearing surface for force transmission is still maximized.

[0008] In one embodiment, instead of using a shell bearing, the groove is formed across the entire extent of the big end bearing surface of the lower half. The grooves communicate the lubricating oil to a passage extending through the upper half. The passage does not communicate with the inner peripheral surface of the upper-half large-end bearing surface. Thus, the bearing surface area is maximized in the upper half thereof.

[0009] In another embodiment, and one embodiment using a shell bearing, the terminal circumferential end of the bearing shell has a groove for allowing lubricating oil to flow into the shell radially outwardly. The groove is connected to a passage extending upwardly through the connecting rod to the small end bearing.

[0010] These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

Drawings

[0011] Fig. 1 shows a prior art compressor.

[0012] Figure 2A shows one prior art embodiment.

[0013] Fig. 2B shows another embodiment of the prior art.

[0014] Fig. 3 shows a first embodiment.

[0015] Fig. 4 is a cross-sectional view through a portion of the embodiment of fig. 3.

[0016] Fig. 5 shows the lower bearing portion of the first embodiment.

[0017] Fig. 6 shows a second embodiment.

[0018] Fig. 7 is a cross-sectional view through the embodiment of fig. 6.

Detailed Description

[0019] The prior art compressor 20 as shown in fig. 1 has a motor 22 including a stator 24. The stator 24 causes the rotor 23 to rotate and drive the driveshaft 25. As shown, the end 26 of the driveshaft 25 is mounted to a bearing. The eccentric 28 on the drive shaft drives a connecting rod 30. The connecting rod 30 has a "large end" received on the eccentric 28, and a "small end" received on the piston 32. The piston 32 moves toward or away from the valve plate 34 to compress the coolant. Oil sump 36 delivers oil through passage 100 to oil pump 101 and to passage 102 extending through shaft 25.

[0020] As shown in FIG. 2A, in one embodiment of the prior art, a portion of the oil is drawn into the channel 38 through the connecting rod 30. The connecting rod 30 is composed of a lower half 37 and an upper half 39. The two halves 37 and 39 are bolted together on the eccentric 28, as is known. The inner circumferential bearing surface 40 of the bearing surfaces 40 of the two halves 37 and 39 is free of any oil grooves. Conversely, oil exiting the passage 102 will be diverted into the passage 38 and move upward toward the small end bearing 35, in turn lubricating the crosshead pin bearing surfaces.

[0021] Fig. 2B shows another embodiment of the prior art, in which the housing bearing halves 41 are both disposed inside the lower and upper halves 37 and 39. Grooves 42 are formed in the interior of the two housing bearing halves 41 and communicate with the passage 38 through at least one opening in the housing bearing 41 in the upper half 39.

[0022] Generally, the embodiment of fig. 2A does not always provide sufficient lubrication, and the embodiment of fig. 2B has the problem of reducing the effective surface area on the bearing surface 40 of the upper half 39. Receiving a force transmitted from the eccentric 28 on the surface to drive the connecting rod 30 and piston 32 toward the valve plate 34. The reduction in the surface area of the groove 42 is undesirable and requires a reduction in the oil film thickness to separate the bearing surface 40 from the eccentric 28.

[0023] Fig. 3 shows an inventive tie rod embodiment 50. The upper half 52 is formed inside an inner circumferential bearing surface 56 without any oil groove. The lower half 53 includes a groove 54 extending along the entire circumferential extent.

[0024] As shown in FIG. 4, an opening 58 in the lower end of the upper half 52 of the connecting rod 50 receives lubricating oil from the end of the groove 54. The end 58 communicates the oil into a passage 57 extending upwardly toward the small end 35 of the connecting rod 50.

[0025] As described above, the inner circumference 55 of the lower half 53 includes the groove 54. As best seen in FIG. 5, a communication opening 59 in the lower half 53 is also shown, the communication opening 59 communicating with the lubricant inlet opening 58. The first embodiment thus provides sufficient oil flow to the small end 35 of the connecting rod 50, but also maximizes the surface area of the inner circumference 56 of the upper half 52.

[0026] Fig. 6 shows another embodiment 70, and as with the previous embodiment, the upper half 72 of the connecting rod 70 is secured to the lower half 74. The groove 76 is also formed in the housing bearing 80 of the lower half 74. The opening 78 is formed at the end of a housing bearing 82 mounted inside the upper half 72.

[0027] As shown in FIG. 7, a small opening 78 in the upper half 72 that extends through the housing bearing 82 communicates with a groove 79 formed in the nominal body of the upper half 72. The groove 79 communicates with an opening 86, which opening 86 in turn communicates with a passage 84 extending toward the small end 35 of the connecting rod 70. Although a small amount of surface area is lost due to the openings 78, it is preferred that the openings be disposed at the circumferential ends of the upper half 72 and thus not directly in the force transfer direction. Furthermore, the apertures 78 also result in an increased surface area for force transmission when compared to the prior art.

[0028] Although the present invention can be used in compressors to compress a variety of fluids, it is particularly applicable to refrigerant compressors and particularly to compressing carbon dioxide as a refrigerant.

[0029] Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims (11)

1. A compressor, comprising:

a motor for driving a rotating shaft, the rotating shaft driving at least one eccentric wheel;

a connecting rod connected to a first bearing surface about the eccentric, the first bearing surface including a lower connecting rod half and an upper connecting rod half, the upper connecting rod half extending toward a second bearing surface about a wrist pin connected to the piston;

the piston moves inside the cylinder to compress fluid;

an oil supply system for supplying lubricating oil to the connecting rod passing through the shaft; and

an oil groove formed in said lower tie rod half over at least a majority of a circumferential extent around an inner surface of said eccentric and no oil groove formed in said upper tie rod half over a majority of a circumferential extent around an inner surface of said eccentric, and a passage extending through said upper tie rod half to deliver lubricating oil to said second bearing surface surrounding said wrist pin associated with said piston.

2. The compressor of claim 1, wherein there are a plurality of said eccentrics, a plurality of said connecting rods, a plurality of said wrist pins, and a plurality of said pistons driven by said rotating shaft.

3. The compressor of claim 1, wherein said upper and lower tie rod halves are bolted together.

4. The compressor of claim 1, wherein said oil sump on said inner surface of said lower tie rod half communicates with a lubricant inlet opening, said opening communicating lubricant into said passage through said upper tie rod half.

5. The compressor of claim 4, wherein said passage through said upper tie rod half is formed on one side of said inner surface of said upper tie rod half such that said passage does not extend into said inner surface.

6. The compressor of claim 1, wherein said upper tie rod half houses a bearing bushing.

7. The compressor of claim 6, wherein said lower tie half further receives a bearing bushing to define said inner surface, said bearing bushing at said lower tie half including a circumferentially extending oil groove.

8. The compressor of claim 6, wherein an oil sump is formed in the upper tie rod half radially outward of the bearing bushing.

9. The compressor of claim 8, wherein an oil supply hole is formed through the bearing bushing of the upper tie rod half at a location of a small circumferential space.

10. The compressor of claim 9, wherein said small apertures are formed at circumferential ends of said bearing cartridge.

11. The compressor of claim 1, wherein the working fluid is carbon dioxide (CO)₂)。