KR20050035082A - Reciprocating compressor and manufacturing method thereof - Google Patents

Abstract

In a reciprocating compressor provided with a spherical support of a piston connected to a spherical member of a piston rod, a compressor with high compression efficiency is produced in a short time by improving the processing accuracy of the spherical support of a piston.

A spherical surface having a cylinder, a piston rod, and a piston reciprocating in the cylinder, the piston rod having a spherical member coupling connected to the piston, and the piston having a curved surface in contact with the spherical member coupling of the piston rod. It is assumed that the curved surface of the spherical support portion has a support portion, and the sintered metal which has not been subjected to the water vapor treatment is subjected to mechanical processing and then subjected to water vapor treatment.

At this time, the initial processing is performed before the steam treatment, and it is better to perform the finish processing by machining after the steam treatment.

Description

Reciprocating compressor and its manufacturing method {RECIPROCATING COMPRESSOR AND MANUFACTURING METHOD THEREOF}

The present invention mainly relates to a reciprocating compressor used in an air conditioning apparatus and a refrigeration apparatus.

BACKGROUND ART A reciprocating compressor having a structure in which a piston and a piston rod are connected by spherical coupling has been conventionally used in inclined plate compressors for car air conditioners and hermetic compressors for refrigerators.

As one of such compressors, there is a technique described in Patent Document 1.

Japanese Patent Application Laid-Open No. 5-209588 has a piston rod having a portion connected to a piston as a spherical member, and a piston having a spherical support portion connected to a spherical member of the piston rod, wherein the piston is formed into a metal powder. It is described that if the post-sintered sintered alloy is subjected to steam treatment and manufactured, the pores unique to the sintered alloy can be sealed to improve wear resistance.

In addition, it is described that grinding can be performed on the outer circumferential surface serving as the follower of the piston to remove the oxide film, whereby stabilization of the dimension can be attained, while holes unique to the sintered alloy can be built up to allow lubricating oil penetration.

Further, Japanese Laid-Open Patent Publication No. 2003-3956 describes a spherical support portion made of an iron-based sintered alloy in which the diameter of the opening portion is smaller than the diameter of the spherical member of the piston rod.

In the prior art, the process of steam treatment and the process sequence of machining have not been considered in terms of processing precision and processing time.

Iron-based sintered metal is a material obtained by compressing and molding metal powder in a mold, and then heating and joining the metal powders together, but the metal powders do not completely fuse together because the metal powder is not heated until the molten state in the manufacturing process. Do not. Therefore, since holes exist between the metal powders, there is little ductility. Therefore, when plastic deformation of the sintered metal is brittle, the opening diameter of the spherical base portion is smaller than the maximum diameter of the spherical surface, i.e., the opening direction as shown in Fig. 6 of Patent Document 1 and Fig. 1 of Patent Document 2. In the case of making a reduced shape, it was difficult to mold by plastic deformation.

In addition, when it is desired to shape the desired shape by sintering with a general mold, it is necessary to make the opening diameter of the spherical base portion equal to or larger than the maximum diameter of the spherical surface as shown in FIG.

However, in such a shape, there is a possibility that the spherical member of the piston rod deviates from the spherical support.

Thus, a method of realizing a reciprocating compressor provided with a spherical support made of sintered metal covering the side close to the crankshaft of the spherical member of the piston rod without plastic deformation is conceivable.

As the method, the present inventors formed a spherical surface by machining a hole of a pillar member in a sintered metal, and then forming a spherical surface by machining such as lathe cutting, and forming a two-sided width in which the spherical member was removed to reduce the width. It was assumed that a method of inserting a spherical member into the spherical support was made by using the two surface widths of the spherical support and the spherical member.

In performing these machinings, the inventors of the present invention have conceived of performing steam treatment without machining after sintering the alloy, and then performing machining.

However, when the compressor provided with the spherical member support part manufactured by this method was evaluated, the manufacturing time is very long and the abrasion in the relief surface of a cutting bite is severe. Therefore, it turns out that the processed curved surface of a spherical member support part may become rough, and the movement of a piston rod may deteriorate and the compression efficiency may fall.

In addition, although the leakage of the compressed gas from the cylinder generated by the above-mentioned hole was prevented by the oxide formed by the steam treatment, when the cutting amount was increased, the sufficiently oxidized layer was removed, and the compressed gas leaked by the above-mentioned hole This tends to occur and the compression efficiency may fall.

That is, an object of the present invention is to solve these problems and to smoothly move the piston rod, thereby improving the compression efficiency of the reciprocating compressor.

This application includes a plurality of methods for solving the above problems, but typical ones are as follows.

As a solution of the present invention, before forming an oxide film on a spherical support as a piston connected to a piston rod of a reciprocating compressor, unnecessary parts are removed by machining such as cutting, and thereafter, steam treatment is performed. After that, finishing machining is performed as necessary.

By doing in this way, the roughness of the curved surface accompanying a process can be suppressed and the movement of a piston rod can be made smooth, and the compression efficiency of a compressor can be improved.

In addition, by machining once before the steam treatment, the oxide of the spherical support portion formed by the steam treatment, especially iron, can sufficiently leave a layer of iron trioxide (Fe ₃ O ₄ ). Leakage of the compressed gas can be suppressed.

According to the present invention, the compression efficiency of the reciprocating compressor can be improved.

An embodiment of the invention according to the present invention will be described with reference to Figs.

1 is a longitudinal sectional view of one embodiment of a refrigeration reciprocating compressor.

The reciprocating compressor uses hydrocarbons such as isobutane as the refrigerant, and a motor and a compression mechanism driven by the motor are arranged inside the chamber 6 which is a sealed container.

The motor is provided with the stator 5a and the rotor 5b.

The crankshaft 4 is fastened to this rotor 5b.

The crankshaft 4 is arrange | positioned so that it may penetrate the inside of the bearing 2b which is a hole of fixed thickness formed in a part of the cylinder block 2, and it is a structure which rotates with the rotation of the rotor 5b.

The crankshaft 4 is provided with the eccentric pin 4a, and is structured to rotate with the rotation of the rotor 5b.

A piston rod 3 extending laterally with respect to the axis of the crankshaft is connected to the pin 4a.

The piston 1 is connected to the end part adjacent to the cylinder of the piston rod 3.

The piston 1 is supported by the cylinder 2a, and the rotational movement of the crankshaft passes through the piston rod, thereby converting the rotation of the rotor 5b into a linear reciprocating motion approximately coincident with the reciprocating path of the piston and have.

In addition, a valve mechanism 7 having a valve for controlling the inflow and out of the refrigerant in the cylinder 2a is held on the end face of the cylinder 2a that is not adjacent to the piston rod, and the valve mechanism 7 The silencer 8 which reduces the noise of the refrigerant discharged by compression is attached.

Lubricant is stored in the lower part of the chamber 6, and it is sucked up from the lower end of the crankshaft 4 and slides in the crankshaft 4, the piston rod 3, the cylinder block 2, and the piston 1. The structure lubricates the part.

In the example of this embodiment, the spherical coupling is used for the connection of the piston 1 and the piston rod 3.

The structure of this spherical coupling is demonstrated using FIG.

FIG. 2 is a longitudinal sectional view of the piston 1 connecting the piston rod 3, and is an enlarged view of the connecting portion of the piston rod 3 and the piston 1 in the A-A cross section of FIG.

The cylinder side end portion of the piston rod 3 is reduced in diameter (a smaller cross-sectional area) in order to prevent portions other than the spherical members of the piston rod 3 from contacting the spherical support. Moreover, the spherical member 3a is formed in the front-end | tip part.

The piston 1 is provided with the spherical support part 1a which comprises the space of the substantially spherical member provided with the opening part wider than the movement range of the rod-shaped part of the piston rod 3.

The spherical member 3a is formed with two planes in the direction of the normal line of the sheet of Fig. 2, and can be inserted or separated from each other using these two surfaces.

The piston 1 is made by iron-based sintered metal sintered from a material containing iron, and produced by steam treatment after machining the spherical support 1a and the outer circumferential surface 1b by machining. .

The machining procedure of this machining and steam treatment is not only to clean the surface of the surface by reducing tool wear when the iron-based sintered metal is machined, but also to the oxide film of the sintered metal produced by the steam treatment, in the present embodiment. Since the amount of trioxide trioxide can be increased, the compression efficiency of the compressor can be improved.

This process and tool wear will be described with reference to FIGS. 3 and 4.

3 shows a process set in order to obtain the piston 1 efficiently.

3 shows a flow of a process of manufacturing the piston 1 as an example of this embodiment.

In this step, first, a raw material powder is produced with a desired composition (step No. 1), and this raw material powder is filled with a mold together with a sub raw material powder such as a binder and pressed to obtain a molded product (step No. 2).

Subsequently, the molded body is heated in an atmosphere to sinter to diffuse-bond the metal powder to obtain a sintered body (step 3).

Next, after sintering, the cylindrical spherical support 1a, which was cylindrical in shape, was first processed into a lathe to be spherical (step No. 4), and then similarly, the lathe was used, or a grinding plate was used for the spherical support 1a. Machining is performed to finish with dimensions and precision (process number 5).

As shown in Fig. 3 (b), the spherical support 1a was cylindrical after sintering (step 3) due to the constraints of the mold, but after machining of the spherical support part (step 5), It forms a sphere.

Subsequently, in the process shown by process number 6 of FIG. 1A, the cylindrical outer peripheral surface 1b is processed into a cylindrical grinding machine or a centerless grinding machine. This processing is performed for the purpose of correcting the surface roughness, shape (cylindrical degree) and dimensions of the sintered compact.

Thereafter, when burrs are formed by machining, burrs are removed by brush or the like containing grindstone powder (Step No. 7).

At this stage, the machining for the purpose of forming the shape is completed, and then subjected to steam treatment (Step No. 8). In this steam treatment, first, the processing liquid and the oil adhered by machining are sufficiently removed by washing. Next, it is kept for about 1 hour in steam heated to 500 to 600 degreeC. By this treatment, iron in contact with water vapor is oxidized to black iron trioxide (Fe ₃ O ₄ ) to form an oxide film on the surface of the piston (1).

Here, as an example, the piston 1 is completed as a component, and is assembled by a compressor via the process of the branch B shown after the process number 8 of FIG.3 (a).

In the above-mentioned process, the characteristic of this embodiment is that the machining is performed before the steam treatment.

In the case where the steam treatment is performed after machining, it is necessary to carefully remove the processing liquid and the like attached by machining, but it has been found by experiment that the wear of the machining tool can be reduced by machining.

4 is a graph showing an example of a wear test result of a machining tool in comparison with a sintered material produced in a conventional process and a sintered material produced in the above-described process. The experimental conditions for obtaining the results shown in FIG. 4 are shown in the table of FIG. 7. The sintered material used for the test consists of 0.7-1.0% of carbon (C), 1-2% of copper, and the remainder consists of iron (Fe), and corresponds to SMF4040 by JIS standards. The sintered metal was subjected to steam treatment and was not used for the test. The tool used was not for the lathe to machine the piston 1, but an end mill was used to easily observe wear. The area where the wear was observed was the bottom face of the end mill, and the wear width of the relief face was examined. The diameter of the used end mill was 12 mm, and the number of blades was 6 sheets. As for the processing conditions, the end mill rotation speed was 5000 min <^-1> , the feed speed was 600 mm / min, and 0.05 mm of cuts were provided to the bottom edge, and the end surface of the test material was processed. 4 is a graph showing the resulting machined distance and wear width of the maximum relief surface of the tool.

There is no difference in the wear width of the maximum relief surface at a machining distance of 1.2 m in the initial stage of machining start. However, in the case of sintered metal subjected to steam treatment up to a step of 6 m working distance, the maximum relief surface wear width rapidly increased to 270 µm, and the glowing cutting powder began to be produced from the processing point, and the continuous processing continued. It became difficult. On the other hand, in the case of the sintered metal which was not subjected to the steam treatment, normal wear progressed, and the maximum relief surface wear width was 60 µm at a machining distance of 6 m and 120 µm at a machining distance of 11 m. When compared with the viewpoint of 6 m of processing distances, when processing the sintered metal which does not perform steam treatment, the maximum relief surface wear width can be reduced by 78% compared with the case where the sintered metal which performed the conventional steam treatment was processed. In other words, the tool wear can be about 1/5. According to this result, the process of completing the machining before performing the steam treatment on the piston 1 makes it possible to extend the tool life and improve the production efficiency. In addition, since there is little change in the shape of the tool, it can be processed under constant conditions, and a uniform and smooth processing surface can be obtained.

In addition, the surface layer portion of the triiron tetraoxide (Fe ₃ O ₄₎ is triiron tetraoxide (Fe ₃ O ₄₎ by steam treatment after this, while the machining function of improving the wear resistance by preventing adhesion between the metal because it is an oxide formed by steam treatment completely Remaining. Therefore, there is also an effect of improving the wear resistance of the piston 1. In addition, since the surface layer portion of iron trioxide (Fe ₃ O ₄ ) remains completely, the pores in the sintered metal are not exposed, and the airtightness of the piston 1 is also improved.

The large effect of suppressing the above-described tool wear is the spherical support part priming (step number 4) shown in FIG. Although it is effective also in outer peripheral surface processing (process number 6), this process aims at correcting the dimensional precision and cylindricality not reached by sintering (process number 3), and is not a process which produces a shape. In general, since the removal value is about 0.1 mm, the wear of the tool to be used is also smaller than that of the spherical base portion forming process (process number 4), which makes a sphere. Therefore, the above-described process is particularly effective for spherical support part machining (step No. 4), and the efficiency of the spherical support part first machining (step No. 4), which is difficult to obtain satisfactory spherical precision when the tool is worn, is improved. Great effect

Although the process has such an advantage, the iron trioxide (Fe ₃ O ₄ ) formed on the surface is rough crystals to increase the surface roughness of the machined surface. Therefore, in the case of the high precision specification in which the piston 1 sets the micro fitting gap with the cylinder 2 or the piston rod 3, fitting may become difficult by the increase of surface roughness. In such a case, after the steam treatment, the surface layer portion is removed so as to reduce the surface layer portion of iron trioxide (Fe3O4), and the surface is smoothed. If the removal value of 0.01 mm or less is processed by tape wrap, brush processing, etc., the objective can be achieved. Since the layer of iron trioxide (Fe ₃ O ₄ ) has a thickness of 0.05 mm or more, the layer of iron trioxide (Fe ₃ O ₄ ) remains completely even when the surface layer portion is removed by about 0.01 mm. This process first finishes the outer circumferential surface in order to smooth the surface after steaming after machining to form a shape or dimension in the process indicated by the branch C of the process diagram shown in Fig. 3A. 8A), and then the spherical surface finishing part 2 (process number 8B) is performed. Thereafter, the surface is smoothed by performing the assembly, so that the assembly can be performed smoothly.

In the case where branch C is selected, machining is performed after the steam treatment (Step No. 8). However, since this step is intended to smooth the surface, the removal value is very small at 0.01 mm as described above. Therefore, the increase in tool wear by the steam treatment (process number 8) can be stopped at a level that does not need to be considered.

Since the piston 1 which has undergone the above-described process is excellent in abrasion resistance, it is necessary to interpose a material for improving abrasion resistance of resin or the like between the spherical support 1a of the piston 1 and the piston rod 3a. none. Therefore, as shown in Fig. 5A, the dimension H1 from the bearing portion of the piston rod 3 to the upper surface of the piston in the state of assembling the piston 1 and the piston rod 3 is accurately machined. It is possible to get by. The piston 1 and the piston rod 3 can be assembled to the cylinder block 2 in which the cylinder portion 2a and the bearing portion 2b are integrated in a state where both of them are assembled. The dimension H2 from the bearing center of the cylinder block 2 to the upper cylinder surface is determined by machining, but the dimension H1 from the bearing portion of the piston rod 3 to the piston upper surface is also accurately machined. It can be determined and there is no need to adjust the position during assembly. In the structure in which a material such as resin is interposed between the conventional spherical support 1a and the piston rod 3a, it is difficult to precisely measure the dimension corresponding to H1. . Therefore, the cylinders had to be of different parts to adjust their position relative to the piston. In connection with this, although the operation | work which adjusts a cylinder at the time of assembly | assembly, and the bolt and a bolt hole for fixing a cylinder were needed, these operations are unnecessary in the integrated cylinder block 2, and it becomes possible to improve the efficiency of production. In the conventional method of fixing a cylinder by an assembling process, there is also a problem in that the cylinder is deformed due to stress being applied by fastening with a bolt or the like. However, in the integral cylinder block 2, deformation of the cylinder portion 2a generated during assembly is performed. Problems can also be solved.

Fig. 6 is an example in which a recess is provided at a position including a top point of the spherical base in this embodiment.

In processing the spherical support 1a into a lathe, the piston 1 is rotated about the axis S to be processed into a bite. However, since the surface of the spherical support 1a has a circular cross section, the axis S is Distance from location varies. Therefore, when the piston 1 is processed while rotating the piston 1 at a predetermined rotational speed, the processing speed is changed. Therefore, the control of increasing or decreasing the rotational speed can be taken in accordance with the distance from the axis S of the portion to be processed. However, since the top point portion of the spherical base 1a is on the line of the axis S, and the distance from the axis S is zero, the cutting speed is zero regardless of the number of rotations to be given in this portion. Therefore, the vicinity of the top point of the spherical base portion 1a is a portion where machining accuracy tends to deteriorate. On the other hand, the vicinity of the top point of the spherical support is the portion that receives the most load from the piston, and if the vicinity of the top point is processed into a protruding shape, the surface pressure increases during the sliding movement of the piston rod with the spherical member 3a, which causes abnormal wear Cause.

The recessed part 1d is provided for the purpose of relief not to process in the process which makes this top part part into the spherical support part 1a. As an example, the recessed portion 1d of the peak portion can be provided by drilling after sintering (step 3) in the process diagram of Fig. 3A. Moreover, this recessed part 1d can also be shape | molded by a metal mold | die by shaping | molding (process number 2), and even if a mold becomes complicated, the recessed part 1d is molded by a metal mold | die, and the efficiency of production You can do it nicely. Since this recessed part 1d is a so-called relief provided in order not to process near a normal point in the process of the spherical support part 1a, the shape does not matter, but the area of the spherical support part 1c by the recessed part 1d. Decreases. Since the vicinity of the top point is the portion where the spherical bearing portion is most loaded, the area where the recessed portion 1d is opened in the spherical bearing portion 1a needs to be determined according to the intended use. However, it is preferable to keep the opening area of the recessed portion 1d as necessary.

In this way, the piston 1 excellent in wear resistance can be obtained efficiently, but in the compressor in which the piston 1 is assembled, the durability of the piston can be improved at low cost. In addition, from the viewpoint of global environmental protection, a switch is made from a prone containing chlorine, which is conventionally used as a refrigerant, to a prone containing no chlorine, or a natural refrigerant such as carbon dioxide or hydrocarbon. Compacting does not contain refrigerant these chlorine, in due to the lower friction reduction action of the coolant itself is easy to become a boundary lubrication condition, triiron tetraoxide (Fe ₃ O _4), a piston (1), which forms a surface oxide between the metal Since the contact is prevented, the wear resistance is improved even under boundary lubrication. Therefore, the refrigerant compressor employing the piston 1 is advantageous in terms of durability even in application to a refrigerant containing no chlorine.

By smoothly moving the piston rod, the compression efficiency of the reciprocating compressor is improved.

1 is a longitudinal sectional view showing a compressor which is an example of an embodiment of the present invention.

2 is a longitudinal sectional view showing a state in which a piston and a piston rod are engaged;

3 is an explanatory view showing a machining step of a piston which is an example of an embodiment of the present invention, and a longitudinal cross-sectional view of the piston;

Fig. 4 is a diagram showing an example of tool wear when the sintered metal is machined by the wear width of the relief surface.

5 is a bird's eye view showing the appearance of a piston, a piston rod, and a cylinder block;

Fig. 6 is a longitudinal sectional view of the piston showing a recess provided at the top of the spherical support;

7 is a table showing the conditions of the experiment obtained the results shown in FIG.

<Explanation of symbols for the main parts of the drawings>

1: piston

1a: spherical support

2: cylinder block

2a: cylinder

3: piston rod

3a: spherical member

4: Crankshaft

4a: pin

6: chamber

7: valve mechanism

Claims (9)

A cylinder, a piston rod, and a piston reciprocating in the cylinder, The piston rod has a spherical member coupling connected to the piston, The piston has a spherical support having a curved surface in contact with the spherical member coupling of the piston rod, and the curved surface of the spherical bearing is machined to a sintered metal not subjected to steam treatment, after which a steam treatment is performed. Reciprocating compressor characterized in that. The reciprocating compressor according to claim 1, wherein the curved surface of the curved support portion is machined again after the steam treatment. According to claim 1, having a crankshaft for driving the piston rod, and a frame for supporting the crankshaft, The frame is a reciprocating compressor, characterized in that the piston is formed integrally with the cylinder reciprocating in the cylinder. According to claim 2, having a crankshaft for driving the piston rod, and a frame for supporting the crankshaft, The frame is a reciprocating compressor, characterized in that the piston is formed integrally with the cylinder reciprocating in the cylinder. The reciprocating compressor according to any one of claims 1 to 4, which is used for compressing a refrigerant containing no chlorine powder. A method of manufacturing a reciprocating compressor in which a piston connected to a spherical coupling of a piston rod in a cylinder reciprocates in the cylinder, The curved surface of the spherical base of the piston is formed by machining on a sintered metal not subjected to steam treatment. A method of producing a reciprocating compressor, characterized by performing steam treatment on the curved surface after the machining. The method of manufacturing a reciprocating compressor according to claim 6, wherein the steam treatment is performed and then machined again. The method of manufacturing a reciprocating compressor according to claim 6 or 7, wherein a recess is formed before machining the spherical support in the vicinity of the head surface side top point of the spherical support of the piston. The concave portion according to claim 8, further comprising a concave portion near a head surface side top point of the spherical support of the piston, A method of manufacturing a reciprocating compressor, characterized in that for forming the recess into a mold.