FR2770591A1 - SHOE FOR COMPRESSOR WITH BEATER TRAY AND METHOD FOR MANUFACTURING THE SHOE - Google Patents

Abstract

A hemispherical shoe (10) for use in a beater stage compressor is described, which comprises a convex spherical surface (14) intended to engage against a spherical seat (4b) of a piston (4), and a flat surface (18) intended to come into sliding contact with a beater plate (2), the shoe (10) being cemented by nitriding.

Description

FIELD OF THE INVENTION

  The present invention relates to a shoe for a beater plate compressor used in an air conditioner

automobile or the like.

  The invention also relates to a method of

brication of this hoof.

DESCRIPTION OF THE PRIOR ART

  In a beater plate compressor, as shown briefly in FIG. 2, a rotary shaft 3 carries

  both a beater plate 2 is rotatably mounted in a

  pair of cylinder blocks 5a and 5b. In the blocks of cy-

  lindres 5a and 5b are formed a number of cylinder bores 5 circumferentially spaced by equal intervals, and a piston with two ends 4 is slidably inserted in each bore 5. In the central part of each piston 4 is formed a recess 4a intended to come astride the outer circumference of the beater plate 2, a spherical seat 4b being formed in each of the axially opposite surfaces of the recess 4a. A shoe 1, housed in the spherical seat 4b, is interposed between the beater plate 2 and the piston 4 to transform the rotational movement of the

  beater plate 2 in an alternating movement of the piston 4.

  Although the double action type has been shown using pistons with two ends, the constitution is also basically the same in the single action cylinder. The shoe 1, which is generally hemispherical, engages by its spherical surface against the spherical seat 4b of the piston 4, and is in sliding contact, by its flat bottom,

with the beater plate 2.

  Shoe 1 is formed by die forging at

  from a steel ball to obtain a hemispherical appearance

  that or similar to some sort of button. Shoe 1 is manufactured

  usually from a steel ball made of

  bearing steel (SUJ2 according to Japanese Industrial Stan-

  dart), by die forging processes (battering),

  equalization, grinding and pressing (Patent publications Ja-

  Poles No. 3-33419 and No. 7-24913).

  In the beater plate compressor, due to

  the rotation of the beater plate, the shoe is forced to come off

  place like a pestle in a mortar, which can produce local contact. In addition, the lubricating oil in this area, diluted with a coolant, is

  relatively ineffective in lubricating slippery parts

  your. The shoe must therefore work in an environment of very poor lubrication, which leads to seizure or other failure. In these circumstances, we need a hoof

  wear resistant and galling resistant.

  The present invention therefore aims to improve the wear resistance and the seizure resistance of the shoe for compressor with beater plate. The invention also

  aim of creating a method of manufacturing the shoe presented

so many such characteristics.

SUMMARY OF THE INVENTION

  The above goals are achieved, according to the invention.

  tion, by a shoe for a compressor with a beater plate

  as a nitrided surface, so as to form a layer

hardened to very high hardness.

  To this end, the present invention relates, in a first aspect, to a hemispherical shoe for a compressor with a beater plate, comprising a convex spherical surface intended to engage against the spherical seat of a piston,

  and a flat surface intended to come into sliding contact

  lying with a beater plate, characterized in that the shoe

is cemented by nitriding.

  According to another aspect of the invention, it

  relates to a method of manufacturing a shoe for a compress

  beater tray, characterized in that it comprises the steps consisting in giving a spherical shape to a blank

  made of steel for rolling bearings, by hand forging

  to grind the spherical steel material thus obtained, to cement the spherical steel material by nitriding, and

  to give the spherical steel material a hemispherical form

only by pressing.

  More specifically, in the manufacturing process

  cation, matrix forging, equalization, nitriding

  tion, softening, grinding, pressing, quenching and annealing, rolling, flat grinding and polishing

  plan, are carried out sequentially.

  The nitriding of the spherical material before giving it a hemispherical shape by pressing, advantageously reduces traces or marks of blows which would otherwise be

  produced in the following process. Nitriding can be carried out after giving the steel material a hemispherical shape, although nitriding the spherical material advantageously leads to a uniform hardened layer.

form.

BRIEF DESCRIPTION OF THE DRAWINGS

  The present invention will be described below in more detail using an embodiment

  presented in the accompanying drawings in which: - Figure 1 is a longitudinal sectional view of a shoe engaged against the spherical seat of a piston;

  - Figure 2 is a longitudinal sectional view of a

plate presser;

  - Figure 3 is a flowchart intended to explain the pro-

discontinued manufacturing;

  - Figures 4 to 8 are diagrams showing the re-

  test results; and - Figure 9 is a graph showing the results of

test.

  DESCRIPTION OF THE PREFERENTIAL EMBODIMENT

  FIG. 1 shows an example of the shape of a shoe 10. Obviously, the invention is not limited to the shoe having the shape shown in FIG. 1, but can be applied to any other shape. The shoe 10, which has a hemispherical appearance or similar to a kind of button, engages by its outer circumference 14 against a spherical seat 4b of a piston 4, while its flat bottom 18 is in sliding contact with a plate beater 2. The outer circumference 14 is a convex spherical surface having the same radius of curvature as the radius of curvature R1 of the spherical seat 4b. The outer circumference 14 and the

  bottom 18 meet each other smoothly and conti-

  naked. A recess can be formed in the central part of the bottom 18. The top 16 of the shoe is spaced from the spherical seat 4b so as to form a gap between the two. In the example illustrated, the vertex 16 consists of a partially spherical surface with a larger radius of curvature R2 than the radius of curvature Ri of the outer circumference

  14. As a variant, the vertex can be formed by cutting li-

  a part of the outer circumference of the convex spherical shape. In each case, the apex 16 and the outer circumference 14 preferably meet each other smoothly and continuously. Another recess

  can be formed in vertex 16.

  The shoe 10 is formed from a steel ball by matrix forging. The use of a steel ball made of hardened bearing steel (SUJ2) intended to be used in ball bearings, ensures mass production with high precision and

relatively low cost.

  We will now describe the manufacturing process

  as illustrated in figure 3. We give a rough material

  che a spherical shape by die forging in use

  sant a boutoir and, after equalization, the material is

  nitrided to form a hardened layer on its surface.

  The practical nitriding process can be any known process such as gas nitriding, liquid nitriding or ion nitriding. The nitrided material

  is subjected to annealing which is followed by grinding for effect

  kill a finish to obtain a steel ball of desired precision, and give the steel ball a

  hemispherical shape by pressing. Then, by quenching, cylin-

  drage, plan grinding and plan polishing, we get a product

  shoe as shown in Figure 1.

  To check the seizure resistance and the

  resistance to wear of the shoe 10 according to the invention, the effects

  of the surface treatment of the hoof on wear and rubbing-

  the hemispherical shoe and the beater plate used

  in the beater plate compressor for other air conditioner

  tomobile, have been examined by model tests in

  pure sliding conditions. As a test machine, we have

  defined the tip-on-disk type test machine to obtain

  nir a ball-on-disk type machine in which a

  steel ball was pressed vertically with a special weight

  cemented against an aluminum disc rotating at a specific speed, and we tested the effects of the presence or absence of surface treatment of the steel ball, on

  friction and wear. The disc material was a ma-

  high silicon-aluminum material A390 (17% Si, Al estimated standard) having undergone a soft finishing treatment. The testing machine is capable of increasing and decreasing the pressure in the chamber so as to perform

  tests under an atmosphere of pressurized refrigerant.

  After evacuating the chamber to 50 mmHg, chlorofluorocarbon replacement refrigerant gas was charged to the chamber to the pressure of 4 kgf / cm2, and the test was performed. At the oil concentration of 1%, the seizure resistance performance of the nitrided product was 15 times that of standard products, i.e. 1.5: 0.1 (min), and at the concentration of 2%,

  seizure resistance was 1.8 times higher,

  i.e. 4.5: 2.5 (min). To compare the amounts of wear or the rate of wear, we carried out the test in which we

  supplied enough oil not to pro-

  complain of seizure during the test. The results are indi-

  as in Table 1. The friction force was evaluated in terms of friction coefficient, the values being taken after an operating time of 10 minutes when the friction coefficient was stabilized. The amount of wear was assessed in terms of depth and

  width of the wear marks on the disc. The test was ef-

performed twice.

TABLE 1

  Depth Treatment Width Coefficient of wear surface um friction wear steel ball 30 minutes 30 minutes 10 minutes Standard Standard 4.5 4.5 0.48 0.56 0.28 0.32 (untreated ) Nitrided 5.0 4.0 0.58 0.52 0.30 0.24

  The test conditions are indicated in the Ta-

beau 2.

Table 2

  Test machine Ball-on-disc test machine Sliding speed 60 m / min (597 rpm) Surface pressure 2 Surface pressure 35.27 kgf / cm (poise 1 kgf) medium Disc material A390 (material of aluminum at 17% Si) Surface roughness 0.4 - 0.5 uRa 0.4 - 0.5 mRa of the disc Ball 0.5 inch Temperature Ambient temperature Oil quantity l) 2) Amount of oil 1: low (3 dilution rate)) 2: high 2) lubrication 3) Test time In 30 minutes 3 Atmosphere HFC134a (4.0 kgf / cm pressure) Note l-) 10 The lubricating oil was diluted in acetone up to the oil concentration of 1%, 2% and 3%. The disc was immersed in the solution and then removed from it to allow the acetone to evaporate. The amount of oil deposited on the disc was 1.5 to 2 mg at a concentration of 1%, about 3 mg at the concentration of

  2%, and 4 to 5 mg at a concentration of 3%.

  About 0.25 g of lubricating oil was dropped dropwise onto the disc (10 drops using a dropper pipette). We were measuring the

wear rate 30 minutes later.

  3) We stopped at a coefficient of friction of 1.0 or at

after 30 minutes.

  The surface treatment of the ball is indicated

in Table 3.

Table 3

  Test object Standard Comparative Treatment (not treated) Invention realization Nitrided

  Before performing the test in refrigerated gas

  However, a preliminary test was carried out in air in order to adjust the measurement conditions. The results are indicated in FIG. 4. The quantity of lubricating oil was the minimum quantity since the disc was immersed in the solution at 1% concentration. The time until

  seizure was initially planned to be inside

  laughing 30 minutes. In fact, the lifespan was inside

  15 minutes less in all samples, and results were almost as expected. If the duration before

  seizure was longer, we increased n. Regarding

  identifies the lifespan before seizing, the embodiment

  according to the invention was slightly higher than the example

parative.

  In the preliminary test, the values were determined

  their approximate lubrication oil quantity and service life, while in the following tests the

  refrigerant gas pressure (HFC134a) was set to the pressure

  4 kgf / cm2, and we determined (1) the lifespan

  before seizing for variable quantities of lubricating oil

  as well as with or without surface treatment of the ball, and (2) the rate of wear with sufficient oil to

  do not cause seizure, as well as with or without treatment

surface of the ball.

  Results at 1% concentration are indicated

  as in figure 5. In the refrigerant gas, all the results

  tats were graded within 1.5 minutes, and the lifespan was very short. Compared to results in air (Figure 4), the lifespan is less than 1/5. he

  seems that the reason why the lifespan was short

  shortened, was that the refrigerant gas dissolved in the lubricating oil, thereby decreasing the function of

oil film formation.

  Results at 2% concentration are indicated

  as in Figure 6. Compared to the results at 1% of

  concentration, the lifespan until seizure was slight-

  considerably longer, but was not notably prolonged.

  Results at 3% concentration are indicated

  as in Figure 7. Compared to the results at 2% concentration, the lifespan until seizure was longer

  long, but the fluctuations were also greater.

  The comparative example and the embodiment according to the invention

  tion seem to be practically on the same level.

  In order to compare the wear rates, the test

  was carried out with sufficient oil so as not to provo-

  quit seizing during the test. Lubricating oil

  was previously applied in the central area of the diameter

  be from the track on the disc, by 10 drops (0.25 g) using a drip pipette. There was no

  seizure during 30 minutes of operation.

  The frictional force was evaluated in terms of the coefficient of friction. The wear rate was measured at

  where the wear marks on the disc were parallel

  related to the grinding marks (positions at 0 and 180), and evaluated in terms of maximum depth and maximum width of the wear marks. The number of repetitions of the tests was 2. The results of measurement of depth of the marks

  wear after the test are shown in figure 8. The pro-

  founder in the embodiment according to the invention was

  almost the same as in the comparative example. The chan-

  friction coefficient over time, obtain

  bare in the wear test, are shown in Figure 9.

  As has been described so far, due to the fact that the shoe for a beater plate compressor according to the invention

  is nitrided at least on the surface of the outer circumference

  which engages against the spherical seat of the piston, and on the flat surface which comes into sliding contact with

  the beater plate, the seizure resistance is considerable

  significantly increased, thereby increasing the life of the compressor. The nitriding of the hoof blank at the stage of a steel ball is advantageous since a uniform nitride layer is formed, and bumps are practically unlikely to occur in the processing steps.

  later. In addition, the use of steel for rolling bearings, as a material for making the shoe, increases the wear resistance of this shoe, while the seizure resistance is further increased by nitriding.

Claims (4)

R E V E N D I C A T I O N S   1) Hemispherical shoe (10) for compressor with bat-top   tor, comprising a convex spherical surface (14) intended to engage against the spherical seat (4b) of a piston (4), and a flat surface (18) intended to come into sliding contact with a beater plate (2 ),   characterized in that the shoe (10) is cemented by nitriding.   2) Method for manufacturing a shoe (10) for a beater plate compressor, characterized in that   it includes the steps of giving a spherical form   than a steel blank for rolling bearings, for example   matrix forging, grinding spherical steel material   that thus obtained, to cement the spherical steel material by nitriding, and to give the spherical steel material   a hemispherical shape by pressing.   3) Method according to claim 2, characterized in that matrix forging, equalization, nitriding,   softening, grinding, pressing, quenching and re-   baked, rolling, flat grinding and flat polishing, are performed sequentially.   4) Shoe (10) for beater plate compressor, manufactured   by the process according to claim 2 or the claim tion 3.