Swash plate of a swash plate type compressor and the swash plate type compressor

Abstract

A swash plate fulfils the basic properties required for a swash plate, which are stable boundary lubricating state by lubricating oil, without forming a metal spray coating layer comprising a copper type or aluminum type material on the surface of a substrate 3a forming the swash plate 3 of the swash plate type compressor as an intermediate layer. The substrate 3a of the swash plate 3 comprises a disk-shaped steel sheet formed by pressing a rolled steel sheet into a disk shape, and both surfaces of the disk-shaped steel sheet are ground. Thus, resin coating layers 10 containing fluororesin, which has superior seizure resistance, can be strongly fixed to the substrate without the need to form a metal spray coating layer on the surface of the substrate. This improves the durability of the swash plate type compressor using carbon dioxide gas as a refrigerant.

Claims

1. A method of manufacturing a swash plate for a swash plate type compressor in which the swash plate is mounted directly to a rotary shaft or indirectly to the rotary shaft through a coupling member so as to be oblique to or perpendicular to the rotary shaft in a housing in which a refrigerant exists, and in which the swash plate is in sliding contact with shoes such that the rotary motion of the swash plate is converted to reciprocating motion of pistons through the shoes, thereby compressing and expanding the refrigerant, the method comprising: forming a substrate of the swash plate by pressing a rolled steel into a disk-shaped steel sheet; forming sliding surfaces on both sides of the disk-shaped steel sheet by firstly grinding side surfaces of the disk-shaped steel sheet to a flatness of 10 μm or less and a parallelism of 15 μm or less, and subjecting the side surfaces to shot blasting; forming low-friction resin coating layers on the sliding surfaces, respectively, without forming an intermediate metal coating layer between the substrate and the respective low-friction coating layers, by applying a coating material containing fluororesin, matrix resin, and graphite on the side surfaces of the disk-shaped steel sheet by spray coating and baking the thus applied coating material; and secondly grinding the low-friction resin coating layers formed on the sliding surfaces of the disk-shaped steel sheet, wherein the low-friction resin coating layers each have a thickness within a range of 8 to 30 μm, wherein the fluororesin is polytetrafluoroethylene resin and constitutes 40-50% of each of the low-friction coating layers, wherein the graphite is in the form of powder having a particle diameter of 30 μm or less, wherein the matrix resin is polyamideimide resin, wherein both side surfaces of the disk-shaped steel sheet are ground using a two-head grinding machine, and wherein the side surfaces of the disk-shaped steel sheet are top side and bottom side surfaces, and wherein the firstly grinding and the secondly grinding are both performed by a driving type two-head grinding method in which the top side and bottom side surfaces of the disk-shaped steel sheet are simultaneously ground with grinders while rotating the disk-shaped steel sheet with its center held in position.

2. The method of manufacturing a swash plate according to claim 1, wherein the ground surfaces of the disk-shaped steel sheet on both sides thereof are ground to a flatness of 8 μm and a parallelism of 10 μm or less.

3. The method of manufacturing a swash plate according to claim 1, wherein the disk-shaped steel sheet is made of SAPH440.

4. The method of manufacturing a swash plate according to claim 1, wherein the graphite is graphite containing 97.5% or more of fixed carbon.

5. The method of manufacturing a swash plate according to claim 4, wherein the graphite is artificial graphite containing 98.5% or more of fixed carbon.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a vertical sectional view of a swash type compressor embodying the present invention.

(2) FIG. 2 is an enlarged vertical sectional view of the swash plate of FIG. 1.

(3) FIG. 3 is a partially cutaway side view of the swash plate of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(4) Now the embodiment of the present invention is described with reference to the drawings. Carbon dioxide gas is used in this swash plate compressor as a refrigerant. As shown in FIG. 1, this compressor is a two-way swash plate compressor including a housing 1 in which the refrigerant exists, a swash plate 3 directly fixed to a rotary shaft 2 in the housing 1 so as to be oblique to the rotary shaft 2, and two-head pistons 5, and is structured to convert the rotary motion of the swash plate 3 to reciprocating motion of the respective two-head pistons 5 through shoes 4 that slide on both sides of the swash plate 3, thereby compressing and expanding the refrigerant in cylinder bores 6 that are equiangularly spaced from each other on both sides of the pistons 5, when the heads of the respective pistons 5 are inserted into and out of the corresponding cylinder bores 6. The rotary shaft 2, which is rotated at high speed, is supported by needle roller bearings 7 in the radial direction, and by thrust needle roller bearings 8 in the thrust direction.

(5) Each piston 5 has a recess 5a that straddles the radially outer portion of the swash plate 3. The recess 5a has axially opposed surfaces in which spherical seats 9 are formed. The hemispherical shoes 4 are seated in the respective spherical seats 9. Instead of the hemispherical shoes 4, spherical shoes may be used. The shoes 4 support the respective pistons 5 so as to be movable relative to the swash plate 3 as the swash plate 3 rotates, thereby facilitating conversion of the rotary motion of the swash plate 3 to the reciprocating motion of the respective pistons 5.

(6) As shown in FIG. 2, on the side surfaces of the substrate 3a of the swash plate 3 along which the shoes 4 slide, resin coating layers 10 comprising PTFE as a fluororesin, PAI as a heat-resistant resin, and graphite powder are formed.

(7) The substrate 3a of the swash plate 3 is a disk-shaped steel sheet formed by pressing a rolled steel sheet. Both side surfaces of the disk-shaped steel sheet are ground into sliding surfaces along which the shoes slide. The low-friction resin coating layer 10, which contains 40 to 50% by weight of fluororesin, is formed on each sliding surface.

(8) The resin coating layers 10 are formed on the surfaces of the substrate 3a by applying by spray-coating a coating agent formed by dissolving PAI in a solvent to form a resin solution and diluting the solution by adding PTFE and graphite powder, and then by baking the thus applied coating agent at 240° C. The content ratios of PAI and graphite powder are 150 parts by weight and 10 parts by weight based on 100 parts by weight of PTFE. PTFE used was an irradiated recycled PTFE, PAI was a PAI varnish dispersed with N-methylpyrrolidone, and graphite powder was an artificial graphite having an average particle diameter of 10 μm.

EXAMPLES

Examples of the Invention

(9) In each example of the invention, the substrate 3a of the swash plate 3 was formed as follows: A steel sheet SAPH440 was formed into a disk shape by pressing, and roughly machined by a lathe to the thickness of 6.5 mm and a diameter of 90 mm. Both sides thereof were then ground using a two-head grinding machine (grinder: #80) so that the thickness of the substrate decreases to 6.36 mm. Table 1 shows the measured accuracy values after the respective steps.

(10) The disk substrates thus formed were subjected to shot blasting to increase their surface roughness.

(11) Then, a low-friction resin coating composition containing formula A as solid contents were applied by spray coating to both sides of the respective specimens thus formed so that their thicknesses are 30 μm on both sides after baking. After baking, final finish machining was carried out using a two-head grinding machine (grinder: #400 for resin) (to the thickness of 6.40 mm). Measured accuracy values after the finish machining are shown in Table 1.

(12) Formula A

(13) (a) PTFE: PTFE having an average particle diameter of 10 μm; 40% by weight (b) PAI: having a glass transition temperature of 245° C.; 55% by weight (c) Graphite powder: Artificial graphite having an average particle diameter of 10 μm; 5% by weight

Comparative Example

(14) A steel sheet S45CAPH440 was formed into a disk shape by pressing, and roughly machined by a lathe to the thickness of 6.5 mm and a diameter of 90 mm. Both sides thereof were then ground using a surface grinding machine (grinder: #80) so that the thickness of the substrate decreases to 6.36 mm. Table 1 shows the measured accuracy values after the respective steps.

(15) Formula A was applied by spray coating to both sides of the test piece so that the coating thickness is 30 μm after baking. After baking, final finish machining was carried out using a surface grinding machine (grinder: #400 for resin) (to the thickness of 6.40 mm). Measured accuracy values after the finish machining are shown in Table 1.

(16) TABLE-US-00001 TABLE 1 Example 1 of Example 2 of Comparative invention invention Example 1 Rough machining Cutting Cutting Cutting of substrate Flatness, μm 15  15 20 Parallelism, μm 20  20 30 Finish machining Driving type Driving type Carrier type of substrate two- two- two- head grinding head grinding head grinding Flatness, μm 3 10 20 Parallelism, μm 5 15 35 Finishing of Driving type Driving type Carrier type coating film two- two- two- head grinding head grinding head grinding Flatness, μm 3  3 14 Parallelism, μm 5  5 20 Thickness of 20  20 coating film Variation 3 12 20

(17) For the accuracy of the substrate 3a after finish machining, the flatness was 8 μm or less and the parallelism was 10 μm or less for Example 1 of the invention. For Example 2 of the invention, the parallelism (maximum difference in thickness) was 15 μm. This increased the maximum difference in thickness of the coating film to 12 μm for Example 2 of the invention, while this difference was stably around 3 μm for Example 1 of the invention.

(18) For accuracy after finish machining of the substrate in Comparative Example 1, the flatness was 20 μm and the parallelism was 35 μm. After final finishing after coating, there were portions where the substrate was exposed.

(19) For the respective test pieces for Examples of the invention and the Comparative Example, a friction/wear test was conducted using a thrust type tester in which three steel shoes (SUJ2) are brought into contact with the respective test pieces (three-shoe-on type) to measure the friction coefficients at the sliding portions in the initial stage of the test and five minutes into the test, and the depths of wear on the sliding surfaces of the respective test pieces, five minutes into the test. The test conditions are as follows: Sliding surface pressure: 10 MPa Sliding speed: 210 m/min Lubricating conditions: The sliding surfaces were wetted with PAG refrigerating machine oil. Test time: Five minutes
Table 2 shows the results of the friction/wear test.

(20) TABLE-US-00002 TABLE 2 Example 1 of Example 2 of Comparative invention invention Example 1 Initial friction 0.02 0.02 0.02 coefficient Frictional 0.04 0.04 0.08 coefficient five minutes into the test Depth of wear five 0.002 0.002 Peeling of resin minutes into the test layer Determination of the ◯ ◯ X test results

(21) For the Examples of the invention, the friction coefficient was stable from the beginning of the test to 5 minutes, and the depth of wear was extremely low. In contrast, for the Comparative Example, there were portions where the resin coating peeled off the substrate. Thus, it was discovered that the resin coating film containing fluororesin, which has superior seizure resistance, is less likely to peel off, so that the swash plate according to the present invention shows sufficiently high durability when used in a swash plate type compressor using carbon dioxide gas as a refrigerant of which the pressure in the compressor reaches as high as 10 MPa.

(22) As described, the swash plate according to the present invention is formed by pressing a rolled steel sheet into a disk shape, grinding both side surfaces of the disk-shaped steel sheet formed by pressing using a two-head grinding machine, and forming a low-friction coating layer containing 40 to 50% by weight of fluororesin in the coating film on each sliding surface. This eliminates the necessity for flame spray coating layers, which were necessary in conventional arrangements.

(23) Since the metal substrate and the low-friction resin coating composition can be formed with high accuracy, uneven wear does not occur, so that the metal substrate is never exposed even if refrigerant oil runs out.

(24) By machining a metal substrate so that its flatness is 8 μm or less and its parallelism is 10 μm or less, applying a fluororesin type coating, and machining the thus applied fluororesin type coating film, it was possible to improve the final finishing accuracy to 10 μm or less in flatness and 10 μm or less in parallelism.

(25) Thus, it was confirmed that the swash plate according to the present invention is economical and can effectively and stably achieve a boundary lubricating state even if refrigerating machine oil runs out during operation of the swash plate type compressor.