JPH0135190B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swash plate compressor, and more particularly to an improvement in a slider disposed between a swash plate and a piston. Conventional Technology and Problems A type of swash plate compressor consists of a swash plate fixed to a rotating shaft at a fixed angle, a piston fitted in a cylinder parallel to the rotating shaft, and a swash plate. Some types include a sliding member disposed between the piston and the piston, and the piston is reciprocated by the rotation of the swash plate, and gas is introduced into the cylinder and compressed. Conventionally, the sliding member of this compressor consists of a steel ball that engages with a recess provided in a piston, one surface of a plate-shaped body slidingly contacts the swash plate, and a recess provided in the other surface made of steel. It consisted of a ball and a shoe that engaged with the ball. As a result, the manufacturing cost is high due to the large number of sliding parts, the large number of parts is an obstacle to miniaturization and weight reduction, and there are problems in that assembly workability and parts management are complicated. In order to solve these problems, we first developed a swash plate compressor that omitted the shoe and filed an application. These are Utility Application No. 53-121758 and Japanese Patent Application No. 55-29667. The sliding member of such a swash plate compressor is composed only of a hemispherical slider whose flat part slides on the swash plate and whose spherical part engages with a recess provided in the piston.
Small size, weight reduction, cost reduction, etc. are achieved. However, in recent years, there has been an increasing demand for lighter weight compressors for vehicle air conditioning.
The applicant planned to make the swash plate and piston, which are large components in a compressor, from an aluminum alloy, and made the above-mentioned hemispherical slider and an aluminum-silicon alloy (hereinafter referred to as an Al-Si alloy). We prototyped a compressor combining a swash plate and a piston. Although this prototype machine was significantly lighter than the conventional one, as a result of operational tests, it was found that seizure was likely to occur between the slider and the swash plate, and that contact between the slider and the piston It was also found that the surface wear was large, and it was found that it was difficult to obtain sufficient durability for commercialization, especially when a lubrication method in which oil mist was mixed into the refrigerant gas was applied. Against the background of the above circumstances, the inventors of the present invention have conducted intensive research in order to develop a swash plate compressor that does not cause seizure even under severe lubrication conditions and has a long slider life. By making the flat part a convex curved surface with a slight bulge, and by making the hardness of the slider above a certain level, seizure will be prevented and wear of the slider will be reduced, resulting in sufficient durability for commercialization. I discovered the fact that it can be done. The present invention has been made based on this knowledge. Means for Solving the Problems That is, the present invention has a swash plate fixed to the rotating shaft at a fixed angle, a piston fitted in a cylinder provided parallel to the rotating shaft, and c A substantially hemispherical sliding body comprising a spherical part and a flat part, the spherical part engaging with a recess provided in the piston, and the flat part slidingly contacting the swash plate to transmit the driving force of the swash plate to the piston. In a swash plate compressor in which the piston is reciprocated as the swash plate rotates, the swash plate and piston are made of an aluminum-silicon alloy, while the slider is made of chromium-containing steel. At the same time, the hardness is made 50H _R C or more by quenching, and the flat part of the slider is
It is a smooth convex curved surface with a peak at the center and a height of 15 μm or less. Function and Effect As described above, if a convex curved surface with an extremely large radius of curvature is formed on the flat part of the slider, an oil film is likely to be formed between the slider and the swash plate as the swash plate rotates. The wear resistance and seizure resistance of both are significantly improved. Chromium-containing steels for sliders include high carbon chromium bearing steel (SUJ), chromium molybdenum steel (SCM),
Chrome steel (SCr) is suitable, and when such chromium-containing steel is hardened, a structure in which extremely hard chromium carbide fine particles are uniformly dispersed in a considerably hard matrix is obtained, and the hardness is 50H _R C or higher. Despite the high surface roughness, a sliding surface with good conformability can be obtained. It is also possible to form a hard layer by infiltrating the sliding surface of a relatively soft base material with carbon, etc., or by thermal spraying, plating, etc., but in this case, the hard layer as a whole is extremely hard. This results in poor conformability, and therefore, it is not possible to obtain as good seizure resistance as with chromium-containing steel that has been hardened to a hardness of 50H _R C or higher. Generally speaking, seizure is likely to occur when two members that slide against each other are made of the same type of material, but in the swash plate compressor according to the present invention, the swash plate is made of an aluminum-silicon alloy. On the other hand, since the slider is made of chromium-containing steel and both are made of completely different materials, this also provides the effect of improving seizure resistance. As described above, according to the present invention, seizure between the swash plate and the slider can be effectively avoided, and since the sliding surface of the slider has a high hardness, wear on this sliding surface can also be effectively avoided. The extremely low convex curved surface with a height of 15 μm or less is well maintained over a long period of time, and the hardness of the spherical part, which is the sliding surface with the piston, is also high, so wear in this part is well avoided. As a result, a swash plate compressor with excellent durability can be obtained. The present invention has been completed to provide a compact and light swash plate compressor that is equipped with a light swash plate and piston made of aluminum-silicon alloy, and has a hemispherical slider instead of the combination of steel balls and shoes. It is no exaggeration to say that only then did it become truly suitable for practical use. Embodiments Hereinafter, embodiments in which the present invention is applied to a swash plate compressor applicable to a refrigeration system for vehicle air conditioning will be described based on the drawings. In FIG. 1, reference numerals 1 and 2 indicate cylinder blocks, and a compressor main body 3 is constructed by combining two cylinder blocks 1 and 2 of mutually symmetrical shapes. 3 for each cylinder block 1 and 2
Cylinder bore 1 each (or 5 each)
a and 2a are formed parallel to the rotating shaft 5, and a double-headed piston 4 made of an Al--Si alloy is slidably fitted into these cylinder bores 1a and 2a. A rotating shaft 5 is inserted into the center hole 3a of the compressor body 3,
It is rotatably supported by bearings 6 and 7.
A swash plate 8 made of an Al-Si alloy manufactured by gravity casting is fixed to the center of the rotating shaft 5 by a spring pin 9. When the swash plate 8 rotates, it forms an approximately hemispherical surface. The piston 4 is made to reciprocate within the cylinder bores 1a, 2a through a slider 10 made of chromium-containing steel with a hardness of 60H _R C (Rockwell hardness) or higher, which is the most desirable value. That is, as shown in FIG. 2, the slider 10 has a spherical part 10a and a flat part 10b.
The plane part 10b has its center as its apex,
The height is a smooth convex surface 10c with an extremely large radius of curvature, which is the most desirable value of 2 to 5 μm, and a flat portion 10c is formed on the outer peripheral edge of the flat portion 10b.
A chamfered portion 10d forming a small inclination angle with respect to b is formed. The presence or absence of the convex curved surface 10c cannot be confirmed because it looks like a flat surface to the naked eye, but it can be sufficiently confirmed by a measuring machine as shown in the profile shown in FIG. 3, and the convex curved surface 1
The height H1 of 0c is measured as the height from the point of contact 12a between the convex curved surface 10c and the circle of the rounded part formed at the boundary with the adjacent chamfered part 10d to the apex. The slider 10 formed in this manner has the spherical surface portion 10a engaged with the recess 11 provided in the piston 4, and the flat surface portion 10b in sliding contact with the swash plate 8.
are placed on both sides. 13 and 1
4 is a thrust bearing. The slider is made by cutting a ball made of hardened chromium-containing steel, and has a convex curved surface 10c on the cut surface.
It may be manufactured by finishing it to form the chamfered portion 10d, or it may be manufactured by forging it into a hemispherical shape in advance and quenching it, and then subjecting its surface to finishing treatment such as buffing. . Further, the convex curved surface 10c may be a spherical surface with a large radius of curvature, and in this case, processing becomes easy. Returning to FIG. 1, a front housing 20 is fixed to the end face of the cylinder block 2 with a suction valve seat 15, a valve plate 16, and a gasket 17 interposed therebetween. Three suction ports 16a and three discharge ports 16b are formed in the valve plate 16, and each of them cooperates with a suction valve seat 15 and a discharge valve reed (not shown) to form three suction valves 18 and a discharge valve. It consists of 19. Each suction valve 18 is provided at a position where it can suck refrigerant gas from a common suction chamber 21 formed in the front housing 20, and each discharge valve 19 is located at a position where it can discharge refrigerant gas into a common discharge chamber 22. It is provided. The rotating shaft 5 passes through the center of the front housing 20 and projects to the outside, and is connected to a drive source at this projecting end. The rotating shaft 5 and the front housing 20 are kept airtight by a shaft sealing device 23. On the other hand, a rear housing 34 is fixed to the end face of the cylinder block 1 with a suction valve seat 31, a valve plate 32, and a gasket 33 in between.
It is connected to the suction chamber 36 via the valve 36 and to the discharge chamber 38 via the discharge valve 37. The suction chambers 21 and 36 are communicated with each other by a suction passage (not shown) formed by passing through the compressor body 3 in the axial direction, and are connected to a suction pipe by a common suction flange (also not shown). has been done. Further, the discharge chambers 22 and 38 are connected to holes 39 and 40 formed in the valve plates 16 and 32, respectively.
and are connected to a common discharge flange 43 by discharge passages 41, 42 formed in the cylinder blocks 2, 1. In the swash plate compressor configured as described above, when the rotating shaft 5 is rotated by a drive source such as an engine (not shown), the swash plate 8 fixed to the rotating shaft 5 is rotated, and the slider 10 is rotated. The piston 4 is reciprocated via the . Therefore, the slider 10 is swung and rotated in response to changes in the contact angle of the surface of the swash plate 8 with respect to the piston 4, and the flat portion 1 of the slider 10
The sliding contact portion between the swash plate 8 and the swash plate 8 is
For example, a high circumferential speed of about 23 m/sec and, for example, 80 m/sec.
Severe friction occurs due to the high surface pressure (piston load) of about Kg/ ^cm2 . In particular, when a lubrication method using oil mist mixed in refrigerant gas is applied and the rotating shaft 5 is driven at low speed,
Since the amount of lubricating oil supplied to the sliding portion decreases, seizure of the slider 10 may easily occur. Moreover, the swash plate 8 of this embodiment is hard among aluminum alloys and has high wear resistance and strength.
Since it is made of an Al-Si alloy material, it is more likely to seize with the hard slider 10. However, the flat portion 10b of the slider 10 of the present invention has a convex curved surface 10c as described above, and the hardness of the slider 10 is 60H _R C (Rockwell hardness).
Since it is made of chromium-containing steel that has been hardened to the above-mentioned extent, seizure of the slider hardly occurs. This effect is based on the presence of the convex curved surface 10c, the material and hardness of the slider 10, and the material of the swash plate 8.
This occurs even if there is no rounded portion at the boundary with 0c, but these chamfered portions 10d and rounded portions act as so-called wedges that actively draw oil adhering to the surface of the swash plate 8 into the sliding surface and promote the formation of an oil film. It has the effect of increasing the effect and making it difficult for layer burn-in to occur. In this way, the material and hardness of the slider 10 and the convex curved surface 10c formed at a slight height H1 with the center of the flat portion 10b as the apex prevent seizure with the swash plate 8 made of Al-Si alloy. It is presumed that this can be prevented for the following reasons. In other words, a wedge-shaped gap is formed between the convex curved surface 10c and the surface of the swash plate 8 with an extremely small angle, and the angle gradually decreases, so that when sliding at high speed, the surface of the swash plate 8 Fluid lubrication is achieved by the so-called wedge effect, in which the lubricating oil adhering to the cylinder is easily drawn in and an oil film is formed that prevents direct contact between the two. Further, as the slider 10 swings, the contact area between the swash plate 8 and the convex curved surface 10c changes with each rotation, and by increasing the amount of lubricating oil circulating in the contact area where the swash plate 8 and the convex curved surface 10c make sliding contact. , it is thought that the lubrication conditions will be further improved. In addition, since the hemispherical slider 10 has a high height relative to the size of the flat portion 10b, it is strongly influenced by the rotational moment based on the frictional force between it and the swash plate 8, and the leading edge of the flat portion 10b , that is, the edge of the swash plate 8 on the side opposite to the rotation direction is particularly strong.
However, in the slider 10 of this embodiment, the convex curved surface 10 is formed on the flat portion 10b.
It is considered that one of the reasons for the improvement in seizing resistance is that the pressure of the leading edge on the swash plate is reduced due to the formation of the leading edge. Slider 1
If a rotational moment acts on 0 as above,
The presence of the convex curved surface 10c allows the slider 10 to swing at a minute angle (the slider 10 and the piston 4
Since the contact surface with the slider 10 is a spherical surface, it does not, of course, impede the swinging of the slider 10). As the slider 10 swings, the portion of the convex curved surface 10c closer to the leading edge approaches the swash plate 8, and the gap between them decreases, but this gap is used to prevent lubricating oil from escaping. Since it is so small that it does not easily tolerate the movement of the slider 10, high oil film pressure is generated between the convex curved surface 10c and the swash plate 8 due to the slight rocking of the slider 10.
It serves to prevent the slider 10 from swinging any further. If the flat portion 10b of the slider 10 is completely flat, even if the slider 10 swings by a slight angle, the leading edge will be pressed against the swash plate 8 with high surface pressure, causing seizure. However, the present slider 10 has a convex curved surface 1 on the flat portion 10b.
Since 0c is formed, such a situation is avoided, the starting torque is reduced, the amount of heat generated is reduced, and seizure between the slider 10 and the swash plate 8 is prevented. Furthermore, since the slider 10 has a high hardness of 60H _R C, the swash plate 8 is particularly hard to use when starting up or rotating at low speed.
It is difficult for the swash plate 8 and the slider 10 to come into metal contact with each other, which prevents the Al-Si alloy of the swash plate 8 from adhering to the slider 10 and prevents seizure. It is possible that Also,
Since not only the flat part 10b but also the spherical part of the slider 10 has high hardness, wear on the sliding surface with the piston 4 made of Al-Si alloy is reduced, increasing the durability of the compressor. is expected to improve from this point as well. Whether or not the above inference is valid remains to be seen in future research, but its effectiveness has been proven by the following experiment. Experiment 1 Using slider samples with a convex curved surface 10c of different heights H1 and a sample without a convex curved surface, the swash plate 8
The fourth graph shows the results of measuring the pressing load (seizing load) when seizure occurs by pressing the sample against a rotating plate made of the same material as the sample and gradually increasing this pressing force.
As shown in the figure. Note that this experiment was conducted under the following conditions. Friction speed between rotating plate and slider V: 15m/sec Pressing load: 20Kg/20 minutes gradual increase method Lubrication conditions: Part lubrication method (0.4cc/min) Oil type: Refrigerating machine oil 1/light oil 9 Slider: Material High carbon chromium bearing steel (SUJ-2) Spherical diameter 13.5mm Surface roughness 0.3μm or less Rotating plate: Straightness 1μm to 1.5μm Material Al-Si alloy (A390) Surface roughness 0.7μm or less See Figure 4 According to the solid line shown (on which the convex curved surface 10c is formed), the height H1 of the convex curved surface 10c
If the seizure load exceeds 250 kg, the height
When H1 is approximately 5 μm, the seizure load reaches its maximum (500 Kg or more), and then gradually decreases, and when the height H1 exceeds 15 μm, the seizure load becomes smaller than 250 Kg. on the other hand,
According to the dotted line in the figure (where the convex curved surface 10c is not formed), the flat part 1 as shown in FIG.
When the convex curved surface 10c is not formed on 0b and the slider is flat, the seizure load of the slider is 160 kg, and the chamfered portion 1
When a rounded part is provided at the boundary between 0d and the flat part 10b, the maximum value (300 kg) is obtained when the height H2 of the flat part 10b including the rounded part is 3 μm.
After that, it gradually decreases. Note that the height H2 is measured as the height from the contact point 12b between the circle having the radius of curvature of the rounded portion and the chamfered portion 10d to the flat portion 10b. As described above, compared to the conventional slider 10 having a flat plane part 10b, the seizing load of the slider 10 having the convex curved surface 10c is always superior, and especially in the convex curved surface 10b.
In a range where the height H1 of 0c is 15 μm or less, a seizure load of 250 Kg or more, which is higher than before, is secured. Experiment On the other hand, according to an experiment conducted to investigate the relationship between the height H1 of the convex curved surface 10c and the amount of wear, slider samples with different heights H1 of the convex curved surface 10c were tested on the swash plate 8.
When pressed against a rotary plate made of the same material (Al--Si alloy A390) with a constant load, the amount of decrease in height after a predetermined time is as shown in the graph of FIG. Note that this experiment was conducted under the following conditions. Friction speed V between rotating plate and slider: 15 mm/sec Pressing load per unit area cm ² : 100 Kg (25 Kg during break-in) Test time: 100 hours (after 30 minutes of break-in) Lubrication conditions and oil type: Slider: Same as experiment 1: Material High carbon chromium bearing steel (SUJ-2) Surface roughness: 0.3 μm or less Diameter of spherical part: 13.5 mm Rotating plate: Same as experiment According to the graph in Figure 6, the height of the convex curved surface 10c
When H1 exceeds 7 μm, the amount of decrease in height H1 (amount of wear) increases rapidly. This increase in the amount of wear causes play between the swash plate 8 and the piston 4 and the slider 10, causing vibration and noise, or shortening the life of the compressor. Therefore, according to the results of both of the above experiments, the height of the convex curved surface 10c is preferably 7 μm or less in order to improve the seizure load within a range that does not increase the amount of wear on the slider 10. is 2-5 μm. Experiment The slider under each sample condition shown in Table 1 was pressed against the surface of the rotary plate with a constant load, and the time taken until the slider reached seizure was measured. The results are shown in Figures 7 and 8. . Note that this experiment was conducted under the following conditions. Friction speed V between rotating plate and slider: 15 m/sec Load on slider per unit area cm ² : 120 Kg (break-in 25 Kg) Test time: 50 hours (maximum) Lubrication conditions: Part lubrication method

【table】

[Table] Oil type: Refrigerating machine oil 1/light oil 9 mixture Oil Slider: Diameter of spherical part 13.5 mm Height of convex curved surface 3 μm Surface roughness of convex curved surface 0.3 μm or less Rotating plate: Straightness 1.0 μm to 1.5 μm or less Surface roughness 0.7μm or less Al-Si alloy (10-25%Si) According to Figures 7 and 8, the time until seizure depends on the type of chromium-containing steel of the slider and the
- It is not so affected by the silicon (Si) content of the Si-based alloy, but is most affected by the hardness of the slider, and the higher the hardness, the longer it takes to reach seizure, and the more difficult it is for seizure to occur. In other words, if the hardness is 50H _R C (Rockwell hardness) or higher, a practically satisfactory anti-seizure effect can be obtained, and if the hardness is 60H _R
It is even better if it is C or higher. Note that the x mark in FIG. 7 indicates the occurrence of seizure, and the solid line, broken line, and dashed-dotted line in FIG. 8 indicate that the silicon content of the aluminum alloy is 18%, 10%, and 25%. Further, the hardness of the Al-Si alloy is 17 to 42H _R B (Rockwell hardness) at a silicon content of 10% to 25%. Experiment Using a swash plate compressor with a total displacement of 150 cc/rev, the amount of lubricating oil sealed in the swash plate compressor was set at various levels (10 levels), and the lubrication conditions were graded under severe lubrication conditions. The presence or absence of burn-in after a predetermined time in
Table 2 and FIG. 9 show the results of an examination of the sample conditions for each of the slider and swash plate shown in Table 1. Note that this experiment was conducted under the following conditions. Rotation speed: 4000 rpm Refrigerant discharge pressure: 4 to 6 Kg/cm ² Refrigerant suction pressure: Approximately -50 mmHg Operating time: 20 hours Refrigerant gas amount: 100 g (10% of normal amount) Slider and swash plate: Experimental slider And the same conditions as the rotating plate lubricating oil: Refrigerating machine oil Oil filling amount: 100 to 270 c.c.

【table】

[Table] Swash plate: Al-Si alloy (10 to 25% Si) Piston: Al-Si alloy (AC8A) According to Table 2 and Figure 9, the amount of lubricating oil that causes seizure is Material of mover and Al-Si of swash plate
It is not so affected by the silicon (Si) content of the system alloy, but is most affected by the hardness of the slider, and the higher the hardness, the smaller the amount of lubricating oil required to cause seizure.
This means that seizure will not occur even under severe lubrication conditions such as when operating at low speeds. In other words, the results of this experiment, similar to the results of the previous experiment, indicate that in practice, if the hardness of the slider is 50H _R C or higher, a desired anti-seizure effect can be obtained;
This indicates that a value of 60H _R C or higher is even more desirable. In Table 2, the ○, △, and x marks respectively indicate a state in which all the samples are free of burn-in, a state in which a portion of a plurality of samples has burn-in, and a state in which all of the samples have burn-in. In addition, the solid line, broken line, and one-dot chain line in Figure 9 are
It shows that the silicon content of the Al-Si alloy is 18%, 10%, and 25%. According to the above experimental results, the swash plate 8 is made of Al
- Made of Si-based alloy, and has a convex curved surface 10 on the flat part 10b.
When the slider 10 made of chromium-containing steel is used, the slider 10 is used to prevent seizure.
If the hardness is 50H _R C or more, a certain effect can be obtained, and in order to obtain a more reliable effect, it is desirable that the hardness is 60H _R C or more. It goes without saying that the surfaces of the swash plate 8 and the convex curved surface 10c that are in sliding contact with each other should be as smooth as possible to prevent seizure. In other words, the surface roughness of the swash plate 8 is 2 μm.
Below, the slider 10 is preferably 0.7 μm or less.
The surface roughness of is preferably 1 μm or less, particularly 0.3 μm or less. Further, the angle of the chamfered portion 10d formed to actively draw lubricating oil into the sliding surface to promote the formation of an oil film with respect to the flat portion 10b is preferably 1 to 45 degrees, and preferably 5 to 15 degrees. .

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along the axis of a swash plate compressor showing an embodiment of the present invention. FIG. 2 is a front view of the slider shown in FIG. 1 (the unevenness of the convex curved surface 10c is exaggerated). FIG. 3 is a diagram showing an enlarged profile of the convex curved surface of the slider shown in FIG. 2. FIG. FIG. 4 is a graph showing the results of the experiment.
FIG. 5 is a diagram showing an enlarged profile of the flat part of the slider without a convex curved surface used in the experiment. FIG. 6 is a graph showing the results of the experiment. FIGS. 7 and 8 are graphs representing the results of the experiment. FIG. 9 is a graph showing the results of the experiment. 1a, 2a: cylinder bore, 4: piston,
5: Rotating shaft, 8: Swash plate, 10: Slider, 10a:
Spherical part, 10b: Plane part, 10c: Convex part, 10
d: Chamfered portion, 11: Recessed portion.

Claims (1)

[Scope of Claims] 1. A swash plate fixed to a rotating shaft at a predetermined angle, a piston fitted in a cylinder provided parallel to the rotating shaft, a spherical part and a flat part, a substantially hemispherical slider that engages with a recess provided in the piston in a spherical part, and slides in sliding contact with the swash plate in the flat part to transmit the driving force of the swash plate to the piston. , in a swash plate compressor in which the piston is reciprocated as the swash plate rotates, the swash plate and the piston are made of an aluminum-silicon alloy, and the slider is made of chromium-containing steel; Hardness reduced to 50H _R by quenching
C or more, and the flat portion of the slider is a smooth convex curved surface with a vertex at the center and a height of 15 μm or less.