JPH06159244A - Sealed type electric compressor - Google Patents

Abstract

PURPOSE:To improve wear resistance of a slide section of a piston by reducing local face pressure due to point contact of the tip of the piston and forming an oil film sufficiently and improve reliability for substitute refrigerant instead of fleon without abnormal wear and seizure. CONSTITUTION:In a sealed type electric compressor which has a compression device which receives load due to compression in the compression stroke at two points, namely, on one side of a tip 10c of a piston and at an inlet of a cylinder on the opposing side, the shape in which the tip 10c of the piston and an inner peripheral face 9d of the cylinder contact at face at the maximum load point via an oil film 14 is provided partially at the tip 10c of the piston. The shape which becomes face contact forms a curve having inclination which makes interference escape as a continuous locus 10e at the tip of the piston in accordance with the inclination of the piston 10 which interferes with each position in the axial direction of the inner peripheral face 9d of the cylinder from bottom dead center to top dead center in the compression stroke.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hermetic electric compressor, which is incorporated in a refrigerating device such as a refrigerator, and uses a refrigerant containing no chlorine atom instead of a CFC-based regulated refrigerant, and a piston is a single contact. Type of hermetic electric compressor,
For example, the present invention relates to a compression mechanism having high wear resistance by improving the lubrication characteristics of a sliding portion between a piston and a cylinder in a Scotch yoke type hermetic electric compressor.

[0002]

2. Description of the Related Art In recent years, the problem of environmental pollution, particularly ozone layer depletion, has been taken up on a global scale. Therefore, chlorine-based refrigerants that destroy the ozone layer are subject to usage restrictions. Dichlorodifluoromethane (hereinafter referred to as R1) which has been conventionally used in a refrigeration cycle of a refrigeration device such as a refrigerator.
2) is also subject to the regulation, a substitute refrigerant is required, and recently 1,1,1,2-tetrafluoroethane (hereinafter referred to as R134a) that does not hinder the ozone layer depletion is adopted. I feel like I'm being done.

The structure of a conventional Scotch yoke type hermetic electric compressor will be described below with reference to FIGS. 9 to 12.
FIG. 9 is a vertical sectional view of a conventional hermetic electric compressor, FIG.
9 is a partial cross-sectional plan view showing a piston and a cylinder portion in an arbitrary compression process of FIG. 9, FIG. 11 is a diagram showing a displacement of lateral pressure applied to a piston tip portion with respect to the compression process of FIG. 10,
12 is a partial cross-sectional view showing a tilted state of the piston in FIG.

In general, as shown in FIG. 9, a hermetically-sealed electric compressor has a hermetically-sealed container 1 in which a motor part 2 is housed in a lower part and a compression mechanism part 3 is housed in an upper part. Has been done. The electric motor unit 2 includes a stator 4 and a rotor 5.
The rotor 5 is fitted with a crankshaft 6 having an eccentric portion 6a (hereinafter referred to as a crankpin) that interlocks with rotary motion. The compressor unit 3 reciprocates within the cylinder 9 by the movement of the crankshaft 6, the frame 7 serving as the bearing, the slider 8 for converting the rotational movement of the crankshaft 6 into the reciprocating movement, and the volume change due to the movement of the slider 8. In other words, suction process (volume → small),
The piston 10 is configured to repeat the compression process (large volume → small volume).

Refrigerating machine oil 11 is stored in the bottom of the closed container 1 to prevent abnormal wear and seizure of the sliding parts and to allow smooth movement. The refrigerating machine oil 11 is sucked up by the rotation of the crankshaft 6 by the pump member 12 provided at the lower end of the crankshaft 6, and centrifugal force generated by the rotation is applied to the refrigerating machine oil 11. To rise. A part of the raised refrigerating machine oil 11 is supplied to a required sliding portion through the bearing branch hole 6c and the eccentric branch hole 6d, and is scattered from the eccentric inner wall upper portion 6e of the shaft 6 and Oil is supplied to the peripheral portion 9a and the piston outer peripheral portion 10a.

Further, in the prior art, in order to improve the performance, that is, the clearance between the cylinder inner peripheral portion 9a and the piston outer peripheral portion 10a (hereinafter referred to as side clearance) is ensured to a necessary minimum to reduce the compression leakage. This side clearance needs to have a size that does not hinder the formation of an oil film of R12 having high lubricating performance and compatible refrigerating machine oil (for example, paraffinic mineral oil).

Next, the compression process of the cylinder 9 and the piston 10 in the Scotch yoke type hermetic electric compressor will be described in detail. As shown in FIG. 10, the crank pin 6a
Rotates with a radius of rotation R with reference to the center of rotation 0. At this time, the piston 8 reciprocates in the cylinder 9 by the slider 8 that slides inside the slide tube 10b of the piston 10 to suck and compress gas. In the compression process, the gas pressure X indicated by the arrow of the force distribution and the crank pin 6
A moment Y is generated in the piston 10 by the force Y applied to the piston 10 from a, and the side pressure of the piston 10 is
It concentrates on two points, the tip Z of the piston 10 and the inlet W of the cylinder 9. This side pressure changes depending on the crank angle, and becomes maximum immediately before the discharge valve opens, as shown in FIG.

On the other hand, since the piston 10 and the cylinder 9 have side clearances, the action described above causes
In the side clearance, as shown in FIG. 12, the piston 10 tilts and comes into point contact with the piston tip portion 10c and the cylinder inlet portion 9b at two points, and the lateral pressure is concentrated at these two points. Therefore, in the case of the Scotch yoke type, since the lateral pressure of the piston 10 is received at these two points, the surface pressure of this portion becomes very high. Especially, the piston tip 10c
Is heated by the high temperature gas due to compression, and the viscosity of the oil is reduced, so that the load bearing load of the oil is significantly reduced.

[0009]

By the way, as mentioned above, in order to comply with CFC regulations, R12 is used as an alternative to R12.
134a is in the trend of being applied. However, this R13
4a does not contain a chlorine atom, as has been said so far, so that an iron chloride film having high wear resistance cannot be formed, and the lubrication characteristics deteriorate. Therefore, there is a problem that the reliability of the sliding portion is significantly reduced. Particularly, in the case of the Scotch yoke type, as described above, the surface pressure is high, so that the oil film is easily broken, and the wear of the piston portion, especially the wear of the piston tip portion has been a serious problem.

Therefore, for example, a piston in a swash plate type compressor disclosed in Japanese Utility Model Publication No. 3-25341 has a chamfered portion having a tilt angle of about 45 degrees at the tip of the piston and the chamfered portion to the outer peripheral surface of the piston. A gentle inclination angle of 3 ° to 1
A 5 ° taper portion is continuously formed, and the outer peripheral portion, the taper portion, and the chamfered portion are coated with a fluorine resin. However, the above-mentioned prior art is intended to prevent the coating on the piston surface from being peeled off by the impact due to the contact between the piston and the cylinder when assembling the piston and the cylinder. It did not contribute to improving the point contact sliding.

Further, Japanese Utility Model Application Laid-Open No. 64-39485 discloses a technique of forming a plurality of oil grooves having a wavy cross section in a skirt portion of a piston. In this conventional technique, the oil groove improves the sliding characteristics between the piston and the inner diameter surface of the cylinder, but on the other hand, the side clearance is large and the airtightness is poor, so that the compression leakage is large. As a result, the volumetric efficiency is reduced and the cooling power is expected to be reduced. That is, even the technique described in this publication has not been able to improve the point contact sliding of the tip of the piston.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The local surface pressure due to point contact of the piston tip is reduced, and an oil film is sufficiently formed so that the piston sliding part An object of the present invention is to provide a hermetic electric compressor that has improved wear resistance, is free from abnormal wear and seizure, and has improved reliability with respect to CFC regulated alternative refrigerants.

[0013]

In order to achieve the above object, the structure of the hermetic electric compressor according to the present invention is such that the load associated with the compression work in the compression process is applied to one side of the piston tip and the other side of the cylinder. In a hermetic electric compressor having a compression mechanism that is received centrally at two points of the inlet, a piston tip has a shape in which the piston tip and the inner surface of the cylinder make surface contact at the maximum load point via an oil film. It is provided partially.

More specifically, the shape in which the tip portion of the piston and the inner surface of the cylinder are in surface contact is determined by the inclination of the piston that interferes with each axial position of the inner surface of the cylinder from the bottom dead center to the top dead center of the compression process. Correspondingly, a curved surface having an inclination that allows the interference to escape is formed as a continuous locus at the tip of the piston. Thus, as the refrigerant used in the refrigeration cycle, a CFC-controlled alternative refrigerant containing no chlorine atom is used.

The additional points are as follows. In order to achieve the above-mentioned object, the piston according to the present invention does not use an oilless metal or the like, and by performing a special devise on the shape of the piston tip portion, wear of the piston tip portion against the CFC regulation substitute refrigerant is achieved. Is the solution. That is, with respect to the inclination of the piston during the compression process caused by the side clearance between the piston and the cylinder, a corresponding inclination that escapes interference due to the inclination is provided at the tip of the piston. And the tip end portion of the piston is tangentially in contact with the inner surface of the cylinder by this curved surface, and is in surface contact through the oil film.

[0016]

The function of the above technical means is as follows. According to the scotch yoke type hermetic electric compressor of the present invention, the tip of the piston is in surface contact with the lubricating oil.
Therefore, since the lateral pressure is not concentrated at one point as in the conventional case, it is possible to greatly reduce the surface pressure, the oil film is broken by the surface pressure, and the cylinder, the piston and the cylinder are in direct metal contact, It will not wear out. On the other hand, the inlet of the cylinder is not directly heated by the high temperature compressed gas, so that the temperature of this portion can be kept low. Therefore, even if the viscosity of the lubricating oil is high and the surface pressure is high, the oil film rupture load that can withstand this can be secured, so that there is no particular problem of wear at the cylinder inlet.

[0017]

Embodiments of the present invention will be described below with reference to FIGS. [Embodiment 1] FIG. 1 is a cross-sectional view of essential parts showing a piston and a cylinder portion in a Scotch yoke type hermetic electric compressor according to an embodiment of the present invention. FIG. In the compression process of Fig. 3, an enlarged cross-sectional view of a main part of the piston and the cylinder showing the inclination of the piston due to the side clearance, Fig. 3 is a partially enlarged view showing the inclination formation of the piston tip portion corresponding to the inclination of the piston in Fig. 1, Figure 4
Is a partially enlarged view showing a curve connecting loci when the inclination of the piston tip portion in FIG. 3 is continuously obtained, and FIG.
FIG. 5 is a cross-sectional view of relevant parts showing a piston and a cylinder part in a compression process by the piston tip part of FIG. 4. Here, the compressor to which the present embodiment is applied is equivalent to the general Scotch yoke type hermetic electric compressor shown in FIG.

First, in FIG. 1, L, L ₁ and L ₂ indicate lengths of a compression process in which the piston 10 moves in the cylinder 9. The chain double-dashed line indicates the moving position of the piston top surface 10d. L corresponds to the distance between the piston top surface 10d and the cylinder top surface 9c when the piston 10 is at the bottom dead center. Further, L ₁ and L ₂ respectively indicate the distance that the piston top surface 10d has moved from the bottom dead center in an arbitrary compression process, and have a relationship of L ₂ > L ₁ .

In FIG. 2, the piston top surface 10d is located at an arbitrary position m from the cylinder top surface 9c in the compression process.
3 shows the state of interference between the piston 10 and the cylinder 9, which is an enlarged view of the inclination of the piston 10 caused by the side clearance.

FIG. 3 shows the lengths L, L ₁ of the compression process of FIG.
The drawing shows that the piston tip portion 10c is provided with an inclination for escaping interference, which corresponds to the inclination of the piston 10 at L ₂ . FIG. 4 shows a locus as a curve 10e when the inclination of the piston tip portion 9c in FIG. 3 is continuously obtained.

According to FIG. 2, the piston tip portion 10c is provided with an inclination without the \\\\ mark portion where the piston tip portion 10c interferes with the cylinder inner peripheral surface 9d. It will be understood that the piston tip 10c and the cylinder inner peripheral surface 9d are in surface contact. Therefore, if the state of FIG. 2 is continuously obtained corresponding to each axial position of the piston tip portion 10c, the curve 10e shown in FIG.
This curve 10e is tangential to the cylinder inner peripheral surface 9d
Will come into contact with.

Next, a method for obtaining the curve 10e will be described with reference to FIG.
Will be described in detail with reference to. In FIG. 3, l, l ₁ ,
l ₂ indicates the relative length of the compression process corresponding to the lengths L, L ₁ and L ₂ of the compression process in FIG. 1. That is, L
Set an arbitrary length l suitable for, l ₁ = l × L ₁ /
L, l ₂ = l × L ₂ / L. That is,
It is a length obtained by the ratio of arbitrary movement from the distance L at the bottom dead center, and the setting of l is a prerequisite.

First, lmin is set to an appropriate arbitrary length. In the range of 1 min from the piston top surface 10d, the inclination of the angle θmin corresponding to the inclination of the piston 10 (hereinafter referred to as the piston inclination) caused by the side clearance between the cylinder 9 and the piston 10 when the piston 10 is at the bottom dead center. A line A ₁ is provided, and the intersection of this inclined line A ₁ and the piston top surface 10d is X ₀ .

Next, when the piston 10 is in the compression process L ₁ , an inclined line A ₂ having an angle θ ₁ corresponding to the inclination of the piston at this position is provided from the corresponding point P _{1 of} l ₁ , and this inclined line A The intersection of ₂ and the inclined line A ₁ is Xmin. Next, when the piston 10 is in the compression process L ₂ , an inclined line A ₃ having an angle θ ₂ corresponding to the inclination of the piston at this position is provided from the corresponding point P _{2 of} l ₂ , and this inclined line A ₃ and The intersection with the inclined line A ₂ is X ₁ . Next, when the piston 10 is at the top dead center moved by L from the bottom dead center, an inclined line Al having an angle θ ₃ corresponding to the inclination of the piston at this position is provided from the corresponding point Pl of this l, and this inclination is The intersection of the line Al and the inclined line A ₃ is X ₂ . Where the piston 10
Has a relation of θmin> θ ₁ > θ ₂ > θ ₃ because the piston inclination becomes smaller as it approaches the top dead center.

Intersection points X ₀ , X obtained as described above
By connecting min, X ₁ , X ₂ , and Pl, one continuous line can be obtained, and at these points, there is a line where the cylinder inner peripheral surface 9d and the piston tip portion 10c make surface contact. Will be there. Thus, if X ₀ to Pl are continuously obtained, a smooth curve 10e as shown in FIG. 4 can be obtained, and this curve 10e is tangentially contacted without interfering with the cylinder inner peripheral surface 9d. can do.

For example, when L = 18 mm, side clearance is about 16 μm, and the sliding length between the cylinder 9 and the piston is about 35 mm, it is sufficient to secure lmin = about 2 mm and l = about 5 mm. θmi
It becomes a curve of a slight angle change such that n≈0.2 ° and θ ₃ ≈0.03 °. As described above, according to the present invention, the piston tip 10c during the compression process has a smooth curve 10e.
Since it comes into contact with the cylinder inner peripheral surface 9d by the tangent line of, the point contact of the piston tip portion 10c can be prevented.

As a result, the surface pressure decreases, and at the same time, the oil film 14 is easily formed due to the smooth contact. As described above, since the slope of the curve 10e is small, when the oil film 14 is formed as shown in FIG. 5, the side pressure receiving surface through the oil film 14 further expands, and as a result, the surface pressure decreases. The oil film becomes thicker. As a result, the surface for receiving the lateral pressure is further expanded, so that the surface pressure is further reduced and the oil film formation is ensured. Also, this piston tip 10
Since the curve 10e 'of c is a curve obtained according to the inclination of the piston from the bottom dead center to the top dead center of the compression process, the above-described effect can be obtained throughout the compression process.

According to this embodiment, because of the above-mentioned structure, the local surface pressure due to the point contact between the piston tip and the cylinder inner surface is reduced, and the oil film is sufficiently formed to improve the sliding characteristics. To prevent accidents such as abnormal wear and seizure, and chlorine-free CFC-compliant alternative refrigerant R1
It is possible to improve reliability with respect to 34a and the like.

[Embodiment 2] FIG. 6 is an enlarged view of a main part showing a piston tip portion according to another embodiment of the present invention. In the Scotch yoke type hermetic electric compressor as described above, since the lateral pressure of the piston tip portion 10c generally changes as shown in FIG. 11, the maximum crank angle is different from that in FIG.
Even if the piston tip portion 10c is shaped as shown in (4), a considerable effect can be obtained.

Explaining this shape with reference to FIG. 6, a taper portion 10f having an appropriate length S is formed on the piston tip portion 10c at the inclination θ of the piston at the maximum load point. Next, connect the front and back with R. By doing so, the surface pressure at the maximum load point at which the oil film easily breaks can be significantly reduced. Further, by adding R, the oil film is easily formed as described above. Also in this case, since θ is a small angle, even if the piston is tilted at the bottom dead center, if lubricating oil intervenes, the lateral pressure is sufficiently received on the surface, and the wear resistance can be further improved. In addition, as for the joint R, even if either or both of them are omitted, a considerable improvement effect can be obtained as compared with the conventional one without the taper portion 10f.

[Embodiment 3] By combining an oil groove with the above embodiment, a further better effect can be exhibited. Next, the effect of this oil groove will be described with reference to FIGS. 7 and 8. FIG. 7 is a cross-sectional view of an essential part showing a piston outer peripheral portion according to still another embodiment of the present invention, and FIG. 8 is a partial cross-sectional enlarged view showing the shape of the oil groove of FIG. Here, the compressor to which the present embodiment is applied is equivalent to the general Scotch yoke type hermetic electric compressor shown in FIG.

As described with reference to FIG. 9 above, the oil supply to the piston 10 of the Scotch yoke type hermetic electric compressor causes the refrigerating machine oil 11 scattered from the upper part 6e of the inner wall of the eccentric part of the shaft 6 to be 7, the piston outer peripheral portion 9e of the cylinder 9 and the chamfered portion 9f of 10 ° to 50 ° formed continuously from the piston inner peripheral surface 9d to the cylinder inner peripheral surface 9d have a suction effect, a so-called wedge effect, so that the piston outer circumference is indicated by a thick arrow. Part 10
It is drawn between a and the cylinder inner peripheral surface 9d, and is sent to the sliding portion. The sent refrigerating machine oil 11 enters the annular oil groove 15 formed in the piston outer peripheral portion 10a. The refrigerating machine oil 11 that has entered is supplied to the piston tip portion 10c by the reciprocating motion of the piston 10, and the lubricating characteristics of the piston tip portion 10c can be improved.

FIG. 8 shows the cross-sectional shape of the oil groove 15 in the piston outer peripheral portion 10a. The piston top surface side 15a is inclined, and the anti-piston top surface side end portion 15b is formed at approximately 90 ° with respect to the piston axis. I am doing it. The refrigerating machine oil 11 that has entered the oil groove 15 matches the relative movement with the piston 9,
In the compression process, the end portion 1 on the side opposite to the piston top surface of about 90 °
It is pooled without flowing backward from 5b, and is drawn forward by the suction effect of the inclined piston top surface side 15a in the suction step. Therefore, the lubrication characteristics of the piston tip portion 10c can always be improved, and the effect of the present invention can be further ensured.

Further, by applying a surface treatment to both or one of the sliding surfaces of the piston and the cylinder in addition to the above-mentioned structure, variations during machining,
It is possible to further improve the reliability of the piston sliding portion against variations in shape and oil shortage.

According to the above-described embodiment, since the special shape of the piston tip portion and the annular oil groove can be processed at the same time in the outer peripheral grinding step, they can be manufactured without changing the processing steps, so that an inexpensive refrigerant alternative refrigerant refrigerant can be supported. It is possible to provide the closed type electric compressor.

[0036]

As described above in detail, according to the present invention, the local surface pressure due to the point contact of the piston tip is reduced, the oil film is sufficiently formed, and the wear resistance of the piston sliding portion is improved. It is possible to provide a hermetic electric compressor that is improved and does not have abnormal wear or seizure, and that can improve reliability with respect to CFC regulated alternative refrigerants.

[Brief description of drawings]

FIG. 1 is a sectional view of essential parts showing a piston and a cylinder part in a Scotch yoke type hermetic electric compressor according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of a piston and a cylinder showing a tilt of the piston due to a side clearance in an arbitrary compression process according to an embodiment of the present invention.

FIG. 3 is a partial enlarged view showing the formation of an inclination of the piston tip portion corresponding to the inclination of the piston in FIG.

4 is a partially enlarged view showing a curve connecting loci when the inclination of the piston tip portion in FIG. 3 is continuously obtained.

5 is a cross-sectional view of essential parts showing a piston and a cylinder part in a compression process by the piston tip part of FIG.

FIG. 6 is an enlarged view of an essential part showing a piston tip end portion according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view of a main portion showing a piston outer peripheral portion according to still another embodiment of the present invention.

8 is an enlarged partial cross-sectional view showing the shape of the oil groove of FIG.

FIG. 9 is a vertical sectional view showing a conventional hermetic electric compressor.

10 is a partial cross-sectional plan view showing a piston and a cylinder portion in an arbitrary compression step of FIG.

11 is a relationship diagram showing a displacement of lateral pressure applied to a piston tip portion with respect to the compression process of FIG.

12 is a partial cross-sectional view showing a tilted state of the piston in FIG.

[Explanation of Codes] 9 Cylinder 9c Cylinder Top Surface 9d Cylinder Inner Surface 9e Piston Insertion Portion 9f Chamfer 10 Piston 10a Piston Outer Part 10c Biston Tip 10d Piston Top Surface 10e Curve 10f Taper Part 11 Refrigerator Oil 14 oil film 15 oil groove 15a piston top surface 15b opposite piston top surface side end portion _{A 1, A 2, A 3} , Al sloping line

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Isao Matsuura 800 Tomita, Ohira-machi, Shimotsuga-gun, Tochigi Prefecture Hitachi, Ltd. Living Equipment Division Cooling & Heat Headquarters (72) Inventor Hiromasa Uchida Ohira-machi, Shimotsuga-gun, Tochigi Prefecture 800 Tomita Hitachi Co., Ltd. Living Equipment Division Cooling & Heat Headquarters (72) Inventor Takashi Seshita 800 Ota Tomita, Ohira-cho, Shimotsuga-gun, Tochigi Prefecture Hitachi Ltd. Living Equipment Division Cooling & Heat Headquarters (72) Inventor Suzuki Ichihiro 800 Tomita, Ohira-machi, Shimotsuga-gun, Tochigi Prefecture, Hitachi, Ltd.

Claims (5)

[Claims] 1. A hermetically sealed electric compressor having a compression mechanism in which a load caused by a compression work in a compression process is concentratedly received at one point of a piston tip and at two points of a cylinder inlet portion on the opposite side of the piston. The inner surface of the cylinder, through the oil film,
A hermetic electric compressor characterized in that a shape that makes surface contact at the maximum load point is partially provided at the tip of the piston. 2. The shape in which the tip portion of the piston and the inner surface of the cylinder are in surface contact corresponds to the inclination of the piston which interferes with each axial position of the inner surface of the cylinder from the bottom dead center to the top dead center of the compression process. 2. The hermetic electric compressor according to claim 1, wherein a curved surface having an inclination that allows the interference to escape is formed as a continuous locus at the tip of the piston. 3. The hermetic electric compressor according to claim 1, wherein a CFC-controlled alternative refrigerant containing no chlorine atom is used as the refrigerant used in the refrigeration cycle. 4. An oil groove for supplying oil drawn into the outer circumference of the piston from a chamfered portion provided at the piston insertion opening of the cylinder to the sliding portion is provided at the outer peripheral portion of the piston. Any of the enclosed electric compressors described. 5. The oil groove on the outer circumference of the piston is formed such that the end portion on the side opposite to the piston top surface is formed at approximately 90 ° with respect to the piston axis, and the piston top surface side is an inclined surface. The hermetic electric compressor according to 4.