JP2004211695A - Piston compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston compressor with a single head piston less in wear with simple wear preventing machining. <P>SOLUTION: The single head piston 132 to be linearly reciprocated in a cylinder bore consists of a first piston portion 132c closely contacting the cylinder bore for sucking/compressing a cooling medium and a second piston portion 132d having a diameter smaller than that of the first piston portion 132c and continuously provided at the end out of the axial ends of the first piston portion 132c on the side of a crank chamber. Thus, the second piston portion 132d having the smaller diameter is avoided from contacting the cylinder bore or less thrust against the cylinder bore even in contact. Since the second piston portion 132d simply has the diameter smaller than that of the first piston portion 132c, it can be manufactured easily with cutting work. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a piston-type compressor that performs suction and compression of a refrigerant by reciprocating a single-headed piston.

  2. Description of the Related Art Conventionally, as a piston type compressor of this type, for example, a single-head piston type swash plate type compressor generally having the following structure is known.

  That is, the single-headed piston type swash plate type compressor has a plurality of cylinder bores formed in a cylinder block, a single-headed piston accommodated in each cylinder bore so as to reciprocate linearly, and a rotational movement of a driving source installed in a crank chamber. And a motion conversion mechanism for converting the single-ended piston into a reciprocating linear motion. This motion conversion mechanism includes a swash plate mounted on a rotary drive shaft, and a pair of shoes provided on a bridge portion of a single-headed piston, and a peripheral portion of the swash plate is fitted so as to slide between the shoes. . Here, when the drive shaft rotates, the swash plate rotates in an inclined state, and accordingly, the single-headed piston reciprocates up and down.

In such a single-headed swash plate type compressor, when the single-headed piston reciprocates linearly, the single-headed piston comes into contact with the end of each cylinder bore on the crank chamber side, and concentrated pressing force is applied to this end. This operation will be described with reference to FIG. 12. When the swash plate 1 rotates and the single-headed piston 2 starts the compression process, a compression force F1 and a component force F2 orthogonal thereto act on the swash plate 1, and the single-headed piston 2 moves as shown in FIG. Receives a clockwise moment M as shown in FIG. This moment M acts as a concentrated pressing force FM1 at a contact portion P1 between the outer peripheral surface of the single-headed piston 2 and the inner peripheral surface at the end of the cylinder bore 3 on the crank chamber side. For this reason, there is a problem that the inner peripheral surface of the cylinder bore 3 and the outer peripheral surface of the single-headed piston 2 are worn out at an early stage, and the abrasion powder causes clogging in the piping system. In particular, in recent years, in consideration of global environmental conservation, conversion from CFC refrigerant to CO ₂ refrigerant has been promoted, but the discharge amount of CO ₂ refrigerant may be 1/6 to 1/8 of CFC refrigerant, and accordingly, The diameter of the single-headed piston 2 becomes smaller, and the diameter of the portion where the single-headed piston 2 comes into contact with the cylinder bore 3 becomes smaller. On the other hand, the operating pressure thereof is about 10 times that of the CFC refrigerant. It has become something.

Then, in the single-head piston type swash plate type compressor using the CO ₂ refrigerant, the wear mark 2a of the single-head piston 2 was investigated. As a result of this investigation, as shown in FIG. 13 (a), a wear mark 2a remains obliquely from the base side of the single-headed piston 2 toward the tip thereof. As shown by the arrow A in (b), on the other hand, in the suction process of the single-headed piston 2, as shown by the arrow B, the pressing surface between the single-headed piston 2 and the cylinder bore 3 changes. I realized that it was formed.

  In the suction process of the single-headed piston 2, the single-headed piston 2 tilts in the opposite direction as shown by the two-dot chain line, and the single-headed piston 2 comes into contact with the inner peripheral surface of the cylinder bore 3, but no wear mark is formed.

  With respect to such a problem of the wear of the single-headed piston 2, the following inventions have been conventionally proposed. First, the invention described in Japanese Patent Application Laid-Open No. 5-302570 has a structure in which an elastic member is attached to a place where a cylinder chamber end (concentrated pressing force FM1) of a cylinder bore is applied. With this structure, the pressing force of the single-headed piston is absorbed by the elastic member, and wear of the single-headed piston is suppressed.

Next, the invention described in JP-A-2002-13472 has a structure in which a groove extending in the sliding direction of the piston is formed on the outer peripheral surface of the single-headed piston. This groove prevents pressure contact between the single-headed piston and the cylinder bore, and prevents the single-ended piston from being worn.
JP-A-5-302570 JP-A-2002-13472

  However, in the former piston type compressor (the invention described in Japanese Patent Application Laid-Open No. 5-302570), an elastic material must be provided for each cylinder bore, so that the number of parts increases and the elastic material is also assembled. It was troublesome.

  On the other hand, in the latter piston type compressor (the invention described in Japanese Patent Application Laid-Open No. 2002-13472), it is necessary to longitudinally groove the outer surface of the cylindrical single-headed piston, so that the processing is troublesome. Was.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a piston compressor capable of suppressing wear of a single-headed piston by simple wear prevention processing in view of the conventional problems.

  In order to solve the above-mentioned problems, the present invention provides a cylinder bore defined in a cylinder block, a single-headed piston accommodated in a reciprocating linear motion in the cylinder bore, and a drive source installed in a crank chamber. A piston type compressor having a motion converting mechanism for converting the rotational motion of the piston into a reciprocating linear motion of a single-headed piston, wherein the single-headed piston is in close contact with a cylinder bore and sucks and compresses a refrigerant, and a first piston portion. And a second piston portion connected to the crank chamber side end portion and having a smaller diameter than the first piston portion.

  According to the invention of claim 1, the second piston portion has a small diameter, so that contact with the cylinder bore is avoided, or even if the second piston portion contacts, the pressing force from the second piston portion to the cylinder bore is small. Become. Further, there is a case where both the first piston portion and the second piston portion come into contact with the cylinder bore at the same time. In this case, the pressing force from the single-headed piston to the cylinder bore is distributed to two places, and at each contact place. Are small. Further, since the second piston portion is only formed with a smaller diameter than the first piston portion, it can be easily manufactured by cutting.

  According to a second aspect of the present invention, in the piston type compressor according to the first aspect, the second piston portion has a structure in which an oil groove portion for forming oil is formed near the first piston portion in an annular groove. I have.

  According to the second aspect of the present invention, since the lubricating oil can be held in the oil groove, even if a concentrated pressing force is applied in the compression step, the lubricating oil is supplied to the contact portion between the single-headed piston and the cylinder bore. As a result, the frictional resistance during that time is reduced, and the wear of the single-headed piston is suppressed. The outer peripheral surface of the first piston portion may be coated with a wear-resistant material to suppress wear of the single-headed piston (claims 3 and 5).

  According to a fourth aspect of the present invention, in the piston type compressor according to the third aspect, the minimum value of the axial dimension of the second piston portion is set to 50% of the piston stroke of the single-headed piston. Thereby, the coating of the wear resistant material can be prevented from peeling off.

  According to a sixth aspect of the present invention, in the piston type compressor according to the first aspect having no oil groove portion, the minimum value of the axial dimension of the second piston portion is set to 60% of the piston stroke of the single-headed piston. I have. Thereby, the coating of the wear resistant material can be prevented from peeling off.

  In addition, a material mainly composed of polytetrafluoroethylene may be used as the wear-resistant material (the invention of claim 7).

  According to an eighth aspect of the present invention, in the piston type compressor according to any one of the first to seventh aspects, the distal end edge of the first piston portion is formed in an R shape. Thereby, the frictional resistance between the peripheral edge of the tip of the single-headed piston and the inner surface of the cylinder bore is reduced, and wear of the single-ended piston is suppressed.

  When a carbon dioxide refrigerant or a hydrocarbon refrigerant is used as the refrigerant, the concentrated high pressure of the single-headed piston is higher than that of the CFC refrigerant, but the wear of the single-headed piston is surely suppressed by the invention of claims 1 to 8. (Invention of claim 9).

  According to the first aspect of the present invention, since the second piston portion is formed to have a smaller diameter than the first piston portion, the wear of the single-headed piston is suppressed, so that the wear prevention processing is very simple. .

  According to the second aspect of the present invention, since the lubricating oil can be held in the oil groove, the lubricating oil is supplied to the contact portion between the single-headed piston and the cylinder bore, thereby further suppressing the wear of the single-headed piston.

  According to the eighth aspect of the present invention, since the distal end edge of the first piston portion is formed in an R shape, the abrasion of the single-headed piston is further suppressed.

  1 to 5 show a piston type compressor according to a first embodiment of the present invention. FIG. 1 is a sectional view of the piston type compressor, and FIGS. 2 (a) and (b) are front views of a single-headed piston. FIG. 3 is a cross-sectional view of a main part showing an initial state of a refrigerant compression step, FIG. 4 is a cross-sectional view of a main part showing a state in the middle of a refrigerant compression step, and FIG. FIG. In the present embodiment, a single-headed piston type swash plate type compressor (hereinafter, referred to as a compressor) will be described as an example among the piston type compressors.

  First, the overall structure of the compressor 10 will be described with reference to FIG. The compressor 10 has a rear housing 11 and a front housing 12, and a cylinder block 13 is connected to the rear housing 11 of the front housing 12 by bolts or the like (not shown). A plurality of cylindrical cylinder bores 131 are formed in the cylinder block 13, and each of the cylinder bores 131 accommodates a single-headed piston 132 so as to be able to reciprocate linearly. A refrigerant suction chamber 111 and a discharge chamber 112 are formed in the rear housing 11. Each of the chambers 111 and 112 communicates with a cylinder bore 131 through a valve body. Compressed. A rotating shaft 121 protruding from the cylinder block 13 to the outside of the front housing 12 penetrates the front housing 12. The rotating shaft 121 is supported by bearings 133 and 122 interposed in the cylinder block 13 and the front housing 12, and the tip thereof is connected to the electromagnetic clutch 14. The electromagnetic clutch 14 has a pulley 141 connected to a belt of an automobile engine (not shown), and a rotational force output from the engine is transmitted to the rotating shaft 121 through the electromagnetic clutch 14.

  The rotary motion transmitted to the rotary shaft 121 is converted into a reciprocating linear motion by the motion converting mechanism 15 installed in the crank chamber 123 of the front housing 12. That is, the motion conversion mechanism 15 is interposed in the rotor 151 fixed to the rotating shaft 121, the connecting portion 152 connected to the rotor 151, the swash plate 153 fixed to the connecting portion 152, and the bridge portion 132 a of the single-headed piston 132. The swash plate 153 is slidably sandwiched between the peripheral edges of the swash plate 153. Here, when the rotating shaft 121 performs a rotating motion, the rotor 151 and the connecting portion 152 rotate, and accordingly, the swash plate 153 rotates. Since the swash plate 153 rotates while being inclined with respect to the rotation shaft 121, the single-headed piston 132 reciprocates in a linear direction by an amount corresponding to the inclination width of the swash plate 153. In this motion conversion mechanism 15, the inclination angle of the swash plate 153 changes in accordance with the pressure difference between the pressure in the crank chamber 123 and the suction pressure in the cylinder bore 131, so that the stroke of the single-headed piston 132 can be changed. .

  The compressor structure as described above is the same as the conventional compressor structure, and the compressor 10 according to the present invention has a single-headed piston 132 structure. This structure will be described mainly with reference to FIG.

  That is, the single-headed piston 132 has a bridge 132a at one end in the axial direction, and a piston body 132b is formed from the bridge 132a to the other end in the axial direction (the tip of the single-headed piston 132). The bridge portion 132a is formed in a U-shaped cross section as shown in FIG. As shown in FIG. 1, a peripheral edge of a swash plate 153 is slidably held by a pair of shoes 154 inside the bridge portion 132a. The swing of the swash plate 153 causes the piston 132 to reciprocate up and down. It has become.

  On the other hand, as shown in FIGS. 2A and 2B, the piston main body 132b has a first piston portion 132c formed slightly smaller than the inner peripheral surface diameter of the cylinder bore 131, and a smaller diameter than the first piston portion 132c. The second piston part 132d is formed. The first piston portion 132c has a function of sucking and compressing the refrigerant between the distal end surface and the cylinder bore 131. The second piston 132d is connected to the bridge 132a from the end near the crank chamber of the axial end of the first piston 132c. Here, the axial dimension and the radial dimension of the second piston portion 132d are, as shown in FIG. 4, the side surface of the second piston portion 132d and the crank chamber side end 131a of the cylinder bore 131 in the compression step of the refrigerant. Are set so that they do not touch In the present embodiment, the axial dimension L1 of the second piston 132d is, for example, about 10 mm (about half of the stroke of the single-headed piston 132), and the radial dimension of the second piston 132d is, for example, 1 mm from the first piston 132c. It is formed smaller by about 2 mm.

  According to this embodiment, when the swash plate 153 rotates and the single-headed piston 132 starts the compression process, the compression force and a component force orthogonal thereto act on the single-ended piston 132 to receive the moment as in the conventional example. , As shown in FIG.

  At the initial stage of the compression process, as shown in FIG. 3, the outer peripheral surface of the first piston portion 132c is pressed against a part of the end of the cylinder bore 131 on the crank chamber side (the edge 131a of the cylinder bore 131). Further, a part of the peripheral edge 132 e of the distal end of the first piston portion 132 c is pressed against the inner peripheral surface of the cylinder bore 131. The repulsive force (FM1 ', FM2') is applied to the first piston portion 132c from the cylinder bore 131 by the concentrated pressing force of both. The repulsive forces FM1 'and FM2' cause wear of the first piston 132c. In particular, abrasion occurs at a contact portion between the edge 131a of the cylinder bore 131 and the outer peripheral surface of the first piston portion 132c (where the repulsion force FM1 'is applied).

  As the compression process proceeds, as shown in FIG. 4, the first piston portion 132c comes off the edge 131a of the cylinder bore 131, and the edge 131a faces the outer peripheral surface of the second piston portion 132d. Here, since the diameter of the second piston portion 132d is smaller than the diameter of the first piston portion 132c, the edge 131a and the second piston portion 132d are separated as shown in FIG. That is, the abrasion of the single-headed piston 132 due to the contact with the edge 131a is avoided during the compression process.

  As shown in FIG. 4, the repulsive force FM1 'applied to the first piston portion 132c is applied from the inner surface of the cylinder bore 131 to a part of the rear end 132f of the first piston portion 132c. Since the repulsion force FM1 'is applied, the abrasion force is not so large.

  Further, in addition to the above-described contact between the first piston portion 132c and the cylinder bore 131, the contact may occur between the second piston portion 132d and the edge 131a of the cylinder bore 131 (not shown). In this case, the pressing force from the single-headed piston 132 to the cylinder bore 131 is dispersed, and the concentrated pressing force at each contact point is small.

  Then, when the compression process shifts to the final stage, as shown in FIG. 5, the edge 131a and the second piston portion 132d are completely separated from each other.

  Therefore, according to the present embodiment, the edge 131a and the second piston portion 132d are in a non-contact state during the refrigerant compression process, and the repulsive forces FM1 'and FM2' are both on the inner surface of the cylinder bore 131. , The abrasion force applied to the single-headed piston 132 during the compression process is not so large.

  Here, comparing the conventional single-ended piston 2 shown in FIG. 12A with the single-ended piston 132 of the present embodiment shown in FIG. It can be understood that

  Further, in the refrigerant compression process, the operating pressure increases as the refrigerant compression progresses, and the repulsive forces FM1 ′ and FM2 ′ increase accordingly. Since it is suppressed, it is an effective means for suppressing the wear.

  FIG. 6 shows a main part of a piston type compressor according to a second embodiment of the present invention, that is, a single-headed piston. The single-headed piston 134 has a first peripheral portion 132e of the first piston portion 132c according to the first embodiment formed by rounding the peripheral edge 132e, that is, a peripheral portion 132e formed in an R shape. Note that the same components as those of the single-headed piston 132 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

  According to the second embodiment, in the refrigerant compression step, the tip peripheral edge 132e of the first piston portion 132c hits the inner peripheral surface of the cylinder bore 131, and the repulsive force FM2 'is applied to the outer surface of the first piston portion 132c. The repulsion force FM2 'is dispersed by the shape and the wear of the first piston 132c is suppressed. The other operations are the same as in the first embodiment.

  7 to 9 show a main part of a piston type compressor according to a third embodiment of the present invention, that is, a single-headed piston. The single-headed piston 135 is formed by forming an oil groove 135a in the second piston 132d according to the first embodiment. Note that the same components as those of the single-headed piston 132 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The oil groove portion 135a is, for example, grooved along the circumferential direction on the second piston portion 132d as shown in FIG. The oil groove 135a is formed near the first piston 132c.

  According to the third embodiment, the lubricating oil 16 in the crank chamber 123 adheres to the single-headed piston 135 during the suction process of the single-headed piston 135, and a part of the oil 16 accumulates in the oil groove 135a. Here, as shown in FIGS. 8 and 9, during the refrigerant compression process, blow-by gas (dashed-dotted arrow) is sucked into the crank chamber 123 and the lubricating oil 16 adhering to the outer surface of the single-headed piston 135 is removed. Is returned to the crank chamber 123 by the wind pressure, but the lubricating oil 16 accumulated in the oil groove 135a is held as it is. Therefore, during the compression step, the lubricating oil 16 reduces the frictional resistance between the first piston portion 132c and the cylinder bore 131, and the wear of the first piston portion 132c is suppressed.

  In addition, in the single-headed piston 135 according to the third embodiment, it is needless to say that the distal end edge 132e may be formed in an R shape as in the second embodiment. Other operations are the same as those in the first embodiment or the second embodiment.

  FIGS. 10A, 10B and 11 show a main part of a piston type compressor according to a fourth embodiment of the present invention, that is, a single-headed piston. The single-headed piston 136 has a configuration in which the axial dimension ratio of the first piston portion 132c and the second piston portion 132d according to the first embodiment is changed. That is, in the first piston part 136a and the second piston part 136b according to the fourth embodiment, the axial dimension L2 of the second piston part 136b is longer than the axial dimension L1 of the second piston part 132d of the first embodiment. are doing.

  According to the fourth embodiment, the contact between the edge 131a of the cylinder bore 131 and the first piston portion 136a is avoided from the initial state of the refrigerant compression step of FIG. 11 by the length of the second piston portion 136b. Therefore, as shown in FIG. 10B, it is possible to configure so that a wear mark is not formed on the outer peripheral surface of the first piston portion 136a.

  However, when the inclination angle θ2 of the single-headed piston 136 is compared with the inclination angle θ1 of the single-ended piston of the first embodiment, θ2> θ1, and the inclination angle θ2 of the single-ended piston 136 is increased. This means that each of the first piston portions 132c and 136a has a function of restricting the inclination of each single-headed piston 132 and 136, and the function of restricting the inclination is proportional to each axial dimension of each of the first piston portions 132c and 136a. It is due to. Accordingly, since the axial dimension of the first piston portion 136b of the fourth embodiment is shorter than that of the first piston portion 132c of the first embodiment, the inclination angle of the single-headed piston 136 is increased. The contact angle between the first piston portion 136a and the cylinder bore 131 increases, and the frictional resistance tends to increase.

  Such an increase in frictional resistance not only causes a hindrance of the smooth reciprocating movement of the single-headed piston 136, but also causes a wear of the single-headed piston 136. Therefore, the axial dimension of the second piston portion 136b is designed by comprehensively judging these.

  An experiment was conducted to design the axial dimension of the second piston portion 136b, and the minimum axial dimension of the second piston portion 136b (the axial dimension at which wear and damage of the first piston portion 136a was avoided) was calculated as a percentage of the piston stroke. Asked from. In this experiment, a single-headed piston 136 having an outer peripheral surface coated with a wear-resistant material was used as the first piston portion 136a, and the presence or absence of peeling of the wear-resistant material was verified. As a result of the experiment, when the axial dimension of the second piston portion 136b is formed to be smaller than 60% of the piston stroke (58% in the experiment), the wear-resistant material is peeled off, and on the other hand, more than 60% of the piston stroke. It was found that the wear resistant material did not peel when formed in dimensions.

  Further, in the single-headed piston 136 from which the wear-resistant member was peeled off, the lateral pressure load at the peeled portion was calculated based on the load calculation. As a result, it was confirmed that the peeling occurred at the portion where the lateral pressure load of 50 kgf or more was applied. Further, when the separated portion was cut into the second piston portion 136b, the axial dimension of the second piston portion 136b was 60% or more of the piston stroke.

  Further, in the present embodiment, the single-headed piston 136 having no oil groove (the oil groove 135a of the third embodiment) is used for the experiment. However, when the single-headed piston having the oil groove is used as in the third embodiment, Since the frictional resistance is further reduced by the lubricating effect of the lubricating oil, it is estimated that the coating in the axial direction of the second piston portion does not peel even at 50% of the piston stroke.

  In the first to third embodiments, the single-headed pistons 132, 134, 135 are made of a piston base made of iron or aluminum (including an aluminum alloy) material. Like the single-headed piston 136 used in the above, at least the outer peripheral surfaces of the first piston portions 132c and 136a are coated with a wear-resistant material (for example, polytetrafluoroethylene) (for example, a uniform film thickness of 20 μm to 40 μm). The wear of the single-headed pistons 132, 134, 135, 136 may be suppressed. Further, the refrigerant used in the compressor 10 according to the present embodiment is not limited to Freon, ammonia or the like, and may be a carbon dioxide refrigerant or a hydrocarbon refrigerant such as propane or butane.

Cross section of piston type compressor Front view and side view of the single-headed piston according to the first embodiment Main part sectional view showing the initial state of the refrigerant compression process of the first embodiment. Sectional drawing of the essential part showing the state in the middle of the refrigerant compression step of the first embodiment. Main part sectional view showing the end state of the refrigerant compression process of the first embodiment. Front view of a single-headed piston according to a second embodiment Front view of a single-headed piston according to a third embodiment Sectional drawing of the principal part showing the state in the middle of the refrigerant compression step of the third embodiment. The principal part expanded sectional view which shows the state in the middle of the refrigerant compression process of 3rd Embodiment. Front view and side view of a single-headed piston according to a fourth embodiment Sectional drawing of the principal part showing the initial state of the refrigerant compression process of the fourth embodiment. Sectional view for explaining the concentrated pressing force of a conventional single-headed piston Diagram showing conventional single-ended piston with wear marks and operation

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 10 ... Single head piston type swash plate type compressor, 12 ... Front housing, 13 ... Cylinder block part, 15 ... Motion conversion mechanism, 16 ... Lubricating oil, 123 ... Crank chamber, 131 ... Cylinder bore, 132, 134, 135, 136 ... Single head Piston, 132c, 136a: first piston portion, 132d, 136b: second piston portion, 135a: oil groove portion.

Claims (9)

A cylinder bore defined in the cylinder block, a single-headed piston accommodated in the cylinder bore for reciprocating linear motion, and a motion installed in the crank chamber for converting a rotational motion of a driving source into a reciprocating linear motion of the single-headed piston. In a piston type compressor equipped with a conversion mechanism,
The single-headed piston is connected to a crank chamber-side end of an axial end of the first piston that is in close contact with the cylinder bore and sucks and compresses refrigerant, and is smaller than the first piston. And a second piston portion having a diameter. The piston type compressor according to claim 1, further comprising an oil groove formed in an annular groove for oil intake in the second piston portion near the first piston portion. The piston type compressor according to claim 2, wherein an outer peripheral surface of the first piston portion is coated with a wear-resistant material. The piston type compressor according to claim 3, wherein a minimum value of an axial dimension of the second piston portion is set to 50% of a piston stroke of the single-headed piston. The piston type compressor according to claim 1, wherein an outer peripheral surface of the first piston portion is coated with a wear-resistant material. The piston type compressor according to claim 5, wherein a minimum value of an axial dimension of the second piston portion is set to 60% of a piston stroke of the single-headed piston. The piston type compressor according to any one of claims 3 to 6, wherein the wear-resistant material is mainly composed of polytetrafluoroethylene. The piston type compressor according to any one of claims 1 to 7, wherein a distal end edge of the first piston portion is formed in an R shape. The piston type compressor according to any one of claims 1 to 8, wherein the refrigerant compressed in each of the cylinder bores is a carbon dioxide refrigerant or a hydrocarbon refrigerant.

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