JP2569350B2 - Piston rod for variable displacement compressor and method of manufacturing the same - Google Patents

Description

The present invention relates to a compressor in which a drive swash plate and a piston are connected via a piston rod, and more particularly to a compressor for a variable displacement compressor. It relates to improvement of the manufacturing method.

(Related Art) A variable displacement swash plate type compressor as shown in FIG. 5 has been proposed as a compressor used in a recent automobile air conditioner.

The variable capacity swash plate compressor 3 adjusts the amount of refrigerant discharged from the compressor 3 by changing the compression chamber volume in the cylinder 25 in accordance with the suction pressure of the refrigerant returning to the compressor 3. The suction pressure is made constant.

By making the suction pressure constant in this way, the refrigerant pressure at the outlet of the evaporator (that is, the evaporation pressure of the refrigerant in the evaporator) becomes constant to some extent, so-called evaporator freezing at a low load can be avoided, and the compressor is not heated. A discharge amount corresponding to the load is produced, and the on / off operation of the compressor by the conventional magnetic clutch can be reduced as much as possible. The temperature change and the sudden torque change of the engine rotation are eliminated, and the driving comfort can be improved.

The variable displacement swash plate type compressor 3 has a drive shaft 11 that is rotationally driven by the engine via a belt, a pulley 2, and a magnet clutch 2a. A drive expansion 11 a is provided on the drive shaft 11 so as to project in a direction perpendicular to the drive shaft 11, and rotates together with the drive shaft 11 in the crank chamber 12.

A drive swash plate 13 is connected to the drive rod 11a so that the drive swash plate 13 can pivot with the pin 11b as a fulcrum with respect to the drive shaft 11,
The rotational force of the drive shaft 11 is transmitted to the drive swash plate 13 via the drive rod 11a and the pin 11b. A non-rotating wobble plate 16 is slidably attached to the drive swash plate 13 via a thrust bearing 14 and a radial bearing 15.

The wobble plate 16 has a shoe 19 slidably connected to a guide pin 18 fixed to a casing 17 of the crank chamber 12, and the rotation of the shoe 19 is prevented by the shoe 19. Is allowed.

Here, a portion that drives the piston 23 via the piston rod 22, such as the drive swash plate 13 and the wobble plate 16, is hereinafter generally referred to as a drive unit D.

On the wobble plate 16, a plurality of piston rods 22 are mounted at equal intervals in the circumferential direction via a spherical bearing portion 22a, and a piston 23 is connected to the other end of the piston rod 22 via a spherical bearing portion 22b. Have been.

The rotation of the driving swash plate 13 causes the wobble plate 16 to reciprocate in the axial direction by performing a so-called razor-like operation, whereby the piston 23 moves through the piston rod 22.
Is reciprocated. The front side portion of the piston 23 of the cylinder 25 in which the piston 23 is inserted serves as a compression chamber, and the rear side portion communicates with the crank chamber 12.

The cylinder head 30 has a suction port 29 and a discharge port 33
A return refrigerant from an evaporator flows into the suction port 29, and the refrigerant flows into the cylinder bore 26 against a closing elastic force of a suction valve 34 that closes a suction port 27 opened in the valve plate 20. It flows into a compression chamber formed therein.

The refrigerant is guided to the suction-side pressure chamber 32 through a communication passage 32a that communicates with the suction port 29 formed in the cylinder head 30.

On the other hand, the discharge port 33 is a portion where the compressed refrigerant flows out, and a discharge port opened in the valve plate 20.
It communicates with a pipe (none of which is shown) for sending the refrigerant discharged from the condenser 28 to the condenser, and further communicates with the discharge-side pressure chamber 35 via a communication passage 35a.

Between the suction side pressure chamber 32 and the discharge side pressure chamber 35, there is provided a control valve Cv which operates according to the pressure of the refrigerant returning to the suction port 29 of the cylinder 25.

The control valve Cv selectively opens the first valve port 40 when the pressure of the returned refrigerant is low, and selectively opens the second valve port 47 when the pressure is high.
Has a second control valve 39 at the top, and the first control valve
The opening 36 of the first valve port 40 is adjusted by balancing a force between a bellows 37 which expands and contracts according to the internal pressure of the suction side pressure chamber 32 and a spring 38 provided in the bellows 37. ing.

Further, the first control valve 36 is provided with an operating rod 46, and the operating rod 46 opens the second control valve 39. The two control valves 36 and 39 operate in conjunction with each other. When the first control valve 36 increases the opening of the first valve port 40 as described above, the second control valve
39 operates so as to reduce the opening degree of the second valve port 47.

Therefore, when the heat load in the cooling cycle is small, the pressure of the return refrigerant does not provide a sufficient superheat amount and returns at a low pressure, so that the pressure in the suction-side pressure chamber 32 (hereinafter, suction pressure Ps) decreases. The bellows 37 extends upward, opens the second valve port 47 widely, and discharges a part of the high-pressure refrigerant (hereinafter, discharge pressure Pd) compressed by the piston 23 in the compression step from the discharge port 28 to the second valve port 47. More passage 62 → passage 63
→ Passage 48 → Center hole 44 → Crank chamber 12 through center passage 45
To increase the internal pressure of the crank chamber 12 (hereinafter, crank chamber pressure Pc).

With this, each tilt of the wobble plate 16 has a plurality of pistons
It will be controlled by the pressure balance before and after applied to 23. That is, the pressure in the crank chamber 12
When Pc becomes slightly larger than the pressure on the suction side, the resultant force applied to the back surface of the plurality of pistons 23 acts on the wobble plate 16 as a moment about the pin 11b, thereby reducing the inclination angle of the wobble plate 16. Act like so.

For this reason, the piston 23 in the suction process cannot retreat so as to have a sufficiently large stroke, and can perform only a small compression stroke when the next compression process is started. As a result, the compression amount of the refrigerant is reduced, the discharged refrigerant amount is reduced, the flow rate of the refrigerant circulating in the cooling cycle is reduced, and an appropriate refrigerant amount corresponding to a low heat load is obtained. Due to this decrease in the refrigerant amount, the suction pressure Ps of the compressor 3 gradually increases, and as a result, is maintained at a constant suction pressure Ps.

When the heat load in the cooling cycle is large, the suction pressure Ps increases, the bellows 37 contracts, the first control valve 36 moves downward, the opening of the first valve port 40 increases, and the second valve The opening of the valve port 47 is closed. Therefore, the high discharge pressure Pd is not introduced into the crank chamber 12 and the suction pressure Ps
Is smaller than the internal pressure Pc, the refrigerant in the crank chamber 12 flows through the cylinder passage 61 → the passage 41 → the first valve port 40 → the bellows chamber 64, whereby the crank chamber pressure Pc and the suction pressure Ps are substantially equal. Become.

Therefore, the wobble plate 16 and the drive inclined plate 13 are tilted to the maximum with respect to the drive shaft 11 by the action of the above-mentioned moment, and the reciprocating stroke of the piston 23 is increased.

Therefore, when compression is performed in this state, the discharged refrigerant amount increases, the refrigerant flow rate circulating in the cooling cycle increases, the refrigerant flow rate becomes appropriate according to the high heat load, and the suction pressure Ps of the compressor 3 gradually decreases. As a result, a constant suction pressure Ps is maintained.

(Problems to be Solved by the Invention) Recently, there is a demand for such a variable displacement swash plate type compressor 3 to have a large capacity and a high speed in order to increase the discharge capacity of the refrigerant. In order to reduce the inertial force, each of the components uses a lightweight alloy based on aluminum or the like to meet the above demand.

However, since the piston rod is provided between the drive unit and the piston and is subjected to both tensile stress and compressive stress, it must be made of a material that is reliable in terms of strength. , It must be excellent in abrasion resistance because it is slidably connected to the drive unit or the piston, and moreover, since this compressor uses a plurality of piston rods, cost is reduced. It must be a cheap material.

Under such circumstances, light-weight alloys such as aluminum are not used for piston rods, and steel rods are still used.

For this reason, when the steel piston rod is used in a variable displacement compressor that rotates at high speed, a large inertial force acts due to the large mass of the piston rod, and the inclination of the drive unit is reduced by the above-mentioned moment balance. When changing, it is not possible to create a more accurate tilt state, and there is a possibility that the response and accuracy of the variable capacity are lacking.

In addition, since this piston rod has bearing portions at both ends, a portion that requires accuracy and a portion that does not need are mixed.

Therefore, in manufacturing this piston rod, it is not possible to take a method of manufacturing the whole at once,
As a conventional production method, a troublesome method is adopted in which a steel rod portion and spherical bearing portions at both ends are formed separately, and spherical bearing portions are welded to both ends of the rod portion.

For this reason, only this piston rod cannot be manufactured more quickly than other components, and the manufacturing process of this piston rod is a so-called bottleneck in a factory for mass-producing compressors.

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a lightweight and low inertia piston rod which has been made to solve the above-mentioned disadvantages and problems associated with the prior art.

A second object of the present invention is to provide a method of manufacturing a piston rod for a compressor that can be easily and quickly manufactured.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the first object, the present invention provides a drive unit having an inclination angle variably connected to a drive shaft, and reciprocates in a cylinder. A variable displacement compressor in which a piston slidably provided is connected via piston rods having spherical bearings at both ends, wherein the piston rod is made of a nitrogen-containing aluminum alloy.

In order to achieve a second object, the present invention provides a drive unit having a drive shaft variably connected to a drive shaft and a piston provided so as to reciprocate in a cylinder. A piston rod having a spherical bearing portion is formed by casting, and the spherical bearing portion before and after casting is removed together with the excess wall portion so that a concave groove is formed on the outer peripheral surface of the spherical bearing portion.

(Operation) In the present invention, since the piston rod is made of a nitrogen-containing aluminum alloy, the piston rod is extremely lightweight, and has strength against compression and tension. Also when changing the inclined state of the unit, the inertia force is small, and a more accurate inclined state of the drive unit can be created, and the hardness is sufficient.

In addition, since the surface of the piston rod is plated with Ni, it is possible to exhibit a more excellent specialty in wear resistance.

Furthermore, a piston rod having spherical bearing portions at both ends was formed by casting, and after this casting, the spherical bearing portion was cut off together with the excess wall portion so that a concave groove was formed on the outer peripheral surface of the spherical bearing portion. Therefore, the manufacture of the piston rod is facilitated, and the groove formed as a result of the shaving becomes a lubrication groove,
Lubricity when connected to a piston or the like is also improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic explanatory view showing one embodiment of the present invention, and FIG.
The drawing is a cross-sectional view along the line II-II in FIG. 1, and the same members as those shown in FIG. 5 are denoted by the same reference numerals.

In FIG. 1, a piston rod 22 of a variable displacement compressor is provided with a drive unit D variably connected to a drive shaft 11 at an inclination angle, and a piston rod provided so as to reciprocate in a cylinder 25. 23, and has spherical bearing portions 22a and 22b at both ends.

The piston rod 22 is made of an extremely high strength, high hardness and lightweight nitrogen-containing aluminum alloy.

Generally, aluminum alloys are excellent in terms of lightness, corrosion resistance, etc., but are not sufficient in strength and hardness. However, in the nitrogen-containing aluminum alloy used in the present invention, the aluminum alloy base material is densified by nitridation, and the strength and hardness required for the piston rod 22 are sufficiently satisfied. This makes it possible to create an accurate tilting state of the drive unit.

Such a nitrogen-containing aluminum alloy is, for example, Al
-What can be obtained by dissolving a high-strength aluminum alloy such as a Zn-Mg-Cu-based alloy and containing nitrogen in the form of nitride by blowing dry nitrogen gas directly at an appropriate temperature in the molten metal You can do it. In addition, high-strength aluminum alloys used as base materials include Zr, Cr, Ti, Be,
It is desired to contain an active metal element such as B.

In addition, as a preferable example of such an Al-Zn-Mg-Cu-N-based alloy, Al-6.0% Zn-2.7% Mg-0.8% Cu-N
Alloys can be mentioned. Furthermore, such Al-Zn
As the -Mg-Cu-N alloy, so-called T6 treated, which has been subjected to an artificial age hardening treatment after solution treatment, has sufficient strength and hardness, but has an appropriate spreadability even after age hardening. Therefore, it is desired that the substrate is so-called T9-treated which is further subjected to cold working. As heat treatment conditions, it is appropriate to form a solution at 480 ° C. and age harden at 110 ° C. for 20 to 30 hours.

Further, since the piston rod 22 is in a state of being brought into contact with the driving portion D and the piston 23, it is necessary to have excellent wear resistance, and the piston rod 22 is in sliding contact with the driving portion D and the piston 23. The surfaces of the spherical bearing portions 22a and 22b are plated with Ni electroless plating.

The nitrogen-containing aluminum alloy constituting the piston rod 22 has excellent wear resistance as described above, and shows a sufficiently low degree of wear even without surface treatment. In the case of plating, in synergy with the high hardness of the base nitrogen-containing aluminum alloy, the aluminum alloy constituting the driving portion D and the piston 23 is used as a mating material to exhibit particularly excellent wear resistance, and any of the members is used. Wear is hardly observed. Furthermore, since this Ni electroless plating can be performed relatively easily and inexpensively, it is most desirable from the viewpoint of improving the wear resistance of the piston rod 22, but in addition to this, from a nitrogen-containing aluminum alloy. The surface of the piston rod may be coated with an oxide film by anodic oxidation or the like, chromium plating, or a ceramic coating by a thermal spraying method, a chemical densification method, or the like. Such a surface treatment may be performed on the entire piston rod 22, or may be performed only on a part including the spherical bearing portions 22a and 22b.

Further, in forming the piston rod 22,
A mold K as shown in FIGS. 3 and 4 (only the lower mold is shown in the figure) is used to perform a batch molding by casting.

First, the above-mentioned nitrogen-containing aluminum alloy is set on a lower mold, and this is crushed by an upper mold to form a piston rod-like material a as shown in FIG.

Next, the excess meat portion b protruding from the piston rod-shaped material a is cut off by machining.

In this case, the spherical bearing portions 22a, 22 of the piston rod 22
Excess flesh portion b corresponding to b is cut off to the extent that concave groove m is formed as shown in FIG.

By doing so, the groove m serves as a passage for the lubricating oil, and when the piston rod 22 is mounted between the driving portion D and the piston 23, seizure of the spherical bearing portions 22a and 22b can be prevented. become.

The operation of the embodiment configured as described above will be described with reference to FIG.

When the variable displacement compressor 3 rotates, the driving unit D
Is inclined by a predetermined angle, and is pushed by the drive unit D to push the piston rod 22. The piston rod 22 slides the piston 23 in the cylinder 25, and discharges the refrigerant flowing from the suction port 27 while compressing it.

In this case, a reciprocating inertia force acts on the piston rod 22.

This inertial force Mn is: Mn = 4 / 5mR ² ω ² sm2α where m is the mass of the piston rod R is the distance between the rotating shaft 11 and the piston rod ω is the angular velocity α of the drive unit D is the drive unit The inclination angle of D.

That is, the inertial force Mn is proportional to the angular velocity omega ² of the drive unit D.

Therefore, if the weight of the piston rod 22, a predetermined inertial force Mn next be increased angular velocity omega ² of the driving unit D, speed of the variable capacity compressor is possible.

[Effects of the Invention] As described above, according to the present invention, the piston rod is made of a nitrogen-containing aluminum alloy, so that the piston rod is extremely lightweight, and has strength against compression and tension. When the inclination state of the drive unit is changed depending on the case, it is possible to create a more accurate inclination state of the drive unit, and since the hardness is sufficient, it exhibits excellent characteristics in abrasion resistance. It will be.

Further, since the surface of the piston rod is plated with Ni, more excellent characteristics regarding wear resistance can be exhibited.

Further, a piston rod having spherical bearing portions at both ends was formed by casting, and at the time of this casting, the spherical bearing portion was cut off together with the excess wall portion so that a concave groove was formed on the outer peripheral surface of the spherical bearing portion. The concave groove serves as a lubricating groove, and lubricity when connected to a piston or the like is also improved.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a diagram showing a piston rod according to the present invention. FIG. 4 is a perspective view showing a state in which a piston rod-shaped object is attached to the mold, and FIG. 5 is a sectional view showing a conventional variable displacement compressor. is there. 11 ... Drive shaft, 22 ... Piston rod, 23 ... Piston, 25 ... Cylinder, D ... Drive part.

Claims (3)

(57) [Claims] 1. A drive section (D) having a variable inclination angle with respect to a drive shaft (11) and a piston (23) provided to reciprocate in a cylinder (25). Variable displacement compressor connected via a piston rod (22) having a spherical bearing portion to the piston, wherein the piston rod (22) is made of a nitrogen-containing aluminum alloy. rod. 2. The piston rod for a variable displacement compressor according to claim 1, wherein the surface of the piston rod is plated with Ni. 3. A drive unit (D) having a tilt angle variably connected to a drive shaft (11) and a piston (23) provided to reciprocate in a cylinder (25). A piston rod (22) having spherical bearing portions at both ends is formed by casting, and after this casting, the spherical bearing portion is cut off together with the excess wall portion so that a concave groove is formed on the outer peripheral surface of the spherical bearing portion. Method of manufacturing piston rod for variable displacement compressor.