EP1387957B1 - Reciprocating engine with an articulation arrangement - Google Patents

Abstract

In a reciprocating-piston machine, in particular a refrigerant compressor for a motor vehicle air-conditioning system, including a machine shaft, a plurality of pistons are arranged, at the same distance from the machine shaft, on a cylinder envelope defined by the axes of the pistons and extending around the machine shaft, and an annular pivoting disc which is driven by the machine shaft and which engages the pistons via a joint arrangement, the joint arrangement has an at least partially spherical receptacle, in which at least one sliding element structure is arranged moveably relative to the associated piston and relative to the pivoting disc, including a first sliding element having a first sliding face in the form of a spherical segment with a first geometric center (M<SUB>1</SUB>, M<SUB>3</SUB>), and a second sliding element having a second sliding face in the form of a spherical segment with a second geometric center (M<SUB>2</SUB>, M<SUB>4</SUB>) arranged at a distance from the first geometric center.

Description

The invention relates to a reciprocating engine according to the preamble of claim 1.

From the publication DE 197 49 727 A1 is a generic reciprocating engine known. It comprises a machine housing in which a plurality of pistons are arranged around a rotating drive shaft in a circular arrangement. The driving force is transmitted from the drive shaft via a driver on an annular pivot plate and from this in turn via a hinge assembly on the parallel to the machine shaft translationally displaceable piston. In this case, the swash plate is pivotally mounted on the one hand on a linearly displaceable attached to the machine shaft sliding sleeve; on the other hand, it slides along the joint arrangement, which surrounds the swivel disk with two spherical cap-shaped sliding blocks. In the joint arrangement, a power transmission center is provided, which is arranged in extension of the respectively associated piston axis and forms the geometric center of the spherical sliding surfaces of the sliding blocks. Machine shaft, driver, swivel disk and the joint assemblies and are arranged in a so-called drive chamber, in the gaseous working fluid of the reciprocating engine is present at a certain pressure. The delivery volume and thus the stroke of the piston and the inclination of the swash plate relative to the machine shaft are dependent on the pressure ratio between the suction side and pressure side of the piston or depending on the pressures in the cylinders on the one hand and in the drive chamber on the other.

From the patent US 4,762,468 is a reciprocating engine in the form of a swash plate compressor with a rotating drive shaft known on the fixed position with a swash plate is fixed. About the swash plate a plurality of pistons are articulated, the piston axes are arranged in each case the same distance from the machine shaft on a cylinder jacket around the machine shaft around. For coupling of the swash plate and the piston, two sliding elements are associated with each piston, which are mounted in a spherical segment-like receptacle on the part of the associated piston and slide on the swash plate. The sliding elements are cylindrical with a hemispherical end portion. Due to the constant angle between the swash plate and the drive shaft, the positions of the sliding elements do not change during operation of the compressor, so that a clearance between the sliding elements and the swash plate is constantly adjustable.

From the JP 05-306678 A is a reciprocating engine with a machine shaft is known which has a plurality of equally spaced around the machine shaft around the piston, wherein the pistons are articulated via a respective hinge assembly of a swash plate. The joint arrangements each have sections of spherical receptacles in which spaced-apart sliding elements are provided with ball-shaped sliding surfaces.

The object of the invention is in contrast to provide a reciprocating engine with improved performance and higher performance.

This object is achieved by a reciprocating engine having the features of claim 1.

A reciprocating piston engine according to the invention is characterized in that a first sliding element has a first spherical section-shaped sliding surface with a first geometric center and a second sliding member having a second spherical portion sliding surface with a second geometric center, wherein first and second center are spaced from each other. This arrangement is preferably just relaxed and possibly executed with play when the swash plate with the machine shaft includes a right angle and thus is in a "neutral position" in which no piston stroke is generated. The radius of the recording is approximately the radius of the sliding surfaces. In an adjustment of the swash plate in a working position in which it assumes an angle of less than 90 ° with the machine shaft, the sliding elements are pressed by the receptacle against the swash plate. This results in a particularly simple way of biasing the hinge assembly with increasing deviation of the swash plate from its neutral position. In this case, the first geometric center point on the side facing the piston guide side of the center plane of the swash plate and the second geometric center approximately on the center plane of the swash plate or also on the piston guide facing side of the median plane of the swash plate. Overall, there is a shift of the power transmission center in the direction of the piston or in the direction of the piston guide. This results in particularly low, initiated on the piston moments and very low support forces on the piston guide.

In an embodiment of the invention, the reciprocating engine according to the invention is characterized in that the first geometric center is arranged offset from the second geometric center in the direction of rotation on the cylinder jacket. This results in a reduction of a present in the neutral position game at a pivoting of the swash plate in a first direction and an increase of the game at a pivoting of the swash plate in the opposite direction.

In a further embodiment of the invention, the joint arrangement is associated with an approximately lying on the cylinder jacket of the piston axes power transmission center, which is positioned with respect to the direction of rotation of the swash plate in front of the associated piston axis. The power transmission center is a geometric location at which the power transmission between the swash plate and the respective piston takes place in an idealized manner. Further, the force transmission center is the pivot point of the joint assembly and possibly the common center of several sliding or rolling elements. By a displacement of the power transmission center on the cylinder jacket defined by the piston axes, the force can be influenced in the corresponding piston. Based on known solutions in which the power transmission center is arranged in extension of the piston axis, the position of the power transmission center should be moved against the direction of rotation of the swash plate in front of the piston axis, so that the force exerted on the piston due to the inclined arrangement of the swash plate rotation or tilting moment and corresponding support forces are reduced to a piston guide.

Fig. 1

einen Längsschnitt durch eine erfindungsgemäße Hubkolbenmaschine,

Fig. 2

eine Prinzipskizze zur Funktion der Hubkolbenmaschine gemäß Fig. 1,

Fig. 3 und 4

Prinzipskizzen zur Funktion eines ersten Ausführungsbeispiels einer erfindungsgemäßen Gelenkanordnung,

Fig. 5

eine Prinzipskizze zur Funktion eines zweiten Ausführungsbeispiels der Gelenkanordnung sowie

Fig. 6

eine Prinzipskizze zur Funktion eines dritten Ausführungsbeispiels der Gelenkanordnung.

Further features and combinations of features result from the description and the drawings. Concrete embodiments of the invention are shown in simplified form in the drawings and explained in more detail in the following description. Show it:

Fig. 1

a longitudinal section through a reciprocating piston engine according to the invention,

Fig. 2

a schematic diagram of the function of the reciprocating engine of FIG. 1,

3 and 4

Schematic diagrams for the function of a first embodiment of a joint arrangement according to the invention,

Fig. 5

a schematic diagram of the function of a second embodiment of the hinge assembly and

Fig. 6

a schematic diagram of the function of a third embodiment of the hinge assembly.

In Fig. 1 is a longitudinal section through a reciprocating engine 1 is shown in the form of a refrigerant compressor for a motor vehicle air conditioning. The reciprocating piston engine 1 has a plurality of pistons 4 arranged in a machine housing 3. All piston axes 12 are at a fixed distance from the axis of rotation 11, i. geometrically arranged on a cylinder jacket (not shown) around the machine shaft 2 and aligned parallel to the axis of rotation 11 of the machine shaft. The pistons 4 are guided in cylindrical bushings 10 (piston guides) in which cylindrical compression chambers 13 are formed (compare FIGS. 2 to 4). The pistons 4 separate the compression chambers 13 from a so-called drive chamber 14 ("crankcase"). About a subsequently explained in more detail power transmission arrangement, the rotational movement of the machine shaft is converted into a translational movement of the piston 4.

On the machine shaft 2, a sliding body is guided in the form of a sliding sleeve 9. On the sliding sleeve 9, in turn, a preferably annular swash plate 5 is mounted, wherein the swash plate 5 together with the sliding sleeve 9 in the direction of the axis of rotation 11 is displaceable. On the sliding sleeve 9, two short pins are mounted on both sides, which define a transverse to the axis of rotation 11 of the machine shaft aligned hinge axis 8, about which the swash plate 5 is pivotable.

In a recess 2a of the machine shaft 2, a driver 7 is fixed. The driver 7 protrudes approximately at right angles from the machine shaft and engages with a spherical articulation section in a radially open receptacle 15 on the part of the swash plate (see Fig. 2). Since the driver 7 is fixed to the machine shaft, a pivoting of the swash plate about the hinge axis 8 is coupled to the displacement of the sliding sleeve 9. About the driver 7, the rotation of the machine shaft 2 is transmitted to the swash plate during operation of the reciprocating piston (rotational movement in the direction of the arrow w).

Perpendicular to the hinge axis 8 is defined by the axis of rotation 11 main center plane which separates a suction side of a pressure side of the reciprocating engine. The main center plane rotates with the machine shaft.

The swash plate 5 is encompassed at its periphery in the region of each piston 4 by a hinge assembly 6 which slides over the swash plate when it carries out its rotational movement w. With an inclination of the swash plate 5 relative to the machine shaft 2, causes the swash plate in the course of its rotation, the piston located on the pressure side to a compression movement and lying on the suction side of the piston to a suction movement. In Fig. 2 is a simplified schematic diagram for power transmission between the machine shaft 2 and piston 4 is shown.

Further information on the structure and function of the reciprocating engine 2 are from the DE 197 49 727 A1 to which reference is expressly incorporated herein by reference. At the time of the DE 197 49 727 A1 known variant of the reciprocating engine, the power transmission center of a hinge assembly are each arranged exactly in extension of the associated piston axis on the cylinder jacket.

A first embodiment of the joint arrangement 6 is shown schematically in FIGS. 3 and 4 in more detail. FIGS. 3 and 4 (as well as FIGS. 5 and 6) show a view in the radial direction from the machine shaft 2 to the outside again, the swivel disk 5 moving in the direction of the arrow w in FIG. 3 showing a suction stroke of the piston 4 (arrow s) and in Fig. 4 causes a compression stroke of the piston 4 (arrow v).

The joint assembly 6 has a receptacle with two identical, approximately spherical guide and sliding surfaces 6a, in which two spherical cap-shaped sliding elements 16, 17 are mounted. The recording and the sliding elements 16, 17 is associated with a common geometric center M, which also forms a power transmission center K of the joint assembly 6. The sliding surfaces 6a of the receptacle and the spherical surfaces of the sliding elements 16, 17 have the same radius and the same curvature. The sliding elements 16, 17 sit with a small clearance on the swash plate 5. The power transmission center K is positioned counter to the direction of rotation w in front of the piston axis 12 of the associated piston 4 on the cylinder jacket containing all piston axes. The distance of the power transmission center M to the piston axis 12 is preferably 10% to 20% of the piston stroke.

In the intake stroke (acc. Fig. 3) transmitted from the swash plate 5 to the piston 4 force F _s, in general, is significantly smaller than that in the compression stroke (acc. Fig. 4) transmitted force F _v. This also results in very different transverse forces Q _s and Q _v . These transverse forces Q _s and Q _v respectively generate torques on the pistons, which must be compensated by the piston guide 10 and finally lead to supporting forces A _s and A _v . The supporting forces A _s and A _v are idealized in the region of the lower end of the piston guide 10. Due to the lateral offset of the power transmission center M arise Idealized force application points K _s and K _v on the piston axis 12. The force application point K _s for the suction stroke is thus further away from the piston 4 and the piston guide 10 than the power transmission center K of the joint assembly, while the force application point K _v for the compression stroke closer to the piston 4th is located as the power transmission center K of the joint assembly. For the suction stroke (according to Fig. 3) this means that the transverse force Q _{s is introduced} farther away from the piston guide 10, while during the compression stroke (according to Fig. 4) the transverse force Q _{v is introduced} closer to the piston guide 10 than without an offset between the power transmission center K and the piston axis 12. This results for the suction stroke compared to an arrangement without offset comparatively increased moment on the piston and for the compression stroke a comparatively reduced moment. The same applies to the supporting forces A _s and A _v , which are approximately equal in a preferred embodiment.

A second embodiment of the hinge arrangement 6 according to the invention is shown in FIG. The joint arrangement 6 has a receptacle with two spherical sliding / guide surfaces 6a, 6b, in which a first sliding element 18 with a spherical segment-shaped sliding surface 18a and a second sliding element 19 with a spherical segment-shaped sliding surface 19a are mounted. The first sliding element 18 is arranged on the side facing the associated piston, the second sliding element 19 on the side facing away from the piston side of the swash plate 5, so that the swash plate 5 is encompassed by the sliding elements 18, 19.

The geometric center M _{1 of} the first sliding element 18 is arranged between the median plane 5 a of the swash plate 5 and the piston (not shown), while the geometric center M _{2 of} the second sliding element 19 lies on the median plane 5 a. Thus arise for a same angular mobility different radii of curvature of Sliding surfaces 18a and 19a, wherein the smaller radius is provided in the arranged on the side of the piston guide slide 18. In the "neutral position" of the swash plate 5, ie when the swash plate and machine shaft enclose an angle of 90 °, the sliding elements 18, 19 sit with a certain play on the swash plate 5, so that during start-up of the reciprocating engine low frictional forces between the sliding elements and the swash plate occur and can quickly form a lubricating film. Said game is reduced with an inclination of the swash plate 5 (increasing swivel angle) for reasons of geometry, so that finally results in a tilt of the swash plate shown in Fig. 5 in the load-free state, a tension of the joint assembly (bias). This bias is compensated by the fact that the joint assembly 6 is bent by occurring during operation of the reciprocating engine forces. Ideally, the static preload and the dynamic operating forces at the joint arrangement are neutralized in the load condition.

Since with increasing pivot angle of the swash plate 5, the load to be absorbed by the joint assembly 6 increases in both directions of the piston movement, there is an increasing, swelling elastic bending of the joint assembly 6 with corresponding noise. This can be achieved by the proposed arrangement both in the suction and in the. Compression movement equally greatly reduced or eliminated.

The power transmission center of the joint assembly 6 is in the state of bias between the two geometric centers M ₁ , M ₂ , so that the force is introduced into the piston (relative to arrangements with a power transmission center on the center plane 5 a) generally closer to the piston guide and a smaller overturning moment is exerted on the piston. Nevertheless, embodiments are foreseeable, in which the geometric Midpoints M ₁ , M ₂ are arranged approximately mirror-symmetrically with respect to the center plane 5a and the power transmission center on the center plane 5a.

A third embodiment of the joint arrangement 6 according to the invention is shown in FIG. The hinge assembly 6 comprises two sliding members 20, 21 corresponding to those in the previously described embodiments. The sliding elements 20, 21 each have ball-section-shaped sliding surfaces 20a, 21a, which slide in a receptacle 6c, 6d. The sliding surfaces 20a, 21a have geometric centers M ₃ , M ₄ , which lie approximately on the center plane 5a of the swash plate 5 and the other on the cylinder jacket, on which all piston axes 12 (see Fig. 1 to 3) of the reciprocating engine are positioned. The geometric center M _{3 of} the closer lying on the piston guide slide 20 is seen in the direction of rotation of the swash plate (arrow w) behind the center M _{4 of} the opposite sliding element 21. As a result, for geometrical reasons, a tilt of the swashplate 5 as shown in FIG. 6 results in a reduction of the clearance provided in the "neutral position" of the swashplate. Thus, a tension of the sliding elements 20, 21 during the suction stroke corresponding to Fig. 6. With an inclination of the swash plate 5 in the opposite direction (compression stroke, not shown) results in an enlargement of the provided in the "neutral position" game.

In a modified embodiment, a joint arrangement of a piston is provided, the sliding blocks having spherical portion sliding surfaces positioned their centers according to a combination of the present in the aforementioned embodiments features in front of the associated piston axis, spaced apart in a direction parallel to the piston axis and / or in the rotational direction the swash plate are offset from each other.

By means of the proposed joint arrangements, reciprocating engines can be designed which can withstand substantially greater dynamic loads in the region of the power transmission between the swivel disk and the piston with essentially the same dimensions as compared with reciprocating engines of the prior art. At the same time there are reduced or evened balance of power in the area of the piston guides and on the joint arrangements. This results in higher performance with a smoother running and lower operating noise.

Claims (3)

1. Reciprocating-piston machine, in particular refrigerant compressor (1) for a motor vehicle air-conditioning system, with

   - a machine shaft (2),

   - a plurality of pistons (4), the piston axes of which are arranged, in each case at the same distance from the machine shaft, on a cylinder envelope around the machine shaft,

   - an, in particular, annular pivoting disc (5) which is driven by the machine shaft (2) and which

   - engages on the pistons in each case via a joint arrangement (6),

   - the joint arrangement having an at least partially spherical receptacle, in which

   - at least one sliding or rolling element is arranged moveably relative to the associated piston and relative to the pivoting disc, wherein

   - a first sliding element (18, 20) has a first sliding face (18a, 20a) in the form of a spherical segment, with a first geometrical centre (M₁, M₃), and

   - a second sliding element (19, 21) has a second sliding face (19a, 21a) in the form of a spherical segment, with a second geometrical centre (M₂, M₄), the first and the second centres being arranged at a distance from one another, characterized in that

   - the first geometrical centre (M₁) is arranged on that side of the mid-plane (5a) of the pivoting disc which faces the piston guide and the second geometrical centre (M₂) is arranged approximately on the mid-plane (5a) of the pivoting disc or likewise on that side of the mid-plane (5a) of the pivoting disc which faces the piston guide.
2. Reciprocating-piston machine according to Claim 1, characterized in that

   - the first geometrical centre (M₃) is arranged on the cylinder envelope so as to be offset in the direction of rotation (w) relative to the second geometrical centre (M₄).
3. Reciprocating-piston machine according to Claim 1 or 2, characterized in that

   - the joint arrangement (6) is assigned a centre of force transmission (K) which is located approximately on the cylinder envelope of the piston axes and which

   - is positioned in front of the associated piston axis (12) with respect to the direction of rotation of the pivoting disc (5).

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