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Axial piston compressor, especially for the air conditioning system of a motor vehicleRelated Patent Categories: Pumps, Three Or More Cylinders Arranged In Parallel, Radial, Or Conical Relationship With Rotary Transmission AxisAxial piston compressor, especially for the air conditioning system of a motor vehicle description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070224051, Axial piston compressor, especially for the air conditioning system of a motor vehicle. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The invention relates to an axial piston compressor, especially to compressors for motor vehicle air-conditioning systems, having a housing and, for drawing in and compressing a coolant, a compressor unit arranged in the housing and driven by means of a drive shaft, the compressor unit comprising pistons, which move axially back and forth in a cylinder block, and a tilt plate (swash ring, tilt ring or wobble plate) which drives the pistons and rotates together with the drive shaft. [0002] An axial piston compressor of such a kind is known, for example, from DE 197 49 727 A1. That compressor comprises a housing in which, in a circular arrangement, a plurality of axial pistons are arranged around a rotating drive shaft. The drive force is transmitted from the drive shaft, by way of a member for conjoint movement, to an annular tilt plate and in turn, from there, to the pistons displaceable in translation parallel to the drive shaft. The annular tilt plate is pivotally mounted on a sleeve which is mounted on the drive shaft so as to be axially displaceable. In the sleeve there is provided an elongate hole, through which the mentioned member for conjoint movement engages. Consequently, the capability of the sleeve for axial movement on the drive shaft is limited by the dimensions of the elongate hole. Assembly is carried out by passing the member for conjoint movement through the elongate hole. The drive shaft, member for conjoint movement, sliding sleeve and tilt plate are arranged in a so-called drive mechanism chamber, in which gaseous working medium of the compressor is present at a particular pressure. The delivery volume and consequently the delivery output of the compressor are dependent on the pressure ratio between the suction side and delivery side of the pistons or correspondingly dependent on the pressures in the cylinders on the one hand and in the drive mechanism chamber on the other hand. [0003] A somewhat different kind of construction of an axial piston compressor is described, for example, in DE 198 39 914 A1. The tilt plate is in the form of a wobble plate, there being arranged between the wobble plate and the pistons a non-rotating take-up plate mounted opposite the wobble plate. [0004] Reference is made, furthermore, to the following prior art: [0005] DE 2 524 148 [0006] U.S. Pat. No. 4,815,358 [0007] U.S. Pat. No. 4,836,090 [0008] U.S. Pat. No. 4,077,269 [0009] U.S. Pat. No. 5,105,728 [0010] In the case of the compressors described in those publications, the purpose is, inter alia, to take measures to prevent or reduce drive mechanism imbalance in use. Otherwise the known arrangements have in common the fact that the rotating components are of relatively large and, consequently, heavy construction compared to the parts moved in translation, namely the pistons, piston rod etc.. Furthermore, the known arrangements have in common the fact that the actual tilt plate apparatus is acted upon by an additional plate by means of a suitable coupling mechanism. The several rotating components are intended to bring about a righting moment of the tilt plate apparatus in the direction of minimum piston stroke, which has an influence on the regulation behaviour. [0011] The mentioned arrangements are all relatively complicated, expensive and of low compactness and for that reason they are unsuitable for the compressors required nowadays by the automobile industry for air-conditioning systems. [0012] Also in the case of mass-produced compressors as are used in motor vehicles, it is an objective that the components moved (especially their mass) should be suitably dimensioned in order to achieve a desired regulation behaviour. The compressor 6SEU 12C mass-produced by DENSO has, for example, a drive mechanism having the following masses relevant to the regulation behaviour: TABLE-US-00001 Component Number Mass of component [g] Total mass [g] Pistons 6 41 246 Sliding block 12 5 60 Masses moved in 306 g translation Swash plate 1 391 391 Guide pins 2 20 40 Masses moved in 431 g rotation [0013] From the above-mentioned figures it can be seen that a considerable component mass is provided for the parts moved in rotation. By that means an attempt is made to produce a sufficient counter-force or counter-moment relative to the masses moved in translation. The same basic idea also underlies DE 198 39 914 A1, in which indeed the rotating mass of the tilt plate or of the pivotal part thereof is so dimensioned that the centrifugal forces occurring on rotation of the drive plate are sufficient to counteract the pivotal movement of the tilt plate to provide deliberate regulation and consequently to influence, namely to reduce or to limit, or especially to keep constant, the piston stroke and accordingly the quantity delivered. [0014] The influences acting as moments about the tilt centre of a tilt plate apparatus are, in detail, the following moments, the direction of the moments being given in brackets, with (-) denoting down-regulation (in the direction of minimum stroke) and (+) denoting up-regulation (in the direction of maximum stroke): [0015] moment due to gas forces in the cylinder spaces (+) [0016] moment due to gas forces from the drive mechanism chamber (-) [0017] moment due to a restoring spring (-) [0018] moment due to an advancing spring (+) [0019] moment due to rotating masses (-); including moment due to location of centre of gravity (for example, tilt plate: tilt location.noteq.mass centre of gravity) : can be (+) or (-) [0020] moment due to masses moved in translation (+) [0021] In relation to the mentioned 6SEU 12C compressor of DENSO, which represents the typical constructional form of a tilt plate compressor, it is to be noted that the mass of such a tilt plate cannot be increased at will in order to modify the regulation behaviour accordingly. This is due to the fact that, in the case of the compressors of the described kind, the mass centre of gravity of the tilt plate is generally a substantial distance away from the tilt-providing articulation of the tilt plate. The basic justification for such an arrangement is that the tilt plate, in addition to its own guideway on the drive shaft, has to be coupled to the drive shaft or a component connected to the drive shaft by way of a positioning mechanism. [0022] The mentioned distance between the centre of gravity of the tilt plate and the tilt-providing articulation thereof results in imbalance of the drive mechanism, especially in dependence upon the tilt plate tilting angle (the centre of gravity moves "in the manner of a swing" beneath the tilt-providing articulation), and in the worst case results in an up-regulating characteristic (so-called "location of centre of gravity"). [0023] Accordingly, in the case of the compressors according to the prior art, and indeed according to both the published and the actually practised prior art, a compromise has to be reached so that a predetermined mass of the tilt plate is made available in order to produce a counter-moment to the masses moved in translation; on the other hand, however, the mass of the tilt plate must not be over-dimensioned because then the imbalance of the drive mechanism would be excessive. Otherwise, when a tilt plate is constructed in the form of a tilt ring, increasing the mass thereof is restricted by the available space. [0024] In order to address that problem it has also already been proposed that the pistons, that is to say the masses moved in translation, should be constructed as sparingly, that is to say as lightly, as possible, for example using aluminium or other materials of relatively low specific density. In that respect it has also been proposed to use hollow pistons. [0025] Reference is made furthermore to the compressor according to EP 0 809 027 A1, which relates to a particular arrangement of the coupling mechanism between the drive shaft and tilt plate apparatus. The coupling mechanism is designed for high pressure, for example when R744 is used as coolant. Also of importance in this last-mentioned prior art is so-called constant regulation of the delivery quantity. It is proposed that the kinematics of the compressor be so designed that the down-regulating tilting moments acting on the tilt plate should clearly predominate over the upregulating tilting moments. In this context it should be mentioned that the phrase "delivery quantity" is relatively imprecise. The delivery quantity could be considered constant if, for example, on doubling the speed of rotation, the tilt angle of the tilt plate apparatus halves. As a result the delivery quantity would be constant in geometric terms. Of course, other parameters will also then have an effect on the delivery quantity when the tilt angle of the tilt plate changes, for example volumetric efficiency, oil throw-off or the like. [0026] For constant regulation of the delivery quantity in the event of changing speeds of rotation, the restoring torque of the tilt plate apparatus is utilised because the tilt plate opposes its angled position because of the dynamic forces at the co-rotating plate part. This process can be aided by the force of a spring so that the increasing quantity delivered in the case of an increase in the speed of rotation is at least partly compensated by restoration of the angled or pivoted position of the tilt plate. [0027] As already mentioned hereinbefore, such a behaviour can in principle be obtained by, for example, integrating an additional mass into the drive mechanism, the inertia of which mass acts on the tilt plate by way of a coupling mechanism. It was also explained that, in the case of compressors as are used today in motor vehicles, the mass of the tilt plate cannot be increased at will without having to accept other disadvantages. This also holds true, especially, for the teaching according to DE 198 39 914 A1 and EP Application No. 99 953 619. The regulation proposed therein using the mass of the rotating components may result in regulation behaviour as a result of which the delivery output is substantially independent of the speed of rotation but this is not necessarily the case. Over-compensation may also be an outcome. The design criteria are very imprecise. The reason for that lies in the fact that the righting moment of the tilt plate is influenced only proportionally by the mass of the rotating components but quadratically by the speed of rotation (.omega.), which is to say that the quantity delivered can be compensated only in the relatively high speed of rotation range (in this case the dynamics play a part) and for exactly 2 speeds of rotation. [0028] Furthermore, compressors are known, especially mass-produced compressors for R134a, wherein the stroke volume has a tendency to increase solely because of the moments of up-regulating and down-regulating mass forces that come into play. In some cases this has to be compensated by means of appropriate regulatory intervention of the regulating valves used. In the case of relatively new developments, especially for CO.sub.2 compressors, attempts are made at reversing that behaviour. The necessary regulatory intervention can then be reduced or can even be dispensed with. [0029] For a better understanding, the described tilting behaviour due to variation in the speed of rotation is shown in FIGS. 2 and 3. FIG. 2 shows the dependence of drive mechanism chamber pressure difference, relative to the suction pressure, set against the tilt angle .alpha. or "alpha" of the tilt plate. Calculations were carried out by way of example for the following pressures: [0030] high pressure 120 bar and suction pressure 35 bar. [0031] Also calculated were the speeds of rotation: [0032] 600 rpm, 1200 rpm, 2500 rpm, 5000 rpm, 8000 rpm and 11,000 rpm. [0033] In FIG. 2, however, only five of the six plots calculated are to be seen. This is due to the fact that the plots for the speeds of rotation 600 rpm and 1200 rpm lie substantially entirely on top of one another (because of a lack of dynamic); accordingly the "delivered quantity that is independent of the speed of rotation", which is required in the prior art, is rather a wishful notion that cannot be put into practice using the measures described. [0034] Referring to the diagram according to FIG. 2, it can be very clearly seen that plots are obtained which cause the tilt plate to adopt greater tilt angles when the speed of rotation increases. The calculation was based on a tilt ring having a predetermined internal and external diameter and a predetermined height. [0035] Also of relevance are the piston mass, the reference diameter on which the pistons are located, and the number of pistons. [0036] The tilt ring preferably has a mass moment of inertia J.sub.2=J.sub..eta. or J=m/4 (r.sub.a.sup.2+.eta..sup.2+h.sup.2/3) which is greater than 100,000 gmm.sup.2. Preferably, the mass moment of inertia is greater than J=200,000-250,000 gmm.sup.2. [0037] Furthermore, the tilt ring preferably has a mass moment of inertia of J 3 = J .zeta. = m 2 .times. ( r a 2 + r i 2 ) which is greater than 200,000 gmm.sup.2, preferably about 400,000-500,000 gmm.sup.2. Continue reading about Axial piston compressor, especially for the air conditioning system of a motor vehicle... Full patent description for Axial piston compressor, especially for the air conditioning system of a motor vehicle Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Axial piston compressor, especially for the air conditioning system of a motor vehicle patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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