Axial piston compressor

The invention relates to an axial piston compressor, especially to a compressor for the air-conditioning system of a motor vehicle, in accordance with the preamble of claim 1.

DE 195 14 748 C2 explains the tilting moments which act on a tilt plate in the case of, in principle, all compressors existing in the prior art, and also those compressors that have entered mass production, and which decisively contribute to the tilting behaviour of the tilt plate. The influences acting as moments about the centre of tilt of a tilt plate are, in detail, the following moments, the direction of the particular 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):

• • moment due to gas forces in the cylinder spaces (+)
  • moment due to gas forces from the drive mechanism chamber (−)
  • moment due to a restoring spring (−) (in the direction of minimum stroke)
  • moment due to an advancing spring (+) (in the direction of maximum stroke)
  • moment due to rotating masses (−); including moment due to location of centre of gravity (for example, tilt plate: tilt location≠mass centre of gravity): can be (+) or (−)
  • moment due to masses moved in translation (+)

The moment due to the rotating masses (hereinafter referred to as M_SW) generally has a down-regulating action; it is only in the region of very small tilt angles that as a result of, for example, an outwardly displaced location of centre of gravity (Steiner component when calculating the moment of deviation J_yz) an up-regulating moment can be produced in the case of the tilt plate (see DE 195 14 748 C2 in this regard). The component of the moment of deviation J_yz without a Steiner component already predominates, then, in the region of small tilt angles, and as the tilt angle increases the tilt plate has an increasingly down-regulating tilt moment.

Referring to DE 195 14 748 C2, a curve for the masses moved in translation having, as already explained, an up-regulating action is also shown.

Also of interest is the sum of the moments, which is likewise represented in graph form (FIG. 4 of DE 195 14 748 C2). For the entire tilt angle range, the drive mechanism exhibits up-regulating behaviour because the masses moved in translation dominate the regulation behaviour in all ranges.

From EP 0 809 027 A1 there is known a further drive mechanism which is characterised in that the delivery quantity of the compressor is so compensated by the dynamic behaviour of the drive mechanism of the compressor that the delivery quantity can be kept constant. Specifically, the following is stated therein in this respect: “In order to keep constant the delivery quantity at changing rotation speeds, use can be made of the restoring torque of the wobble plate counteracting its inclined position due to dynamic forces on the co-rotating plate part.”

Building on EP 0 809 027 A1, measures are known from DE 198 39 914 A1 as to how regulation behaviour of such a kind (at least partial compensation of the quantity delivered) can be achieved. It is proposed that the component mass of the tilt plate be so dimensioned in relation to the masses moved in translation that the centrifugal forces of the tilt plate influence its regulation behaviour. Specifically, it says in that respect that the rotating mass of the drive plate is greater than the total mass of all the pistons so that the centrifugal forces occurring during rotation of the drive plate are sufficient to deliberately counteract the pivoting movement of the drive plate in regulating manner and thereby to influence, especially to reduce or to limit, the piston stroke and, accordingly, the quantity delivered.

In the as yet unpublished DE 103 24 393 belonging to the Applicant it is explained why the component mass should not be the preferred parameter for influencing as desired the regulation behaviour of the drive mechanism as a result of changes in the speed of rotation.

The desired regulation behaviour of the compressor is primarily achieved not by means of the component mass of the tilt plate in relation to the masses moved in translation but rather by taking into account the mass moment of inertia of the component unit that is the “tilt plate”, which depends more on its geometry than on the component mass. A central idea is accordingly that, in the case of fluctuations or changes in the speed of rotation, the moment due to masses moved in translation is directly compensated, or even over-compensated, by the moment due to rotating masses.

In the case of such compressors it is desirable to reduce the frequency and intensity of regulatory interventions to a low level. With reference to the prior art and DE 195 14 748 C2 it is extremely disadvantageous that, when there is an increase in the delivery volume due to an increase in the speed of rotation, an additional increase in the delivery volume due to an increase in the tilt angle of the tilt plate is added thereto.