GB2060087A

GB2060087A - Piston Compressor

Info

Publication number: GB2060087A
Application number: GB8032467A
Authority: GB
Original assignee: STIEBER PRAEZISION
Current assignee: STIEBER PRAEZISION
Priority date: 1979-10-08
Filing date: 1980-10-08
Publication date: 1981-04-29
Also published as: FR2467306A1; DE2940679A1; IT1133181B; IT8025154A0; ES495701A0; ES8105832A1

Abstract

A piston compressor has a lubricating oil circuit (4) and a drive wheel (9) fixed on its drive shaft (2a); this drive wheel receives, between its hub (11) and its outer driving rim (12), a freewheel roller bearing assembly (10); the annular space (24) between the hub (11) and the driving rim (12) receives the roller or ball wedging elements (15) of the freewheel (13), and this space is sealed off from the outside and connected to the lubricating oil circuit (4) of the piston compressor. <IMAGE>

Description

SPECIFICATION Piston Compressor The invention relates to a piston compressor with a lubrication circuit and with a drive wheel fixed on its drive shaft.

In the case of compressors of this kind the driving torque8which is usually uniform and is for example produced by electric motor means-is used for transmitting the drive energy, required for compressing the gaseous medium (e.g. air), to a piston which can be driven by way of a crank shaft. The torque reaction which is effective at the crank shaft of the compressor, which is continuously driven at high speeds of up to about 3,000 r.p.m. is subject, at each revolution, to considerable fluctuation; indeed, it fluctuates between a maximum value occurring during the compression stroke and negative values which act in the direction of the driving torque and which are produced by the residual gas, which remains behind in the compression chamber when the exhaust stroke has ended and which expands at the start of the piston return stroke, and also by inertial forces which arise towards the end of the piston return stroke. It is a drawback in the case of these conventional piston compressors that, due to the abovementioned continuous rapid fluctuation of the torque, in comparison with a uniformly introduced torque, fluctuating stresses are experienced both at the bearings of the compressor and also at the driving elements, e.g. between a-drive pulley and a drive belt, these fluctuating stresses resulting in undesirable generation of heat and wear.

The underlying object of the invention is the provision of an improved piston compressor which in operation is not subject to these disadvantages.

As is for example clear from the brochure No.

IC LFE/2 of the Firm Stieber Rollkupplung KG, Munich, issued in 1954, freewheel clutches have principally been used as ratchet mechanisms, e.g.

in cable drives of chair lifts, as switching elements, for example in machine tools, or as over-running clutches in motor vehicles and production industry machines; the over-running action has always been initiated by substituting for the continuous drive applied on the drive side of the clutch, a further driving force which is also continuously effective at the drive shaft of the clutch, in the case of motor vehicles by (for example) acceleration forces effective at the vehicle or, in the case of production machines by (for example) the first drive of the driving shaft, which takes place initially by a starter present on the drive side of the clutch, by the more rapid drive which becomes effective at the drive shaft by a main driving machine which has been brought into operation by the starter, whereafter the starter has been brought out of operation.In the case of all these applications there are, per unit of time, only a few engagements and disengagements of the freewheel coupling. In the case of ratchet mechanisms the engagements and disengagements of the freewheel clutch usually only occur on the rare occasions when extraordinary operating conditions are experienced so that the wedging elements of the freewheel coupling are usually only subject to small fluctuations in stress.

By way of contrast, it has, surprisingly, now been found that the incorporation, which is now proposed, of a freewheel roller bearing assembly, lubricated from the piston compressor, in the drive wheel of the piston compresssor can be accepted-in spite of the continuous alternation of clutch engagements and disengagements necessitated by the operation of the compressor-with a frequency of up to 6,000/min, that is to say at a frequency which is double that of the, already high, operating speed.

Not only does this achieve the object underlying the invention, that is to say the avoidance of undesired evolution of heat and undesired wear phenomena in the driving system of the piston compressor, but it also causes the additional driving torque, which now freely acts on the drive shaft, to transmit a working speed to the compressor which is up to 20% higher than the driving speed through gas forces and inertial forces and without any further introduction of energy. In this way the efficiency of the compressor is improved to a corresponding degree, although the compressor still runs appreciably more quietly than would be the case if the proposals of this invention had not been adopted.

It is known, from Page 65 of the Journal "dhf", 12/68, 14th year, to connect independently centred freewheel couplings, which are not in the form of self-contained structures, to an already present bifurcating system. Apart from the fact that such independently centred freewheel couplings had to be installed in enclosed spaces, e.g. in a gear housing, these known structures do not permit the clutches to be used otherwise than is defined in the prior art document referred to above.

Embodiments of the invention are described in the accompanying drawings, in which: Figure 1 is a schematic side elevation of a piston compressor; Figure 2 is a partial view of one end of the crank shaft, a drive wheel being shown in axial cross-section; Figure 3 is a partial cross-section taken along line Ill-Ill of Figure 2, of the drive wheel shown in Figure 2; and Figure 4 is a partial cross-sectional view similar to that of Figure 2, of a modified drive wheel of the piston compressor.

The piston compressor 1 shown in Figure 1 has a crankshaft 2 with a conventional piston (not shown), which is reciprocable in a cylinder 3, by rotation of the crank shaft 2, and is lubricated by way of a conventional lubricating circuit, of which details are not illustrated. Figure 1 merely shows an oil sump 5, which is positioned in the crank housing 4 of the piston compressor 1 and from which lubricating oil is conveyed, by way of lubricating pump (not shown), inter alia into an infeed bore 7 (Figure 2) which extends both along the crankshaft 2 and also along a drive shaft 2a, which runs axially of the crank shaft 2, this infeed bore 7 being offset from the shaft axis 6. A return flow bore 8, which leads back to the oil sump 5 in a manner which is not illustrated in detail, is offset in the opposite direction from the shaft axis 6.As will be explained below, both bores are used for lubricating and cooling a freewheel roller bearing assembly 10 which is received in a drive wheel 9 fixed on the free end of the drive shaft 2a, and is depicted in detail in Figures 2 and 3.

The drive wheel 9 receives the freewheel roller bearing assembly 10 between its hub 11, which is fixed on the drive shaft 2a in a conventional way, and its drive rim 12, by means of which the drive can be introduced and, in accordance with the embodiment of Figure 1, in which the drive wheel 9 is constituted as a pulley, may be used for receiving a driving belt (not shown). As is shown in Figures 2 and 3, the axial centre part of the hub 11 functions as an inner camming or wedging surface of a freewheel 13, which comprises a cylindrical roller 15, serving as a wedging element, between each pair of adjacent camming projections 14. Further, the cylindrical rollers are, in a conventional fashion, biassed into their wedging position by way of a spring 16.Also associated with each wedging element 1 5 is a raceway 17, which is constituted as a wedging surface and lies between the camming projections 14. The hub also forms on both sides of the freewheel 1 3, a cylindrical raceway 1 8 for roller elements 19, also shaped as cylindrical rollers, of roller bearings 20, 21 of the freewheel roller bearing assembly 1 0.

In the vicinity of the centre transverse plane of the freewheel 1 3-and, at the same time, within the axial plane of the drive shaft 2a receiving the infeed bore 7 and the return flow bore 8transverse bores 22, 23 respectively extend from the infeed bore 7 and return flow bore 8, and thence extend radially outwardly (also passing through the hub 11) to the annular gap 24 (c.f.

Figure 2) which accommodates the wedging or camming elements 15, whereby both the freewheel 13 and also the two roller bearings 20, 21, which comprise a full complement of roller elements 19, are connected to the lubricating circuit and are effectively cooled by this lubricating circuit.

Further, as is clear from Figure 2, the freewheel roller bearing asembly 10 comprises an outer race 25, with an inner cylindrical peripheral surface which is common to the freewheel 13 and to the two roller bearings 20, 21. At its cylindrical outer periphery-the details of the shape of this outside peripheral surface arts now shown in the drawing-the outer race 25 receives, by way of a groove 27 with a key, the drive rim 12 which, as is clear from Figure 1, is constituted as a pulley, and is fixed for rotation with this drive rim 12.

It is apparent from Figure 2 that the wedging elements 15 are axially guided, on both sides and at the outer periphery of the hub 11, by retaining rings 28, which are at the same time used for the inner axial guidance of the roller elements 1 9 of the two roller bearings 20 and 21. The outer guidance of the roller elements 1 9 of the two roller bearings 20 and 21 is effected by discs 29 and 30 which are secured to the sides of the outer bearing race 25 and of which the disc lying at the compressor side is sealed off, in oil-tight manner, from the drive shaft 2a by means of an oil seal 31.

On the opposite side, the axial opening of the outer disc 30 is sealed off, in oil-tight manner, by a cap 32 which encloses the free end of the drive shaft 2a.

The freewheel roller bearing assembly 10 could, in the manner shown in Figure 4, comprise ball bearings 33 instead of the roller bearings used in the embodiment described above.

Claims

1. A piston compressor, comprising a lubricating circuit, a drive wheel fixed on a drive shaft, and having a hub and an outer drive rim, a freewheel roller bearing assembly disposed between said hub and said outer drive rim, by means of which the drive can be transmitted, wedging elements of a freewheel of the said assembly being received in an annular space between said hub and said drive rim, which space is externally sealed and connected to the lubricating circuit.

2. A piston compressor according to Claim 1, wherein the drive shaft comprises two longitudinal bores which are radially offset in oppposite directions relative to the shaft axis, one of which longitudinal bores is an entry bore and the other is a return flow bore of the lubricating oil circuit; the two longitudinal bores being each connected, within the axial plane of the drive shaft which receives them and by way of respective radially outwardly extending tranverse bores to the annular space which accommodates the wedging elements.

3. A piston compressor according to claim 1 or claim 2, wherein the freewheel roller bearing assembly has the freewheel disposed between two roller bearings.

4. A piston compressor according to any of the foregoing claims, wherein an outer race of the freewheel roller bearing assembly is closed off at the free end of the drive shaft by a cap which covers this free end.

5. A piston compressor according to any of the foregoing claims, wherein an outer race of the freewheel roller bearing assembly carries, at the compressor side, a disc which is sealed off from the drive shaft.

6. A piston compressor according to any of the foregoing claims, wherein the hub also defines, along its outer circumference, the raceways for the wedging elements and for roller bearing elements.

7. A piston compressor according to any of the foregoing claims, wherein the freewheel comprises an inner camming or wedging surface and, between projections of this wedging surface, there are situated cylindrical rollers which serve as wedging elements.

8. A piston compressor according to any of the foregoing claims, wherein the freewheel roller bearing assembly comprises an outer race with a cylindrical inner circumferential surface which is common to the roller bearing elements and to the wedging elements.

9. A piston compressor according to any of the foregoing claims, wherein the drive wheel comprises a driving rim which is fixed to, and is rotatable with, a separate outer race of the freewheel roller bearing assembly.

10. A piston compressor according to any of the foregoing claims, wherein said annular space accommodates roller bearings and is filled with a full complement of cylindrical rollers, which constitute the roller elements.

11. A piston compressor according to any of claims 1 to 9, wherein the annular space of the freewheel roller bearing assembly accommodates ball bearings.

12. A piston compressor constructed and adapted to operate substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.