GB2118628A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

In a Roots-type compressor for e.g. i.C. engine supercharging, gears 38, 40 interconnecting the rotors 12, 14 are secured to the rotor shafts 16, 18 frictionally with the aid of nuts 42, 44 so as to facilitate accurate angular location of the rotors. A special tool may be employed to establish the correct locations of the rotors and hold them thereat until the gears have been secured, Figures 2 and 3. <IMAGE>

Description

SPECIFICATION Roots-type rotary volumetric compressor and a tool for use in assembling the compressor The present invention relates to a Roots-type rotary volumetric compressor including two contra-rotating rotors with shafts which carry two meshing gear wheels for transmitting rotation from one shaft to the other.

In conventional compressors of this type, the two gear wheels are normally keyed to their respective shafts by means of prismatic couplings.

These prismatic couplings must, of necessity, be formed very precisely, by means of accurate working which requires complicated and expensive equipment, in order to obtain the correct phasing between the two rotors and the two gear wheels.

The object of the present invention is to provide a compressor of the type specified above which is simpler and more economical to manufacture and allows a more precise phasing to be achieved between the two rotors and their gear wheels during assembly.

In order to achieve this object, the present invention provides a rotary volumetric compressor of the type defined initially, characterised in that the two gear wheels are freely rotatably mounted on the shafts of the two rotors, and in that friction locking means are provided for rendering the gear wheels rigid with their respective shafts for rotation.

This characteristic allows precise phasing between the rotors and the two gear wheels to be achieved simply and rapidly during assembly of the compressor, without requiring the accurate and complicated keying of the latter onto their respective shafts. In fact, during the assembly of the compressor, it suffices, before the friction locking of the two gear wheels, to place one of the latter in the correct angular position relative to the other while retaining the two rotors in their corresponding predetermined relative angular positions. The assembly of the compressor is then completed simply by tightening the friction locking means so as to couple the gear wheels to their respective shafts for rotation.

Preferably, each of the gear wheels is interposed between two axial retaining members mounted on the respective rotor shaft, one of which is fixed axially and the other of which is movable axially, and the axially movable retaining member is associated with a screw-threaded locking member which is screwed onto corresponding threading on the shaft to clamp the gear wheel between the two axi.al retaining members The invention also relates to a tool for use in the assembly of the compressor defined above, which is particularly simple, practical and functional.

The invention will now be described in detail with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is a partially sectioned axial view of a rotary volumetric compressor according to the invention; Figure 2 is a view similar to Figure 1 illustrating part of the compressor of Figure 1 during assembly, and Figure 3 is a side elevational view along arrow Ill of Figure 2.

Referring initially to Figure 1, a Roots-type rotary voiumetric compressor, generally indicated 10, is intended for the supercharging of an internal combustion engine for motor vehicles. The compressor 10 includes a casing 11 within which are rotatably mounted two double-lobed rotors 1 2, 1 4 of known type, the respective shafts 1 6, 1 8 of which are supported for rotation by a pair of heads 20, 22 fitted sealingly to opposite ends of the casing 11. Respective removable covers 26, 28 are connected to the two support heads 20, 22.

The ends of the two shafts 1 6, 1 8 adjacent the cover 28 are supported for rotation in the corresponding head 20 by means of respective rolling bearings 30, 32, the inner rings 30a, 32a of which bear axially against respective spacers 34, 36 abutting the two rotors 12, 14 facially.

Two gear wheels 38, 40 of equal diameter are mounted on the shaft 16 and the shaft 18 respectively, and are meshed together. Each gear wheel 38, 40 is interposed between the inner ring 30a, 32a of the respective rolling bearing 30, 32 and a clamping nut 42, 44 and washer 46, 48 screwed onto a threaded portion 50, 52 of the respective shaft 1 6, 18. The two gear wheels 38, 40 are locked with the shafts 1 6, 1 8 for rotation by means of a simple friction coupling between the inner rings 30a, 32a and the washers 46, 48 which is achieved by tightening the two nuts 42, 44. This locking is effected manually by means of an ordinary spanner for nuts and bolts, after the rotors 12, 14 and the gear wheels 38, 40 have been brought into phase in a manner which will be explained below.

The end of the shaft 1 8 opposite the cover 26, indicated 18a, passes sealingly through the cover 28 and carries a pulley 54 connectible, by means of a cogged belt, to a drive member constituted, for example, by the shaft of the engine with which the compressor 10 is associated or by the camshaft of this engine. The pulley 54 is locked torsionally to the end 1 8a of the shaft 18 by means of a nut 56 and washer 58 screwed onto terminal threading 1 8b of the shaft 1 8.

Figures 2 and 3 illustrate a tool according to the invention usable during assembly of the compressor 10 to achieve precise and accurate phasing af the two rotors 1 2, 14 and the gear wheels 38, 40. The tool, generally indicated 60, comprises essentially a support platform 61 having two parallel spaced-apart walls 62, 64 the first of which is provided with centering and retaining members 65 for the support head 20 and the other of which is provided with a bush 66 for supporting rotatably the respective ends 1 6a, 1 8c of the shafts 1 6, 1 8 opposite the head 20.

The wall 62, which is fixed to the platform 61 by means of a pair of lateral reinforcing flanges 70 and has a central aperture 67, supports a pair of jaw-like positioning members, generally indicated 72, 74 respectively, the frist of which is located on the side of the wall 62 opposite the platform 61 and the other of which is located on a side by one of the lateral flanges 70. Each of the positioning members 72, 74 includes a screw-and-nut operating member 76, 78 for effecting, through a wheel 80, 82, the manual movement of a shaft 84, 86 carrying a body 88, 90 with a cradleshaped end 92, 94. The bodies 88, 90 are guided in respective guide structures 96, 98 and are slidable axially in two mutually perpendicular directions A, B.

The wall 62 also supports, on the side of the lateral flange 70 opposite the positioning member 74, a reaction member 100 including a screw and-nut operating device 102 with an operating wheel 104 for moving a shaft 106 carrying a body 108 with a cradle-shaped end part 110. The operation of the device 102 effects the axial displacement of the body 108 in a direction C parallel to the direction of displacement B of the body 90 of the positioning member 74, and hence perpendicular to the direction of displacement A of the body 88 of the positioning member 72.

The operation of the tool 60 during the assembly of the compressor 10 will now be described.

Before the assembly of the casing 11 and the support head 22, the unit constituted by the two rotors 12, 14 mounted in the support head 20 with their respective shafts 1 6, 1 8 is positioned on the tool 60 by the insertion of the two rotors 12, 14 through the aperture 67 until the ends 16a, 1 8c of the shafts 1 6, 18 are engaged in the bush 66, and the support head 20 is locked with the outer face of the wall 62 in the manner illustrated in Figure 2. Thus, the two rotors 1 2, 1 4 extend between the two walls 62, 64 with their shafts 16, 18 parallel to the platform 61, that is, perpendicular to the directions of displacement A, B, C of the two positioning members 72, 74 and the reaction member 100.At this stage, at least one of the locking nuts 42, 44 is kept in its loose condition so that at least one of the gear wheels 38, 40 is freely rotatable on its respective shaft 16,18.

Subsequently, the two rotors 12, 14 are disposed manually in the position clearly illustrated in Figure 3, that is, with the major axis D of the rotor 12 arranged perpendicular to the platform 61 and the major axis E of the rotor 14 parallel to this platform 61, that is, perpendicular to the major axis D. At this point, the wheels 80, 82, 104 are operated so as to bring the cradle part 92 into engagement with the lobe of the rotor 12 opposite the rotor 14, and the cradle parts 94, 110 into engagement with the two lobes of the rotor 14. In this way, the two rotors 12, 14 are positioned precisely and firmly, the major axes D, E being aligned respectively with the directions of displacement A, B of the two positioning members 72,74.

At this stage, the relative angular positions of the two gear wheels 38, 40 are adjusted and, finally, the nuts 42, 44 are tightened so far as possible to render these gear wheels rigid with their respective shafts 1 6, 1 8 for rotation.

Once this operation has been completed, the support head 20 with the rotors 12, 1 4 is removed from the tool 60 and the assembly of the compressor 10 is completed by the assembly of the casing 11 , the support head 22, and the pulley 54.

Naturally, the principle of the invention remaining the same, the constructional details and forms of embodiment of the compressor and the tool usable for its assembly may be varied widely with respect to that described and illustrated, without thereby departing from the scope of the present invention.

Claims (6)

1. A roots-type rotary volumetric compressor, including two contra-rotating rotors with shafts which carry two meshing gear wheels at one end for transmitting rotation from one shaft to the other, characterised in that the two gear wheels (38, 40) are freely rotatably mounted on the shafts { 16,18) of the two rotors (12,14), and in that friction locking means (42, 46, 30a; 44, 48, 32a) are provided for rendering the gear wheels (38, 40) rigid with their respective shafts (16, 18) for rotation.

2. A compressor according to Claim 1, characterised in that each of the gear wheels (38, 40) is interposed between two axial retaining members (30a, 46; 32a, 48) mounted on the shaft (16,18) of the respective rotor (12,14), one of which is fixed axially and the other of which is movable axially, and in that a screw-threaded locking member (42, 44) is associated with the axially movable retaining member (46, 48) and is screwed onto corresponding threading (50, 52) on the shaft (1 6, 18) to clamp the gear wheel (38, 40) facially between the two axial retaining members (30a, 46; 32a, 48).

3. A tool for use in the assembly of a Rootstype volumetric rotary compressor according to the preceding claims and having the ends of the shafts of the two rotors supported for rotation by two lateral support heads which are fixable sealingly to a casing of the compressor, characterised in that it comprises:: - a support (61) having two parallel spacedapart walls (62, 64) for supporting the shafts (1 6, 18) of the two rotors (12, 14) rotatably prior to their insertion into the casing (11) of the compressor (10), one of which is provided with means (65) for positioning and locking that head (20) of the compressor which supports the ends of the shafts (16, 18) carrying the two gear wheels (38, 40) for rotation, so as to allow access to the friction locking means (42, 44) of the gear wheels (38, 40) from the exterior, and - a pair of jaw-like positioning members (72, 74) movable in directions (A, B) perpendicular to the shafts (16,18) of the two rotors (12, 14) during use of the tool, the positioning members (72, 74) being provided with respective cradle parts (92, 94) for engaging a respective rotor (12, 14) peripherally and for locking the rotors in a predetermined relative angular position.

4. A tool according to Claim 3, for use in the assembly of a compressor the rotors (12,14) of which have a double-lobed cross-section with a major axis and a minor axis, characterised in that the directions of displacement (A, B) of the two positioning members (72, 74) are perpendicular to each other, and in that the cradle part (92, 94) of each positioning member (72, 74) is arranged to interact with one of the lobes of a respective rotor (12, 14) to clamp the rotors (12, 14) in a position in which their major axes (D, E) are aligned in the directions of displacement of the respective positioning members (72, 74).

5. A tool according to Claim 4, characterised in that it further includes a reaction member (100) movable parallel to the direction of displacement (B) of one of the positioning members (74) and having a cradle part (110) arranged to interact with the other lobe of the rotor (14) with which the positioning member (74) is intended to cooperate.

6. A tool substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.