GB2349425A

GB2349425A - Internal geared wheel pump with play compensation in the keyed drive region

Info

Publication number: GB2349425A
Application number: GB0007130A
Authority: GB
Inventors: Frank Lantermann
Original assignee: Deutz AG
Current assignee: Deutz AG
Priority date: 1999-03-29
Filing date: 2000-03-23
Publication date: 2000-11-01
Anticipated expiration: 2020-03-23
Also published as: DE19914167A1; DE19914167C2; GB0007130D0; GB2349425B

Abstract

An internal geared wheel pump for the delivery of fluids, with an inner rotor (2) seated on a drive shaft (1), whereby drive keys (3) set into the drive shaft (1) lie against edges (4) of the inner rotor (2) and drive it. At least one plastics material element (6) is arranged between the drive shaft (1) and the inner rotor (2), allowing play between the drive keys (3) and the plastics material element (6) in a cold condition of the pump to facilitate assembly, the play being less than the thermal expansion of the length of the plastics material element (6) in the operation of the internal geared wheel pump so that, in use, the element (6) heats up and undergoes an expansion in its length, reducing play in the keyed drive region.

Description

2349425 Internal geared wheel pump with play compensation in the drive

region The invention relates to an internal geared wheel 5 pump for the delivery of fluids with an inner rotor seated on a drive shaft, whereby drive keys set into the drive shaft lie against edges of an inner rotor and drive it.

An -internal geared wheel pump, also called an Eaton 10 pump, is known from "Die verbrennunungskraftmaschine", Springer -Ve rlag, Wien, 1964, Vol 11, pp 95,96.

The pump works in accordance with the compression principle and comprises an outer and an inner rotor. The outer rotor is toothed internally with circular shaped tooth edges, which form the generating function for the tooth form of the inner rotor. The inner rotor, which sits on the drive shaft, has one tooth fewer than the outer rotor. The two rotors engage each other continuously with all the teeth at the rolling point. The centre point of the inner rotor is displaced eccentrically to the outer rotor by half a tooth depth.

In the movement of the rotors the pump spaces are continuously increased on the suction side, whilst on the compression side the process is reversed.

In modern self igniting internal combustion engines (Diesel motors) internal geared wheel pumps are known to be used as lubricating oil pumps. The lubricating oil pump is driven directly from the crankshaft. To this end, drive keys are set into the drive shaft of the the sides in-e-nal geared wheel pump, which!-e against of the inner rotor and drive it.

For tolerance and assembly reasons the radial crankshaft drive key play amounts to some 1-5'- Because of torsional vibration in the crankshaft and ignition culsing of the cylinder nearest to tle oil pump the drive keys lift in operation frorr, the driving edges of the crankshaft cut-outs and impact upon the rearward edges, thus running through the available playAs a consequence of the relative movement--s of the rotor, there arise metallic rattling _10 4 ses, wear on the drive keys and in individual cases (decending on the torsional vibration resonance situation), even rotor breakages.

The invention therefore has the aJ_m of producing an I internal geared wheel pump according to the opening paragraph of the present specification, with compensat-ion or play in the drive region.

In accordance with the present invention, this aim is addressed in that at least one element is arranged between the drive shaft and the _.nner rotor in the direction of rotation to 14 1 e with play on the drive keys with the internal geared wheel pump at a standstill, and that the play is less than the Iiinear expansion of the t in length of the elemen J_ the operation of the internal geared wheel pump.

This gives the advantage tnat at a standstill, that is in the cold condition of the internal geared whee-L y 4 S pump, easy assembl possibie because of the play. In operation of the internal geared wheel pump the element heats up and thereby undergoes an expansion in its lenat h, whereby the existing play is automatically compensated.

In a preferred embodiment the element is a plastics material element and two plastics material elements lie with play against the drive keys on both sides with the internal geared wheel pump at a standstill, that is the drive keys are enclosed in the circumferential direction by the plastics material ei-ements. More than two plastics material elements and drive keys can be provided, to correspond with the individual requirements. The number depends on the power to be transmitted (Moment) and the expansion in length, that is a sufficient surface should be available for the compensation of the play.

Advantageously the plastics material elements completely cover the drive shaft completely up to the drive keys.

it is expedient to arrange two drive keys diametrically oppos ite one another on the drive shaft and to border these with two plastics material elements which are semi-circularly shaped in section.

The plastics material elements comprise advantageously PA (polyamid) or P E (polyethylene).

However, any plastics material or even a non-plastics material can be used, which has a significantly greater coefficient of linear expansion than steel.

For assembly reasons the plastics material elements are p-referably fastened to the 4 nner rotor, for example they may be vulcanised on.

In a preferred embodiment the drive keys are disc sp-rings.

Advan-cageously, the fiu-id delivered by the internal geared wheel pump is an oil, especially lubricating o-J-1.

The internal geared wheel pump may be used as a lubricating 0 11 pump L or a self-igniting internal combustion engine.

The drive shaft is preferably +the crankshaft of the internal combustion engine.

Parts of an example of a pump embodying the present invent-;on wiil now be described with reference to the accompanying drawing, the single Figure of which shows a _'L'5 cross-sect-iona, view of those parts.

In the Figure, a drive shaft I of an in--ernai geared wheel pump has an inner rotor 2 assembled on it. The pump s used as the lubricating oil pump of a seif igniting internal combustion engine. The drive shaft I is thereby the crankshaft of the internal combustion engine. The direction of rotation is shown by the arrow S.

Ti-le inner rotor 2, which is driven by the drive shaft I is keyed onto the drive shaft 1 con-centrilcallily. The other parts of the internal geared wheel pump, such as the outer rotor and the housing, are not shown, but, however, represent the state of the art.

To drive the inner rotor 2 (and possibly also several re I inner rotors) two or more drive keys 3 a- set into the drive shaft diametrically and each lies on an edge 4 of the inner rotor. These drive keys are disc springs, which are set into cut- outs in the drive shaft 1. Between the drive shaft 1 and the inner rotor 2 are arranged two plastics material elements, which are semicircular in section, and which are vulcanised onto the inner rotor 2. Two positions, at which the plastics material elements are vulcanised on, are, for instance, identified with the reference character 7. Other fastening processes can be utilised.

The plastics material elements 6, when the lubricating oil pump is at a standstill, that is with cold lubricating oil, lie with play against the drive keys 3. This cold play is necessary for the assembly of the inner rotor 2 onto the drive shaft 1.

On starting the internal combustion engine the lubricating oil is very viscous, that is it has a higher viscosity than in the hot operating condition. The lifting of the drive key 3 from the edge 4 is thereby prevented. This is the case up to an oil temperature of approximately 115'C.

Since the plastics material elements (for example PA or PE) has a greater coefficient of linear expansion -than the surrounding steel of the drive shaft 1 and of the inner rotor 2, there occurs with rising temperature an increasing compensation of the play, until at operating temperature complete compensa t 4 on has taken place. At high oil temperatures and therefore with high component -emperatu-res -he drive keys can no lonaer detach from the edges 4. Any ret--irn impacting on the opposite edges is sim-41arly prevented, whereby an automatic com)ensation of the play is ef-fected.

Claims

Claims:

1. An internal geared whee-I pump for the delivery of fluids with an inner rotor seated on a drive shaft, whereby drive keys set into the drive shaft lie against edges of an inner rotor and drive it, in which at least one element is arranged between the drive shaft and the inner rotor in the direction of rotation to lie with play on the drive keys with the internal geared wheel pump at a standstill, and that the play is less than the linear expansion of the element in the operation of the internal geared wheel pump.

2. An internal geared wheel pump according to claim 1, in which the element is a plastics material element and in which two plastics material elements lie with play against the drive keys on both sides with the internal geared wheel pump at a standstill.

3. An internal geared wheel pump according to claim 1 or claim 2, in which the plastics material elements cover the drive shaft up to the drive keys.

4. An internal geared wheel pump according to any preceding claim, in which two drive keys are arranged diametrically on the drive shaft and border two plastics material elements which are semi-circularly shaped in section.

S. An internal geared wheel pump according to any preceding claim, in which the plastics material elements are fastened to the inner rotor.

6. An intrernal geared wheel pump according to claim 5, in which the plasics material elements are vulcanised on to the inner rotor.

7. An internal geared wheel ymmp according to any preceding claim, in which the drive keys are disc S springs.

8. An internal geared wheel T"nq according to any preceding claim, in which the fluid de-ivered is oil, especially lubricating oil.

9. An internal geared wheel pump according to any 10 preceding claim, for use as a lubricating oil pump for a self igniting internal combustion engine.

10. An internal geared wheel pump according to any preceding claim, in which the drive shaft is the crankshaft of the internal combustion engine.

11. An internal geared wheel pump substantially as described hereinbefore with reference to and as illustrated in the only Figure of the accompanying drawing.