GB2047809A - Lubricating-oil gear pump for an I.C. engine - Google Patents

Abstract

The pump comprises an internally-toothed gear outer gear (3) meshing with an externally-toothed inner gear (4) in a chamber (5) formed by a housing (1) and a cover (2). A crescent-shaped piece (7) fills the space between the gears. The housing has a suction pocket (8) and a pressure pocket (9) separated from each other by a web (10). The cover has an annular groove (23) and the inner gear is provided on an inner bearing surface (17) with a chamfer (21) which in conjunction with the housing forms an annular chamber (22), the said chamber and groove being fed with oil through a groove (25) in the pressure pocket and a groove (24) in the web, respectively. The oil in the said groove and chamber reduce friction and obviate ingression of air. Recesses (27 to 30), Fig. 3 (not shown), may be formed in the housing and the cover to further reduce friction. <IMAGE>

Description

SPECIFICATION Lubricating oil pump for vehicle engines The invention relates to lubricating oil pumps for internal-combustion engines.

One known oil pump of this type has a pump chamber constituted by a cavity in a pump housing and closed by a lateral cover, in which an internally toothed, externally mounted external gear meshes with an externally toothed internally mounted internal gear arranged eccentrically thereto. The gear is arranged co-axially to a shaft of the internalcombustion engine and drivingly connected to the latter. A crescent-shaped packing piece is arranged opposite the region of engagement in the pump chamber and, laterally in the pump housing, considered in the direction of rotation of the gears, a suction pocket is constructed in front of and a pressure pocket behind the packing piece, being mutually separated by a web in the region of engagement.

A pump of the type initially mentioned is disclosed in German Patent Publication No. DOS 1576345. In a known lubricating oil pump of this type it was difficult to seal satisfactorily, especially the internal gear arranged concentrically to the shaft of the internal-combustion engine. It was necessary to accept that air was sucked into the lubricating oil along the check surfaces of the internal gear in the region of the suction pocket and that pressure oil was lost in the region of the pressure pocket along the check surfaces of the internal gear. This admixture of irto the lubricating oil and the loss of lubricating oil presented no particular problems for the normal supply of lubricating oil to an internalcombustion engine.

It has been discovered in the case of such a known lubricating oil pump that a considerable friction power was consumed by the lubricating oil pump during its operation due to the comparatively large plane check surfaces on both sides of both gears and also by the large cylindrical check surface of the external gear.

According to the present invention, there is provided a lubricating oil pump for internal-combustion engines, wherein an internally toothed, externally mounted external gear meshes in a pump chamber constituted by a cavity in a pump housing and closed by a lateral cover with an externally toothed internally mounted internal gear arranged eccentrically thereto which is arranged co-axially to a shaft of the internal-combustion engine and drivingly connected thereto and wherein a crescent-shaped packing piece is arranged in the pump chamber opposite the region of engagement, and laterally in the pump housing considered in the direction of rotation of the gears a suction pocket is constructed in front of and a pressure pocket behind the packing piece, mutually separated by a web in the region of engagement, characterised in that the cover is provided on its plane check surface for the internal gear with a concentric pressure oil groove and the internal gear is provided on its internal bearing circumference with a chamfer which in conjunction with the pump housing forms a concentric pressure oil chamber and said pressure chambers are loaded with pressure oil through a radial groove with the pressure pocket or through an appropriately radial groove in the web immediately behind the pressure pocket.

Preferabiy the cover is provided on its plane check surface for the internal gear with a concentric pressure oil groove which is connected by a radial groove to the pressure pocket and the internal gear is provided on its bearing circumference with a chamfer which in conjunction with the housing constitutes a concentric pressure oil chamber which is loaded with pressure oil through an approximately radial groove in the web immediately behind the pressure pocket. The pressure oil carried through the concentric pressure oil groove or the concentric pressure oil chamber into the region of the suction pocket reliably prevents the suction of air into the lubricating oil. Furthermore, the inherently difficult lubrication of the internal bearing circumference of the internal gear is substantially improved by the pressure oil supply through the concentric pressure oil chamber.

Advantageously, the lateral plane check surfaces for the internal and external gears are kept to a minimum dimension by recesses in the housing and in the cover, a considerable reduction of the friction power consumed by the lubricating oil pump is achieved.

A further reduction in the friction power of the lubricating oil pump is achieved by the fact that the outer cylindrical bearing surface for the external bearing circumference of the external gear is reduced by recesses, e.g., to three bearing webs distributed on the circumference.

The grooves for the supply of pressure oil into the concentric pressure oil groove or the pressure oil chamber may optionally also be constituted in the form of corresponding radial enlargements of the laterial recesses in the housing and in the cover.

It was only due to the. measures according to the invention, which permit a reliable sealing and lubrication of the internal gearofthe lubricating oil pump, that it was possible for the measures which produce the desired reduction of the friction power of the lubricating oil pump to be performed.

The invention is explained more fully hereinbelow with reference to an exemplary embodiment illustrated in the accompanying drawings, wherein: Fig. 1 shows a view ofthe lubricating oil pump according to the invention from its cover side; Figure 2 shows a section made along the line ll-ll in Figure 1; Figure 3 shows a view of the housing interior in the direction of the arrow Ill in Figure 2; Figure 4 shows a view of the cover interior in the direction of the arrow IV in Figure 2.

Figures 1 and 2 illustrate a lubricating oil pump for internal-combustion engines which is substantially constituted by a pump housing 1, a cover 2 and two mutually meshing gears, an external gear3 and an internal gear 4.

In the pump housing 1 there is formed a chamber 5 in which the internally toothed externally mounted external gear 3 is arranged in mesh with the exter nallytoothed internally mounted internal gear4 arrranged eccentrically thereto.

The pump chamber 5 is provided with a crescentshaped packing piece 7 in its region opposite the region of engagement 6 of the two gears. In the pump housing 1 there are formed at the side of the pump chamber 5, considered in the direction of rotation of the gears 3 and 4 of the lubricating oil pump designated by the arrow R, a suction pocket 8 in front of and a pressure pocket 9 behind the packing piece 7, which are mutually separated in the region of engagement 6 by a web 10.

The lubricating oil pump is provided on the pump housing 1 with various connection parts by which it can be connected to the internal-combustion engine.

Thus the pump housing 1 can be connected by a flange 11 to the engine block (not shown) and by a flange 12to a lubricating oil suction pipe (also not shown). An outlet channel 13 leading from the pressure pocket 9 into the flange 11 in the pump housing 1 establishes the connection to the lubricating system of the internal-combustion engine. An inlet channel 14 formed in the pump housing 1 and leading from the suction pocket 8 to the flange 12 establishes the connection to the lubricating oil sump of the internal-combustion engine.

A pressure relief valve (not shown) and arranged in the pump housing 1 causes pressure oil to be discharged through a bypass pipe 15 in case of need.

The driving connection of the lubricating oil pump to the shaft of the internal combustion engine (not shown) is effected through the flattened central recess 16 of the internal gear 4. The connection between the shaft of the internal-combustion engine and the internal gear4 is chosen so that radial and axial displacements of the shaft of the internalcombustion engine dictated by thermal expansion and by tolerances have no influence upon the internal gear 4. The central recess 16 of the internal gear 4 merely ensures a driving connection.

The internal gear4 is otherwise mounted in the pump housing 1 by its internal bearing circumference 17. In similarmannerthe external gear3 is mounted in the pump housing 1 by its external bearing circumference 18.

The two mutually meshing gears 3 and 4 slide by their lateral surfaces against a plane check surface 19 in the pump housing 1 on the one hand and against a plane check surface 20 on the cover 2 on the other hand.

The internal gear 4 is provided on the side of its bearing circumference 17 confronting the pump housing 1 with a chamfer 21 which in conjunction with the pump housing 1 constitutes a concentric pressure oil chamber 22. A concentric pressure oil groove 23 is constructed on the check surface 20 of the cover 2 slightly within the root circle diameter of the internal gear 4. The pressure oil chamber 22 and the pressure oil groove 23 are loaded with pressure oil from the region of the pressure pocket 9, firstly through an approximately radial groove 24 in the web 10 immediately behind the pressure pocket 9, and in the other case through a radial groove 25 approximately in the centre of the pressure pocket 9.

The arrangement of the suction and pressure poc kets 8 and 9, the position of the pressure oil chamber 22 and the position ofthe groove 24 may be seen from figure 3, which shows a view of the pump hpusing interior, in which however the gears 3 and 4 have been shown by dash lines for better comprehension.

The arrangement of the concentric pressure oil groove 23 and the position of the radial groove can best be seen from figure 4, which shows a view of the cover interior in which the gears 3 and 4 have been shown by dash lines for better comprehension.

By the loading of the pressure oil chamber 22 and of the concentric pressure oil groove 23 with pressure oil from the region of the pressure pocket 9 and groove 24, it is ensured that no air is sucked into the lubricating oil by the negative pressure prevailing in the region of the suction pocket 8. This is essential, particularly for those cases of application of a lubricating system of internal-combustion engines where hydraulic tappets connected to the lubricating oil circuit of the internal-combustion engine are used in the valve gear of the internal-combustion engine.

Furthermore a substantially better lubrication of the internal bearing circumference of the internal gear 4 is achieved, whereby pitting and wear phenomena which occasionally occur here are prevented and operational reliability and service life are thereby improved.

Figure 3 and 4 illustrate two further measures which reduce the friction power necessary for the operation of the lubricating oil pump. The first of these measures consists in recesses 27 and 28 in the marginal region of the pressure and suction pockets 9 and 8 and a recess 28 in the region opposite the web 10, shown as half-tone surfaces and arranged on the lateral plane check surfaces 19 and 20 forthe gears 3 and 4 on the one hand, and by recesses 30 shown as half-tone surfaces and located in the cover 2 correspondingly opposite the recesses 27,28 and 29 in the pump housing 1 on the other hand.

The second measure consists in a reduction of the external cylindrical bearing surface for the external bearing circumference 18 of the external gear3 in that the latter is reduced by recesses 31 shown as hatched areas to three bearing webs 32 distributed on the circumference.

The arrangement of the removal grooves for the pressure oil required to seal and improve the lubrication of the internal gear may in principle be effected at any point of the pressure region of the pump.

Likewise the arrangement and position of the lateral recesses and the arrangement of the bearing webs distributed on the circumference is not restricted to the exemplary embodiment illustrated, but may be varied according to operational require ments having regard to the correct mode of function ing of the pump.

The friction power necessary for the operation of the lubricating oil pump is reduced by these two measures, resulting firstly in a prolonged useful life of the lubricating oil pump due to reduced wear, and secondly to an improvement of the overall efficiency of the internal-combustion engine.

Claims (5)

1. Lubricating oil pump for internal-combustion engines, wherein an internally toothed, externally mounted external gear meshes in a pump chamber constituted by a cavity in a pump housing and closed by a lateral cover with an externally toothed internally mounted internal gear arranged eccentrically thereto which is arranged coaxially to a shaft of the internal-combustion engine and drivingly connected thereto and wherein a crescent-shaped packing piece is arranged in the pump chamber opposite the region of engagement, and laterially in the pump housing considered in the direction of the gears a suction pocket is constructed in front of and a pressure pocket behind the packing piece, mutually separated by a web in the region of engagement, characterised in that the cover is provided on its plane check surface for the internal gear with a concentric pressure oil groove and the internal gear is provided on its internal bearing circumference with a chamfer which in conjection wth the pump housing forms a concentric pressure oil chamber and said pressure chambers are loaded with pressure oil through a radial groove with the pressure pocket or through an approximately radial groove in the web immediately behind the pressure pocket.

2. A lubricating oil pump according to Claim 1, characterised in that the lateral plane check surfaces for the internal and external gears are kept to a minimum dimension by recesses in the pump housing and by recesses in the cover.

3. A lubricating oil pump according to Claim 1 or 2, characterised in that the external cylindrical bearing surface for the external bearing circumference of the external gear is reduced to bearing webs distributed on the circumference by recesses.

4. A lubricating oil pump according to any one of Claims 1 to 3 characterised in that the grooves for supplying the pressure oil chamber and the concentric pressure oil groove are constituted by radial enlargements of the recesses in the pump housing and of the recess located in the region of the pressure pocket in the cover.

5. A lubricating oil pump substantially as hereinbefore described, and as illustarted in the drawings.