Oil pumps

Abstract: Oil pump manufacture is simplified by providing the pump body with a planar unstepped face and achieving radial location by the provision of a bush 22 (Fig.2) on the pump driven shaft 14, which bush is received in the counterbore 24 of the part journalling the drive shaft 16, i.e. the cylinder block adjacent the end of the drive shaft (crankshaft).

Description: This invention relates to oil pumps such as gerotor pumps primarily for i.c. engines. In a typical layout, the drive shaft for the pump - which may be the nose of the engine crankshaft - has a central splined or slotted bore to receive the splined or tang end of the driven shaft in the pump. This driven shaft projects through a pump body face, and that face mates with the engine block/sump and alignment is achieved by a circular formation or step machined in said face and a complementary step formation on the pump body. Radially outwardly of the step the face is apertured for securing bolts. EP-A-0196469 shows a fuel feed pump driven by an electric motor in which the pump body or housing has a sleeve or cylindrical projection which is located in a bore in the casing on which the pump is mounted, in a generally similar fashion to that mentioned above. DE-A-3620705 shows an oil pump for an I.C. engine with the pump body fixed and located by unspecified means. A bush is keyed to the crank shaft and is angularly fast with the pump rotor to transmit drive directly to the rotor. The object of the invention is to simplify manufacture. According to the invention a pump for an I.C. engine of the kind in which the engine has a drive shaft connected to the internal rotor of the pump, and the pump body has a planar unstepped face clamped to the engine block is characterised in that a pump driven shaft is coaxially connected to the engine shaft, a bush journals said pump drive shaft in said body and said bush is located in a bore in said engine to locate the pump in a radial position determined by the bush. This eliminates one operation in machining the pump body. Conveniently the bush is one coated with or impregnated with a low friction material such as PTFE which is effective in the bore of the bush in order to journal the driven shaft. This driven shaft is usually a problem for lubrication, involving either a bleed of pumped lubricant or splash from the sump, both of which are unsatisfactory: thus the pumped lubricant is at this point (i.e. in the pump) unfiltered, because the lubricant circuit goes from pump to main filter and only then to points to be lubricated, so that if this bush is to be supplied with filtered lubricant, an extra delivery gallery is required duplicating the one from the pump to the filter, and simply returning a proportion to the pump shaft. That is considered to be an undesirable complication. The splash alternative primarily relies upon oil mist in the sump reaching the shaft, and is found in practice to be unreliable. The PTFE impregnated bush has been known per se for very many years but has never been used for this purpose, as far as is known to the inventor. The use is surprising and non-obvious. The combination of solving the lubrication problem for the oil pump driven shaft and use of the same bush to simplify pump body machining by providing location in use is an important advantage for the invention. The invention is now more particularly described with reference to the accompanying drawings wherein:- Figure 1 is a diagrammatic sectional elevation showing the prior art arrangement; Figure 2 is similar to Figure 1 but showing the invention. Turning first to Figure 1, the pump comprises a body 10 housing a pump set 12, in this example a gerotor set, and the body is provided with appropriate inlet and outlet ports for the lubricant to be circulated by the pump. The pump has a driven shaft 14 keyed or like angularly fast with a drive shaft 16 which may be the crankshaft of the engine, and the shaft is journalled in bush 21 in the body. In order to align the pump with the end of shaft 16, a recess or shoulder 18 which is precisely concentric with the shaft axis is machined in the part 20. The pump body has a complementary stepped face which is likewise precisely concentric to the shaft axis. In addition the pump body is provided with holes for bolts and the part 20 is likewise provided with screw tapped apertures to receive those bolts. Turning now to the invention in Figure 2, the pump body is made planar instead of being stepped, and the part 20 is likewise planar. The pump driven shaft 14 now has a bush 22 which is received in the bore 24 in order to align the shaft 14 with the shaft 16. The pump body is therefore self locating. It may be clamped in place by bolts passing through enlarged apertures in the pump body flange 26 and into screw-tapped apertures in the part 20 in the usual way.

Claims: An oil pump (10,12) for an i.c. engine, in which the engine has a drive shaft (16) connected to the internal rotor (12) of the pump and the pump body (10) has a planar unstepped face clamped to the engine block (20) characterised in that a pump driven shaft (14) is coaxially connected to the engine shaft (16), a bush (22) journals said shaft (14) in said body (10) and said bush is located in a bore in said engine (20) to locate the pump in a radial position determined by the bush. A pump as claimed in Claim 1 wherein said bush is coated or impregnated with low friction material.

Inventors: HODGE STEVE, HODGE , STEVE
Applicants: CONCENTRIC PUMPS LTD, CONCENTRIC PUMPS LIMITED
Application year: 1992
Main classification: F04C11
IPC codes: F04C2, F01M1, F04D29, F04C11