GB2286017A

GB2286017A - Improvements relating to pumps

Info

Publication number: GB2286017A
Application number: GB9401089A
Authority: GB
Inventors: Steve Hodge
Original assignee: Concentric Pumps Ltd
Current assignee: Concentric Pumps Ltd
Priority date: 1994-01-21
Filing date: 1994-01-21
Publication date: 1995-08-02
Also published as: JPH07259751A; EP0664378A1; KR950023857A; NO950195D0; NO950195L; WO1995020099A1; BR9500270A; GB9401089D0; FI945874A0; FI945874A

Description

C- 1 1 1 IMPROVEMENTS RELATING TO PUMPS 2286017 This invention relates to

oil pumps for I.C. engines. Such pumps are engine driven, and as such, the pturip output is nominally proportional to engine speed.

Now as the engine demand curve for oil pressure is not normally proportional to enfbine speed, a quantity of oil in excess of that needed to maintaiii the bearing pressure is diverted to the sump via a control valve mechanism. If this were not so, the result would be excessive pressures causing possible engine damage. This excessive oil represents wasted energy. Many prnposals have attempted to deal with this prol)"ieril for example by using a gerotor pump and varying tile eccentricity of the axes so as to reduce output at higher speeds. The object of the invention is to provide a new solution to this old problem.

According to the invention, an engine oil pump comprises a drive shaft connected to a pair of pumps J_ having a common inlet supply and separate but connected outlets, includin. c a diverter valve in one of the outlets effective to return oil frora the corresponding pump 0 direct to supply at higher delivery rates/pressures.

According to a preferred version of the invention, an engine oil pump coitiprises a drive shaft connected to a pair of gerotor oil pumps having their inlets connected to a common supply, and thei.r outlets connected to a common delivery passage, and wi.th a control valve located between one ofe the outlets and the delivery passage arranged to divert oil from one of the gerotor sets to tile coinmon supply when the valvP is open, and with the valve arranged to open automatically at Inigher pressures/delivery rates.

The valve may be a simple spring controlled valve. When the pump output pressure is low, the valve remains closed and all output -oes to the deli. very passage. As 0 t pressure rises, nrL,-,iarily with speed nf the en-ine, but n Z possibly also due to reduction in viscosity as in the case of low temperatures the valve opens and allows some and then all of the output from the one gerotor set to bypass the delivery passage and return directly to the supply source, for example the sump.

The power utilization of the gerotor set depends upon the outlet pressure: hence by connecting the outlet direct to sump the pressure is effectively zero so that the workload on the pump is relieved and the gerotor set in question uses ininimal energy at such time.

01 Gerotor pumps are well understood in the art and comprise a male lobed rotor with n lobes located in a feniale lobed annulus havina n+l lobes. This forms a series of chambers between the rotor and annulus, each bounded by the pump body in planes normal to the axis of rotation and also bounded by the lines of contact between the parts. As the rotor and annulus rotate albeit at different speeds, the chambers revolve about the axes (the rotor and annulus are on parallel not coincident axes) and vary in size. They increase in one half revolution from the minimum where a lobe on one part is located midway between two lobes on the other part to a maximum at a point diametrically opposite, and as they increase they move over the inlet port. In the second and subsequent half revolution the chambers decrease in size and move over the outlet port leading to the delivery passage.

The accompany diagrammatic drawings show a preferred arrangement in the fall flow, i.e. both pumps operative 1 L 0 pos2tion in Fi-ure 1 and in the low flow, one pump operative Position in Figure 22. In the drawings, the drive shaft 10 extends through and is angularly fast with til-le rotor of each of two Serotor pumps -Indicated by the refe-rence numerals 12-, 14. The comi-tion inlet passage 16 is connected to boLii pumps. Outlet passage 108 from pump 121is connected to the delivery passage '40 leading. to for example the inain oil gallery of the engine.

The ontlet passage 2.2 the pump 14 extends to a 1\ 3 sump, that is the same source of supply as the inlet 16, with a pair of connection passages 24 26 extending from the passage 22 to the passage 18.

Passa.e 24 communicates pressure from outlet 18 to act upon the control valve 28 which may be spring urged at 30 to the closed position illustrated in Figure 1. this position ball valve 32 in passages 26 is open allow flow from passage 22 via 26 to the outlet 20. passages are effective to deliver oil to the engine both pumps absorb energy.

to Both and When the pressure rises in passage 18 it can overcome the spring 30, the valve 28 moves to open the path in passage 22 direct to the sump, and the ball valve also seats so that there is no flow between passages 18 22 in either direction and the one pump delivers to the engine and the other pump delivers back to the sump. At this time pump 14 uses but little energy.

!.-- 1 : I# 4

Claims

1. An engine oil pump comprising a pair of pumps driven from a common drive shaft, having a common inlet supply and connected but separate outlet passages including a diverter valve in one of the outlets effective to return oil from the corresponding pump direct to supply avoiding the lubricant delivery passage unless the valve is in a closed position.

2. An engine oil pump comprising a drive shaft connected to a pair of gerotor oil pumps having their inlets connected to a common supply, and their separate outlets connected to a common delivery passage, and with a control valve located in between one of the outlets and the delivery passage arranged to divert oil from one of the gerotor sets direct to the common supply when the valve is open.

3. A pump as claimed in Claim 2 wherein the valve is arranged in the outlet line from one of the pumps to be operated by pressure in the outlet line from the other of the pumps.

4. A pump as claimed in Claim 2 and Claim 3 wherein the outlet line from one pump is connected to the delivery passage, the outlet line from the other pump is connected to the inlet source or line, and a pair of passages connect the two lines, one containing a diverter valve for operation by pressure in the other line, and the other containing a ball check valve.