Oil pump system for a four-stroke engine

Field of invention

The present invention relates to an "Oil pump for a four stroke engine" and more particularly to oil pump which delivers the required quantity of lubrication oil to various parts present in a four stroke spark or compression ignited engine.

Background

Oil pump is one of the most important parts of an automotive engine, which ensures safe running of the engine even in heavy load conditions. An automotive engine consists of a number of rotating and reciprocating parts, which has to be properly lubricated during their operation. In conventional 4-stroke engine, the preferred method of lubrication is the "Wet sump lubrication", in which the lubricating oil stored in the sump is drawn in by an oil pump, pressurized and is supplied to the various rotating and reciprocating parts. In this lubrication system the oil pump is a significant member.

Most often the pump used is a positive displacement rotary pump such as Gerotor pump (Figure 1). The Gerotor pump consists of an 'outer rotorl' with internal gear teeth in mesh with an 'inner rotor2' with external teeth. Usually the number of teeth of the inner rotor will be one less than that of the outer rotor and the centre of the inner rotor is displaced from the centre of the outer rotor by an eccentric distance 'e'. Drive is given to the inner rotor through a drive shaft The inner rotor in turn drives the outer rotor by means of its gear teeth. As explained in the Figure 1, 'A' is a chamber confined by inner rotor gear teeth and outer rotor gear teeth. As the inner rotor rotates the volume of the chamber 'A' first increases reaches to a maximum value at position 'B' and then decreases and reaches to a minimum value at position 'C During the period of rotation, where the chamber volume increases, it is in communication with the inlet eyelid and when the chamber volume decreases, it is in communication with the outlet eyelid. The inlet eyelid is connected to the oil sump through a strainer, while the outlet eyelid is connected to the various rotating parts of the engine through an oil gallery. As the inner and the outer rotor rotate, the expanding chamber 'A' creates a vacuum, which sucks the oil from the oil sump through the inlet eyelid and oil strainer. During the next part of rotation, the chamber 'A' contracts, there by pressurizing the oil trapped within the chamber and delivering it to the rotating parts through the outlet eyelid and oil gallery.

This conventional Gerotor pump falls in the category of 'positive displacement pump', where the theoretical discharge from the pump varies linearly with the pump speed.

However the oil requirement by the various rotating and reciprocating parts of the engine does not vary linearly with engine speed. One of the most essential criteria for selection of an oil pump is that the actual discharge of the oil pump should be higher than or equal to the net oil requirement by all rotating and reciprocating parts at all engine speeds. So the typical method followed for pump selections is to calculate the net oil requirement by all rotating and reciprocating parts at the lowest engine rpm and full load and selecting the oil pump that gives the same oil output at that rpm. But at higher engine speeds such a pump will deliver more oil than what is really required and the excess oil must be send back to the sump through a pressure regulator. Energy consumed by an oil pump is directly dependent on the amount of oil pumped. Thus when there is excess pumping of oil, it eventually leads to wastage of energy and thus decreasing the overall efficiency of the vehicle system.

In order to overcome the above said drawback it is required to match the pump oil output with the oil requirement by the rubbing parts at all engine speeds.

One method is to provide a 'variable displacement Gerotor pump', (US Patent Number: US2008/0019846A1, 4778361) where changing the eyelid positions with respect the expanding varies the effective displacement of the pump and contracting chambers. By this method even though it is possible to match the oil pumped out from the pump to the oil required by the rubbing parts, still there will not be a substantial saving in energy.

Here even though the pump delivers less oil at higher speeds, still it will consume more energy, as part of the energy will be lost for re-circulating the oil within the chamber confined by the gear teeth.

In conventional lubrication system, the oil pump will get the drive directly from engine, or components like camshaft driven directly by engine, such that the speed of the pump is equal to or directly proportional to engine speed. In this method the pump can be driven by another power source like an electric motor. By doing so the pump can be driven at a speed, different than the engine speed, such that the pump can be made to deliver exactly the same as that required by the rubbing parts. But here also there will not be a substantial saving of energy, as the energy saved by matching the pump delivery with oil requirements will be lost in the energy conversions occurring at the 'alternator generator' and at the 'electric motor'.

Therefore a need arises to overcome this issue of wastage of energy and increase the overall efficiency of the system.

Hence the objective of the invention is to provide a multi stage oil pump which delivers the required quantity of lubrication oil to various parts present in a four stroke spark or compression ignited engine.

Summary of the invention

The present disclosure consists of two Gerotor pumps arranged in parallel configuration.

In this method, instead of a single Gerotor pump, two pumps of lower displacement are used. Here both the pumps receive power from engine and are connected in parallel. At lower rpm, both the pumps work together to meet the oil requirement by the rubbing parts. But at higher rpm, when the pumps deliver oil, which is higher than the requirement, one of the pumps gets shut down by disconnecting its drive from the engine.

Hence the second pump only meets the oil requirement. When compared to the previous methods, here the energy saved by matching the oil delivered with oil required is neither lost as eddies occurring within the chamber nor in energy conversions at the electric motor.

Brief description of drawings

The above and other features, aspects and advantages of the subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where:

Figure 1 illustrates a Gerotor pump with typical notations on its various working conditions.

Figure 2 illustrates a cross sectional view of the proposed art.

Figure 3 illustrates isometric view of the proposed art.

Figure 4 illustrates an exploded view of the proposed art.

Detailed description

A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures 2 to figure 4 Present arrangement consists of two Gerotor pumps arranged in parallel configuration. The pumps selected are low displacement pumps, such that at lower engine speeds the oil delivered by both the pumps will be equal to the net oil required by the rubbing parts. At higher engine speed when the net oil delivered by both the pumps is higher than the required, pump 2 is
disconnected and pump 1 only works which supplies less oil that matches the requirement. The operation of the pump can be divided into two stages.

a. Low-speed operating range.

b. High-speed operating range.

a. Low-speed operating range: (up to 2000rpm)

Here the drive from the engine is first transferred to the drivegearl 202. Since the drive gearl 202 is coupled to the inner rotorl 212 through the drive shaft 1 205, the drive is transferred to the inner rotorl 212 and thus the inner rotorl 212 starts rotating. The inner rotorl 212 transfers this drive to the outer rotorl 219, through the engaging teeth and there by causes the outer rotorl 219 to rotate along with it. As the rotors rotate, the expanding chambers confined between the inner rotor and outer rotor teeth suck the oil through the inlet eyelidl 208. On subsequent rotation of the inner rotorl 212 and outer rotorl 219, the confined chamber A contracts and thereby compress the oil and delivers it to the gallery through the outlet eyelidl 220 and the outlet oil passagel 221.

During rotation the centrifugal masses203 mounted to the drive gearl 202 also rotates and thereby experience a centrifugal force which forces them to fly away against the spring force developed by spring206. However at lower engine speeds, the centrifugal force developed is lower than the spring force and hence the spring forces the teeth on the centrifugal mass 203 to be pressed against the teeth on the drive gear 2 204.As a result the drive from the drive gearl 202 is transferred to the drive gear2 204 through the centrifugal mass 203. The drive gear2 204, connected to the inner rotor2 213, through the drive shaft 2 423, transfers this drive to the inner rotor 2 213. Inner rotor2 213 transfers this drive to the outer rotor2 218 through the meshing gear teeth. As the inner rotor2 213 and outer rotor2 218 rotates, they take in oil form the oil sump through the non-return valvel 209, pressurize the oil and deliver it to outlet eyelid 2 214. This pressurized oil push opens the no-return valve2 216 and move to the oil gallery.

High-speed operation:

Whenever the engine speed crosses a threshold speed(2000rpm), where the delivery from one pump is sufficient to meet the requirement, the pump 2 is switched off. Here as the engine speed crosses beyond the threshold speed, the centrifugal force developed by the centrifugal mass 203 becomes higher than the spring force exerted. So the centrifugal masses 203 fly off. As they do so the gear teeth provided on the centrifugal mass 203 loses its contact with the mating gear teeth on drive gear2 204 and thereby decouples the drive gear 2 204 from drive gearl 202. Hence the pump2 connected to the drive gear2 204 stops rotating and there by stops pumping the oil. However the pumpl is still coupled to drive gear 1 202 and rotates to deliver the oil to the gallery. In this case there arises a situation in which the oil delivered from pumpl enters into the pump2 and thereby making the pump 2 to work as a motor. This is prevented by the non-return valves 1 and 2 216 & 209 that prevent any reverse flow of oil from the pumpl to pump2.

Nomenclature used in the diagrams

213: Inlet rotor 2

201: Casing 1

214: Outlet eyelid 2

202: Drive Gear 1

215: Outlet oil passage 2

203: Centrifugal Mass

216: Non return valve 1

204: Drive Gear 2

217: Casing 2

205: Drive shaft 1

218: Outer rotor 2

206: Centrifugal spring

219: Outer rotor 1

207: Inlet oil passage 1

220: Outer eyelid 1

208: Inlet eyelid 1

221: Outlet oil passage 1

209: Non-return valve 2

322: Gasket

210: Inlet oil passage 2

423: Drive shaft 2

211: Inlet eyelid 2

424: Plug

212: Inlet rotor 1

425:Fasteners

Claims

We claim:

1. An oil pumping system for a four stroke engine, comprising;

a pair of gerotor pumps, pump 1 and pump 2 wherein it includes a casing 1 201; a drive gearl 202; a centrifugal mass 203; a drive gear 2 204; a drive shafM 205; a centrifugal spring 206; an inlet oil passage 1 207; an inlet eyelid 1 208; a non return valve 2 209; an inlet oil passage 2 210; an inlet eyelid 2 211; an inner rotor 1 212; an inner rotor 2 213; an outlet eye lid 2 214; an outlet oil passage 2 215; a non return valve 1 216; a casing 2 217; an outer rotor 2 218; an outer rotor 1 219; an outlet eyelid 1 220; an outlet oil passage 1 221; a gasket 322; a drive shaft 2 423; and fasteners 425; wherein both pump 1 and pump 2 are low displacement pumps, such that at lower engine speed the oil delivered by both the pumps pump 1 and pump 2 will be equal to the net oil required by the rubbing parts.

2. The oil pumping system for four-stroke engines as claimed in claim 1 wherein both pump 1 and pump 2 are arranged in parallel configuration.

3. The oil pumping system for a four stroke engine as claimed in claim 1, wherein both pump 1 and pump 2 are low displacement pumps, such that at lower engine speed the oil delivered by both the pumps pump 1 and pump 2 will be equal to the net oil required by the rubbing parts.

4. The oil pumping system for a four stroke engine as claimed in claim 1 wherein at higher engine speed when the net oil delivered by both the pumps is higher than the required, pump 2 is disconnected and pump 1 only works which supplies less oil that matches the requirement.

5. An oil pumping system for a four stroke engine comprising a pair of gerotor pumps pump 1 and pump 2, wherein during rotation at lower speed, the centrifugal masses mounted to the drive gearl 202 also rotates and the spring forces the teeth on the centrifugal mass to be pressed against the teeth on the drive gear 2 204 and subsequently the drive from the drive gearl 202 is transferred to the drive gear2 204 through the centrifugal mass and consequently drive gear2 204, connected to the inner rotor2 213, through the drive shaft 2 423, transfers this drive to the inner rotor 2 213 which in turn transfers this drive to the outer rotor2 218 through the meshing gear teeth and thus taking in oil form the oil sump through the non-return valvel 216, pressurize the oil and deliver it to outlet eyelid 2 214 and finally this pressurized oil push opens the no- return valve2 209 and move to the oil gallery.

6. The oil pumping system for a four stroke engine as claimed in claim 1, wherein during rotation at high speed, the gear teeth provided on the centrifugal mass loses its contact with the mating gear teeth on drive gear2 204 and decouples the drive gear 2 204 from drive gearl 202 and the pump2 connected to the drive gear2 204 stops rotating and there by stops pumping the oil.

7. The oil pumping system for a four stroke engine as claimed in claim 1 wherein, it comprises a pair of non-return valves 1 and 2 216 & 209 that prevent any reverse flow of oil from the pumpl to pump2.