GB2198191A

GB2198191A - Solenoid driven pump

Info

Publication number: GB2198191A
Application number: GB08724148A
Authority: GB
Inventors: Michael Leonard Mckay
Original assignee: ORBITAL ENG Pty; Orbital Engine Co Pty Ltd
Current assignee: ORBITAL ENG Pty; Orbital Engine Co Pty Ltd
Priority date: 1986-10-14
Filing date: 1987-10-14
Publication date: 1988-06-08
Also published as: JPS63179113A; GB8724148D0; IT1222906B; DE3744665A1; FR2606073A1; DE3735019A1; BR8705497A; KR880005342A; IT8722270A0; BE1001379A5

Description

1, 10819.1 2 0 w IMPROVED LUBRICATION SYSTEM AND PUMP OF INTERNAL

COMBUSTION ENGINES This invention relates to a lubrication system for providing lubricant to internal combustion engines, particularly two stroke cycle engines, and to a lubricant pump for that purpose.

Lubrication systems of internal combustion engines have the prime function of delivering oil at an appropriate rate to the various moving surfaces of the engine and, for a number of reasons well recognised in the engine industry, air and other gases may be entrained with the oil and accordingly the pump must be capable of performing effectively under such conditions. In situations where an engine is not operated for considerable periods, the oil may drain from the various ducts and pass.ageways in the lubrication system. Under such conditions it is necessary for the pump to be capable of initially pumping air to clear air from the system before the pumping of the oil can commence.

The current trend in engines operating on the two stroke cycle, such as used extensively in outboard ' marine 1 engines, is to avoid the practice of mixing oil Jith the fuel as a means of lubrication of the engine because of the inconvenience involved and the pollution problems associated therewith. Currently such engines are provided with a pump or pumps which deliver metered quantities of oil to various areas of the engine where lubrication is required. Control systems are used with the pumps to vary the quantity of oil delivered in accordance with the lubrication requirements of the particular section of the engine, which are basically related to both the engine speed and the engine load.

Pumps for this purpose are mechanically controlled such as by continuously driving the pump at a speed proportional to engine speed, and varying the displacement of the pump per stroke in accordance with the engine air throttle position, the latter being representative of the -2engine load. These systems are limited in regard to the degree of control that can be exercised over the rate of oil delivery, and require comparatively complex mechanical mechanisms which are costly both from the point of view of manufacture and assembly, and are subject to mechanical wear with resultant loss of accuracy in oil delivery control.

In addition the pumps currently employed in the lubrication of two stroke cycle engines are not conveniently adapted for control by electronics as they require considerable mechanical mechanisms to interface with an electronic controller.

It is therefore the principal object of the present invention to provide a lubrication system and a pump for the regulated delivery of oil to internal combustio engines, particularly two stroke cycle engines.

With this object in view there is provided according to the present invention in an internal combustion engine lubrication system a pump means to deliver oil to a selected location in the engine, said pump means having a fixed delivery rate per cycle thereof, electromotive means operable to produce a cyclic motion and coupled to drive said pump means at a fixed ratio of pump cycles to electromotive means cycles, means to sense selected engine operating conditions and determine therefrom the oil demand at said selected location, and means operable in response to said determined oil demand to control the cyclic frequency of said electromotive means so that the rate ofoil delivered on a time basis by the pump means is related to said determined oil demand.

Conveniently the electromotive means is a solenoid means that is coupled to the pump means to effect one cycle thereof per cycle of the solenoid means. Preferably the pump means is a piston type pump which may be directly coupled to an armature of the solenoid means. The solenoid means may be arranged to drive two or more pump means simultaneously, or cyclicly or a combination thereof.

1 1 Conveniently two pumps may be coupled to the armature of one solenoid means, one at each opposite end of the armature. The pumps are preferably half a cycle out of phase with each other so that one is delivering a charge of oil as the other is drawing in a charge of oil.

The rate of oil delivery can be readily controlled by regulation of the cycle frequency of the solenoid. The oil demand may 'be ascertained by a suitably programmed electronic control unit (ECU) which receives signals related to selected engine operating parameters, and determines from that input the required cycle frequency of the solenoid or other electromotive means to meet the oil demand of the engine. Engine operating parameters that may be used in determining the oil demand include engine speed, engine temperature, induction air flow rate, engine fueling rate, and the period that the engine has been operating within selected load and/or speed ranges.

An engine lubrication system is usually required to deliver oil to more than one location, and the oil demand at each location may differ. if the difference in oil demand at respective locations is a substantially fixed relation for all operating conditions, an individual pump may be provided for each location, with all pumps driven by the same electromotive means, and each pump having a respective delivery rate per pump cycle.

In a multi cylinder engine, several pumps may be provided with each pump arranged to deliv,er oil to the same location for all of the cylinders. Thus one series of pumps driven by the same electromotive means may supply oil to the crankcases of several cylinders, while another series of pumps similarly all driven by a second electromotive means may supply oil to the pistons of several cylinders.

Accordingly, to another aspect of the present invention there is provided an oil pump for incorporation in an engine lubrication system, said pump comprising a cylinder closed at one end, a valve controlled discharge 1 port in said closed end, a piston axially movable in said cylinder and defining a working chamber between said piston and said closed end and drive means to effect cyclic reciprocation of the piston in the cylinder, the working chamber varying in volume in response to said axial movement, said piston having a skirt portion slidably received in said cylinder in substantially sealing relation and a head portion in opposed face to face relation with said closed end of the cylinder, said head portion being supported for limited axial movement relative to the skirt portion, said head and skirt portions being adapted to provide selective communication between the working chamber and the supply part of the cylinder on the opposite side of said head portion in response to said limited axial movement, so oil can flow past the head portion to enter the working chamber as the piston moves away from the closed end of the cylinder and oil flow between the working chamber and that said supply part of the cylinder is prevented as the piston moves in the opposite direction. 20 Preferably this pump may be incorporated as the positive displacement pump in the lubrication system previously described, and two said pumps may be coupled to the one drive means, such as the electromotive means previously referred. Conveniently the limited axial movement between the head and skirt portions of the piston cyclicly opens and closes an annular passage between them to control the flow of oil into the working chamber. Preferably the discharge port incorporates a pressure responsive valve means to permit delivery of oil therethrough when the pressure in the working chamber is above a predetermined value.

Conveniently the head portion of the -piston has a diameter selected to provide an annular axial passage between the periphery of the head portion and the wall of the cylinder to provide part of the oil flow path to the working chamber. The axial movement of the head portion in -5a direction away from the skirt portion provides a radial annular passage between the head and skirt portions that communicates the annular axial passage with a hollow interior of the skirt portion. The piston head and skirt portions have respective annular surfaces which define the opposite walls of said radial annular passage when said portions are axially spaced, and which cyclicly sealably abut to prevent oil flow past the head portion into the working chamber.

Preferably the head portion is connected to the skirt portion to permit a limited degree of axial movement therebetween at each change in direction of the axial movement of the piston. That is as the piston is moving towards the closed end of the cylinder, the respective radial faces of the skirt and head portion abut in sealing relation. Accordingly, the oil in the working chamber is pressurised. Upon the skirt portion reversing its direction of movement to move away from the closed end of the cylinder, the skirt portion will initially move a small distance before the head portion commences to also move in the reverse direction, -this causes the two annular faces to separate and provide the radial annular passage therebetween. Oil may t henflow through the radial annular passage and the axial annular passage to enter the working chamber. Upon the piston changing direction of movement at the opposite end of its axial movement in the cylinder, the reverse relative movement takes place between the skir..-. and head portions to effect closing of the radial annular passage.

The invention will be more readily understood from the following description of preferred practical arrangements of an engine lubrication system and the pump therefor, as illustrated in the accompanying drawings.

In the drawings:

Figure 1 is a longitudinal cross sectional view of a pump assembly incorporating two pumps driven by a single solenoid; 1 Figure 2 is an enlarged view of a piston skirt and head as shown in Figure 1; Figures 3 and 4 are schematic representations of two alternative lubrication systems for a two stroke cycle engine and incorporating a pump assembly as shown in Figure 1; Figure 5 is a logic diagram. for the electronic control of the lubrication system as shown in Figure 2; Figure 6 is an electrical circuit diagram for the oil pump control.

Referring now to Figures 1 and 2, the pump assembly comprises a cylindrical housing 1 in which t ' here is fixedly mounted a cylindrical core 2 having wound thereon a coil winding 3. The armature 4 is disposed within the central cavity of the cylindrical core 2 with the compression spring 5 interposed between the armature 4 and the internal annular shoulder 6 on the core 2. The spring 5 urges the armature in a direction upwardly as seen in the Figure 1.

The annular end portion 7 of the housing 1 is of a magnetic material and has an internal cylindrical surface 8 providing a narrow annular air gap 9 between the surface 8 and the cylindrical end portion 10 of the armature 4. The winding 3 is wound so that when energised the magnetic field so produced will draw the armature 4 downwardly as viewed in Figure 1, against the resistance of the spring 5. Hence, upon the de-energising the winding 3, the spring 5 will cause the armature to return upwardly to occupy the position as shown in the drawing.

The cylindrical tube 11 of non magnetic material extends coaxially through the armature 4 and is rigid therewith. At each end of thearmature 4 the tube 11 extends axially to form respective piston skirts 12 and 13 integral with the tube 11 and slidably received in respective cylinders 14 and 15. The piston skirts 12 and 13 are freely slidable in the cylinders 14 and 15 and cooperate therewith in a substantially sealing relation as a pump piston t cooperates with a pump cylinder in a conventional reciprocating pump.

Each piston skirt 12 and 13 has abutting the free end thereof a piston head 16 and 17 respectively, the piston heads having integral guides 18 and 19 respectively slidably received within the bore of the tube 11 at opposite ends thereof. The pins 20 and 21 fixedly mounted in the armature 4 pass through espective apertures 22 and 23 and in the guides 18 and 19, with a predetermined clearance in the axial direction of the tube 11 between the pins and the apertures through which they pass. This clearance permits the respective piston heads 16 and 17 to have limited axial movement relative to the cooperating piston skirt 12 and 13.

Each of the cylinders 14 and 15 is closed by respective end walls 24 and 25 in which there are provided delivery ports 26 and 27. The ports are normally closed by respective ball valves 28 and 29, held in the closed position by the springs 30 and 31.

As shown in the drawing the armature 4 is at the limit of its movement in the upward direction and in that position a working chamber 35, provided between the piston head 17 and the end wall 25 of the cylinder 15, is of maximum capacity. The working chamber 36 at the opposite end of the assembly between the piston head 16 and end wall 24 is of minimum capacity. when the armature is moved to the opposite end of its extent of movement the working chamber 35 will be of minimum capacity and working chamber 36 of maximum capacity.

Nipple 37 is provided for connection to an oil line leading to an oil reservoir so that oil will normally fill the whole of the free space within the housing 1, including the interior of the tube 11 and the interior of the piston skirts 12 and 13. As can be seen at 40 and 41 a series of apertijres is provided in the wall of the tube 11 and the piston head guides 18 and 19 to provide free passage of oil into the interior of the tube 11 and the piston skirts 12 and 13 and piston head guides 18 and 19.

Considering now in detail the operation of one of the piston skirt and piston head assemblies, such as that made up of the piston skirt 13 and head 17 at the lower end of Figure 1. Assuming that at the position as shown the working chamber 35 is charged with oil, upon energising of the coil 2 the armature 4 will commence to move downwardly in Figure 1. This movement will be transmitted directly through the tube 11 and pin 21 to piston skirt 13 and piston head 15 and so the oil in the chamber 35 will be pressurised. When the pressure of the oil is sufficient to dislodge the ball valve 29 against the action of the spring 31, oil will be delivered through the port 27. The extent of the movement of the armature 4 is limited by the piston head 17 contacting the end wall 25, in which posi tion substantially all of the oil will have been discharged from the working chamber 35.

Upon de-energising of the coil 3 the spring 5 will cause the armature to commence to move upwardly as seen in Figure 1 and this movement will immediately be translated to the tube 11 and the piston skirt 13. However, there will be no corresponding immediate movement of the piston head 17 due to the clearance between the pin 21 and apertures 23 in the piston guide 19. This absence of movement of the piston head 17 will cause a break in the contact between the radial face 42 of the piston head and the corresponding radial face 43 of the piston skirt, whereby the annular radial passage 44 will be formed therebetween as seen in Figure 2. As the movement of the armature 4 continues upwardly, the clearance between the pin 21 and the apertures 23 will be taken up and thereafter the piston head 17 will move in unison with the piston skirt 13. However, the annular radial passage 44 will remain therebetween whereby oil may pass from the interior of the piston skirt 13 around the periphery of the piston head 17 into the working chamber 35.

1 When the limit of the upward movement of the armature 4 has been reached, the piston head 17 will still be spaced from the skirt 13 to privide the annular passage 44.

Upon commencement of the next cycle the energising of the coil 3 will again commence downward movement of the armature 4 to the right as seen in Figure 1, whereupon the tube 11 and the piston skirt 13 will immediately commence to move downward. As a result of the clearance between the pin 21 and the apertures 23, the piston head 17 will not immediately move similarly and so the end face 42 of the piston skirt 13 will advance toward the radial face 43 of the head 17 until contact is established therebetween, whereafter the piston head and skirt will move in unison towards the cylinder end face 25 thus commencing another oil delivery cycle.

It will be appreciated that the piston head 16 and skirt 12 at the opposite end of Figure 1 operate on the same cycle as descried above with respect to the piston head 17 and skirt 13, but a half cycle out of phase therewith.

In the above described cnstruction, it is required to provide sufficient clearance between the peripheral edge 45 of the piston head 17 and the wall of the cylinder 15 so that the annular space about the piston head 17 is sufficient for the oil to pass into the working chamber during the intake stroke. However, this clearance must also be kept to a sufficiently low value to ensure that the clearance volume in the working chamber 35, when the piston head 17 reaches the end of its stroke towards the end wall 25, will not substantially effect the volumetric efficiency of the pump operation. This is of particular importance as this pump must, under some circumstances, pump air or an air and oil mixture, and accordingly unless the clearance volume is ket to a the air trapped in the working chamber can nullify the pumping action normally derived from the movement of the piston. The diameter of the piston head portions 16 and 17 is preferably not less than 0.75 of the diameter of the bore of the cylidner 15 in which the piston operates.

In order to reduce the sticking effect between the piston head and the end wall of the cylinder, one or more transverse grooves may be provided in the face of the piston head opposite to the cylinder end wall, the groove extending from the peripheral edge of the piston head. Alternatively the face of the piston head may be shaped to reduce the area of contact with the end wall of the cylinder.

Also in order to improve the volumetric efficiency of the pump above described, there can be provided resilient means, such as a spring, to normally position the piston heads so the radial faces 42 and 43 are in contact thus closing the annular radial passage 44. This construction has the advantage that at the end of the movement of the piston skirt 13 in the direction away from the end wall 25, the piston head 17 continues to move in that direction under the action of the resilient means to close the passage 44 before or as the direction of movement of the piston skirt 13 changes. Accordingly the proportion of the movement of the piston skirt 13 towards the cylinder end wall 25 during which the passage 44 is opened is eliminated or reduced to thereby increase the volumetric efficiency of each cycle.

The resilient means or spring above described with reference to the piston skirt 13 and head portion 17 is also provided to operate with the piston skirt 12 and head portion 16 at the opposite end of the pump assembly. In one preferred construction a tension spring is connected between the piston head portions 16 and 17, and tensioned to achieve the above described operation.

Figure 3 of the drawings illustrates a typical lubrication system for a two cylinder, two stroke engine and incorporating the oil pump as described above. The engine 100 is of a conventional construction wherein air is induced into individual crankcase areas 101 and 102 associated with the respective cylinders 103 and 104. The air flow to the respective crankcases is via the air induction duct 105 in which a conventional throttle valve 106 is located and having respective reed valve assemblies 107 and 108 communicating the induction duct with the respective crankcases.

An air flow sensor device 110 of known construction is incorported in the air induction duct and provides a signal to the electronic control unit (ECU) 115, that is proportional to the rate of air flow to the respective crankcases. The air flow rate in the induction duct is related to the engine load and thus the input to the EM from the air flow sensor 110 provides the EM with a measure of the engine load.

An engine speed sensor 112 of known construction is located to be activated by the engine flywheel 114 to provide to the EM a signal indicative of the engine speed.

The EM is programmed to determine from the inputs of the air flow sensor and the speed sensor the lubrication requirements of the engine and in accordance with this determination, the EM controls the frequency of the energising cycle of the oil pump 120. AS previously descibed the oil pump provides two deliveries of a fixed quantity of oil each cycle. The respective oil deliveries are conveyed via the ducts 121 and 122 to be delivered into the air induction duct 105 at respective locations immediately upstream of the reed valve assemblies 107 and 108 controlling the flow of air into the respective crankcases. The delivery of the oil is effected through suitable nozzles 123 and 124 so the oil is in a finely divided spray as it issues into the air, and each nozzle incorporates a check valve to prevent the entry of air into the ducts 121 and 122 from the air induction ducts.

In the embodiment shown the EM 115 is also programmed to control the metering and delivery of fuel to the respective cylinders of the engine through the injector and metering units 130 and 131. The same EM may be programmed to also control other functions of the engine, such as the ignition timing, and for this purpose inputs to the EM may be provided in respect of other engine operating parameters and conditions. In particular where the engine is provided with means to vary the exhaust port opening and closing timing, this may also be controlled by the same ECU.

In the lubrication system as above described with respect to Figure 3, lubrication of the bearings of the crankshaft and the lubrication of the piston in the cylinder is effected by the entraining of the oil In the air inducted into the crankcase of the engine and subsequently transferred to the cylinders of the engine in a manner not dissimilar to the principle p'reviously employed of pre-mixing the lubricating oil with the fuel. However, in the embodiment shown in Figure 4 the fuel is not introduced into the air entering the engine, but is delivered by the pump directly at selected locations to the crankshaft bearings and engine cylinders for the purpose of lubricating these respective areas.

in the construction as shown in Figure 4 the oil pump 140 is of the same general construction as previously described butdelivers two different fixed quantities of oil per pump cycle. In this construction the pump delivers the oil to a bearing duct 141 and a cylinder duct 142. The different quantities are used because the oil requirements of the bearings and of the cylinder/piston are different. the different quantities are achieved by having working chambers 35 and 36 displace different fixed quantities of oil, preferably by having piston heads 16 and 17 of different diameter. The bearing duct 141 delivers the oil to an appropriate location within the crankcase where the oil will be effectively applied to the crankshaft bearings. The oil may be delivered in the form of a spreyo with a spray being located and of an appropriate shape, to lubricate the relevant bearings in that crankcase area. The cylinder duct 142 delivers the oil through an orifice in the wall of the cylidner at a location or locations selected so that the oil will be effectively distributed to lubricate the mating surfaces of the piston and cylinder wall including the rings carried by the pistons.

The EM 115A as used with the lubrication system of Figure 4 may he as previously described with respect to Figure 3, and receives signals from the air flow sensor 144 locat&d in the air inductioh passage 145 of the engine and also receiveo input from a suitable located engine speed sensor (not shown).

/1 -.1 i - It will be appreciated that in the lubrication system as described with reference to Figure 3, one delivery of oil is required for each cylinder of the engine end thus the unit as described having two deliveries per cycle is suitable for providing lubrication to two cylinders of an engine. However, the construction shown in Figure 4 requires two deliveries for each cylinder of the engine, that is one to provide lubrication for the engine crankshaft bearing surfaces and the other to provide lubrication for the piston, and therefore one oil pump unit having a double delivery per cycle is requied for each cylinder of the engine. In a multi cylinder engine using the system of Figure 4 one pump may be used to provide the oil to the crankshaft bearing of all cylinders of the engine, and another pump to supply oil to all cylinder bores of the engine.

Figure 5 of the drawings is a typical and somewhat simplified diagram of the logic applied in the determination of the frequency of activation of the oil pump unit from the engine condition parameters supplied to the ECU. The ECU receives a range of inputs as previously discussed, including a measurement of the air flow rate in the engine air induction system, the engine speed, engine temperature and such other parameters regarding the engine operating conditions as may be deemed desirable. From this input information the ECU determines among other things the engine fuel requirement per cylinder per cycle for control of the fuel metering and this information is used in the determination of the engine lubrication requirements as the fuel per cylinder per cycle is a measure of the engine load.

This engine load ordinate and engine speed ordinate are used to determine from a lookup map of fuel to fuel/oil ratio what is the engine oiling requirement for the particular load and speed. The ratio of fuel to oil may vary in the range from 20:1 to 200:1 depending on engine load and speed conditions. The determination of the 1 1 fuel/oil ratio is then used with thefuel per cylinder per cycle determination to calculate the oil requirements per cylinder per cycle and from this informationj and the cycles per second of the engine as determined by the engine speed sensor, the actual oil requirement of the engine per unit time such as in milligrams of oil per second is calculated. This calculation is further modified by a preset factor based on selected engine conditions such as engine temperature, whether the engine is in a transient load condition, whether it is operating at wide open or fully closed throttle and other conditions considered appropriate. This modification factor is then applied to the oil requirement to produce a corrected oil supply rate per unit time. From this determination, and the oil pump calibration, that is the quantity of oil per pump cycle, the frequency of the pump cycles is determined and an output signal produced which will provide the required pulse width between activations of the pump and hence determine the frequency of deliveries of the pump that will meet the determined oil rate requirement of the engine. A minimum and maximum pump frequency is set and if the determined frequency is outside this range the pump will operate at the appropriate end of the frequency range.

In one arrangement it has been found convenient to energise the solenoid of the oil pump for a period of 20 milliseconds per cycle, which has been found to be sufficient time to perform one stroke of the pump, and the frequency of the energising cycles may conveniently vary -between 80 millisOconds for high ailiftg rates to up to 5 seconds for low oiling rates.

The actual operation of the oil pump may be controlled by having the electrical coil winding 3 energised by a conventional 12 volt electrical system as commonly used in motor vehicles and providing a switching transistor driven by' the output from the ECU which cyclically establishes an tarth connection between the coil and the -i & - negative side of the battery so that the coil is energised when the switch is closed and the circuit is earthed, and de-energised when the switch is open. A typical circuit is shown in Figure 6.

The oil pump and oiling system herein disclosed may be used in thedelivery of oil to spark ignited engines operating on either the two stroke cycle or the four stroke cycle. Engines equipped with the oil pump and/or oiling system herein disclosed may be used in any application including engines for vehicles including automobiles, and marine engine including outboard marine engines.

-)-7-

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An internal combustion engine lubrication system comprisiing a pump means to deliver oil to a selected location in the engine, said pump means having a fixed delivery rate per cycle thereof, electromotive means operable to produce a cyclic motion and coupled to drive said pump means at a fixed ratio of pump cycles to electromotive means cycles, means to sense selected engine operating conditions and determine therefrom the oil demand at said selected location, and means operable in response to said determined. oil demand to control the cyclic frequency of said electromotive means so that the rate of oil delivered on a time basis by the pump means is related to said oil demand.

c

2. An internal combustion engine lubrication system as laimed in claim 1 wherein the pump means is adapted to effect two individual deliveries of oil per pump cycle.

3. An internal combustion engine lubrication system as claimed in claim 2 wherein said two individual deliveries are of different fixed quantities of oil.

4. An internal combustion engine lubrication system as claimed in claim 2, wherein the pump means comprises two positive displacement pumps, each having a respective fixed delivery rate per cycle, said electromotive means being operable to effect sequentially movements in two opposite directions each cycle of said electromotive means, said pumps being drive coupled to said electromotive means so one pump effects a delivery of oil in Lesponse to movement in one direction and the other pump effects a delivery of oil in response to movement in said opposite direction.

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5. An internal combustion engine lubrication system as claimed in claim 2 or 4, wherein the electromotive means includes electromagnetic means adapted to be sequentially energised and de-energised to complete one cycle of the electromotive means.

6. An internal combustion engine lubrication system as claimed in claim 1, wherein the pump means comprisesa cylinder closed at one end, a valve controlled discharge port in said closed end, a piston axially movable in said cylinder and defining a working chamber between said piston and said closed end, said electromotive means being drive coupled to said piston to effect cyclic reciprocation of the piston in the cylinder, said piston having a skirt portion slidably received in said cylinder in substantially sealing relation and a head portion in opposed face to face relation with said closed end of the cylinder, said head portion being supported for limited axial movement relative to the skirt portion in the axial direction, said head and skirt portions being adapted to provide selective communication between the working chamber andasupply part of the cylinder on the opposite side of said head portion in response to said limited axial movement, so oil can flow past the head portion to enter the working chamber as the piston moves away from the closed end of the cylinder and oil flow between the working chamber and said supply part of the cylinder is prevented as the piston moves in the opposite direction.

7. An internal combustion engine lubrication system as claimed in claim 6 wherein said head and skirt portions of the piston are adapted to define therebetween an annular radial passage which cyclicly opens and closes in response to said cyclic reciprocation of the piston in the cylinder.

1 -19,

8. An internal combustion engine lubrication system as claimed in claim 70 wherein the head portion defines witth the cylinder an annular axial passage to provide communication between the annular radial passage and the working chamber for the flow of oil into the working chamber when the annular radial passage is open.

9. An internal combustion engine lubrication system as claimed in claim 7 or 8, wherein the piston skirt and piston head portions have respective substantially radial annular faces arranged in opposed relation defining opposite walls of said radial passage when said portions are axially spaced and abut to close said radial passage.

10. An internal combustion engine lubrication system as claimed in claim 6,7,8 or 9, wherein the electromotive means has a reciprocating drive member and the piston ' skirt portion is directly coupled to said drive member to reciprocate in unison therewith, said piston head portion being indirectly coupled to said drive member to permit said limited axial movement between the skirt portion and the head portion at each change in direction of movement of the drive member.

11. A pump comprising a cylinder closed at one end, a valve controlled discharge port in said closed end, a piston axically movable in said cylinder and defining a working chamber between said piston and said closed end, drive means to effect cyclic reciprocation of the piston in the cylinder, said piston having a skirt portion slidably received in said cylinder in substantially sealing relation and a head portion in opposed face to face relation with said closed end of the cylinder, said head portion being supported for limited axial movement relative to the skirt portion in the axial direction, said head and skirt portions being adapted to provide selective communication between the working chamber and a supply part of the cylinder on the opposite side of said head portion in response to said limited axial movement, so fluid can flow past the head portion to enter the working chamber as the piston moves away from the closed end of the cylinder and fluid flow between the working chamber and said supply part of the pylinder is prevented as the piston moves in the opposite direction.

12. A pump as claimed in claim 11, wherein said head and skirt portions of the piston are adapted to define therebetween an annular radial passage which cyclicly opens and closes in response to said cyclic reciprocation of the piston in the cylinder.

13. A pump as claimed in claiml 1, wherein the head portion defines with the cylinder an annularaxial passage to provide communication between the annular radial passage and the working chamber for the flow of fluid into the working chamber when the annular radial passage is open.

14. A pump as claimed in claim 11 or 12, wherein the piston skirt and piston head portions have respective substantially radial annular faces arranged in opposed relation defining opposite walls of said raidal passage when said portions are axially spaced and abut to close said radial passage.

is. A pump as claimed in any one of claims 11 to 14, wherein the drive means is an electromotive driven means, operable at a variable cycle frequency.

16. A pump as claimed in claim 15, wherein the electromotive drive means has a reciprocating drive member and the piston skirt portion is direct coupled to said drive 21)- member to reciprocate in unison therewith, said piston head portion being indirectly coupled to said drive member to permit said limited axial movement between the skirt portion and the head portion at each change in direction of movement of the drive member.

17. A pump as claimed in claim 15 or 16, wherein the electromotive drive means is adapted to effect a fixed stroke of the piston each cycle of the electromotive drive means.

18. A pump as claimed in claim 15, 16 or 17, wherein means are provided to control the cycle frequency of the electromotive drive means in response to the delivery demand on the pump.

18. An internal combustion engine having a lubrication system as claimed in any one of claims 1 to 10.

19. An internal combustion engine as claimed in claim 18 and operating on the two stroke cycle.

20. An internal combustion engine as claimed in claim 18 or 19, being an automobile engine.

21. An internal combustion engine as claimed in claim 18 or 19, being a marine engine.

Published 1988 at The Patent Office. State House, 66'71 High Holborn, London WCIR 4TP. Further copies may be obtained from The Patent Oface, Sales Branch. St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray. Kent, Con. 1/87.