EP0049603A2

EP0049603A2 - Lubrication system

Info

Publication number: EP0049603A2
Application number: EP81304537A
Authority: EP
Inventors: William Robert Oswald Mann; Roger Brian Smedley; David Charles Warkman
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1980-10-04
Filing date: 1981-10-01
Publication date: 1982-04-14
Also published as: DK438781A; EP0049603A3; JPS5788212A; ES506543A0; ES8206743A1; NO813345L; BR8106384A; GR75371B

Abstract

A cylinder lubrication system for an internal combustion engine, particularly a low speed compression ignition engine, is controlled electronically.

Oil supply to the cylinders is from a ring main gallery (22,41) via oil supply devices (16) having electro-magnetically operated valves (19).

An electronic control system (29) actuates valves (19) in response to signals from a timing device (30). Signals may additionally be generated from an oil pressure sensor (28), a flow detector (21) and other sensors detecting other engine operating parameters fed into the electronic control system to adjust and control the lubricant supply.

Description

This invention relates to a lubricating system for the cylinder and piston rings of an internal combustion engine, for example, a low speed compression ignition engine.
It is known in the field of low speed compression ignition engines to supply metered quantities of lubricating oil to the running surface between the cylinder bore and the piston rings. This is achieved through a plurality of openings formed in the surface of the cylinder bore in which the piston is located, the openings, which may be in a common transverse plane, being angularly spaced about the longitudinal axis of the cylinder bore. The openings may contain nozzle assemblies and oil is supplied to each opening of the nozzle assembly therein by means of mechanical pumps respectively, conveniently driven by a cam shaft of the engine. The supply of oil to the piston has to be carefully timed and its quantity caarefully controlled in order that the oil is used to the best advantage.
The mechanical pumps which have been employed have proved to be difficult to refine in order to achieve the precise control needed to obtain satisfactory lubrication under all the working conditions of the engine and at the same time minimise the consumption of oil.
The object of the invention is to provide a lubrication system for the cylinder and piston rings of an internal combustion engine in a simple and convenient form.
According to the invention, a lubricating system for a cylinder of an internal combustion engine comprises a plurality of oil supply devices disposed about the cylinder bore in which a piston is located, each device having an oil outlet to the cylinder bore, an oil inlet, a supply gallery to which the oil inlets of the device are connected, each device incorporating an electro-magnetically operated valve, an oil pump for supplying oil to said gallery, valve means for controlling the oil pressure in said gallery, an electronic control system for energising the valves of said devices when it is required to supply oil to the surface of the cylinder bore and means for providing a timing signal to said control system from which the control system can determine the position of the piston so as to ensure that delivery of oil to the surface of the cylinder bore takes place at the desired position of the piston.
The internal combustion engine may be a low speed compression ignition engine. Such engines, which may run at from 50 to 300 rpm, are extensively used for ship propulsion but they may also be used as stationary engines on land, e.g. for electricity generation.
The oil outlet of the oil supply device may be similar to the outlets currently used for mechanical systems and known as quills. Thus it may have a non-return valve, e.g. a spring loaded ball valve to prevent gases from the cylinder entering the oil supply system. For the present system it is preferred that the quills should be designed to have interchangeable nozzles. In this way the diameter and other characteristics of the nozzle can be altered to suit differing circumstances and make better use of the flexibility of the present system as compared to a mechanical system.
The supply gallery may be, in effect, a ring main system with each oil supply device having an inlet from a supply limb of the gallery and an oil outlet to a return limb of the gallery. Oil can be circulated around the ring main at a rate in excess of the rate of delivery to the cylinder bore. This ensures that there is always an adequate supply of oil to the devices and also helps in cooling the electro-magnetically operated valve.
The electro-magnetically operated valve may be of the known solenoid type. A particularly suitable, quick-acting valve is one having a helically wound armature as described and claimed in UK Patent No. 1504873.
The valve for controlling the oil pressure in the gallery should be set so that the oil pressure is in excess of the engine cylinder pressure at the time of oil injection and this may vary according to the engine design. The presure is likely to be at least 10 bars and may be as high as 125 bars.
The oil in the gallery may also be at elevated temperature, e.g. a temperature of from 50-100°C. This may be achieved by means of a heater and thermostat in a main oil tank supplying oil to the gallery. The use of an elevated temperature has a number of benefits including a lower oil viscosity and a more accurate control of viscosity (i.e. the oil viscosity index will be more favourable than at ambient temperature). The oil may, nevertheless, be the same as that used for mechanical systems.
The electronic control system may be based on generally known principles of electronic control and may, as discussed in more detail hereafter, vary in complexity depending on the number of variables to be allowed for. In its simplest form it converts timing signals into valve actuation but may, in addition, take account of signals from a pressure sensor in the oil gallery to check that the oil pressure is correct and signals from flow detectors in the oil supply devices to check that the devices are functioning.
The timing signal may be generated from the engine conveniently the crankshaft and may be generated by mechanical, electrical or optical means.
Other features of the system may be:

An accumulator and relief valve between the oil pump and the oil gallery to stabilise the oil supply and guard against excessive pressure,
A filter also between the oil pump and the oil gallery,
A bleed line at atmospheric pressure on the downstream side of the electro-magnetically operated valve so that the pressure drops quickly at the end of injection and valve closure is rapid.

An example of a lubrication system in accordance with the invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic view of a lubrication system also showing parts of the associated engine, and
Figure 2 is a block diagram of an electronic control system for the lubrication system.
Figure 1 shows one cylinder and piston of a low speed compression ignition engine.

Piston 10 is mounted in a cylinder bore 11 which conveniently is the internal surface of a liner 12. The piston is connected to a cross head 13 and the cross head, in known manner, is connected by means of a connecting rod 14 to a crank shaft 37 of the engine. The piston 10 is provided with a plurality of piston rings and formed into the liner are a plurality of openings 15 in which are located oil supply devices indicated generally at 16. The openings are equiangularly spaced about the longitudinal axis of the cylinder bore and conveniently lie in a common plane. In the particular example there are 8 such openings.
Each oil supply device 16 comprises a body part 17, the body part being hollow and having an oil inlet 18 and an oil outlet 38. An oil supply passage 39 extends from the interior of the body part to terminate in outlet 15 and includes a non-return valve 40 to prevent gases from the engine cylinder entering the body part. Located within the body part is a valve 19 which is operated by an electro-magnetic device generally indicated at 20 and which includes a spring which biases the valve member 19 into contact with a seating. Located in the passage 39 is a flow detector 21.
The lubrication system also includes an oil supply gallery.
The gallery is in the form of a ring main with a supply limb 22 and a return limb 41. Supply limb 22 has outlets 23 for connection to the inlets 18 of the oil supply devices and return limb 41 has inlets 42 for connection to the outlets 38 of the oil supply devices.
Lubrication oil is supplied to limb 22 from a main oil tank 26 through an atmospheric pressure filter 25, oil pump 24 and high pressure filter 34. The oil tank 26 is maintained at a pre-determined temperature by heater 43 and thermostat 44. The supply limb 22 also has an accumulator and relief valve 32 returning oil to tank 26 if the pressure exceeds a safe pre-determined value.
Oil is returned to tank 26 through return limb 41 .by.way of a control valve 27 the setting of which can be varied by means of an electrical signal applied to it. A pressure sensor 28 is located upstream of the valve 27 to provide an indication of the oil pressure within the gallery.
There is also a return pipe 36 to oil tank 26 from passage 39 of the oil supply device. A small orifice 35 connects passage 39 and pipe 36 allowing a small continuous bleed from passage 39 at atmospheric pressure. Loss via the bleed is small when valve 19 is open and oil is being injected, but when valve 19 closes the bleed allows a quick collapse of pressure in passage 39 so that the valve closes quickly and tightly.
The lubrication system also includes an electronic control system generally indicated at 29. The control system has power outlets connected to the electro-magnetic devices 20 respectively and it also has a power outlet to the aforesaid control valve 27. The control system provides signals, at the appropriate time, to the electro-magnetic devices 20 to lift the valve members 19 from their respective seatings thereby to allow supply of oil to the surfaces of the cylinder bore and piston rings. In order to do this the control system is supplied with a timing signal from a sensor 30 which is disposed adjacent a rotary part of the engine, the part being generally indicated at 31. The signals provided by the sensor 30 are interpreted by the control system so that the signals to the devices 20 are provided at the correct time. In addition the control system receives a signal from the
can be provided to the control valve 27 to ensure that the oil pressure in the gallery is correct. In addition the control system receives signals from the flow detectors 21. These detectors are switches
which are opened when flow of oil takes place. In the event that a detector does not provide the required signal this is noted in the control system and an alarm is given. The alarm need not necessarily be given for any individual lack of signal but can be arranged to be given if the lack of a signal persists and exceeds a certain percentage, e.g. if no signal is provided on 5 or more occasions per 100 actuations.
It is desirable that the quantity of oil supplied to the piston should vary in accordance with various engine operating parameters, for example, the speed of the engine, the power being developed by the engine and the type and quality of fuel being used. Signals are therefore provided to the control system in order that the amount of oil delivered to the piston can be varied to suit the engine operating parameters. In addition a signal may be provided indicative of the wear of a cylinder bore which signal may be used to increase supply of lubricant to a maximum. It may be desirable that the oil supply devices should operate in sequence during the stroke of the piston and this can be arranged by suitable modification of the control system. In addition it may be necessary for more oil to be supplied by some of the devices than the other devices and this is arranged by ensuring that the valves of the devices remain lifted from their seatings for a further period of time. Adjustment of the setting of the control valve 27 will produce an overall variation in the amount of oil supplied by each device.
Figure 2 is a block diagram of an electronic control system for use with the lubrication system of Figure 1.
In Figure 2, the crankshaft position sensor (30 and 31 of Figure 1) generates two signals, a single pulse per revolution which marks bottom dead centre of number one cylinder and another signal, which generates 3600 pulses per revolution. The 'BDC' pulse is fed through a detection circuit 45, and then through an optional 'crankshaft torsion correction' circuit 46 to a sequencer 47 and to another pulse detection circuit 48. This pulse detection circuit counts the second, 3600 pulses per revolution signal, and is reset by the 'BDC' pulse, giving a numberical count representing crank angle from bottom dead centre.
The sequencer 47 takes the form of a matrix, manually controlled so that each lubricator can operate individually in any sequence over a period of 10 revolutions. The sequencer has 8 output channels (for 8 lubricators) which are fed to 8 injector logic circuits, one of which is shown at 49.
These logic circuits compare the count from the pulse detector circuit 48 with two values (to give start and end of injection) which are set manually. After the first comparison, a signal is sent via a fault detection circuit 50 to the injector drive circuit 51 which energises the electro-magnetic device (20, Figure 1) in the lubricator (17, Figure 1) beginning the injection sequence.
When the second comparison has been made, the drive circuit is switched off, ending the injection.
The flow through the lubricator is monitored by a flow detection (21, Figure 1) which sends a signal to the fault detection circuit 50. There the flow detector signal is compared with the injector logic signal. If there is a difference between the signals (i.e. the lubricator has not injected properly) and this occurs more than a certain number of times in 100 attempted injections, the operation of the lubricator is stopped and a signal sent to the warning and alarm systems 52,53. The circuits can be manually reset if required.
The lubricator oil pressure in controlled by a linear integral/proportional loop control system. Pressure is sensed by a transducer (28, Figure 1) which, after decoding in 54, is compared with a pressure demand signal 55 (normally manually set as at 61). The error between the two signals 56 is sent to a pressure regulator drive circuit 57 which controls the pressure regulator (27,Figure 1). Should this error signal be excessive, indicating a mulfunction in the system, a signal is sent to the warning and alarm system circuits 52, 53 to sound the alarm.
To enable the system to be controlled by engine power, an engine output signal is required. This can be generated by a propeller shaft torque meter 58 which when multiplied by a speed signal gives a further signal proportional to engine power. This is generated and modified in the 'Power Link' network 63 and then fed to the pressure . control network 55. Thus the system pressure and hence injection quantity can be adjusted by the engine power output. The 'Power Link' network can be designed to produce any desired relationship between quantity of oil delivered and engine power.
The output from the torque meter 58 is also fed to the crankshaft torsion correction circuit 46 so that crankshaft 'wind up' can be corrected for.
If the engine is fitted with a 'scuffing alarm' system (cylinder liner temperature sensing system) 59 the lubrication system can be rest by this alarm. Signals from the scuffing alarm are fed to the pressure control network.55 and the sequencing circuits 47. Thus if the alarm is activated, the system pressure is adjusted to ensure adequate supply of lubricating oil and the sequencer ensures each injector functions every engine revolution.
Provision is also made for an input to the alarm system from temperature sensors 60 in the heated supply tank. Should the temperature in the tank go outside the normal operating range, the alarms are activated.
The system also has an engine simulator 62 which can supply signals to the BDC detector 45 and the pulse detector 48 if required. This enables the lubricators to be checked and bled even if the engine itself is stationary.
It should be apparent that an electronically controlled lubrication system according to the present invention will have advantages over the present mechanical systems. The advantages include:-

a) more accurate control of lubricant supply leading to reduced lubricant consumption,
b) less mechanical wear and hence a longer service life of cylinder liners and piston rings.
c) greater flexibility allowing adjustment in lubricant supply in response to a variety of engine operating parameters and conditions.

Claims

1. A lubrication system for a cylinder of an internal combustion engine comprising a plurality of oil supply devices disposed about the cylinder bore in which a piston is located, each device having an oil outlet to the cylinder bore, an oil inlet, a supply gallery to which the oil inlets of the device are connected, each device incorporating an electro-magnetically operated valve, an oil pump for supplying oil to said gallery, valve means for controlling the oil pressure in said gallery, an electronic control system for energising the valves of said devices when it is required to supply oil to the surface of the cylinder bore and means for providing a timing signal to said control system from which the control system can determine the position of the piston so as to ensure that delivery of oil to the surface of the cylinder bore takes place at the desired position of the piston.

2. A lubrication system as claimed in claim 1 in which the engine is a compression ignition engine operating at 50 to 300 rpm.

3. A lubrication system as claimed in claim 1 or 2 characterised in that the oil outlet to the cylinder bore has an interchangeable nozzle.

4. A lubrication system as claimed in claim 1., 2.or 3 characterised in that the supply gallery is a ring main with a supply limb and a return limb.

5. A lubrication system as claimed in any of claims 1 to 4 characterised in that the electro-magnetically operated valve has a helically wound armature.

6. A lubrication system as claimed in any of claims 1 to 5 characterised in that the system has a heater and thermostat to heat the oil to a pre-determined temperature.

7. A lubrication system as claimed in any of claims 1 to 6 characterised in that the oil supply device has a flow detector.

8. A lubrication system as claimed in any of claims 1 to 7 characterised in that the oil supply device has a bleed line at atmospheric pressure downstream of the elctro-magnetically operated valve.

9. A lubrication system as claimed in claim 1 substantially as described with reference to Figures 1 and 2.

10. A method of lubricating an internal combustion engine comprising supplying oil to a cylinder via a lubrication system as claimed in any of claims 1 to 9.