GB2430474A

GB2430474A - Lubrication system

Info

Publication number: GB2430474A
Application number: GB0625988A
Authority: GB
Inventors: David Black
Original assignee: Dana Automotive Ltd
Current assignee: Dana Automotive Ltd
Priority date: 2003-06-14
Filing date: 2006-12-29
Publication date: 2007-03-28
Anticipated expiration: 2023-06-14
Also published as: GB2430474B; GB0625988D0

Abstract

A lubrication system 10 comprises a lubricant pump 12, an electrical heater 16, and controller 18 for controlling the heater 16 and pump 12. The controller 18 is adapted to decrease the amount of electrical power supplied to the heater 16 and increase the amount of electrical power supplied to the pump 12 as the temperature of the lubricant increases. The system 10 may also include a filter 14.

Description

Title: Lubrication System Description of Invention The present invention relates to a lubrication system, particularly, but not exclusively, to a lubrication system for an automotive engine. The presence of particles, for example wear debris, in a liquid lubricant is undesirable as such particles may causes abrasions to the surfaces of the moving parts the lubricant is acting upon, which may decrease the life of such parts. It is therefore known to include a filter in the lubrication system for an engine in order to remove such particles from the lubricant. Typicaiiy the filter is a mechanical filter, which uses a barrier element such as a filter paper to trap the particles, or a centrifugal filter, which relies on centrifugal forces to separate the particles from the lubricant. Such filters only work effectively, however, when the lubricant has a sufficiently low viscosity. In the case of a mechanical filter, if the viscosity of the lubricant is too high, the lubricant will not readily pass through the barrier element. In the case of a centrifugal filter, rotation of the centrifuge required to generate the necessary centrifugal forces is powered by lubricant flowing through small orifices in the centrifuge, and the lubricant cannot readily flow through such orifices if its viscosity is high. In addition, any particles in the lubricant cannot readily move through the lubricant in response to the centrifugal forces. This is a particular problem when the lubricant is cold, on engine startup for example. According to a first aspect of the invention we provide a lubrication system including a lubricant pump, an electrical heater, and controller for controlling the heater and pump, the controller being adapted to decrease the amount of electrical power supplied to the heater and increase the amount of electrical power supplied to the pump as the temperature of the lubricant increases. By virtue of the provision of a heater for heating the lubricant, cold lubricant may be heated and hence its viscosity reduced, and thus the filter may operate more effectively on engine start-up. Moreover, ineffective filtration due to high lubricant viscosity results in a build up in lubricant pressure up-stream of the filter. Lubricant pressure up-stream of the filter thus provides an indirect indication of the filter effectiveness, and controlling operation of the heater and pump according to lubricant pressure upstream of the filter ensures that the correct amount of heat is provided by the heater to bring the lubricant towards a suitable temperature for effective filtration. Preferably the heater is upstream of the filter. Thus the lubricant is heated prior to entering the filter. Preferably the pump is upstream of the filter. The pump may be located between the heater and the filter. Preferably the controller is adapted to divert electrical power from the heater to the pump as the lubricant pressure upstream of the filter decreases. Thus, where the lubricant is cold, and hence has a high viscosity, more power is supplied to the heater to heat the lubricant and less power is supplied to the pump. The pump therefore operates relatively slowly, which is preferable as forcing the high viscosity lubricant through the filter is relatively difficult, and therefore excessive pressure build up upstream of the filter is avoided, and energy is not wasted in creating such a pressure build up. As the lubricant warms up, less power is supplied to the heater, and more to the pump. Thus, as the difficulty in forcing the lubricant through the filter diminishes, the speed of the pump may increase without causing excessive lubricant pressure build up, and energy is not wasted in overheating the lubricant as it approaches an optimum operating temperature. Preferably the controller is adapted to stop supply of electrical power to the heater, when the lubricant pressure up-stream of the filter reaches a predetermined value. The lubrication system may further include a temperature sensor to measure the lubricant temperature. According to a second aspect of the invention we provide a method of operating a lubrication system including a lubricant pump, an electrical heater, and a controller for controlling the heater and pump, the method including the steps of decreasing the amount of electrical power supplied to the heater and increasing the amount of electrical power supplied to the pump as the temperature of the lubricant increases. An embodiment of the invention will now be described with reference to the accompanying drawing which shows a schematic illustration of a lubricant system according to the invention. Referring now to the drawing, there is provided an engine lubrication system 10 including a lubricant pump 12, a filter 14, a heater 16 for heating the lubricant, and controller 18 which is adapted to control operation of the heater 16 and pump 12. The pump 12 is located upstream of the filter 14, and the heater 16 is located upstream of the pump 12. The lubrication system 10 further includes an inlet 22 through which lubricant, typically oil, is returned from the engine, and an outlet 24 through which lubricant is returned to the engine. The pump 12 may be any type of electrically operated pump, such as a gear or vane pump which is driven by an electric motor. The speed of operation of the pump 12, and hence the volume of fluid pumped by the pump 12 per unit time, thus increases as the electrical power supplied to the pump 12 increases. The heater 16 is an electrical resistance heater, and thus the heat output of the heater increases as the electrical power supplied to the heater 16 increases. The filter 14 may be any kind of filtering device, but is typically a mechanical filter including at least one filter paper, or a centrifugal filter. Such filters are well known, and therefore require no further description. The controller 18 is an electrical or electronic controller which controls the supply of electrical power to both the heater 16 and the pump 12, either by means of appropriate passive electrical and/or electromechanical components, or using a programmable controller which makes decisions based on the sensor input, such as a microprocessor. The lubrication system 10 further includes a pressure sensor 20 which is adapted to measure the lubricant pressure up-stream of the filter 14 and down-stream of the pump 12. An output of the pressure sensor 20 is connected to an input of the controller 18, and the controller 18 is adapted to control supply of electrical power to the heater 16 and pump 12 according to the pressure measured by the pressure sensor 20. The lubrication system thus operates as follows. On or before engine start-up, electrical power is supplied to the pump 12, and the pump 12 operates to pump lubricant from the inlet 22 towards the outlet 24. The lubricant passes from the inlet 22, past the heater 16, into an iniet of the pump 12, out of the pump 12, past the pressure sensor 20, and into the filter 14. If the lubricant is cold, and hence relatively viscous, forcing the fluid through the filter 14 is relatively difficult, and thus lubricant cannot pass through the filter 14 as fast as the lubricant is pumped to the filter 14. Thus, the lubricant pressure increases up-stream of the filter 14, and the pressure measured by the pressure sensor 20 provides an indirect indication of the oil temperature. This increase in lubricant pressure is detected by the pressure sensor 20, and the pressure reading is transmitted to the controller 18. In response to the increase in pressure, the controller 18 reduces the electrical power supplied to the pump 12, which thus decreases the speed of operation of the pump 12, and increases the electrical power supplied to the heater 16. Lubricant passing the heater 16 is thus heated by the heater. The amount of electrical power supplied to the heater 16 continues to increase, and correspondingly, the amount of electrical power supplied to the pump 12 decreases, as the lubricant pressure increases. The consequent reduction in pump speed, decreases the rate of increase of lubricant pressure up-stream of the filter 14. As the temperature of the lubricant increases, its viscosity decreases, and it becomes easier for the lubricant to pass through the filter 14. Thus the rate of increase of lubricant pressure detected by the pressure sensor 20 decreases further until the lubricant can pass through the filter 14 at a faster rate than it is being pumped to the filter 14 by the pump 12. At this point the pressure detected by the pressure sensor 20 starts to decrease. In response to this, the controller 18 starts to decrease the electrical power supplied to the heater 16 and increase the electrical power supplied to the pump 12. Thus, the pump speed gradually increases and the energy output by the heater 16 decreases. At a pre-determined pressure level, which corresponds to an optimum lubricant temperature at which the lubricant viscosity is sufficiently low for efficient filtration of the lubricant, no electrical power is supplied to the heater 16 whilst maximum electrical power is supplied to the pump 12, which thus operates at maximum speed. Increasing the electrical power supplied to the heater 16 whilst decreasing the electrical power supplied to the pump 12 or vice versa, may be achieved by diverting electrical power from one to the other. Although the lubricant would in any event eventually be heated to its optimum temperature as the engine warms up, by virtue of the provision of a heater 16 for heating the lubricant, the lubricant reaches its optimum temperature more rapidly than it would without the heater 16. Thus the filter 14 may operate effectively sooner after engine start-up, which may reduce wear on the engine. In addition, as an engine operates more efficiently when the lubricant is at its optimum operating temperature, reducing the time taken for the lubricant to reach its optimum operating temperature also increases the overall efficiency of the engine, and hence reduces fuel consumption and engine emissions. Moreover, controlling operation of the heater 16 and pump 12 according to lubricant pressure upstream of the filter 14 ensures that the correct amount of heat is provided by the heater 16 to bring the lubricant towards a suitable temperature for effective filtration. Diverting the electrical power supplied from the pump 12 to the heater 16 whilst the lubricant is cold is advantageous, as excessive pressure build up upstream of the filter is avoided, and energy is not wasted in creating such a pressure build up. Similarly diverting electrical power from the heater 16 to the pump 12 as the lubricant approaches its optimum operating temperature, is advantageous as energy is not wasted in overheating the lubricant. Since the heater 16 is up-stream of the filter 14 the lubricant is heated just prior to entering the filter 14, and is not cooled in the engine prior to entering the filter 14. Whilst in this example, the controller 18 controls supply of electrical power to the pump 12 and heater 16 according to the lubricant pressure upstream of the filter 14, which, as discussed above, provides an indirect indication of the lubricant temperature, the system may alternatively or additionally include a temperature sensor which measures the lubricant temperature directly. In this case, the controller 18 may control the electrical power supplied to the heater 16 and pump 12 according to the temperature sensor reading, or to a combination of temperature sensor and pressure sensor reading. After a period of use, the filter 14 will become blocked with particles filtered from the lubricant. Where both a pressure sensor 20 and a temperature sensor are provided, the pressure and temperature sensor readings may be used to provide an indication of the extent of filter 14 blockage. To achieve this, the system must be calibrated to provide an indication of the correlation of pressure and temperature readings for a clean filter 14. This information can then be used to obtain a theoretical "clean filter" lubricant temperature from the pressure sensor reading. The "clean filter" temperature may then be compared with the temperature sensor reading, the discrepancy between the two values giving an indication of the extent to which the filter is blocked. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A lubrication system including a lubricant pump, an electrical heater, and controller for controlling the heater and pump, the controller being adapted to decrease the amount of electrical power supplied to the heater and increase the amount of electrical power supplied to the pump as the temperature of the lubricant increases.

2. A lubrication system according to claim 1 wherein the controller is adapted to divert electrical power from the heater to the pump as the temperature of the lubricant increases.

3. A iubrication system according to ciaim 1 or 2 wherein the system further includes a filter and the heater is upstream of the filter.

4. A lubrication system according to claim 2 wherein the pump is upstream of the filter.

5. A lubrication system according to claim 4 wherein the pump is located between the heater and the filter.

6. A lubrication system according to claim 1 wherein the controller is adapted to stop supply of electrical power to the heater, when the lubricant pressure up-stream of the filter reaches a predetermined value.

7. A lubrication system according to any preceding claim, wherein the system further includes a temperature sensor for sensing the temperature of the lubricant.

8. A method of operating a lubrication system including a lubricant pump, an electrical heater, and a controller for controlling the heater and pump, the method including the steps of decreasing the amount of electrical power supplied to the heater and increasing the amount of electrical power supplied to the pump as the temperature of the lubricant increases.

9. A lubrication system substantially as hereinbefore described with reference to and/or as shown in the accompanying drawing.

10. A method of operating a lubrication system substantially as hereinbefore described with reference to and/or as shown in the accompanying drawing.

11. Any novel feature or novel combination of features described herein and/or in the accompanying drawing.