Patent Application
20070084431
This invention relates to internal combustion engines, including but not limited to fluid pumps for internal combustion engines.
Many internal combustion engines use fluid pumps to pump fluid for various engine systems, for example, fuel systems, lubrication systems, and/or hydraulic systems. Many fluid systems pump fluid from a low or an intermediate pressure to a high pressure. A high pressure pump on an engine may be used to pump hydraulic fluid, for example, oil or fuel, to a plurality of injectors. The injectors either inject high pressure fuel, or use high pressure oil to intensify the pressure of low pressure fuel within the injectors. In either case, high pressure fuel is injected into engine cylinders and is mixed with air, often air containing recirculated exhaust gas to provide combustion, as is known in the art. Combustion in a plurality of cylinders provides power that rotates a crankshaft and drives the engine.
Mechanical power generated by the rotation of the crankshaft of the engine is often used in many forms to drive other components, or is converted to other types of power, for example electrical or thermal, to drive other systems on the engine or a vehicle. Power used to drive anything other than the main output shaft of the engine is referred to as “parasitic” loss. Examples of parasitic losses on engines include cooling fans, air compressors, air conditioning compressors, alternators driving various electrical components, fuel and/or oil pumps, and so forth.
A fluid pump on an engine may be driven mechanically from a rotating component of the engine, or may be driven electrically by current generated by an alternator or a generator. Depending on the capacity of the pump, the power output of the engine may be reduced by as much as 10% or more at high engine speeds and loads. Often, the entire output capacity of the pump is not required at high engine speeds, but the direct mechanical connection between the pump and the rotating engine component may not allow for modulation of the pump's power consumption resulting in wasted power from driving the fluid pump. Wasted power takes away from the useful power of the engine, and increases the parasitic losses of the engine thus increasing fuel consumption and engine wear.
Some solutions have been proposed in the past for reducing parasitic losses associated with engine driven pumps. Most systems proposed include use of an electric pump that provides a capability of variable pump power. Such systems rely on driving a pump with an electric motor that receives electrical power from an alternator or a generator driven mechanically by the engine. These electrical pump systems achieve a desirable modulation of the power consumed by the pump, but introduce additional inefficiencies at times when the full output of the pump is required. For example, the addition of an alternator in a pump driving circuit inherently reduces the overall efficiency of the system because there are power losses associated with conversion of mechanical to electrical power in the alternator, and additionally, there are power losses in the transmission of electrical power to the pump motor and the conversion of electrical power back to mechanical power in the motor.
Accordingly, there is a need for more efficient modulation of power consumption in a fluid pump for an internal combustion engine.
An internal combustion engine includes a fluid pump having an inlet, a low pressure outlet, and a high pressure outlet. A reservoir is connected to the high pressure outlet and an oil sump is in fluid communication with the inlet. A pressure regulating valve connects the high pressure outlet and the low pressure outlet. A recirculation passage fluidly connects the low pressure outlet and the inlet. A flow of oil at a high pressure in the high pressure outlet passes through the regulating valve and enters the inlet when the pump is in operation.
In one embodiment, the fluid pump includes a pump housing having the regulating valve integrated thereon. An inlet, a high pressure outlet, and a low pressure outlet, are formed in the pump housing. A first check valve is integrated in the pump housing and is in fluid communication with the low pressure outlet. A second check valve is also integrated in the pump housing and is in fluid communication with an outlet of the first check valve and the inlet of the pump. When the first check valve is open, the inlet of the pump receives an oil flow from the low pressure outlet of the pump.
A method for use with a fluid pump includes the steps of ingesting an oil flow at a low pressure into an inlet of the fluid pump, compressing the oil flow to a high pressure, sending a first portion of the oil flow to a high pressure reservoir, venting a second portion of the oil flow to a low pressure outlet, recirculating an oil quantity from the low pressure outlet to the inlet of the fluid pump through a recirculation path, and mixing the oil quantity with the oil flow.
A typical prior art configuration of an oil circuit for an internal combustion engine is shown in
A rotating crankshaft (not shown) of the base engine 102 drives the low pressure pump 108. A low pressure outlet 114 of the pump 108 is connected to an oil distribution circuit 116. The oil distribution circuit 116 is connected to the base engine 102 to supply oil for lubrication of various moving components, for example, crankshaft bearings, valve train components, and so forth. The supply circuit 116 is also connected to an inlet 118 of a high pressure oil pump 120.
The high pressure oil pump 120 receives oil from the outlet 114 of the low pressure pump 108, and pressurizes the oil and supplies it to a high pressure outlet 122. Typical pressures at the outlet 114 may be between 10 and 50 PSI (70 and 345 kPa), and typical pressures at the outlet 122 may be around 4500 PSI (30 MPa) or more. High pressure oil from the outlet 122 of the high pressure pump 120 passes through a check valve 124 before collecting in a high pressure oil rail or reservoir 126. A desired pressure in the high pressure reservoir 126 is controlled by an injection pressure regulator (IPR) valve 128 that fluidly connects the outlet 122 of the pump 120 with a low pressure drain passage 130. The drain passage 130 receives oil from the IPR valve 128, and drains it back into the sump 104. This process is known as “shunting”, wherein high pressure oil at the outlet of the pump 120 is “shunted” to control the pressure of oil in the reservoir 126.
The reservoir 126 is connected to a plurality of fuel injectors 132 and supplies them with high pressure oil. The oil from the reservoir 126 is used in each of the injectors 132 in conjunction with an intensifier piston (not shown) to elevate the pressure of fuel coming to the injectors through a fuel circuit 134 to a level appropriate for injection into combustion cylinders (not shown) included in the base engine 102.
The high pressure pump 120 is typically gear driven and receives power from the base engine 102, as denoted by a solid bold arrow 136. Because of a direct mechanical connection between the base engine 102 and the high pressure pump 120, a rotational speed of the pump 120 is proportional to a rotational speed of the crankshaft in the base engine 102. Power consumption of the pump 120 increases as a speed of the base engine 102 increases, and can reach 10% or more of the total power output of the engine 100 during operation at high speeds. If the engine 100 is operating at a low load output requirement condition, a fuel quantity consumed by the engine 100 is relatively low, and hence, a high pressure oil quantity used from the reservoir 126 may be far below the oil output capacity of the pump 120. Under such a condition, a large quantity of oil is discharged though the drain passage 130, but the power consumption 136 of the pump 120 remains high. This problem may be rectified in the following solution which describes an apparatus for and method of reducing parasitic power consumption of a fluid pump for an internal combustion engine.
A core engine 200 includes a base engine structure 202. An oil sump 204 contains an oil pool 206. A low pressure oil pump 208 has an oil inlet 210 that collects oil from the oil pool 206 to supply the pump 208. A low pressure outlet 214 of the pump 208 is connected to an oil distribution circuit 216. The oil distribution circuit 216 is connected to the base engine 202 and also connected to an inlet 218 of a high pressure oil pump 220. A first check valve 219 is positioned upstream of the inlet 218 to prevent return flow from the high pressure pump circuit 218.
High pressure oil from an outlet 222 of the high pressure pump 220 passes through a second check valve 224 including a bleed orifice before collecting in a high pressure oil rail or reservoir 226. A desired pressure in the high pressure reservoir 226 is controlled by an IPR valve 228. The IPR valve 228 fluidly connects the outlet 222 with a low pressure outlet 223 and the inlet 218 of the high pressure pump 220 through a recirculation passage 227. The recirculation passage 227 includes a third check valve 229 to prevent back flow to the drain passage. The recirculation passage 227 is in direct fluid communication with the inlet 218, and is disposed downstream of the first check valve 219. Oil in the recirculation passage 227 is at a low to moderate pressure after venting from the IPR valve 228, and enters back into the pump 220 instead of draining into the sump 204 as previously described.
The high pressure pump 220 may be gear driven and receive power from the base engine 202, as denoted by a solid bold arrow 236. Alternatively, the high pressure pump 220 may receive power from an electric motor (not shown) or any other mode used in the art of internal combustion engines to operate a pump for an engine. In the embodiment of
Two main considerations may be addressed for the engine 200 during operation. First, recirculation of oil around the pump 220 through the passage 227 may elevate the temperature of the recirculated oil due to repeated compression cycles. A temperature sensor 238, connected to an engine controller 239 may be included in the passage 227 and monitor the temperature of the oil. In the case when the temperature of oil in passage 227 exceeds a predetermined value during operation of the engine 200, for instance, 240 deg F. (116 deg C.), the electronic controller may command a vent valve 240 to vent oil back into the sump 204 through a vent passage 242 that fluidly connects the recirculation passage 227 with the sump 204. Venting of oil in the passage 227 will allow for a quantity of oil at a lower temperature from the low pressure pump 208 to reach the inlet 218, replace the quantity of oil that was vented through the valve 240, and mix with warmer oil in the recirculation passage 227 thus lowering the overall temperature of oil passing through the pump 220.
Alternatively, an oil cooler 244 may be placed in the recirculation passage 227 and be used instead of or in conjunction with the valve 240 to control the temperature of oil passing through the pump 220.
Second, depending on a control scheme used to operate the IPR valve 228, controllability issues creating instabilities and pressure fluctuations in the recirculation passage 227 may arise. These issues may be related to a feedback loop time and response time of the IPR valve 228 and may be resolved by a placement of an additional vent passage 245 that fluidly connects the IPR valve 228 with the sump 204 and contains a pressure relief valve 246. The pressure relief valve 246 may open to relieve pressure spikes in the recirculation passage 227 that may be created when the IPR valve 228 first opens or at times of drastic change in the speed of the engine 202. The pressure relief valve 246 may be selected to have an opening pressure value that allows it to remain closed during normal engine operation, and only open when a pressure spike is present.
One example of a high pressure oil pump 300 for an internal combustion engine is shown in
A view of the pump 300 with the driving gear removed is shown in
A partial section of the pump 300 is shown in
A detail cut-away view of the check valve 702 in a closed position is shown in
The check valve 702 will open when fluid, in this case oil, enters through the inlet port 704 and pressure in the priming port 713 is low. A flow of oil under pressure into the inlet port 704 will push the valve element 714 toward the stop plug 712 and away from the outlet port 706. With the valve element 714 pushed against the stop plug 706, the spring 716 is extended and the outlet port 706 is opened to allow the flow of oil.
In one embodiment, the valve 702 may serve the function of the first check valve 219 shown in
A pump 800 having integrated check valves and a recirculation passage is shown in partial cut-away in
A second passage 828 fluidly connects an outlet of the first check valve 818 with an outlet 830 of a second check valve 832. The second check valve 832 is configured to open when oil enters the check valve 818 from a pump inlet 834. The second check valve 832 may be integrated with the housing 802, and may include a second tension spring 836, a second valve element 838, and a second plug 840. The second spring 836 is connected to the second valve element 838, and the two are included in a second valve bore 842. The bore 842 may be formed into the housing 802, and is in fluid communication with the second passage 828 and the pump inlet 834. The second plug 840 limits the travel of the valve element 838 in the bore 842 during operation of the valve 832.
During operation of the pump 800, oil may enter through the pump inlet 834 as shown in
A method for recirculation of fluid around a pump is presented in
Additional steps may be advantageous to the operation of the pump. First, oil in the recirculation path coming from the low pressure outlet of the pump may be cooled, for example by use of an oil cooler connected to the recirculation path, before going back into the pump inlet. Second, the temperature of oil in the recirculation path may be monitored and used to control a valve that will vent oil back into the sump of the engine, as described above.
Numerous advantages may be realized with the embodiments described herein. First, power consumption of a high pressure fluid pump may be reduced during periods of engine operation not requiring the full output capability of the pump. These embodiments may help reduce parasitic losses of power for an engine, thus reducing power loss and increasing fuel economy. Impacts to existing fluid systems using a pump may be minimal in that the additional paths and valves needed for this invention are typically small and inexpensive, and can even be integrated into existing pumps.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
