Patent Application
20060255657
This invention relates to fluid systems for internal combustion engines, including but not limited to high pressure fluid systems having a high pressure pump with an inlet throttle to supply fluid to injectors.
Some internal combustion engines have a fluid system to provide fuel or oil to various engine components. Engines typically compress and ignite a mixture of fuel and air in one or more cylinders. The ignited mixture generates rapidly expanding gases that actuate a piston. Each piston usually is connected to a crankshaft or similar device for converting an axial motion of the piston into rotational motion. The rotational motion from the crankshaft may be used to propel a vehicle, operate a pump or an electrical generator, or perform other work. The vehicle may be a truck, an automobile, a boat, or the like.
A typical fluid system includes a low pressure pump that circulates fluid from a sump or a low pressure reservoir to a high pressure pump. The high pressure pump circulates fluid to one or more high pressure reservoirs that supply fluid to injectors. Some hydraulic systems have an inlet throttle on an input side of the high pressure pump. The inlet throttle controls the flow of fluid into the high pressure pump. As the inlet throttle opens, more fluid flows to the high pressure pump. As the inlet throttle closes, less oil flows to the high pressure pump. The inlet throttle is typically biased to a fully open position. During operation, the biasing force of the inlet throttle is usually overcome by a hydraulic force that moves the inlet throttle into a more closed position. An injection pressure regulator on an outlet side of the high pressure pump usually shunts excess fluid back to the sump or low pressure reservoir under normal operating conditions.
Hydraulic feedback loops often generate instability in the operation of the high pressure pump. The instability generally occurs from throttling or reducing the flow of fluid into the high pressure pump when more flow is desired at the outlet of the high pressure pump. Lack of adequate pressure in the hydraulic feedback loop may not open the inlet throttle during engine startup and other operating conditions enough, causing fluid pressure at the outlet of the high pressure pump to be lower than desired. Moreover, many injection pressure regulators have multi-stage elements such as a main stage valve that can generate instability in the high pressure pump. The main stage valve usually is a mechanical pressure relief valve that opens when the fluid pressure is excessively high. The main stage valve discharges or shunts fluid to the sump to reduce the fluid pressure at the outlet of the high pressure pump to a desired pressure during normal operating conditions. The main stage valve can have a strong impact on pressure regulation by discharging a larger amount of fluid through a larger area than the pilot stage valve. The discharged fluid from the main stage valve may have little or no effect on the pressure of the fluid in the hydraulic feedback loop.
The hydraulic feedback loop control of the inlet throttle may be constrained by the physical limitations of a hydraulic-based system. The hydraulic feedback loop may be difficult to fine tune and may have time lags when implementing changes or quick adjustments to the position of the inlet throttle. The hydraulic feedback loop also may be affected by temperature changes and may increase the response time, i.e., the time needed for the inlet throttle to reach a high gain or fully open operation.
Accordingly, there is a need for control of an inlet throttle valve for a high pressure fluid pump that is stable, energy efficient, and has a quick response capability.
A high pressure fluid system for an engine includes a high pressure reservoir fluidly connected to a high pressure pump. The high pressure pump circulates fluid to the high pressure reservoir and has an inlet throttle arranged and constructed to control a fluid flow rate at an inlet of the high pressure pump. A low pressure pump is fluidly connected to the inlet throttle and circulates the fluid from a low pressure reservoir to the inlet throttle.
An inlet throttle for a high pressure pump in a high pressure fluid system of an engine includes a core having a cylindrical bore and a spool valve disposed in the cylindrical bore. The spool valve includes a spool and a spring. The spring biases the spool in a fully open position and a solenoid is disposed on the core. The solenoid is arranged and constructed to move the spool in response to a drive signal.
A method includes the steps of circulating a fluid from a low pressure pump to an inlet throttle, controlling a fluid flow to a high pressure pump through the inlet throttle in response to a drive signal, circulating the fluid from the high pressure pump to a high pressure reservoir, and diverting a portion of the fluid flow when the fluid pressure at the outlet of the high pressure pump exceeds a maximum allowable pressure. The drive signal is responsive to a fluid pressure at an outlet of the high pressure pump.
The following describes an apparatus for and method of directly controlling an inlet throttle placed on an inlet to a high pressure fluid pump of an internal combustion engine. A schematic diagram of a fluid system 100 for an internal combustion engine is shown in
The high pressure pump 106 has a check valve 120, a ferry valve 122, and a relief valve 124. The check valve 120 may be the lip seals of the high pressure pump 116. The ferry valve 122 allows fluid to fill the high pressure reservoir 110 when the fluid cools and contracts after the engine shuts down. The relief valve 124 discharges fluid into the low pressure reservoir 104 when the pressure of fluid on the outlet side of the high pressure pump 116 becomes excessively high and exceeds a maximum allowable pressure. Under normal operating conditions, the relief valve 124 is expected to be closed and isolate fluid at a high pressure on the outlet of the high pressure pump 106 from fluid at a low pressure in the low pressure reservoir 104.
The engine control module 118 may have one or more microprocessors and electrical circuitry that monitor operation parameters of the engine. The engine control module 118 provides a command or drive signal to the inlet throttle 114 that is responsive to the fluid pressure in the high pressure fluid reservoir 110. The engine control module 118 monitors an electrical signal from the sensor, for example, an injection control pressure (ICP) sensor 126 located on the high pressure reservoir 110. The engine control module 118 may monitor the electrical signal continuously or intermittently such as with a sampling algorithm or the like. The electrical signal from the ICP sensor 126 is responsive to the fluid pressure in the high pressure reservoir 110. The fluid pressure in the high pressure reservoir 110 is expected to be substantially equal to or within 5% of the pressure at the outlet of the high pressure pump 116. The engine control module 118 may monitor other electrical signals from other sensors disposed at other locations of the engine, for instance sensors placed on the outlet side of the high pressure pump 116, or sensors placed at other locations on the engine. The drive signal may be responsive to other engine and vehicle operating parameters.
A longitudinal, cross-section view of an inlet throttle 201 disposed, for example, in a high pressure pump housing 203 is shown in
The inlet throttle 201 has a solenoid 205, a valve assembly 207, and a spool assembly 209. The solenoid 205 is mounted on one end of the valve assembly 207. The spool assembly 209 is disposed in a cylindrical bore 211 formed in the other end of the valve assembly 207 as shown in
The solenoid 205 includes a solenoid housing 217, a bearing liner 219, a magnetic yoke 221, a bobbin 223, an armature 225 having passages 226, and a pin 227. The solenoid 205 also has electrical connections for connecting the solenoid 205 with an engine control module. The solenoid 205 may have other configurations. The solenoid housing 217 may be made from an electrically insulative material. The bearing liner 219 may be made from an electrically insulative and wear resistant material. The bobbin 223 is wound with a coil of electrically conductive material such as copper wire or the like. The coil may be wound on a substructure made of an electrically insulative material. The coil may advantageously be encased in an electrically insulative material. The armature 225 has a pin pocket 229. The pin pocket 229 is arranged along the axis of the armature 225. The armature 225 may be made from a magnetic material such as iron or the like. The pin 227 is cylindrical. The pin 227 has an outside diameter essentially the same as or less than the diameter of the pin pocket 229 in the armature 225. The pin 227 may be made of an electrically insulative material.
When the solenoid 205 is assembled, the magnetic yoke 221 is disposed in the solenoid housing 217. The bearing liner 219 is disposed in the solenoid housing 217 through the magnetic yoke 221 as shown. The bobbin 223 is disposed in the solenoid housing 217 adjacent to the bearing liner 219. The pin 227 is disposed in the pin pocket 229.
The valve assembly 207 has core 231, an first o-ring 233, a second o-ring 235, and a third o-ring 237. The core 231 has a flange section 239. The valve assembly 207 may be made from an electrically insulative material. The core 231 has a step 241 between a second circumferential groove 243 and a third circumferential groove 245 on its exterior surface. The core 231 has a cavity 247 opposite the flange section 239 and on the side of the solenoid 205. The step 241 is adjacent to the entrance chamber 215 when the inlet throttle 201 is disposed in the pump bore 213. The second o-ring 235 is disposed in the second circumferential groove 243. The third o-ring 237 is disposed in the third circumferential groove 245. The cylindrical bore 211 has an opening 249 opposite the cavity 247, and an interior circumferential channel 251 between the opening 249 and the flange section 239. One or more inlets or inlet holes 253 extend from the interior circumferential channel 251 to the step 241. The inlets 253 may be arranged equidistantly along the interior circumferential channel 251 and fluidly connect the opening 249 with the entrance chamber 215. The core 231 has a valve seat 255 in the cylindrical bore 211 near the flange section 239.
The flange section 239 has a pin passage 257 between the cylindrical bore 211 and the cylindrical cavity 247. The pin passage 257 extends essentially along the axis of the core 231. The pin passage 254 has a larger diameter than the pin 227. The flange section 239 forms one or more passages 259 between the cylindrical bore 211 and the cylindrical cavity 247.
The spool assembly 209 includes a spool 261, a spring 263, a retaining plate 265, and a retainer clip 267. The spool assembly 209 may be made of metal, plastic, a like material, or a combination thereof. The spool 261 forms a spool bore 269 with an opening 271 at one end and a spool base 273 at the other end. The spool base 273 has spool passages 275 that fluidly connect the spool bore 269 and the cylindrical bore 211. The spool 261 may advantageously form one or more gain notches 277 at the spool opening 271 as shown in
When the inlet throttle 201 is assembled, the solenoid 205 connected with the core 231 adjacent to the flange section 239. The first o-ring 233 engages and seals the bearing liner 219. The armature 225 is arranged and constructed to move in the cylindrical cavity 247. The pin 227 extends through the pin passage 257 in the flange section 239.
The spool assembly 209 is disposed in the cylindrical bore 211 of the core 231. The spool assembly 209 is disposed between the valve seat 255 and the interior circumferential groove 251 with the spool base 273 oriented toward the flange section 239. The spring 263 biases the spool 261 away from the retaining plate 265 and toward the valve seat 255.
During operation, the spool 261 advantageously moves within the cylindrical bore 211 and closes the interior circumferential channel 251 by partially or fully covering or blocking the interior circumferential channel 251. The inlet throttle 201 may position the spool 261 in a fully open position, a partially closed position, or a fully closed position in response to a drive or command signal from the engine control module 118.
The inlet throttle 201 is in a fully open position when the spool 261 is adjacent to the valve seat 255. In the fully open position, the engine control module advantageously provides a weak or no drive signal to the solenoid 205. A drive signal is weak when it does not energize the solenoid 205 sufficiently to overcome the force of the spring 263 which biases the spool 261 toward the valve seat 255. The spool 261 pushes against the pin 227 and holds the armature 225 in position. The inlet throttle 201 is capable of providing fluid to the high pressure pump with little or no loss of pressure. The fluid flows from the low pressure pump into the entrance chamber 215. The fluid flows from the entrance chamber 215 through the inlets 253 and into the interior circumferential channel 251. The fluid flows from the interior circumferential channel 251, past the spool 261, the gain notches 277, and into the cylindrical bore 211. The fluid flows from the cylindrical bore 211, through the retainer 265, and out of the inlet throttle 210 to the high pressure pump through the opening 249. Some fluid may flow from the cylindrical bore 211 through the spool passages 275, the passages 259, and the armature passages 226 to lubricate the solenoid 205 and equalize the pressure on either side of the spool 261 to advantageously improve controllability and reduce response time.
The inlet throttle 201 is in a fully closed position when the spool 261 fully covers or blocks the interior circumferential channel 251 as shown in
The inlet throttle 210 is in a partially closed or partially open position when the spool 261 is between the fully open and fully closed positions. In a partially closed position, the spool 261 partially covers or blocks the interior circumferential channel 251. The drive signal from the electronic control module energizes the solenoid 205 to move the armature 225 at least partially into the cylindrical cavity 247. The armature 225 pushes the pin 227 against the spool 261, which moves the spool 261 toward the opening 249 and into the position that partially blocks or covers the interior circumferential channel 251. In the partially closed position, the spool 261 controls or throttles the fluid flow from the interior circumferential channel 251 into the cylindrical bore 211 thus reducing or restricting the fluid flow into the high pressure pump.
The gain notches 277 may be used to further control fluid flow through the inlet throttle 201. When the spool 261 moves from a fully closed to a partially closed or fully open position, the spool 261 uncovers the interior circumferential channel 251. Fluid flow from the interior circumferential channel 251 into the cylindrical bore 211 depends on the uncovered surface area of the interior circumferential channel 251. When the uncovered surface area increases, fluid flow increases. When the uncovered surface area decreases, fluid flow decreases. The uncovered surface area is determined by the stroke or position of the spool 261 in the cylindrical bore 211. Without the gain notches 277, the uncovered surface area changes uniformly as the stroke changes (i.e., the proportional change in the uncovered surface area may be linear as the spool 261 uncovers or covers the interior circumferential channel 251). With the gain notches 277, the uncovered surface area does not change uniformly as the stroke changes (i.e., the proportional change in the uncovered surface area is non-linear and varies as the spool 261 uncovers or covers the interior circumferential channel 251). The gain notches 277 may be configured to change the uncovered surface as required, for example, the rate of change of surface area versus stroke could exponential.
The gain notches 277 skew the shape of the graph to deviate from a straight line, and may be appropriately shaped to provide other relationships between the stroke position of the spool 261 and the uncovered surface area of the interior circumferential channel 251. At stroke position X, the spool 261 is at a fully closed position, i.e., the solenoid 205 is fully extended and the spool 261 fully covers or blocks the interior circumferential channel 251 as shown in
At stroke position Z, the spool 261 is at a fully open position as shown in
One advantage of this invention is the elimination of a pressure control valve that typical systems use at the outlet of the high pressure pump to control fluid pressure at the high pressure pump outlet. The elimination of the pressure control valve also eliminates the typical shunting of high pressure fluid that effectively controls the pressure in traditional systems. Fluid entering the high pressure pump is pressurized and used in the high pressure reservoir, under normal operating conditions. Moreover, the response time and controllability of the high pressure fluid system is improved overall, thus improving overall system efficiency. The response time, i.e., the time lag between opening and closing the throttle valve, is reduced by the use of an electronic solenoid actuator. Typical systems -have relatively increased response times because the motive force of their inlet throttles is hydraulic pressure acting on a surface. The response time in traditional systems depends on the required to build hydraulic pressure. The response time for the inlet throttle of this embodiment does not depend on hydraulic pressure because the motive force for the inlet throttle is an electronic actuator. In one embodiment, the actuator is arranged to move the inlet throttle from an open to a closed position in about 150 ms.
An additional advantage of this embodiment is improved stability in the operation of the inlet throttle. With the pressure equalized on either side of the spool, the spool is balanced, the force required to move the spool is reduced, and additionally the spool is advantageously less prone to instability due to pressure fluctuations. A balanced spool configuration also permits low power consumption in the solenoid.
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.
