The present invention relates to controlling the output of a variable flow pump. More specifically, the present invention relates to a control system for a variable oil pump used with an engine, with the control system used for controlling the output of the oil pump.
Engines used in motor vehicles typically have a pump in some form which provides lubrication to the engine bearings, as well as other components of the engine. Typically, these oil pumps are driven directly or indirectly by the crankshaft of the engine, and do not have very complex pressure regulation systems. While these systems generally are sufficient, there are several disadvantages. Most notably, because of the simplicity of the pressure regulation system, control over the output of the oil pump and fluid delivery to the various engine parts is somewhat limited.
One example of this lack of control is that there are certain engine operating conditions where the maximum amount of oil flow is not needed for the various engine components. However, because of the lack of flexibility of control of the oil pump, the oil pressure may exceed what is needed under these various operating conditions, which leads to excessive power consumption by the oil pump, and reduced efficiency of the engine. This is mainly because the design of the oil pump is usually in such a manner that, under all engine operating conditions, the oil pump attempts to deliver higher levels of oil pressure and flow required for worst case conditions.
Accordingly, there exists a need for a method of control of a variable flow pump, by using an engine control unit which actuates a solenoid for either direct or indirect control of the oil pump.
The present invention is a variable displacement pump system for delivering precisely controlled oil flow and oil pressure, including a variable displacement pump having an inlet passage, an outlet passage, a first chamber for controlling the displacement of the variable displacement pump, and a second chamber for controlling the displacement of the variable displacement pump. The present invention also includes a fluid control device for receiving fluid from the outlet passage, and selectively delivering fluid to the second chamber.
Fluid is delivered from the inlet passage to the outlet passage from the variable displacement pump, and fluid is also delivered from the outlet passage to the first chamber and the fluid control device. When fluid pressure is greater in the first chamber relative to the second chamber, the displacement of the variable displacement pump will decrease, and when fluid pressure is greater in the second chamber relative to the first chamber, the displacement of the variable displacement pump will increase.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
Referring to the Figures generally, a system for pumping fluid according to the present invention is generally shown at 10. The system 10 has an engine side or an engine 12, a pump side or a variable displacement pump 14, and an oil sump 16. The system 10 is provided for controlling the oil pump 14 with either a variable displacement pump element or a variable output pump element. It should be appreciated that other types of pump systems can be used in the present invention, such as but not limited to other types of vane pumps, gear pumps, piston pumps, and/or the like.
In the system 10 of the present invention, there is at least a lubrication circuit, generally shown at 18, an engine control unit (i.e., ECU) or computer 20. The oil pump 14 draws oil from the oil sump 16 and delivers it at an elevated pressure to the lubrication circuit 18.
The lubrication circuit 18 includes an oil filter 22, and a variable pressure transducer 26. Fluid is delivered to the engine's crankshaft, bearings, connecting rods, and camshafts. While the oil filter 22 and the variable pressure transducer 26 are shown in this embodiment, other embodiments of the present invention may not include the oil filter 22, or the pressure transducer 26. More specifically, the pressure transducer 26 may be eliminated because the system 10 has the ability to operate as an open loop system. The lubrication circuit 18 restrictions are schematically shown by constrictions 24. The lubrication circuit 18 can also optionally contain items such as piston cooling jets, chain oilers, variable cam timing phasers, and cylinder de-activation systems, as are generally known in the art. The lubrication circuit 18 also delivers fluid to a main oil gallery 28, which is part of the engine 12.
The ECU 20 includes electrical inputs for the measured engine speed 30, engine temperature 32, and engine load, torque or throttle 34. The ECU 20 can also have, as shown in the present embodiment, an electrical input for the measured oil pressure 36 from the transducer 26. The ECU 20 also has an output 38 for transferring an electrical control signal that is used to control the oil pump 14.
The oil pump 14 also includes a housing 40 which contains an inlet or a suction passage 42, and an outlet or a discharge passage and manifold 44. The oil pump 14 also optionally includes a pressure relief valve 46 and/or an internal oil filter 48 for cleaning the discharge oil for use inside the oil pump 14. While the present embodiment includes the pressure relief valve 46 and the internal oil filter 48, these devices are not necessary for the operation of the present invention.
The oil pump 14 contains a variable flow pump element, generally shown at 50. The variable flow pump element 50 includes a displacement control pump element, such as an eccentric ring 52. The position of the eccentric ring 52 determines the theoretical flow rate discharged by the pump element 50 at a given drive speed. Two control chambers 54,56 are provided in the housing 40 on opposing sides of the eccentric ring 52. Both of control chambers 54,56 contain fluid of controlled pressure for the intended purpose of exerting a control force on an area of the eccentric ring 52. The first chamber, e.g., the decrease chamber 54, contains pressure applied to the eccentric ring 52 to decrease the flow rate of the variable flow pump element 50, and the second chamber, e.g., the increase chamber 56, contains pressure applied to the eccentric ring 52 to increase the flow rate of the variable flow pump element 50. Disposed within the eccentric ring 52 is a rotor 128 having a plurality of slots 130, each slot 130 receiving a vane 132. The rotor 128 rotates about an axis, and is driven by rotational power received from the crankshaft of the engine 12.
There is also a spring 58 positioned between the housing 40 and the eccentric ring 52 which applies a force to the eccentric ring 52 to bias the eccentric ring 52 toward maximum fluid pumping displacement of the variable flow pump element 50. Also included is at least one channel in the form of channel 60 and channel 62. The decrease chamber 54 is be supplied with oil pressure from either the oil pump discharge manifold 44 via channel 60 or, in an alternate embodiment, at some other point downstream in the lubrication circuit 18 (e.g., usually from the main oil gallery 28) via channel 62.
The oil pump 14 also contains a fluid control device in the form of a solenoid valve module 64 which includes a solenoid valve stage 66 and a pressure regulator valve stage 68. The solenoid valve module 64 is used for controlling the amount of fluid pressure in the increase chamber 56.
The solenoid valve stage 66 includes a solenoid 70, an armature spring 72, and a housing 74. The solenoid 70 includes a coil of electrical wire 76 and a ferrous armature 78, configured so that an electric current passing through the coil 76 generates an electromagnetic field which moves the armature against the compression spring 72 and opens the valve hole 80 in the housing 74, thereby allowing fluid to flow through it.
The pressure regulator valve stage 68 includes a spool 82, a spool spring 84, and an area defining a bore 86 (i.e., in housing 74) for radial containment of the spool 82. The spool 82 has an outer diameter with two annular grooves, a spool supply port 88 and a spool control port 92. The spool supply port 88 is in continuous fluid communication with a housing supply port 90, and the spool control port 92 is in continuous fluid communication with a housing control port 94. The spool supply port 88 is also in continuous fluid communication with a first fluid chamber 100 via a restrictive orifice hole 102. The spool 82 is positioned axially in bore 86 by the resultant force of the control pressure in fluid chamber 100, the spring 84, and the supply pressure in a second fluid chamber 104. The restrictive orifice hole 102 creates a pressure differential between the fluid chamber 104 and the fluid chamber 100, the function of which will be described later.
The channel 60 (or 62 in an alternate embodiment) is connected to a common inlet channel 118 which feeds into the decrease chamber 54. Connected to the inlet channel 118 is a pressure supply channel 120; in this embodiment, the oil filter 48 is included and is located in the pressure supply channel 120. Housing supply port 90 is supplied with oil pressure from the pressure supply channel 120 and, if included, the filter 48; the pressure supply channel 120 receives pressure from the channel 60 (or 62) via the inlet channel 118. The pressure supply channel 120 is connected to a channel 122, the channel 122 is connected to a port 106, and feeds fluid to the fluid chamber 104. The pressure supply channel 120 is also in fluid communication with the housing supply port 90. The lubrication circuit 18 also optionally includes another restrictive orifice 124 in which fluid flows through before flowing into through the port 106. The purpose of the restrictive orifice 124 is for damping the movement of the spool 82 by slowing down the flow of fluid through the port 106.
A change in the axial position of spool 82 will increase or decrease the amount of fluid communication between spool control port 92 and the housing supply port 90, and between the spool control port 92 and a housing drain port 108. This has the resultant effect of regulating the control pressure (e.g., see reference 98 in
Conversely, when the pressure in the decrease chamber 54 is lower than the reference pressure, the pressure in the increase chamber 56 and the spring 58 will move the eccentric ring to increase the pump flow. The pressure regulator valve stage 68 is shown in accordance with one aspect of the present invention to have a total of three fluid communication ports, i.e., the spool supply port 88, the housing supply port 90 and the housing drain port 108.
During engine 12 start-up when there is low fluid pressure, the pump 14 is in the position as shown in
The amount of space in between each of the vanes 132 which expands and contracts will vary as the position of the eccentric ring 52 is changed in relation to the rotor 128. The vanes 132 are in sliding contact with the eccentric ring 52 at all times; the sliding contact between the vanes 132 and the eccentric ring 52 can be maintained by any conventional means, such as centrifugal force, oil pressure underneath the vanes 132, or a vane extension ring (not shown) which moves with the eccentric ring 52, and supports each of the vanes 132.
When the pressure is reduced in the increase chamber 56 and increased in the decrease chamber 54 such that the pressure in the decrease chamber 54 applies a greater amount of force to the eccentric ring 52 compared to the combined force applied to the eccentric ring 52 from the spring 58 and the pressure in the increase chamber 56, the eccentric ring 52 will move downwardly when looking at
In accordance with one aspect of the present invention, the curves have two characteristic zones, e.g., the offset control pressure zone 112, and the variable control pressure zone 114. The transition from the offset control pressure zone 112 to the variable control pressure zone 114 occurs at decreasing supply pressure as the current to the solenoid valve 66 is increased.
In operation, the pump 14 begins at low supply pressure 96 (at start-up). As previously mentioned, at low supply pressure 96, the spring 84 holds the spool 82 to the left in dominance, when looking at
Initially, as the supply pressure 96 increases in the fluid chamber 104 and the fluid chamber 100 simultaneously, the pressure of the fluid flowing into the fluid chamber 104 and the fluid chamber 100 is substantially equal. Therefore, as the supply pressure 96 continues to increase, the force from spring 84, together with the control pressure force in fluid chamber 100, e.g., communicated via restrictive orifice hole 102, overcomes the supply pressure force in fluid chamber 104 and holds the spool 82 to the left when looking at
As the supply pressure 96 continues to increase, the pressure in fluid chamber 100 will also continue to increase, and the fluid pressure in fluid chamber 100 along with the force applied from the ferrous armature 78 will eventually overcome the spring 72 holding the solenoid armature 78 against the housing 74, thereby opening valve hole 80.
When the valve hole 80 is open, and there is a restricted fluid flow through the restrictive orifice hole 102, fluid pressure in fluid chamber 100 is no longer equal to, but is reduced in comparison to the supply pressure 96 at the spool supply port 88. This creates the pressure differential between the fluid chamber 100 and the fluid chamber 104. As the pressure in fluid chamber 100 continues to drop relative to the pressure in fluid chamber 104, the differential pressure acting on the spool 82 in fluid chamber 104 will eventually overcome the combined force applied to the spool 82 from the spring 84 and the pressure in fluid chamber 100, causing the spool 82 to move to the right when looking at
The ECU 20 has the ability to selectively route current through the solenoid coil 76 via the electrical output 38. This results in an electromagnetic field, and biases the armature 78 to move against the spring 72. The bias of the armature 78 alone against the spring 72 does not move the armature 78; however, the force applied from the armature 78 to the spring 72 resulting from the electromagnetic field reduces the amount of pressure needed in the fluid chamber 100 to overcome the force from the spring 72 to move the armature 78 and open the valve hole 80, thereby reducing the pressure in fluid chamber 100, which causes the pressure regulator valve stage 68 and everything upstream of the pressure regulator valve stage 68 (i.e., the common inlet channel 118 and the pressure supply channel 120) to be reduced in pressure as well.
The current chosen is selected based on the desired operating conditions of the system 10. As the amount of current applied to the solenoid coil 76 increases, the amount of pressure needed in the fluid chamber 100 to overcome the force of the spring 72 decreases. The current applied to the solenoid coil 76 is either set to a constant value, or varied to regulate the pressure in fluid chamber 100, and therefore the position of the spool 82. The control pressure 98 is adjusted automatically by the system 10 to maintain the correct pressure in the increase chamber 56 to achieve the target pressure in the common inlet channel 118.
The oil pump 14 still functions without the ECU 20, because the solenoid valve module 64 performs some pressure regulation activity even without electrical power, as shown in the variable control pressure zone 114 in
The oil pump 14 can be operated in an open loop control mode or a closed loop control mode. The oil pump 14 can be operated by the ECU 20 in an open loop control mode because the ECU 20 can be reasonably certain of the oil pressure in the lubrication circuit 18 as a function of current to the solenoid 70 through electrical output 38 from an internal “look up” table in the ECU 20, even without measuring the oil pressure through the transducer 26, because the system is regulating directly according to the feedback pressure in common inlet channel 118 and the pressure supply channel 120.
The oil pump 14 can also be operated by the ECU 20 in a closed loop control mode to actively control the oil pressure by adjusting its electrical signal to the solenoid 70 through electrical output 38 according to software logic control programmed into the ECU 20, and the oil pressure measured in the lubrication circuit 18 by transducer 26. The ECU 20, if desired, has the ability to anticipate increasing oil demand in the lubrication circuit 18. This is accomplished by simultaneously actuating the pump and an oil-consuming engine subsystem, such as variable cam timing or cylinder deactivation. The ECU 20, through the present invention, also has the capability of selectively activating certain pressure-sensitive engine subsystems, by selecting a higher or lower oil pressure for the lubrication circuit 18 depending on any known condition, including but not limited to the measured engine speed 30, engine temperature 32, and/or engine load 34.
Additionally, the oil pump 14 has the ability to be operated in a mixed control mode by combining elements of the previous three control modes. By way of a non-limiting example, it is useful to allow the oil pump 14 to regulate itself without ECU 20 control at conditions outside the range of normal parameters, and then to use open loop control to quickly achieve oil pressure near the desired value, and then use closed loop control to exactly achieve the desired oil pressure.
An alternate embodiment of the invention is shown in
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
This application is a PCT International Application of U.S. Provisional Application No. 60/927,651, filed May 4, 2007. The disclosure of the above application is incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US08/05631 | 5/2/2008 | WO | 00 | 10/27/2009 |
Number | Date | Country | |
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60927651 | May 2007 | US |