Patent Application
20170356327
The present disclosure relates to electric pumps utilized in internal combustion engine coolant circuits and more particularly to a strategy for controlling an electrically powered pump in an internal combustion engine coolant circuit.
The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
The cooling circuit of an internal combustion engine and more particularly coolant flow in the cooling circuit of an internal combustion engine in a motor vehicle is critical not only from the fundamental standpoint of dissipating the heat of combustion to the ambient but also to accurately control the temperature of the engine to optimize performance and fuel economy.
Significant engineering and design effort is directed to these operational parameters, especially the latter given increasingly stringent fuel economy requirements. Unfortunately, even the most sophisticated cooling system configurations are subject to variations caused by, for example, manufacturing and assembly variables and wear and aging of the components such as the pump impeller, the radiator and the hoses. These variations cause variations in system backpressure which can result in flow reduction and temperature variations that deviate from design goals.
With older engines having engine driven coolant pumps (and less stringent performance expectations and requirements) such backpressure variations were of little moment. Today, an increasing number of internal combustion engines, obviously subject to today's performance expectations and requirements, utilize electrically driven coolant pumps, which, unfortunately, are highly sensitive to backpressure variations. A engine cooling system utilizing an electric pump that initially met all heat dissipation and temperature control requirements, as components wear and age and system backpressure changes, may no longer achieve the desired design goals. Because coolant flow and thus temperature and heat dissipation affect cylinder wall and cylinder head temperature, an engine operating at other than design or optimal temperature will compromise fuel economy.
The present invention addresses this problem.
The present invention provides a strategy for controlling an electric pump in an internal combustion cooling circuit or system which compensates for backpressure variations and maintains system operation, especially engine temperature, within design parameters. The method of operation comprises the steps of measuring the coolant temperature, measuring the electrical voltage and current to the electric pump, determining the pump speed and the coolant flow, determining the desired coolant flow, determining a positive correction signal to the flow control valve and electric pump motor if desired flow is less than current coolant flow and determining a negative correction signal to the flow control valve and electric pump motor if desired flow is more than current coolant flow and undertaking this correction to coolant flow. Thus, based upon inferred back pressure in an engine coolant circuit from the data, engine operating temperature can be maintained in spite of short term and long term variations in system flow restrictions and backpressure and thus variations in coolant flow.
It is thus an aspect of the present invention to provide a control method for a cooling system or circuit of an internal combustion engine which compensates for variations in flow restrictions.
It is a further aspect of the present invention to provide a control method for a cooling system or circuit of an internal combustion engine which measures electric coolant pump voltage and current to determine pump speed and flow.
It is a still further aspect of the present invention to provide a control method for a cooling system or circuit of an internal combustion engine which infers system or circuit backpressure from electric pump operational date.
It is a still further aspect of the present invention to provide a control method for a cooling system or circuit of an internal combustion engine which provides a positive correction signal to the flow control valve and electric pump motor if instantaneous coolant flow is less than desired coolant flow.
It is a still further aspect of the present invention to provide a control method for a cooling system or circuit of an internal combustion engine which provides a negative correction signal to the flow control valve if instantaneous coolant flow is more than desired coolant flow.
It is a still further aspect of the present invention to provide a control method for a cooling system or circuit of an internal combustion engine which compensates for variations in system backpressure thereby maintaining design engine operating temperature and other parameters.
It is a still further aspect of the present invention to provide a control method for a cooling system or circuit of an internal combustion engine which compensates for short term and long term variations in system backpressure thereby maintaining design engine operating parameters such as temperature.
Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
With reference to
The coolant passing through the components of the internal combustion engine 12 exits in a coolant line 42 which includes an engine outlet temperature sensor 44. The coolant then enters a first inlet port 48 of a two section coolant control valve 50. A first section 52 of the coolant control valve 50 receives coolant flow from the internal combustion engine 12 through the first inlet port 48 and directs it to either a first exhaust port 54 connected through a line 56 to a radiator 60 or a second (bypass) exhaust port 62 connected to a line 64 which bypasses the radiator 60 and returns coolant to the inlet or suction side of the electric pump 24.
A second section 68 of the coolant control valve 50 receives coolant flow in a second inlet port 72 from both the integrated exhaust manifold 18 and the turbocharger 32 in a line 74 which also communicates with the inlet port 48 of the first section 52 of the coolant control valve 50. A third inlet port 76 of the second section 68 of the coolant control valve 50 is connected to the electric pump 24 through the fluid supply line 28. The second section 68 of the coolant control valve 50 also includes two exhaust ports: a third exhaust port 82 which directs coolant flow to an engine oil heater 84 and a fourth exhaust port 86 which directs coolant flow to a transmission oil heater 88. Return coolant flows from the engine oil heater 84 and the transmission oil heater 88 are carried in the line 64 which communicates with the inlet or suction side of the electric pump 24. The coolant control valve 50 also includes a single, i.e., tandem, spool or flow control element 92 which is linearly and bi-directionally translated by an electric or hydraulic actuator or operator 94.
Both the electric motor 26 of the coolant pump 24 and the linear actuator or operator 94 of the coolant control valve 50 are under the control of an engine control module (ECM) 96 or other, similar global or dedicated electronic control module have I/O devices, static and transient memories and processors or microprocessors as well as associated electronic components.
Turning now to
Turning next to the upper portion 102 of the map 100, as noted, it relates to the first section 52 of the coolant control valve 50. At the full left position of travel of the spool or flow control element 92, all of the coolant flow is directed to the second (bypass) exhaust port 62 connected to the line 64 as indicated by the area 104. As the spool 92 translates to the right, flow through the (bypass) second exhaust port 62 decreases while flow through the first exhaust port 54 connected through a line 56 to the radiator 60 increases. The latter flow is represented by the area 106. At approximately the mid or center position of the spool or flow control element 92 all coolant flow from the first inlet port 48 of the first section 52 of the coolant control valve 50 is directed to the radiator 60. As the spool or flow control element 92 continues to translate to the right, flow through the first inlet port 48 and the radiator 60 begins to decrease while flow through the second (bypass) exhaust port 62 and the line 64 begins to increase, as represented by the area 108, until the limit of travel to the right is reached and all coolant flow bypasses the radiator 60 and flows through the second exhaust port and the line 64.
Referring now to the lower portion 112 of the map 100, it will be appreciated that for a short distance of travel of the spool or flow control element 92 neither of the inlet ports 72 and 76 are open. After this region, the second inlet port 72 from the integrated exhaust manifold 18 and the turbocharger 32 opens rapidly, represented by the area 114, and stays open until the center point of the region or area 106 in the upper portion 102 is reached. At this center point, the second inlet port 72 is closed and the third inlet port 76 connected by the supply line 28 to the electric pump 24 is opened as represented by the area 116. This condition persists for the remainder of translation to the right of the spool or flow control element 92. When opened, the flows from the second inlet port 72 and the third inlet port 76 are provided to both the engine oil heater 84 and the transmission oil heater 88.
With reference now to
Turning now to
A decision point 164 is then encountered which determines whether the speed of the electric motor 26 is at or above a predetermined or design threshold value. If the speed of the electric motor 26 is below the predetermined or design threshold, the decision point 164 is exited at NO and the method 150 terminates at the stop or exit step 160 and repeats. If the speed of the electric motor 26 is at or above the predetermined or design threshold, the decision point 164 is exited at YES and the method 150 moves to a process step 166. It should be appreciated that optimum control is achieved by the present method 150, utilizing current sensing to infer motor speed, when the speed of the electric motor 26 and the pump 24 is at least 4000 r.p.m. and preferably 5000 r.p.m. or higher, as noted above, which is the optimal pump accuracy range.
The process step 166 then determines the pump output or coolant flow which is a function of the speed (r.p.m.) of the pump 24, the electric current drawn or consumed by the electric motor 26 driving the pump 24, the voltage supplied to the electric motor 26. From this data, and utilizing an application specific look up table or similar computational or memory device or application, the present coolant flow is determined. The position of the coolant control valve 50 is also monitored by the control module 96 which may be achieved without feedback by reading the signal provided to the linear actuator or operator 94 or may be provided by feedback from a linear sensor (not illustrated) associated with the actuator or operator 94.
Next, in a decision point 168, the desired coolant flow is compared to the present coolant flow. The desired coolant flow is found in, for example, a look up table or read only memory which is engine specific and based upon prior dynamometer tests. The primary factors utilized to determine the desired coolant flow are engine speed, engine temperature and engine mode as well as other, optional, secondary factors. If the desired coolant flow is less than the present coolant flow such that more heat is being transported out of the engine 12 and its temperature is lower than is optimal, the decision point 168 is exited at NO and the method 150 moves to a process step 172. If the desired coolant flow is greater than the present coolant flow such that less heat is being transported out of the engine 12 and its temperature is higher than is optimal, the decision point 168 is exited at YES and the method 150 moves to a process step 174.
Since the process step 172 is executed when, in the decision point 168, it is determined that the desired coolant flow is less than the present coolant flow and the process step 174 is executed when, in the decision point 168, it is determined that the desired coolant flow is greater than the present coolant flow, it should be appreciated that the two process steps 172 and 174 provide closed loop feedback in opposite directions: the former (172) reducing the coolant flow to the desired level or rate and the latter (174) increasing the coolant flow to the desired level or rate.
Turning first to the process step 172, a flow correction factor FC is computed which is the difference between the desired and currently measured coolant flow. A flow learn value FL which represents all previous corrections as a function of coolant valve position is also computed. Then, a flow multiplier FM which is a correction factor for coolant backpressure based on present coolant valve position is computed by subtracting the flow correction factor FC from the flow learn value FL. The corrected or new pump flow is then computed as the open loop (unrestricted) pump flow times the just computed flow multiplier FM. The computed corrected pump flow signal is then provided to the coolant control valve 50 by the control module 96 to adjust its position and to the electric motor 26 of the coolant pump 24 to provide an appropriate reduction in the coolant flow. The method ends at the stop or exit step 160 and then repeats.
Similar though inverse activity occurs in the process step 174 wherein a flow correction factor FC is computed which is the difference between the desired and currently measured coolant flow. The flow learn value FL which represents all previous corrections as a function of coolant valve position is also computed. Then, a flow multiplier FM which is a correction factor for coolant backpressure based on present coolant valve position is computed by adding the flow correction factor FC to the flow learn value FL. The corrected or new pump flow is then the open loop (unrestricted) pump flow times the just computed flow multiplier FM. The computed corrected or new pump flow is then provided to the coolant control valve 50 by the control module 96 to adjust its position and to the electric motor 26 of the coolant pump 24 to provide an appropriate increase in the coolant flow. The method ends at the stop or exit step 160 and then repeats.
It will thus be appreciated that an internal combustion engine cooling system of circuit having an electrically driven pump and coolant control valve which is operated according to the just described method is capable of not only matching coolant flow to varying operating conditions of the engine such as speed and ambient temperature but is also capable of compensating for short and long term variations in system backpressure that would otherwise interfere with attaining and maintaining optimal system operating temperatures.
The description of the invention is merely exemplary in nature and 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.
