WO2013003950A1

WO2013003950A1 - System and method for pumping coolant through an internal combustion engine for a vehicle

Info

Publication number: WO2013003950A1
Application number: PCT/CA2012/000649
Authority: WO
Inventors: Zbyslaw Staniewicz
Original assignee: Litens Automotive Partnership
Priority date: 2011-07-04
Filing date: 2012-07-04
Publication date: 2013-01-10
Also published as: CN103608557A; CN103608557B

Abstract

In an aspect, the invention is directed to a system and method for pumping coolant through an internal combustion engine for a vehicle. The system includes a water pump and a control system that is programmed to: a) determining a selected target coolant temperature; b) determining the actual coolant temperature; c) selecting an average flow rate for the water pump that is in at least some situations non-zero and lower than the maximum possible flow rate; and d) controlling the operation of the water pump to provide the selected average flow rate by alternately starting and stopping the water pump to bring the actual coolant temperature towards the target coolant temperature.

Description

Title: SYSTEM AND METHOD FOR PUMPING COOLANT THROUGH AN INTERNAL COMBUSTION ENGINE FOR A VEHICLE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Applications

No. 61/504,283, filed July 4, 2011 and 61/569,278, filed December 11, 201 1, the disclosures of both of which are incorporated by reference as if fully set forth in detail herein.

FIELD

[0002] The present invention relates to vehicles with liquid-cooled internal combustion engines and more particularly to vehicles with liquid-cooled internal combustion engines that employ a water pump that includes a wrap-spring clutch.

BACKGROUND

[0003] Currently most vehicles have liquid-cooled internal combustion engines, wherein a water pump that is driven from the engine pumps coolant constantly through a cooling circuit constantly. The cooling circuit typically consists of a first loop in which coolant leaving the engine is transported through the radiator and a second loop in which coolant leaving the engine is transported through a cabin heater core. The proportion of the flow that passes through each circuit is controlled by a thermostat-actuated valve (which may simply be referred to as the thermostat), which begins to open at a selected temperature and which progressively further to divert more flow through the radiator as coolant temperature rises further above the selected temperature. Typically, the thermostat is set for a relatively low temperature, so as to ensure that sufficient cooling is provided under all circumstances. This, however, causes the engine to operate at an unnecessarily low temperature in most circumstances, which is not ideal for the combustion efficiency and exhaust emissions associated with the engine. Furthermore, the water pump, which is on at all times regardless of coolant temperature, draws power from the engine and is a parasitic loss whenever it is on.

[0004] A variable speed electric water pump could be used to provide greater control over the flow of coolant, which is advantageous, however such water pumps can draw a significant amount of electrical power for their operation, as well as adding significantly to the cost of the thermal management system for a vehicle. Additionally, a loss of electrical power results in a loss of coolant flow, which is, of course, highly detrimental to the engine.

[0005] It would be beneficial to provide a thermal management system for a vehicle that could control coolant flow similarly to using a variable speed electric water pump, but that at least partially addressed the issues identified above.

SUMMARY

[0006] In a first aspect, the invention is directed to a method of control of a water pump for pumping coolant through an internal combustion engine for a vehicle, comprising: a) determining a selected target coolant temperature; b) determining the actual coolant temperature; c) selecting an average flow rate for the water pump that is in at least some situations non-zero and lower than the maximum possible flow rate; and d) controlling the operation of the water pump to provide the selected average flow rate by alternately starting and stopping the water pump to bring the actual coolant temperature towards the target coolant temperature.

[0007] In another aspect, the invention is directed to a system for pumping coolant through an internal combustion engine for a vehicle, comprising: a water pump; and a control system programmed to carry out the method described above.

[0008] In another aspect, the invention is directed to a method of controlling a water pump for a vehicle having an internal combustion engine, wherein the water pump has a maximum possible flow rate of coolant associated therewith, the method comprising: a) sensing whether the engine has been started; b) selecting an average flow rate of the coolant for the water pump wherein the selected average flow rate is in at least some situations non-zero and lower than the maximum possible flow rate; and c) controlling the operation of the water pump to provide the selected average flow rate of the coolant by alternately starting and stopping the water pump until the temperature of the engine is determined to be at least a selected target engine temperature.

[0009] In another aspect, the invention is directed to a method of controlling a water pump for a vehicle having an internal combustion engine and a temperature sensor positioned for detecting the temperature of coolant. The water pump has a maximum possible flow rate of coolant associated therewith. The method comprises: a) sensing whether the engine has been started;

b) activating the water pump for a selected period of time to send coolant from the engine a selected distance to ensure that the coolant from the engine reaches the temperature sensor, while keeping an average flow rate of the coolant below the maximum possible flow rate;

c) taking a reading from the temperature sensor after the coolant from the engine has reached the temperature sensor; and

d) turning off the water pump for another selected period of time.

[0010] In another aspect, the invention is directed to a method of defrosting a windshield of a vehicle after engine startup, comprising: a) delaying circulation of coolant from an engine through a heater core until a selected time after engine startup; and

b) at the selected time, initiating circulation of coolant from the engine through the heater core to heat an air flow passing through the heater core and into a cabin of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Aspects of the present invention will now be described by way of example only with reference to the attached drawings, in which:

[0012] Figure 1 is a schematic illustration of a vehicle with a thermal management system in accordance with an embodiment of the present invention;

[0013] Figure 2a is an end view of an engine in the vehicle shown in Figure 1 ;

[0014] Figure 2b is an exploded perspective view of a water pump that is driven by the engine;

[0015] Figure 3 is a flow diagram illustrating a method of controlling the water pump shown in Figure 2b during a warm-up phase of operating the vehicle;

[0016] Figure 4 is a flow diagram illustrating an alternative method of controlling the water pump shown in Figure 2b during the warm-up phase of operating the vehicle;

[0017] Figures 5a and 5b are magnified views of a portion of the engine shown in

Figure 2a, illustrating the mitigation of a hot spot using the method illustrated in Figure 4;

[0018] Figure 6 is a flow diagram illustrating a method of controlling the water pump shown in Figure 2b during a driving phase of operating the vehicle;

[0019] Figure 7 is a flow diagram illustrating an alternative method of controlling the water pump shown in Figure 2b during a driving phase of operating the vehicle;

[0020] Figure 8 is a flow diagram illustrating a method of controlling the fan for the radiator of the vehicle shown in Figure 1 ; [0021] Figures 9a-9c are graphs showing test data for the vehicle using variations of the methods illustrated in Figures 4 and 6;

[0022] Figure 9d is a graph showing test data for a vehicle with a prior art thermal management system;

[0023] Figure 10 is a graph showing test data for a vehicle using variations of the methods illustrated in Figures 3 and 4, and also test data for a vehicle using a prior art thermal management system;

[0024] Figure 11 is a schematic illustration of a vehicle with a thermal management system in accordance with another embodiment of the present invention; and

[0025] Figure 12 is a graph showing the temperature of an air flow into the cabin based on several different scenarios.

DETAILED DESCRIPTION

[0026] Reference is made to Figure 1 , which shows a schematic representation of a vehicle 10 with an internal combustion engine 12, a water pump 14, a cabin heater core 15, a radiator 16, a fan 18 and a control system 20, in accordance with an embodiment of the present invention.

[0027] The water pump 14 pumps coolant through the engine 12 to control the temperature of the engine 12. Downstream from the engine 12, the coolant flow is divided into a first loop in which the coolant passes through the radiator 16 and then back to the inlet of the water pump 14, and a second loop in which the coolant passes through the heater core 15 and then back to the inlet of the water pump 14. A thermostat 21 is provided in the first loop as it would be in many vehicles today, for controlling the distribution of coolant between the first and second loops. A heater fan 22 is provided and is selectively operable to extract heat from coolant flowing through the heater core 15 for use in heating the vehicle cabin, shown at 24, and for defogging the windows in the cabin 24. Coolant flowing through the radiator 16 is cooled via a flow of air passing over the radiator. The fan 18 controls the air flow passing over the radiator 16, and thus controls the amount of cooling that is provided to the coolant flow through the radiator 16. This layout is similar to the coolant system layout in many vehicles today, which facilitates the incorporation of the components of the invention into current vehicles.

[0028] The control system 20 controls the operation of the water pump 14, the fan

18 and the heater fan 22. The control system 20 may be made up of one or more separate control units including but not limited to an engine control unit, a vehicle control unit, and a separate control unit that is separate from the engine control unit and vehicle control unit. The control system 20 is shown schematically as being a single box in Figure 1 , however it will be understood that this is a schematic representation only and that it may be made up of multiple boxes which communicate with each other. The control system 20 may include a processor and a memory, and code and data in the memory. The code and data may be used to carry out one or more methods which are described further herein. To carry out the one or more methods, the control system 20 receives input from one or more sources and issues one or more outputs to one or more receiving devices, as described further herein.

[0029] The vehicle cabin 24 may have therein a cabin heating request control element 26 (e.g. a selection dial) for use in sending a cabin heating request to the control system 20, and may have a window defogging/defrosting request control element 28 (e.g. a button or a selection dial) for use in sending a window defogging/defrosting request to the control system 20.

[0030] The water pump 14 may be any suitable type of water pump 14. For example, referring to Figure 2a, the water pump 14 may be driven by an accessory drive belt 30, which is itself driven by the crankshaft of the engine 12.

[0031] Referring to Figure 2b, the water pump 14 includes a housing 32, a pump rotor 34 that is rotatable within the housing 32 to pump coolant, an input member 36 such as a pulley that is driven by the accessory drive belt 30 and that is operative ly connectable to the rotor 34 through a wrap spring clutch 38 which incorporates a wrap spring 39. An electromagnetic coil 40 is provided on the housing 32 and is controllable to selectively draw an armature plate 42 against a friction surface 44. The armature plate 42 is connected to one end of the clutch spring 39. The other end of the clutch spring 39 is engageable (i.e. abuttable) with the pump rotor 34. In a pump-stopped condition, the input member 36 may be rotating (assuming the engine 12 is on), but the wrap spring 39 is spaced from the inner surface (shown at 45) of the input member 36 and so the wrap spring 39 is not driven by the input member 34. The electromagnetic coil 40 is energized to hold the armature plate 42 against the friction surface 44. To start rotation of the pump rotor 34, the electromagnetic coil 40 is de-energized. The armature plate 42 moves away from the friction surface 44 by a biasing member (e.g. a spring). A teaser plate 46 which is connected to the armature plate 42 is urged against a friction surface (not shown in Figure 2b) on the input member 36, which causes rotation of the teaser plate 46 and armature plate 42. The rotation of the armature plate 42 drives rotation of the first end of the clutch spring 39. The second end of the clutch spring 39 which is abutted with the pump rotor 34, however, resists rotation due to inertia of the pump rotor 34 and of the coolant that is to be pumped by it. As a result, the first end of the clutch spring 39 rotates in a driving direction relative to the second end thereof, which causes the clutch spring 39 to expand radially until the clutch spring 39 engages the inner surface of the input member 36. Once there is engagement between the clutch spring 39 and the input member 36 the input member directly drives the clutch spring 39, which in turn drives the pump rotor 34. To stop the rotation of the pump rotor 34, the electromagnetic coil 40 is energized which draws the armature plate 42 against the friction surface 44, which slows the armature plate 42, which in turn slows the first end of the clutch spring 39. The second end of the clutch spring 39 however, continues momentarily without decelerating due again to inertia. Thus there is relative movement of the first end of the clutch spring 39 in a direction opposite to the driving direction, relative to the second end of the spring 39. This causes the clutch spring 39 to uncoil and therefore to shrink radially, which in turn causes it to space itself from inner surface of the input member 36. A suitable water pump is shown and described in PCT publication WO2010054487, the contents of which are incorporated herein by reference.

[0032] In Figure 2b the wrap spring clutch 38 is shown to be of the type where engagement of the wrap spring 39 with the takes place on its outer diameter and at one of its ends. This is advantageous in that the wrap spring 29 is not stressed as it would be in some other types of wrap spring clutch, such as one where the wrap spring constricts to engage the outer surfaces of two co-axial shafts, or one where the wrap spring expands to engage the inner surface of two co-axial hollow shafts. In these other types of clutch, the wrap spring incurs shear at the edges of the shafts. However, it will be understood that such clutches could still be used in place of the clutch 39 shown in Figure 2b.

[0033] When an engine, such as engine 12, is at a certain optimal temperature the combustion efficiency of the engine 12 is relatively high and emissions from the engine 12 are relatively low. Below that temperature the engine 12 consumes a relatively large amount of fuel and has higher emissions. It is therefore desirable to bring the engine 12 up to the optimal engine temperature as quickly as possible.

[0034] Reference is made to Figure 3. When the vehicle 10 is started up, the temperature of the engine 12 is below the optimal engine temperature and as a result, the emissions from the engine 12 are relatively high and the engine 12 consumes a relatively large amount of fuel. The control system 20 may be programmed to control the operation of the water pump 14 in a way that permits a relatively quick warm up of the engine 12 to the optimal engine temperature. The control system 20 may be programmed according to the method 50 shown in Figure 3, which represents a warm-up algorithm. The method begins at step 52. At step 54 the control system 20 senses whether the engine 12 has been started. This may be done in any suitable way. For example, the control system 20 may receive signals from an RPM sensor on the crankshaft to determine whether the engine RPM is greater than zero. At step 56 the control system 20 controls the water pump 14 to ensure that the water pump 14 is off. In the embodiment shown in Figure 2, this is carried out by energizing the electromagnetic coil 40. By keeping the water pump 14 off, there is no coolant flow through the engine 12 to transport heat away from the engine 12 and so the engine 12 heats up relatively quickly. At step 58 the control system 20 determines whether the engine has reached the optimal temperature. To determine this a temperature sensor 60 (Figure 1) may be provided in a coolant conduit in or very near the engine 12, preferably near the top of the engine 12 and preferably in the cylinder head as opposed to being in a plastic fitting on the engine 12. The temperature sensor 60 is positioned to sense coolant temperature. The engine temperature can be determined based on the coolant temperature and other factors, such as the engine load and vehicle driving pattern. The engine load may be determined based on any suitable criteria, such as the amount of fuel being consumed by the engine 12. This relationship between engine temperature and coolant temperature can be determined empirically by testing a test vehicle during vehicle development. Thus the control system 20 sets a target temperature for the temperature sensor 60 that is representative of a target temperature for the engine. The target temperature for the temperature sensor 60 is represented by the variable Ttarget.

[0035] If the control system 20 determines that the engine 12 has not yet reached its target temperature, then the control system 20 may do nothing until it determines that the target temperature has been reached. Once the target temperature has been reached, the control system 20 may end the warm-up algorithm (i.e. method 50) and may then carry out a driving algorithm, examples of which are shown in Figures 5 and 6.

[0036] In order to select the selected target temperature Ttarget, the control system 20 may use any suitable method. As noted above, there is a relationship between the temperature of the coolant (which is measured by temperature sensor 60) and the temperature of the engine 12. An example relationship for an exemplary engine is shown in graph 61. In general, as the engine load increases, the engine produces more heat, and so the target coolant temperature Ttarget decreases since coolant at a lower temperature would have capacity to draw more heat away from the engine. As a hypothetical example for illustration purposes only, for an engine at very high load and therefore producing a lot of heat, a coolant temperature of 60 degrees C might imply an engine temperature of 1 10 degrees C. By contrast, when the same engine is at idle and producing very little heat, the coolant temperature would have to be 100 degrees C to imply an engine temperature of 1 10 degrees C. The selected target coolant temperatures may be determined during engine development by testing a sample engine 12 to assess its fuel efficiency and emissions under different loads and operating temperatures. A table of data may be developed which may be stored in memory for the control system 20 to use as a lookup table to select target coolant temperatures based on engine load.

[0037] Given that engine load can vary during use of the vehicle 10, the control system 20 may repeatedly redetermine the selected target temperature Ttarget at some selected time interval and may then determine whether the actual coolant temperature has reached the target temperature Ttarget. A suitable time interval may be, for example, 5 seconds.

[0038] It is efficient to keep the water pump 14 off during the warming up of the engine. However when the water pump 14 is off, no heat is transferred from the engine 12 to the heater core 15 and thus there is no heat for heating the cabin 24. It will be noted that in some situations, it may take 10-15 minutes for the engine 12 to warm up to the target engine temperature, depending on several factors, such as the engine load on the engine 12 while the vehicle 10 is being driven during this phase. When the ambient temperature Tamb is sufficiently low however, the vehicle occupants may desire to heat the cabin 24 for their comfort. Additionally or alternatively, the vehicle occupants may desire to send heat to the windshield to defog or defrost the windshield. To provide the capability of sending heat to the cabin 24 for occupant comfort or for defogging/defrosting purposes, the control system 20 may carry out a method shown at 80 in Figure 4. The method 80 starts at step 82. At step 84, the control system 20 senses whether the engine 12 has been started, in similar fashion to step 54. When it does sense that the engine 12 has been started, step 86 is carried out, whereupon the control system 20 determines whether a defrost/defog action is needed, based on one or more criteria. One such criterion is whether a defog/defrost action or a heating action has been actively requested by the vehicle occupants using the cabin heating request control element 26 and/or the window defogging/defrosting request control element 28. Another criterion is whether a defog/defrost action is effectively being requested by the vehicle occupants activating the air conditioning compressor while the ambient temperature is relatively low (indicating the vehicle occupants want the air conditioning system to be on for the purpose of reducing humidity in the cabin 24 as opposed to wanting the air conditioning system to be on for the purpose of cooling the cabin for comfort reasons). Another criterion is whether the ambient temperature could warrant a request for heating or for defog/defrost. If a defrost defog action is determined to needed based on one of more of the criteria above, the control system 20 proceeds to step 100, and will establish a cycle of operation of the water pump 14 where the operation of the water pump 14 alternates between a first period of time during which the water pump 14 is on and transfers heat from the engine to the heater core 15, and a second period of time during which the water pump 14 is off. In this way, the water pump 14 is controlled to generate a selected average coolant flow through the engine 12 that is a selected portion of the maximum possible flow rate of the water pump 14. The maximum possible flow rate of the water pump 14 is the flow rate of the water pump 14 when it is on. The cycle time, which may be represented by a variable named PWM_period, is the sum total of the first and second periods of time. The first period of time may be represented by the variable PWM duty. In an exemplary embodiment, the cycle time PWM_period may be 5 seconds.

[0039] At step 88 the value of PWM duty is determined. In the exemplary embodiment, the value of PWM duty may be determined based on the ambient temperature (represented by variable Tamb), which may be determined using a temperature sensor 102 as shown in Figure 1. An example of a relationship between PWM duty and ambient temperature is shown in graph shown at 104 in Figure 4. As shown in the graph 104, when Tamb is at or is less than a first ambient temperature (e.g. 5 degrees C), the control system 20 selects an average coolant flow rate of 20% of the maximum possible flow rate (which translates into a value for PWM_duty of 1 second for a cycle time of 5 seconds). In a situation where the value of Tamb is greater than or equal to a second ambient temperature (e.g. 20 degrees C), the control system 20 may select a value of zero for PWM duty (i.e. which means that the water pump 14 is turned off for the 5 second duration of the cycle), because at or beyond the second temperature heating the cabin 24 and defogging/defrosting the windshield may be deemed unnecessary. The curve shown at 106 in the graph 104 illustrates an example of the relationship between the value of PWM_duty and ambient temperature Tamb for values of Tamb between the first ambient temperature and the second ambient temperature. In the example curve 106, the relationship is linear however in some embodiments, a nonlinear relationship may be used. Once the value of PWM duty is selected by the control system 20 (e.g. via a lookup table), the algorithm may proceed to step 90 where it turns on the water pump 14 (i.e. the electromagnetic coil 40 shown in Figure 2 is deenergized) for the first period of time if the value of PWM duty is non-zero, or step 92 where it keeps the water pump 14 off (i.e. the coil 40 is energized) until the cycle time is completed. If it does carry out step 90, then it will afterwards proceed to step 92 where it will turn off the water pump 14 until the cycle time is completed.

[0040] If at step 86, the control system determines that a request for a defrost/defog action or heating action is not needed, then it sets a value for PWM duty of zero and proceeds to step 92, where it keeps the water pump 14 off for the duration of the cycle.

[0041] The selected average coolant flow rates established in the graph 104 may be selected so as to provide a sufficient amount of heating to the cabin to be considered acceptable to most vehicle occupants, and/or to provide a sufficient amount of defogging/defrosting to prevent the windshield of the vehicle from fogging during use of the vehicle. The average coolant flow rate that satisfies these conditions may be determined empirically by conducting tests in a test vehicle during vehicle development. It could alternatively be that two individual values may be used, a value drawn from a first graph when defog/defrost has been requested, and a different value drawn from a second graph when cabin heating has been requested (or the larger of the two if both have been requested).

[0042] After the cycle time (e.g. 5 seconds) is finished, the control system 20 determines if the actual temperature T of the coolant has reached the target temperature Ttarget at step 94. The target temperature Ttarget may be selected based on the relationship illustrated in graph 61. If the actual coolant temperature T has reached the target temperature Ttarget, the control system 20 ends the method 80 at step 98 and carries out a driving algorithm, as shown in Figures 6 and 7. If the actual coolant temperature T has not yet reached the target temperature Ttarget, the control system 20 returns to step 86 where it begins anew to determine if a defog/defrost or heating action is needed.

[0043] By selecting a cycle time that is relatively short, such as 5 seconds, the operation of the water pump 14 in sending heat to the heater core 15 approximates that of a continuous flow at a reduced flow rate, from the perspective of the vehicle occupants. It will be understood that a longer cycle time could be selected however, while still suitably approximating a continuous reduced flow from the water pump 14 for the purpose of providing comfort to the vehicle occupants. In some embodiments, an even longer cycle time may be used that does not approximate a continuous reduced flow very well. A shorter cycle time than 5 seconds could alternatively be selected to approximate a continuous flow even more closely than a 5 second cycle time would. In general the benefit to providing a relatively shorter cycle time is that choppiness in the flow of heat into the cabin is reduced. One reason that a short cycle time is possible with the water pump 14 shown in Figure 2 is the use of the wrap spring clutch 38. A wrap spring clutch 38 is capable of being cycled on and off many times over short intervals without substantial heat buildup. This is distinct from other types of clutch, such as friction plate clutches which cannot sustain rapid engagement and disengagement without risk of failure due to heat buildup. Additionally, a wrap spring clutch is capable of many more cycles of engagement and disengagement over its operating life than a friction plate clutch. Furthermore, a wrap spring clutch is able to engage and disengage more quickly than some other types of clutch, which is advantageous in that it permits short cycle times to be used. However, it may still be possible to use a friction plate clutch or another type of clutch instead of the wrap spring clutch 38 in some embodiments of the invention and for some applications. [0044] While the algorithm shown in Figure 4 is shown to divide the cycle into a period of time in which the water pump 14 is on, and a subsequent period of time in which the water pump 14 is off. It is alternatively possible for the two periods of time to be reversed so that, during each cycle the water pump 14 is off first and is then turned on for the latter portion of the cycle.

[0045] During use, depending on the design of the engine 12, the engine 12 could be prone to developing 'hot spots' if there is no coolant flow through an engine. Hot spots are localized regions of the engine 12 that reach significantly higher temperatures than other portions of the engine 12. In an alternative embodiment of the algorithm shown in Figure 4, the water pump 14 may be operated in a way to mitigate the generation of such hot spots in the engine 12, while still permitting a relatively fast warm up of the engine 12 to its target temperature. To illustrate this feature, a portion of the engine 12 is shown in Figure 5a, showing a portion of a coolant conduit 108 passing therethrough. A hot spot is shown at 1 10. When the water pump 14 is stopped, a first volume of coolant shown at 1 12 remains in the conduit 108 proximate the hot spot 1 10 and is heated by the hot spot 1 10 to a temperature that is higher than the coolant that surrounds it, shown at 1 14a on the upstream side and 114b on the downstream side. To achieve mitigation of the hot spot 1 10 (i.e. to reduce the temperature difference between the hot spot 1 10 and other portions of the engine 12), the value of PWM duty that is selected at step 100 may be a very small fixed value (e.g. a fraction of a second), so as to correspond some small amount of rotation, such as, for example, a half of a revolution, one revolution, or a few revolutions of the pump rotor 34. After the pump rotor 34 is turned on and off for the period of time PWM duty, the pump rotor 34 will have turned just enough to cause some mixing of coolant in the conduit 108 with other adjacent coolant in the conduit 108. Thus, the volume of coolant 1 12 that is proximate the hot spot 1 10 mixes with surrounding coolant that is cooler (i.e. one or both of the volumes of coolant 1 14a and 1 14b) to form a volume of coolant 1 15 that has a more uniform temperature. In this way, the heat from the hotter volume of coolant 112 is moved to a spot on the engine 12 where it can heat the engine 12. Very little (substantially none) of the coolant in the conduit 108 in the engine 12 leaves the engine 12 and so very little of the heat generated by the engine is lost. As a result, the reduced warm-up time of the engine 12 is substantially retained, but hot spots 1 10 in the engine are at least to some extent mitigated. This level of control of the flow of coolant through the engine 12 (i.e. whereby the water pump 14 is rotated by a very small amount as described above) is possible using the water pump 14 with the wrap spring clutch 38. By selecting a suitable cycle time and a suitable time PWM duty, the temperature difference between the hot spot 1 10 and other portions of the engine 12 can be reduced without having a large impact on the time required for the engine 12 to warm up to its target temperature (i.e. its optimal temperature). The particular value for PWM_duty that works well may be determined empirically based on tests of a test vehicle during vehicle development and may be stored in a memory for use by the control system 20. Thus, as can be seen, for the purpose of mitigating hot spots in the engine 12 the value for PWM_duty is not based on the ambient temperature Tamb.

[0046] As noted above, the temperature sensed by the temperature sensor 60 is not the same as the temperature of the engine 12 itself. This is particularly true during engine warm up. Because the temperature sensor 60 is positioned outside of the engine 12 (e.g. in the housing of the thermostat), and therefore senses temperature of the coolant outside of the engine, and because there is essentially no coolant flow during engine warm-up, there can be a large difference between the coolant temperature at the sensor 60 and the coolant temperature in the engine 12. Furthermore, this difference varies depending on several factors, such as engine rpm and engine load. As a result, extensive testing of the vehicle 10 is required up front in order to accurately predict engine temperature based on coolant temperature measured by sensor 60. This testing can be time-consuming and expensive.

[0047] Errors in the assumed temperature of the engine 12 lead to errors in the various actions taken by the vehicle's ECU that directly impact fuel economy. For example, in at least some engines, the ECU determines the amount of fuel to inject into the combustion chambers based at least partly on engine temperature. For a lower engine temperature, the ECU is typically programmed to inject a relatively greater amount of fuel into the combustion chambers in order to achieve a selected amount of power to meet a driver's demand. This is because it is expected that the engine's combustion efficiency is relatively lower at lower temperatures and so the injection of greater amount of fuel is intended to compensate for this, albeit at a penalty in emissions and fuel economy. By contrast at a higher engine temperature, the ECU is typically programmed to injected a relatively smaller amount of fuel into the combustion chambers to achieve the same power demand, because it is expected that the combustion efficiency of the engine 12 is relatively higher at higher RPM. During engine warm up where there is essentially no coolant flow out of the engine 12 (in order to reduce engine warm up time), the engine 12 is hotter than the coolant temperature measured at the sensor 60, in some instances by as much as 30 or 40 degrees Celsius or more. If the ECU assumes that the engine temperature is lower than it really is, then it may carry out actions that have a negative impact on emissions and fuel economy, such as to inject more fuel than is necessary into the combustion chambers. If the ECU assumes that the engine temperature is higher than it really is, then it may carry out actions that have a negative impact on the power output of the engine. For example, it may inject too little fuel into the combustion chambers to meet the driver's demand and when the lower-than-expected engine temperature results in a lower-than-expected combustion efficiency, the resulting power output is less than what was requested by the driver. Similarly, the ECU's control of valve timing and other parameters that have an impact on emissions and fuel economy may also be based at least in part on assumed engine temperature and may thus negatively impact emissions and fuel economy when the ECU's assumption of the engine temperature is too far off the actual engine temperature.

[0048] To address this, the water pump 14 may be programmed to periodically send a small volume of coolant to the sensor 60 from within the engine 12. The amount of time during which the water pump 14 is turned on (i.e. the 'on' period) is preferably selected to be large enough to transport coolant from within the engine 12 to the sensor 60 but as small as possible so as to minimize the amount of heat transported out of the engine 12. Viewed from another perspective, the On' period is selected to achieve flow of coolant over a selected distance (i.e. the distance from the engine 12 to the sensor 60). This period will vary based on the engine RPM; at higher RPM the water pump 14 will spin faster and therefore a shorter On' period accomplishes the desired flow, while at a lower RPM the water pump 14 spins slower and thus a longer On' period is needed to accomplish a selected flow. The 'on' period can be selected based on a look-up table in relation to the engine RPM and any other factors that are relevant.

[0049] The frequency of activation of the water pump 14 may be selected based on how quickly the temperature differential builds again between the coolant at the sensor 60 and the coolant in the engine 12 once the water pump 14 is shut off and/or based on other factors. If the temperature differential builds generally slowly, then the temperature measured at the sensor 60 is generally an accurate indicator of the coolant temperature in the engine 12 for longer, and therefore a lower frequency of activation of the water pump 14 is acceptable. By contrast, if the temperature differential builds generally quickly, then the temperature measured at the sensor 60 becomes a less accurate indicator of the coolant temperature in the engine 12 more quickly, and therefore a higher frequency of activation of the water pump 14 is needed.

[0050] In an example embodiment, at relatively higher RPM, the duty cycle of the water pump 14 may be selected to be 5% with a 5 second frequency, and at relatively lower RPM the duty cycle of the water pump 14 may be selected to be 10% at a 5 second frequency.

[0051] It will be understood that the activation of the water pump 14 to regularly transport coolant from within the engine 12 to the temperature sensor 60 results in some small net coolant flow and therefore results in a loss of some heat from the engine 12 during engine warm up. This extends the engine warm up time and has a correspondingly negative influence on fuel economy because the engine 12 remains below its optimum operating temperature for a slightly longer period of time. However, by having more accurate temperature information on the engine by periodically transporting coolant from the engine 12 to the sensor 60, the ECU can better determine the correct settings for various engine-related actions, such as the correct valve timing and the correct amount of fuel to inject into the combustion chambers. This has a greater positive impact on the fuel economy of the vehicle 10 than the negative impact from the small heat loss from the engine 12 during warm up, and so the net result is a gain in fuel economy and a drop in emissions when carrying this out.

[0052] Another advantage to the above described method of sending coolant from the engine to the temperature sensor 60 relates to durability of the engine 12. In embodiments wherein there is a large temperature differential between the coolant at the temperature sensor 60 and the coolant in the engine 12, the ECU is does not have 'true' information on the coolant temperature in the engine 12. It possesses other data, such as coolant temperature information from the sensor 60 outside of the engine 12, and perhaps other data, and uses that data to control engine operation based on assumptions of what the engine temperature is likely to be based on all the data. However, there is at least some potential for situations to occur where the engine 12 is hotter (or at least hotter in certain spots) than the ECU assumes it to be, because the ECU is working with data that is only indirectly related to engine temperature. As a result, there could be situations where the engine 12 gets too hot or too hot in certain spots and could suffer damage or premature wear without the ECU being aware of it. By sending coolant from the engine 12 to the sensor 60 a more direct indication of engine temperature is obtained and so if the engine 12 is too hot, the ECU can sense it through the sensor 60, and can act on it (e.g. to activate the water pump 14 to cool the engine 12 until the temperature drops to an acceptable level). By having a more direct measurement of the engine temperature, the ECU is less likely to be in error as to whether the engine 12 requires cooling or not.

[0053] In addition to the above, it will be noted that significantly less testing of the engine 12 is needed in order to determine the engine temperature based on the temperature sensed by the sensor 60 when it is sensing coolant that came from the engine 12. This reduces some time and cost that would otherwise be needed when developing the engine and the software used by the ECU to control the engine based on the temperature read by the sensor 60. [0054] After the engine 12 reaches its target temperature, (i.e. after the coolant temperature measured by the temperature sensor 60 reaches the target temperature Ttarget), the control system 20 ends the warm-up algorithm, and carries out a driving algorithm, which has as a goal to keep the engine temperature relatively constant at its target temperature independent of the engine load. An exemplary driving algorithm or method is shown at 120 in Figure 6. The driving algorithm 120 starts at step 122. At step 124, the driving algorithm 120 may set an initial value for PWM_duty of 0 (i.e. water pump 14 is off), and the cycle time PWM_period may be set at any suitable value, such as, for example, 5 seconds. At step 126, the driving algorithm 120 determines a current target temperature Ttarget for the coolant that will keep the engine temperature relatively constant at its target temperature, based on the current engine load. As described above in relation to the warm-up algorithm, when the engine 12 is at idle, Ttarget may be a first, higher target temperature, and when the engine 12 is at high load Ttarget may be a second, lower target temperature, to compensate for the greater amount of heat that is being produced by the engine 12 at the high load, as shown by the graph 127. Additionally at step 126, the control system 20 determines the difference between the actual coolant temperature T and the target temperature Ttarget. The control system 20 may then employ any suitable algorithm for achieving the target temperature Ttarget. For example, for each cycle, the control system 20 may use a PID control algorithm to determine an average coolant flow rate for the water pump 14 to provide. A value for PWM duty (which represents the period of time out of the cycle time during which the water pump 14 is on) can then be easily determined based on the selected average coolant flow rate determined using the PID control algorithm. Once the value for PWM duty is selected for the current cycle, the control system 20 starts the water pump 14 at step 128 by deenergizing the electromagnetic coil 40 until the first period of time has elapsed, and then stops the water pump 14 at step 132 by energizing the electromagnetic coil 40. The control system 20 then returns to step 126 to determine anew the target temperature Ttarget based on engine load, and to start a new cycle. [0055] It will be noted that the control system 20 operates the water pump 14 using something akin to pulse width modulation, so as to provide essentially infinitely adjustable control of the effective flow rate of the water pump 14 without the use of valves in the coolant lines. It will be noted that this kind of control, particularly with relatively short cycle times, such as 5 seconds, is well suited to being carried out with a wrap spring clutch which can handle repeated cycling without overheating or damage.

[0056] The P, I and D values to use for the PID control algorithm may be selected during vehicle development by testing a test vehicle. The control system 20 may be programmed to change these values based on different conditions, such as the rapidness of change in the load on the engine 12. For example, if the vehicle 10 changes suddenly from idle to a high load condition, the engine temperature can be expected to rise quickly. Knowing this, the P, I and D values can be selected to rapidly increase the average flow rate of the water pump 14 to compensate and thereby help to prevent a relatively high swing in temperature in the engine 12 that could otherwise occur if the P, I and D values were to remain constant. By contrast, if the engine 12 is gradually increased from idle to a high load condition, the P, I and D values that can be used provide a relatively gentler slope to the increase in the average flow rate of the water pump 14.

[0057] Selecting cycle times that are relatively short, such as 5 seconds has several advantages. For example, when the engine 12 has reached its target temperature, short cycle times mean short periods of cooling and heating the engine 12, which means that the temperature swings between the first and second periods of time are small. Thus, the engine 12 remains relatively close to its target temperature, which keeps the engine 12 at a relatively high combustion efficiency. Furthermore, the small temperature swings reduce the amount of wear that occurs in any engine gaskets such as the head gasket, and in other sealing elements, thereby increasing their operating life as compared to a prior art engine that has larger engine temperature swings. Using a PID control algorithm along with a pulse width modulation with a relatively short cycle time further reduces any overshoot of the target temperature by the control system 20. The driving algorithm 120 may continue to be carried out until the engine 12 is turned off. [0058] As noted above in relation to the warm-up algorithm, it is desirable to provide heating to the vehicle cabin 24 and/or defogging/defrosting of the windshield while driving the vehicle 10. A driving algorithm or method 150 shown in Figure 7 provides this capability. The algorithm 150 starts at step 152, and proceeds to step 154 whereat PWM duty may initially be set to zero and PWM_period may be set to a selected value, such as 5 seconds. The algorithm 150 then determines two potential values for PWM duty and sets the value for PWM_duty to be the larger of the two potential values. Step 156 may be similar to step 126 (Figure 6) in that a target coolant temperature Ttarget is set based on engine load, the current temperature of the coolant T is determined and compared with the target temperature Ttarget, and a first potential value of PWM duty is set based on the difference between the two temperatures, using any suitable algorithm, such as a PID control algorithm. At step 1 8 (which could optionally occur before step 156), the control system 20 determines if a defog/defrost action is needed, based on any one of several conditions, including for example, whether a request for a defog/defrost action having been made by the vehicle occupants using the controls 26 or 28, and including for example, whether the ambient temperature is below a selected ambient temperature as shown in graph 104. If the control system 20 does determine that a defog/defrost action is needed the control system 20 sets a second potential value of PWM duty at step 160. For example, the second potential value of PWM_duty may be set to be 1 second when the cycle time is 5 seconds. If the control system 20 does not sense a defog/defrost action request by the vehicle occupants, the control system 20 may determine the second potential value for PWM duty based on ambient temperature, using a relationship between the second potential value of PWM duty and ambient temperature that is similar to the graph 104 in Figure 4. At step 162, the control system 20 checks if the first potential value is smaller than the second potential value, in which case it uses the second potential value as the value for PWM_duty. Otherwise, it uses the first potential value as the value for PWM duty. In other words, the control system 20 uses whichever is the larger of the two potential values as the value for PWM duty. In this way, the control system 20 has used the ambient temperature and the deemed need for defog/defrost or cabin heat to select a minimum value for PWM duty for that cycle, below which the first period of time cannot go for that cycle. After establishing the value for PWM duty, the control system 20 then proceeds to step 164, whereat it turns on the water pump 14 for the first period of time, and then to step 166 whereat it turns off the water pump 14 for the remainder of the cycle (i.e. for the second period of time). If at step 158, the control system 20 determines that no defog/defrost action is needed, then the control system 20 sets the value to PWM duty to be the first potential value and proceeds to steps 164 and 166. After step 166, the algorithm 150 sends control back to step 156. The driving algorithm 120 may be carried out until the engine 12 is turned off.

[0059] Referring to Figure 1, when the control system 20 ends the warm-up algorithm and initiates execution of the driving algorithm, the engine 12 may be at a relatively high temperature, such as about 100 degrees C, while the coolant in the radiator 16 may be at a relatively low temperature, such as 0 degrees C, depending on the ambient temperature and depending on whether there was any coolant flow that took place in the warm-up phase. Thus, if, for some reason, the water pump 14 was turned on for more than a selected period of time, such as, for example, 4 seconds, it could transport the water from the radiator into the engine 12. In other words, it could replace all of the hot coolant in the engine 12 with cold coolant from the radiator 16. In order to avoid this type of thermal shock to the engine 12 it is possible for the control system 20, when initiating execution of any of the driving algorithms described herein, to initially select a small, but non-zero value for PWM duty to make more gradual the transfer to the engine 12 of cold coolant that was in the radiator 16. After some selected period of time operating in this way, the temperature of the coolant becomes somewhat more uniform (i.e. there becomes less of a difference in the temperature of the coolant in the engine 12 and the coolant elsewhere in the cooling circuit), and so there is less of a concern regarding thermal shock. At that point, the driving algorithm can proceed to a step wherein the target temperature is selected based on engine load, and the PWM duty is selected based on the PID (or other) control algorithm in order to bring the engine 12 towards the target temperature.

[0060] In some embodiments, the fan 18 may be a two-speed fan, instead of being a single speed fan. In addition to providing a driving algorithm for operation of the water pump 14, a driving algorithm for operation of the fan 18 may be provided, as shown at 180 in Figure 8, for use in embodiments of the vehicle 10 wherein the fan 18 is a 2-speed fan. Using the driving algorithm 180, the control system 20 operates the fan 18 using pulse-width modulation and using a second PID control algorithm. The driving algorithm 180 starts at step 182 and then proceeds to step 184 wherein the cycle time for the fan 18 is selected and the value of PWMfan duty (which is the period of time that the fan 18 is on during the cycle time for the fan 18) is set to an initial value, such as 20% of the cycle time for the fan 18. The cycle time for the fan 18 may be the same or different than the cycle time for the water pump 14. At step 186, the control system 20 determines if a situation has occurred where the actual coolant temperature has exceeded the target coolant temperature Ttarget by some selected amount and whether the value of PWM_duty (for the water pump 14) corresponds to 100% of the cycle time (for the water pump 14) for more than a selected amount of time. If not, the control system 20 sets the value of PWMfan duty to zero at step 187 and returns to step 186. If so, then the control system 20 proceeds to step 188 where it determines the difference between the actual coolant temperature T and the target coolant temperature Ttarget and determines a value for PWMfan duty using a suitable control algorithm, such as a second PID control algorithm for the fan 18, as distinct from the first PID control algorithm which is described above for the water pump 14. At step 190, the control system 20 determines if the value selected for PWMfan duty is 100% of the cycle time for the fan 18. If so, then the fan 18 is operated at its high speed at step 192 for one cycle, and then the control system 20 returns to step 184. If the value of PWM duty is less than 100% of the cycle time, then the fan 18 is operated at its low speed at step 194 until the first period of time for the fan is completed. At step 196 the fan 18 is turned off for the remainder of the cycle. Control is then returned to step 184. By controlling the fan operation in this way, the fan 18 is used only when needed, and is used in its high speed setting only when needed. The fan 18 in some embodiments is a relatively large consumer of power in the vehicle 10 and so it is advantageous to use the water pump 14 where possible so as to reduce the use of the fan 18. Furthermore, controlling the operation of the fan 18 in this way reduces temperature swing in the coolant, since operation of the fan 18 has a relatively strong impact on coolant temperature.

[0061] In some embodiments, instead of having a two speed fan, two single speed fans may be provided. In such embodiments, the above control algorithm for the fan would be the same, except that instead of operating one fan at low speed at step 194 and at high speed at step 192, a first fan would be first operated in step 194, and a second fan would be operated at step 192 instead of, or in conjunction with the first fan.

[0062] Furthermore, in some other embodiments, a single fan is provided that is infinitely variable in speed over a certain range of speeds. In such an instance, PID control may still be used with such a fan, except that it needn't be in the form of pulse- width modulation. Instead, the fan speed can simply be selected using a PID control algorithm based on the difference between the actual and target coolant temperatures. The fan would preferably only be turned on, however, when the water pump 14 was unable to keep the coolant temperature from exceeding the target temperature for more than a selected period of time.

[0063] Aside from providing controls 26 and 28 for defog and defrost, it is possible to provide an additional control button in the vehicle cabin 24, that would permit the vehicle occupants to choose between an Eco mode and a Comfort mode. Selecting Comfort mode could be used to override the control system's ability to shut off the water pump 14 entirely. In other words, it prevents the control system 20 setting the value of PWM duty to zero; in its place it may set the value of PWM duty to some small number, such as 10% of the maximum possible flow rate which would be 0.5 seconds on a 5 second cycle. The particular value for PWM duty that is selected may be selected to ensure that the vehicle occupants are kept comfortable. Testing can be carried out during vehicle development to determine a value for PWM duty that provides cabin heating performance that is generally close to the performance achieved if the water pump 14 were on constantly. In some embodiments, in Comfort mode, the water pump 14 may optionally be set to be on constantly (i.e. PWM duty value of 100% of cycle) until the Eco mode is selected. Selecting Eco mode could be used to permit the control system 20 to set the value of PWM duty to zero when the control system deems it beneficial.

[0064] The graphs shown in Figures 9a, 9b, 9c and 9d show the temperatures of the coolant, the cylinder head and at the dashboard vents, as well as the value of PWM_duty (expressed as a percentage of the maximum possible flow rate for the water pump 14) in relation to time for a test vehicle. In each figure, the solid line is the cylinder head temperature, the dashed line is the coolant temperature, the dot-dash line is the dashboard vent temperature and the dotted line is the value of PWM duty. Figure 9a shows this data in a test where the control system 20 was permitted to set the value of PWM duty to zero if needed. Figure 9b shows this data in a test where the control system 20 was not permitted to set the value of PWM duty to less than 5% of the maximum possible flow rate for the water pump 14. Figure 9c shows this data in a test where the control system 20 was not permitted to set the value of PWM duty to less than 20% of the maximum possible flow rate for the water pump 14. Figure 9d shows this data for a standard water pump that is always on (effectively a value of PWM_duty of 100%). It will be noted that the time required for the engine 12 to reach an optimal temperature (e.g. about 120 degrees C) increased as the minimum value of PWM duty increased. In fact, after 2000 seconds of testing, the engine temperature in Figure 9d never reached 120 degrees C.

[0065] Reference is made to Figure 10, which shows a graph of temperature vs. time for several different tests on a test vehicle. The upper and lower solid lines in Figure 10 are the cylinder head temperature and dashboard vent temperature using the water pump 14 where the control system 20 is permitted to set a value for PWM_duty of zero. The upper and lower dotted lines are the cylinder head temperature and dashboard vent temperature using the water pump 14 where the control system 20 is not permitted to set a value for PWM_duty that is less than 20% of the maximum possible flow rate for the pump. The upper and lower dashed lines are the cylinder head temperature and dashboard vent temperature using a conventional water pump that is always on. It is noteworthy that the algorithm where the minimum value for PWM duty is 20% provides a dashboard vent temperature profile that is substantially the same as that provided by a conventional water pump, while providing a temperature profile for the cylinder head that is close to the temperature profile provided when the control system 20 could set the value of PWM duty to zero. This means that the engine heats up to take advantage of the higher combustion efficiency relatively quickly, while the vehicle occupants do not suffer in terms of their comfort or their ability to defog/defrost the windshield as compared to using a conventional arrangement with a water pump that is always on.

[0066] In order to reduce the amount of starts and stops of the water pump 14 that are carried out, the control system 20 may set the value of PWM_duty to zero in instances where the determined value is deemed to be small (e.g. less than 5% of the maximum possible flow rate). Additionally or alternatively, the control system 20 may set the value of PWM_duty to be the full cycle in instances where the determined value is deemed to be large (e.g. greater than 80% of the maximum possible flow rate). As a result, at least a starting or a stopping of the water pump is avoided in these cycles.

[0067] The strategies disclosed herein for controlling the operation of the water pump 14 reduce the overall amount of time that the water pump 14 is on, which reduces the overall power consumption associated with the water pump 14, which in turn improves the fuel economy of the vehicle 10.

[0068] In the embodiment shown in Figure 1 , the thermostat 21 is provided and may act independently of the control system 20, depending on the type of thermostat it is. However, the thermostat 21 does not hamper the control system 20 from controlling the engine temperature using the water pump 14 since the control system 20 provides closed loop control of the coolant temperature based on the difference between the actual coolant temperature sensed by temperature sensor 60 and the target coolant temperature. It would, however, be advantageous to provide a system that omitted the thermostat 21. [0069] Reference is made to Figure 1 1 , which shows an alternative cooling system layout, wherein the two coolant loops shown in Figure 1 are replaced with a single coolant loop. The coolant flows sequentially from the water pump 14 through the engine 12, through the cabin heater core 15, through the radiator 16 and finally back to the inlet of the water pump 14. Such a configuration is simpler than the cooling system configuration used in many vehicles today, which incorporate two loops. As a result, the cooling system shown in Figure 1 1 would be more robust and less expensive than the one shown in Figure 1 , due to having fewer components, and fewer joints between components. Additionally, the cooling system shown in Figure 11 does not include a thermostat. Although the P, I and D values may differ from those that would be used in the system shown in Figure 1 , the control of the cooling system shown in Figure 1 1 may still be carried out using the same algorithms shown in Figures 3, 4, 6, 7 and 8.

[0070] It will be noted that the system described herein can easily be retrofitted to many existing vehicles or can easily be incorporated into many existing vehicle designs. The vehicle's current water pump may be replaced with the water pump 14 if necessary, the temperature sensor 60 is incorporated into the coolant conduit at the engine, a suitable control unit can be provided, which together with the existing ECU and/or VCU, can make up the control system 20.

[0071] In the embodiments described above, the control system 20 uses the coolant temperature to estimate the temperature of the engine 12 based on empirical testing during vehicle development. However, in some embodiments, a temperature sensor may be provided in the engine itself that provides direct measurement of the temperature of the metal making up the engine, instead of, or in addition to a temperature sensor for measuring the coolant temperature. In such embodiments, the temperature signal from this sensor may be used to represent the actual temperature and a target temperature will be set for it, which will control the amount of time the water pump 14 will be on for during a cycle. The relationship between the temperature reading from this sensor and the temperature at the hottest portion of the engine may be more direct and more clear than the relationship between coolant temperature and the temperature at the hottest portion of the engine. As a result, if this temperature sensor were used instead of a temperature sensor that measures coolant temperature, more precise control over the engine temperature may be achieved.

[0072] Reference is made to Figure 12, which shows a graph of several superimposed curves. Curve 200 is the temperature of an air flow into the vehicle cabin 24 using a water pump that begins operation essentially immediately upon turning on the engine. The coolant that is pumped by the water pump passes through a heater core to heat the aforementioned air flow that then passes into the cabin 24. The air flow may, for example, be requested for the purpose of defrosting the vehicle's windshield. For the curve 200 (and for all other curves that represent temperature in the graph), the Y axis of the graph represents temperature (in degrees Celsius) and the X axis represents time (in seconds). As can be seen, the temperature of the air flow increases immediately and continues to increase progressively over time. Curve 202 represents the duty cycle of the water pump 14 using the control system 20 and one of the methods described above, in accordance with an embodiment of the present invention. For the curve 202, the Y axis of the graph represents the duty cycle for the water pump 14 (in percent, where a 100% duty cycle represents the water pump being on continuously) and the X axis represents time (in seconds). As can be seen, for some initial period of time, i.e. from time TO (engine startup) to time Tl , the water pump 14 is off (i.e. it has a duty cycle of zero). At time Tl, the water pump 14 is turned on and is operated at a duty cycle of about 50% (this duty cycle value is an example value only and is not to be taken as limiting). The water pump 14 is operated at this duty cycle throughout the rest of the time represented on the graph. Curve 204 represents the temperature of the coolant in the engine when the water pump is operated as shown by curve 202. As can be seen the temperature of the coolant in the engine increases relatively quickly when the water pump is off. At time Tl, when the water pump 14 begins to pump coolant out of the engine and through the heater core, the temperature of the coolant can be seen to decrease as it releases built up heat to the air flow and then subsequently increase gradually as the air flow itself presumably warms up and is drawn from the cabin 24 and is recirculated back through the heater core. Curve 206 represents the temperature of the air flow entering the cabin 24 when the water pump 14 is operated as shown by curve 202. As can be seen, the temperature of the air flow initially remains relatively constant since there is no heat input being received by the air flow from the coolant. Once the water pump 14 is turned on at time Tl however, built up heat in the coolant is released to the air flow via the heater core, thereby driving up the temperature of the air flow. As can be seen, at time T2 and thereafter the temperature of the air flow increases to a value that exceeds the temperature that would be achieved by the air flow when operating a water pump immediately upon turning on the engine. When defrosting the windshield of a vehicle, it is necessary for the temperature of the air flow being blown on the windshield to be greater than some threshold temperature in order to have any melting effect on the frost present on the windshield. In a situation where the ambient temperature is low, e.g. -20 degrees Celsius, it is possible that the threshold temperature will be reached by the air flow several minutes earlier when operating the water pump 14 as shown by curve 202 than if the water pump were operated immediately upon starting the engine. An example would be where the threshold temperature would be temperature TEMPI as shown in the graph. It can be seen that the air flow reaches temperature TEMPI about 400 seconds after engine startup (as shown by curve 206) when operating the water pump 4 as shown by curve 202, whereas the air flow does not reach temperature TEMPI until about 580 seconds after engine startup (as shown by curve 200) when operating a water pump immediately upon engine startup. Thus, by the time the air flow shown by curve 200 reaches the threshold temperature at which it becomes effective in melting frost on the windshield, the air flow shown by curve 206 has already been melting frost on the windshield for about 3 minutes.

[0073] The time Tl may be selected based on any suitable criteria. For example the time Tl may be selected so as to permit the air flow to reach the threshold temperature TEMPI in less than a selected amount of time (e.g. less than 420 seconds, or 7 minutes after engine startup). The time Tl may vary depending on the ambient temperature at the time of engine startup. For example, when the ambient temperature is higher the time Tl may be sooner, since it will take less time for the coolant in the engine to achieve a selected temperature that would drive the air flow to reach the threshold temperature TEMPI . When the ambient temperature is lower the time Tl may be later since it will take more time for the coolant in the engine to achieve a selected temperature that would drive the air flow to reach the threshold temperature TEMPI . The time Tl may be selected by the control system based on a lookup table using the ambient temperature at the time of engine startup.

[0074] The curve 208 is simply a curve representing the difference between the curves 200 and 206.

[0075] While the above description constitutes a plurality of embodiments of the present invention, it will be appreciated that the present invention is susceptible to further modification and change without departing from the fair meaning of the accompanying claims.

Claims

CLAIMS:

1. A method of controlling a water pump for a vehicle having an internal combustion engine, wherein the water pump has a maximum possible flow rate of coolant associated therewith, the method comprising:

a) sensing whether the engine has been started;

b) selecting an average flow rate of the coolant for the water pump wherein the selected average flow rate is in at least some situations non-zero and lower than the maximum possible flow rate; and

c) controlling the operation of the water pump to provide the selected average flow rate of the coolant by alternately starting and stopping the water pump until the temperature of the engine is determined to be at least a selected target engine temperature.

2. A method as claimed in claim 1 , wherein the selected average flow rate is selected based at least in part on the ambient temperature.

3. A method as claimed in claim 1 , wherein step c) includes at least one cycle of starting the water pump for a first selected period of time and subsequently stopping the water pump for a second selected period of time, wherein the first period of time is selected to so as to mix coolant adjacent a first relatively hotter spot in the engine with coolant adjacent a second relatively cooler spot in the engine while generating substantially zero coolant flow out of the engine.

4. A method as claimed in claim 1 , wherein the selected average flow rate is repeatedly selected anew after a selected time interval.

5. A method as claimed in claim 1, wherein if the ambient temperature is greater than a selected ambient temperature, the selected average flow rate is zero.

6. A method as claimed in claim 1 , wherein the determination of whether the temperature of the engine is at least at the target engine temperature is determined by determining whether the temperature of the coolant is at least a selected target coolant temperature.

7. A method as claimed in claim 6, wherein the selected target coolant temperature is selected based at least in part on a determination of the amount of load on the engine.

8. A method as claimed in claim 1, wherein the water pump includes a housing, a pump rotor that is rotatable in the housing, and an input member that is driven by the engine and that is selectively operatively engageable to the pump rotor through a wrap spring clutch.

9. A method as claimed in claim 8, wherein step c) includes repeating cycles of alternately operatively engaging and disengaging the input member with respect to the pump rotor through the wrap spring clutch.

10. A method as claimed in claim 9, wherein movement of the wrap spring clutch to disengage the input member with respect to the pump rotor is carried out by energizing an electromagnetic coil, and movement of the wrap spring clutch to engage the input member with respect to the pump rotor is carried out by deenergizing the electromagnetic coil.

1 1. A method as claimed in claim 9, wherein each cycle lasts approximately 5 seconds.

12. A method as claimed in claim 9, wherein the selected average flow rate is selected based at least in part on a determination of whether a vehicle occupant has requested at least one action selected from the group of actions consisting of: a cabin heating request and a window defog/defrost request.

13. A method of control of a water pump for pumping coolant through an internal combustion engine for a vehicle, comprising:

a) determining a selected target coolant temperature;

b) determining the actual coolant temperature;

c) selecting an average flow rate for the water pump that is in at least some situations non-zero and lower than the maximum possible flow rate; and

d) controlling the operation of the water pump to provide the selected average flow rate by alternately starting and stopping the water pump to bring the actual coolant temperature towards the target coolant temperature.

14. A method as claimed in claim 13, wherein the target coolant temperature is selected based at least in part on a determination of the amount of load on the engine.

15. A method as claimed in claim 13, wherein the water pump includes a housing, a pump rotor that is rotatable in the housing, and an input member that is driven by the engine and that is selectively operatively engageable to the pump rotor through a wrap spring clutch.

16. A method as claimed in claim 15, wherein step d) includes a plurality of cycles of alternately operatively engaging and disengaging the input member with respect to the pump rotor through the wrap spring clutch.

17. A method as claimed in claim 16, wherein movement of the wrap spring clutch to disengage the input member with respect to the pump rotor is carried out by energizing an electromagnetic coil, and movement of the wrap spring clutch to engage the input member with respect to the pump rotor is carried out by deenergizing the electromagnetic coil.

18. A method as claimed in claim 13, wherein the target coolant temperature is repeatedly selected anew after a selected time interval.

19. A method as claimed in claim 18, wherein the selected average flow rate is selected based at least in part on a PID control algorithm.

20. A method as claimed in claim 19, wherein step c) includes a plurality of cycles of alternately starting the water pump for a first selected period of time and stopping the water pump for a second selected period of time, wherein the first and second selected periods of time are selected so as to provide the selected average flow rate.

21. A method as claimed in claim 13, wherein the selected average flow rate is selected based at least in part on a determination of whether a vehicle occupant has requested at least one action selected from the group of actions consisting of: a cabin heating request and a window defog/defrost request.

22. A method as claimed in claim 13, wherein the selected average flow rate is selected based at least in part on the ambient temperature.

23. A method as claimed in claim 13, wherein the selected average flow rate is greater than zero depending on the ambient temperature.

24. A method as claimed in claim 13, wherein the vehicle includes a radiator positioned to receive coolant flow from the engine and a fan positioned to cool coolant flowing through the radiator, and wherein the fan has at least a first, lower speed and a second, higher speed, wherein the fan is operated at at least the lower speed if the actual coolant temperature is greater than the target coolant temperature and the water pump has been on for at least a selected amount of time.

25. A method as claimed in claim 24, further comprising selecting an average on-time for the fan, and alternately starting and stopping the fan at the lower speed to provide the selected average on-time if the actual coolant temperature is greater than the target coolant temperature and the water pump has been on for at least a selected amount of time.

26. A method as claimed in claim 25, wherein the fan is operated at the higher speed for a selected amount of time upon detection that the selected average on-time for the fan corresponds to continuous operation of the fan at the lower speed for at least a selected period of time.

27. A method as claimed in claim 25, wherein the selected average on-time is selected based at least in part on a second PID control algorithm.

28. A system for pumping coolant through an internal combustion engine for a vehicle, comprising:

a water pump;

a control system, wherein the control system is programmed to:

a) determine a selected target coolant temperature;

b) determine the actual coolant temperature;

c) select an average flow rate for the water pump that is in at least some situations non-zero and lower than the maximum possible flow rate; and d) control the operation of the water pump to provide the selected average flow rate by alternately starting and stopping the water pump to bring the actual coolant temperature towards the target coolant temperature.

29. A system as claimed in claim 28, wherein the water pump includes a housing, a pump rotor that is rotatable in the housing, and an input member that is driven by the engine and that is selectively operatively engageable to the pump rotor through a wrap spring clutch.

30. A system as claimed in claim 29, wherein movement of the wrap spring clutch to disengage the input member with respect to the pump rotor is carried out by energizing an electromagnetic coil, and movement of the wrap spring clutch to engage the input member with respect to the pump rotor is carried out by deenergizing the electromagnetic coil.

31. A method of controlling a water pump for a vehicle having an internal combustion engine and a temperature sensor positioned for detecting the temperature of coolant, wherein the water pump has a maximum possible flow rate of coolant associated therewith, the method comprising:

a) sensing whether the engine has been started;

d) turning off the water pump for another selected period of time.

32. A method as claimed in claim 31 , wherein the selected period of time in step b) is selected so that the water pump, when activated, sends coolant from the engine a sufficient distance to just reach the temperature sensor.

33. A method of defrosting a windshield of a vehicle after engine startup, comprising: a) delaying circulation of coolant from an engine through a heater core until a selected time after engine startup; and

34. A method as claimed in claim 33, wherein step b) includes:

selecting a non-zero duty cycle for a water pump that is connected to drive circulation of the coolant; and

operating the water pump at the selected non-zero duty cycle at the selected time.