COOLANT PUMP FOR INTERNAL COMBUSTION ENGINE

RELATED APPLICATION

This application derives and claims priority from U.S. patent application 11 /194,382, filed 1 August 2005.

TECHNICAL FIELD

This invention relates in general to pumps, and more particularly to a coolant pump for an internal combustion engine, to an engine equipped with such a pump, and to a method of dissipating heat from such an engine.

BACKGROUND ART

Many internal combustion engines rely on liquid coolants to dissipate heat that would otherwise destroy such engines. In the typical engine coolant passageways surround the cylinders of the engine and a water pump, driven by the engine itself, circulates the coolant through the passageways. In most engines, particularly those used to power automotive vehicles, the water pump also circulates the coolant through a radiator where the heat is transferred to air passing through the radiator. The water pump for this type of engine may also circulate the coolant through an additional heat exchanger in the form of a heater that supplies heat to the passenger compartment. Usually, a thermostat restricts the flow of coolant to the radiator to maintain the temperature of the coolant in the coolant passageways generally uniform, once that coolant reaches a prescribed operating temperature.

The water pump, being coupled directly to the crankshaft of the engine, operates at a speed that correlates at a fixed ratio to the speed of the crankshaft. If the speed of the crankshaft increases, so does the speed of the water pump. But that often does not produce optimal cooling for the engine or best supply coolant to either the radiator or the

heater. For example, when an automobile engine operates at highway speeds for extended time and then is brought to idle at a stop, or to lower speeds in city driving, the flow of coolant may not be sufficient enough to dissipate the residual heat remaining from the high-speed operation. The engine should receive a greater flow of coolant. Also, at start up the engine may not circulate enough coolant through the heater.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view of an internal combustion engine equipped with a coolant pump constructed in accordance with and embodying the present invention;

Fig. 2 is a sectional view of the pump; and Fig. 3 is a perspective view, partially broken away and in section, of the pump.

BEST MODE OF CARRYING OUT THE INVENTION

Referring now to the drawings, an internal combustion engine 2 includes (Fig. 1) a block 4 that contains cylinders 6 in which pistons 8 reciprocate, and the pistons 8 rotate a crankshaft 10 from which power is delivered from the engine 2. Fuel burns in the cylinders 6 beneath a head 12 to produce that power, but the combustion also produces excess heat, which must be dissipated to protect the engine 2 from destruction. To this end, the block 4 and the head 10, contain coolant passageways 14 through which a liquid coolant, such as a mixture of water and ethylene glycol, flows.

Indeed, the engine 2 itself powers a coolant pump 16 which circulates the coolant through the passageways 14 to extract the excess heat produced in the cylinders 6. The power to operate the coolant pump 16 derives from the crankshaft 6, which is equipped with a pulley 18 over which a belt 20 is trained. The belt 20 delivers power to the coolant pump 16 and other accessories as well.

Actually, the coolant pump 16 and coolant passageways 14 lie in a coolant circuit that beyond the engine 2 also includes at least a primary heat exchanger that typically takes the form of a radiator 22 through which air flows to extract heat from the coolant in passing through the radiator 22. The circuit also includes a secondary heat exchanger in the form of a heater 24 designed to heat the passenger compartment of an automotive vehicle. The inlet to the heater 24 communicates with one of the coolant passageways 14 downstream from the cylinders 6, so that coolant flows into the heater 24 at an elevated temperature. Here the heater 24 is provided with a valve 26 to control the rate of the flow of coolant through it. The heater 24 discharges the coolant back into a coolant passageway 14 at the location where that passageway 14 discharges the coolant to the radiator 22. Here the passageway 14 contains a thermostat 28, which has the capacity to restrict the flow of coolant, so that the temperature of the coolant within the passageways 14 and the heater 24 remains generally uniform once the engine 2 reaches its operating temperature.

The coolant pump 16 includes (Figs. 2 & 3) a housing 30, an impeller 32 that rotates within the housing 30 about an axis X, a pulley 34 over which the belt 20 is trained, and a clutch 36 interposed between the impeller 32 and the pulley 34. The clutch 36 controls the angular velocity at which the impeller 32 rotates, so that the impeller 32 to a measure operates independently of the crankshaft 10. At least the ratio between the velocity of the impeller 32 and the velocity of the crankshaft 10 is variable. Preferably, the clutch 36 is a magnetic particle clutch.

The housing 30 provides a cavity 40 that opens into a coolant passageway 14 at one end of the engine block 4 and as a consequence the cavity 40 forms part of the coolant circuit. Here the end of the housing 30 is open and provided with a flange 42 along which it is secured to the block 4. The other end of the housing 70 is for the most part closed by an end wall 44 provided with an axially directed bearing mount 46 through which a portion of the impeller 32 projects. The axially

directed mount 46 contains sealed antifriction bearings 48. The housing 30 also includes an inlet 50 that opens into the cavity 40 near the end wall 44.

The impeller 32 includes a shaft 52 that rotates in the bearings 48 of the housing 30 about an the axis X and extends both into the cavity

40 and in the other direction away from the cavity 40. Within the cavity

40 the impeller 32 is fitted with vanes 54 that radiate from the axis X.

When the impeller 32 rotates on the bearings 48, its vanes 54 draw coolant from the inlet 50 and force it into the coolant passageways 14 of the block 4 and head 12. That coolant after being heated also flows into the heater 24 unless restricted by the valve 26.

The magnetic particle clutch 36 includes an inner clutch element

60 and an outer clutch element 62 which are organized concentrically about the axis X. In addition it has an electromagnet 64 that is carried by the outer clutch element 62 and a connector assembly 66 for connecting the electromagnet 64 to a source of electrical energy.

The inner clutch element 60 is coupled to and rotates with the shaft 52 of the impeller 32. To this end, it has a sleeve 70 that fits over the impeller shaft 52, to which it is coupled with a spline or key so that the two will always rotate at the same angular velocity. The inner element 60 also has a rim 72 provided with a cylindrical surface that is presented outwardly away from the axis X. The sleeve 70 and the rim 72 are joined together by a web 76 that is considerably narrower than both. The outer clutch element 62 encloses the inner clutch element 60, yet is capable of rotating relative to the inner clutch element 60. To this end, it has two sections 80 which fit along each side of the web 76 for the inner element 60, and they provide a hub 82 which encircles the sleeve 70 of the inner element 60. Between the hub 62 and sleeve 70 are antifriction bearings 84 that enable the outer element 62 to rotate relative to the inner element 60, with the axis X being the axis of rotation. The two bearings 84 are isolated from exterior contaminants by seals

that likewise fit between the sleeve 70 and hub 82. The sections 80 of the outer element 62 also extend over the rim 72 of the inner element 60 where they provide a cylindrical surface that is presented inwardly toward the axis X and toward the cylindrical surface on the rim 72 of the inner element 60. Between the two cylindrical surfaces is a gap g of uniform thickness. It contains magnetic particles, that is to say, particles that are capable of being magnetized in the magnetic field and when magnetized are capable of transferring torque from the outer clutch element 62 to the inner clutch element 60. That field is produced by the electromagnet 64, which is captured in the outer element 62 slightly outwardly from the cylindrical interior surface. Thus, the magnetic particles constitute a torque-transfer substance.

The connector assembly 66 lies between the housing 30 and the two elements 60 and 62 of the clutch 35. It includes a stationary connector 90 which is attached to the end wall 44 of the housing 30 and is formed from a dielectric substance. The connector 90 carries an inner and outer slip rings 92, which are formed from an electrically conductive material. In addition, the connector assembly 66 includes a rotating connector 94 which is likewise formed from a dielectric substance. It carries inner and outer brushes 96 which are formed from an electrically conductive material and are biased by springs against the inner and outer slip rings 92, respectively, on the stationary connector 90. Outwardly, from the slip rings 92 and brushes 96, the two connectors 92 and 94 create a labyrinth that excludes contaminants from the slip rings 92 and brushes 94.

The electromagnet 64 is in effect an annular coil having two leads, one attached to the inner brush 96 and the other to the outer brush 96. The slip rings 92 of the stationary connector 90 are connected across a source of electrical energy, such as the storage battery of an automotive vehicle, there being a control module interposed between the slip rings 92 and the energy source to control the electrical potential impressed across the electromagnet 64 and hence the current that flows through the magnet

64. The control monitors and responds to several operating conditions of the engine 2, including the temperature of the coolant in the coolant passageways 14 of the engine block 4, and also the speed of impeller 32 through a speed sensor which may be mounted on the housing 30. The magnetic particles in the gap g between the of two clutch elements 60 and 62 transfer torque from the outer section 62 to the inner section 60, but only when the electromagnet 64 is energized. Moreover, when the electromagnet 64 is energized and the transfer of torque occurs, the velocity of the inner section 60 relative to the outer section 62 depends on the magnitude of the current passing through the magnet 64 which in turn depends on the magnitude of the electrical potential impressed across it. In any event, the electromagnet 64 creates a magnetic field in the gap g, and the strength of that field determines the relative speed between the inner and outer clutch elements 60 and 62. 5 The pulley 34 of the coolant pump 16 serves as a drive member for the pump 16. It encircles the outer element 62 of the magnetic . particle clutch 36 and is coupled to the outer section 62 through machine screws 98, so that the pulley 36 and outer section 62 rotate together always at the same angular velocity. The belt 20 passes over the pulley 0 18 on the crankshaft 10 and the pulley 34 of the clutch 36 so that the crankshaft 10 drives the outer element 62 of the clutch 36 such that a fixed ratio exists between the velocities of the two.

In the operation of the engine 2, fuel and air enter the cylinders 6 where the mixture is ignited, driving the pistons 8 toward the crankshaft 5 10 and imparting rotation to the crankshaft 10. The combustion produces heat which elevates the temperature of the engine block 4 and the coolant in its passageways14. But the pump 16 circulates that coolant through the passageways 14 and through the radiator 22 and perhaps the heater 24 where the heat is extracted from the coolant to o reduce its temperature. The lower temperature coolant flows back to the pump 16 which recirculates it through the passageways 14. The thermostat 26 controls the flow of the coolant through the passageways

14 in the sense that it seeks a position which keeps the coolant within the passageways 14 at a prescribed temperature. But it is not entirely effective in this regard. The pump 16 provides an extra measure of control, so that the pump 16 and thermostat 28 together provide enhanced thermal management for the engine 2 and thereby improve the efficiency of the engine 2.

To this end, the ratio between the crankshaft pulley 18 and the pump pulley 36 are such that the pump pulley 36 will rotate at a higher velocity than the pulleys on conventional pumps for internal combustion engines. The increased velocity, however, is modulated by the magnetic particle clutch 36 so that the impeller 32 of the pump 16 may not — and indeed often does not - operate at the velocity of the pulley 34. Nevertheless, a reserve for increased velocity of the impeller 32 is available. Some operating conditions may require that the reserve be called upon. For example, if the engine 2 runs at high power output for extended periods on a hot day, the control module for the pump 16 will sense an elevation in the temperature of the coolant in the passageways 14 and will direct enough current through the electromagnet 64 of the clutch 36 to rotate the impeller 32 at a velocity great enough to circulate the coolant at a rate that prevents the engine 2 from overheating. This capability is particularly useful if the engine 2 is brought to idle after an extended period of operation at high power output. Likewise, at low engine speed when the engine is cold, the reserve velocity can circulate the coolant, even as it heats, through the heater 24 to bring warmer coolant to the heater 24 and thereby hasten the time required to heat the passenger compartment.

Variations are possible. For example the drive element represented by the pulley 34 of the pump 16 may be part of a gear train or a sprocket for a chain drive. The housing 30 of the pump 16 may be cast in part into the block 4 of the engine 2. The electromagnet 64 of the clutch 36 may be carried by the inner clutch element 60 or it may be located externally of both clutch elements 60 and 62, yet close enough

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to enable the magnetic field produced by it to pass through the gap g between the clutch elements 60 and 62. The clutch 36 may be installed on the crankshaft 10 instead of on the shaft 52 at the impeller 32, in which event the shaft 52 would have a pulley attached to it, with that 5 pulley and another pulley at the clutch 36 being connected by an endless belt trained over them. However, the belt may be dedicated to the pump 16 so as not to drive other components. A magnetorheological clutch may be substituted for the magnetic particle clutch 36. This type of clutch utilizes a magnetorheological fluid as its o torque-transfer substance. To this end, the viscosity of the fluid may be altered with a magnetic filed - the stronger the field greater the viscosity. The clutch includes an electromagnet for producing the magnetic fluid that controls the viscosity of the fluid in the clutch. Also, in the event the engine 2 is used for marine applications, a body of water may serve as 5 the primary heat exchanger and the water itself as the coolant.