GB2037913A

GB2037913A - Water Pump Drive for Internal Combustion Engines

Info

Publication number: GB2037913A
Application number: GB7940565A
Authority: GB
Original assignee: Delta Materials Research Ltd
Current assignee: Delta Materials Research Ltd
Priority date: 1978-11-29
Filing date: 1979-11-23
Publication date: 1980-07-16

Abstract

A water-cooled internal combustion engine has a first pulley 5 rotatable with the water pump and a second pulley 3 rotatable with the crankshaft, and a vee belt 33 passing around the pulleys. Each pulley has two members 11, 17 and 21, 23 each providing one inclined face of the vee groove of the pulley, one member 11, 21 is fixed and the other 17, 23 is movable under spring bias relative to the other. The position of the movable member of one of the pulleys is determined by a spring 27 constituted by a shape memory effect (SME) element defined as an element of a material whose elastic modulus varies significantly with temperature in a reversible manner over a transition temperature range. The pulleys are arranged so that, below the transition temperature of the element, the first pulley rotates more slowly than it does above the transition temperature for the same crankshaft speed. <IMAGE>

Description

SPECIFICATION Improvements in Water-cooled Internal Combustion Engines This invention relates to water-cooled internal combustion engines. It is usual in such engines for a water pump for circulating the cooling water to be rotated by means of a belt passing around a pulley mounted on the shaft of the rotary water pump and around a pulley mounted on the crankshaft of the engine. A fan may be mounted on the same shaft as the water pump for drawing air through a radiator forming part of the cooling system of the engine. If the pulleys mounted on the shaft of the water pump and on the crankshaft have fixed effective diameters, then the speed of rotation of the water pump and the fan, when fitted, bear a fixed relationship with that of the crankshaft.It is desirable however for the speed of operation of the water pump and the rotation of the fan to be slowed down relative to the speed of rotation of the crankshaft when the engine is cold and for them to be speeded up relative to that of the crankshaft when the engine is hot.

It is an object of the present invention to provide a water cooled internal combustion engine with such a system whereby the abovementioned desirable feature can be obtained.

According to the present invention a watercooled internal combustion engine has first and second vee pulleys rotatable with the drive shaft of a water pump and with the crankshaft of the engine respectively, a vee belt passing around part of the periphery of each of said pulleys and wherein each of the pulleys has two members each providing one inclined face of the vee groove of the pulley, one of the members being fixed to the shaft and the other slidable along the shaft to vary the separation of the inclined faces, and the position of the movable member of one of the pulleys relative to the other member of the pulley being determined by an SME element (as herein defined), and the first and second pulleys being arranged such that, at temperatures below the transition range of temperatures of the SME element, the ratio of the effective diameter of the first pulley to that of the second pulley is greater than said ratio at temperatures equal to or greater than said transition range of temperatures of the element.

By a "shape memory effect element" (SME) as used herein is meant an element of a material, usually an alloy, having an elastic modulus which varies significantly with temperature in a reversible manner over a transition temperature range dependent on the material employed. There are a number of known alloys which display shape memory effect when subject to a pre-conditioning heat treatment. A suitable alloy is one having a composition by weight of the order of copper 70%, aluminium 4% and zinc 26%. Above and below the transition temperature range, change of temperature has no appreciable effect on the thermal properties of the material. In the transition range, however, increase in temperature results in progressive increase in the elastic modulus, and hence in decrease in the strain of the stress element.

In the arrangement of the present invention, at temperatures below the temperature range of the SME element, the vee belt is located towards the bottom of the vee groove of the second vee pulley and towards the top of the vee groove of the first pulley and, in this way, the ratio of the effective diameter of the first pulley to that of the second pulley is such that the water pump and the fan rotate at a relatively low speed compared with the speed of rotation of the crankshaft. This is a satisfactory situation in that, before the engine has warmed up to its most efficient operating temperature, the water pump and the fan are rotated relatively slowly, thereby having a reduced effect on the cooling system.The SME element is chosen such that the transition range of temperature is close to the most efficient operating temperature of the engine so that, when the engine has warmed up, the pulley fitted with the SME element causes the effective diameter of that pulley to change. Since the length of the belt is constant, the change in effective diameter of one pulley causes a corresponding change in the effective diameter of the other pulley. The effect is that, for each rotation of the crankshaft, the shaft driving the water pump and the fan rotates at the relatively higher speed, thereby causing the water pump and the fan to have more effect on the cooling of the internal combustion engine.

The second pulley, that is the one rotatable with the crankshaft, may have the position of the movable member determined by the SME element and the element, when actuated at the transition range of temperatures, causes the movable member to move towards the fixed member to reduce the separation between said inclined faces of the groove. Such a pulley is shown in Figure 1 of the drawings of our copending application No. 7842736. Serial No.

2033031.

Alternatively, the first pulley, that is the one rotatable with the shaft of the water pump, may have the position of the movable member determined by said SME element and said element, when actuated at the transition range of temperatures, causes the movable member to move away from the fixed member to increase the separation between said inclined faces of the groove. Such a pulley is shown in Figure 2 of the drawings of our co-pending application No.

7842736. Serial No.2033031.

In order that the invention may be more readily understood it will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevation of part of a water-cooled internal combustion engine, Figure 2 is a front view of the engine shown in Figure 1, and Figure 3 is a front view of an alternative embodiment of the invention.

Referring to Figures 1 and 2, an internal combustion engine has a crankshaft 1 extending to the front of the engine with a pulley 3 mounted on the end of the crankshaft. Above the pulley 3 there is positioned a further pulley 5 which is mounted on a shaft 7 parallel with the axis of rotation of the crankshaft and carrying a water pump (not shown) and a multi-bladed fan 9.

The pulley 5, referred to as the first pulley, has a first member 11 which is secured to a sleeve 13 rigidly secured to the shaft 7 and provides an inclined face of the vee groove 1 5 of the pulley. A second member 1 7 is slidable along the shaft and provides the other inclined face of the vee groove.

A biasing spring 19 urges the member 1 7 relative to the shaft 7 towards the fixed member 11.

The pulley 3, referred to as the second pulley, has a fixed member 21 secured to the end of the crankshaft 1 and a member 23 slidable relative to the shaft towards and away from the member 21.

The two members 21, 23 each have an inclined face which together define the vee groove 25 of the pulley. An SME element in the form of a coil spring 27 is interposed between a stop 29 on the shaft 1 and the member 23. A biasing spring 31 is interposed between the two members 21,23 urging the two members apart. A vee belt 33 passes aroung the periphery of part of each of the pulleys and also around a pulley 35 (see Figure 2) which serves to drive an alternator.

When the operating temperature of the element 27 is below its transition range, and this is arranged to be below the normal operating temperature of the engine, the biasing spring 31, aided by a component of the tension in the belt, forces the members 21 and 23 apart so that the belt 33 takes up a position close to the bottom of the groove 25. The effective diameter of the pulley 3 is thus small. The biasing means 1 9 on the first pulley urges the two members 11, 17 towards each other, thereby narrowing the groove and the belt takes up a position towards the outer edge of the groove thus providing a relatively large effective diameter of the pulley. In Figure 2 the belt is shown by a full line.When the SME element reaches its transition temperature, it rapidly expands and tries to revert to its original undistorted shape and the force developed during this change of shape causes the member 23 to be moved towards the member 21 against the action of the biasing spring 31. This has the effect of reducing the width of the gap of the pulley and the belt is forced towards the outer end of the groove, thereby increasing the effective diameter of the pulley.Since the belt is of constant length, the portion of the belt which passes round the pulley 5 is forced towards the bottom of the groove, thereby forcing the member 1 7 away from the member 11 against the action of the biasing spring 1 9. In this situation, as shown in broken lines in Figure 2, a relatively large diameter pulley mounted on the crankshaft rotates a smaller diameter pulley mounted on the shaft 7. This means that the speed of rotation of the fan and the water pump increase as the operation temperature of the engine passes through the transition range of temperatures of the SME element.

One disadvantage with the system described is that the alternator is driven at a low speed when the engine is cold and at a faster speed when the engine is hot. When the engine is cold and the alternator is driven at the lower speed, it may not generate sufficient electrical energy to replace that which is being withdrawn from the battery.

To overcome this problem, the alternator may be driven by a separate belt 37 passing around a constant diameter pulley 39 mounted on the crankshaft. Such an arrangement is shown in Figure 3.

It wili be noted in Figure 1 that the movable part 17 of the pulley 5 is on the opposite side of the belt from the movable part 23 of the pulley 3 and, in this way, the alignment of the belt remains substantialiy constant when the change in diameters of the two pulleys occurs.

In the arrangement shown in Figure 1, the pulley 3 is provided with a biasing spring 31 which acts to bias the members 21, 23 apart.

When the SME element is below its transition range of temperatures, the tension in the belt 33 also serves to force the belt towards the bottom of the groove 25, and the position of the belt in the groove depends upon the combination of the belt tension and the biasing spring.

In an alternative arrangement, however, the biasing spring may be omitted and the belt tension alone, which is a function of the bias spring load on the pulley 5, suffices to keep the members 21,23 apart.

In an alternative arrangement (not illustrated), the pulley providedwith the SME element is mounted on the shaft of the water pump and the fan and the other pulley is mounted on the crankshaft. The two members of the SME pulley are biased together so that the belt is positioned near the outer edge of the groove. When the temperature reaches the transition temperature range of the SME element, the element pushes the movable member away from the fixed member to thereby widen the gap and allow the belt to move towards the centre of the pulley.

Claims

1. A water-cooled internal combustion engine having first and second vee pulleys rotatable with the drive shaft of a water pump and with the crankshaft of the engine respectively, a vee belt passing around part of the periphery of each of said pulleys and wherein each of the pulleys has two members each providing one inclined face of the vee groove of the pulley, one of the members being fixed to the shaft and the other slidable along the shaft to vary the separation of the inclined faces, and the position of the movable member of one of the pulleys relative to the other member of the pulley being determined by an SME element (as herein defined), and the first and second pulleys being arranged such that, at temperatures below the transition range of temperatures of the SME element, the ratio of the effective diameter of the first pulley to that of the second pulley is greater than said ratio at temperatures equal to or greater than said transition range of temperatures of the element.

2. A water-cooled internal combustion engine as claimed in claim 1, in which the second pulley has the position of the movable member determined by said SME element and said SME element, when actuated at the transition range of temperatures, causes the movable member to move towards the fixed member to reduce the separation between said inclined faces of the groove.

3. A water-cooled internal combustion engine as claimed in claim 1, in which the first pulley has the position of the movable member determined by said SME element and said SME element, when actuated at the transition range of temperatures, causes the movable member to move away from the fixed member to increase the separation between said inclined faces of the groove.

4. A water-cooled internal combustion engine as claimed in claim 2, in which the movable member of the first pulley is biased towards the fixed member.

5. A water-cooled internal combustion engine as claimed in any preceding claim, in which a fan is mounted for rotation with the first pulley.

6. A water-cooled internal combustion engine as claimed in any preceding claim, in which the movable members of the first and second pulleys are mounted on opposite sides of the vee belt.

7. A water-cooled internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.