The invention relates more particularly to a heat exchanger for use in conjunction with an internal combustion engine.

It is known to heat a liquid fuel prior to carburetion or injection thereof in an internal combustion engine, especially in relation to diesel before injection. Such heating of a liquid fuel will herein be referred to as pre-heating thereof and a pre-heater, as referred to herein, must be interpreted as a device for pre-heating a liquid fuel. It is known that pre-heating of a liquid fuel to an optimum temperature improves the performance and fuel economy of an engine whilst reducing engine emissions that are potentially harmful to the environment. The current invention aims to provide an improved pre-heater for an internal combustion engine for pre-heating the liquid fuel prior to carburetion or injection thereof, as the case may be, into the engine to a substantially constant temperature of the fuel after pre-heating.

A heating liquid as referred to herein must be interpreted as a liquid which flows, in an internal combustion engine and/or one or more of its ancillary components, at a

temperature above ambient temperature, such as the cooling liquid of a liquid-cooled engine, the lubrication oil of an engine, and the like.

According to the invention there is provided a pre-heater for an internal combustion engine for pre-heating liquid fuel, utilizing a heating liquid of the engine, to within a predetermined small deviation from a predetermined optimum temperature, irrespective of such variables as the ambient temperature of the fuel, the rate of flow of the fuel, and the temperature of heating liquid entering the pre-heater, the pre- heater including a heat exchanger for transferring heat from a heating liquid to a liquid fuel, the heat exchanger defining therethrough a fuel flow passage between a fuel inlet end and a fuel outlet end and a heating liquid flow passage between a heating liquid inlet end and a heating liquid outlet end, the heat exchanger being connectable, via its fuel inlet and outlet ends, in line with a fuel line of an internal combustion engine and, via its heating liquid inlet and outlet ends, in parallel with a line of the engine carrying a heating liquid ; a temperature sensitive flow regulator connected in line with the heating liquid flow passage and downstream of the heat exchanger, for regulating the rate of flow of heating liquid through the heat exchanger, the flow regulator including a temperature actuated valve which, in use of the pre-heater, progressively closes as the temperature of heating liquid passing through the flow regulator increases and progressively opens as the temperature of heating liquid passing through the flow regulator decreases.

In the operative configuration of the pre-heater, its heat exchanger is connected, via its fuel inlet and outlet ends, in line with a fuel line of an internal combustion engine and, via its heating liquid inlet and outlet ends, in parallel with a line of the engine carrying a heating liquid. Provided that the pre-heater is suitably configured to match the particular engine, its operation, including particularly the opening and closing of

the temperature actuated valve in response to the temperature of heating liquid passing through the flow regulator, as aforesaid, and transfer of heat from the heating liquid to the fuel within the heat exchanger, will result in the fuel exiting the fuel flow passage of the heat exchanger being at a temperature within a small deviation from a predetermined optimum temperature. The optimum fuel temperature is the temperature at which the combination of temperature and viscosity of the fuel, the latter being a function of the former, is such that optimum combustion of the fuel in the engine will result. In operating conditions where ambient temperature varies, efficient operation of the pre-heater will require that the effect of ambient temperature on heat loss of cooling liquid occurring between the heat exchanger and the temperature sensitive flow regulator, if any, be minimized. As such, where the flow regulator and the heat exchanger are separate units, the flow regulator may be connected to the heat exchanger as near as possible to the outlet end of its heating liquid flow passage.

The pre-heater and the flow regulator may define matching connecting formations for directly interconnecting them. Such matching connecting formations may be screw thread formations permitting the flow regulator to be screwed directly onto the heat exchanger at its heating liquid outlet end. Alternatively, the heat exchanger and the flow regulator may be incorporated into a single unit.

The heat exchanger of the pre-heater may be a plate-type heat exchanger and its plates may be of a generally rectangular shape. The plates of the heat exchanger may be made from a material that has a high thermal conductivity, such as stainless steel, brass, and the like.

The flow regulator may include a body made of any suitable materials such as stainless steel, brass, and the like. The temperature actuated valve may define a seat formation and a flow aperture within the seat formation and may include an actuation mechanism and a closure member, linearly displaceable with respect to the seat formation under bias of the actuation mechanism, for regulating flow of heating liquid

through the aperture in response to the temperature of heating liquid passing through the flow regulator, as aforesaid. The temperature actuated valve may provide slack between the actuation mechanism and the closure member, against bias of a spring, to prevent damage to the valve under bias of the actuation mechanism when the closure member seats against the seating formation.

In the case of the fuel being a diesel fuel, the optimum fuel temperature may be approximately 62oC and the corresponding small deviation may be approximately 2°C.

The pre-heater may include an adjustable throttle valve that provides a further means for regulating the rate of flow of heating liquid through the pre-heater, thus operatively regulating the temperature of the heating liquid exiting from the pre-heater and, consequently, also the temperature of fuel exiting the pre-heater. As such, the adjustable throttle valve provides for adjustment of the rate of flow of heating liquid through the pre-heater for any given extent of opening of the temperature actuated valve. Upon implementation of the pre-heater on an engine, the throttle valve may be initially adjusted so that the pre-heater maintains the temperature of the fuel exiting therefrom at its predetermined optimum temperature while the engine is operating at a speed of approximately half its maximum operating speed and at its normal operating temperature. The throttle valve may be incorporated in the flow regulator. It may, alternatively, be incorporated in the heat exchanger.

The temperature actuated valve of the flow regulator may have adjustment means for adjusting the extent of opening of the valve for a given temperature of heating liquid passing through the flow regulator. As such, the adjustment means provides a means for adjustment of the rate of flow of heating liquid through the pre-heater for any given temperature of heating liquid passing through the flow regulator. By means of the said adjustment means, the temperature actuated valve may, upon implementation of the pre-heater on an engine, be adjusted so that the pre-heater maintains the temperature of fuel exiting therefrom at its pre-determined optimum

temperature while the engine is operating at a speed of approximately half of its maximum operating speed and at its normal operating temperature.

The adjustable throttle valve or the adjustment means of the temperature actuated valve or both, as the case may be, provide (s) for the pre-heater to be highly adjustable for matching different types of engines with which it may be used and for different operating conditions. As such, a universal pre-heater may be provided which can be suitably adjusted for use with any of a wide range of different engines and/or in a wide range of different operating conditions.

The invention extends also to a temperature sensitive flow regulator as such, as defined herein, for use in conjunction with a heat exchanger.

The above and other features of the invention will now be described with reference to an embodiment of a pre-heater, in accordance with the invention, as illustrated in the accompanying diagrammatic drawings. In the drawings: Figure 1 shows a diagrammatic illustration of a water-cooled internal combustion diesel engine, its fuel supply system, and an embodiment of a pre-heater, in accordance with the invention, connected in line with the fuel supply line and in parallel with a line carrying cooling water of the engine; Figure 2 shows a diagrammatic general view of the pre-heater of Figure 1 in an inoperative configuration; Figure 3 shows a diagrammatic sectional view of the pre-heater of Figure 1 along the line III-III of Figure 2 with a valve thereof in an operative configuration; Figure 4 shows the detail A of Figure 3; and

Figure 5 shows a diagrammatic sectional view of a part of the pre-heater of Figure 1 along the line V-V of Figure 2.

In Figure 1, a pre-heater, in accordance with the invention, is designated generally by the reference numeral 10. The pre-heater 10 is shown installed on an internal combustion diesel engine 12. Liquid fuel in the form of diesel 14 is stored in a fuel tank 16 and supplied to the engine 12 via a fuel line 18 having connected in line therewith a fuel pump 20, two fuel filters 22, the pre-heater 10, and a temperature gauge 34. The fuel line 18 terminates in a diesel injector pump 24. A return fuel line 26 operatively serves to return excess diesel to the fuel tank 16.

As the engine 12 is water-cooled, water is the heating liquid as defined herein. The water-cooling system of the engine 12 includes a radiator 28 and a heating liquid line in the form of a water line, which includes an internal passage (not shown) defined through the engine 12 and connecting pipes 29.1 and 29.2 interconnecting the radiator 28 with the internal passage of the engine. In operation of the engine 12, water is circulated by a water pump (not shown) through the internal passage of the engine 12, via the connecting pipe 29.1, into the radiator 28, via the connecting pipe 29.2, and into the internal passage again. By means of a first water pipe 30, extending between a port 31 of the internal passage of the engine 12 and the pre- heater 10, and a second water pipe 32, extending from the pre-heater 10 to the connecting pipe 29.2, the pre-heater 10 is connected in parallel with the said water line.

The pre-heater 10 includes a plate-type heat exchanger 36 and a temperature sensitive flow regulator 38. The heat exchanger 36 defines therethrough a water flow passage between a water inlet end 40 and a water outlet end 46 and a diesel flow passage between a fuel inlet end 44 and a fuel outlet end 42. Details of the pre- heater 10 will be described hereinafter. In operation of the engine 12 and the pre- heater 10, the temperature of water entering the water inlet end 40 of the heat

exchanger 36 is determined by the engine 12 and its cooling system, as regulated by its thermostat (not shown).

With reference particularly to Figures 2 and 3 of the drawings, the heat exchanger 36 has a box-like outer shell 50 made of stainless steel within which generally rectangular stainless steel plates 52 are spaced in parallel relation to define between them passages 54 and 56. In operation of the pre-heater 10, water enters the heat exchanger 36 through the inlet end 40, flows through the passages 54, and exits the heat exchanger through the outlet end 46. The passages 54 thus form part of the water flow passage defined by the heat exchanger 36. Similarly, diesel enters the heat exchanger 36 through the inlet end 44, flows through the passages 56, and exits the heat exchanger through the outlet end 42. The passages 56 thus form part of the diesel flow passage defined by the heat exchanger 36. Such flow operatively provides for heat transfer from the water to the diesel while both liquids are passing through the heat exchanger 36.

The flow regulator 38 of the pre-heater 10 is screwed onto the heat exchanger 36 at its water outlet end 46 by means of matching connecting formations in the form of screw thread formations 58 defined by the flow regulator and the heat exchanger.

As such, the flow regulator 38 is connected in line with the water flow passage of the heat exchanger 36 downstream of the heat exchanger. In this arrangement, heat loss of water between the heat exchanger 36 and the flow regulator 38 is minimized and, more particularly, the effect of ambient temperature on such heat loss is minimized.

With reference particularly to Figure 4, the flow regulator 38 has a brass body 60 defining therein a cavity 62 which is in liquid communication with the outlet end 46 of the heat exchanger 36 via a round flow aperture 64 defined by the body 60 within an internal seat formation in the form of a seat surface 66 thereof. An axis 68 is defined perpendicular to the surface 66 and through the center of the aperture 64.

The flow regulator 38 has also an outlet port 70 which is in liquid communication

with the cavity 62 and to which the second water pipe (see reference numeral 32 in Figure 1) is operatively connected.

The flow regulator 38 has a temperature actuated valve 72 within the cavity 62 defined therein. The temperature actuated valve 72 includes a frame 74, which is mounted on the body 60 by means of springs 76 in a configuration which permits the frame to be linearly displaced in a direction parallel to the axis 68.

The valve 72 includes further a first round disc 78 parallel to the surface 66 and co- axial with the axis 68. The frame 74 defines therein a round aperture 77 and the valve 72 includes a closure member in the form of a second round disc 79, which regulates the flow of water through the said aperture and which can block it off. The valve 72 includes further a temperature sensitive actuation mechanism including a bulb 81 (of which the internal details are not shown) containing an expansive gel, a spring 83, and a pin 85 protruding from the bulb and actuated by the expansive gel.

Insofar as the operation of the said actuation mechanism is essentially conventional, it will not be described in detail herein. The actuation mechanism responds to an increase in its temperature by displacing the pin 85 in a direction outward from the bulb 81, thus causing the bulb, the disc 78, and the disc 79 to be displaced towards the aperture 64, against the bias of the spring 83. Conversely, it responds to a decrease in its temperature by permitting the spring 83 to displace the bulb 81, the disc 78, and the disc 79 away from the aperture 64.

In operation of the pre-heater 10, water exiting from the outlet end 46 enters the cavity 62 defined in the body 60 of the flow regulator 38 via the aperture 64 and exits the flow regulator via the port 70. The port 70 operatively is connected to the second water pipe (see reference numeral 32 in Figure 1). The valve 72 is thus continuously submerged in water that has exited from the heat exchanger 36. The valve 72 responds to the temperature of the water passing through the flow regulator 38 by progressively displacing its disc 78 towards the aperture 64 as the temperature increases, thus progressively closing the aperture 64 and decreasing the rate of flow

of water through the flow regulator. Conversely, the valve 72 responds to a decrease in the temperature of the water by displacing its disc 78 away from the aperture 64, thus progressively opening the aperture 64 and increasing the rate of flow of water through the flow regulator 38.

By regulating the rate of flow of water through the flow regulator 38 as aforesaid and, consequently, also the rate of flow of water through the heat exchanger 36, the flow regulator regulates the time that water passing through the passages 54 is effectively in thermal communication with the cooler diesel in the passages 56 and with the cooler atmosphere surrounding the heat exchanger. All other operating conditions being equal, the drop in temperature experienced by water passing through the heat exchanger 36 will thus decrease as the rate of flow of water increases and will increase as the rate of flow of water decreases. As a result, a slower rate of flow of the water will result in a reduction in the temperature of water exiting from the outlet end 46, and vice versa. The drop in temperature experienced by the water passing through the heat exchanger 36 also will be influenced by the rate of flow of diesel through the heat exchanger and the ambient temperature of the diesel.

The opening or closing of the temperature actuated valve 72 in response to the temperature of the water, in conjunction with the operation of the heat exchanger, i. e. the transfer of heat from the water to the diesel therein, results in the temperature of diesel exiting the outlet end 42 being maintained within a range between 61 °C and 64°C. It is thus maintained within a small deviation, not exceeding 2°C, from an optimum diesel temperature of 62°C.

The disc 79 generally is fixed in relation to the disc 78. If, however, the said discs are displaced towards the aperture 64 to the extend that the disc 78 seats against the surface 66, thus closing the aperture, the disc 78 will be arrested and thereafter further displacement of the disc 79 towards the aperture 64 is provided for via slack provided in the valve 72 against the bias of a spring 87. Such slack is provided to prevent damage to the valve 72 under bias of the actuation mechanism.

At ambient temperature, the disc 79 is positioned to close off the aperture 77. The frame 74 defines therethrough also an aperture 89 permitting a nominal flow of water through the flow regulator 38 when the aperture 77 is so closed off. As the temperature of the water in the cooling system of the engine 12 rises after the engine has been started, the disc 79 is displaced away from the aperture 77 and water is permitted to flow past the disc 79 and through the said aperture. When the engine 12 is operating within its normal operating temperature range, the flow of water through the flow regulator is restricted by the disc 79 to a limited degree only and thus effectively is regulated by the valve 72 regulating the clearance between the disc 78 and the surface 66. The extent of opening of the valve 72, as referred to herein, is thus the extent of opening as determined mainly by the clearance between the disc 78 and the surface 66.

For the sake of clarity, the valve 72 is shown here in an operative configuration in which the aperture 77 is open. It must be appreciated, however, that in the inoperative configuration of the pre-heater 10, particularly at ambient temperature, the disc 79 is positioned to close off the aperture 77, as aforesaid.

With reference to the drawings in general and to Figure 5 in particular, the flow regulator 38 includes also an adjustable throttle valve 80 comprising a needle 82 and a seat formation 84 against which the needle can sealingly seat. The needle 82 has a screw thread formation 86 matched to a screw thread formation defined by the body 60 permitting the needle 82 to be displaced towards or away from the seat formation 84 by a screwing action. Such screwing action may be performed by inserting an allen key (not shown) into an allen key formation 88 defined at an end of the needle 82 projecting through the body 60.

In operation of the pre-heater 10, water passes between the needle 82 and the seat formation 84 as it flows from within the cavity 62 to the port 70. By adjusting the clearance between the needle 82 and the seat formation 84, an additional means is provided to regulate the rate of flow of water through the flow regulator 38. As such,

the throttle valve 80 provides for adjustment of the rate of flow of water through the pre-heater 10 for any given extent of opening of the temperature actuated valve 72.

Upon implementation of the pre-heater 10 on the engine 12, the throttle valve 80 was initially adjusted so that the pre-heater maintained the temperature of the diesel exiting therefrom at 62°C while the engine was operating at a speed of approximately half its operating speed and at its normal operating temperature.

With reference to the drawings in general and to Figure 4 in particular, the temperature actuated valve 72 has adjustment means in the form of a spindle 90 to adjust the clearance between the disc 78 and the surface 66, i. e. the extent of opening of the valve, for a given temperature of water passing through the flow regulator 38. The spindle 90 is generally cylindrical and is co-axial with the axis 68.

The spindle 90 defines a round screw thread formation 92 to co-operate with a matching screw thread formation defined by the body 60 and further defines an allen key formation 96 and a bearing formation 98 bearing against a matching bearing formation 100 defined by the frame 74. While screwing the spindle 90 in relative to the body 60 by means of an allen key (not shown) inserted into the formation 96, the valve 72, and particularly its disc 78, may be linearly displaced towards the aperture 64 against the bias of the springs 76. When screwing the spindle out relative to the body 60, the springs 76 are permitted to displace the valve 72, particularly its disc 78, away from the aperture 64, thereby increasing the extent of opening of the valve.

As such, the valve 72 may be adjusted to regulate the rate of flow of water through the pre-heater 10 for any given temperature of the water passing through the flow regulator 38. Upon implementation of the pre-heater 10 on the engine 12, the valve 72 was adjusted to regulate the rate of flow of water through the pre-heater so that the pre-heater maintained the temperature of the diesel exiting from the fuel outlet end 42 of the heat exchanger 36 at 62°C while the engine 12 was operating at a speed of approximately half of its maximum operating speed and at its normal operating temperature. As such, the said effect may be achieved by adjusting the valve 72 in conjunction with the throttle valve 80.