AIR-COOLING MECHANISM FOR THE INTERNAL CENTRE OF AN INTERNAL-COMBUSTION ENGINE

Abstract: This invention relates to an air cooling mechanism for the internal centre of an internal combustion engine (10) which has air jackets (1a,1b,1c,1d) for cooling the internal centre of the engine (10) with air, an atmospheric air inlet (20) and an air exhaust outlet (30), and air suction means (40) for positively exhausting air from the air jackets (1a,1b,1c,1d) whereby cooling air is forcibly caused to flow through the air jackets (1a,1b,1c,1d) to cool the internal centre. Since the energy for said suction means (40) is obtained from the acceleration of the exhaust gas stream from the engine (10), said energy is responsive to the power of the engine (10) and the power of the engine (10) is not affected thereby.

Description: This invention relates to a mechanism for cooling the internal centre of an internal combustion engine directly with air. It is known to employ air cooling in internal combustion engines, and particularly in small-sized engines which generate less heat. As engines increase in size they mostly employ water, oil or other liquid-cooling, with the coolant mostly being water. Since the boiling point of water is little different to the ordinary operating temperature of an engine, the coolant can quickly arrive at the boiling point if the load on the engine is increased or the engine is rotated at high speed to feasibly cause overheating of the engine. The other disadvantages of liquid cooled engines are that their structure is complicated, seals for preventing the liquid from leaking at temperatures up to approximately 100°C must be provided, and engine maintenance is complicated due to management of the quantity and components of the coolant. Moreover a radiator is required to lower the temperature of the coolant in a liquid-cooling type engine, where the heat in the coolant is exchanged with air. Since the mean temperature of the atmospheric air is approximately 20°C, and approximately 50° C under the most severe conditions, there is sufficient temperature difference between the atmospheric air and the boiling point of the coolant to lower the temperature of the coolant and water has the advantage of being almost inexhaustibly available. The present inventor has conducted studies and developed a technique for cooling the internal centre of an internal conduction engine directly with air. As a result, the inventor has discovered the fact that cooling the internal centre of an internal combustion engine not by natural air cooling as in the existing air cooled engines but by forced air cooling gives excellent results. An object of this invention is to provide an air cooling mechanism for the internal centre of an internal combustion engine which can directly cool the internal centre of the engine with air by forcibly introducing cooling air to the internal centre of the engine. In FR-A-352383 is described an air cooling mechanism cooling the internal centre of an internal combustion engine, comprising a plurality of air jackets provided around a combustion chamber of an engine, an air inlet conduit for connecting the air jackets to an atmospheric air inlet and an exhaust conduit connected to air suction means for positively exhausting heated air from the air jackets wherein said air suction means is a negative pressure generator for generating negative pressure by utilizing the exhaust gas stream exhausted from the engine. The present invention provides an air cooling mechanism cooling the internal centre of an internal combustion engine as characterised in claim 1. The air jackets referred to above can be considered to have a similar role to the water jackets in a conventional liquid-cooled engine, with the air passing through the air jackets cooling the periphery of the combustion chamber where heat is generated, i.e., the internal centre of the engine. The intake and the exhaust for the cooling air are important factors, and one of the features of the present invention is to positively exhaust the cooling air and so draw fresh cooling air through the intake. As a result, the air after it has been used for cooling can be exhausted very smoothly and low temperature cooling air can be efficiently introduced through the intake to the air jackets to provide cooling according to the present invention. Negative pressure necessary to draw cooling air into the intake can be obtained by utilizing the engine exhaust gas stream. This provides the best efficiency from the engine. If, for example, electric power or a rotary force was to be produced from the engine to drive a fan for providing the negative pressure, the efficiency of the engine would be reduced. The most significant difference between the air cooling mechanism of the present invention and the conventional air cooling mechanism of an internal combustion engine resides in that the cooling effect of the latter depends upon the relative speed between the engine and the surrounding air, i.e., is dependent upon the speed of a vehicle to which the engine is fitted, while with the mechanism of the present invention the cooling effect is obtained even when a vehicle to which the engine is fitted is stationary. The present invention will be more particularly described with reference to the accompanying drawings, in which:- Fig. 1 is an explanatory view of an embodiment of an entire structure of an air cooling mechanism for the internal centre of an internal combustion engine according to the present invention; Fig. 2 is a cross-sectional view of the engine body of the embodiment; and Figs. 3 and 4 are sectional views of two examples of negative pressure generator of the embodiment. The invention will be described with respect to an embodiment of an air cooling mechanism for the internal centre of an internal combustion engine according to the present invention with reference to the accompanying drawings. In the drawings, reference numeral 10 designates an engine in which an air cooling mechanism of the present invention is carried out, numeral 20 denotes an atmospheric air inlet, numeral 30 depicts an exhaust conduit for heated air after heat exchanging, and numeral 40 indicates a negative pressure generator forming an air suction means, provided in a muffler 51 of an exhaust manifold 50. Air jackets 1a, 1b, 1c, 1d, are respectively so provided in the engine 10 as to surround the peripheries of heat generators, such as a cylinder 11, a piston 12, a cylinder head 13, etc. Air introduced through the atmospheric air inlet 20 and purified by a filter 21 passes by way of an air inlet conduit 22 and one or more ports 23 into the air jackets 1a. An exhaust conduit 30 is connected to the air jackets 1a, to exhaust the air after heat exchange, and the other end of the conduit 30 being connected to the negative pressure generator 40. The negative pressure generator 40 is constructed as shown in Figs. 3 and 4. Fig. 3 shows an example of producing negative pressure in the exhaust conduit 30 only by an exhaust gas stream from the engine. The negative pressure generator 40 has a conical accelerator 41 provided at the upstream side of a throttle 42 for throttling the sectional area of the passage and the exhaust conduit 30 is connected to the downstream side of the throttle 42. Reference numeral 52 designates the main passage of the muffler 51, numeral 53 denotes ports for silencing sounds, and numerals 54 and 55 depict inner and intermediate cylinders for forming a bypass passage to which an exhaust gas stream is fed through the ports 53. Fig. 4 shows an example of forming negative pressure responsive to the velocity of air during operation of e.g., a vehicle fitted with the engine, having acceleration conduits 61, 62, 63 and 64 for introducing atmospheric air in multiple stages in addition to the construction similar to that of Fig. 3. The exhaust conduit 30 is not shown in Fig. 4 but is to the left of the conduits 63, 64. Thus, stronger negative pressure can be produced. If desired, two or more negative pressure generators 40 may be provided, e.g., at the front and rear of the exhaust gas stream. Reference numeral 60 designates a fan, which may be auxiliarily used arbitrarily. When the fan 60 is used, the natural air cooling of the outside of the engine 10 is accelerated. With the mechanism of the invention, when the engine 10 is operated, negative pressure is formed in the negative pressure generator 40 as the exhaust gas stream is exhausted from the exhaust manifold. As a result, a stream of cooling air is forcibly directed from the atmospheric air inlet 20 through the air jackets 1a, of the engine 10 and the exhaust conduit 30 toward the downstream of the muffler 51. The atmospheric air purified and introduced through the inlet 20 is fed to the air jackets 1a, which surround the internal centre of the engine 10 where the combustion tends to produce high temperatures to thermally exchange the high temperature of the internal centre with the cool atmospheric air temperature by a large temperature difference to thus cool the internal centre of the engine 10, with the heated cooling air being exhausted through the exhaust conduit 30 to the negative pressure generator 40 to be exhausted with the exhaust gases from the engine downstream of the muffler 51. There thus arises an advantage that the exhaust gas temperature can be reduced by the air stream combining with the exhaust gas at the downstream side of the muffler. When the rotating speed of the engine is increased, the internal centre of the engine increases in temperature, the velocity and the flow rate of the exhaust gas stream from the engine also increases to provide stronger negative pressure, thereby increasing the cooling effect. When the air suction means is constructed as shown in Fig. 4, since the air stream from outside of the engine can be utilized, the intake of cooling air is further enhanced. Therefore, according to the present invention, there is obtained the effect of holding the internal centre of an internal combustion engine at operating temperature by forcibly cooling the internal centre of the engine directly with air. Further, since negative pressure utilizing the exhaust gas stream of the engine can be utilized to forcibly cool the engine, the loss of power from the engine is minimal and the engine can perform at extremely high efficiency. According to the present invention, measures for circulating liquid and sealing against liquid leakage necessary for liquid cooled engines are entirely unnecessary, engine maintenance is remarkably simplified, the weight of the engine is significantly reduced, and the cooling effect is very rapidly presented.

Claims: An air cooling mechanism cooling the internal centre of an internal combustion engine, comprising a plurality of air jackets (1a,1b,1c,1d) provided around a combustion chamber (11) of an engine (10), an air inlet conduit (22) for connecting the air jackets (1a,1b,1c,1d) to an atmospheric air inlet (20) and an exhaust conduit (30) connected to air suction means (40) for positively exhausting heated air from the air jackets (1a,1b,1c,1d) wherein said air suction means is a negative pressure generator (40) for generating negative pressure by utilizing the exhaust gas stream exhausted from the engine (10), characterised in that the negative pressure generator (40) has a conical accelerator (41) at the upstream side of a throttle (42), and the exhaust conduit (30) is connected at the downstream side of the throttle (42). An air cooling mechanism according to claim 1, characterised in that the negative pressure generator (40) further comprises conduits (61,62,63,64) for introducing atmospheric air to the exhaust gas flow and in that the exhaust conduit (30) is connected at the downstream side of the conduits (61,62,63,64). An air cooling mechanism according to either one of claims 1 and 2, wherein said negative pressure generator (40) is disposed at the downstream side of an exhaust gas muffler (50). An air cooling mechanism according to claim 3, wherein two or more said negative pressure generators (40) are provided at the front and rear of the exhaust gas stream.

Inventors: KAKUTA, YOSHIAKI
Applicants: KAKUTA, YOSHIAKI
Application year: 1988
Main classification: F01P1
IPC codes: F01P1, F01P5