Abstract:
A fluid cooling system for an engine ( 101 ). The fluid cooling system comprises a junction ( 105 ), the junction comprising: a primary duct ( 102 ) suitable for conveying fluid into the junction; and a secondary duct ( 103 ) and a tertiary duct ( 104 ), the secondary and tertiary ducts being in fluid communication with the primary duct and being suitable for conveying fluid out of the junction. The secondary duct is arranged at a substantially oblique angle to the primary duct at the point at which the secondary duct meets the primary duct, and the tertiary duct is arranged at a substantially acute angle to the primary duct at the point at which the tertiary duct meets the primary duct.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to a fluid cooling system for an engine, and to an engine and a vehicle comprising the same. 
       BACKGROUND 
       [0002]    In order to prevent mechanical wear, engines will frequently make use of lubricants. The lubricants are interspersed between the moving parts of the engine in order that the parts can move more smoothly with respect to one another. The viscosity of the lubricants in an engine will vary with temperature, and usually the lubricants are chosen such that they will perform well at the engine&#39;s typical operating temperature. However, for an engine which generates a significant amount of heat, such as an internal combustion engine, the engine will typically begin at an ambient temperature before rising to its typical operating temperature as the engine generates heat. Therefore there is a period when the engine is started during which the lubricants within the engine are beneath their optimum operating temperature. For this reason it is often desirable to allow components such as pistons and cylinders to heat up as quickly as possible when the engine is started, in order to ensure that the lubricating oils within the pistons are as effective as possible. 
         [0003]    However, pistons and cylinders are also at risk of becoming too hot. In particular, the components contained at the head of the cylinder such as spark plugs and sensing apparatus are often very sensitive to being overheated. Therefore cylinders in modern engines are provided with an outer shell, or jacket, which is filled with a fluid, typically water. These water jackets provide cooling as the heat from the piston and the cylinder is absorbed by the water. The warmed water is then pumped out of the jacket and replaced with colder water to absorb more heat. 
         [0004]    However, during engine start up, the jacket is still full of water, and as such the jacket tends to absorb heat, slowing the warming of the piston and the cylinder, and therefore slowing the warming of the lubricant and reducing the efficiency of the lubricant shortly after the engine is started. This effect is worsened if cooler water is allowed to flow into the jacket during the warming up period. 
         [0005]    It is important therefore to provide a water jacket that can provide effective cooling for the vehicle while also minimising heat loss during the early stages after the internal combustion engine is started. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with an aspect of the present invention there is provided a fluid cooling system for an engine. The fluid cooling system comprises a first cooling jacket, a second cooling jacket and a junction, the junction comprising: a primary duct suitable for conveying fluid into the junction; and a secondary duct and a tertiary duct, the secondary and tertiary ducts being in fluid communication with the primary duct and being suitable for conveying fluid out of the junction. The secondary duct is in further fluid communication with the first cooling jacket and the tertiary duct is in further fluid communication with the second cooling jacket. The secondary duct is arranged at a substantially oblique angle to the primary duct at the point at which the secondary duct meets the primary duct, and the tertiary duct is arranged at a substantially acute angle to the primary duct at the point at which the tertiary duct meets the primary duct. 
         [0007]    In this way a junction is provided in which fluid is able to travel easily from the primary duct into the secondary duct, but in which fluid travelling into the tertiary duct encounters a greater resistance due to the acute change of direction which the fluid must undergo. As such, more fluid will tend to flow through the secondary duct than the tertiary duct. This difference can be provided based solely on the shape and relationship of the ducts, without the need for complicated valve systems which may be subject to mechanical failure after repeated use. As such, when fluid is flowing under pressure through the junction, for example because it is being pumped, more fluid will tend to be supplied to the first cooling jacket, through the secondary duct, than will be supplied to the second cooling jacket, through the tertiary duct. The larger quantities of fluid flowing through the first cooling jacket will tend to cause the first cooling jacket to absorb more heat than the second cooling jacket, all other factors being equal. In use, therefore, an engine component which is contained inside the first cooling jacket will tend to have more heat energy removed than an engine component which is contained inside the second cooling jacket. 
         [0008]    By substantially oblique it is meant that fluid flowing from the primary duct into the secondary duct will undergo a translation in direction of travel which is less than ninety degrees. It may be that fluid flowing from the primary duct into the secondary duct will undergo a translation in direction of travel which is less than thirty degrees. By substantially acute it is meant that fluid flowing from the primary duct into the tertiary duct will undergo a translation in direction of travel which is greater than ninety degrees. It may be that fluid flowing from the primary duct into the tertiary duct will undergo a translation in direction of travel which is greater than one hundred and fifty degrees. It may be that the tertiary duct is arranged with respect to the primary and secondary ducts, for example by virtue of required translation in direction of travel of fluid and/or by virtue of size, so that a majority of the flow from the primary duct enters the secondary duct. 
         [0009]    Typically, the primary and secondary ducts form a single duct. Where this is the case, it may be that a hole is bored in the single duct that forms the primary and secondary ducts, with the tertiary duct being attached to the primary and secondary ducts at the hole in order to form the junction. 
         [0010]    It may be that the engine is an internal combustion engine. However a cooling system according to the invention may be used with any engine or system which requires cooling, particularly where such engine or system requires or would benefit from cooling at least at two differing rates. 
         [0011]    Where the engine is an internal combustion engine, it may be a piston driven internal combustion engine. Where this is the case, the fluid cooling system may comprise a first water jacket for a piston cylinder head, the secondary duct being in fluid communication with the first water jacket. The fluid cooling system may comprise a second water jacket for a piston cylinder, the tertiary duct being in fluid communication with the second water jacket. Typically, such a second water jacket is intended to cool a section of the piston cylinder through which the piston travels. 
         [0012]    It may be that the tertiary duct is connected to a lower portion of the second water jacket. Lower here means lower with respect to gravity. It may be that the tertiary duct is connected to the bottom half of the second water jacket. It may be that the tertiary duct is connected to the bottom of the second water jacket, or it may be that the tertiary duct is connected adjacent the bottom of the second water jacket. 
         [0013]    Typically, the fluid cooling system further comprises a pump, the pump being in fluid communication with the primary duct and suitable for pumping fluid into the junction. It may be that the pump is in fluid communication with at least one of the first and second water jackets and is suitable for pumping fluid out of the first and/or second water jacket. 
         [0014]    Alternatively, the fluid may be moved around the system using some other method, for example by relying upon convection currents. 
         [0015]    It may be that the fluid comprises water. Typically, such fluid is primarily water by mass. The fluid may comprise other fluids such as additives intended to lower the freezing point of the water. 
         [0016]    It may be that the secondary duct has a bore substantially the same as the bore of the primary duct. It will be appreciated that this means that it has the same cross-sectional area. It may be that the tertiary duct has a bore smaller than the bore of the secondary duct. It may be that the tertiary duct has a bore smaller than the bore of the primary duct. A smaller cross sectional area in the bore of the tertiary duct helps to further reduce the flow of fluid through the tertiary duct as compared to the secondary duct. 
         [0017]    It may be that the second cooling jacket comprises a heater. The heater may be located inside the second cooling jacket. Alternatively, the heater may be located adjacent to the second cooling jacket. The heater may be an electrical heater. 
         [0018]    The second cooling jacket may comprise a first compartment and a second compartment, the second compartment being joined to the first compartment by one or more capillaries or ducts, the tertiary duct being connected to the first compartment. Where a heater is provided, the heater will typically be located in or next to the second compartment, such that the heater can heat fluid within the second compartment. 
         [0019]    It may be that the fluid cooling system has a typical orientation for use, wherein the tertiary duct reaches the second cooling jacket at a point substantially lower than the junction when the fluid cooling system is in the typical orientation. 
         [0020]    In an aspect, the invention provides a method of cooling an engine, the method comprising:
       providing a fluid cooling system as described above;   attaching the fluid cooling system to the engine; and   pumping fluid around the fluid cooling system.       
 
         [0024]    In an aspect, the invention provides an engine which comprises a fluid cooling system as described above. In an, the invention provides a vehicle which comprises an engine, the engine comprising a fluid cooling system as described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Exemplary embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: 
           [0026]      FIGS. 1  shows a diagram of a first cooling system according to the invention; 
           [0027]      FIGS. 2 and 3  show a second cooling system; and 
           [0028]      FIGS. 4, 5 and 6  show a third cooling system. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIG. 1  shows a diagram of a first cooling system  101  according to the invention. The cooling system  101  is intended for use with a piston driven internal combustion engine (not shown) and comprises a first primary duct  102 , a first secondary duct  103  and a first tertiary duct  104 , which are all connected at a junction  105 .  FIG. 1  shows the first cooling system in substantially the same orientation in which it would be installed in a vehicle, with the upper parts of the diagram representing those parts which would be higher with respect to gravity in a vehicle fitted with the first cooling system  101 . 
         [0030]    The first secondary duct is further connected to a first water jacket  106 , which is intended to fit around and provide cooling for a piston cylinder head (not shown). The first water jacket  106  is provided with a first outflow  107 . 
         [0031]    The first tertiary duct  104  is further connected to a second water jacket  108  which is intended to fit around and provide cooling for the section of a piston cylinder through which a piston head travels (also not shown). The second water jacket  108  is provided with a second outflow  109 , which comprises a valve  110 . 
         [0032]    In use, water is pumped around the first cooling system  101  in the directions shown by the arrows  111 , so that the water will absorb excess heat from the piston cylinder and the piston cylinder head. The water then travels via the first and second outflows  107 ,  109 , to a radiator where the water is allowed to cool before being pumped through the first cooling system  101  again. This prevents the piston cylinder and the piston cylinder head from becoming hot enough to damage the components contained therein. 
         [0033]    However when the engine is cold, which typically occurs immediately following an engine start, it may be advantageous to encourage rapid warming of the piston cylinder. When the engine is cold, therefore, the valve  110  may be closed to prevent outflow of water from the second water jacket  108  through the second outflow  109 . Hence water in the second water jacket  108  will tend to be trapped there. The water trapped in the second water jacket  108  then absorbs heat from the piston cylinder. This still slows the rate at which the piston cylinder will heat up, but since the warmed water is retained next to the piston cylinder, the piston cylinder is able to heat up faster than would be the case if the valve  110  was open. 
         [0034]    Typically, even immediately after start up it is still necessary to pump water through the first primary and first secondary ducts  102 ,  103  to the first water jacket  106 . This is because the cylinder head tends to generate a lot of heat very rapidly, and also contains equipment which is sensitive to overheating. 
         [0035]    The first tertiary duct  104  and the second water jacket  108  are designed to reduce syphoning of water into and out of the second water jacket  108 , and so more effectively trap water, particularly warmer water, in the second water jacket  108 . 
         [0036]    Firstly, the first tertiary duct  104  is connected to the junction  105  at an acute angle to the first primary duct  102 . As a result, the flow of water through the first tertiary duct  104 , when such a flow occurs, is also at an acute angle to the flow of water through the first primary duct  102 . Therefore water flowing through the first primary duct  102  to the junction  105  must alter its course substantially in order to enter the first tertiary duct  104 , as indicated by the arrows  111 . In contrast, the first secondary duct  103  is arranged as a continuation of the first primary duct  102 , so that water flowing from the first primary duct  102  into the first secondary duct  103  does not need to alter its course. The inventor has found that this relationship between the ducts tends to reduce the amount of water which flows into the second water jacket  108 , in particular when the valve  110  is closed. 
         [0037]    Secondly, the first tertiary duct  104  is connected to the bottom of the second water jacket  108 . As the water in the second water jacket  108  absorbs heat from the piston cylinder, the hottest water will tend to rise to the top of the second water jacket  108 , which is also the top of the diagram shown in  FIG. 1 . As such, the hottest water is trapped at the opposite end of the second water jacket  108  from the fluid connection with the first tertiary duct  104 . This tends to prevent thermo-syphoning of water from the second water jacket  108 . Such thermo-syphoning may be undesirable in a circumstance in which a rapid initial warming up of the piston cylinder is preferable. 
         [0038]    Once the piston cylinder has achieved a desired temperature, the valve  110  can be opened to allow a flow of water out of the second water jacket  108 . Some of the colder water being pumped through the first primary duct  102  will then travel down the first tertiary duct  104  and into the second water jacket  108 , where it can absorb heat from the piston cylinder and so help to regulate the temperature of the piston cylinder. 
         [0039]    However, even once the valve  110  is open the water flow through the first tertiary duct  104  will still be less than the water flow through the first secondary duct  103 , due to the acute angle between the first tertiary duct  104  and the first primary duct  102 . As such, more cooling water is delivered to the first water jacket  106  than to the second water jacket  108 . As such the piston cylinder loses less heat than, and can be maintained at a higher temperature than the piston cylinder head. The precise relationship between the water pumped through the secondary and tertiary ducts can be controlled by adjusting the angle of the tertiary duct relative to the primary duct. 
         [0040]    The first tertiary duct  104  is also narrower than the first secondary duct  103 , in that it has a bore with a smaller cross-sectional area. This has the effect of further restricting the water flow into the second water jacket  108 . The relationship between the water pumped through the first secondary duct  103  and the first tertiary duct  104  can therefore also be controlled by changing the bore of the tertiary duct relative to the bore of the secondary duct. 
         [0041]      FIGS. 2 and 3  show a section of a second cooling system  201  according to the invention. Like components with the first cooling system  101  are numbered with like numerals, except in the two hundreds range rather than the one hundreds range. The second cooling system  201  comprises a second primary duct  202 , a second secondary duct  203  and a second tertiary duct  204 , which are arranged in a similar manner to the ducts in  FIG. 1 . Water flows through the ducts as indicated by the arrows  211  in  FIG. 2 . The second secondary duct  203  is connected to a third water jacket for a piston cylinder head (not shown). The second tertiary duct  204  is connected to a fourth water jacket  208  which is intended to fit around several piston cylinders. 
         [0042]    As with the first cooling system  101 , the second tertiary duct is connected to the bottom of the fourth water jacket to reduce thermal syphoning. The second tertiary duct  204  is also arranged at an acute angle to the second primary duct  202  in order to reduce water flow from the second primary duct  202  into the second tertiary duct  204 . 
         [0043]      FIGS. 4 and 5  show a section of a third cooling system  301  according to the invention. Like components with the first cooling system  101  are numbered with like numerals, except in the three hundreds range rather than the one hundreds range. The third cooling system  301  comprises a third primary duct  302 , a third secondary duct  303  and a third tertiary duct  304 , which are arranged in a similar manner to the ducts in  FIG. 1  and  FIG. 2 . Water flows through the pipes as indicated by the arrows  311  in  FIG. 4 . The third secondary duct  303  is connected to a fifth water jacket for a piston cylinder head (not shown). The third tertiary duct  304  splits into two quaternary ducts  312 , and each quaternary duct  312  is connected to a sixth water jacket  308  which is intended to fit around four piston cylinders. 
         [0044]      FIG. 6  shows a plan view of the third cooling system  301  in which the connection between the quaternary ducts  312  and the sixth water jacket  308  can be seen. Water flows in and out of the sixth water jacket  308  as indicated by the arrows  311  in  FIG. 6 . 
         [0045]    As with previous embodiments, the quaternary ducts  312  are connected to the bottom of the sixth water jacket  308  to reduce thermal syphoning. The third tertiary duct  304  is also arranged at an acute angle to the second primary duct  302  in order to reduce water flow from the third primary duct  302  into the third tertiary duct  304 . 
         [0046]    In an embodiment, one of the quaternary ducts  312  may be sealed, so that no water may flow through it. Water can then still reach the sixth water jacket  308  through the open quaternary duct  312 , while the sealed quaternary duct  312  serves only to support the water cooling system by maintaining the spatial relationship between the sixth water jacket  308  and the ducts  302 ,  303 ,  304 ,  312 . 
         [0047]      FIG. 7  shows a fourth cooling system according to the invention  401 . Like components with the first cooling system  101  are numbered with like numerals, except in the four hundreds range rather than the one hundreds range. The fourth cooling system  401  operates in a similar way to the first cooling system  101 , with the same arrangement of ducts to conduct water into and out of water jackets  406 ,  408 . 
         [0048]    In extreme cold conditions, it can become very difficult to start an internal combustion engine. In particular, at - 40  degrees centigrade and below, a petrol engine may be unable to start. Therefore it can be helpful to provide further assistance to an engine in these conditions. 
         [0049]    The fourth cooling system  401  comprises a seventh water jacket  406  and an eighth water jacket  408 . The eighth water jacket  408  comprises a first compartment  413  and a second compartment  414 . The first and second compartments  413 ,  414  are joined by several capillaries  415 , such that fluid can flow between the first and second compartments by passing through the capillaries. When installed in an engine, the first compartment  413 , second compartment  414  and the capillaries  415  enclose a piston cylinder (not shown) as is described above with reference to  FIG. 1 . 
         [0050]    The fourth cooling system  401  further comprises a heating element  416 , which is located in the second compartment  414 . The heating element  416  comprises a conductor which, when provided with an electrical current, produces heat. The heating element  416  is electrically insulated from the fluids in the heating element  416  in order to prevent the element discharging into the cooling fluid inside the eighth water jacket  408 . 
         [0051]    At very low ambient temperatures such as - 40  degrees centigrade, therefore, the heating element  416  can be used to help heat fluid in the eighth water jacket  408 . The heated fluid then in turn heats the piston cylinder, and so assists the engine in starting. 
         [0052]    Fluid heated by the heating element  416  tends to rise as indicated by arrow  417 . The fluid heated by the heating element  416  can also flow from the second compartment  414  into the first compartment  413  through the capillaries  415  as indicated by the arrow  418 . However the small size of the capillaries  415  means that the transit of liquid between the two compartments is slow, especially when the valve  410  is closed so that there is no overall flow of fluid through the eighth water jacket  408 . Hence the heated fluid tends to accumulate at the top of the second compartment  414 , well away from the fourth tertiary duct  404 . This tends to reduce thermal syphoning of warm fluid out of the eighth water jacket  408 . As such the location of the fourth tertiary duct  404  again helps to maintain and increase the temperature of the piston cylinder as is discussed above with reference to other embodiments. 
         [0053]    Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. 
         [0054]    Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
         [0055]    Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.