Abstract:
In an internal combustion engine, a large volume of lubricant is desirable to increase service intervals and thus reduce maintenance costs. Large lubricant volumes typically require an undesirable increase in engine size. A cylinder block assembly for an internal combustion engine in accordance with this invention comprises a cylinder block, a primary lubricant reservoir or sump below the cylinder block, and a secondary lubricant reservoir at a side of the cylinder block. The secondary lubricant reservoir may be formed as a pannier oil tank by sealably attaching an apron to a side of the cylinder block. A fluid passage extending between the secondary lubricant reservoir and the primary lubricant reservoir is closeable by a valve and is adapted to permit lubricant flow from the secondary lubricant reservoir to the primary lubricant reservoir when open. The secondary lubricant reservoir increases the oil capacity of the cylinder block.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to a cylinder block assembly for an engine having an increased lubricant capacity and in particular to a cylinder block assembly in which the volume and flow rate of lubricant within the engine is controlled. The invention also relates to a method of lubricating an engine.  
         BACKGROUND  
         [0002]    During operation of an engine, a lubricant such as engine oil is pumped from a sump into the working portions of an engine in order to lubricate, clean and cool the engine&#39;s moving parts. Excess oil supplied to the moving parts is drained back to the sump along various paths defined in the engine cylinder block and cylinder head.  
           [0003]    A large volume of lubricating oil is desirable in an engine. For example, where the volume of engine oil is increased, service intervals can be increased thereby minimizing maintenance costs. However, the volume of oil that can be employed in an engine is limited by engine size as, in general, it is desirable to maintain engine size at a minimum while large volumes of oil require large storage reservoirs in an engine.  
           [0004]    UK Patent specification No 100,345 describes a lubricating system for a car engine comprising a circulating oil tank located beneath a cylinder block of the engine, and a fresh oil tank formed in the side of the block. Filling of the fresh oil tank results in overflow oil passing through a weir to the circulating oil tank. The system includes a first pump to pump oil from the circulating oil tank to the oil circulation system and a second pump which supplies oil from the fresh oil tank to the oil circulation system. While the fresh oil tank provides an extra volume of oil for the engine, the means for supplying the fresh oil to the circulation system necessitates the use of a pump in the supply line as the disposition of the line is such that oil will not flow to the circulating system when the line is open. Moreover, in order for fresh oil to be supplied to the oil circulation system, both pumps need to operate at the same time. These shortcomings result in a lubricating system which is more expensive to manufacture and operate. The present invention sets out to overcome one or more of the disadvantages of the prior art.  
         SUMMARY OF THE INVENTION  
         [0005]    According to the invention there is provided a cylinder block assembly comprising a cylinder block, a primary lubricant reservoir below the cylinder block, a secondary lubricant reservoir at a side of the cylinder block, a fluid passage extending between the primary and secondary lubricant reservoirs, and a valve which can be actuated to open and close the fluid passage, wherein the fluid passage is adapted to permit gravitational flow of the lubricant from the secondary lubricant reservoir to the primary lubricant reservoir when open, wherein actuation of the valve is controlled by a level of lubricant in the primary lubricant reservoir.  
           [0006]    The invention also extends to an engine having such a cylinder block assembly.  
           [0007]    The invention also extends to a method for lubricating an engine comprising the steps of:  
           [0008]    pumping lubricant around the engine from the primary lubricant reservoir;  
           [0009]    collecting a proportion of returned lubricant in the secondary lubricant reservoir; and  
           [0010]    controlling the return of lubricant from the secondary lubricant reservoir through the fluid passage to the primary lubricant reservoir by means of the valve. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    Various embodiments of the invention will now be described, by way of example only, having regard to the accompanying diagrammatic drawings in which:  
         [0012]    [0012]FIG. 1 a  is a partial transverse cross section through a cylinder block assembly according to one embodiment of the invention, including a cylinder block provided with a secondary lubricant reservoir at a side wall thereof, the cylinder block also being provided with a primary lubricant reservoir and a cylinder head; and  
         [0013]    [0013]FIG. 1 b  is a partial transverse cross section through a cylinder block assembly according to another embodiment of the invention, including a cylinder block provided with a secondary lubricant reservoir at a side wall thereof in which the pannier oil tank is defined by the cylinder block and a cylinder block apron. 
     
    
     DETAILED DESCRIPTION  
       [0014]    A cylinder block  1  is provided with at least one secondary lubricant reservoir which acts as an engine oil capacitor to increase engine lubricating oil capacity. In the present example, the secondary lubricant reservoir takes the form of a pannier oil tank  11 ; however the secondary lubricant reservoir can be of any construction that may be adapted by a skilled person in accordance with the present invention.  
         [0015]    In FIG. 1 a , the pannier oil tank  11  is integrally formed in the cylinder block  1  while in FIG. 1 b  the pannier oil tank  11  is defined between the cylinder block  1  and a cylinder block apron  2 . The illustrated embodiments are described in more detail below, but it is to be understood that the form and construction of the pannier oil tank may be varied in accordance with the present invention.  
         [0016]    As shown in FIG. 1 a , the cylinder block  1  is a casting made up of a cylinder block body  4  and a cylinder block base  5 . Two cylinder block side walls  35  and two cylinder block end walls  36  upstand from the cylinder block base  5  (only one side wall  35  and end wall  36  is shown). The cylinder block  1  is provided with a primary oil reservoir in the form of a sump  37  attached to the cylinder block base  5 . The cylinder block  1  has a cylinder head  8  fitted with a cylinder head cover  9 .  
         [0017]    The side walls  35  are shaped to define a crankcase housing  7  of a crankcase  6  adjacent the cylinder block base  5 . A crankshaft  10  is contained within the crankcase  6 .  
         [0018]    The side wall  35  of the cylinder block  1  is formed to define the pannier oil tank  11  between a side wall outer wall  12  and a side wall inner wall  13  adjacent the cylinder block base  5 . The pannier oil tank  11  is further defined by a bottom wall  14  at the cylinder block base  5 . A bottom wall valve opening  15  in the bottom wall  14  provides a fluid passage  38  between the pannier oil tank  11  and the sump  37 . The pannier oil tank  11  is open at a top end  34 . The bottom wall  14  may be formed as a separate plate to facilitate core sand removal from the pannier oil tank  11  where the pannier oil tank  11  is cast integrally with the cylinder block  1 .  
         [0019]    The pannier oil tank  11  is adapted to store lubricating oil  16  or other lubricant. The bottom wall valve opening  15  is openable and closeable by a float valve  17  located in the sump  37 . The float valve  17  is of substantially conventional construction and is provided with a valve head  18  moveable between an open position to allow drainage of oil  16  from the pannier oil tank  11  through the fluid passage  38  and into the sump  37 , and a closed position to allow filling of the pannier oil tank  11  in accordance with oil levels in the sump  37 . The bottom wall valve opening  15  is dimensioned to allow relatively brisk oil flow in the open position. As the lubricant level in the sump  37  increases, the valve  17  closes the aperture  15  when the level of the lubricant  16  reaches a predetermined level.  
         [0020]    At its open top end  34 , the pannier oil tank  11  is adapted to receive lubricating oil  16  through a filler tube  19  defined in the side wall outer wall  12 . Whilst the float valve  17  is in the open position, oil received via the filler tube  19  will pass through the pannier oil tank  11  and through the valve opening  15  into the sump  37 . When the oil level in the sump  37  has reached a predetermined design level, the float valve  17  will close the valve opening  15  and the pannier oil tank  11  will commence to fill.  
         [0021]    A conventional dipstick (not shown) or sight glass  40  is used in conjunction with the pannier oil tank  11  to determine when the design quantity of oil has been reached. It is envisaged that the maximum oil level of the engine will be at or just below the open top end  34  of the filler tube  19 .  
         [0022]    When the engine is in operation, oil is received in the pannier oil tank  11  from a cylinder block duct  21  which extends between the cylinder head  8  and the pannier oil tank  11  via a cavity  20 . The cylinder block duct  21  is located in the cylinder block side wall  35 .  
         [0023]    The apparatus may be configured such that the pannier oil tank  11  is the prime recipient of oil from the various oil return sources in an engine. Those sources may include, for example, a pressure relief valve  24 , shown in FIG. 1 b , that may be required to relieve oil pressure in the lubricating oil circuit of the engine, particularly at low engine speeds.  
         [0024]    It may be found desirable to include, in an engine, more than one float valve  17  or even a series of float valves  17 , to cater for the variable engine inclinations that the engine may experience in use. The speed of oil drain from the pannier oil tank  11  into the sump  37  that may be required in use or in service may also influence the number and location of float valves  17 .  
         [0025]    The side wall inner wall  13  is provided with an aperture  32  located at the top end  34  of the pannier oil tank  11 . The aperture  32  serves as an overflow for the pannier oil tank  11  so that oil can flow from the pannier oil tank  11 , through the aperture  32 , into the sump  37  when the capacity of the pannier oil tank  11  is exceeded.  
         [0026]    [0026]FIG. 1 b  shows an engine including a cylinder block  1  with a pannier oil tank  11  in accordance with a second embodiment of the invention. The cylinder block  1  of FIG. 1 b  is broadly similar to the cylinder block  1  of FIG. 1 a . Accordingly, like numerals indicate like parts. However, in the present embodiment, the pannier oil tank  11  is defined by an apron  2  and the cylinder block side wall  35 . More particularly, the pannier oil tank  11  is defined between the crankcase housing  7  and the apron  2 .  
         [0027]    The apron  2  is sealably adhered to the side wall  35  to define the pannier oil tank  11 . Briefly, the apron  2  is made up of an apron bottom portion  26 , an apron cylinder block portion  27  and an apron cylinder head portion  28  attachable to the cylinder head  8 . The apron  2  is formed from a metal sheet or other suitable material and is shaped and contoured to complement the side wall  35  of the cylinder block  1 . Advantage is thus taken of a natural cavity that exists in the necked region of a conventional crankcase to define, with apron  2 , a pannier oil tank  11 .  
         [0028]    The apron  2  is folded at the bottom portion  26  to define an elongate box-like beam  30  for reinforcing the apron  2  and the cylinder block  1  to which the apron  2  is adhered. The beam  30  is secured to a cylinder block flange  31  defined at the cylinder block base  5 .  
         [0029]    The apron  2  may be provided with cooling elements  33  on its outer surface in the region of the pannier oil tank  11  to facilitate cooling of oil  16  contained within the pannier oil tank  11 . The pannier oil tank  11  of FIG. 1 b  is also provided with a bottom wall  14 . However, in the present embodiment, the bottom wall  14  is formed by the cylinder block base  5 .  
         [0030]    Accordingly, the bottom wall valve opening  15  of the pannier oil tank  11  and the fluid passage  38  of FIG. 1 b  are defined in the cylinder block base  5 . The bottom wall valve opening  15  is also openable and closeable by a float valve  17  in the sump  37 .  
         [0031]    The pannier oil tank  11  of FIG. 1 b , like pannier oil tank  11  of FIG. 1 a  is adapted to receive oil from a filler tube (not shown) and the cylinder block duct  21  in communication with the cylinder head  8  via the cavity  20  defined between the apron  2  and the cylinder block  1 . In the embodiments of both FIGS. 1 a  and  1   b  the cylinder block duct  21  is in communication with the interior of the cylinder head cover  9  via cylinder head ducts  29  provided in the cylinder head  8  itself. The pannier oil tank  11  can also receive oil from miscellaneous sources as described in relation to FIG. 1 a.    
         [0032]    The aperture  32  in the crankcase housing  7  also functions to receive crankcase gases from the crankcase  6 .  
         [0033]    Both embodiments of the invention are provided with a sump oil pick up  22  located in the sump  37  and an oil pump  23 , also housed in the sump  37 , for pumping oil from the sump  37  to the crankshaft  10 . Oil is directed to the crankshaft  10  by a crankshaft oil feed  25  in communication with the oil pump  23  while the pressure relief oil valve  24  is disposed between the pannier oil tank  11  and the crankshaft oil feed  25 . An oil spray (not shown) in communication with the oil pump  23  can also be provided to assist in piston cooling and lubrication of piston pins and rings and the cylinder block side and end walls  35 ,  36  respectively.  
         [0034]    The lubricating oil is filtered by an oil filter (not shown) to clean the oil and remove debris therefrom in conventional manner.  
       INDUSTRIAL APPLICABILITY  
       [0035]    The pannier oil tanks  11  of FIGS. 1 a  and  1   b  operate in a similar manner and operation and use of the invention will now be described in relation to a typical six cylinder 6.0 liter engine having a pannier oil tank  11  on each cylinder block side wall  35 . However, it will be appreciated by those skilled in the art that the invention finds application in engines having different numbers of cylinders and different capacities while engines can be provided with one, two or more pannier oil tanks  11  as required.  
         [0036]    Lubrication oil  16  from engine main and big end bearings and from piston cooling jets and the like is returned to the sump  37  in a substantially conventional manner.  
         [0037]    Other oil flow from the cylinder head  8 , pressure relief valves  24  and engine components including turbo-chargers, camshafts, idler shaft bearings and the like may be returned first to the pannier oil tanks  11  via the cylinder block ducts  21  and the cylinder head ducts  29 .  
         [0038]    In the 6.0 liter engine of the present example, the sump  37  is adapted to receive ten liters of oil while the pannier oil tanks  11  are dimensioned to receive six liters of oil before overflowing into the sump  37  through the aperture  32 . Maximum oil flow from the pannier oil tanks  11  via bottom wall valve openings  15  is restricted to six or less liters per minute.  
         [0039]    The fluid passage  38  is disposed such that, when open, oil flows under the force of gravity from the pannier oil tank  11  to the sump  37  without the need for an additional pump.  
         [0040]    The float valve  17  is set at a level such that the bottom wall valve opening  15  is open under least favorable operating conditions when oil levels in the sump  37  are at their lowest levels, due to the high volume of oil  16  in circulation in an engine. Accordingly, the float valve  17  is closed under most operating conditions.  
         [0041]    As indicated above, the initial volume of oil is fed, prior to engine start-up, into the pannier oil tank  11  via the filler tube  19 . When the oil level in the pannier oil tank reaches the aperture  32  the additional fed oil overflows through the aperture into the sump  37 .  
         [0042]    At engine start-up, the pannier oil tanks  11  are full under normal conditions. The float valves  17  are closed due to the high oil level in the sump  37 .  
         [0043]    Accordingly, upon engine start up, oil levels in the sump  37  are lowered as oil is pumped around the engine components, enabling the float valve  17  to open to a limited extent.  
         [0044]    At idle speed oil will circulate at a rate which returns 18 liters of oil per minute to the sump  37  and 6.5 liters of oil per minute to the pannier oil tanks  11 . If the float valves  17  are closed, and the pannier oil tanks are full, then the 6.5 liters of oil per minute returned to the pannier oil tanks will overflow through the aperture  32  and return to the sump  37 . However, under abnormal conditions where the float valves  17  are open, then assuming the float valves  17  are fully opened and sized to permit a flow of 6 liters of oil per minute, the pannier oil tanks  11  are filled approximately 12 minutes after start up, based on a net flow of 0.5 liters of oil per minute into the pannier oil tanks.  
         [0045]    In practice, the float valves  17  are generally completely shut due to high oil levels  16  in the sump  37  so that the pannier oil tanks  11  fill at a faster rate.  
         [0046]    At most engine operating regimes, flow rate of oil returned to the pannier oil tanks  11  greatly exceeds flow rate from the pannier oil tanks  11 . Flow rates are calibrated such that, at idle speeds, oil in circulation is insufficient to allow oil levels in the sump  37  to depress to the point where the valves  17  will open. As previously described, any overflow from the pannier oil tanks  11  through the apertures  32  simply enters circulation in the engine. At running speeds, oil levels in the sump  37  are further depressed due to the increased volume of oil in circulation whereby the float valves  17  may open. Opening of the float valves  17  in such a manner therefore results in a stabilization of oil levels in the pannier oil tanks  11  at a level proportionate to return flow of the oil  16 .  
         [0047]    Oil within the pannier oil tanks  11  is also cooled in the embodiment described in FIG. 1 b  due to the cooling elements  33 .  
         [0048]    In short, oil level within the sump  37  is regulated to be at a correct level in accordance with engine requirements at all times due to the presence of the pannier oil tanks  11  and the co-operation of the bottom wall valve openings  15  and float valves  17 .  
         [0049]    Table  1  below summarizes the above described oil flows in an engine:  
                                                               TABLE 1                           Typical Oil Flows                    Peak Torque/               Idle   Cruise   Rated Speed           Litre/min %   Litre/min %   Litre/min %                        Speed - rpm   700       1500       2200           Bearings   17       32       47       Cooling Jet   1       8       13       Return to sump   18   73%   40   44.1%   60   47.3%       Turbo   3       4.2       4.5       Relief valve   0       30       40       Head/valve gear   1       2       2       Bypass filter   1       8       11.5       Miscellaneous   1.5       6.4       8.7       Return to pannier   6.5   27%   50.6   55.9%   66.7   52.7%       oil tanks (11)           Total flow   24.5   100%    90.6    100%   126.7    100%                  
 
         [0050]    As indicated above, where the engine is running the volume of oil  16  in circulation results in oil levels in the sump  37  being lowered so that the float valves  17  are partially opened. However, when the engine is stopped, oil in circulation within the engine is returned to the sump  37  and the pannier oil tanks  11  in proportions relative to the engine operating speed immediately prior to shut down. The float valves  17  remain open until the sump  37  is at least partially filed with oil  16 . In practice, return of oil  16  to the sump  37  occurs in advance of return of oil  16  to the pannier oil tanks  11  due to longer return paths from pannier oil tank filling sources, such as the cylinder head  8 . When the float valves  17  are closed, the oil level in the sump  37  continues to rise to a normal level due to the large volume of sump return oil  16  in circulation.  
         [0051]    When servicing the engine, oil drain may be achieved through a sump plug or a suction tube into the sump  37 . At a critical drainage level, the float valves  17  are opened thereby permitting the pannier oil tanks  11  also to drain.  
         [0052]    On refilling, the pannier oil tanks  11  are filled through the filler tube  19  and hence the sump  37  becomes filled via the bottom wall valve opening  15 . If an excessive filling rate is used, the oil tank panniers  11  simply overflow into the sump  37  via the apertures  32  as previously described.  
         [0053]    The invention finds application in engines where it is desired to incorporate an oil capacitor to supplement the oil sump without detriment to engine servicing efficiency and without compromising oil cleanliness and durability within the engine during operation.  
         [0054]    The invention is not limited to the embodiments herein before described which may be varied in both construction and detail.