Lubricating oil supply system for industrial engines
BACKGROUND OF THE INVENTION 
     The present invention relates to a lubricating oil supply system for industrial engines, which is capable of automatically supplying lubricating oil when the amount of lubricating oil becomes less than a predetermined level. 
     Generally, in an industrial engine, it is necessary to supply lubricating oil to a crankcase when the amount of the lubricating oil in the crankcase decreases below the predetermined level due to the consumption of lubricating oil with the operation of the engine. Accordingly, a system which can automatically supply lubricating oil has been employed for this purpose. For example, the assignee proposed in Japanese Utility Model Laid Open No. 55-130008 a lubricating oil supply system for an industrial engine in which pulsation of air pressure in the crankcase is used to vibrate a diaphragm for a pump when the amount of lubricating oil is less than a predetermined level and a necessary amount of lubricating oil is automatically supplied. However, in such a system, the amount of lubricating oil supplied to the crankcase fluctuates due to temperature variation of the oil which is caused by temperature fluctuations of the ambient air and the engine. Namely, at a low temperature, a long time is required to supply a necessary amount of lubricating oil due to an increase of the viscosity of the oil, while at high temperature an excessive amount of the oil is fed due to reduction of the viscosity. Further, such a system of the prior art does not provide any warning or alarm and does not stop the operation of the engine when the temperature of the oil or the diaphragm pump excessively lowers or rises. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a system which can ensure stable supply of lubricating oil and keep a constant oil level within a crankcase of an industrial engine without any influence of fluctuations in temperature of the oil and a diaphragm pump. 
     Another object of the invention is to provide a lubricating oil supply system for industrial engines which can prevent trouble of the industrial engine by providing a warning system or by stopping the operation of the engine when the temperature of the oil or the diaphragm pump lowers or rises excessively. 
     The present invention provides a lubricating oil supply system for industrial engines which can supply the lubricating oil into a crankcase by effecting pulsation of air pressure in the crankcase on a diaphragm pump when the level of the oil in the crankcase becomes lower than a predetermined level, wherein a temperature-sensitive control member such as a bimetallic strip is provided for varying the cross-sectional area of a lubricating oil passage for the diaphragm pump, thereby controlling the flow rate of the oil to a constant value. 
     In the system according to the invention, since a temperature-sensitive control member capable of changing the cross-sectional area of a lubricating oil passage is provided, when the temperature of the oil or the pump which depends on the temperature of the ambient air or the engine lowers or rises, the cross-sectional area of the oil passage is increased or reduced, so that the flow rate of the oil can be kept constant without any influence of the fluctuation of the viscosity of the lubricating oil. 
     Further, when the temperature of the lubricating oil or the diaphragm pump excessively lowers or rises, the control member operates to close an electric circuit, so as to give a warning or to stop the operation of the engine and thus trouble of the engine may be prevented. 
    
    
     The above and other objects and features of this invention will become understood from the following description with reference to the accompanying drawings. 
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 shows a lubricating oil supply system of the invention, partially in cross section; 
     FIG. 2 is a sectional view taken along the line A--A of FIG. 1; 
     FIG. 3 is a sectional view taken along the line B--B of FIG. 1; 
     FIG. 4 is a circuit of a warning lamp; and 
     FIG. 5 is a circuit for stopping an engine. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, an industrial engine E is provided with a crankcase 1, an auxiliary lubricating oil tank 2 and a diaphragm pump 3. The pump 3 has a diaphragm actuating chamber 5 and a pumping chamber 6 defined by a diaphragm 4. The pump 3 comprises a check valve 7 disposed in the suction side, a check valve 8 placed in the discharge side, an inlet port 9, an outlet port 10 of pump chamber 6, and an intermediate chamber 6a. The diaphragm 4 is held by a coil springs 11a on a plate 5a, and connected to a piston 8a of the check valve 8 by an annular plate 8b having holes 8c. A spring 11 is disposed between the plate 8b and a body of the pump. 
     The piston 8a has an axial passage 8d and passages 8e communicated with the passage 8d, and an O-ring 12 is provided between flanges 8f and 8g and slidably enaged with the inside wall of the chamber 6a. The chamber 5 is communicated with a port 13 through holes 5b formed in the plate 5a. The port 13 is further communicated with an oil level detecting and pulsation introducing pipe 17. The height of the lower end of pipe 17 can be adjusted by a screw 18 having a scale 19. The outlet port 10 is communicated with an oil supply nozzle 14 in the crankcase 1, and the inlet port 9 is communicated with the auxiliary oil tank 2. The bottom portion of the crankcase 1 forms an oil pan 15 and the lubricating oil is stored in the oil pan 15. The end of the pipe 17 is opened at a position slightly higher than a predetermined oil level 16 which is the required lowest oil level. On the other hand, an oil passage 20 has an expanded chamber portion 20a formed between the check valve 7 and the inlet port 9, in which a bimetallic strip 21 is cantilevered on the wall of the passage 20 so as to project into the oil passage 20. The bimetallic strip 21 is arranged to bend toward an inside wall 20b so as to reduce the cross-sectional area of the oil passage 20 as shown by broken line 21a in FIG. 1, when the temperature of the lubricating oil or the diaphragm pump 3 is elevated. To the contrary, the bimetallic strip bends toward the other inside wall so as to increase the cross-sectional area when the temperature of the oil or the pump is lowered. 
     A fixed contact 23 for the higher temperature and a contact 24 for the lower temperature are attached on corresponding positions of the inside wall of the oil passage 20, so that an end 21a of the bimetallic strip 21 engages with one of the contacts. As shown in FIG. 4, the contacts 23 and 24 are connected to a battery 27 through leads 25 and 26, and the battery 27 is connected to the strip 21 through a warning lamp 28 and a lead 22. 
     In operation, when the oil level 16 in the crankcase 1 becomes lower than the predetermined level, which is the level of the end opening of the detecting pipe 17, the pipe 17 is communicated with the space above the oil. Thus, pulsations of pressure in the crankcase 1, which are caused by the reciprocation of the piston of the engine, is transmitted to the diaphragm actuating chamber 5 of the pump 3 to vibrate the diaphragm 4, so that the check valves 7, 8 operate to supply the lubricating oil from the auxiliary oil tank 2 to the crankcase 1. The operation of check valves 7, 8 is as follows. 
     When the piston 8a lowers, the flange 8f engages with the O-ring 12 to lower it. Accordingly, the pressure in the chamber 6a reduces, so that the check valve 7 opens to induce the oil into the chamber 6a from the tank 2. When the piston 8a rises, the flange 8f disengages from the O-ring 12 and the flange 8g engages with the O-ring 12 to raise it. As a result, a passage is formed between the flange 8f and the O-ring 12. Thus, the oil in the chamber 6a flows into the passage and the passages 8e and 8d and flows in the crankcase 1 through holes 8c and chamber 6. 
     When the oil level in the crankcase 1 becomes higher than the end of the pipe 17, the opening of the pipe 17 is closed by the oil so that the operation of the diaphragm pump 3 stops. 
     If the height of the end opening of the pipe 17 is changed by adjusting the screw 18, the level of the oil changes in accordance with the positions of the opening of the pipe 17. Accordingly, the pipe 17, screw 18 and scale 19 serve as an oil level gauge. 
     When the temperature of the lubricating oil or the diaphragm pump 3 lowers, the cross-sectional area of oil passage is increased by the bending of the bimetallic strip 21, and when the temperature rises, the cross-sectional area is reduced by the bending of the strip 21 in the opposite direction. Thus, the lubricating oil is supplied at a constant flow rate irrespective of a change of the viscosity of the oil. Further, when the temperature of the lubricating oil or the diaphragm pump 3 lowers or rises to a large extent, the bimetallic strip 21 engages with the contact 24 for the lower temperature or with the contact 23 for the higher temperature to close the circuit and to light warning lamp 28. 
     In the above embodiment, although two pipes 10, 14, 13, 17 are provided for supplying oil and for inducing pressure pulsations, it is possible to provide only one pipe which serves as an oil supply and pulsation inducing pipe. 
     FIG. 5 is a circuit for stopping the engine at abnormal temperatures. In the embodiment of the invention, leads 25, 26 of the contacts 23, 24 are coupled together with a primary winding of a magneto igniting device 31 for a spark plug 32. 
     In such a construction of this embodiment, when the temperature of the oil or diaphragm pump becomes extremely high or low and the strip 21 engages with the contact 23 or 24, the primary winding of the magneto igniting device 31 is grounded, so that the operation of the engine stops. 
     While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.