Distributor-type fuel injection pump governor
BACKGROUND OF THE INVENTION 
     This invention relates in general to distributor-type fuel injection pumps for compression ignition internal combustion engines or Diesel engines and more particularly to governors of such fuel injection pumps. 
     In FIG. 1, there is shown a prior art distributor-type fuel injection pump for a compression ignition multi-cylinder internal combustion engine. 
     The prior art distributor-type fuel injection pump comprises a pump housing 1 having an inner chamber 1a which is charged with fuel by a fuel supply pump (not shown). To the pump housing 1 there is fixedly attached a plunger barrel 2 in which is mounted a distributor plunger 3. The distributor plunger 3 is powered by engine-driven power transmitting means (not shown) and reciprocates while rotating to effect pumping and distributing actions. 
     During the suction stroke or leftward stroke of the distributor plunger 3, fuel is drawn from the inner chamber 1a through an inlet channel 4 and longitudinal grooves 5 provided in the outer face of a terminal portion of the distributor plunger 3 to a pump work chamber 6 which is adjoined by the distributor plunger 3. During the pressure stroke or rightward stroke of the distributor plunger 3, fuel under pressure is delivered from the pump work chamber 6 through a distributor channel 7 to one of outlet channels (only one is shown). Therefrom fuel is delivered through the associated one of delivery valves 9 to one of injection nozzles (not shown). In this manner, fuel is sequentially injected into the cylinders of the engine. 
     In the distributor plunger 3 there is provided a transverse channel or relief channel 10 which cooperates with a control sleeve 11. The control sleeve 11 is axially displaceable on the distributor plunger 3 to seal and unseal the mouths of the relief channel 10 in the outer surface of the distributor plunger 3. When the control sleeve 11 unseals or uncovers the mouths of the relief channel 10, the pump work chamber 6 is drained into the inner chamber 1a of the pump housing 1 to terminate the fuel delivery to the injection nozzles. Hence it is possible to alter the terminal moment of fuel delivery during each pressure stroke of the distributor plunger 3 and therefore the quantity of fuel delivered to the engine by changing the position of the control sleeve 11. For example, leftward displacement of the control sleeve 11 in the drawing results in reduced injected fuel quantity. 
     The axial position of the control sleeve 11 is controlled by a governor mechanism which comprises a governor shaft 12 which is fixedly attached to the pump housing 1. On the governor shaft 12 there is rotatably mounted a centrifugal weight holder 13. The holder 13 is powered by the aforementioned power transmitting means (not shown) for the distributor plunger 3 by way of a multiplying gear (also not shown). On the centrifugal weight holder 13, centrifugal weights 14 are supported and rotated about the governor shaft 12 and swing outwardly due to centrifugal force. As the weights swing outwardly, fingers 14a axially displace a governor sleeve 15on the governor shaft 12, in the rightward direction in the drawing. The governor sleeve 15 abuttingly engages at the left-hand end thereof with the upper arm portion of a starting lever 16 which is swingably supported on a pivot 17. The lower arm portion of the starting lever 16 has a spherical terminus 16a which extends into a depression of the control sleeve 11 for causing axial displacement of the control sleeve. On the pivot 17 there is also swingably supported a tensioning lever 18. Between the tensioning lever 18 and the starting lever 16 there is interposed a starting spring or an excess fuel spring 19 in the form of a leaf spring. The tensioning lever 18 is operatively connected through an idle spring 20, a governor main spring 21 and a control lever 22 to an accelerator pedal (not shown). Stopper 23 limits the extent of counter-clockwise swing of the tension lever 18. 
     The operation of the governor mechanism thus described will be explained hereinbelow with additional reference to FIG. 2. 
     When the engine is stopped and therefore the centrifugal weights 14 are motionless, the centrifugal weights 14 assume the completely closed condition due to the bias of the starting spring 19 transmitted thereto by way of the starting lever 16 and at the same time control sleeve 11 is moved into the starting position or the most rightward position thereof (represented by the horizontal line A in the graph of FIG. 2) in the drawing (FIG. 1) whereby an excess fuel quantity required by the engine during starting is obtained. 
     When the engine starts and in the absence of depression on the accelerator pedal, the control lever 22 is put into the idle position and therefore the tension of the governor spring 21 reduces approximately to zero. The centrifugal weights 14 are thus permitted to swing outwardly even in the relatively low rotational conditions thereof which displaces the governor sleeve 15 rightwardly turning the starting lever 16 together with the tension lever 18 and compressing both the starting spring 19 and the idle spring 20, resulting in the movement of the control sleeve 11 leftwardly into the idle position which is determined by the balance of the centrifugal force and the biasing forces of the starting spring 19 and the idle spring 20. In this manner, the quantity of fuel necessary for smooth idling of the engine is obtained as represented by the point B in the graph of FIG. 2. 
     When the accelerator pedal is then depressed to move the control lever 22 to some extent, the tension of the governor main spring 21 becomes larger and consequently both the starting spring 19 and the idle spring 20 are compressed to be of shorter length permitting the tension lever 18 to swing counterclockwise until it abuttingly engages the stopper 23. Actuated by such swing of the tension lever 18, the starting lever 16 displaces the control sleeve 11 to the full load position as is represented by the point C in the graph of FIG. 2. The control sleeve 11 remains thereat permitting the engine speed to increase up to the value as is represented by the point D in the graph of FIG. 2 where the centrifugal weights 14 start to displace the governor sleeve 15 overcoming the counter force thereto. After that, the control sleeve 11 is displaced in the fuel-increasing direction, i.e., leftwardly to the position as represented by the point E in the graph of FIG. 2 which is determined by the balance of the centrifugal force of the centrifugal weights 14 and the biasing forces of the springs 19, 20 and 21. The engine speed is thus controlled with relation to the amount of depression on the accelerator pedal. 
     The pivot 17 is carried on a full load fuel quantity adjusting lever 24 which is pivotally supported on a stationary pivot 25. The adjusting lever 24 is normally held stationary but is caused to swing about the stationary pivot 25 by rotating a screw 26 to change the setting of the full load fuel quantity. A fuel-cut solenoid valve 27 is provided for stopping the engine. 
     The governor sleeve 15 has an inner space 30 which is adjoined by an end of the governor shaft 12 and which varies in volume in response axial displacement of the governor sleeve on the governor shaft. In order to draw fuel from the inner chamber 1a of the pump housing 1 into the inner space 30 and on the other hand to discharge fuel from the inner space 30 into the inner chamber 1a in response to the variation in volume of the inner space 30, there is provided in the governor sleeve 15 an opening P which provides communication between the inner space 30 and the inner chamber 1a. The flow passage sectional area of the opening P has heretofore been designated to be relatively large for the reason of good responsiveness. 
     Though the prior art distributor-type fuel injection pump with such a governor mechanism produces good results upon engine deceleration due to the good responsiveness, it tends to produce undesirable results upon rapid engine acceleration due to the good responsiveness. That is, upon rapid engine acceleration, the control lever 22 actuates, by means of the governor main spring 21, the starting lever 16 toether with the tension lever 18 to rapidly swing in the counterclockwise direction displacing the governor sleeve 15 leftwardly in the drawing. In response to such displacement of the governor sleeve 15, the control sleeve 11 is rapidly displaced rightwardly or in the fuel-increasing direction. As a result, the quantity of fuel delivered to the engine increases rapidly, resulting in an acceleration jerk which prevents good drivability and causes a smoky exhaust emission from the engine. This occurs because, at the initial stage of the rapid engine acceleration, the rate of engine air flow can not quickly increase so as to match the increased quantity of fuel delivered to the engine, that is, the increase in the rate of engine air flow lags behind the increase in the quantity of fuel delivered to the engine. 
     OBJECTS OF THE INVENTION 
     It is accordingly an object of the present invention to provide a distributor-type fuel injection pump with an improved governor mechanism which is free from the foregoing drawbacks inherent in the prior art comparable fuel injection pump. 
     It is another object of the present invention to provide a distributor-type fuel injection pump of the above described character which is constructed to prevent an acceleration jerk upon rapid engine acceleration. 
     It is a further object of the present invention to provide a distributor-type fuel injection pump of the above described character which is constructed to prevent smoky exhaust emission from a Diesel engine upon rapid engine acceleration. 
     It is a yet a further object of the present invention to provide a distributor-type fuel injection pump of the above described character which is constructed to prevent noxious exhaust emissions from the engine upon rapid engine acceleration. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a sectional view partly broken away showing a prior art distributor-type fuel injection pump with which the present invention is concerned; 
     FIG. 2 is a graph showing the operation characteristics of the governor mechanism of the fuel injection pump of FIG. 1; 
     FIG. 3A is a fragmentary sectional view showing part of a governor mechanism of a distributor-type fuel injection pump embodying the present invention; 
     FIG. 3B is a cross sectional view taken approximately along line L--L of FIG. 3A; 
     FIG. 4 is a view similar to FIG. 3A but showing another embodiment of the invention; and 
     FIG. 5 is a view similar to FIGS. 3A and 4 but showing a further embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 3A and 3B, part of a governor mechanism according to one embodiment of this invention is shown. The omitted part of the governor mechanism is substantially similar to the prior art governor mechanism of FIG.1. A governor shaft 31 has a reduced diameter neck section 31a which is located approximately at the middle of the governor sleeve carrying portion thereof. A governor sleeve 32 is rotatably and axially displaceably carried on the governor shaft 31 and cooperates with the neck section 31a to define therebetween an annular space 33. The governor sleeve also has an inner space 34 which is adjoined by an end of the governor shaft 31. The governor shaft 31 is formed with a groove 31b in the outer cylindrical surface of the end section thereof between the inner space 34 and the neck section 31a. The groove 31b is a helical groove of the kind that recedes from an observer while twisting in the direction opposite to the rotational direction of the governor sleeve 32 which is observed from the end thereof nearer to the inner space 34. That is, in the case where the governor sleeve 32 is adapted to rotate counterclockwise when viewed from the righthand side thereof in the drawing, the groove 31b is formed into a right-handed helical shape. 
     The governor sleeve 32 is formed with a first radial opening 32a which provides communication between the annular space 33 and the inner chamber 1a of the pump housing 1 (FIG. 1) and a second radial opening 32b which provides communication between the inner space 34 and the inner chamber 1a. The second opening 32b has a flow passage cross sectional area smaller than that of the first opening 32a. 
     The operation of the distributor-type fuel injection pump with an improved governor mechanism thus described according to the present invention will be explained hereinbelow. 
     When the governor sleeve 32 is axially stationary while rotating on the governor shaft 31, such circulation of fuel occurs that a portion of the fuel contained in the inner chamber 1a of the pump housing flows through the opening 32a into the annular space 33 and therefrom through the helical groove 31b, the inner space 34 and the opening 32b, in sequence, back to the inner chamber 1a. This is due to the provision of the helical groove 31b, that is, the helical groove 31b effects a forced fuel conveying action of forceably, though yeildingly, conveying fuel from the annular space 33 to the inner space 34 upon rotation of the governor sleeve 32. 
     Upon engine acceleration, the governor sleeve 32 is actuated by the tension lever 18 and the starting lever 16 to be displaced leftwardly in the drawing. In this instance, as the governor sleeve 32 is increasingly displaced in the leftward direction, a quantity of fuel contained in the inner space 34 increasingly flows out therefrom through the opening 32b and the flow path comprised of the groove 31b, the annular space 33 and the opening 32a. However, since such outflow of fuel from the inner space 34 is restricted or limited by the forced fuel conveying action of the groove 31b and the opening 32b of a relatively small flow passage cross sectional area, the governor sleeve is displaced relatively slowly or insensitively in the leftward direction to increase the quantity of fuel to the engine for injection. 
     Upon engine deceleration, the centrifugal weights 14 are swung outwardly causing the governor sleeve 32 to be displaced rightwardly in the drawing. In this instance, as the governor sleeve 32 is increasingly displaced rightwardly, a portion of the fuel contained in the inner chamber 1a increasingly flows into the inner space 34 through the opening 32b and the flow path comprised of the opening 32a, the annular space 33 and the groove 31b. In this instance, since an increased quantity of fuel flows into the inner space 34 for a given time due to the forced fuel conveying action of the helical groove 31b, the governor sleeve 32 is displaced quite quickly or sensitively in the rightward direction to increase the quantity of fuel to the engine for injection. 
     By foregoing, there has been provided a distributor-type fuel injection pump with an improved governor mechanism which relatively quickly responds to the demand for engine deceleration and which responds relatively slowly to the demand for engine acceleration, preventing an acceleration jerk and a smoky exhaust. 
     Referring to FIG. 4, wherein another embodiment of the invention is shown, it will be seen that a governor shaft 41 has a governor sleeve carrying portion of a substantially uniform cross section and a helical groove 41a which is formed in the outer cylindrical surface of the governor sleeve carrying portion. The helical groove 41a is of such length as to extend throughout the axial length of the governor sleeve carrying portion and have an exposed end which opens into the inner chamber 1a of the pump housing 1. A governor sleeve 42 is formed with an opening 42a which provides communication between the inner space 43 and the inner chamber 1a. The other structure of this embodiment is identical with that described in conjunction with FIGS. 3A and 3B. 
     With this FIG. 4 arrangement, since opening 32a and neck section 31a which were required in the FIG. 3 embodiment can be dispensed with, a simplified structure of a governor mechanism results. Otherwise, the action is identical with that described in conjunction with FIGS. 3A and 3B. 
     As an alternative to forming the helical groove in the outer cylindrical surface of the governor shaft as in the previous embodiments, the helical groove may be formed in the inner cylindrical surface of the governor sleeve as shown in FIG. 5. In the embodiment of FIG. 5, a governor sleeve 51 has a helical groove 51a which is formed in the inner cylindrical surface thereof for sliding engagement with a governor shaft and which extends nearly throughout the axial length of the inner cylindrical surface so as to open at the opposite ends thereof into the inner chamber 1a and an inner space 52 defined within the governor sleeve, respectively. Unlike the previous embodiments, the helical groove 51a in this case is of the kind that recedes from an observer while twisting in the direction corresponding to the rotational direction of the governor sleeve 51 which is observed from the end thereof nearer to the inner space 52. That is, in the case where the governor sleeve 51 is adapted to rotate counterclockwise when viewed form the right-hand side thereof in the drawing, the helical groove 51a is formed into a left-handed helical shape. The governor sleeve 51 is also formed with an opening 51b providing communication between the inner space 52 and the inner chamber 1a. 
     This embodiment of FIG. 5 produces substantially the same effect as the previous embodiments. 
     In each foregoing embodiment, it will be understood that a desired response characteristic of the governor mechanism is obtained by suitably determining the flow passage cross sectional area and the helical form of the groove 31b, 41a or 51a and/or by determining the bore size of the opening 32b, 42a or 51b. 
     By the foregoing, there has been provided an improved governor mechanism of a distributor-type fuel injection pump calculated to fulfill the objects hereinabove set forth and while preferred embodiments have been illustrated and described in detail hereinabove, various additions, substitutions, modifications and ommissions may be made thereto without departing from the spirit of the invention as encompassed by the appended claims.