Fuel pump drive system

Information

  • Patent Grant
  • 6786206
  • Patent Number
    6,786,206
  • Date Filed
    Wednesday, March 5, 2003
    21 years ago
  • Date Issued
    Tuesday, September 7, 2004
    20 years ago
Abstract
Disclosed is a fuel pump drive system which can change revolution ratio of an engine to a fuel pump to one-to-one without vast increase in cost, allowing the fuel pump to be smaller-sized fuel pump. The system has a conventional flywheel housing with a gear through hole opened to a gear train accommodation space and adapted to receive a conventional input gear as an element of a gear train for transmission of the torque to the fuel pump through meshing with an output gear with revolution ratio of the engine to the fuel pump being two-to-one, an air compressor gear (new input gear) for transmission of the torque to the fuel pump through meshing with a smaller main idle (output gear) via an idle gear within a range of the gear through hole with revolution ratio of the engine to the fuel pump being changed to one-to-one, and an adapter interposed between the flywheel housing and the fuel pump for rotatably supporting the idle gear in a position for meshing with the air compressor gear.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a fuel pump drive system.




2. Description of the Related Art




A common rail type fuel injection system for injection of fuel to an engine has been known as a system which can enhance an injection pressure and which optimally controls injection conditions such as fuel injection rate and timings depending upon operational status of the engine.





FIG. 1

is a block diagram typically and schematically showing such common rail type fuel injection system in which fuel in a fuel tank


1


is pressurized by a fuel pump


2


in the form of for example a plunger type variable displacement high-pressure pump.




This fuel pump


2


is driven by an engine output to pressurize the fuel into a required pressure and deliver the same via a fuel conduit


3


to a common rail


4


where the fuel is accumulated in pressurized state.




The fuel pump


2


is provided with a valve means


5


which controls fuel discharge rate to maintain the fuel in the common rail


4


to a predetermined pressure. Relieved fuel from the pump


2


is returned by a return conduit


6


to the tank


1


.




The fuel in the common rail


4


is delivered via delivery conduits


7


to a plurality of injectors


8


each for each cylinder of the engine to inject the fuel into the respective cylinders; part of the fuel delivered via the conduits


7


to the injectors


8


that has failed to be consumed for injection into the cylinders is returned via a return conduit


9


to the tank


1


.




Reference numeral


10


denotes an engine-control computer or ECU (electronic control unit) which receives, for detection of operational status of the engine, various signals such as a cylinder discriminating signal


11


from an engine cylinder discriminating sensor, a crank angle signal


12


from a crank angle sensor for sensing phase difference relative to for example a top dead center (TDC), an accelerator opening signal


13


from an accelerator opening sensor (engine load sensor) for sensing a pressurized amount of an accelerator pedal and an engine revolution speed signal


14


from an engine revolution speed sensor.




The common rail


4


is provided with a pressure sensor


15


which detects pressure in the common rail


4


. A pressure signal


16


from the sensor


15


is also inputted to the electronic control unit


10


.




On the basis of these signals, the electronic control unit


10


issues injection commands


18


to electromagnetic valves


17


of the injectors


8


to optimize the engine output in line with the operational status, thereby optimally controlling fuel injection conditions, i.e., fuel injection rate and timings (injection starting and ending timings).




The pressure in the common rail


4


, which may be lowered due to consumption of the fuel in the rail


4


through injection by the injectors


8


, is controlled by the electronic control unit


10


to a required fuel injection pressure depending upon the operational status of the engine. More specifically, the unit


10


issues a pressure control command


20


to an electromagnetic valve


19


of the discharge rate control valve means


5


of the fuel pump


2


to control the discharge rate of the fuel pump


2


, thereby controlling the pressure in the common rail


4


.




Injection starting and ending timings of the fuel are controlled such that phase difference from a predetermined crank angle (for example, that of TDC) is calculated by the crank angle sensor on the basis of which the electronic control unit


10


issues command pulses (the injection commands


18


) to establish drive current to the electromagnetic valves


17


of the injectors


8


so as to inject the fuel over a predetermined period in terms of the crank angle signal


12


.




In the common rail type fuel injection system thus constructed, the fuel pump


2


is engine driven by torque transmitted from a crankshaft via a gear train with the revolution ratio of the engine to the fuel pump


2


being two-to-one (i.e., two revolutions of the engine per revolution of the fuel pump) as traditional with respect to the timings of the conventional mechanical fuel injection systems; this will needlessly involve increase in capacity of the fuel pump


2


irrespective of the fact that such revolution ratio has no substantive meanings or advantages in the common rail type fuel injection system.




That is to say, in a mechanical fuel injection system where fuel discharge timing of the fuel pump


2


is mechanically made accordant with fuel injection timing for a four cycle engine, the revolution ratio of the engine to the fuel pump must be two-to-one to attain two revolutions of the engine per injection in the respective cylinders whereas such revolution ratio of two-to-one has no specific meanings or needs in a common rail type fuel injection system where the fuel from the fuel pump


2


is accumulated in the common rail


4


in pressurized state and the fuel injection in the respective cylinders is electronically controlled.




In view of the above, the inventors thought of an engine with a common rail type fuel injection system where revolution ratio of the engine to a fuel pump is set to one-to-one, which allows reduced fuel discharge rate per revolution of the fuel pump and thus allows the fuel pump to be smaller-sized, leading to improvement in mountability of the engine to a vehicle.




However, there are problems in this respect. As shown in

FIG. 2

, in a conventional gear train G for transmission of torque from a crankshaft


21


to the fuel pump


2


, rotation or revolution of the crank shaft


21


integral with the crank gear


22


causes a larger main idler


23


in mesh with the gear


22


to rotate integrally with a smaller main idler


24


; then, an air compressor gear


25


in mesh with the idler


24


is rotated integrally with a drive shaft


26


which serves to drive not only the fuel pump


2


but also an air compressor


27


(see FIG.


4


). Therefore, if the revolution ratio of two-to-one as shown in

FIG. 2

is to be changed into one-to-one, then, as shown in

FIG. 3

, the air compressor gear


25


must be in mesh with the larger main idler


23


having gear teeth twice in number as great as that of the smaller main idler


24


, which will involve substantial displacement of an axis of the air compressor gear


25


. As a result, a flywheel housing


28


which is to accommodate such gear train G must be inevitably changed in shape, resulting in significant increase in cost.




More specifically, as shown in

FIG. 4

with reference to the structure shown in

FIG. 2

, the flywheel housing


28


is integrally formed with an accommodation space S for the gear train G which is partly defined by a bracket


28




a


of the housing


28


. The bracket


28




a


is formed with a gear through hole


29


through which the air compressor gear


25


is passed to the space S with the air compressor


27


being fitted together with the fuel pump


2


to the bracket


28




a


; thus, arrangement of the air compressor gear


25


in a position shown in

FIG. 3

utterly away from its original or conventional position will necessitate a new flywheel housing


28


with its gear through hole


29


being formed thereon in a different position. The flywheel housing


28


itself is an expensive and larger-sized part and is of various kinds such that dozens of alternative flywheel housings are usually stocked. Therefore, innovation of such housing with conventional stocks being reserved will lead to vast increase in cost from viewpoints of not only manufacture but also storage.




BRIEF SUMMARY OF THE INVENTION




The present invention was made in view of the above and has its object to set revolution ratio of an engine to a fuel pump to one-to-one without involving vast increase in cost, thereby allowing a fuel pump to be smaller-sized.




The invention is directed to a fuel pump drive system for engine driving a fuel pump by torque transmitted from a crankshaft via a gear train, comprising a conventional flywheel housing with a gear through hole opened to a gear train accommodation space and adapted to receive a conventional input gear as an element of the gear train for transmission of the torque to the fuel pump through meshing with an output gear with revolution ratio of an engine to the fuel pump being set to two-to-one, a new input gear in lieu of said conventional input gear for transmission of the torque to the fuel pump through engagement with said output gear via an idle gear within a range of said gear through hole with revolution ratio of the engine to the fuel pump being changed to one-to-one, and an adapter interposed between said flywheel housing and said fuel pump for rotatably supporting said idle gear in a position for meshing with said new input gear.




Thus, use of the existing or conventional flywheel housing with the gear through hole for receiving the gear train with revolution ratio of the engine to the fuel pump of two-to-one, without changing the design of the flywheel housing and together with the new input gear and the idle gear which are receivable in the gear through hole of the existing flywheel housing, can change revolution ratio of the engine to the fuel pump to one-to-one, which allows a reduced fuel discharge rate per revolution of the fuel pump, thereby allowing the fuel pump to be smaller-sized.




Moreover, in the invention, an air compressor may be arranged between the adapter and fuel pump, both the fuel pump and the air compressor being driven by a drive shaft. This allows, in a vessel with the air compressor being arranged between the adapter and fuel pump, the air compressor to be also driven with revolution ratio of one-to-one with respect to the engine, so that necessary air compression work can be attained by the air compressor which is smaller in capacity than the conventional ones, leading to allowance of the air compressor to be smaller-sized.




A preferred embodiment of the invention will be described in conjunction with the drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a block diagram for schematically showing a conventional common rail type fuel injection system;





FIG. 2

is a front view of a conventional gear train with revolution ratio of an engine to a fuel pump being two-to-one;





FIG. 3

is a front view of the gear train shown in

FIG. 2

with revolution ratio being changed to one-to-one;





FIG. 4

is a perspective view of the conventional structure shown in

FIG. 2

;





FIG. 5

is a perspective view showing an embodiment of the invention;





FIG. 6

is a front view showing the gear train in the embodiment; and





FIG. 7

is a perspective view showing in details the adapter of FIG.


5


.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT





FIGS. 5-7

show an embodiment of the invention in which any parts similar to those in

FIGS. 1-4

are designated by the same reference numerals.




As shown, in the embodiment, an air compressor gear


25


(a conventional input gear: see

FIGS. 2 and 4

) used for revolution ratio of the engine to the fuel pump


2


of two-to-one is replaced with an air compressor gear


30


(a new or substitutive input gear) which has a radius and gear teeth substantially half as great as those of the conventional input gear. As is conventional, concentrically connected to this air compressor gear


30


is a fuel pump


2


. More specifically, both the fuel pump


2


and the air compressor


27


are driven in unison by a drive shaft


26


rotated integrally with the air compressor gear


30


.




The new air compressor gear


30


is received together with an idle gear


31


within a range of a gear through hole


29


of a conventional or existing flywheel housing


28


which has been designed for a gear train G for revolution ratio of the engine to the fuel pump


2


of two-to-one, the hole


29


being originally opened for reception of the conventional air compressor gear


25


. Through this idle gear


31


, a smaller main idler


24


(output gear) is engaged with the air compressor gear


30


so that torque is transmitted to the fuel pump


2


with the revolution ratio of the engine to the fuel pump


2


being changed to one-to-one.




The idle gear


31


in mesh with the air compressor gear


30


is rotatably supported by an adapter


32


interposed between the flywheel housing


28


and the air compressor


27


.




This adapter


32


is fitted to the flywheel housing


28


to which the air compressor


27


has been fitted, such that the idle gear


31


is properly positioned to mesh with the smaller main idler


24


.




Thus, in this way, without design-changing the existing flywheel housing


28


designed for the gear train G with revolution ratio of the engine to the fuel pump


2


being two-to-one, the new air compressor gear


30


and idle gear


31


receivable in the range of the gear through hole adapted to originally receive the conventional air compressor gear


25


(see

FIGS. 2 and 4

) enable revolution ratio of the engine to the fuel pump


2


to be changed into one-to-one, which will reduce fuel discharge rate per revolution of the fuel pump, allowing the fuel pump


2


to be smaller-sized.




Therefore, according to the above embodiment, without design-changing the existing flywheel housing


28


, revolution ratio of the engine to the fuel pump


2


can be changed into one-to-one, which allows the fuel pump


2


to be smaller-sized; thus, with respect to an engine with the common rail type fuel injection system applied, mountability of the engine to a vehicle can be drastically improved without vast increase in cost.




Moreover, especially in this embodiment, the fuel pump


2


and the air compressor


27


interposed between the adapter


32


and the fuel pump


2


are driven by one and the same drive shaft


26


so that the air compressor


27


can be also driven with the revolution ratio with respect to the engine being one-to-one. As a result, necessary air compression work can be effected by the air compressor


27


which is smaller in capacity than the conventional ones, allowing the air compressor


27


to be smaller-sized.




It is to be understood that the invention is not limited to the above embodiment and that various changes and modifications may be made without departing from the spirit and scope of the invention.



Claims
  • 1. A fuel pump drive system for engine driving a fuel pump by torque transmitted from a crankshaft via a gear train, comprisinga conventional flywheel housing with a gear through hole opened to a gear train accommodation space and adapted to receive a conventional input gear as an element of the gear train for transmission of the torque to the fuel pump through meshing with an output gear with revolution ratio of an engine to the fuel pump being set to two-to-one, a new input gear in lieu of said conventional input gear for transmission of the torque to the fuel pump through engagement with said output gear via an idle gear within a range of said gear through hole with revolution ratio of the engine to the fuel pump being changed to one-to-one, and an adapter interposed between said flywheel housing and said fuel pump for rotatably supporting said idle gear in a position for meshing with said new input gear.
  • 2. The system according to claim 1 wherein an air compressor is interposed between the adapter and the fuel pump, said air compressor and said fuel pump being driven by a drive shaft.
Priority Claims (1)
Number Date Country Kind
2002-060424 Mar 2002 JP
US Referenced Citations (8)
Number Name Date Kind
2512125 Whited Jun 1950 A
3781137 Engstrom Dec 1973 A
4218193 Mehne Aug 1980 A
4305352 Oshima et al. Dec 1981 A
4411237 Ableitner et al. Oct 1983 A
5255643 Mochizuki et al. Oct 1993 A
5511956 Hasegawa et al. Apr 1996 A
6415758 Pierro et al. Jul 2002 B1