GB2135730A - Fuel injection systems for IC engines - Google Patents

Abstract

Fuel is supplied to an injector 4B by a fuel injection pump 4A driven by a crank mechanism 50-55, Fig. 1, the injector 4B comprising an accumulator 16 from which fuel is supplied to a space 15 surrounding an injection valve 12 which is caused to open by a pressure drop in the fuel passages 5a, 7a, 7c supplying the accumulator 16 and, via fuel passage 8a, the space behind the injection valve 12. Closure of the injection valve 12 is caused by the drop of pressure in the accumulator 16. The pressure drop in fuel passages 5a, 7a, 7c is caused by actuation of valve 17. In a distribution type injection pump, Fig. 5 rotation of drive shaft 107 causes a crank- shaft 122 to rotate about a vertical axis and, by way of level gears 113, 114, 119 and 125, about a horizontal axis. Fuel is metered to chamber 136 by a governor 145 in accordance with the portion of a lever 141 and engine speed. <IMAGE>

Description

SPECIFICATION Fuel injector The present invention relates to a fuel injectorfor a compression ignition engine.

In the usual jerk or unit injectortype injection device krfown in the prior art, a plunger is lifted bythe rotation of acas shaft to compress and discharge a fuel therebyto inject the fuel through a nozzle into a combustion chamber of an engine. In this construction ofthe prior art, however, the pressure and rate of the injection are necessarily low at low engine speeds so that the performance and thermal efficiency of the engine at low engine speeds are unsatisfactory.

In orderto improve the combustion efficiency, shortenthefuel injection period and enhance the isochoric degree with a viewto improving the thermal efficiency overthe whole r.p.m. range and the whole load range, it is necessaryto increase the injection pressure and rate. It is, however, difficult using the aforementioned device to increase the injection pressure and rate.

In orderto solve this problem there have been developed several accumulating type fuel injection devices, some ofwhich are of practical valvue but have not yet come into common use.

Oneofthe reasonsforthisisthatalthough an accumulating type fuel injection device using no booster is simple in construction and low in price, there is a face pressure between the cam and the roller which makes its difficultto raise the injection pressure to 1000atms. Moreover,although a boostertype accumulation fuel injection device can injectfuel at high-pressure over a shorttime period by electronic control it is high in price and low in reliability because of its complicated construction.

In known fuel injection devices, the plunger is always driven by coaction ofthe cam and a roller follower. As a resultthe contact between the cam and the roller is of linear type so that the Hertz stress of the linearly contacting portion is increased in accordance with the increase in the injection pressure until the contacting faces of the cam and the roller finally fail because offatigue. This obstructs the development of injection devices which will generate high pressure at a high injection rate.

It is, therefore, an object ofth is invention, to provide a high-pressure fuel injector which will generate notably higherfuel injection pressures.

Another object ofthe present invention isto provide a fuel injector which can be easily adapted for use not only with low- and medium- speed but also with high-speed diesel engines.

The present invention provides an accumulating type fuel injector in which the injection of a fuel is started bya fall in the pressure in a fuel passage from a fuel injection pump of non-accumulating type to an .accumulating chamber and is ended byafall in pressure in the accumulating chamber, and in which the plunger of the injection pump is driven by means of a crank mechanism.

The invention is particularly useful when applied to a distribution type fuel injector.

Afuel injector to be used with a diesel engine intrinsically is of complicated construction andre- quires highly accurately machined parts because it handles fuel under high pressure, consequently, it is very expensive and adds considerablyto the cost of a diesel engine.

In this respect, a distribution type fuel injector has an advantage that it has a smaller number of parts and is light, small and inexpensive. However, a distribution type fuel injector has to supply the fuel to each of the cylinders over one cycle ofthe engine so that a plunger drive mechanism constructed of a cam, a rollerfollower and a spring driven at a high speed in accordance with the number ofthe engine cylinders is subjected to a high degree of stress. Consequently, the injection pressure has to be restricted so that its application of cam-driven distribution type fuel injectors is effectively limited to auxiliary chamber type diesel engines in which high injection pressure is not required.

The present situation is that auxiliary chamber type diesel engines are gradually being replaced by direct injection type fuel injector because ofthe higher thermal efficiency of the latter. Also, with a view to further improving the thermal efficiency of direct injection type diesel engines, efforts are being made to raise the injection pressure and rate thereby to shorten the injection period.

However, up to now no direct injection type diesel engine capable of running at the desirably high injection pressure (e.g. 2,000 atms) is commercially available because of high price and unsatisfactory reliability.

The present invention provides a distribution type fuel injectorwhich can distribute and supply a fuel at a supply pressure as high as 2,000 atms to the respective cylinders of an engine by means of one plunger and which is light, small, inexpensive and highly reliable.

The present invention therefore also provides a fuel injectorfor a compression ignition engine, comprising, a fuel injection pump including a suction re yrn valve disposed in a high-pressurefuel passage communicating with a barrel in which a plunger is fitted; and an accumulating type fuel injection valve including a fuel injection valve having a needle valve the opening of which is controlled bythe pressure of fuel and bya spring and an injection port which is opened and closed by said needle valve, and an accumulating chamber disposed in a portion of said high-pressure fuel passage so that said needle valve is opened by a fall in the pressure in said high-voltage fuel passagetherebytostartthefuel injection and is closed by a drop in the pressure in said accumulating chambertherebyto terminate injection, of fuel, the said plunger being driven by a crankshaft and a connecting rod.

The present invention will now be described in connection with the embodiments thereof with refer enceto the accompanying drawings in which: Figure 1 is a front elevation showing a fuel injector and crank drive; Figure 2A is a sectional view of a fuel injector; Figure 2B is an enlarged view ofthe control valve shown in Figure 2A; Figure 3 is a sectional view ofthe drive to the injector; Figure 4 is an elevation of another embodiment of injector and drive; Figure 5 is a sectional view of a crank-driven distribution type fuel injector; Figure 6 is a section along line A-A of Figure 5; Figure 7 is a section along partof line B-B of Figure 5; Figure 8 is a sectional view of part of another embodiment of an injector; Figure 9 is a section along line C-C of Figure 8; Figure 10 is a section along line D-D of Figure 8; and Figure 11 showsthe relationship between the locus of the movement ofthe spill port, the relative position ofthe sliding face ofthe adjusting piece and the injection timing and rate.

In Figure l,a piston 2 is fitted in a cylinder block 1 having an upperface carrying a cylinder head 3 in which the injection port of an accumulating type fuel injector4 is positioned.

With reference to Figure 2, injector 4 comprises a fuel injection pump4Aand an accumulating type fuel injection valve 4B which is connected to the leading end of that pump and equipped with a fuel injection valve 4b.

In the accumulating type fuel injection valve 4B a thread formed in the upper end of a nut 6 is screwed in a thread which is formed in the lower end of a sheath 5 ofthe injection pump 4A. In the nut 6, there are fitted in thight relationship a control valve member 7, a spacer 8, an accumulating cylinder 9, a spacer 10, and a needle valve member 11, which are arranged in the enumerated order.

The needle valve member 11 is formed at its leading end with an injection port 11 a, the opening and closing ofwhich are controlled by the coaction ofthe valve seat at the leading end inner wall of the valve member andthevalvefaceofa needle valve 12.

This needle valve 12 has its upper half or larger diameter portion fitted in the needle valve member 11 in an axially movable manner. To the upper end ofthe larger diameter portion, there is fixed a spring bearing 13, on which a spring 14 is elastically mounted.

The needle valve member 11 is formed therein which a fuel passage 11 a which has communication with a space 15 surrounding the outer circumference of a smaller diameter portion ofthe needle valve.

The spacer 10 is also formed therein with a fuel passage 1 Oa which has its upper portion communicating with an accumulating chamber 16 in the accumulating cylinder 9 and its lower portion communicating with the passage 11 a.

Thespacer8 isformed with passages 8b and 8for providing communication between afuel passage 8a having communication with the atmospheric pressure side of the needle valve 12 and the accumulating chamber 16. The spacer 8 at its lower end bears against an end of the spring 14. The fuel passage 8a communicateswith afuel passage7aofthecontrol valve member7 and with fuel passages 7b and 7c branched from that passage 7a. This passage 7a furthercommunicateswith therecornmunicates with a afuel passage 5a of the sheath 5.Moreover, the fuel passages 8a, 7a and 7b are made to communicate with the atmospheric pressure side ofthe needle valve 12, and an injection end control valve 17 is disposed between those passages and the fuel passage 8b communicating with the accumulating chamber 16. The injection end control valve 17 has its larger diameter portion fitted in the control valve member 7 in a vertically movable manner. The valve face 1 7a of that control valve is pushed down bythe action of a compr~ssion spring 18 which is disposed in the sheath 5, and the spacer8 acts as the stopperthereof. As shown in Figure 2B, moreover, thatvalve face can come, when it is lifted, into abutmentagainstthevalveseat7d ofthecontrol valve member 7.

Between thefuel passage 7c and the passage 8c, there is attached to the control valve member7 a check valve 20 which is enabled to blockthe flow ofthe fuel from the passage 8cto the passage7cbytheaction of a compression spring 19 accommodated in the spacer 8. Moreover, the fuel leaking from the sliding faces of the control valve member 7 and the injection end control valve 17 is returned to the atmospheric pressure side by way of a fuel return passage 22 having communication with a spill port 21 in the injection pump 4A.

Next the internal construction ofthe fuel injection pump 4Awill be described. A suction return valve 24 for preventing any leakage while being looselyfitted in a suction valve member 23 is enabled to have a function as a check valve by a compression spring 25 and has its valve head regulated bythe action of a stopper 26.

Moreover, the plunger 28 is slidablyfitted in a barrel 27.

In the barrel 27, there is interposed between a fuel inlet 29 and a fuel passage 30 a check valve 31 which is caused to perform a checking action by a spring therebyto blockthe reverse flow ofthe fuel from the passage 30 to the inlet 20. The barrel 27 is formed with the spill port 21 at its middle portion, and thefuel return passage 22 prevents establishment of a back pressure in the control valve 17 thereby to return the fuel therefrom through a fuel return port 32 to a fuel tank (not shown) orthefuel inlet 29. Eitherthefuel inlet 29 and the fuel return port 32 orthisfuel return port and the atmosphere have to be suitably prevented from an leakage by means of an O-ring orthe like.

Incidentally, the barrel 27 and thesunction return valve meber 23 are mounted in the sheath 5 by means ofthreads 33.

The plunger 28 having the same construction as that ofthe Bosch type is formed with a passage 28a. The supplyoffuel bytheinjectorterminates when the notched face 28b of the plunger28 communicates with the spill port 21, whereupon subsequent dis charge of fuel bythe head ofthe plunger is conducted through the spill port out ofthefuel return port 32.

An adjusting rod 34 is slidably borne in the sheath 5 and is formed in its portion with a rack34a, which is in meshing engagementwith a pinion 28cformed on the plunger 28.

Incidentally, the adjusting rod 34 has its position determined by the balance with the oil pressure, which comes from an oil pressure inlet 36 and acts againsttheforce of a spring 35, therebyto determine the injection timing.

As to the construction of the driving mechanism of the plunger 28 of the injector, reference is now made to Figure 3. A crosshead 37, which is fitted in a vertically movable manner in the hollow portion at the upper end ofthe sheath 5, has its one end connecting with the plunger 28 in a rotatable manner and its other end fixed a pin 38 thereto. To this pin 38, there is rotatably connected through a bush 40 the lower end of a link 39 which has its upper end connected rotatablythrough a bush 41 and a pin 42 to the lefthand end ofa rocker arm 43. This rocker arm 43 is rotatably engaged through a bush 44, which is fixed thereto, to a rockershaft 46 which is fixed in a bracket 45 projecting from the cylinder head 3 (which is shown in Figure 1), and has at its other end a pin 47.On this pin47,there is rotatably mounted th rough a bush 48 the upper encl of a connecting rod 49 which has its lower end rotatably mounted on a crankpin 51 through bearings 52 and 53, the crankpin being eccentric to the axis of a camshaft 50 for actuating intake and exhaust valves, as shown in Figure 1. Bearings 52 and 53 are fixed in the connecting rod 49 by a bearing cap 54 secured by means of a bolt 55.

The operation of the injector ofthe present invention will now be described.

Fuel isfed byway ofthe fuel inlet 29, the check valve 31 and the passage 30to a chamber in the barrel 27.

In accordance with the downward movement ofthe plunger 28 form its top dead centre, the checkvalve 31 is closed so that the pressure in the chamber is raised, the suction return valve 24 is pushed down and fuel is pumped to thefuel passages 5a, 7a and 8a.

Atthis time, the injection end control valve 17 is pushed down by the spring 18 and has its valve face 17a spaced from the valve seat 7d ofthe control valve member7, as shown in Figure 2B, so that it is open.

The fuel fed to the passage 7a is further pumped by way of the passage 7b,the injection end control valve 17 and the passage 8bto the inside ofthe accumulating chamber 16.

The fuel is a compressible fluid, as is well known in the art, so that it is stored in the accumulating chamber 16 while having its volume reduced in proportion to the rise in the pressure.

When the pressure in the accumulating chamber 16 reaches a level, e.g. 1000 atms, the injection end control valve 17 is pushed upward againstthe compression spring 18so that its valve face 17a is brought into contact with the valve seat7d to block the communication between the passages 7b and 8b.

After this time, the check valve 20 is opened so that the fuel having passed through the passages 7a and 8c is compressed and accumulated under a higher pressure in the accumulating chamber, this pressure being applied through the fuel passages 1 Oa and 11 a to the lower portion ofthe needle valve 12.

Fuel inside the passage 8a is, like that inside the accumulating chamber 16, at a higher pressure, and this is applied to the uppersideofthelarger-diameter portion of the needle valve. In this state, (the force of the spring 14) + (the pressure x the area ofthe larger diameter portion of the needle valve) = (the pressure to push down the needle valve 12), and (the pressure) x (the area of the larger diameter portion ofthe needle valve - the area ofthe smaller diameter portion of the needle valve) = (the force to push up the needle valve 12) so that the valve face is forced into contactwith the valveseattherebytopreventthefuelfrom leaking out ofthe injection port 1 1a.

As the engine continues to revolve, the plunger 28 is further pushed down until the maximum pressure at the high pressureside ofthe injection system atthe maximum fuel injection rate reach reach as high as 2000 atms.

Atthis time, communication between the passage 28a and the spill port 21 is established by the notched face 28b of the plunger 28. The fuel at a high pressure side flows through the passage 28a until it overflows through the spill port 21 into the fuel return port 32.

At this time, the suction return valve 24 is closed and the pressure in the passages 5a, 7a and 8a drop abruptly as a result of its returning action so that the pressureattheatmosphericpressureside pushing down the larger diameter portion of the needle valve 12 disappears.

Meanwhile, the valve face continues to be seated on the valve seat, while the injection end control valve 17 is pushed up because the pressure is equal to or higher than 1000 atms, for example, so thatthe high-pressure fuel in the accumulating chamber 16is prevented by the check valve 20 from flowing back into the passages 5a, 7a and 8a.

Atthis time, the force of (the area of the larger diameter portion ofthe needle valve - the area of the smaller diameter portion of the needle valve) + (the pressure) pushes the needle valve 12 againsttheforce ofthe compression spring 14therebyto establish between the valve face and the valve seat a gap through which the fuel is injected from the injection port 1 1a into the engine combustion chamber. In accordance with the progress ofthe fuel injection, the pressure of the fuel having been compressed in the accumulating chamber 16 continues to drop to 1000 atms, for example. Then the injection end control valve 17 is pushed down and opened, as shown in Figure 2A, so that the fuel in the accumulating chamber 16 flows back th rough the passages 8b an 7b into the passages 7a and 8a.

Atthis time,the suction return valve 24 is in its closed state so that the fuel does not overflow from the spill port 21, and the fuel passage 8a naturally acquires the same pressure as that in the accumulating chamber 16, which pressure is applied to the atmos pheric pressure side at the upper portion of the needle valve thereby to abruptly close the needle valve 12.

Thus, according to the present invention, by means ofthe injection end control valve 17, equal pressure is applied to both the upper and lower sides of the needle valve 12 simultaneously with the opening of that control valve 17, so that the needle valve 12 is accelerated toward the valve seat 11 b bythe force of the spring 14 without being influenced by the pressure in the accumulating chamber 16. Thus, it is possible to increasethevalve closing rateto shorten the fuel injection period thereby to effect a high injection rate.

The drive means ofthe plunger28 will now be described. As shown in Figure 1 the crankpin 51 causes reciprocation of the connecting rod 49 by the revolution of the camshaft so thatthe rocker arm 43 follows the motions of the lower end portions of the connecting rod 49thereby to rockonthe rocker shaft 46. The rocking motion ofthe rocker arm 43 causes the crosshead 37 to move up and down through the link 39 therebyto drive the plunger 28 which is rotatably connected to the crosshead 37.When the crankpin 51 is being turned form the bottom dead centre toward thetop dead centre by revolution ofthe camshaft50, the connecting rod 49 is moved upward, and this movement is transmitted through the pin 47 to the rocker arm 43so that the rocker arm is turned counter-clockwise around the rocker shaft 46.

As a result, the pin 42 at the other end ofthe rocker ar n 43 is moved downward to push down the crosshead 37 through the link 39 and the pin 38.

The plunger28 connected to the crosshead 37 raises the pressure ofthefuel in the barrel 27, while moving downward, and opensthesuction return valve 24 therebyto pumpthatfuel intothefuel passage8a.

This pressure is applied to the upper side of needle valve 12 andthereby opensthe needlevalve and the check valve 20.

Asthecrankpin51 continues to revolve the plunger 28 continues to be moved down to raise the pressure in the fuel passage 8a so that fuel is pumped through the fuel passage7c,thecheckvalve 20 and the fuel passage until it is accumulated in the accumulating chamber 16.

When the crankpin 51 is furtherturned to approach the top dead centre, the plunger 28 isfurther moved down so that its notched face passes over the spill port 21 to open the passage between the spill port 21 and the inside ofthe barrel 27 through the passage 28a.

Since the spill port 21 communicates th rough the fuel inlet 32 with the low-pressure side, the fuel in the barrel 27 flows outtheretoo.

At this time, the suction return valve 24 is closed to drop the pressure in the fuel passage 8a by its movement in the returning action.

The high-pressurefuel in the accumulating chamber 16 is blocked by the check valve 20 so that it does not flow into the fuel passage 8a.

When the pressure in the fuel passage 8a drops, the pressure to be applied to the lower portion ofthe needle valve 12 through the fuel passage 11 a pushes up and opens the needle valve 12 againsttheforce of thespring 14therebyto injectfuel from its injection portlla.

Simultaneously with the injection ofthefuel, the pressure in the accumulating chamber is dropped so thatthe needle valve is closed to terminate the injection when the force of the spring 14 exceeds the pressure applied to the lower portion ofthe needle valve.

While the crankpin 51 is being furtherturned over thetop dead centre toward the bottom dead centre, the plunger 28 is continuously moved up to approach the bottom dead centre. The, the upperend ofthe plunger opens the spill port 21 so that fuel is drawn in in preparation forthe next cycle of operations.

The bushes 40,41,44 and 48 of Figure 3, the bearing 52 (which is shown in Figure 1) orthecorresponding pines 38,42,46 and 47 or the crankpin 51 are designed and sized such that the face pressure thereon are about 300 atms when the plunger 28 feeds the fuel under 2000 atms, and are constructed to ensure the reliably withstand such pressures. The injection pressure can be raised, when required by enlarging the proportions ofthe pump driving system.

Another embodiment of an injection pump unit4Aa which is connected by means of a high-pressure pipe to the accumulating type fuel injectionvalve 4B shown in Figure 2, will now be described with rsferenceto Figure 4.

Afeature of unit 4Aa is that a plungerS6fitted therein is driven by means of a crankshaft 60 through a connecting rod 59 which is rotatably mounted in the pin 58 of a crosshead 57. Otherwise, the construction ofthe injection pump unit 4Aa isthe same asthat of the known Bosch type orasthe injection pump 4A shown in Figure 2.

To the smaller end portion ofthe connecting rod 59, there is fixed a bush which acts as a bearing forthe pin 59.Thelargerend portion is rotatably mounted through a bearing on the crankpin 61 ofthe crankshaft 60, and a bearing cap 62 is attached thereto by fastening bolts 63. The plunger 56 is moved up and down by revolution ofthe crankshaft 60, and the pump unit4Aa is connected through a high-pressure pipe 64 with the fuel passage 8a of the accumulating type injection valve 4B by means of a nut 65.

In the operation of the injection pump unit 4Aa the accumulating type injection valve 4B functions in the same way as in the embodiment of Figure 2 and has the same construction as that of the Bosch type except forthedrivemechanism oftheplunger56.Thefuel injection pump 4Aafunctions in the same way as the unitinjectorshown in Figure 2 sothatthe crosshead 57 and the plunger 56 are moved up and down on the revolution ofthe crankshaft 60 thereby to feed high-pressurefuel through the high-pressure pipe 64 to the accumulating injection valve 4B.

In the construction thus far described, the injection rate ofthe accumulating type fuel injector is determined exclusively by the pressure in the accumulating chamber and bythe diameter ofthe injection portand is not dependent upon the speed ofthe plunger.

Consequently, the plungercan be driven buy a crank mechanism and its speed varies in sinewave form.

Moreover, the plunger driving system ofthe present invention is of positive motion type and requires no spring thereby avoiding the risk ofthe spring breaking under stress or of surging. The design and manufac tureofa high-pressurefuel injector having an identical injection capacity can be facilitated by adopting the plunger which is less liable to leakage and which has a small diameter.

According to the presentinvention,theplunger driving system has neither point nor linear contacting portion and since the plunger is driven by a crankshaft, not by a cam, high-pressure injection can be achieved without the use of a booster, so that the injection can be simplified.

The distribution type fuel injectorto which a crankshaft drive may be applied is now described with reference to Figures 5 to 11.

As shown in Figure 5, a body 101 and a barrel member 102 are connected by means ofa plurality of bolts 103.

In the body 101 having a flange 104for mounting on the engine, there is disposed a drive shaft 107 which is rotatably borne by means of bearings 105 and 106.

Said drive shaft 107 has fixed on its outer end a gear 108, which is driven at a predetermined reduction ratio bythe crankshaft (not shown) ofthe engine. On its other inner end is fixed a drive bevel gear 113 by means of bearing caps 109 and 1 and a plurality of bolts 111. Said bevel gear 113 is carried by a bearing 112 which is fixed in the barrel member 102.

An intermediate bevel gear 114 meshes at right angles with bevel gear 113. Said bevel gear 114 is carried by bearings 117 and 118 in a bearing member 116which is mounted inthe body101 by means of a plurality of bolts 115.

An accelerating or gearing-up bevel gear 119 is mounted in the body by means of bearings 120 and 121 which surround the drive shaft 117. The bevel gear 119 meshes with the intermediate bevel gear 114 therebyto drivethe same in the direction oppositeto that of the drive shaft 107.

Acrankshaft 122 is borne in the drive shaft 107 at right angles to the axis thereof by means of plain bearings 123 and 124. The crankshaft 122 has fixed thereon at one end of a driven bevel gear 125 which meshes with the bevel gear 119. As a result, the crankshaft 122 is turned horizontally, as viewed in Figure 5, by the revolution ofthe drive shaft 107 and around the axis thereof by the actions of the bevel gears 119 and 125.

A connecting rod 126 has its larger end attached rotatablyto the crankpin 127 ofthe crankshaft 122, as shown in Figures 5and 7, and its smaller end connected through a wrist pin 129 to a crosshead 128, which is fitted slidably and rotatably in the barrel member 102,therebyto restrict revolution of the crosshead 128 and to transmit the revolution of the drive shaft 107 to the crosshead 128 thereby to reciprocate the said crosshead 128.

A plunger 130 is formed with a distribution groove 131 in the upper circumference thereof and with a bore 132 atthe centre thereof. Said centre 132 has its lower end formed with a spill port 132a.The lower end of the plunger 130 is fixed in the crosshead 128.

Said plunger 130 slides in the bore 135 of a barrel 134which isfixed on the barrel member 102 by means of a plurality of bolts 133. An adjusting piece 137 is inserted in a chamber 136 which is formed across said bore 135.

In the barrel 134 areformed, equidistantaly arranged, oil supply passages 1 38a to 138din number corresponding to the number of cylinders of the engine (in the case, four) as is shown in detail in Figure 6. Said oil supply passages 1 38a to 1 39d are connected with fuel injection nozzles (not shown) mounted in the respective cylinders.

The adjusting piece 137 is formed in its outer side with a hole 139 which extends at right angles with respectto the plunger 130, as shown in Figure 5. In that hole, there is inserted the balled end portion 141 a of an adjusting lever 141, which is rotatably borne on the barrel member 102 by means of a pin 140, so that a lever 142 attached to one end of the aforementioned pin 140 moves the adjusting piece 137 up and down through the adjusting lever 141 therebyto adjustthe fuel injection timing in the following manner.

Specifically, one end of the lever 142 is connected through a Iinkl43totheleverl46ofagovernorl45 which responds to both the speed of revolution of the intermediate bevel gear 114 corresponding to the r.p.m. ofthe engine and the position of an output adjusting lever 144. As a result, the motions of said governor 145 are transmitted through the lever 146 and the link 143 to the lever 142 whereby the adjusting piece 137 is moved up and down to change the distance between the spill port 1 32a of the aforementioned plunger 130 and the lower end face 1 37a ofthe adjusting piece 137 therebyto adjustthe injection timing.

Afuel pipe 147 communicates between a fuel tank (not shown) and the governor 145. Fuel is metered by the governor 145 in accordance with the position of the output adjusting lever 141 and the r.p.m. of the engine so thatthe metered fuel is supplied through a pipe 148to the inside of the chamber 136.

Figures 5 to 8 showthe fuel injector of the present invention as applied to afour-cylinderengineof equal ignition interval. When the drive shaft 107 is turned by the gear 108 which is driven at a predetermined reduction ratio by a gear (not shown) fixed on the crankshaft ofthe engine, the drive bevel gear 113 is fixed on the said shaft 107 drives the intermediate bevel gear 11 4which is turn drives the accelerating bevel gear 1 19,which is borne in the body 101,atthe same angularvelocity asthatof and in the opposite direction of the drive shaft 107.

As a result, the drive bevel gear 125, which is in meshing engagementwith the bevel gear 119 and which has one half as many teeth as that of gear 119, is driven to turn the crankshaft 122.

Thus,thedriven bevel gear 125 is revolving in meshing engagement with the drive bevel gear 119 around the crankshaft 122 the axis of which revolves horizontally in accordance with the revolution of the drive shaft 107. As a result, if the drive shaft 107 revolves once, the angular velocity is doubled bythe tooth ratio to the bevel gear 119 and finally quadrupled, because the bevel gear 119 is revolving in the opposite direction and at the same angular velocity, as that ofthe drive shaft 107. Thus, the crankshaft 122 revolvesfourtimes during one revolution ofthe drive shaft 107.

On revolutions of the crankshaft 122, the connecting rod 126 is caused to effect both a part revolution of 90 degrees and one reciprocation ofthe plunger 130, which is fixed in the crosshead 128, through the wrist pin 129 within the sliding bore 135 of the barrel 134, for each part revolution of the drive shaft 107 of 90 degrees.

Atthe same time, the governor 145 is driven by the intermediate bevel gear 1 14so that fuel is metered in accordance with the rotational speed thereof and the position ofthe output adjusting lever 144, the fuel being supplied to the chamber 136 by way of the pipe 148.

As a result, during the downward movement of the plunger 130, fuel from the chamber 136 is sucked from the spill port 132a ofthe plunger 130 through the bore 132 into the upper portion ofthe sliding bore 135 of the barrel 134. Said fuel starts to be compressed, when the spill port 132a is closed by the lower end face 1 37a of the adjusting piece 137, as a result of the rise of the plunger 130, and has its pressure gradually boosted.

When this pressure reaches a predetermined level, i.e.

when the groove 131 comes into alignment with the oil supply passage 138, for example, fuel is fed to the fuel injection valve of one ofthefour cylinders until it is injected into the corresponding cylinder.

When the plunger 130 is further moved up so that the spill port 132a passed beyondthe upperend face 137b ofthe adjusting piece 137, communication between the chamber 136 and the bore 135 in the barrel 134 is restored through the bore 132 so that the fuel in the sliding bore 135 overflowsto end the iniection ofthefuel.

In a fuel injectorfor a six-cylinder engine of equal ignition interval the reduction ratio ofthe bevel gear 119tothe bevel gear 113can besetatavalue of 1,5 and six oil supply passages at equal spacing, can be provided.

When the fuel injection timing is to beadjusted,the adjusting lever 141 is turned clockwise orcounterc lockwise through the link 143 and the lever 142 by turning the lever 146 ofthe governor 145 clockwise or counter-clockwise so that the adjusting piece 137 is moved upward or downward bytheend portion 141a thereof, thereby the timing at which the spill port 1 32a ofthe plunger 130 is closed, i.e. the injection timing can be retarded or advanced.

Another embodiment of a fuel injector according to the present invention will now be described with reference to Figures 8to 11 which show an example in which the adjusting piece functions to adjust both the injection rate and the injection timing.

In Figures 8 and 9 constituent parts having the same functions as those ofthe embodiment of Figure 5 are indicated by the same reference numerals or symbols.

In Figure 8, an adjusting piece 371,which is made slideable and rotatable with the plunger 130, is formed, with an upper end face 371 b, which is inclined with respect to the axis ofthe plunger 130, and a lower end face 371 a which is at a right angle with respect to the same axis. As a result, the adjusting piece 371 has its sliding face with the plunger 130 limited and is formed with sliding faces b1, b2 and soon in number corresponding to the number of cylinders of a multicylinder engine.

The adjusting piece 371 has formed in its side a recess 391, in which the balled end portion 411 a of a lever 411 is inserted. Said lever 411 is fixed on a pin 400 which is borne slidably and rotatably by the barrel member 102.

To one end of the pin 400,there is attached a lever 149 which isformedwith a sloped groove 150 around its boss portion 149a. In the groove 150, there is fitted the end portion 1 52a of a lever 152 which is borne on a pin 151 fixed in the barrel member 102.

Figure 11 is an exploded view showing the sliding portions ofthe innerface of the adjusting piece 371 and the plunger 130 of the embodiment shown in Figures 8to 10. A broken line a generally following a sine curve indicates the locus ofthe movement ofthe spill port 132a; the aforementioned sliding face b1, which is surrounded by the solid lines ofthe upper end face 371 band the lower end face 371 a, indicates a position for a large injection rate; a sliding race c, which is surrounded by single-dotted lines, indicates a position for a small injection rate; and a sliding faced, which is surrounded by double-dotted lines, indicates a position for an advanced injection timing.Correspondingly, the positions, in which the spill port 1 32a is closed by the sliding face, are indicated byW and X, whereas the positions, in which the same are opened, are indicated byYand Z.

The operation of the embodiment ofthe present invention shown in Figures 8to 11 is as follows.

When the lever 152 is turned clockwise around the pin 151, as viewed in Figure 9, the end portion 152a of the lever 152 moves up the pin 400 through the sloped groove 150 so thatthe end portion 411 a ofthe lever 411 turns the adjusting piece 371 counter-clockwise wherebythe sliding face ofthe adjusting piece 371 changes its position relative to the spill port 1 32a from the solid line b1 appearing in the exploded view of Figure 11 to the position cindicated by the singledotted line.On the solid line b1 ,the spill port 132a is closed atXto start the injection and is opened atZto end the injection, whereupon the effective stroke of the plunger, which is proportionaltothefuel injection rate, is expressed by the letter.

Ifthe sliding face is moved to the position indicated by the single-dotted line c,the injection is started at X and is ended atY so thatthe effective stroke ofthe plunger is expressed by letter mto reduce the fuel injection rate.

Asa result,thefuel injection rate can be adjusted by turning the adjusting piece 371 aroundtheaxisofthe plunger 130.

On the other hand, ifthe lever 149 is turned counterclockwise like the aforementioned embodiment shown in Figure 5, the adjusting piece 371 is moved down bythe lever 411 so that the sliding portion b1 is moved to the positioned, which is indicated by double-dotted lines in Figure 11, thereby to advancethe staticfuel injection starting timing by n.

Thus, the adjusting piece 371 can adjust not only the fuel injection but but also the injection timing.

As shown in Figure 10,the reason why the groove 150 is sloped with respect to the pin 400 is that it is made to correspond to the broken line a orthe locus of the spill port, as shown in Figure 11,so that the fuel injection rate is notvaried when the injection timing is adjusted.

When the present invention is used in combination with an accumulating type fuel injector, the so-called "negative lead" is sufficient, in which the upper end face 371 b of the adjusting piece 371 is arranged at right angles to the axis of the plunger 130, the lower end face being sloped with respect to the same.

As has been described fuel can be distributed and fed to a plurality of cylinders by means of only one plunger so thatthe full injection pump can be made simpler, smaller, and lighter and can be produced at a lower cost. In addition, since the plunger 130 is driven bythe crankshaft 122 and the connecting rod 126, the injection pressure is not restricted bythe Hertz stress, as is the case when a cam and roller lubricated by the compressible fluid are useed as in the injection pumps ofthe prior art. As a result, the injection pressure can be easily raised by suitably selecting the facing pressure of the crank shaft and the bearings ofthe connecting rod lubricated by the fluid.

In the design exemplified in Figure 5, the facing pressure of the larger end bearing of the connecting rod is 500Kg/cm2 for a fuel injection pressure of 2,000 Kg/cm2 and is equal to that ofthe plain bearings in the usual diesel engine.

On the other hand, no spring is used so thatthe stroke ofthe plunger can be augmented withoutthe limitations arising from use of a spring.

Moreover, the diameter of the plunger can be reduced without affecting injection by extending the plungerstroke,andthe loads to be borne bythe respective constituent parts are reduced so that the noise and size ofthe drive mechanism can be reduced such that leakage from the gap between the barrel and the plungercan be reduced.

Thus, according to the present invention, a fuel injector can have its injection pressure raised not only to enhance the performance and thermal efficiency of the engine but also to effect a simpler construction and reduction in weight, size, noise and production cost.

Claims (4)

1. An accumulatingtypefuel injector in which the injection of a fuel is started by a fall in pressure in a fuel passage from a fuel injection pump of non-accumulating type of an accumulating chamber and is ended by a fall in pressure in the accumulating chamber, and in which the plunger ofthe injection pump is driven by means of a crank mechanism.

2. Afuel injectorforacompression ignition engine, comprising, afuel injection pump including a suction return valve disposed in a high pressurefuel passage communicating with a barrel in which a plunger is fitted; and an accumulating type fuel injection valve including a fuel injection valve having a needlevalvetheopening ofwhich is controlled bythe pressure of fuel and by a spring, and an injection port which is opened and closed by said needle valve, and an accumulating chamber disposed in a portion of said high pressure fuel passage so that said needle valve is opened by a fall in the pressure in said high voltage fuel passage thereby to start the fuel injection and is closed by a drop in the pressure in said accumulating chambertherebyto terminate injection fuel, the said plunger being driven by a crankshaft and a connecting rod.

3. Afuel injector comprising, a crank mechanism driven from a drive shaft by an accelerating gear mechanism, a plungerfor reciprocation in a barrel by said crank mechanism and formed with a fuel distributing groove; the barrel in which said plunger slides being formed with fuel supply passages in number corresponding to the number of engine cylinders, said plunger in its reciprocation being revolvable in the barrel to align its fuel distribution groove with each fuel supply passage in turn to supply fuel to each corresponding cylinder in turn.

4. Afuel injector as claimed in claim 3 in which the plunger is provided with a fuel inlet bore leading from a spill port in which an adjusting piece for closing the spill port at an adjustable point in the stroke of the plungerfor adjusting the injection timing of the injector.