GB2230559A

GB2230559A - Fuel injection valve

Info

Publication number: GB2230559A
Application number: GB8908419A
Authority: GB
Inventors: Hiroshi Kanesaka
Original assignee: Usui Kokusai Sangyo Kaisha Ltd; Kanesaka Gijutsu Kenkyusho KK
Current assignee: Usui Kokusai Sangyo Kaisha Ltd; Kanesaka Gijutsu Kenkyusho KK
Priority date: 1988-04-19
Filing date: 1989-04-13
Publication date: 1990-10-24
Also published as: DE3912834A1; FR2633332A1; GB8908419D0; JPH01267352A

Description

FUEL INJECTION VALVE The Present invention rel-,xte.s to a fuel injecLion

valve, more particularly, such a valve for use in a diesel engine and effective in enhancing Lhe rate. of fuel. injection at the end of an injection cycle rnth,?_r than at of the beginning of the cycle.

One knOWT1 automatic fuel injection valve for diesel engines Ghown in Figure 5, includes a needie valve body 103 having a tip needle valve 104 coopprating with a valve seat 10? to control the tlow of fuel to a nozzle 106. Tile valve body 103 is slidable in bare 102 urged 109.

F (110t upwardly on a in the lower part of a valve body 101 and downwardly by a valve spring 108 through a seat uel under pressure P from a fuel injection pump shown) flows into a fuel passage 110 avid acts the needle valve body 103 over an effective area (X - Y) at the lower end 105 of the needle valve body 103. When th.e upward force (area (X-Y) x pressure p) exceeds the downward force of' the spring 107, the valve body 103 moves upward lifting the needle from its seat 107 to open the valve so that is injected from the nozzle 106.

Once the valve is open, the effective area of the. needle valve body 103 (on which pressure acts) increasec from (X - Y) to (X), so that the force tending tu lift. the needle valve body.1.03, also increases. 3 1-1 CJ t h e needle valve body 103 accelerates until an upper rtid 103a thereof engages an upper end 101a. of the bore.

Figures 6A to 6D are graphs, Figure 6A indicating cl fuel into the pcassage 1.10, Figure 6B indicating the force tending force to 11 e e d 1 (1 valve 104 fuel oil on the ordinate axi.s, the change of pressure oil is fed from from the, - fuel injection pump fue. 1 to lift tile needle valve body 103 arid the depress the. needle valve. body 103, Figure fiC indilicating the lift of the needle valve body 103, and Figure 6D indicating the change of the fuel injection rate. in each case plotted Pga-i-sz time.

As z--e delivered -fuel pressure rises from P toward P the force tending to lift. the needle valve body 103 rises from F t 0 F P, X (X The opposing spring force is set to be so that when the pressure exceeds P 4- he needle valve body 1C3 ascends and -,",le Dressure P,is also aoDlied to a lower surface of the needle valve 1-04, the force tending to lift the needle valve body 103 sharply increases to F 2 = P 1 X X. This accelerates the needle valve body 103 which lifts quickly from L 0 to L 1 until its upper end engages 'the upper end 101a of th.e bore 102. Here a delay between T and is due to the to accelerate the mass of zIne needle valve The :4-me taken body from -10 the force tending to lift- the needle valve body 103 remains larger th.an the soring (108) force as indicated by a full line of Figure 6B, and the needle valve body 103 retains maximum!ift.

When approaching the end of fuel injection, the pressure in the passage 110 reduces -to P,, and the force -:--ending to lift the needle valve body 103 is F x X, which becomes equa'to the force --- of 3 -L -..5 the soring 108 tending to depress the needle valve body 105.

As the fuel pressure decreases, the needle valve body 103 is lifted on the force of the spring 108, and when the nressure becomes P at a time T the force of th.e spring 108 increases F 3 as the needle valve body 103 lifts, however 3 -1 1 force 'lending to lift' the needle valve body 103 becomes F 1 = P 3 x X; lower than F 3 The needle valve body 103 lift becomes L 0 and the needle valve closes when the fuel pressure P (at the time of closing of the 3 1.04) becomes F,/X, the pressure P. a,:

of omening becomes lower than V, and fuel 4n.;ecll-i-on rate at the time of closinz needle valvE the time thus the reduced.

t In practice, the time taken to accelerate the of the needle valve body 103 creates a delay so that the valve closes not at time 1, 2 but at T 3 During this delay the pressure in the fuel passaze 110 further decreases to p 4 Accordingly, the fuel. injection rate proportional to the fuel passage internal pressure is minimised inevitably at the end of fucl injection as shown in Figure 6D..

However, fuel injected at n high rate a t the beginning of injection is burned quickly in the combustion chamber of the diesel engine to raise pressure, cause combustion noise or so-called diesel knock, raise the combustion maximum pressure rnise the combustion temperature accordingly, thus often producing noxious NOx.

Further, deterioration of the fuel injection rate nt the end of the injection period and the resultant increane in fuel injection time, and the coarse fuel spray caused by a decrease in injection pressure are capable of causing so-call.ed after-hurning, and thus 2 0 the imperfect combustion. This may not only cause noxious black smoke (CO, HG) but also redurr the thermal (Ifficiericy.

The acceleration delay might be shortened by lerr,(!liiti.g the mass- of the needle valve body 103 or increasing nn apparent spring constant by using an upper portion of the needle valve body 103 as a pressure accumulating chamber. However, such measures have not yet been made effective in improving performance stability.

One object of the present invention is to ensure a low initial fuel injection rate and to enhance the fuel injection rate toward the end of an injection cycle to shorten the fuel injection period, thereby decreasing NOx, CC) -and HC and enhancing thermal efficiency.

In necordance with the present invontion, we propose 3 5 a fuel injection valve having a seated valve for controlling the flow of fuel under pressure from a fuel supply passage to a fuel injection nozzle wherein the v,:tlve s coerable by a plunger biased towarn; a va-ve c-'cseand urged in the valve closing -,4-4reczion by the oressure acting in a pressure accumulating in communication via a throttle with the fuel, supply passage.

A preferred embodiment of fuel injection valve comprises a needle valve body serving as the plunger, with a needle valve for co-operation with a valve seat near a nozzle hole. The needle valve body nuns in a bore and the space within the bore on one side of 'he plunger (opposite to the needle valve), forms at least par.; of the Dressure accumulating chamber. A fuel massage communicazing with valve seat also communicates w-zh the mressure accumulating chamber through a which may be in the form of an axial groove extending axially of the plunger.

When the valve opens as 'he pressure in the -fuel passage rises at the beginning of fuel injection, fuel in the Dressure accumulating chamber is compressed as the needle valve body lifts. This reduces the opening velocity of -he needle valve body and the fuel injection rate is lowered. Thus, the heat generated in an engine combustion chamber during the initial stage of combustion is retarded, and 'he combustion Dressure is kecz from 2 55 r-is4ng.

When 'he valve closes at the end of a fuel 4-n.4ecz-.on cycle, pressure in the accumulating chamber is kept high by the fuel passage internal pressure through the throttles which is applied to an upper end of the needle valve body, -he needle valve of the needle valve body contacts with valve seat in co-operation with the spring, thus closing the valve. The fuel passage internal pressure at the time the valve begi-s to close is higher than that at the end of open'-5,,, and due to zhe increase In the fuel at -.he end of the valve closing, the parz-4c- l-- size e c41--i-4sz -njec-zed from the nozzle -n-. --he end J o f e 1 n j e c t -4 o n -- s n i m 4_ s e d n GI c c,-,, b u s z _ o n 1 s 1 Vurther, high pi:.errure injection at the time of v-.ilvc, closing enhancer, the fuel injection j,Rte suff'i(,jic-riLly to prevent after- burning, decrease. the exhaust of' blaCIC smol,,e, CO and HC, and further to enhnnr.e. a constallt volume of Sabathe cycle, thus improving the thermal. efficiency of the diesel engine.

Preferred embodiments of tile invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a longitudinal sectional view of a fuel.

injection valve; Figures 2A to D are performance curves for the valve of Figure 1; Figure 3 is a longitudinal sectional view of anol-her IC, fuel injection valve; Figure 4 is a fragmentary longritudinal sectional view of another fuel injection valve; Figure 5 is a longitudinal sectional view of a conventional fuel injection valve; arid Figures 6A Lo D are performance rurves for the valve of Figure 6.

With reference to Figure 1, a fuel injection valve body 1 comprises a valve body upper portion 2, and a valve body lower portion 4 held together with a press.ure accumulating rhamber cnvet, 5 therebetwnen by a nut 3 screwed onto the upper body portion 2, the upper end of which has screwed thereon a stopper 6.

Within a nose on the lower body portion 4 protruding from the nut 3 is formed a valve neat 8 and downstream 30thereof a nozzle 7. A needle valve body 1.21 co-oper.sting. with the seat 8 is slidable within a bore 10 farmed centrally of the lower body portion 4 and opening. into an application chamber 11 upstream of the valve sea', Thp needle valve body 12 carries a needle valve 14 having a sectional area A 2 for contRr.t with the valve spat. 8, the body or sliding part 13 having a v - is - seczional area A,, and a smaller diameter part 155 z-- L.

which a pushrod 16 is connected having a sectional area A, A stop hole 17 formed in the pressure accumulating chamber cover 5, co- axial with and communicating with the bore 10 in the lower body portion 4, receives the smaller diameter body part 15. An annular oressure accumulating chamber 18 defined between-the upper face 13a of the sliding part 13 of the needle valve body 12 and the lower face 5a of the cover 5, communicates via a throttle groove 19 formed on a side of the sliding part 13, with the application chamber 1-1.

Between the stopper 6 and a spring seat 20 carried by the push rod 16 is a spring 21 which biases the needle valve body 12 downward toward the valve closed Dosition (with the needle valve 14 in contact with the valve seat 8).

A fuel passage 22 through the pressure accumulating chamber cover 5, communicates with the fuel passage 9 in the valve body upper portion 4 and a fuel inlet passage 23 in upper body portion 2, for connection to a fuel injection pump (not shown). A leak hole 24 is Drovided in the stopper 6.

When fuel from a fuel injection pump (not shown) flows into the fuel passages 23, 22 and 9, pressure in the passage begins to rise from P 0 (Figure 2), the pressure in the pressure accumulating chamber 18 communicating with the application chamber 11 through the throttle groove of oressure rise in 18 is low (PO - p 2; When the internal o r c e - A- j when s h o...j n 19 also being P and the rate = 01 the pressure accumulating chamber dotted line in Figure 2).

fuel pressure reaches P-, -he ready for opening. The force f_= in Figure 2B acts against 7-e spring an internal pressure P- x zressure accumulazing chamber 18, -nnz needle valve 14:arts from c the valv (from the nozzle hole 7) commences.

At the instant the valve opens, the effective _area of the needle valve body 12 on which pressure acts increases to A, from (A 1 - A,), and thus the force tending to lift the needle valve body 12 increases to f 3 = p 1 x A 1 (Figure 23), so that ascent of the needle valve body 12 is accelerated by the force.4Lr' 3 The valve lift increases from period to 4,0 ti.

AS the lift increases, fuel in Ihe pressure accumula.-ng chamber 18 is compressed, the nressure increasing successively along the curve P- to P to P (Fiaure 3 4 2A), P 3 x (A 1 A 3 plus the force of the spring 21 becomes f 4 =; p x A 1 at the pressure P 3 midway of the lift (time t 1), and further lift of the needle valve body 12 is limited by the pressure rise in the pressure accumulating chamber 18. The lift of the needle valve body 12 at time t 1 is j 1 (Figure 2C), e seat 8 to open the valve, and j a to J 1 during the lift of the needle valve body 12 are small, the initial fuel injection rate is low as indicated by r 0 in Figure 2D.

When the pressure increases, the fuel in the pressure r 18 and the spring 21 are further compressed until P 6 x A 1 = f 6 = p 4 x (A 1 - A 3) + force f 7 of the spring 21 at time t., and when the pressure in the fuel passage exceeds P,, an upper end 15a of -he small diameter part 15 abuts the upper end 17a 30 Of the stop hole 17, to determine the maximum lift 2 in Figure 2C).

As shown in 7igure 2D, the fuel injection ---mze in from r, to in 'he period zII - t,,, but remains - -:ow ith the prior art -:'uel injection valves. s :he pressure 'n:ne --,-e'. passage ncreases -8 needle valve and pressure !-U also increases as shown the needle valve 1-1 remains open. fuel in -- he appl-Lcaziion chamber 11 a.LE' tne fuel passage 9 is fed into the pressure accumulating chamber 18 through throttle groove 19, so that the in Filcure 25, o.a e v -- r, h i z 1- - pressure in the pressure accumulating chamber 1-8 continues to rise, even after the pressure in the fuel Passage begins to decrease as the fuel injection end approaches.

The force tending to open the needle valve 14 is balanced by the force tending to close the valve at time 11. 31 the force tending to open the valve being given by p x A-, and the force tending to close the valve 7 being P X iIA A plus:;he force of the spring 21 at the 8 - 3 time of full lift the pressure in the fuel so the lift of the needle The valve-closing start comDared with the known Accordingly, as passage decreases further valve body 12 decreases. pressure P 7 is very high as prior art for the internal pressure P 8 of the pressure accumulating chamber

Since the pressure in the accumulating chamber 1 and the spring 21 depress the needle valve body 12 continuously the volume of the press chamber 18 increases, chamber 18 decreases, and the the needle valve 14 also decrease The needle valve 14 closes at tending to open the needle valve the force tending to close the plus the force of the spring 21 at closing f, - 'L, = f9Y Z - t due to the time of the needle valve 14 a point t. in time.

then drops as low as start pressure P- and 1-, are very hiah as valves, by v-4rzue of chamber 1-8 and the 1 18.

8 the mressure ir force ure accumulating -he accumulating tending to open 47 when zhe force 14 P 9 x A 1 =:E balances valve P 10 x (A1 A 3 the time of full however there is a delay (t 4 taken to accelerate the mass and thus the valve closes The pressure in the fuel p li However, the valve-closing the valve- closing end pressure with at passage compared c--nvenz4-onal oroviding z,-e oressure throttle zroove 19, the accumulat4na _z -g- be in g not only minimisarion of the particle size c. the fuel mist during the fuel injection end oer-4od but also an enhancement of the fuel inJection rate.

After the end of fuel injection, the pressure of fuel in the accumulating chamber 18 continues to a drop as shown in Figure 2A, to the pressure P 0 of -fuel n the fuel passage - the pressure before the fuel injection starts at time t. 6 - in readiness for the next fuel injection cycle.

Other embodiments shown in Figures 3 and 4 (wherein equivalent reference numerals are used) have no pressure accumulating chamber cover 5 and the needle valve body 12 does not have a small diameter part equivalent zo Dart 15 in Figure 1.

The valve body upper portion 2 is in direct contact with the valve body lower portion 4 and is coupled thereto by the nut 3. The pressure accumulating chamber 18 is formed by the space between an upper surface of the sliding part 13 of the needle valve body 12 and a lower surface 2a of the valve body upper portion 2, the annular space, the pushrod 16 and a hole 25 through which it passes and of a chamber 26 containing a square section spring 25 and the spring seat 20.

Also, instead of the throttle groove 19 in Figure 1, a throttle 27 is formed between the fuel passage 23 and the insertion hole 25.

An air vent valve 28 is screwed into the leak hole 24 formed on the stopper 6 which has a central projection 6a forming an abutment determining the maxi-mum lift, the clearance d being smaller than the distance between the upper surface 13a of the sliding part 13 of the needle valve body 12 and the lower surface E2a of the valve body upper portion 2 when the needle valve 14 s closed. Thus, the upper end 1-3a c--" the needle valve body 12 is always subject to the pressure c-.:' fuel in 7he pressure accumulating c-amber 18, even needle valve 14 lift.

at Maximum -io- The embodiment of' Figure 1 -'s basically similar -:o that of Figure 3 except that the spring 21 is circular in section and that a needle valve 30 movable bv a screw 29 is provided for adjusting the effective flow area of the leak hole 241. in the embodiments of Figure 3 and Figure 4 when fuel oil is fed from the fuel injection pump and the pressure in the fuel passage rises from P 0 to P 1, fuel flows through the throttle 27 and the pressure in the pressure accumulating chamber 18 also rises from P 0 to P 2 as described above with reference to Figure 2.

area) of the needle - A) to A,, so that e v nd e by -he force tending to open the valve is f, = P, x (A 1 - A,,) as shown in Figure 23, is opposed by the pressure in the pressure accumulating chamber 18 acting on the upper surface of the sliding part 13 (P 2 x A 1) and a spring force t 1 f 2 When the pressure in the fuel passage exceeds P 4- he needle valve 14 lifts from the valve seat 8, and fuel injection from the nozzle hole 7 begins.

Instantaneously, the effective (pressure receiving valve body 12increases from (A, 2 the force tending to lift the P x A, needl alve body 12 increases to f 3 2B) a as the needle valve body 1-2 lifts it, is accelerated -"h force.0 11 3 As lift. of the needle valve body 12 increases, so fuel in the pressure accumulating chamber 18 is compressed to increase the pressure as shown in Figure 2A. When at half lift the pressure reaches P 3 (at f4 f 5 of P 3 x A 1 + force of the spring 21, is balanced by the force tending to open the needle valve 14 (Or, x A,) and an increase in the lift of -.he.needle valve body 12 is limited.

When the Dressure in the fuel passage P-, the fuel J.-,i the pressure accumulazing and the =_Dring 21 are fur:her compressed p x A, until an upper end of the spring seat 20 comes 4n contac-with the or04ection 6a at maximum lift (L of Figure J force f of the sDring 21 at time z_), 7 The pressure in the fuel passage then increases as shown in Figure 2A, so that force tending to open the needle valve 14 also increases as shown in Figure 2B, and the needle valve 14 remains opening. However, high-pressure fuel in the fuel passages 23, 22, 9 is fed into the pressure accumulating chamber 18 through the throttle 27, so maintaining a high pressure in the pressure accumulating chamber 18.

Even after zhe fuel passage internal pressure begins to drop as the end of fuel injection approaches the oressure in the pressure accumulating chamber 18 con to rise. At time t 3 the force f 8= p 7 x A 1 tending to open the needle valve 14 is balanced by the -force tending to close the valve (P 8 x A 1 + force of the spring 21 at the ime of full lift ú 7 = f 8), and as the pressure in the fuel passage drops thereafter so the lift of the needle valve body 12 reduces. Thus the spring 21 depresses the needle valve body 12, increasing the volume of the nressure accumulating chamber 18 to ooen the needle valve 14 also continues to reduce.

The needle valve 14 is to close at time t 4 when the force to open the needle valve 14 (P 3 x A 1 = f 9 is balanced by;the force to close (P 10 x A, plus force of the spring 21 at the time of full close f 1 - f 2 f 9 however, a delay arises due to the time taken to accelerate the mass of the needle valv the valve in f accumulating chamber 1-8 continues to the _hrottle 97 to ecualise with the passage and as shown in 7igure P at time t 6 in the embodimentof Figure 4 pre 0 fuel in th flow e 14, and pressure out through pressure in the 2A, iz drops to sure in the pressure accumulating chamber 18 can be regulated by the needle valve 30 thus enabling adjustment of 'he fuel injection valve according to the operating state of an engine.

As described above, the invention comprises disposing a needle valve body with a needle valve coming in contact with valve seat nearby a nozzle hole and its upper end depressed downward by a valve spring in a sliding hole perforated in a valve body lower portion, forming a pressure accumulating chamber over the needle valve lo body, leading fuel passage communicating with the valve seat into the pressure accumulating chamber through a throttle, therefore a fuel injection raze at a fuel injection beginning will be moderated, thus a heat generation is suppressed to combustion in a diesel engine combustion chamber, a combustion pressure is kept from rising and a noise is also suppressed, and NOx will be less produced.

Further, the invention has advantages in that the fuel injection rate at the end of an injection cycle is enhanced, the fuel injection period is shortened -er-burning in the combustion of at the same time, aft diesel engine is avoided, there is a decrease in the black smoke, CO and HG exhausted and an improvement in thermal efficiency. Furthermore, the fuel injection -ure and obtainab valve of the invention is simple in struct at a moderate cost.

A 1 e

Claims

1. A fuel injection valve having a seated valve for controlling the flow of fuel under pressure from a fuel supply passage to a fuel injection nozzlepherein the valve is operable by a plunger biased toward a valve cloged position, and urged in the valve closing direction by the pressure acting in a pressure accumulating chamber in communication via a throttle with the fuel supply passage.

2. A valve according to claim 1 wherein the arrangement is such that in use, fuel supply pressure acts on one side of the plunger in the sense to open the seated valve and in opposition to bias, and that the pressure in the pressure mccumulating chamber acts on the other side of the plunger.

is

3. A valve according to claim 1 or claim 2 wherein the throttle is in the form of a groove extending axially of the plunger to communicate between opposite sides thereof.

4. A vnlvp according to any one of claims 1 to 3 comprising a needle valve cooperating with a valve scat and carried by a needle valve body that is slidable in a bore to form the said plunger, the needle valve being smaller in diameter than the body and extending into a chamber communicating with the fuel supply passage upstream of the valve scat.

5. A valve according to any one of the preceding claims wherein the space within the bore on a side of the plunger opposite to the valve forms at least a part of the pressure accumulating chamber.

6. A valve according to any one of the preceding claims comprising an abutment limiting maximum lift of the valve.

7. A fuel injection valve constructed and arranged' subntantially as hereinbefore described with reference 35to and as illustrated in Figures 1 and 2, Figure 3 and/or Figure 4 of the accompanying drawings.

Published 1990 at The Patent Office. StateHouze.6671 High liolborn. LondonWC1R4TP.PurLheroopica maybe obedtmm The Patent Office Wes Er. St Mary Crav. OrDinewn. Sent SP.5 3RD. P=ted by Mulupex techWques It& 51 Mary Cray, Kent. Con. 1187