Fuel-Injection Pump for Turbocharged Diesel Engine

Europaisches Patentamt J European Patent Office © Publication number: 0 645 534 A1 Office europeen des brevets

EUROPEAN PATENT APPLICATION

@ Date of filing: 27.09.94

® Priority: 28.09.93 JP 263055/93 Saimata Pref. (JP) Inventor: Kato, Hiroaki, c/o Zexel Corp. @ Date of publication of application: Higashi-Matsuyama Fact. 13-26, 3-chome, 29.03.95 Bulletin 95/13 Yakyu-cho Higashi-Matsuyama City, © Designated Contracting States: Saimata Pref. (JP) DE GB Inventor: Yashiro, Hidekatsu, c/o Zexel Corp. Higashi-Matsuyama Fact. 13-26, 3-chome, © Applicant: ZEXEL CORPORATION Yakyu-cho 6-7, Shibuya 3-chome, Higashi-Matsuyama City, Shibuya-ku Saimata Pref. (JP) Tokyo (JP)

@ Inventor: Tanaka, Noritoshi, c/o Zexel Corp. © Representative: Patentanwalte Grunecker, Higashi-Matsuyama Fact. 13-26, 3-chome, Kinkeldey, Stockmair & Partner Yakyu-cho Maximilianstrasse 58 Higashi-Matsuyama City, D-80538 Munchen (DE)

© A fuel-injection pump for a turbocharged diesel FIG. 1 T0I3 engine not equipped with a boost compensator is able to suppress the generation of black smoke when the engine is subjected to sudden acceleration from a low-speed state, or to low speed, high load operation, by reducing the fuel injection quantity. The pump comprises a plunger barrel (24) in which are formed intake and exhaust ports (32,33) that communicate with a fuel reserve chamber (30), said intake and exhaust ports (32,33) being constituted by a large diameter main port (32) and a small diameter sub-port (33) arranged so that the upper edge of the sub-port (33) is not above the upper edge of main port (32), a plunger (25) disposed within the plunger barrel inclined lead formed the 00 (24), an (35) being on plunger (25) at a position that permits communication with the intake and exhaust ports (32,33), an upper sub-lead (36) being formed on the head por- CO tion of the plunger (25) that is able to communicate with the sub-port (33) over a prescribed range of rotation by the plunger (25), and which permits the sup-port (33) to communicate with the upper sub- lead (36) even when the main port (32) is closed by the upper edge of the plunger (25).

Rank Xerox (UK) Business Services (3. 10/3.09/3.3.4) EP 0 645 534 A1

FIG.2

2 1 EP 0 645 534 A1 2

BACKGROUND OF THE INVENTION ment, a device known as a boost compensator (not shown) was used to control the relationship be- Field of the Invention tween turbocharger 4 boost pressure, and pump speed N and injection quantity Q. The present invention relates to a fuel injection 5 Specifically, with reference to Figure 9, the pump for a diesel engine fitted with a turbo-charg- boost compensator suppresses the emission of er, and more particularly to a fuel-injection pump black smoke during low-speed operation by reduc- for a turbocharged diesel engine that has an injec- ing injection quantity Q (refer to the "Zone of tion compensation mechanism. injection quantity control by boost compensator" in io Figure 9). That is, when the boost pressure pro- Description of the Prior Art vided by the turbocharger 4 is low, the boost compensator limits the generation of black smoke In a turbocharged diesel engine, exhaust gas to a certain level by setting the control rack posi- from the combustion chamber (engine cylinder) is tion R further in. used to compress intake air which is then supplied 75 However, in the case of turbocharged diesel to the engine to increase the power of the engine. engines not equipped with a boost compensator, In a conventional turbocharged diesel engine, particularly turbocharged diesel engines used for changes in the boost pressure provided by the industrial applications, the injection quantity Q be- turbocharger is a function of the fuel injection comes excessive and all turns into black smoke, pump speed in rpm (N) and injection quantity or 20 creating a major problem with respect to engine load (Q). evaluation. Furthermore, most turbocharged diesel A conventional turbocharged diesel engine will engines 1 are small units. In order to newly equip now be described briefly, with reference to Figure such engines with a boost compensator, it is nec- 7. In Figure 7, a turbocharged diesel engine 1 has essary to alter the linkage (not shown) used for the a engine body 2, a piston 3, a turbocharger 4, a 25 governor 5. Also, in the case of turbocharged die- governor 5 and a fuel injection pump 6. A crank- sel engines in which the governor 5 is not directly shaft 8 is turned by the reciprocating movement of connected to the fuel injection pump 6 but is the piston 3 in a combustion chamber 7. The provided on the engine side, the limited space also turbocharger 4 uses the exhaust gas from an ex- makes it difficult to fit a boost compensator. haust manifold 9 to compress intake air, and the air 30 This has produced a demand for a means of thus compressed is delivered to the combustion solving the problem of black smoke generated dur- chamber 7 via an intake manifold 10. ing sudden acceleration from a low idle condition in The governor 5 controls the fuel injection quan- turbocharged diesel engines that do not have a tity in accordance with the speed (rpm) of the boost compensator and cannot readily be fitted turbocharged diesel engine 1. The fuel injection 35 with such a boost compensator. pump 6 has a camshaft 1 1 driven by the crankshaft 8, an injection pipe 12, and an injection nozzle 13 SUMMARY OF THE INVENTION arranged in opposition to the combustion chamber 7. One method that is commonly used to evaluate An object of the present invention is to provide the performance of an engine such as the tur- 40 a fuel-injection pump for a turbocharged diesel bocharged diesel engine 1 consists of measuring engine that is not equipped with a boost com- the level of black smoke that is generated when the pensator, and which by reducing the fuel injection engine is subjected to sudden acceleration from a quantity is able to suppress the generation of black low idle. However, a problem with the diesel engine smoke when the engine is subjected to sudden 1 is that sharply accelerating the engine from a low 45 acceleration from a low-speed state, or to low idle causes an excessive quantity of fuel to be speed, high load operation. injected and black smoke to be produced. This is In accordance with the present invention, the explained below. above object is attained by, instead of the de- The graph of Figure 8 shows the relationship scribed boost compensator, a fuel-injection pump between pump speed N (or engine speed) and 50 for a turbocharged diesel engine that uses a plung- injection quantity Q. In the graph, the relationship er having a preflow effect, said fuel injection pump in the case of an engine that does not have a comprising a turbocharger, a piston driven by com- turbocharger 4 is indicated by a broken line, while bustion in a combustion chamber of intake air the higher injection quantity Q of the engine 1 supercharged by the turbocharger, a crankshaft equipped with the turbocharger 4 is indicated by a 55 rotated by the driving of the piston, a governor able solid line. Injecting more than the proper quantity to control a fuel injection quantity in accordance of fuel during low-speed operation causes black with a differential between a rotational speed of the smoke to be produced. In a conventional arrange- crankshaft and a set target rotational speed, a

3 3 EP 0 645 534 A1 4 pump housing, a cam driven by rotation of the BRIEF DESCRIPTION OF THE DRAWINGS crankshaft, a plunger barrel that is affixed to the pump housing and in which are formed intake and Figure 1 is a vertical cross-sectional view of an exhaust ports that communicate with a fuel reserve embodiment of the fuel-injection pump for a chamber, said intake and exhaust ports being con- 5 turbocharged diesel engine according to this stituted by a large diameter main port and a small invention; diameter sub-port arranged so that the upper edge Figure 2 is a vertical cross-sectional view of the of the sub-port is not above the upper edge of the main parts of portion II of Figure 1; main port, a plunger disposed within the plunger Figure 3 shows details of the leads at the top barrel that can be moved reciprocally by the cam io part of the plunger; and rotated by a control rack operated in conjunc- Figure 4 is a vertical cross-sectional view to tion with the governor, an inclined lead formed on illustrating the operation of the pump during low- the plunger at a position that permits communica- speed operation; tion with the intake and exhaust ports, an upper Figure 5 is a vertical cross-sectional view illus- sub-lead formed on the head portion of the plunger 15 trating the operation of the pump during high- that is able to communicate with the sub-port over speed operation; a prescribed range of rotation by the plunger, and Figure 6 is a graph of the N-Q characteristics of which permits the sub-port to communicate with the pump provided with a preflow effect plunger; the upper sub-lead even when the main port is Figure 7 shows the arrangement of a conven- closed by the upper edge of the plunger, and a 20 tional turbocharged diesel engine; fuel pressure chamber formed between the plunger Figure 8 is a graph showing the relationship and the plunger barrel into which fuel is sucked in between pump (or engine) rotational speed N from the fuel reserve chamber and delivered under and fuel injection quantity Q; and pressure by the reciprocating movement of the Figure 9 is a graph showing the relationship plunger. 25 between pump (or engine) rotational speed N Thus, the fuel-injection pump for a turbochar- and fuel injection quantity Q when a boost com- ged diesel engine has a plunger barrel in which are pensator is used to suppress the generation of formed a large diameter main port and a small black smoke at low rotational speed by reducing diameter sub-port, and a plunger in which is injection quantity Q. formed an upper sub-lead able to communicate 30 with the sub-port. DESCRIPTION OF THE PREFERRED EMBODI- By employing a plunger barrel with a main port MENT and a sub-port and a plunger with an upper sub- lead, utilizing the fuel throttling effect of the upper An embodiment of a fuel injection pump 20 sub-port at high engine speeds and, with the con- 35 according to this invention will now be described trol rack set at the same position, reducing the fuel with reference to Figures 1 to 6. Parts that are the injection quantity at low speeds, the fuel-injection same as in Figure 7 have been given the same pump according to this invention can provide the reference symbols, and further details thereof are same functionality as a boost compensator, and omitted. therefore can improve engine performance without 40 Figure 1 is a cross-sectional view of the fuel- any changes to the principle parts of conventional injection pump 20 for a turbocharged diesel engine, diesel engines or fuel injection pumps. and Figure 2 is a cross-sectional view of the main Moreover, while in the case of a boost com- parts of portion II of Figure 1. The fuel injection pensator, reducing the fuel injection quantity at low pump 20 has a pump housing 21 , a cam 22 affixed speeds is effected mechanically by controlling the 45 to a camshaft 11 (Figure 7), an injection quantity position of the control rack, with the pump of this control rack 23, a plunger barrel 24, a plunger 25, a invention, the injection quantity characteristics can delivery valve 26 and a delivery valve holder 27. be adjusted based on the difference between the The cam 22 is driven via the camshaft 1 1 by a static effective stroke (low speed) and dynamic crankshaft 8 of a diesel engine 1, thereby causing effective stroke (high speed) with a fixed control 50 the plunger 25 to be reciprocated vertically via rack position. tappet roller 28. The control rack 23 is linked to the Further features of the invention, its nature and accelerator (not shown) via governor 5 (Figure 7). various advantages will become more apparent Moving the control rack 23 in a direction normal to from the accompanying drawings and following de- the drawing sheet via control sleeve 29 rotates the tailed description of the invention. 55 plunger 25 axially through a prescribed angle. The plunger barrel 24 is fixed within the pump housing 21 to which it is attached. The plunger 25 is accommodated inside the plunger barrel 24 so that

4 5 EP 0 645 534 A1 6 the plunger 25 can reciprocate and rotate therein. of the plunger 25 and the upper edge 36A of the A fuel reserve chamber 30 is defined by the plung- upper sub-lead 36, and delivery of the fuel stops er 25 and the pump housing 21, and the space when the main port 32 aligns with the inclined lead between the plunger barrel 24 and the delivery 35. valve 26 forms a fuel pressure chamber 31 . 5 That is, the stroke of the plunger 25 from As shown enlarged in Figure 2, formed in the bottom dead center to the start of fuel delivery is a plunger barrel 24 are a main port 32 and a sub-port prestroke. The depth or height of the upper sub- 33 through which fuel is drawn in and expelled. lead 36 is preflow stroke L1. The stroke from the The upper edge 32A of the main port 32 and the closing of the sub-port 33 to the opening of the upper edge 33A of the sub-port 33 are formed at io main port 32 is static (low speed operation) effec- the same height or horizontally at the same posi- tive prestroke L2, and the stroke from the closing tion and separated in the circumferential direction to the opening of main port 32 is dynamic (high by 180 degrees. The main port 32 and sub-port 33 speed operation) effective stroke L3. may also be formed so that the upper edge 33A is When the engine is under normal load opera- lower than the upper edge 32A. Fuel from the fuel 15 tion, the main port 32 is opposite the upper edge reserve chamber 30 is sucked in by the reciproca- 25A of the plunger 25 and the sub-port 33 is tion of the plunger 25 in the plunger barrel 24 and opposite the upper sub-lead 36. At idling and other compressed in the fuel pressure chamber 31. low speed operation, the position of the main port When the delivery valve 26 opens, the fuel is 32 is further to the left relative to the inclined lead delivered under pressure via injection pipe 12 (Fig- 20 35 shown in Figure 3, reducing the effective stroke, ure 7) to the injection nozzle 13. and as shown in Figure 4, the sub-port 33 is in Figure 3 is a diagram of the leads at the top alignment with the upper sub-lead 36, so the deliv- part of the plunger 25, showing the mutual posi- ery of fuel substantially starts when the sub-port 33 tional relationship between the main port 32 and is closed by the upper edge 36A of the upper sub- sub-port 33. Formed in the top part of the plunger 25 lead 36. 25 are a vertical fuel passage 34 that commu- When the rotational speed is increased during nicates with the pressure chamber 31, an inclined high speed operation the main port 32 is shifted to lead 35 that communicates with the vertical fuel the right of the inclined lead 35, increasing the passage 34, and an upper sub-lead 36 that com- effective stroke, and as shown in Figure 5, as the municates with the pressure chamber 31 . 30 throttling effect of the sub-port 33 causes fuel de- As shown in the drawing, the upper sub-lead livery to start before the sub-port 33 is completely 36 can oppose the sub-port 33 from normal load to closed by the upper edge 36A of the upper sub- startup, and the main port 32 can oppose the upper lead 36 (the prestroke effect), fuel injection timing edge 25A of the plunger 25. Here, normal load is advanced. encompasses a range of operation extending from 35 Figure 6 is a graph of the N-Q characteristics low speed operation such as idling, to high speed of the pump 20 with this preflow effect plunger 25. operation and high idling (reduction of fuel injection With the preflow effect plunger 25, the above func- quantity by the governor 5 when high speed, high tion results in the N-Q characteristics indicated in load rated rotational speed zone is exceeded), un- Figure 6 by the solid lines rising to the right (with der high loads and low loads other than at startup. 40 the control rack 23 at the same position, injection With respect to Figure 3, as the plunger 25 is quantity increases at the high speed side). The vertically reciprocated within the plunger barrel 24 broken lines indicate the results obtained with a by the action of the cam 22, the upper sub-lead 36, conventional plunger not having an upper sub-lead vertical fuel passage 34 and inclined lead 35 are 36. shifted vertically relative to the fixed-position main 45 Thus, the fuel injection pump 20 has a fuel port 32 and sub-port 33. Also, the rotation of the injection quantity suppressing effect that is the plunger 25 in the plunger barrel 24 by the action of equivalent of the injection quantity suppressing ef- the control rack 23 shifts the upper sub-lead 36, fect provided by a boost compensator, as indicated vertical fuel passage 34 and inclined lead 35 hori- by the "Zone of injection quantity control by boost zontally relative to the main port 32 and sub-port 50 compensator" in Figure 9. Especially when rota- 33. tional speed is increased by sudden acceleration In the fuel injection pump 20 thus configured, from a low idle, the fuel injection pump 20 can when the plunger 25 descends, fuel in the fuel prevent the generation of black smoke caused by reserve chamber 30 is sucked into the pressure an excessive quantity of fuel injection by holding chamber 31 via the main port 32 and sub-port 33. 55 the fuel injection quantity to the appropriate level. When the plunger 25 ascends, fuel compression Moreover, there is the advantage that simply by begins from the point at which the main port 32 replacing the plunger and plunger barrel, a conven- and sub-port 33 are closed by the upper edge 25A tional fuel injection pump can be given this black

5 7 EP 0 645 534 A1 8 smoke generation prevention effect without altering 2. A fuel injection pump according to claim 1, the basic pump arrangement. wherein there is provided no boost compensa- In accordance with the invention described tor in which, when the boost pressure pro- above, a plunger having an upper sub-lead for a duced by the turbocharger is low the fuel in- sub-port is used instead of a boost compensator. 5 jection quantity is limited by inserting the con- The plunger be used in place of a standard plung- trol rack further in. er, whereby it enables the generation of black smoke to be kept to a low level without any exter- 3. A fuel injection pump according to claim 1, nal change to the fuel injection pump or diesel wherein the main port is able to communicate engine. Thus, the boost compensator can be omit- io with the inclined lead over a prescribed range ted and the governor linkage therefore simplified. of rotation by the plunger.

Claims

1. A fuel-injection pump for a turbocharged diesel w engine, characterized in that said fuel injection pump comprises: a turbocharger, a piston driven by combustion in a combustion chamber of intake air supercharged by 20 the turbocharger, a crankshaft rotated by the driving of the piston, a governor able to control a fuel injection quantity in accordance with a differential be- 25 tween a rotational speed of the crankshaft and a set target rotational speed, a pump housing, a cam driven by rotation of the crankshaft, a plunger barrel that is affixed to the pump 30 housing and in which are formed intake and exhaust ports that communicate with a fuel reserve chamber, said intake and exhaust ports being constituted by a large diameter main port and a small diameter sub-port ar- 35 ranged so that the upper edge of the sub-port is not above the upper edge of the main port, a plunger disposed within the plunger barrel that can be moved reciprocally by the cam and rotated by a control rack operated in con- 40 junction with the governor, an inclined lead formed on the plunger at a position that permits communication with the intake and exhaust ports, an upper sub-lead formed on the head 45 portion of the plunger that is able to communicate with the sub-port over a prescribed range of rotation by the plunger, and which permits the sub-port to communicate with the upper sub-lead even when the main port is 50 closed by the upper edge of the plunger, and a fuel pressure chamber formed between the plunger and the plunger barrel into which fuel is sucked in from the fuel reserve chamber and delivered under pressure by the recipro- 55 eating movement of the plunger.

6 EP 0 645 534 A1

FIG. 1 EP 0 645 534 A1

3 EP 0 645 534 A1

FIG. 3

36 36A

3REF LOW STROKE L1

VMA11C (A I LOW SPEED) EFFECTIVE STROKE L2

IYNAMIC (AT HIGH SPEED) iFFECTIVE STROKE L3 EP 0 645 534 A1

FIG.4 FIG.5

10 EP 0 645 534 A1

FIG. 6

CONVENTIONAL THIS INVENTION CONTROL RACK POSITION

a HIGH LOAD

6— LOW LOAD

CAMSHAFT SPEED (rpm)N

11 EP 0 645 534 A1

FIG. 7

12 tr U D43 A I

FIG. 8

FIG. 9

ONE OF INJECTION QUANTITY CONTROL BY I00ST COMPENSATOR 1 . WITH TURBOCHARGER HAVING /T NO BOOST COMPENSATOR Patent Number European EUROPEAN SEARCH REPORT Application Office EP 94 11 5201

DOCUMENTS CONSIDERED TO BE RELEVANT Citation of document with indication, where appropriate, Relevant CLASSIFICATION OF THE Category of relevant passages to claim APPLICATION (lnt.CI.6) US-A-2 361 817 (B. BOLLI ET AL) 1,3 F02M59/26 * page 3, right column, line 71 - left column, line 21; figures 1.6A-6D *

US-A-4 512 307 (T. IGASHIRA ET AL) * column 2, line 12 - line 47; figures 1-3

TECHNICAL FIELDS SEARCHED (lnt.CI.6) F02M

The present search report has been drawn up for all claims Place of tearch Dale of coMpletiM of the tearch THE HAGUE 27 December 1994 Hakhverdi, M CATEGORY OF CITED DOCUMENTS T : theory or principle underlying the invention E : earlier patent document, but published on, or X : particularly relevant if taken alone after the filing date Y : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons A : technological background O : non-written disclosure & : member of the same patent family, corresponding P : intermediate document document