Safety Valve for Fuel Injection Apparatus

Europaisches Patentamt European Patent Office © Publication number: 0 466 081 A1 Office europeen des brevets

EUROPEAN PATENT APPLICATION

@ Date of filing: 08.07.91

© Priority: 09.07.90 JP 182410/90 © Applicant: NIPPONDENSO CO., LTD. 1-1, Showa-cho @ Date of publication of application: Kariya-shi Aichi-ken(JP) 15.01.92 Bulletin 92/03 @ Inventor: Kariya, Yasuhiro © Designated Contracting States: Sharuman Hausu 203, 34-11, Higashitoyoda DE FR GB IT 2-chome Hino-shi(JP)

© A safety valve (3) provided in a fuel injection to maintain a pressure for pressing the valve ele- apparatus including an accumulator (1) in which fuel ment (36) in a valve-opening direction, wherein the is accumulated, comprises: a housing (30) having an high-pressure fuel from the inside passage (31) is inside passage (31) for introducing the high-pressure introduced into the fuel chamber (39) when the valve fuel of the accumulator (1) into the inside of the body (37) of the valve element (36) is separated housing (30) and a seat face (32) formed at a portion from the seat face (32). With this safety valve (3), of the inside passage (31); a valve element (36) the high-pressure fuel of the accumulator (1) is intro- provided movably within the housing (30) and includ- duced into the fuel chamber (39) in order to press ing a valve body (37) to open/close the seat face the valve element (36) in the valve-opening direction (32); an elastic member (38) for pressing and biasing so that the valve element (36) will be rapidly opened, the valve element (36) in a closing direction; and a with the result that the fuel pressure in the accu- fuel chamber (39) defined between the inner surface mulator (1) can recover a predetermined value in- of the housing (30) and the valve element (36) so as stantaneously. < F I G. 00 o CO CO

Rank Xerox (UK) Business Services 1 EP 0 466 081 A1 2

BACKGROUND OF THE INVENTION Therefore, the present invention is intended to provide a safety valve of a fuel injection apparatus Field of the Invention which can obtain a property of a large flow rate after the valve is opened and which can constantly The present invention relates to a safety valve 5 maintain the pressure in an accumulator to be not of an accumulator in a fuel injection apparatus of a higher than a critical pressure. diesel engine for injecting high-pressure fuel accu- It is a further object of the invention to provide mulated in the accumulator by means of an injector a safety valve which enables the fail-safe system to of an electronic control type provided in each cyl- function favorably at the time of a trouble by regu- inder. io lating a clearance between the inner peripheral surface of a small-diameter section and the outer Description of the Prior Art peripheral surface of a valve element so as to set the increased fuel pressure in the accumulator to a There has been conventionally known a fuel predetermined value. injection apparatus, as disclosed in Japanese Pat- 75 Another object of the invention is to provide a ent Unexamined Publication No. 59-165858, which safety valve which enables the fuel pressure in the is arranged in such a manner that high-pressure accumulator to recover a predetermined value in- fuel is accumulated in an accumulator called a stantaneously by opening the valve rapidly once it common rail by a high-pressure supply pump, and reaches a valve-opening pressure. the high-pressure fuel of the accumulator is in- 20 jected by an injector of an electronic control type BRIEF DESCRIPTION OF THE DRAWINGS provided in each cylinder. This fuel injection apparatus is provided with a Figs. 1 to 4 relate to one embodiment of a safety valve which is opened for releasing the fuel safety valve according to the present invention: when a pressure in the accumulator exceeds a 25 Fig. 1 is a cross-sectional view showing the predetermined value. whole structure of the safety valve; As shown in Fig. 5, the structure of the conven- Fig. 2 is a schematic view showing the entire tional safety valve is such that a tapered seat face system of a fuel injection apparatus including 32 which is an opening portion of a passage 31 in the safety valve applied to the present embodi- communication with the accumulator is 30 ment; opened/closed by a ball valve 37, and that when Fig. 3 is an enlarged fragmentary view of a the fuel pressure in the accumulator exceeds a portion enclosed by a circle line III in Fig. 1; and biasing force of a spring 38 which presses and Fig. 4 is an operational characteristic graph of biases the ball valve 37 in a valve-closing direction, the safety valve. the ball valve 37 is opened to release the fuel of 35 Figs. 5 and 6 relate to a prior art concerning the the accumulator to the low pressure side, thereby present invention: suppressing an increase of pressure in the accu- Fig. 5 is a cross-sectional view showing the mulator. whole structure of the conventional safety valve; With this structure, however, an area of an and opening after the ball valve 37 is opened is insuffi- 40 Fig. 6 is an operational characteristic graph of cient. Consequently, even after the fuel has been the safety valve. once released through the opened valve, there is a risk that the pressure in the accumulator is in- DETAILED DESCRIPTION OF THE PREFERRED creased to exceed a valve-opening pressure of the EMBODIMENT ball valve 37 when the fuel is pressurized and 45 delivered again. Particularly when the fuel of a One embodiment of the present invention will maximum flow rate Qmax is pressurized and deliv- be hereinafter described with reference to the at- ered from the high-pressure supply pump to the tached drawings. accumulator, there is a risk, as shown in Fig. 6, that Referring to Fig. 2, fuel supplied from a fuel the fuel pressure is increased to exceed not only 50 tank (not shown) is pressurized and delivered the valve-opening pressure Po but also a critical through a conduit via a delivery valve by means of internal pressure PE of an accumulation piping. a high-pressure supply pump 2 such as a priming pump, and accumulated in an accumulation cham- SUMMARY OF THE INVENTION ber of an accumulator 1 which is called a common 55 rail. It is an object of the present invention to pro- The high-pressure fuel accumulated in the ac- vide a fuel injection apparatus capable of prevent- cumulation chamber of the accumulator 1 is in- ing an abnormal increase of a fuel pressure. jected into an internal combustion engine through

2 3 EP 0 466 081 A1 4 an opened nozzle hole when a nozzle needle hav- 33, and when the pressure PR is set to a minimum ing a distal-end portion to open/close the nozzle value which the pressure in the accumulator 1 is hole is biased in a valve-opening direction by a required to have for operating the engine, the fail- pressure of the fuel supplied through a check valve safe and limp-home system can be functioned fa- and a passage in an injector of an electronic con- 5 vorably at the time of a trouble. trol type (not shown) provided in each cylinder. According to the present invention, as de- At an end portion of the accumulator 1 , there is scribed heretofore, when the valve body of the provided a safety valve 3 for controlling the fuel valve element is separated from the seat face, the pressure in the accumulator 1 so as to prevent it high-pressure fuel introduced from the inside pas- from exceeding a critical value. io sage flows into the fuel chamber, and the pressure As shown in Figs. 1 and 3, the safety valve 3 in this fuel chamber presses the valve element in comprises: a housing 30 which includes an inside the valve-opening direction so that the valve ele- passage 31 in communication with the accumulator ment will be rapidly opened, with the result that the 1, a tapered seat face 32 formed at an opening fuel pressure in the accumulator can recover a portion of the inside passage 31 , a small-diameter is predetermined value instantaneously. section 33, a spring chamber 34 and a low-pres- A safety valve provided in a fuel injection ap- sure passage 35 in communication with a fuel tank paratus including an accumulator in which fuel is 4 on the low pressure side of the safety valve; a accumulated, comprises: a housing having an in- valve element 36 provided movably within the side passage for introducing the high-pressure fuel housing 30, with a ball valve 37 to open/close the 20 of the accumulator into the inside of the housing seat face 32 being fixed on this valve element; and and a seat face formed at a portion of the inside a spring 38 which presses and biases the valve passage; a valve element provided movably within element 36 in a valve-closing direction. The valve the housing and including a valve body to element 36 is closely fitted in the small-diameter open/close the seat face; an elastic member for section 33 of the housing 30, and a fuel chamber 25 pressing and biasing the valve element in a closing 39 which maintains a pressure for pressing the direction; and a fuel chamber defined between the valve element 36 in the valve-opening direction is inner surface of the housing and the valve element defined between the valve element 36 and the end so as to maintain a pressure for pressing the valve surface of the small-diameter section 33. element in a valve-opening direction, wherein the The safety valve 3 of the above-described 30 high-pressure fuel from the inside passage is intro- structure is operated in the following manner. duced into the fuel chamber when the valve body When the fuel pressure in the accumulator 1 is of the valve element is separated from the seat not higher than a valve-opening pressure of the ball face. With this safety valve, the high-pressure fuel valve 37 which is predetermined by the spring 38, of the accumulator is introduced into the fuel cham- the ball valve 37 is contacted with the seat face 32. 35 ber in order to press the valve element in the With the ball valve 37 in this state, when the valve-opening direction so that the valve element fuel pressure in the accumulator 1 is increased, the will be rapidly opened, with the result that the fuel fuel introduced from the inside passage 31 causes pressure in the accumulator can recover a pre- the ball valve 37 to be opened against a biasing determined value instantaneously. force of the spring 38. Consequently, the fuel intro- 40 duced from the inside passage 31 flows into the Claims fuel chamber 39 and presses the valve element 36 in the valve-opening direction. As a result, the valve 1. A safety valve provided in a fuel injection ap- element 36 is rapidly opened to allow the fuel paratus including an accumulator in which fuel introduced from the inside passage 31 to flow to 45 is accumulated, the low pressure side of the safety valve at once so said safety valve for the fuel injection ap- that the accumulator 1 will recover a predetermined paratus comprises: pressure in an instant. a housing having an inside passage for Fig. 4 illustrates a change of the fuel pressure introducing the high-pressure fuel of the accu- in the accumulator 1 from the opening to the clos- 50 mulator into the inside of the housing and a ing of the safety valve. When the ball valve 37 is seat face formed at a portion of said inside opened at a valve-opening pressure Po, the fuel passage; pressure is decreased to a pressure PR instanta- a valve element provided movably within neously, and eventually reaches a valve-closing said housing and including a valve body to pressure Pc of the ball valve 37. 55 open/close said seat face; The pressure PR can be set to a predetermined an elastic member for pressing and bias- value by regulating a clearance a between the ing said valve element in a closing direction; valve element 36 and the small-diameter section and

3 EP 0 466 081 A1

a fuel chamber defined between the inner surface of said housing and said valve element so as to maintain a pressure for pressing said valve element in a valve-opening direction, the high-pressure fuel from said inside 5 passage being introduced into said fuel chamber when the valve body of said valve element is separated from said seat face.

A safety valve for a fuel injection apparatus 10 according to Claim 1, wherein said housing includes a small-diameter section in communication with said inside passage and a spring chamber whose diameter is larger than that of said small-diameter section, said valve element is being closely fitted in said small-diameter section.

A safety valve for a fuel injection apparatus according to Claim 1 or 2, wherein the valve 20 body of said valve element is a ball valve which is fixed to be pressed against said seat face, said fuel chamber being defined between an end portion of said valve element on which said ball valve is fixed and an end surface of 25 said small-diameter section.

A safety valve for a fuel injection apparatus according to Claim 2, wherein the increased fuel pressure in said accumulator can be set to 30 a predetermined value by regulating a clearance between the inner peripheral surface of said small-diameter section and the outer peripheral surface of said valve element. 35

55 EP 0 466 081 A1

FIG. 2

INJECTOR

F I G. 3

34 ,, I oo EP 0 466 081 A1

F I G. 4

Pc Pr Po Pe

ACCUMULATOR PRESSURE

F I G. 5

Po(Pc)Pe

ACCUMULATOR PRESSURE

6 European Office J Patent EUROPEAN SEARCH Application Number REPORT EP 91 11 1358

DOCUMENTS CONSIDERED TO BE RELEVANT Citation of document with indication, where appropriate, Relevant CLASSIFICATION OF THE Category of relevant passages to claim APPLICATION (Int. CI.5)

EP-A-0 299 337 (IVECO FIAT) 1-3 F 02 M 59/46 * column 2, line 49 - column 3, line 9; figure 1 * F 02 M 63/00

Y,A GB-A-925 590 (MASTABAR MINING EQUIPMENT COM- 1-3,4 PANY) * page 2, line 39 - line 108; figure 2 *

EP-A-0 145 436 (LUCAS INDUSTRIES) 1,2,4 * page 4, line 19 - page 6, line 9; figure 1 *

FR-A-2 341 087 (BENDIBERICA) 1,3 * page 2, line 14 - page 4, line 30; figures 1,2 *

FR-A-2 609 503 (IVECO FIAT) * page 3, line 16 - page 4, line 21; figure 2 *

US-A-4 217 862 (FORT) * column 3, line 38 - line 48; figure 1 *

US-A-3 373 764 (MUNN) TECHNICAL FIELDS SEARCHED (Int. CI.5) F 02 M F 16 K

The present search report has been drawn up for all claims Place of search Date of completion of search The Hague 02 October 91 FRIDEN CM. CATEGORY OF CITED DOCUMENTS E : earlier patent document, but published on, or after particularly relevant if taken alone the filing date particularly relevant if combined with another D: document cited in the application document of the same catagory L : document cited for other reasons technological background non-written disclosure & : member of the same patent family, corresponding intermediate document document theory or principle underlying the invention