CA1203730A - Fuel injection nozzle - Google Patents
Fuel injection nozzleInfo
- Publication number
- CA1203730A CA1203730A CA000433816A CA433816A CA1203730A CA 1203730 A CA1203730 A CA 1203730A CA 000433816 A CA000433816 A CA 000433816A CA 433816 A CA433816 A CA 433816A CA 1203730 A CA1203730 A CA 1203730A
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- CA
- Canada
- Prior art keywords
- nozzle
- fuel passage
- nozzle needle
- fuel injection
- cylindrical surface
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
ABSTRACT OF THE DISCLOSURE
A fuel injection nozzle is provided with such an annular fuel passage that its fuel passage section is, at the earlier stage of fuel injection, maintained smaller than the whole sum of the sectional areas of injection orifices and adapted to increase gradually in response to the lift of a nozzle needle so that the rate of fuel injection increases gradually.
A fuel injection nozzle is provided with such an annular fuel passage that its fuel passage section is, at the earlier stage of fuel injection, maintained smaller than the whole sum of the sectional areas of injection orifices and adapted to increase gradually in response to the lift of a nozzle needle so that the rate of fuel injection increases gradually.
Description
3~31~
FUEL INJECTION NOZZLE
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates in general to fuel injection nozzles and particularly to improvements in a so-called hole type fuel injection nozzle for use in direct fuel-injection diesel engines.
FUEL INJECTION NOZZLE
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates in general to fuel injection nozzles and particularly to improvements in a so-called hole type fuel injection nozzle for use in direct fuel-injection diesel engines.
2. Description of the Prior Art It has been proposed to construct a hole-t-ype fuel injection nozzle in such a manner as disclosed in the provisional Japanese Utillty Model Publication No. 54-112918. This prior art fuel injection nozzle however encounters the problem that it leads to a large nitrogen oxides (NOx) content in the exhaust gases and to a large combustion noise.
SUMM~RY OF THE INVENTION
It is an object of the present invention to provide a fuel injection nozzle which completely solves the above noted problem.
A feature of the present invention is the provision of a fuel injection nozzle which comprises a hollow nozzle body formed at the tip portion thereof with a conical valve seat and at least one fuel injection orifice havlng an upstream end located in the valve ~2~3731~
seat; a nozzle needle axially movable in the nozzle body and formed at an end with a conical seating surface engageable with the valve seat to control fuel flow through the injection orifice; and means for defining between the nozzle body and the nozzle needle at a location upstream of a fuel passage which is to be formed between the valve sea-t and the seating surface upon lifting of the nozzle needle, an annular fuel passage having a fuel passage section of which sectional area is, at the earlier stage of fuel injection, maintained smaller thar the sectional area of the injection orifice and which is adapted to increase gradually in response to the lift of the nozzle needle.
By the provision of such an annular fuel passage, the rate of fuel injection at the earlier stage thereof can be restricted to be smaller and can be controlled in a manner as to increase gradually, which is ~uite effective in solving the problem noted above for the reason as will be described hereinlater.
BRIEY DESCRIPTION OY THE DRAWINGS
The features and advantages of the fuel injection nozzle according to the present invention will beco~e more clearly appreciated from the following description taken in conjunction with the accompanying drawings, in which:-Fig~ l is a lony;tudinal sec-tional view of a tip portion of a prior art hole type fuel injection nozzle;
Fig~ 2 is a view similar to Fig. l but shows a ho'le type fuel injection nozzle in accordance with a first embodiment of the present invention;
Fig. 3 is a sectional view taken along the line III-III of Fig. 2;
Fig. 4 is a view similar to Fig. 2 but shows the nozzle needle lifted to permit free fuel flow;
Fig. 5 is a graph illustrating the rate of fuel injection as a function of the nozzle needle lift9 for the fuel injection nozzle of Fig. 2, the dotted line indica-ting the corresponding rate of fuel inj,ection of the com parable prior art device, Fig. 6 which is on the same sheet as Fig. 4 is a view simi'lar to Fig. 2 but shows a second embodiment of the present invention;
Fig. 7 is a graph similar to Fig. 5 but shows a performance characteristics of the second embodiment, the dotted line indicating the performance characteristics of the comparable prior art device;
Fig. 8 is a view similar to Fig. 6 but shows the nozzle need'le liEted nearly maximunlly; and
SUMM~RY OF THE INVENTION
It is an object of the present invention to provide a fuel injection nozzle which completely solves the above noted problem.
A feature of the present invention is the provision of a fuel injection nozzle which comprises a hollow nozzle body formed at the tip portion thereof with a conical valve seat and at least one fuel injection orifice havlng an upstream end located in the valve ~2~3731~
seat; a nozzle needle axially movable in the nozzle body and formed at an end with a conical seating surface engageable with the valve seat to control fuel flow through the injection orifice; and means for defining between the nozzle body and the nozzle needle at a location upstream of a fuel passage which is to be formed between the valve sea-t and the seating surface upon lifting of the nozzle needle, an annular fuel passage having a fuel passage section of which sectional area is, at the earlier stage of fuel injection, maintained smaller thar the sectional area of the injection orifice and which is adapted to increase gradually in response to the lift of the nozzle needle.
By the provision of such an annular fuel passage, the rate of fuel injection at the earlier stage thereof can be restricted to be smaller and can be controlled in a manner as to increase gradually, which is ~uite effective in solving the problem noted above for the reason as will be described hereinlater.
BRIEY DESCRIPTION OY THE DRAWINGS
The features and advantages of the fuel injection nozzle according to the present invention will beco~e more clearly appreciated from the following description taken in conjunction with the accompanying drawings, in which:-Fig~ l is a lony;tudinal sec-tional view of a tip portion of a prior art hole type fuel injection nozzle;
Fig~ 2 is a view similar to Fig. l but shows a ho'le type fuel injection nozzle in accordance with a first embodiment of the present invention;
Fig. 3 is a sectional view taken along the line III-III of Fig. 2;
Fig. 4 is a view similar to Fig. 2 but shows the nozzle needle lifted to permit free fuel flow;
Fig. 5 is a graph illustrating the rate of fuel injection as a function of the nozzle needle lift9 for the fuel injection nozzle of Fig. 2, the dotted line indica-ting the corresponding rate of fuel inj,ection of the com parable prior art device, Fig. 6 which is on the same sheet as Fig. 4 is a view simi'lar to Fig. 2 but shows a second embodiment of the present invention;
Fig. 7 is a graph similar to Fig. 5 but shows a performance characteristics of the second embodiment, the dotted line indicating the performance characteristics of the comparable prior art device;
Fig. 8 is a view similar to Fig. 6 but shows the nozzle need'le liEted nearly maximunlly; and
3~a3~
Fig. 9 is a diagrammatic view showing by an enlarged scale the details of the sectional area of the minimum fuel passage section defined between the nozzle needle and the nozzle body of Fig. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before describing the preferred embodiments of this invention, reference is first made to Fig. 1 wherein a prior art hole type fuel injection nozzle as disclosed in the foregoing Japanese Utility Model Publication is shown, for the purpose of analizing the foregoing problem of the prior art device.
In Fig. 1, the prior art hole type fuel injection nozzle is shown as comprising a nozzle body 10 and a nozzle needle 12. The nozzle body 10 has a hollow conical tip portion where it is formed with a conical valve seat 14. The tip portion of the nozzle body 10 is also formed with a plura:Lity of injection orifices 16 of which upstream ends are located in the valve seat 1 Ll . The nozzle needle 12 is axially slidably received in the nozzle body 10 and its tip portion is formed with a conical valve portion 18 which closes the injection orifices 16 when seating on the valve seat 14. The tip portion of the nozzle needle 12 is also formed with a frustoconical portion 20 which defines part of a pressure chamber 22.
~l2~3~3q~
~5--In operation, the nozzle needle 12 ls lifted upwardly in the drawing by a predetermined pressure acting on the conical surface 20. The li.ft of the nozzle needle 12 results in a formation of an annular fuel passage between the valve seat 14 and the valve portion 18, through which annular fuel passage fuel flows into the injection orifices 16 and therefrom is discharged into the combustion chamber.
In the above described fuel injection nozzle, upon lifting of the noz:zle needle 12 the sectional area of the fuel passage formed between the valve seat 14 and the valve portion 18 increases rapidly up to the area equal to the whole sum of the sectional areas of the injection orifices 16, thus allowing ~5 the rate of fuel injection to increase rapidly to the maximum possible rate that is determined by the whole sum of the sectional areas of the injection orifices 16. With this prior art fuel injection nozzle, a great amount of fuel is therefore injected into the combustion chamber at the earlier stage of fuel injection. This leads to a rapid rise of the pressure and ternperature in the combustion chamber and there~ore to a large combustion noise and a large nltrogen oxides (~Ox) content in the exhaust gases. By the study conducted by the applicants, ~Z~3~
it is revealed that the foregolng problem of the prior art device is resulted from the rapid rise of fuel injection rate at the earlier stage thereof~
In view of this fact~ it is proposed by the present invention a novel and improved fuel injection nozzle which is free from the foregoing problem and which will be described hereinafter.
Referring now to Figs. 2 to 5, the fuel injection nozzle in accordance with a first embodiment of the present invention is shown as comprising a hollow nozzle body 24 and a nozzle needle 26 axially slidably received therein, though only the tip portion of the fuel injection nozzle is shown in the drawings.
The nozzle body 24 has a conical tip portion ~here it is formed with a straigh~ bore 28 which cooperates with a generally cylindrical surface 30 oF the nozzle needle 26 to define therebetween an annular fuel passage 32. The downstream end of the bore 28 terminates in a conical valve seat 34 which may be engaged by a correspordingly cone-shaped seating surface 36 on the end of the nozzle needle 26 in which the downstream end of the cylindrical surface 30 terminates.
The upstream end of the cylindrical surface 30 terminates in a pressure taper 38 which is surround by a pressure chamber L10 communicating with any suitable source of fluid under pressure, such as a fuel injection pump, not shown. The upstream end of the bore 30 terminates in a frustoconical flared portion 42 which may receive therein the downstream end portion of the pressure taper 38 in a manner to define there-between a fuel passage 44 providing communication between the pressure chamber 40 and the annular fuel passage 32. The tip portion of the nozzle body 24 is also formed with a plurality of injecton orifices 46 of which upstream ends are located in the valve seat 34 so that fuel flow through the injection orifices 46 are controlled by the seating surface 36 of the nozzle needle 26.
The conical seating surface 36 of the nozzle needle 26 has a blunted extremety so that a small fluid chamber 48 is defined between the extremeties of the seating surface 36 and the valve seat 34 when the seating surface seats on the valve seat.
The nozzle needle 26 is also formed at the ~ downstream side portion of the cylindrical surface 30 with a plurality o~ grooves 50 extending axially of the nozzle needle to have a downstream end opening through the seating surface 36. The sectional area of the annular fuel passage section 32 defined between the upstream side portion of the cylindrical surface 30 and the bore 28 is smaller than the whole sum of the sectional areas of the injection orifices 46 so that the upstream side portion of the cylindrical surface 30 serves as a fuel flow restricting portion 52 of which downstream end is determined by the upstream end of the groove 50. The whole sum of the sectional areas of the above-mentioned annular fuel passage section 32 and the grooves 50 is designed to be larger than the whole sum of the sectional areas of the injection orifices 46. The axial length h of the fuel flow restricting portion 52 is designed to be smaller than the maximum lift of the nozzle needle 26 by such an amount that is determined depending upon how long at the earlier stage it is desired lS to resirict the rate of fuel injection. That is, the longer the fuel flow restricting portion is made, the longer at the earlier stage the rate of fuel injection is restricted.
In operation~ when the fuel pressure in the pressure chamber 40 increases up to a predetermined value, the pressure acting on the pressure taper 38 causes the nozzle needle 26 to be lifted, allowing the injection orifices 46 to open to initiate fuel injection. In this instance, at the first step of nozzle needle lift, that is, during the time ~3~3~
_9_ when lift of the nozzle needle 26 is smaller than the length h of the fuel flow restricting portion 52J the rate of fuel injection is restricted by the fuel flow restricting portion 52 and is maintained small. When the lift of the no%zle needle 26 exceeds the length h of the fuel flow restricting portion 52 as shown in Fig. 4, fuel flows freely from the pressure chamber 40 to the injection orifices 46 through the grooves 50 in addition to the annular fuel passage 32. From this time onward, the rate of fuel injection is determined by the whole sum of the sectional areas of the injection orifices 46.
Accordingly, the rate of fuel injection as a function of the lift of nozzle needle for the fuel injection nozzle in accordance with the first embodiment of this invention is controlled in such a manner as represented by the solid line in Fig. 5.
That is, the fuel injection rate at the earlier stage of fuel injection (which corresponds to the nozzle needle lifting range X1 and wherein the lift of nozzle needle is smaller than the length h of the fuel flow restricting portion 52) is restricted by the fuel flow restricting portion and set smaller as indicated by R1, while at the later s-tage (which ~2~37~
corresponds to the nozzle needle lifting range X2 and wherein the lift of the nozzle needle exceeds the length h of the fuel flow restricting portion) the fuel injection rate is determined by the whole sum of the sectional areas of the injection orifices 46 and set larger as represented by R2. The rate of fuel injection effected by the fuel injection nozzle of the first embodiment of this invention thus increases stepwisely and gradually.
Referring to Figs. 6 and 7, a modification in accordance with the present invention will be described hereinafter~ In the modified embodiment, elements or parts substantially similar to or functionally identical with those of the previous embodiment are indicated by like reference numerals as their corresponding parts of the previous embodiment, with prime marks added and will not be described again for br~vity.
In this modified embodiment, the nozzle body 24' is provided with a tapered bore 54 in place of the straight bore 28 in the previous embodiment, and the cylindrical surface 30~ of the nozzle needle 26' is not provided with such grooves 50 as in ,'he previous ernbodiment. With this modification, such an annular fue]. passage 32' that has a pair of symmetrical 3~:~
triangular sections about the central axis thereof is defined between the tapered bore 54 and the cylindrical surface 30' when the seating surface 36l of the nozzle needle 26' is held seated on the valve seat 34'. In other words, the sectional area of the annular fuel passage 32' is largest at the upstream end and reduces gradually toward the downstream end where it is smallest. For this reason9 the downstream end or smaller diameter end of the tapered bore 54 is designed to be nearly equal in the diameter to the cylindrical surface 30 t of the nozzle needle 26'. More specifically, the fuel passage 32' is designed so that the sectional area of the fuel passage section defined between the downstream end of the cylindrical surface 30l and the tapered bore 54 when the nozzle needle 26' is lifted nearly maximumly, is equal to or larger than the whole sum of the sectional areas of the injection orifices 46. The taper of the tapered bore 54 is determined depending upon how much at the earlier stage of fuel injection it is desired to res-trict the rate of fuel injection.
Description being further made as to the fuel passage 32', the sectional area of the minimum fuel passage section defined between the downstream end of the cylindrical surface 30' and the tapered bore ~37~
5ll when the nozzle needle 26' is lifted nearly maximumly is equal to the area M of the tapered peripheral surface of a truncated cone that i.s obtained, as diagrammatically shown in Fig. 9, by rotating a trapezoid OPQS about the axis OP (the central axis of the cylindrical surface 30~O The tapered peripheral surface area M is obtained from the following equation:
M = ~(R -~ r) ~ (R _ r)2 ~ h2 (1) where R is the radius of the larger diameter end of the truncated cone, r is the radius of the smaller diameter end of the truncated cone and h is the height of the truncated cone.
In this instance, assuming that the lift of the nozzle needle 26' is Q 9 the diameter of the cylindrical surface 30' of the nozzle needle 26' is d, and the angle which the tapered bore 54 and the cylindrical surface 30' form with each other with respect to a sectional plane passing through the certral axis OP is ~, the following equations are obtained:
r = 2' h = Qsin2 ~, R = 2d -~ Qsin ~ cons 73~
substitution of the equation (1) for r = 2d, h = Qsin2 ~, and R = 2d ~ Qsin ~ ~ cons ~ provides M = ~Q(d ~ Qsin ~ cos ~) sin ~ (2) By the experiments conducted by the applicants, it is found that the following formula must be satisfied in order to attain the desired restriction of the rate of fuel injection at the earlier stage thereof:
SO _ Mo ~ 2So (3) where SO is the whole sum of the sectional areas of the injection orifices, that is, SO = n- ~d2 where n. is the number of the injection orifices, and Mo is the sectional area of` the minimum fuel passage section when the nozzle needle is lifted by a predetermined full lift or maximum lift QO.
From (2) and (3), the following equation is obtained:
l~d < (d ~ Q sin ~ cos ~) sin~ < n2d ~33~3~
Thus, the angle ~ is designed so as to satisfy the equation ( Ll ), In operation of the modified embodiment, since a~ the earlier stage of nozzle needle lift the sectional S area of the minimum fuel passage section defined between the downstream end of the cylindrical surface 30' and the tapered bore 54 is maintained smaller than the whole sum of the sectional areas of the injection orifices 46' and adapted to increase gradually as the lift of the nozzle needle increases, the rate of fuel injection increases gradually as represented by the solid line in Fig. 7. The dotted line in Fig. 7 indicates the performance characteristlcs of the comparable prior art device.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention ~ay be practiced otherwise than as specifically described.
Fig. 9 is a diagrammatic view showing by an enlarged scale the details of the sectional area of the minimum fuel passage section defined between the nozzle needle and the nozzle body of Fig. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before describing the preferred embodiments of this invention, reference is first made to Fig. 1 wherein a prior art hole type fuel injection nozzle as disclosed in the foregoing Japanese Utility Model Publication is shown, for the purpose of analizing the foregoing problem of the prior art device.
In Fig. 1, the prior art hole type fuel injection nozzle is shown as comprising a nozzle body 10 and a nozzle needle 12. The nozzle body 10 has a hollow conical tip portion where it is formed with a conical valve seat 14. The tip portion of the nozzle body 10 is also formed with a plura:Lity of injection orifices 16 of which upstream ends are located in the valve seat 1 Ll . The nozzle needle 12 is axially slidably received in the nozzle body 10 and its tip portion is formed with a conical valve portion 18 which closes the injection orifices 16 when seating on the valve seat 14. The tip portion of the nozzle needle 12 is also formed with a frustoconical portion 20 which defines part of a pressure chamber 22.
~l2~3~3q~
~5--In operation, the nozzle needle 12 ls lifted upwardly in the drawing by a predetermined pressure acting on the conical surface 20. The li.ft of the nozzle needle 12 results in a formation of an annular fuel passage between the valve seat 14 and the valve portion 18, through which annular fuel passage fuel flows into the injection orifices 16 and therefrom is discharged into the combustion chamber.
In the above described fuel injection nozzle, upon lifting of the noz:zle needle 12 the sectional area of the fuel passage formed between the valve seat 14 and the valve portion 18 increases rapidly up to the area equal to the whole sum of the sectional areas of the injection orifices 16, thus allowing ~5 the rate of fuel injection to increase rapidly to the maximum possible rate that is determined by the whole sum of the sectional areas of the injection orifices 16. With this prior art fuel injection nozzle, a great amount of fuel is therefore injected into the combustion chamber at the earlier stage of fuel injection. This leads to a rapid rise of the pressure and ternperature in the combustion chamber and there~ore to a large combustion noise and a large nltrogen oxides (~Ox) content in the exhaust gases. By the study conducted by the applicants, ~Z~3~
it is revealed that the foregolng problem of the prior art device is resulted from the rapid rise of fuel injection rate at the earlier stage thereof~
In view of this fact~ it is proposed by the present invention a novel and improved fuel injection nozzle which is free from the foregoing problem and which will be described hereinafter.
Referring now to Figs. 2 to 5, the fuel injection nozzle in accordance with a first embodiment of the present invention is shown as comprising a hollow nozzle body 24 and a nozzle needle 26 axially slidably received therein, though only the tip portion of the fuel injection nozzle is shown in the drawings.
The nozzle body 24 has a conical tip portion ~here it is formed with a straigh~ bore 28 which cooperates with a generally cylindrical surface 30 oF the nozzle needle 26 to define therebetween an annular fuel passage 32. The downstream end of the bore 28 terminates in a conical valve seat 34 which may be engaged by a correspordingly cone-shaped seating surface 36 on the end of the nozzle needle 26 in which the downstream end of the cylindrical surface 30 terminates.
The upstream end of the cylindrical surface 30 terminates in a pressure taper 38 which is surround by a pressure chamber L10 communicating with any suitable source of fluid under pressure, such as a fuel injection pump, not shown. The upstream end of the bore 30 terminates in a frustoconical flared portion 42 which may receive therein the downstream end portion of the pressure taper 38 in a manner to define there-between a fuel passage 44 providing communication between the pressure chamber 40 and the annular fuel passage 32. The tip portion of the nozzle body 24 is also formed with a plurality of injecton orifices 46 of which upstream ends are located in the valve seat 34 so that fuel flow through the injection orifices 46 are controlled by the seating surface 36 of the nozzle needle 26.
The conical seating surface 36 of the nozzle needle 26 has a blunted extremety so that a small fluid chamber 48 is defined between the extremeties of the seating surface 36 and the valve seat 34 when the seating surface seats on the valve seat.
The nozzle needle 26 is also formed at the ~ downstream side portion of the cylindrical surface 30 with a plurality o~ grooves 50 extending axially of the nozzle needle to have a downstream end opening through the seating surface 36. The sectional area of the annular fuel passage section 32 defined between the upstream side portion of the cylindrical surface 30 and the bore 28 is smaller than the whole sum of the sectional areas of the injection orifices 46 so that the upstream side portion of the cylindrical surface 30 serves as a fuel flow restricting portion 52 of which downstream end is determined by the upstream end of the groove 50. The whole sum of the sectional areas of the above-mentioned annular fuel passage section 32 and the grooves 50 is designed to be larger than the whole sum of the sectional areas of the injection orifices 46. The axial length h of the fuel flow restricting portion 52 is designed to be smaller than the maximum lift of the nozzle needle 26 by such an amount that is determined depending upon how long at the earlier stage it is desired lS to resirict the rate of fuel injection. That is, the longer the fuel flow restricting portion is made, the longer at the earlier stage the rate of fuel injection is restricted.
In operation~ when the fuel pressure in the pressure chamber 40 increases up to a predetermined value, the pressure acting on the pressure taper 38 causes the nozzle needle 26 to be lifted, allowing the injection orifices 46 to open to initiate fuel injection. In this instance, at the first step of nozzle needle lift, that is, during the time ~3~3~
_9_ when lift of the nozzle needle 26 is smaller than the length h of the fuel flow restricting portion 52J the rate of fuel injection is restricted by the fuel flow restricting portion 52 and is maintained small. When the lift of the no%zle needle 26 exceeds the length h of the fuel flow restricting portion 52 as shown in Fig. 4, fuel flows freely from the pressure chamber 40 to the injection orifices 46 through the grooves 50 in addition to the annular fuel passage 32. From this time onward, the rate of fuel injection is determined by the whole sum of the sectional areas of the injection orifices 46.
Accordingly, the rate of fuel injection as a function of the lift of nozzle needle for the fuel injection nozzle in accordance with the first embodiment of this invention is controlled in such a manner as represented by the solid line in Fig. 5.
That is, the fuel injection rate at the earlier stage of fuel injection (which corresponds to the nozzle needle lifting range X1 and wherein the lift of nozzle needle is smaller than the length h of the fuel flow restricting portion 52) is restricted by the fuel flow restricting portion and set smaller as indicated by R1, while at the later s-tage (which ~2~37~
corresponds to the nozzle needle lifting range X2 and wherein the lift of the nozzle needle exceeds the length h of the fuel flow restricting portion) the fuel injection rate is determined by the whole sum of the sectional areas of the injection orifices 46 and set larger as represented by R2. The rate of fuel injection effected by the fuel injection nozzle of the first embodiment of this invention thus increases stepwisely and gradually.
Referring to Figs. 6 and 7, a modification in accordance with the present invention will be described hereinafter~ In the modified embodiment, elements or parts substantially similar to or functionally identical with those of the previous embodiment are indicated by like reference numerals as their corresponding parts of the previous embodiment, with prime marks added and will not be described again for br~vity.
In this modified embodiment, the nozzle body 24' is provided with a tapered bore 54 in place of the straight bore 28 in the previous embodiment, and the cylindrical surface 30~ of the nozzle needle 26' is not provided with such grooves 50 as in ,'he previous ernbodiment. With this modification, such an annular fue]. passage 32' that has a pair of symmetrical 3~:~
triangular sections about the central axis thereof is defined between the tapered bore 54 and the cylindrical surface 30' when the seating surface 36l of the nozzle needle 26' is held seated on the valve seat 34'. In other words, the sectional area of the annular fuel passage 32' is largest at the upstream end and reduces gradually toward the downstream end where it is smallest. For this reason9 the downstream end or smaller diameter end of the tapered bore 54 is designed to be nearly equal in the diameter to the cylindrical surface 30 t of the nozzle needle 26'. More specifically, the fuel passage 32' is designed so that the sectional area of the fuel passage section defined between the downstream end of the cylindrical surface 30l and the tapered bore 54 when the nozzle needle 26' is lifted nearly maximumly, is equal to or larger than the whole sum of the sectional areas of the injection orifices 46. The taper of the tapered bore 54 is determined depending upon how much at the earlier stage of fuel injection it is desired to res-trict the rate of fuel injection.
Description being further made as to the fuel passage 32', the sectional area of the minimum fuel passage section defined between the downstream end of the cylindrical surface 30' and the tapered bore ~37~
5ll when the nozzle needle 26' is lifted nearly maximumly is equal to the area M of the tapered peripheral surface of a truncated cone that i.s obtained, as diagrammatically shown in Fig. 9, by rotating a trapezoid OPQS about the axis OP (the central axis of the cylindrical surface 30~O The tapered peripheral surface area M is obtained from the following equation:
M = ~(R -~ r) ~ (R _ r)2 ~ h2 (1) where R is the radius of the larger diameter end of the truncated cone, r is the radius of the smaller diameter end of the truncated cone and h is the height of the truncated cone.
In this instance, assuming that the lift of the nozzle needle 26' is Q 9 the diameter of the cylindrical surface 30' of the nozzle needle 26' is d, and the angle which the tapered bore 54 and the cylindrical surface 30' form with each other with respect to a sectional plane passing through the certral axis OP is ~, the following equations are obtained:
r = 2' h = Qsin2 ~, R = 2d -~ Qsin ~ cons 73~
substitution of the equation (1) for r = 2d, h = Qsin2 ~, and R = 2d ~ Qsin ~ ~ cons ~ provides M = ~Q(d ~ Qsin ~ cos ~) sin ~ (2) By the experiments conducted by the applicants, it is found that the following formula must be satisfied in order to attain the desired restriction of the rate of fuel injection at the earlier stage thereof:
SO _ Mo ~ 2So (3) where SO is the whole sum of the sectional areas of the injection orifices, that is, SO = n- ~d2 where n. is the number of the injection orifices, and Mo is the sectional area of` the minimum fuel passage section when the nozzle needle is lifted by a predetermined full lift or maximum lift QO.
From (2) and (3), the following equation is obtained:
l~d < (d ~ Q sin ~ cos ~) sin~ < n2d ~33~3~
Thus, the angle ~ is designed so as to satisfy the equation ( Ll ), In operation of the modified embodiment, since a~ the earlier stage of nozzle needle lift the sectional S area of the minimum fuel passage section defined between the downstream end of the cylindrical surface 30' and the tapered bore 54 is maintained smaller than the whole sum of the sectional areas of the injection orifices 46' and adapted to increase gradually as the lift of the nozzle needle increases, the rate of fuel injection increases gradually as represented by the solid line in Fig. 7. The dotted line in Fig. 7 indicates the performance characteristlcs of the comparable prior art device.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention ~ay be practiced otherwise than as specifically described.
Claims (10)
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:
1. A fuel injection nozzle comprising:
a hollow nozzle body formed at the tip portion thereof with a conical valve seat and at least one fuel injection orifice having an upstream end located in said valve seat;
a nozzle needle axially movable in said nozzle body and formed at an end with a conical seating surface engageable with said valve seat to control fuel flow through said injection orifice; and means for defining between said nozzle body and said nozzle needle at a location upstream of a fuel passage which is to be formed between said valve seat and said seating surface upon lifting of said nozzle needle, an annular fuel passage having a fuel passage section of which sectional area is, at the earlier stage of fuel injection, maintained smaller than the sectional area of said injection orifice and which is adapted to increase gradually in response to the lift of the nozzle needle.
a hollow nozzle body formed at the tip portion thereof with a conical valve seat and at least one fuel injection orifice having an upstream end located in said valve seat;
a nozzle needle axially movable in said nozzle body and formed at an end with a conical seating surface engageable with said valve seat to control fuel flow through said injection orifice; and means for defining between said nozzle body and said nozzle needle at a location upstream of a fuel passage which is to be formed between said valve seat and said seating surface upon lifting of said nozzle needle, an annular fuel passage having a fuel passage section of which sectional area is, at the earlier stage of fuel injection, maintained smaller than the sectional area of said injection orifice and which is adapted to increase gradually in response to the lift of the nozzle needle.
2. A fuel injection nozzle as set forth in Claim 1, in which said nozzle body is formed with a straight bore of which downstream end terminates in said valve seat, said nozzle needle being formed with a generally cylindrical surface which cooperates with said straight bore to define therebetween part of said annular fuel passage, said cylindrical surface having a downstream end terminating in said conical seating surface, and in which said nozzle needle is also formed at the downstream side portion of said cylindrical surface with at least one groove extending axially of the nozzle needle to have a downstream end opening through said seating surface, said groove forming part of said annular fuel passage and cooperates with said cylindrical surface and said straight bore to constitute said annular fuel passage means.
3. A fuel injection nozzle as set forth in Claim 2, in which said groove is of the length shorter than a predetermined maximum lift of said nozzle needle.
4. A fuel injection nozzle as set forth in Claim 3, in which said cylindrical surface of said nozzle needle has an upstream side portion of which down stream end is defined by the upstream end of said groove, and in which the sectional area of the annular fuel passage section defined between said upstream side portion of` said cylindrical surface and said straight bore is smaller than the sectional area of said injection orifice, the whole sum of the sectional areas of said annular fuel passage section defined between the upstream side portion of the cylindrical surface and the straight bore and said groove being larger than the sectional area of said injection orifice.
5. A fuel injection nozzle as set forth in Claim 4, in which said nozzle needle further has a pressure taper in which the upstream end of said cylindrical surface terminates and which is surrounded by a pressure chamber, and in which said nozzle body further has a frustoconical flared portion in which the upstream end of said cylindrical surface terminates and which may receive therein the downstream end portion of said pressure taper in a manner to define therebetween a fuel passage providing communication between said pressure chamber and said annular fuel passage.
6. A fuel injection nozzle as set forth in Claim 1, in which said nozzle body is formed with a tapered bore of which downstream end terminates in said valve seat, and in which said nozzle needle is formed with a generally cylindrical surface which cooperates with said tapered bore to define therebetween said annular fuel passage of which sectional area is largest at the upstream end and reduces gradually toward the downstream end where it is smallest, said tapered bore and said cylindrical surface con-stituting said annular fuel passage defining means.
7. A fuel injection nozzle as set forth in Claim 6, in which the downstream end of said tapered bore is nearly equal in diameter to said cylindrical surface.
8. A fuel injection orifices as set forth in Claim 7, in which said annular fuel passage is adapted to have such a fuel passage section when said nozzle needle is lifted nearly maximumly that is equal to or larger than the sectional area of said injection orifice.
9. A fuel injection orifice as set forth in Claim 8, in which said nozzle needle further has a pressure taper in which the upstream end of said cylindrical surface terminates and which is surrounded by a pressure chamber, and in which said nozzle body further has a frustoconical flared portion in which the upstream end of said straight bore terminates and which may receive therein the downstream end portion of said pressure taper in a manner to define therebetween a fuel passage for providing communication between said pressure chamber and said annular fuel passage.
10. A fuel injection nozzle comprising:
a hollow nozzle body formed at the tip portion thereof with a conical valve seat and a plurality of injection orifices having an upstream end located in said valve seat;
a nozzle needle axially movable in said nozzle body and formed at an end with a conical seating surface engageable with said valve seat to control fuel flow through said orifices; and means for defining between said nozzle body and said nozzle needle at a location upstream of a fuel passage which is to be formed between said valve seat and said seating surface upon lifting of said nozzle needle, an annular fuel passage having a fuel passage section of which sectional area is, at the earlier stage of fuel injection, maintained smaller than the whole sum of the sectional areas of said injection orifices and which is adapted to increase gradually in response to the lift of the nozzle needle.
a hollow nozzle body formed at the tip portion thereof with a conical valve seat and a plurality of injection orifices having an upstream end located in said valve seat;
a nozzle needle axially movable in said nozzle body and formed at an end with a conical seating surface engageable with said valve seat to control fuel flow through said orifices; and means for defining between said nozzle body and said nozzle needle at a location upstream of a fuel passage which is to be formed between said valve seat and said seating surface upon lifting of said nozzle needle, an annular fuel passage having a fuel passage section of which sectional area is, at the earlier stage of fuel injection, maintained smaller than the whole sum of the sectional areas of said injection orifices and which is adapted to increase gradually in response to the lift of the nozzle needle.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11859282U JPS5922984U (en) | 1982-08-04 | 1982-08-04 | fuel injection nozzle |
| JP57-118592 | 1982-08-04 | ||
| JPUM58-107952 | 1983-07-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1203730A true CA1203730A (en) | 1986-04-29 |
Family
ID=33307382
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000433816A Expired CA1203730A (en) | 1982-08-04 | 1983-08-03 | Fuel injection nozzle |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5922984U (en) |
| CA (1) | CA1203730A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2565471Y2 (en) * | 1991-06-07 | 1998-03-18 | 株式会社ゼクセル | Fuel injection nozzle |
| JP6036354B2 (en) * | 2013-02-04 | 2016-11-30 | 日立オートモティブシステムズ株式会社 | Fuel injection valve |
-
1982
- 1982-08-04 JP JP11859282U patent/JPS5922984U/en active Granted
-
1983
- 1983-08-03 CA CA000433816A patent/CA1203730A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5922984U (en) | 1984-02-13 |
| JPS6115251Y2 (en) | 1986-05-12 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |