Fuel injection nozzle clamping structure

Abstract: A fuel injection nozzle clamping structure adapted to fix three series-arranged fuel injection nozzles 1 for an engine by a uniform level of force by one nozzle clamp 19 having both-end nozzle contacting portions 9 and intermediate nozzle contacting portions 20, and insert holes 8 for stud bolts 7 in the parts of the nozzle clamp 19 which are halfway between adjacent nozzle contacting portions 9, 20.

Description: Background of the Invention: This invention relates to a fuel injection nozzle clamping structure for internal combustion engines, and more particularly to a fuel injection nozzle clamping structure adapted to clamp three fuel injection nozzles, which constitute one set of fuel injection nozzles, by one nozzle clamp and fix the same to a cylinder head. Known means for fixing a fuel injection nozzle for an internal combustion engine to a cylinder head include, for example, a means in which a nozzle clamp is provided in the form of a beam between a fuel injection nozzle and a cylinder head, an intermediate portion of which clamp is tightened and fixed by bolts and nuts as disclosed in Japanese Patent Laid-Open No. 182680/1991. The fuel injection nozzle is fixed to a cylinder head by cutting both side surfaces of the fuel injection nozzle to form clamp receiving seats, inserting the resultant fuel injection nozzle into a nozzle setting bore made in the cylinder head, fitting a bifurcated support portion, which is formed at one end of a nozzle clamp, in the clamp receiving seats, inserting a stud bolt, which is fixed to the cylinder head, into a bolt hole formed in an intermediate portion of the nozzle clamp, and screwing a nut on this bolt with the other end of the nozzle clamp engaged with the clamp receiving seats formed on the cylinder head. It is necessary that such a fuel nozzle clamping structure formed so that a fuel nozzle is clamped by supporting a fuel injection nozzle on one end portion of a nozzle clamp, and fastening an intermediate portion of the nozzle clamp by tightening a stud bolt with the other end portion of the nozzle clamp supported on the clamp receiving seats on the cylinder head, has construction for sealing the fuel injection nozzle by applying a reliable pressing force thereto in accordance with a vertical position of the clamp receiving seats on the fuel injection nozzle. In the case of a four-valve engine in which four valves are provided on both sides of a fuel injection valve, cams for driving these valves and a cam shaft supporting these cams are provided close to each other, so that it is necessary to avoid the interference of the cam and fuel injection nozzle with each other. Moreover, there is layout restriction that the fuel injection nozzle should be provided within a head cover. Consequently, it becomes difficult to adopt a method of tightening one fuel injection nozzle by one nozzle clamp, and the dimensions of the head cover and a space for the installation of the nozzle clamp increase. This poses problems with the designing of an engine. In the conventional example of a fuel injection nozzle clamping structure shown in Fig. 7 of the accompanying drawings, width across flat clamp receiving seats 4 is formed by cutting both side surfaces of an intermediate portion of a fuel injection nozzle 1, and a clamp receiving seat 5 is further formed on an upper surface of a cylinder head 2. This fuel injection nozzle 1 is inserted into a nozzle setting bore 3 made in the cylinder head 2, and a bifurcated portion formed at one end of a nozzle clamp 6 is fitted in the width across flat clamp receiving seats 4 of the fuel injection nozzle 1. A clamping bolt 7 fixed to the cylinder head 2 is inserted into a bolt hole 8 provided in an intermediate portion of the nozzle clamp 6, and a nut 10 with a spherical washer 12 applied thereto is screwed on the portion of this stud bolt 7 which projects from the bolt hole 8. The nozzle clamp 6 in this condition is fixed with the clamp receiving seats 4, 5 pressed by the lower surfaces of cross-sectionally arcuately formed contact parts 9 of the bifurcated portion of the nozzle clamp and a contact part thereof at the opposite side of this bifurcated portion respectively, whereby a free end portion of the fuel injection nozzle 1 is fixed with a sealing load imparted to a nozzle packing 11. The spherical washer 12 receiving the force of the nut 10 and pressing the nozzle clamp 6, is provided so as to offset a small height difference between the clamp receiving seats 4, 5 and impart a predetermined sealing load to the fuel injection nozzle 1. In the case of a four-valve engine in which a total of four valves including two intake valves and two exhaust valves are provided in one cylinder as mentioned above, the four valves are close to one another, so that driving shafts provided with cams for driving these valves and the cams are necessarily positioned close to one another. Therefore, there is the possibility that the cams interfere with the cam shafts, other cams or fuel injection nozzle, and, moreover, many movable members are provided. This places restrictions on the layout for providing the fuel injection nozzle in the head cover. Consequently, the fuel injection nozzle clamping structure shown in Fig. 7 cannot be applied to this type of engine. In order to forcibly apply the fuel injection nozzle clamping structure of Fig. 7 to this type of engine, it becomes necessary to increase the distance between cylinders and the dimensions of the head cover, so that the space for the installation of the fuel injection nozzle clamp increases. Therefore, the nozzle clamping structure of Fig. 7 is not suitable for the miniaturization of an engine. A both end-supported type fuel injection nozzle clamping structure shown in Figs. 8 and 9 has been proposed as another type of fuel injection nozzle clamping structure. In this structure, two fuel injection nozzles are fixed by both end portions of one nozzle clamp 6. As shown in Fig. 8, bifurcated nozzle contact portions 9 are formed at both ends of the nozzle clamp 6, and a bolt insert hole 8 in an intermediate portion thereof. The nozzle clamp 6 is inserted into a clamping bolt 7 fixed to a stud boss 13 formed on a cylinder head 2, and a nut 10 with a spherical washer 12 applied thereto is screwed on a conical seat formed on an upper surface of the bolt insert hole 8, to tighten the nozzle clamp, whereby a sealing load is imparted to a nozzle packing. When the fuel injection nozzle clamping structure is thus formed to a both end-supported type structure, two fuel injection nozzles 1 can be fixed by one nozzle clamp 6, and this enables the space required to tighten the fuel injection nozzles 1 to be reduced. In, for example, a 6-cylinder V-type engine, each bank has three cylinders, and, when the both end-supported type nozzle clamp shown in Fig. 8 is used for each two adjacent fuel injection nozzles therein, the one end-supported type nozzle clamp shown in Fig. 7 has to be used for the remaining one fuel injection nozzle. A fuel injection nozzle clamping structure of the kind defined in the preamble of independent claim 1 is known from EP-A-0.491.582. In this prior art structure four nozzles are held in position by a flat bar fixed at its both ends only by two screws. Thereby it is impossible to adjust the pressure to be applied to the fuel injection nozzle, which nozzles rather are undergoing deformation and stress. Furthermore the prior art arrangement makes a sealing of the fuel injection nozzle only in the radial direction in which the nozzle abuts against the wall surface of a through-bore through the packing. Thereby it is not possible to use the prior art structure in diesel engines because of the high pressure in a cylinder bore. Summary of the Invention: The present invention has been developed with attention given to the problems with a conventional fuel injection nozzle clamping structure for an engine, and aims at providing a fuel injection nozzle clamping structure for an internal combustion engine which is adapted to fix together three series-arranged fuel injection nozzles by one nozzle clamp. The fuel injection nozzle clamping structure according to the present invention for achieving the object, applied to an engine having series arranging three fuel injection nozzles inserted into nozzle fixing bores in a cylinder head, comprises a nozzle clamp having three contacting portions aligned with the clamp receiving seats which are formed on the fuel injection nozzles, and having bolt inserted holes between the contacting portions, and clamping bolts inserted into the insert holes so as to press the fuel injection nozzles and impart sealing loads thereto. When the three series-arranged fuel injection nozzles are tightened by one nozzle clamp, the intermediate fuel injection nozzle is tightened by two clamping bolts, so that the tightening force applied to this intermediate fuel injection nozzle becomes larger than that applied to the fuel injection nozzles on both sides. In general, when the tightening force applied to a fuel injection nozzle is set not higher than a predetermined level, the sealing performance of the nozzle packing lowers. Conversely, when this tightening force is set not lower than a predetermined level, the lifting action of a needle valve cannot be made smoothly, i.e., a so-called "slowdown" of a needle valve occurs. In order to prevent a decrease in the nozzle sealing performance and the occurrence of a slowdown of a needle valve, the tightening force of the fuel injection nozzles can be set uniform by suitably selecting the shape of the nozzle clamp and the positions of the clamping bolts. As another means for preventing the above-mentioned inconveniences, the sizes of the clamp receiving seats on the fuel injection nozzles and nozzle contacting portions of the nozzle clamp are set so that a clearance occurs between the nozzle contacting portions formed at an intermediate part of the nozzle clamp and the clamp receiving seat formed on the intermediate fuel injection nozzle when the nozzle clamp is placed on the three fuel injection nozzles. When a predetermined level of tightening force is applied to the nozzle clamp by the clamping bolts, the nozzle clamp is bent, and the intermediate nozzle contacting portions engage the corresponding clamp receiving seat. The tightening force applied to the fuel injection nozzles can be set uniform by further tightening the nozzle clamp so as to impart a sealing load to the three nozzle packings. The fuel injection nozzle clamping structure described above can be suitably applied to a four-valve engine but the engine to which the present invention is applied is not limited to this engine. The present invention can also be applied to other types of internal combustion engines as long as they are provided with three series-arranged nozzles 1. The above-mentioned means formed so as to tighten three series-arranged fuel injection nozzles by one nozzle clamp enables the performance and weight of an internal combustion engine to be improved and reduced respectively, and a space in which a nozzle clamp is fixed to be secured when the engine is miniaturized. Brief Description of the Drawings: Fig. 1A is a diagram illustrating the operation of a three-point supported continuous beam, and Fig. 1B a graph showing the relation between the reaction force occurring in each fulcrum and a deflection amount; Fig. 2 is a diagram illustrating the operation of the nozzle clamp defined in Claim 2, wherein Fig. 2A is a diagram showing the condition of a nozzle clamp placed on clamp receiving seats and the condition of a beam reaching an intermediate clamp receiving seat, and Fig. 2B a graph showing the relation between the force occurring at each clamp receiving seat and a deflection amount; Fig. 3 is a cross-sectional view of a principal portion of an embodiment of the fuel injection nozzle clamping structure according to the present invention; Fig. 4 is a side view of a principal portion of what is shown in Fig. 3; Fig. 5 is a plan view of a nozzle clamp used for the embodiment shown in Fig. 3 and 4; Fig. 6 is a side view of the nozzle clamp of Fig. 5; Fig. 7 is a cross-sectional view of a conventional example of a fuel injection nozzle clamping structure; Fig. 8 is a partial plan view of another conventional example of a fuel injection nozzle clamping structure; and Fig. 9 is a side view of a principal portion of what is shown in Fig. 8. Description of the Preferred Embodiments: The fuel injection nozzle clamping structure in this embodiment is applied to a 6-cylinder V-type engine. As shown in Figs. 3 and 4, fuel injection nozzles 1 are inserted into nozzle fixing bores 3 of nozzle fixing sleeves 3a press-fitted in a cylinder head 2, and three nozzles are thus arranged in series in each bank. The two cam shafts 15 shown in the drawings are held between a cam carrier 16 fixed to the cylinder head 2 and a cam bracket 17. A reference numeral 18 shown in Fig. 3 denotes a path of a cam nose. As shown in Fig. 3, clamp receiving seats 4 are formed on both sides of the fuel injection nozzle 1. As shown in Fig. 4, one nozzle clamp 19 is disposed on three clamp receiving seats 4 provided on both sides of three fuel injection nozzles 1, in a bridge spanning manner. The clamping bolts 7 fixed between adjacent fuel injection nozzles 1 are then inserted into bolt insert holes 8, and spherical washers 12 are provided in conical recesses 8b in the nozzle clamp 19 at the end portions of these clamping bolts 7. Nuts 10 are screwed on the clamping bolts 7, which are thereby tightened so as to press the nozzle packings 11 at the free end portions of the fuel injection nozzles 1 and impart a sealing load thereto. The nozzle clamp 19 which presses three fuel injection nozzles 1 at once is made from a spring material, and shaped as shown in Figs. 5 and 6. Namely, the nozzle clamp 19 has bifurcated nozzle contacting portions 9 at both ends, nozzle contacting portions 20 at both sides of an intermediate through hole 20a, and large-thickness portions 21 having bolt insert bores 8 and extending between the nozzle contacting portions 9, 20. The cross-sectional shape of the nozzle clamp 19 is as shown in Fig. 6. The portions of the nozzle clamp 19 which are provided with the bolt insert holes 8 are formed as the large-thickness parts 21 to heighten the rigidity thereof, and the nozzle contacting portions 9 at both ends are formed to a thickness slightly smaller than that of the large-thickness parts 21 and bent downward so as to increase the elasticity thereof. The lower circumferential edges 8a of the bolt insert holes 8 are recessed so as to lessen the concentration of stress in the lower end opened portions of the holes, and conical recesses 8b are formed at the upper side of the holes 8 so that the recesses 8b receive the spherical washers 12 easily. As shown in Fig. 4, the clamp receiving seats 4 of the three fuel injection nozzles 1 are formed to the same height. As shown in Fig. 6, a lower surface 20b of the intermediate nozzle contacting portions 20 are formed higher than a line (a lower surface 21a of each large-thickness portion 21) connecting together the nozzle contacting portions 9 at both sides so that a clearance t' occurs therebetween, i.e., the clearance t' is provided so that the nozzle contacting portions 9, 9 at both sides and the intermediate nozzle contacting portions 20 do not simultaneously engage the three clamp receiving seats 4 of the three fuel injection nozzles 1. The present invention provides a nozzle clamping structure having one clamp 19 provided with nozzle contacting portions 9, 20, 9 with respect to the clamp receiving seats 4 of three fuel injection nozzles, these nozzle contacting portions 9, 20, 9 being aligned at once with the three clamp receiving seats 4 and tightened by bolts, whereby the three fuel injection nozzles can be pressed and fixed by a uniform level of force. The characteristics of the nozzle clamping structure according to the present invention reside in that it is formed so that the nozzle clamp works as a both-end supported beam in a first stage of a bolt tightening operation, and as a three-point supported beam in a second stage thereof in which the bolts are further tightened. The operation and effects of this single nozzle clamp 19, which is formed so that a clearance t' occurs between the nozzle contacting portions 20 and nozzle contacting portions 9, 9 as shown in Fig. 6, obtained when the three fuel injection nozzles 1 are pressed and fixed at once by using the same nozzle clamp 19 will now be described. First, referring to Fig. 1A, a three-point supported beam supported simultaneously at three points, in which concentrated loads (W 1 , W 2 ) are imparted to intermediate portions (k 1 × L 1 , k 2 × L 2 , wherein 0≦k≦1) of a continuous beam (nozzle clamp 19) having inter-fulcrum length L 1 , L 2 and supported on three fulcrums A, B, C will be described. The continuous beam is regarded as a simple beam including a beam having fulcrums A, B only and a beam having fulcrums B, C, and the reaction force R A , R B , R C occurring in these fulcrums can be determined on the basis of a 3-moment theorem of the strength of materials in which the bending moment at these fulcrums is handled as M A , M B , M C and an expression obtained from the balance of the bending moment (refer to, for example, "Exercise in Strength of Materials" written by Seiroku Koi, pages 106-109, issued on October 15, 1963 by the Gakkensha). When the reaction force mentioned above is calculated by using equations L 1 =L 2 =L , k 1 =k 2 =1/2 , W 1 =W 2 =P , R B >R A =R C is obtained. According to the results of the calculation, the reaction force at the fulcrums A, C becomes R A =R C =5/16×P , and R B =11/8×P and R B ≒4×R A (or R C ) are obtained. Therefore, the relation between the reaction force R A , R B , R C exerted on the fulcrums A, B, C by a load W and deflection t is as shown in Fig. 1B, i.e., the reaction force R B exerted on the fulcrum B becomes far larger than that R A , R C exerted on the fulcrums A, C. The present invention in which a clearance t' is provided between the intermediately formed clamp receiving seats and a nozzle contacting portion 20 will now be described with reference to Figs. 2 and 3. The fulcrums A, B, C shown in Fig. 1 can be replaced by the positions of the clamp receiving seats 4 on the fuel injection nozzles 1 shown in Fig. 4, and Fig. 2 illustrates a case where clamp receiving seats a, b, c are arranged at regular intervals in the same manner as the fulcrums A, B, C shown in Fig. 1, with a tightening force P of bolts applied to the respective central portions. Fig. 2 shows the principle of operation of the nozzle clamping structure according to the present invention. Referring to Figs. 2A, tightening force Fa, Fc is exerted on the clamp receiving seats a , c alone in a first tightening stage, in which a load P is imparted to a three-point supported nozzle clamp 19 as shown in Fig. 4 by screwing a nut 10 to a stud bolt 7, so that the nozzle clamp 19 functions as a simple both-end supported beam. Let Ka, Kc equal the spring constants of the nozzle clamp 19 in this case. Consequently, the tightening force Fa, Fc which the clamp receiving seats a , c receive with respect to the deflection t becomes as expressed by a straight line (1) in Fig. 2B. In a second tightening stage in which the nut 10 is further screwed to the stud bolt 7, the deflection t of the nozzle clamp 19 reaches the clearance t' (Fig. 6), and the nozzle clamp 19 which has theretofore functioned as a two-point supported beam begins to function as a three-point supported beam continuous beam with a tightening force Fb exerted on the clamp receiving seat b . In this case the tightening force Fb exerted on the clamp receiving seat b is larger than that Fa, Fc exerted on the clamp receiving seats a , c as previously described with reference to Fig. 1. However, since the distance between fulcrums of the nozzle clamp 19 decreases from 2L to L, the spring constants Ka', Kc' with respect to the clamp receiving seats a , c become larger than those Ka, Kc (Ka', Kc'>Ka, Kc), which are in the case where the tightening force is as shown by the straight line 1 ○, i.e., as shown by a straight line 2 ○ in Fig. 2B. Moreover, as referred to in the previous description, which was given with reference to Fig. 1, of the reaction force applied to the three fulcrums of a three-point supported beam, the spring constant Kb of the nozzle clamp 19 with respect to the clamp receiving seat b is larger than those Ka', Kc' with respect to the clamp receiving seats a, c (Kb>Ka', Kc'), i.e., increases about four times as described previously. Therefore, when the tightening force P for the nozzle clamp 19 is further increased, the deflection amount t of the nozzle clamp 19 further increases, so that the tightening force Fa, Fb, Fc applied to the clamp receiving seats a , b , c increases. However, as shown in Fig. 2, the angle of inclination of a straight line 3 ○ showing an increase in the tightening force Fb applied to the clamp receiving seat b is larger than that of the straight line 2 ○ showing an increase in the tightening force Fa, Fc applied to the clamp receiving seats a , c , so that a deflection amount t'' at which the two straight lines 2 ○, 3 ○ cross each other exists. It is understood that the three fuel injection nozzles can be tightened by one nozzle clamp by three equal tightening force Fa, Fb, Fc. Since the nozzle clamp 19 thus formed enables three series-arranged fuel injection nozzles 1 to be tightened at once by equal tightening force Fa, Fb, Fc, a decrease in the sealability and a "slowdown" in which the movement of the needle valve being lifted becomes slow do not occur. Accordingly, a desirable engine performance can be obtained. As described above, the fuel injection nozzle clamping structure according to the present invention is formed so that a set of three nozzles are fixed at once by one nozzle clamp. Therefore, the securing of a space for installing the fuel injection nozzle clamping structure can be done easily, so that the present invention can be applied suitably to a 6-cylinder V-type 4-valve engine in which the reduction of the dimensions and weight and the improvement of the performance have been achieved, and to an engine in which the securing of a nozzle clamp installation space is difficult, especially, a miniaturized engine. The invention defined in Claim 2, which is formed so that, when the nozzle clamp is placed on the clamp receiving seats, a clearance occurs between the intermediate nozzle contacting portion and clamp receiving seats so as to operate the nozzle clamp as a two-point supported beam in a first tightening stage, and as a three-point supported beam in a second tightening stage, is capable of easily setting equal the tightening loads imparted to the three nozzles constituting one set nozzles. This can easily prevent the occurrence of imperfect sealing of nozzle packings and a slowdown of the needle valve being lifted.

Claims: A fuel injection nozzle clamping structure applied to an engine having series arranged three fuel injection nozzles (1) for injecting fuel into cylinders, inserted into nozzle fixing bores (3) in a cylinder head (12), whereby a nozzle clamp (19) having contacting portions (9, 9, 20) at both end parts and an intermediate part thereof aligned with the clamp receiving seats (4) which are formed on said fuel injection nozzles (1), said nozzle contacting portions (9, 9) at both end parts being bifurcated, the nozzle clamp (19) having bolt inserting holes (8) between said contacting portions, and clamping bolts (7) inserted into said insert holes (8) so as to press said fuel injection nozzles and impart sealing loads thereto, characterized in that said nozzle contacting portion (20) at an intermediate part of the nozzle clamp (19) comprises peripheral parts of a wide, closed hole (20a) through which one fuel injection nozzle (1) is to be inserted. A fuel injection nozzle clamping structure according to claim 1, wherein said clamp receiving seats (4) of said fuel injection nozzles (1) and said nozzle clamp (19) are formed so that a clearance occurs between nozzle contacting portion at an intermediate part of said nozzle clamp (19) and said clamp receiving seat (4) on an intermediate fuel injection nozzle (1) when said nozzle clamp (19) is placed on said three fuel injection nozzles, said nozzle clamp (19) being bent by applying a predetermined level of tightening force thereto by said clamping bolts (7) to bring said intermediate nozzle contacting portion (20) into contact with the relative clamp receiving seat (4), and a sealing load being imparted to all of said nozzles (1) by further tightening said clamping bolts (7). A fuel injection nozzle clamping structure according to claim 2, wherein said nozzle clamp (19) has nozzle contacting portions (9, 9, 20) at an intermediate part and both end parts thereof, and clamping bolt insert holes (8) in the parts thereof which are between both end nozzle contacting portions (9, 9) and intermediate nozzle contacting portion (20), said insert hole-provided parts of said nozzle clamp (19) being formed to larger-thickness parts (21), both end parts of said nozzle clamp (19) being formed to a thickness smaller than that of said larger-thickness parts (21) to render said both end parts elastic. A fuel injection nozzle clamping structure according to claim 2, wherein, when said nozzle clamp (19) is placed in the condition of a continuous beam on said three fuel injection nozzles (1), a clearance (t') occurs between said nozzle contacting portions at an intermediate part (20) of said nozzle clamp (19) and said clamp receiving seat (4) on said intermediate fuel injection nozzle (1), said clearance (t') working to lessen a fuel injection nozzle (1) pressing force so that a substantially equal pressing force occurs on said three fuel injection nozzles (1) at a predetermined level of bolt tightening force. A fuel injection nozzle clamping structure according to claim 1, wherein said nozzle clamp (19) is made from spring material so that said nozzle clamp is readily bent.

Inventors: KIMURA HARUYOC, KIMURA, HARUYO, KIMURA, HARUYOC/O ISUZU MOTORS LIMITED
Applicants: ISUZU MOTORS LTD, ISUZU MOTORS LIMITED
Application year: 1996
Main classification: F02M61
IPC codes: F02F1, F02M61