JP3881275B2 - Two-cycle multi-cylinder engine fuel supply rail mounting structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply rail mounting structure for a two-cycle multi-cylinder engine.
[0002]
[Prior art]
In an in-cylinder injection (direct injection) multi-cylinder engine in which fuel is directly injected into a cylinder from an injector, fuel from a fuel pump is distributed to each injector via a fuel supply rail attached to the cylinder head.
[0003]
In such an in-cylinder multi-cylinder engine, fuel pressure is increasing due to demands such as atomization of fuel spray and increased penetration (strength of blowing). In the engine that has been made, it is necessary to ensure high strength also in the fuel supply rail from the viewpoint of safety, and therefore, a thick and highly rigid fuel supply rail is used.
[0004]
By the way, in the case of an in-cylinder two-cycle multi-cylinder engine, unlike a four-cycle multi-cylinder engine, there are no valves in the cylinder head, so the fuel supply rail must be attached to the cylinder head. Become. Specifically, a plurality of bosses are integrally projected on the outer surface of the cylinder head, and a bolt inserted into a plurality of bolt insertion holes penetrating the fuel supply rail is screwed to the cylinder head side boss, thereby The structure which attaches a supply rail to a cylinder head is employ | adopted.
[0005]
[Problems to be solved by the invention]
In the in-cylinder two-cycle multi-cylinder engine having such an attachment structure, the cylinder head to which the fuel supply rail is attached becomes hot during operation and thermally expands, but the fuel supply rail is relatively in the interior. It does not expand much because of low temperature fuel flow. For this reason, a thermal expansion difference is generated between the cylinder head and the fuel supply rail, and an excessive stress may be generated in the cylinder head side boss which is a mounting portion of the fuel supply rail due to the thermal expansion difference.
[0006]
Here, FIG. 8 shows a conventional example of a fuel supply rail mounting structure in a two-cycle multi-cylinder engine (see Japanese Patent Laid-Open No. 2000-179432).
[0007]
That is, FIG. 8 is a broken sectional view of the cylinder head of the engine for an outboard motor showing a conventional fuel supply rail mounting structure. The fuel supply rail 125 is attached to the cylinder head 121 by screwing a bolt 142 inserted into a bolt insertion hole 138 penetrating into the cylinder head side boss 121a. .
[0008]
However, since the screwing portion c ″ of the bolt 142 to the boss 121a is located in a shallow portion near the surface of the boss 121a, the stress caused by the difference in thermal expansion between the fuel supply rail 125 and the cylinder head 121 is caused by the bending of the bolt 142. There is a problem that excessive stress acts on the root portion of the boss 121a because it cannot be absorbed by the deformation, and the difference in thermal expansion between the fuel supply rail 125 and the cylinder head 121 is the lengthwise end portions of the fuel supply rail 121. Therefore, the largest stress is generated at the root portion of the boss 121a for attaching this portion.
[0009]
Further, since the reaction force of high fuel pressure and engine vibration act on the fuel supply rail, the stress accompanying them is applied to the boss portion which is the mounting portion of the fuel supply rail. In particular, since the fuel injection possible time (range) in the high speed range of a 2-cycle engine is shorter than that of a 4-cycle engine, the 2-cycle engine is required to have a higher fuel pressure. Stress concentration on the part becomes intense.
[0010]
The present invention has been made in view of the above problems, and its object is to provide a fuel for a two-cycle multi-cylinder engine capable of preventing concentration of excessive stress on a cylinder head side boss for mounting a fuel supply rail. It is to provide a supply rail mounting structure.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a bolt inserted into a plurality of bolt insertion holes penetrating the fuel supply rail is screwed to a plurality of bosses integrally projecting from the cylinder head. As a mounting structure of the fuel supply rail of a two-cycle multi-cylinder engine in which the fuel supply rail is attached to the cylinder head by the above and fuel supplied from the fuel supply rail is directly injected into each cylinder from the injector , the length of the fuel supply rail is The bolt is inserted into the bolt insertion holes at both ends in the vertical direction, and a screwed portion to the cylinder head side boss is provided at the base of the boss, and a gap is formed between the bolt and the bolt insertion hole. To do.
[0012]
The invention of claim 1 further provided with a threaded portion of the cylinder head side boss of the bolt to be inserted into the bolt insertion hole of the longitudinal intermediate portion of the fuel supply rail on the surface portion of the boss, The rigidity in the crankshaft direction of the base portion of the boss is set to be relatively smaller than that of the bosses at both ends located at both ends of the fuel supply rail .
[0013]
According to a second aspect of the invention of claim 1 Symbol mounting, characterized in that interposed a spacer between the fuel supply rail and the cylinder head side boss.
[0014]
Therefore, according to the first aspect of the present invention, the threaded portion of the bolt inserted into the bolt insertion hole at least at both ends in the length direction of the fuel supply rail having the largest thermal expansion difference is connected to the boss on the cylinder head side. Since a gap is formed between the bolt and the bolt insertion hole, the stress caused by the thermal expansion difference between the cylinder head and the fuel supply rail is absorbed by the bending deformation of the bolt, and a special member is provided. It is possible to prevent the concentration of excessive stress on the cylinder head side boss for attaching the fuel supply rail by only simple processing.
[0015]
Further, according to the first aspect of the invention, the thermal expansion difference in the length direction intermediate portion of the fuel supply rail is smaller than that of both end portions, the stress is relatively small acting on the boss of this part. For this reason, even if a configuration similar to the conventional configuration in which a screwed portion of the bolt inserted into the bolt insertion hole in the middle portion in the longitudinal direction of the fuel supply rail to the cylinder head side boss is provided on the surface portion of the boss is adopted. The boss will not be overstressed. Since the rigidity in the crankshaft direction of the base portion of the boss located at the middle portion in the longitudinal direction of the fuel supply rail is set to be relatively smaller than that of the boss located at both ends of the fuel supply rail, the fuel is generated by engine vibration. Even if the supply rail itself vibrates, excessive stress is not generated in the boss located in the middle portion in the longitudinal direction of the fuel supply rail.
[0016]
According to the second aspect of the present invention, since the spacer is interposed between the fuel supply rail and the cylinder head side boss, the protruding height of the boss can be kept low by the thickness of the spacer and bent to the bolt. When a load is applied, a relative displacement is allowed between the spacer and the boss, and a bending load is not easily applied to the boss, so that a large stress is not generated on the boss. If the spacer is made of a highly heat-insulating resin material or the like, the propagation of heat from the cylinder head to the fuel supply rail can be blocked, and the thermal influence on the fuel flowing through the fuel supply rail can be prevented. .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the related art and the present invention will be described below with reference to the accompanying drawings.
[0018]
< Related technology 1>
In Related Art 1, a fuel supply rail mounting structure for a two-cycle multi-cylinder engine is applied to an outboard engine. First, the overall configuration of the outboard motor will be described with reference to FIG.
[0019]
FIG. 1 is a side view of an outboard motor 1. The outboard motor 1 is attached to a stern plate 100a at the rear of a hull 100 by a clamp bracket 2, and a swivel that elastically supports a propulsion unit 3 on the clamp bracket 2. FIG. A bracket 4 is pivotally attached to a tilt shaft 5 so as to be rotatable up and down.
[0020]
The propulsion unit 3 has a housing composed of a cowling 6, an upper case 7 and a lower case 8, and a two-cycle multi-cylinder engine 10 is accommodated in the cowling 6.
[0021]
As described later, the engine 10 is provided with a crankshaft 19 (see FIGS. 2 and 3). The crankshaft 19 has an upper end of a drive shaft 11 that longitudinally cuts the interior of the upper case 7. It is connected. The lower end of the drive shaft 11 is connected to a forward / reverse switching mechanism 12 housed in the lower case 8, and a propeller shaft 13 extends horizontally rearward from the forward / backward switching mechanism 12. A propeller 14 is attached to the rear end portion that protrudes out of the lower case 8.
[0022]
Thus, when the engine 10 is driven, the rotation of the crankshaft 19 is transmitted to the drive shaft 11, and the rotation of the drive shaft 11 is switched at right angles by the forward / reverse switching mechanism 12 to the propeller shaft 13. The propulsion unit 14 is transmitted and the propeller 14 attached to the propeller shaft 13 rotates to generate a required propulsive force in the propulsion unit 3, and the propulsion force causes the hull 100 to travel at a predetermined speed.
[0023]
Next, details of the configuration of the two-cycle multi-cylinder engine 10 will be described with reference to FIGS. 2 is a plan sectional view of the engine portion of the outboard motor, and FIG. 3 is a plan sectional view of one bank of the engine.
[0024]
The two-cycle multi-cylinder engine 10 is an in-cylinder injection (direct injection) V-type six-cylinder engine, and each bank forming the V-type has three cylinders in the vertical direction (vertical in FIG. 2 and FIG. 3). Direction). As shown in FIG. 3, the cylinder body 15 of each bank is provided with a cylinder 16 for each cylinder, and a piston 17 that slides in the horizontal direction is fitted into each cylinder 16. The piston 17 is connected to a crankshaft 19 via a connecting rod 18. The crankshaft 19 is long in the crank chamber 20 in the vertical direction (perpendicular to the plane of FIG. 2 and FIG. 3), and the reciprocating linear motion of each piston 17 in the cylinder 16 is caused by the connecting rod 18 to the crankshaft 19. Is converted into a rotational motion.
[0025]
Further, as shown in FIG. 3, the cylinder head 21 attached to the end of the cylinder body 15 of each bank has a combustion chamber 22 for each cylinder. An injector 23 having an end facing the combustion chamber 22 and a spark plug 24 are attached to each cylinder, and a fuel supply rail 25 for distributing fuel to each injector 23 is attached according to the structure of the present invention.
[0026]
As shown in FIG. 2, a flywheel 26 is fixed to the upper end portion of the crankshaft 19, and a drive pulley 27 is attached to the upper portion thereof. A driven pulley 30 is attached to a rotary shaft 29 of a pump drive unit 28 disposed in the upper part of the engine 10, and an endless drive belt 31 is wound around the driven pulley 30 and the drive pulley 27. ing.
[0027]
Here, the pump drive unit 28 includes a high-pressure fuel pump 32, and the high-pressure fuel pump 32 has a fuel supply / discharge unit 33.
[0028]
On the other hand, fuel supply rails 25 are attached to the cylinder heads 21 of the banks of the engine 10 by the mounting structure according to the present invention. The injectors 23 are connected to the fuel supply rails 25 and the fuel supply rails are connected. A flexible pipe 34 extending from the discharge unit 33 is connected.
[0029]
Thus, when the engine 10 is driven, the rotation of the crankshaft 19 is transmitted to the rotation shaft 29 of the pump drive unit 28 via the drive pulley 27, the drive belt 31 and the driven pulley 30, and the rotation of the rotation shaft 29. As a result, the high-pressure fuel pump 32 is driven to pressurize the fuel to a predetermined pressure (50 to 100 kg / cm ² ). The pressurized high-pressure fuel is sent from the fuel supply / discharge unit 33 to the fuel supply rails 25 of the left and right banks via the flexible pipes 34 and supplied to the injectors 23 from the fuel supply rails 25. The fuel is directly injected into the combustion chamber 22 of each cylinder at an appropriate timing and used for combustion.
[0030]
In FIG. 2, 35 is a starter motor, 36 is a belt tensioner, and 37 is a silencer.
[0031]
Next, a structure for attaching each fuel supply rail 25 to the cylinder head 21 will be described with reference to FIGS. 4 is a front view of the cylinder head, and FIG. 5 is a sectional view taken along line AA in FIG.
[0032]
As shown in FIG. 4, four bosses 21a, 21b, 21c, and 21d are integrally projected at appropriate intervals in the vertical direction on the inner bank side of the outer surface of the cylinder head 21 that is long in the vertical direction. The fuel supply rail 25 is attached to the bosses 21a to 21d.
[0033]
Here, FIG. 5 shows an attachment structure to the boss 21d at the lowermost end of the fuel supply rail 25. A total of four bolt insertion holes 38 are provided at locations corresponding to the bosses 21a to 21d of the fuel supply rail 25. Each of the bosses 21a to 21d is formed with a cast hole 39 that reaches the root, and a circular hole 40 is formed in the upper part (near the surface) of the cast hole 39, and a long hole is formed below the hole 40. A female thread portion 41 of a is formed.
[0034]
Thus, the lower end portion of the fuel supply rail 25 is screwed into a female screw portion 41 formed on the boss 21d by inserting a male screw portion 42a having a length b of the bolt 42 inserted into the bolt insertion hole 38 formed therein. The other three locations are each attached to the boss by the same structure. Here, although the male screw part 42a is formed in the front-end | tip part of each volt | bolt 42 over length b, since each boss | hub 21a-21d has the female screw part 41 near the root part, bolt The threaded portion c of the cylinder head side bosses 21a to 21d is positioned at the roots of the bosses 21a to 21d.
[0035]
Accordingly, a predetermined gap is formed between the bolt 42 and the bolt insertion hole 38 of the fuel supply rail 25 and the circular hole 40 of the bosses 21a to 21d. Although not shown, this gap is used for positioning during assembly. The color used as is inserted.
[0036]
As shown in FIG. 4, the end of the injector 23 provided for each cylinder is inserted and fixed to the fuel supply rail 25 attached to the cylinder head 21 with the above-described structure. In FIG. 4, reference numeral 43 denotes a plug hole formed for each cylinder, and the spark plug 24 is screwed into each plug hole 43.
[0037]
By the way, in the two-cycle multi-cylinder engine 10 according to the related art 1 , the cylinder head 21 to which the fuel supply rail 25 is attached becomes high temperature during operation and thermally expands, but the fuel supply rail 25 is relatively in the interior. It does not expand much because of low temperature fuel flow. For this reason, a difference in thermal expansion occurs between the cylinder head 21 and the fuel supply rail 25, and due to this difference in thermal expansion, excessive stress is generated in the cylinder head side bosses 21a to 21d, which are mounting portions of the fuel supply rail 25. there is a possibility.
[0038]
However, in the related art 1 , a screwing portion c of the bolt 42 for attaching the fuel supply rail 25 to the cylinder head 21 to the cylinder head side bosses 21a to 21d is provided at the root portion of the boss 21a to 21d. 42 and the bolt insertion hole 38 of the fuel supply rail 25 and the circular hole 40 of the bosses 21a to 21d, a stress caused by a difference in thermal expansion between the cylinder head 21 and the fuel supply rail 25 is caused by the bolt 42. It is absorbed by the bending deformation, and excessive stress concentration on the cylinder head side bosses 21a to 21d for attaching the fuel supply rail 25 can be prevented by simple processing without providing a special member.
[0039]
The difference in thermal expansion at the middle portion in the length direction of the fuel supply rail 25 is smaller than that at both ends, and the stress acting on the two middle bosses 21b and 21c excluding the upper and lower bosses 21a and 21d is relatively small. . For this reason, the structure according to the related art 1 is adopted as the attachment structure to the bosses 21a and 21d at the upper and lower ends of the fuel supply rail 25, and the conventional structure is adopted as the attachment structure to the other two bosses 21b and 21c. May be.
[0040]
By the way, although only the attachment structure of the fuel supply rail 25 of one bank was demonstrated above, since the attachment structure of the other fuel supply rail 25 is also the same, illustration and description about this are omitted.
[0041]
< Related technology 2>
Next, Related Technique 2 will be described with reference to FIG. FIG. 6 is a view similar to FIG. 5 showing the fuel supply rail mounting structure according to Related Art 1. In this drawing, the same elements as those shown in FIG.
[0042]
In Related Art 2 , a structure as shown in the figure is adopted as a structure for attaching the upper and lower ends of the fuel supply rail 25 to the cylinder head side bosses 21a and 21d.
[0043]
That is, the bosses 21 a and 21 d at the upper and lower ends of the cylinder head 21 are kept low in height, and the spacer 44 is interposed between the bosses 21 a and 21 d and the fuel supply rail 25. An anti-rotation pin 45 is erected on the upper surface of the spacer 44, and this pin 45 is engaged with the lower surface of the fuel supply rail 25.
[0044]
Thus, the other configuration is the same as in the related art 1, and the screw portion c of the bolt 42 for attaching the fuel supply rail 25 to the cylinder head 21 to the cylinder head side bosses 21a to 21d is formed in the boss 21a. Since a gap is formed between the bolt 42 and the bolt insertion hole 38 of the fuel supply rail 25 and the circular hole 46 of the spacer 44 and the circular hole 40 of the boss 21, the cylinder head 21 and the fuel The stress caused by the difference in thermal expansion from the supply rail 25 is absorbed by the deformation of the bolt 42, and the cylinder head side bosses 21a to 21d for attaching the fuel supply rail 25 are provided only by simple processing without providing a special member. It is possible to prevent excessive stress concentration on the surface.
[0045]
Further, since the spacer 44 is interposed between the fuel supply rail 25 and the cylinder head side bosses 21a and 21d, the protruding height of the bosses 21a and 21d can be kept low by the thickness of the spacer 44, and the bolt 42 When a bending load is applied to the boss, relative displacement is allowed between the spacer 44 and the bosses 21a and 21d, and the bending load is not easily applied to the bosses 21a and 21d, so that a large stress is not generated in the bosses 21a and 21d.
[0046]
Further, if the spacer 44 is made of a resin material having a high heat insulating property, the propagation of heat from the cylinder head 21 to the fuel supply rail 25 can be blocked, and the thermal influence on the fuel flowing through the fuel supply rail 25 can be reduced. Can be prevented.
[0047]
<Form state of implementation>
Next, the shape condition of the present invention will be described with reference to FIG. 7 is a sectional view taken along the line BB in FIG. 4 showing the fuel supply rail mounting structure according to Related Art 1. In this figure, the same elements as those shown in FIG. ing.
[0048]
In the present embodiment, the bolt 42 that is inserted into the bolt insertion hole 38 in the middle portion (except the upper and lower ends) of the fuel supply rail 25 in the cylinder head side bosses 21b and 21c (see FIG. 4) is screwed. c 'is provided on the surface portions of the bosses 21b and 21c, and the rigidity of the base portions of the bosses 21b and 21c in the crankshaft direction (perpendicular to the paper surface in FIG. 7) is set at both ends of the fuel supply rail 25. , 21d (see FIG. 4).
[0049]
Here, as a specific method for making the rigidity in the crankshaft direction of the base portions of the bosses 21b and 21c relatively smaller than those of the bosses 21a and 21d located at both ends of the fuel supply rail 25, the present embodiment Therefore, a configuration is adopted in which a notch 47 is formed in the base portion of the intermediate bosses 21b and 21c to reduce the width dimension of that portion.
[0050]
In the present embodiment, the same structure as that of Related Art 1 (see FIG. 5) is adopted for the mounting structure of the upper and lower ends of the fuel supply rail 25 to the cylinder head side bosses 21a and 21d.
[0051]
By the way, in the two-cycle multi-cylinder engine according to the present embodiment, as described above, the difference in thermal expansion at the intermediate portion in the longitudinal direction of the fuel supply rail 25 is smaller than that at both ends, and the bosses 21b and 21c at this portion. The stress acting on is relatively small. Therefore, as in the present embodiment, the threaded portion c ′ of the bolt 42 inserted into the bolt insertion hole 38 in the middle portion in the longitudinal direction of the fuel supply rail 25 is connected to the cylinder head side bosses 21b and 21c. , 21c, even if a configuration similar to the conventional one is employed, excessive stress is not generated in the bosses 21b, 21c.
[0052]
Further, since the same structure (see FIG. 5) as in the related art 1 is adopted for the mounting structure of the upper and lower ends of the fuel supply rail 25 to the cylinder head side bosses 21a and 21d, the fuel supply rail 25 and the cylinder Excessive stress is not generated in the bosses 21a and 21d due to the thermal expansion difference of the head 21.
[0053]
Further, in the present embodiment, the rigidity in the crankshaft direction of the root portion of the bosses 21b and 21c located at the middle portion in the longitudinal direction of the fuel supply rail 25 is set to the bosses 21a and 21b located at both ends of the fuel supply rail 25. Therefore, even if the fuel supply rail 25 itself vibrates due to engine vibration, excessive stress is generated in the bosses 21b and 21c located in the middle portion in the longitudinal direction of the fuel supply rail 25. There is nothing.
[0054]
In the above embodiment, the present invention has been described with respect to a two-cycle multi-cylinder engine especially for an outboard motor. However, the present invention is applied to a fuel supply rail for an automobile or any other two-cycle multi-cylinder engine. Of course, the same applies to the structure.
[0055]
【The invention's effect】
As is apparent from the above description, according to the present invention, the bolts inserted into the plurality of bolt insertion holes penetrating the fuel supply rail are screwed to the plurality of bosses integrally protruding from the cylinder head. The fuel supply rail is attached to the cylinder head by the above, and the fuel supply rail mounting structure of the two-cycle multi-cylinder engine that directly injects the fuel supplied from the fuel supply rail into each cylinder from the injector, The screw is inserted into the bolt insertion holes at both ends in the lengthwise direction, and the screw is connected to the cylinder head side boss at the base of the boss, and a gap is formed between the bolt and the bolt insertion hole. An effect is obtained that it is possible to prevent excessive stress concentration on the cylinder head side boss for attaching the rail.
[Brief description of the drawings]
FIG. 1 is a side view of an outboard motor.
FIG. 2 is a plan sectional view of an engine portion of an outboard motor.
FIG. 3 is a plan sectional view of one bank of the engine for an outboard motor.
FIG. 4 is a front view of a cylinder head of the engine for an outboard motor.
5 is a view (a cross-sectional view taken along line AA in FIG. 4) showing a fuel supply rail mounting structure according to Related Technique 1. FIG.
6 is a view (similar to FIG. 5) showing a fuel supply rail mounting structure according to Related Technology 2. FIG.
7 is a diagram showing a fuel supply rail mounting structure according to the shape condition of the present invention (B-B line fracture surface view of FIG. 4).
FIG. 8 is a cutaway view showing a conventional fuel supply rail mounting structure.

Claims (2)

The fuel supply rail is attached to the cylinder head by screwing bolts, which are inserted through the plurality of bolt insertion holes provided in the fuel supply rail, into a plurality of bosses integrally projecting from the cylinder head. The fuel supply rail mounting structure of a two-cycle multi-cylinder engine that directly injects fuel to be supplied from an injector into each cylinder,
Provided at the base of the boss is a screwed portion to the cylinder head side boss of the bolt inserted into the bolt insertion hole at both ends in the length direction of the fuel supply rail;
Create a gap between the bolt and the bolt insertion hole ,
Provided on the surface portion of the boss is a screwed portion to the cylinder head side boss of the bolt that is inserted into the bolt insertion hole in the middle portion in the longitudinal direction of the fuel supply rail;
The fuel supply rail mounting of a two-cycle multi-cylinder engine characterized in that the rigidity in the crankshaft direction of the base portion of the boss is set to be relatively smaller than that of the bosses at both ends located at both ends of the fuel supply rail. Construction. The fuel supply rail mounting structure for a two-cycle multi-cylinder engine according to claim 1, wherein a spacer is interposed between the fuel supply rail and the cylinder head side boss.

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