JPH0530460U - Fuel injection nozzle - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable the injection pressure of the fuel injection nozzle to be set high. [Structure] The oil sump chamber 12 includes a straight portion 20 and an arc portion 2.
It consists of 1. The tip of the fuel supply hole 14 is opened across the straight portion 20 and the arc portion 21. The inner surface of the portion of the fuel supply hole 14 that opens to the straight portion 20 and the wall surface of the straight portion 20 intersect at a substantially right angle. When the front end opening of the fuel supply hole 14 is viewed from the front, it becomes as shown in FIG. The above-mentioned opening in the straight portion 20 has a substantially semicircular cross section, and the radius of curvature at the point "B" closest to the guide hole 11 and its vicinity is much larger than that of the conventional one, and stress concentration does not occur in this portion. Therefore, even if the injection pressure is set higher than in the conventional case, the partition wall 19 between the guide hole 11 and the fuel supply hole 14 will not be damaged.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention mainly relates to a fuel injection nozzle in a fuel injection device used for a diesel engine.

[0002]

[Prior Art]

 There are various types of fuel injection nozzles such as Hall type, pintle type, and throttle type, and among the Hall type fuel injection nozzles, there is also a long stem type.

A long-stem type Hall-type fuel injection nozzle is disclosed in JP-A-56-88959, and the basic structure thereof is as shown in FIG. 4 (A). The fuel injection nozzle has a nozzle body 10 and a needle 50. A guide hole 11 extending downward from the upper surface of the nozzle body 10 is formed, and the tip of the guide hole 11 is open to the oil sump chamber 12. The oil sump chamber 12 bulges outward in the radial direction from the guide hole 11 in a substantially semicircular cross section, and the tip of a fuel supply hole 14 extending obliquely downward from the upper surface of the nozzle body 10 is bulged in the bulging portion 13. It is open. A fuel passage 15 extends further downward from the oil sump chamber 12, and a valve seat 16 and a sack portion 17 each having a tapered surface are provided below the fuel passage 15. Further, a plurality of injection holes 18 connected to the sack portion 17 are formed through the tip of the nozzle body 10.

On the other hand, the needle 50 is provided with a guide rod portion 51, a stem portion 52, and a seal portion 53 in order from the top. The guide rod portion 51 is slidably inserted in the guide hole 11 of the nozzle body 10, the stem portion 52 is freely inserted in the fuel passage 15 of the nozzle body 10, and the seal portion 53 is the valve seat of the nozzle body 10. 16 is arranged so that it can be seated and separated.

The needle 50 is urged downward by a nozzle spring (not shown), so that the seal portion 53 is normally seated on the valve seat 16 and the injection hole 18 is closed. When fuel is pumped from the fuel injection pump (not shown) to the oil sump chamber 12 through the fuel supply hole 14 and the fuel in the oil sump chamber 12 is boosted to a valve opening pressure or higher, the needle 50 causes the needle spring to move. Is lifted upward against the spring force of the needle 50, and as a result, the seal portion 53 of the needle 50 separates from the valve seat 16 to open the injection hole 18, and fuel is injected from the injection hole 18.

[0006]

[Problems to be solved by the device]

 By the way, in recent years, the injection pressure of fuel tends to be increased due to exhaust gas regulations for diesel engines. However, in the case of the conventional fuel injection nozzle, there is a limit to the increase range of the injection pressure. This is because, when the injection pressure was raised above a predetermined value, the opening of the fuel supply hole 14 with respect to the oil sump chamber 12 in the nozzle body 10 was damaged.

More specifically, as shown in FIG. 4 (B), in the conventional fuel injection nozzle, the fuel supply hole 14 obliquely projects into the bulging portion 13. Here, since the cross-sectional shape of the fuel supply hole 14 is circular and the cross-sectional shape of the bulging portion 13 is substantially semicircular, the front end opening of the fuel supply hole 14 opening to the bulging portion 13 is viewed from the front thereof. (That is, when viewed from the direction of arrow A in the figure), the shape is as shown in FIG. 4 (C), and the radius of curvature at the “B” point closest to the tip opening of the guide hole 11 is extremely large. small. As a result, when the internal pressure is applied to the oil sump chamber 12, the bending stress and the tensile stress are concentrated at the point "B". Moreover, the partition 19 between the tip of the guide hole 11 and the tip of the fuel supply hole 14 has an extremely thin wall thickness. Therefore, if stress concentration occurs at the point “B”, the partition 19 may crack. Inferred.

In order to prevent the partition wall 19 from being damaged, the simplest method is to increase the wall thickness of the partition wall 19. However, there are design restrictions and processing restrictions, and so on. Was impossible. The present invention has been made in view of the above-mentioned problems of the conventional technique, and an object thereof is to provide a fuel injection nozzle that is robust and can set the injection pressure high.

[0009]

[Means for Solving the Problems]

 This invention was made in order to achieve the above-mentioned object, and its gist is (a) the guide hole, the oil sump chamber which is connected to the tip opening of the guide hole, and the end of which is opened to the oil sump chamber to feed the fuel. A nozzle body having a fuel supply hole for supplying to the sump chamber and an injection hole connected to the oil sump chamber, and (b) in a direction in which the guide hole of the nozzle body is slidably inserted to close the nozzle hole. A fuel injection nozzle that is energized and has a needle that is lifted by an increase in fuel pressure in the oil sump chamber to open an injection hole, and a side of the tip of the fuel supply hole near the guide hole. The fuel injection nozzle is characterized in that the inner surface of is arranged so as to be substantially orthogonal to the wall surface of the oil sump chamber.

[0010]

[Action]

 By arranging the inner surface of the tip of the fuel supply hole, which is closer to the guide hole, and the wall surface of the oil storage chamber so as to be substantially orthogonal to each other, the radius of curvature of the tip opening of the fuel supply hole near the guide hole Can be made larger than before. As a result, when the internal pressure applied to the oil sump chamber is the same, the stress applied to the portion near the guide hole at the tip opening of the fuel supply hole becomes smaller than before. Therefore, the injection pressure can be made higher than before without increasing the thickness of the partition wall between the guide hole and the fuel supply hole.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings from FIG. 1 to FIG. The description of the same aspects as those of the conventional fuel injection nozzle will be omitted, and only the differences will be described. FIG. 1 (A) is a cross-sectional view around the oil sump chamber 12 in the fuel injection nozzle according to this invention. The difference between this fuel injection nozzle and the conventional fuel injection nozzle is the shape of the oil sump chamber 12. The oil sump chamber 12 in the fuel injection nozzle according to the present invention has a straight portion 20 which is orthogonal to the axis of the guide hole 11 and linearly bulges outward, and an arc portion formed at the tip of the straight portion 20. 21 and 21.

Also in this fuel injection nozzle, the cross-sectional shape of the fuel supply hole 14 is circular, and its axis is arranged slightly inclined with respect to the axis of the guide hole 11. The tip of the fuel supply hole 14 opens across the straight portion 20 and the arc portion 21 of the oil sump chamber 12, and the center of the fuel supply hole 14 intersects the branch line between the straight portion 20 and the arc portion 21. It is arranged as follows. By doing so, the inner surface of the portion of the fuel supply hole 14 that opens to the straight portion 20 and the wall surface of the straight portion 20 intersect at a substantially right angle. FIG. 1 (B) is a view of the front end opening of the fuel supply hole 14 opening in the oil sump chamber 12, as viewed from the front side thereof, and is a view corresponding to FIG. 4 (C) in the description of the prior art. As is clear from this figure, the opening in the straight portion 20 has a substantially semicircular cross section, and the radius of curvature at the "B" point closest to the guide hole 11 and its vicinity is much larger than that of the conventional one. ..

As a result, even when the internal pressure is applied to the oil sump chamber 12, the stress concentration of bending stress and tensile stress unlike the conventional case does not occur at the “B” point near the guide hole 1 and its vicinity. Therefore, compared with the case where the same amount of internal pressure is applied to the oil sump chamber 12, the stress at the "B" point and its vicinity is much smaller in this fuel injection nozzle than in the conventional case. In other words, when the wall thickness of the partition wall 19 between the guide hole 11 and the fuel supply hole 14 is made the same as the conventional one, this fuel injection nozzle applies a higher internal pressure to the oil sump chamber 12 than the conventional one. Can be added. Therefore, the injection pressure of the fuel injection nozzle can be made higher than before.

FIG. 2A is a sectional view around the oil sump chamber 12 in another embodiment. The oil sump chamber 12 in this embodiment is formed so as to be surrounded by three wall surfaces of a top surface 22, a bottom surface 23 and a side surface 24. The upper surface 22 is a tapered surface that is inclined slightly downward, the bottom surface 23 is a sulate surface that extends outward so as to be orthogonal to the axis of the guide hole 11, and the side surface 24 has an arc shape and is the upper surface 22. It connects to the bottom surface 23. The tip of the fuel supply hole 14 opens to the upper surface 22 of the oil sump chamber 12, and the fuel supply hole 14 is arranged so that the axial center thereof is orthogonal to the upper surface 22. In this case, when the front end opening of the fuel supply hole 14 opening to the oil sump chamber 12 is viewed from the front, it has a perfect circle as shown in FIG. 2 (B). Therefore, as in the case of the first embodiment, when the internal pressure applied to the oil sump chamber 12 is the same, the stress at the "B" point closest to the guide hole 11 and its vicinity becomes much smaller than in the conventional case. The thin partition wall 19 is not damaged even if the injection pressure is increased.

FIG. 3 is a sectional view around the oil sump chamber 12 in yet another embodiment. The oil sump chamber 12 in this embodiment includes a straight portion 25 which is orthogonal to the axis of the guide hole 11 and linearly bulges outward, and an arc portion 26 which is connected to the tip of the straight portion 25 and has a substantially semicircular cross section. It consists of In this embodiment, the center "P" of a virtual circle inscribed in the arc portion 26 is arranged on the extension of the center of the fuel supply hole 14, and the tip of the fuel supply hole 14 is located in the oil sump chamber 12 It has an opening in the arc portion 26. By doing so, the inner surface of the tip of the fuel supply hole 14 intersects the wall surface of the oil sump chamber 12 at a right angle, and the front end opening of the fuel supply hole 14 that opens into the oil sump chamber 12 is viewed from the front. Then, it becomes almost circular. Therefore, as in the case of the first and second embodiments described above, when the internal pressure applied to the oil sump chamber 12 is the same, the stress at the point “B” closest to the guide hole 11 and its vicinity is It is much smaller than before, and even if the injection pressure is increased, the thin partition wall 19 is not damaged.

The present invention is not limited to the above-mentioned embodiment and various modes can be adopted. For example, each of the above-described embodiments is an example applied to a long-stem type Hall-type fuel injection nozzle, but it is also applicable to a Hall-type fuel injection nozzle other than a long-stem type fuel injection nozzle. It can also be applied to an injection nozzle. Further, the shape of the oil sump chamber is not limited to that of the embodiment, and various shapes can be adopted.

[0017]

[Effect of the device]

 As described above, according to the present invention, the inner surface of the tip of the fuel supply hole, which is close to the tip opening of the guide hole, and the wall surface of the oil sump chamber are arranged substantially orthogonal to each other. , When the internal pressure applied to the oil sump chamber is the same, the stress applied to the partition wall between the guide hole and the fuel supply hole becomes smaller than before, so the injection pressure of the fuel injection nozzle is set higher than before. The excellent effect of being able to do is exhibited.

[Brief description of drawings]

FIG. 1A is a cross-sectional view around an oil sump chamber of a fuel injection nozzle in a first embodiment, and FIG. 1B is a projection view of a tip opening of a fuel supply hole as seen from the front thereof.

FIG. 2 shows a fuel injection nozzle according to a second embodiment, and FIGS. 2A and 2B are views corresponding to FIGS. 1A and 1B, respectively.

FIG. 3 (A) of a fuel injection nozzle in a third embodiment.
It is a sectional view corresponding to.

FIG. 4A is a sectional view of a conventional fuel injection nozzle,
(B) is an enlarged cross-sectional view around the oil sump chamber, and (C) is a projection view of the front end opening of the fuel supply hole as viewed from the front thereof.

[Explanation of symbols]

 10 Nozzle body 11 Guide hole 12 Oil sump chamber 14 Fuel supply hole 18 Injection hole 50 Needle

Claims (1)

[Scope of utility model registration request] (A) A guide hole, an oil sump chamber connected to a tip opening of the guide hole, a fuel supply hole for opening the tip to the oil sump chamber to supply fuel to the oil sump chamber, and an oil sump chamber (B) It is slidably inserted in the guide hole of the nozzle body and is biased in the direction to close the nozzle hole, and the pressure rise of the fuel in the oil sump chamber In the fuel injection nozzle including a needle that is lifted by the needle to open the injection hole, the inner surface of the tip of the fuel supply hole near the guide hole is substantially orthogonal to the wall surface of the oil sump chamber. A fuel injection nozzle characterized by being arranged.