JP3448963B2 - Injection nozzle cooling device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device for an injection nozzle which cools the inside of the injection nozzle which supplies fuel to the combustion chamber of an internal combustion engine as a spray.

[0002]

2. Description of the Related Art An injection nozzle usually has a nozzle body, which is the main body of the injection nozzle, and a needle valve that can slide up and down with respect to a valve seat in the nozzle body. When the opened injection hole is opened, the fuel stored in the nozzle body is injected as a spray into the combustion chamber. Then, in order to inject the fuel as a spray, it is necessary to maintain the inside of the nozzle body at a high pressure, and therefore the temperature of the injection nozzle becomes high. In addition, unless the internal temperature of the nozzle, which rises under the influence of the high-speed movement of the needle valve and the heat of combustion of fuel, is cooled, the fuel density decreases and abnormal needle valve wear occurs,
This will interfere with driving.

For this reason, various proposals have heretofore been made regarding cooling of the injection nozzle. For example, Japanese Utility Model Laid-Open No. 48-76323, which is a first prior art document, discloses a cooling type fuel injection valve in which a cooling oil inlet and an outlet are held down by an injection valve spring retainer. Japanese Utility Model Laid-Open No. 50-13831, which is a technical document, discloses a fuel injection valve cooling device in which a needle valve is formed in a hollow shape to communicate with a fuel collection chamber and leaked fuel flows into the needle valve. It is disclosed.

In Japanese Utility Model Laid-Open No. 62-90976, which is a third prior art document, a needle valve which is actuated in the valve opening direction according to the hydraulic pressure supplied to the fuel chamber, and the needle valve An injection nozzle is shown, which is provided with a reflux cooling passage that surrounds the tip-side stem portion and leaks fuel leaking from the fuel chamber to the outside of the nozzle body.

[0005]

In the first prior art described above, the cooling oil inlet and outlet are held by the spring holder,
Since the flow path is provided on the outer wall of the nozzle, the thickness increases, and the outer shape of the spring retainer becomes large, which may make it unusable in a small engine. In the second conventional technique,
Although the needle valve is hollow and cooling is performed through the leaked fuel, the cooling effect is small because cooling is performed by convective heat conduction without forcibly passing the fuel. Further, in the third conventional technique, since the cooling passage is provided outside the nozzle body, there is a problem that the thickness increases as in the first conventional technique, and further, the cooling passage is connected to the fuel supply passage. Therefore, there was a problem that high-pressure fuel escaped to the cooling passage.

SUMMARY OF THE INVENTION The present invention is intended to solve such a conventional problem, and an object thereof is to provide a cooling fuel passage which reciprocates concentrically in the longitudinal direction inside a needle valve,
Cooling fuel from the feed pump is supplied from the inlet opened on the outer wall of the sliding seal part of the needle valve, and leakage of combustion fuel is caused to flow back from the outlet on the oil collecting side of the fuel, thus ensuring good cooling efficiency of the injection nozzle. It is intended to provide a cooling device.

[0007]

To achieve the above object, in the present invention, in a cooling device for an injection nozzle, which cools a needle valve sliding in a nozzle body of the injection nozzle, the needle valve is closed at its tip. The rear end is opened, the inside is made into a cylindrical cavity communicating with the opening, the outer cylinder with the pores for cooling fuel inlet provided in the wall near the rear end, and the cylinder with both the front and rear ends opened The closing portion provided on the outer periphery of the rear end closes the rear end of the outer cylinder and the concentric circle is formed in the cavity of the outer cylinder without the tip of the cylinder contacting the inner wall of the outer cylinder. And a cooling fuel passage configured to supply fuel from a feed pump to the pores, and an inner cylinder rear end. Store the fuel discharged from the opening of the An oil collecting chamber in which a spring that elastically springs in the direction is disposed, and an escape passage that discharges the fuel contained in the oil collecting chamber to the outside, and allows cooling fuel to flow in through the pores and the outer cylinder. After flowing through the gap with the inner cylinder, the oil flows through the inner cylinder to the oil collecting chamber.
Further, a spiral flow path may be formed between the outer wall surface of the inner cylinder and the inner wall surface of the outer cylinder.

[0008]

[Operation] Since the fuel is pressure-fed from the feed pump to the cooling fuel passage provided so as to reciprocate concentrically in the longitudinal direction inside the needle valve, the inside of the needle valve is strongly cooled by convective heat conduction. The cooled fuel is combined with the leakage fuel of the combustion fuel and recirculated.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a vertical sectional view of a first embodiment of a cooling device for an injection nozzle according to the present invention and an enlarged sectional view of the vicinity of a sliding seal portion thereof. In FIG. 1, reference numeral 1 denotes a nozzle body, which is joined to an upper holder body 3 by a nut portion 17 by a sliding seal portion, and a needle valve accommodating portion 11 for accommodating a needle valve 2 is provided at an axial center of the nozzle body 1. Has been formed. The needle valve accommodating portion 11 has a valve seat 12 formed by narrowing the tip end side in a tapered shape, and a small dome portion 13 is bulged at the end portion of the nozzle body 1 in the tip end direction of the valve seat 12 The injection hole 14 communicating with the housing portion 11 is opened. In addition, at a position in the middle of the needle valve accommodating portion 11 in the longitudinal direction, that is, at a position corresponding to the step portion 21 formed in the middle of the needle valve 2, an annular shape expanded in the outer peripheral direction of the nozzle body 1 is provided. An oil sump 15 is formed. A high-pressure fuel passage 31 is connected to the oil sump 15, and high-pressure fuel is supplied from a fuel inlet 32 provided at the upper end of the holder body 3.

The needle valve 2 is a needle valve accommodating portion 11 of the nozzle body.
It is slidable with respect to the valve seat 12 and movable up and down with respect to the valve seat 12. A step portion 21 is provided in the middle of the outer wall of the needle valve 2.
Is formed, and the portion in the valve seat direction is reduced in diameter. As shown in FIG. 1, the needle valve 2 according to the present embodiment has two types of cylinders of different thicknesses that are concentrically overlapped with each other, and the gap between them and the hole of the shaft core serve as a cooling fuel passage. Therefore, the lower end of the outer cylinder 22 is closed to form a conical surface corresponding to the valve seat 12, and the inner wall of the upper end of the outer cylinder 22 is engaged with the outer wall of the inner cylinder 23 to be closed. Outer cylinder 22 near the closing portion 24
A pore 25 is opened in the
A passage that concentrically reciprocates in the longitudinal direction inside the needle valve 2 is formed with an axial hole in the upper portion of the inner cylinder 23 as an outlet.

On the other hand, in the portion of the inner wall of the needle valve accommodating portion 11 corresponding to the pore 25, as shown in the enlarged cross-sectional view of FIG. 1, the annular portion 1 is engraved toward the outer periphery of the nozzle body 1.
6 is provided so that even if the needle valve 2 rotates with respect to the axis while repeating sliding, the pores 25 always face any part of the annular portion 16. Reference numeral 33 is a low-pressure fuel flow path, which is provided with the low-pressure fuel inlet 34 provided in the holder body 3 and the annular portion 1.
6 and the low-pressure fuel supplied from the feed pump described later through the annular portion 16 and the pores 25
It is a flow path that supplies it to the inside.

Reference numeral 35 is an oil collecting chamber for leaking fuel, which is the needle valve accommodating portion 1
A spring 36 that is provided in the holder body 3 on the extension of 1 and that presses down the needle valve 2 is accommodated. Oil collection chamber 35
Collects fuel leaking along the outer peripheral surface of the needle valve 2 from the oil sump 15 to which the fuel is pressure-fed from the fuel inlet 32 through the high-pressure fuel passage 31, and also from the hole of the axial center of the needle valve 2. Collect the low pressure fuel for cooling that escapes. The fuel collected is
It is guided to a leak-off outlet 38 via a relief flow path 37 connected above the oil collecting chamber 35.

FIG. 2 is a block diagram showing a fuel path of such an embodiment. In FIG. 2, 5 is a fuel injection pump main body, 51 is each injection pump, 52 is a feed pump, and 6 is a fuel tank. Is. The fuel in the fuel tank 6 is supplied to the injection pump body 5 and the low-pressure fuel inlet 34 of the injection nozzle via the feed pump 52. The high-pressure fuel supplied by the operation of the injection pump 51 is pumped to the fuel inlet 32 of the injection nozzle. The fuel from the leak-off outlet 38 is returned to the fuel tank 6.

Next, the operation of the present embodiment thus constructed will be described. The high-pressure fuel pumped to the fuel inlet 32 is
The oil reaches the oil sump 15 via the high-pressure fuel passage 31. Here, according to the change of the high pressure fuel pressure due to the operation of the injection pump 51,
The needle valve 2 slides on the needle valve accommodating portion 11, and fuel is sprayed from the injection hole 14 of the nozzle body 1. Needle valve 2 and needle valve accommodating portion 11
The fuel leaking from the gap between and is collected in the oil collecting chamber 35.

On the other hand, the fuel supplied from the feed pump 52 to the low-pressure fuel inlet 34 reaches the annular portion 16 through the low-pressure fuel passage 33 provided in the holder body 3, and passes through the fine hole 25 to reach the needle valve 2. Enter inside. From there, it flows through the gap between the outer cylinder 22 and the inner cylinder 23, which is the cooling fuel passage, to the tip. Then, it enters the axial center hole of the inner cylinder 23, flows upward, and eventually flows into the oil collecting chamber 35 of the holder body 3. In this way, after flowing along the outer surface of the inner cylinder 23 inside the needle valve, it flows through the hole inside the inner cylinder 23, and so on.
Since the low-pressure fuel reciprocates along the concentric path in the longitudinal direction, the needle valve 2 can be sufficiently cooled. The leaked high-pressure fuel that has flowed into the oil collecting chamber 35 and the cooled fuel flow from the leak-off outlet 38 to the fuel tank 6 and are returned to the fuel tank 6, and are again delivered by the feed pump 52.

FIG. 3 is a sectional view of a needle valve 2'in the second embodiment of the present invention, which is a modification of the needle valve of the first embodiment. Therefore, as the outer cylinder 22 ', the same one as the outer cylinder 22 of the needle valve 2 is used, and similarly has the pore 25' which serves as the fuel inlet. The inner cylinder 23 'is
A continuous spiral convex portion 231 'having a rough pitch is formed on the outer wall surface as a means for rotating the fuel spirally, and is concentrically attached to the outer cylinder 22'. Pore 25
When the fuel is pressure-fed through the inner cylinder 23 ', the fuel flowing in the passage between the two cylinders is guided to the continuous convex portion 231' of the outer wall surface of the inner cylinder 23 'and spirally rotates to rotate the inner cylinder 23'. It flows to the lower end, then flows out from the other end through the hole of the axial center of the inner cylinder 23 '.

In the second embodiment constructed as described above,
As in the case of the first embodiment, the fuel supplied from the feed pump to the annular portion 16 of the nozzle body flows from the pores 25 'of the needle valve 2'to the gap between the outer cylinder 22' and the inner cylinder 23 '. Inflow, but on the outer wall surface of the inner cylinder 23 ', a spiral convex portion 231'
Is formed, a spiral flow is made between the two cylinders in the direction of the dashed arrow in the figure. In the meantime, the wall surfaces of the outer cylinder 22 'and the inner cylinder 23' are sufficiently contacted to efficiently remove heat, and finally, the heat flows into the oil collecting chamber 35 through the axial hole of the inner cylinder 23 '.

In the illustrated example, a spiral continuous projection is provided on the outer wall surface of the inner cylinder as means for rotating and flowing the fuel in a spiral shape. The protrusion may be formed, only the protrusion may be formed on the inner wall surface of the outer cylinder, or a thin piece may be used instead of the protrusion.

[0019]

As described above, according to the present invention, the cooling fuel passage provided in the needle valve and reciprocating concentrically in the longitudinal direction,
Since the fuel is supplied from the feed pump and the inside of the needle valve is cooled by the fuel, a cooling device for the injection pump having a high cooling effect can be obtained. Particularly, the cooling fuel passage formed in a spiral shape has a large cooling effect.

Further, in the present invention, since the cooling fuel passage is inside the needle valve, the outer shape of the injection nozzle does not increase, and the shape is the same as the conventional one. Further, the cooling fuel is forcibly fed by the feed pump, so that the convection current is generated. It has more cooling effect than the conventional one. Further, since the cooling fuel passage is separate from the high pressure fuel supply passage for combustion, there is an advantage that the high pressure fuel does not escape to the low pressure side and the high pressure is maintained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a first embodiment of an injection nozzle cooling device according to the present invention, and an enlarged sectional view in the vicinity of a sliding seal portion thereof.

FIG. 2 is a block diagram showing a fuel passage of this embodiment.

FIG. 3 is a sectional view showing a needle valve portion in the second embodiment.

[Explanation of symbols]

1 ... Nozzle body, 11 ... Needle valve accommodating part, 12 ... Valve seat, 1
4 ... Nozzle hole, 15 ... Oil sump, 16 ... Annular part, 2 ... Needle valve, 2
2 ... Outer cylinder, 23 ... Inner cylinder, 24 ... Closure part, 25 ... Pores, 3
... Holder body, 31 ... High pressure fuel passage, 32 ... Fuel inlet, 33 ... Low pressure fuel passage, 34 ... Low pressure fuel inlet, 35 ...
Oil collection chamber, 37 ... Escape channel, 38 ... Leak off outlet, 51
... injection pump, 52 ... feed pump, 6 ... fuel tank

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02M 53/04 F02M 61/10 F02M 61/16

Claims (2)

(57) [Claims] 1. A cooling device for an injection nozzle that cools a needle valve that slides in a nozzle body of the injection nozzle, wherein the needle valve has a cylindrical shape in which a front end is closed and a rear end is opened, and the inside is communicated with the opening. An outer cylinder that is hollow and has pores to be used as a cooling fuel inlet on the wall near the rear end, and a cylinder that is open at both the front end and the rear end, and has a closed portion provided on the outer periphery of the rear end. Attached to the rear end of the outer cylinder so that the rear end of the outer cylinder is closed and the tip of the cylinder is concentrically arranged in the cavity of the outer cylinder without contacting the inner wall of the outer cylinder. And a cooling fuel passage for supplying the fuel from the feed pump to the pores, and the fuel discharged from the opening at the rear end of the inner cylinder. An oil collecting chamber in which a spring for elastically ejecting the And an escape passage for discharging the fuel contained in the oil collecting chamber to the outside, allowing the cooling fuel to flow from the pores and flowing through the gap between the outer cylinder and the inner cylinder, A cooling device for an injection nozzle, wherein the cooling device flows through the oil collection chamber. 2. A spiral flow path is formed between the outer wall surface of the inner cylinder and the inner wall surface of the outer cylinder.
Cooling device for the jet nozzle described.