JPH022942Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a delivery valve for a fuel injection pump.

(Technical background of the invention and its problems) A fuel injection pump used in an injection-type internal combustion engine such as a diesel engine pressurizes fuel with a reciprocating plunger and injects it through a delivery valve and an injection pipe into an injection nozzle. to be pumped to. As shown in FIG. 2, the delivery valve has a tapered seat surface 1a, which improves the sharpness of fuel injection,
A valve body 1 is formed with a suction piston 1c having a suction collar 1b for preventing the injection nozzle from sagging, a tapered seat surface 2a, and the suction collar 1b and the suction piston 1c. It consists of a valve seat 2 with a valve guide hole 2b into which the valve is inserted, a delivery spring 3, etc., and when the fuel injection is finished and the valve is closed by the spring force of the delivery spring 3, the suction collar 1b and the suction return The suction action of the piston 1c rapidly reduces the fuel pressure in the injection pipe to a certain pressure to prevent the fuel from dripping from the injection nozzle, and the pressure in the injection pipe is maintained until the next injection is performed. It performs a blocking action to maintain the

By the way, in the above conventional delivery valve, the taper angle α of the seat surface 1a of the valve body 1 is set larger than the taper angle β of the seat surface 2a of the valve seat 2, and the outer open end 2c of the seat surface 2a of the valve seat 2 Since the valve seat 2 is formed to be in line contact with the valve seat 2, it is necessary to precisely finish the end surface 2d of the valve seat 2 in order to perfect the seating properties between the two. Finishing of such end faces is very time-consuming and easy to damage during processing, resulting in a poor permissibility (pass rate) of the product.
Moreover, during use, it is easy to get scratched and the seat properties deteriorate, and due to wear of the contact part with the valve body 1, that is, the outer opening end 2c of the seat surface 2a, the contact part moves inward of the seat surface 2a. As a result, the pressure receiving area of the seat surface 1a of the valve body 1 changes, causing changes in the valve opening pressure and the injection amount. In particular, when the suction collar 1b is provided with a cutout or a hole to weaken the suction effect at low speeds, the changes in the valve opening pressure and injection amount become large. As a result, there is a problem that the injection amount in each cylinder varies, which adversely affects the operation of the engine.

(Purpose of the invention) The present invention was created in view of the above points, and aims to reduce variations in valve opening pressure and injection amount caused by wear on the seat surface of the valve seat, and to improve the direct flow rate of the product. An object of the present invention is to provide a delivery valve for a fuel injection pump.

(Summary of the invention) In order to achieve the above object, the present invention provides a delivery valve for a fuel injection pump in which the seat surfaces of the valve body and the valve seat are respectively tapered and in line contact with each other. To provide a delivery valve for a fuel injection pump, in which a taper angle is set smaller than a taper angle of a seat surface of the valve seat, and the seat surface of the valve body is brought into line contact with the inner open end of the seat surface of the valve seat. It is something.

(Embodiment of the invention) An embodiment of the invention will be described below in detail based on the accompanying drawings.

FIG. 1 shows a vertical cross-sectional view of the main parts of a delivery valve to which the present invention is applied, and the delivery valve includes a valve body 1,
The valve body 1 includes a valve seat 2 and a delivery spring 3, and the valve body 1 has a tapered seat surface 1 as described above.
a, a suction collar 1b and a suction piston 1c for improving the cutting of fuel injection and preventing the injection nozzle from sagging, and the seat surface 1a has a diameter that decreases in the direction of the suction collar 1b. It is formed with a predetermined taper angle α.

On the other hand, the valve seat 2 has a tapered seat surface 2a.
and a valve guide hole 2b are formed concentrically, the outer end 2c of the seat surface 2a opens to the end surface 2d, and the inner end 2e forms the inner diameter of the hole 2b and communicates with the hole 2b. The taper angle γ of the seat surface 2a is slightly larger than the taper angle α of the seat surface 1a of the valve body 1 (γ
>α) It is set at a predetermined angle. Incidentally, the difference Δθ (=
γ−α) is approximately 30′ to 1°30′. A suction collar 1b and a suction piston 1c of the valve body 1 are fitted into the hole 2b of the valve seat 2 so as to be slidable in the axial direction.

One end of the delivery spring 3 is pressed against the opposite-seat end surface 1d of the valve body 1, and the other end is pressed against a spring seat (not shown), thereby pressing the valve body 1 against the valve seat 2 with a predetermined spring pressure.
The taper angle α of the seat surface 1a of the valve body 1 is smaller than the taper angle γ of the seat surface 2a of the valve seat 2, and therefore,
The seat surface 1a of the valve body 1 is in line contact with the inner end 2e of the seat surface 2a of the valve seat 2. That is, the seat surface 1a of the valve body 1 is pressed into line contact with the inner end 2e of the seat surface 2a of the valve seat 2 by the spring pressure of the delivery spring 3, thereby closing the hole 2b.

Now, the inner opening end 2e of the seat surface 2a of the valve seat 2
is the same as the diameter of the hole 2b, and therefore, even if the open end 2e is worn, it is always the same as the diameter of the hole 2b and does not change. Therefore, the seat surface 1a of the valve body 1 is in line contact with the inner open end 2e of this seat surface 2a.
The contact position does not change within the range where the taper angle α is smaller than the taper angle γ (α<γ), and as a result, the pressure receiving area of the seat surface 1a does not change. That is, the pressure receiving area of the seat surface 1a of the valve body 1 is always equal to the pressure receiving area of the hole 2 of the valve seat 2.
Equal to the cross-sectional area of b.

In this way, even if the inner opening end 2e of the seat surface 2a of the valve seat 2 wears out, the opening pressure of the delivery valve, the injection amount, etc. are always maintained at the set values.

(Effects of the invention) As explained above, according to the invention, in a delivery valve for a fuel injection pump in which the seat surfaces of the valve body and the valve seat are respectively tapered and in line contact with each other, the seat surface of the valve body is The taper angle is set smaller than the taper angle of the seat surface of the valve seat, and the seat surface of the valve body is brought into line contact with the inner opening end of the seat surface of the valve seat, so that the seat surface of the valve seat Even if the contact portion with the seat surface of the valve body is worn, the valve opening pressure and the injection amount do not change, and as a result, it is possible to extremely reduce the variation in the injection amount. In addition, since the seat surface of the valve body is in line contact with the inner open end of the seat surface of the valve seat, surface finishing of the outer open end of the seat surface of the valve seat is not required, reducing the amount of finished surface and making it easier to process during processing. The occurrence of scratches is reduced, the perpendicularity rate is improved, and manufacturing costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part showing an embodiment of a delivery valve for a fuel injection pump according to the present invention, and FIG. 2 is a vertical cross-sectional view of a main part of a conventional delivery valve. 1... Valve body, 2... Valve seat, 1a, 2a... Seat surface, 3... Delivery spring.

Claims (1)

[Scope of utility model registration request] In a fuel injection pump delivery valve in which the seat surfaces of a valve body and a valve seat are respectively tapered and in line contact with each other, the taper angle of the seat surface of the valve seat is set to be larger than the taper angle of the seat surface of the valve body. ,
A delivery valve for a fuel injection pump, characterized in that a seat surface of the valve body is brought into line contact with an inner opening end of a seat surface of the valve seat.