Valve seat machining method

Abstract

This invention provides a technology that can suitably improve the oiltightness of the needle and valve seat in a fuel injection valve. [Solution] The valve seat processing method is a method applied to a fuel injection valve having a needle and a valve seat. The valve seat processing method includes the step of shaping the valve seat while heating or cooling three or more locations in the circumferential direction, which correspond to the corners of a polygon, to different temperatures from the other locations when the valve seat is viewed from above.

Description

Technical Field

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[0001] The present disclosure relates to a method for machining a valve seat of a fuel injection valve.

Background Art

[0002] In a fuel injection valve of an internal combustion engine, a machining method is known in which an annular groove is provided at the tip of a needle so that the tip elastically deform when the tip of the needle seats on the valve seat (valve seat) of the valve body (for example, see Patent Document 1).

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a technique capable of suitably enhancing the oil tightness of a needle and a valve seat in a fuel injection valve.

Means for Solving the Problems

[0005] One aspect of the present disclosure is a method for machining a valve seat of a fuel injection valve having a needle and a valve seat. In that case, the valve seat machining method, as an example, when the valve seat is viewed in a plan view, the shape machining of the valve seat may be performed in a state where the temperature of three or more sites in the circumferential direction and sites corresponding to the corners of a polygon are heated or cooled to a temperature different from that of other sites.

Effects of the Invention

[0007] [Figure 1] This is a cross-sectional view showing an example of the schematic configuration of a fuel injection valve in an internal combustion engine according to an embodiment. [Figure 2] This figure illustrates an example of a valve seat processing method in an embodiment. [Figure 3] This figure schematically shows an example of the shape of the valve seat after processing in the embodiment. [Modes for carrying out the invention]

[0008] Fuel injectors for internal combustion engines commonly utilize a needle and valve seat. In such fuel injectors, improving the roundness of the valve seat is required to enhance oiltightness when the needle is seated against it. However, increasing the roundness of the valve seat during the fuel injector manufacturing process demands precise machining techniques, potentially increasing the cycle time and manufacturing cost. Therefore, there is a need for a technology that can improve oiltightness while suppressing increases in cycle time and manufacturing costs.

[0009] As a result of the inventors of this disclosure conducting diligent experiments and verifications regarding the above-mentioned requirements, it has been found that if the deviation between the center of the needle and the center of the valve seat when the needle sits on the valve seat can be kept to a minimum, the oiltightness can be improved without precisely increasing the roundness of the valve seat. We gained the insight that it is possible.

[0010] Therefore, in the valve seat processing method according to this disclosure, when the valve seat is viewed from above, the valve seat is shaped while the temperature of three or more locations in the circumferential direction, which correspond to the corners of a polygon, is heated or cooled to a different temperature from the other locations. In one example, the shaping process may be a polishing process such as lapping or polishing applied to a valve seat produced through processes such as molding and sintering.

[0011] According to the valve seat processing method described herein, when the valve seat is placed at room temperature after shaping is complete, the temperature of the heated or cooled parts decreases or rises to room temperature, causing three or more of these parts to contract or expand. As a result, the shape of the valve seat in plan view becomes a substantially polygonal shape with three or more parts that are indented or bulging. When a needle is seated on such a valve seat, the seating position of the needle is positioned by parts of the valve seat that correspond to three or more sides of the polygon. By adjusting the position and number of parts that are heated or cooled during shaping, it becomes possible to position the needle in a desired position (i.e., a position where the deviation between the center of the needle and the center of the valve seat is minimized). In this case, the position and number of parts that are heated or cooled on the valve seat may be determined so that there are at least three or more parts that position the needle.

[0012] <Embodiment> The following describes specific embodiments of the present invention with reference to the drawings. The dimensions, materials, shapes, relative arrangements, etc., of the components described in these embodiments are not intended to limit the technical scope of the invention to those unless otherwise specified.

[0013] (Fuel injection valve) In this embodiment, an example of applying the present disclosure to a fuel injector of an internal combustion engine will be described. Figure 1 is a cross-sectional view showing an example of the schematic configuration of the fuel injector 1 in this embodiment. Note that only the configuration around the injection port of the fuel injector 1 is shown in Figure 1.

[0014] The fuel injector 1 in this embodiment comprises a cylindrical valve body 10, a cylindrical needle 11 housed inside the valve body 10 so as to be movable in the axial direction of the valve body 10, a cylindrical valve seat 12 fixed to the tip of the valve body 10 (lower end in Figure 1), and an injection plate 13 fixed to the tip of the valve seat 12 (lower end in Figure 1). The valve body 10 is configured such that fuel flows through the inside of the valve body 10 (the gap between the inner circumferential surface of the valve body 10 and the outer circumferential surface of the needle 11). The tip portion 110 of the needle 11 is tapered, with its outer diameter decreasing as it approaches the tip. Of the inner circumferential surface of the valve seat 12, the portion 120 on the injection plate 13 side is tapered, with its inner diameter decreasing as it approaches the injection plate 13 (hereinafter, this portion 120 may also be referred to as the "seat portion 120"). The nozzle plate 13 is provided with a plurality of nozzles 130 that penetrate the valve body 10 in the axial direction.

[0015] In the fuel injector 1 illustrated in Figure 1, when the tip of the needle 11 is seated on the seat portion 120 of the valve seat 12 (when the tip 110 is in contact with the seat portion 120), the flow of fuel from inside the valve body 10 to the injection hole 130 of the injection plate 13 is blocked. Also, in the fuel injector 1 illustrated in Figure 1, when the tip 110 of the needle 11 is separated from the seat portion 120 of the valve seat 12 (when the tip 110 is separated from the seat portion 120), the flow of fuel from inside the valve body 10 to the injection hole 130 of the injection plate 13 is permitted, and fuel is injected from the injection hole 130.

[0016] (Method for processing valve seats) Here, an example of a processing method in the manufacturing process of the valve seat 12 in this embodiment will be described. Figure 2 is a diagram illustrating an example of the valve seat processing method in this embodiment. Figure 2 shows a plan view of the valve seat 12 when shaping is being performed. In one example, shaping may be a process of applying polishing such as lapping or polishing to the valve seat 12 produced through processes such as molding and sintering. In the valve seat processing method in this embodiment, shaping is performed while three predetermined locations (parts P1-P3 shown as black circles in Figure 2) on the seat portion 120 of the valve seat 12 are heated. In other words, in the valve seat processing method in this embodiment, shaping of the valve seat 12 is performed while a temperature distribution is created in the seat portion 120 in which the temperature of the three predetermined locations P1-P3 is higher than that of other parts. In one example, the three predetermined locations P1-P3 may be three parts in the circumferential direction of the seat portion 120 in a plan view and correspond to the corners of a virtual equilateral triangle (Tr1 shown as a dashed line in Figure 2). Furthermore, the three designated locations P1-P3 may be heated from the bottom side of the valve seat 12, or from the side side of the valve seat 12.

[0017] (Operation and effects of this embodiment) When the valve seat 12 is shaped using the valve seat processing method in this embodiment, when the shaped valve seat 12 is left at room temperature, three predetermined locations P1-P3 on the seat portion 120 are cooled, causing these three locations P1-P3 to contract. As a result, the shape of the seat portion 120 in plan view becomes a roughly equilateral triangle with the three predetermined locations P1-P3 recessed, as illustrated in Figure 3. Note that in Figure 3, the amount of recession at the three predetermined locations P1-P3 is exaggerated for illustrative purposes, but the actual amount of recession is very small (for example, a few μm to several hundred μm). When the needle 11 is seated on such a valve seat 12, the seating position of the needle 11 is positioned by the parts of the seat portion 120 corresponding to the three sides of the roughly equilateral triangle. As a result, the center (axis) of the needle 11 and the center (axis) of the valve seat 12 come to approximately coincide.

[0018] Therefore, according to the valve seat processing method in the present embodiment, the deviation between the center of the needle 11 and the center of the valve seat 12 when the needle 11 seats on the valve seat 12 can be minimized. Thereby, the oil tightness between the needle 11 and the valve seat 12 can be enhanced without precisely increasing the roundness of the valve seat 12 in shape processing. That is, the oil tightness between the needle 11 and the valve seat 12 can be enhanced while suppressing an increase in the tact time in the shape processing of the valve seat 12 and an increase in the manufacturing cost of the fuel injection valve 1.

[0019] <Other Embodiments> In the above-described embodiment, an example of heating three predetermined locations P1 - P3 in the seat portion 120 of the valve seat 12 has been described. However, a temperature distribution may be generated in the seat portion 120 by cooling the three predetermined locations P1 - P3.

[0020] Also, in the above-described embodiment, an example of heating three predetermined locations P1 - P3 in the seat portion 120 of the valve seat 12 has been described. However, the number of portions heated during shape processing may be four or more, or two or less. However, the position and number of the portions heated (or cooled) during shape processing are limited to the position and number that can uniquely position the seating position of the needle at a desired position (a position where the center of the needle 11 coincides with the center of the valve seat 12).

Explanation of Reference Numerals

[0021] 1 ··· Fuel injection valve, 10 ··· Valve body, 11 ··· Needle, 110 ··· Tip portion, 12 ··· Valve seat, 120 ··· Seat portion, 13 ··· Nozzle plate, 13 0 ··· Nozzle hole

Claims

[Claim 1] A method for machining the valve seat of a fuel injection valve having a needle and a valve seat, When the valve seat is viewed from above, the valve seat is shaped by heating or cooling three or more locations in the circumferential direction, specifically the corners of a polygon, to different temperatures than the other locations. Valve seat machining method.

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