Machining method for fuel injection valve devices of internal combustion engines

Abstract

The present invention provides a method for manufacturing a fuel injection valve device for an internal combustion engine that can be easily produced and can suppress fuel leakage from the injection port when the valve body is in the closed position. [Solution] The method for machining the fuel injection valve device 11 of an internal combustion engine comprises a cylindrical body 12 having an injection port 16 through which fuel is injected, a valve seat 17 provided on the body 12 so as to surround the injection port 16, and a valve body 13 disposed inside the body 12 and configured to move along the axis L of the body 12 between a closed position in which it contacts the valve seat 17 and closes the injection port 16, and an open position away from the valve seat 17 and opens the injection port 16. Grinding is performed on the portion of the valve seat 17 that the valve body 13 contacts, with a low-rigidity portion 19 provided on the valve seat 17 that is partially less rigid than other parts in the circumferential direction.

Description

Technical Field

[0001] The present invention relates to a method for processing a fuel injection valve device for an internal combustion engine.

Background Art

[0002] Conventionally, as a fuel injection valve device for an internal combustion engine, for example, a valve device described in Patent Document 1 is known. Such a valve device uses the interior of a cylindrical valve body as a flow path, and has a valve portion in which a tapered valve body seat surface provided at the tip of a valve body that slides inside the valve body abuts against a tapered seat surface provided at an end of the valve body to close the flow path. The tip of the valve body in the valve portion is provided with an elastically deformable portion that elastically deforms so that the gap between the seat surface of the valve body and the valve body seat surface of the valve body is reduced when the valve portion is seated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] Incidentally, in the above-described valve device, an elastically deformable portion is provided at the tip of the valve body in the valve portion so as to suppress fuel leakage from the valve portion when the valve is closed. However, the elastically deformable portion is constituted by a flange portion formed by notching the entire circumference of the outer peripheral surface of the valve body to a constant depth to form a fine annular groove. For this reason, the above-described valve device has a problem that the shape of the valve body is complicated, so that it cannot be easily manufactured.

Means for Solving the Problems

[0005] A method for machining a fuel injection valve device for an internal combustion engine that solves the above problems comprises a cylindrical body having an injection port through which fuel is injected, a valve seat provided on the body so as to surround the injection port, and a valve body disposed inside the body and configured to move along the axis of the body between a closed position in which it contacts the valve seat and closes the injection port, and an open position away from the valve seat and opens the injection port, wherein grinding is performed on the portion of the valve seat that the valve body contacts, while a low-rigidity portion is provided on the valve seat in the circumferential direction that is partially less rigid than other parts.

[0006] According to the above method, by grinding the portion of the valve seat that contacts the valve body while a low-rigidity portion is provided on the valve seat, the protrusion height of the portion corresponding to the low-rigidity portion of the valve seat that contacts the valve body becomes higher than that of other portions due to springback after grinding. As a result, the portion of the valve seat that seals with the valve body becomes polygonal when viewed from the axial direction of the main body. Therefore, the required roundness of the portion of the valve seat that seals with the valve body can be relaxed, and eccentricity of the valve body when the valve body is in the closed position can be suppressed. Thus, fuel injection valve devices for internal combustion engines can be easily manufactured, and fuel leakage from the injection port when the valve body is in the closed position can be suppressed. [Effects of the Invention]

[0007] The above-described method for manufacturing fuel injection valve devices for internal combustion engines allows for easy production of fuel injection valve devices for internal combustion engines and suppresses fuel leakage from the injection port when the valve body is in the closed position. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1(a) is a half-cross-sectional view showing the main parts of a fuel injection valve device of an internal combustion engine according to one embodiment, and Figure 1(b) is a bottom view of Figure 1(a). [Figure 2] Figure 2 is a graph showing the relationship between the circumferential position on the valve seat, the rigidity of the valve seat, and the protrusion height of the tapered surface. [Figure 3]Figure 3 is a schematic plan view showing the shape of the seal portion. [Modes for carrying out the invention]

[0009] One embodiment will be described below with reference to the drawings. <Fuel injection valve device 11> As shown in Figure 1(a), the fuel injection valve device 11 of the internal combustion engine comprises a cylindrical body 12 and a substantially cylindrical valve body 13 located inside the body 12.

[0010] <Main body 12> As shown in Figure 1(a), the inside of the main body 12 constitutes a passage 14 through which fuel flows. A circular injection port 16 through which fuel is injected is formed in the center of the bottom wall 15 of the main body 12. The main body 12 has an axis L. The axis L passes through the center of the injection port 16. The portion of the bottom wall 15 surrounding the injection port 16 constitutes a valve seat 17.

[0011] In other words, the valve seat 17 is provided on the main body 12 so as to surround the injection port 16. An annular tapered surface 18 is formed on the inner surface of the valve seat 17, which is inclined so that it approaches the injection port 16 as it approaches the axis L. The fuel injection valve device 11 is configured such that the injection port 16 is closed when the valve body 13 comes into contact with the tapered surface 18.

[0012] As shown in Figures 1(a) and 1(b), the outer surface of the valve seat 17 is provided with low-rigidity portions 19 that are partially less rigid than other parts in the circumferential direction. The low-rigidity portions 19 are formed by thinning the surface through the formation of recesses. In this example, three low-rigidity portions 19 are provided on the outer surface of the valve seat 17 at approximately equal intervals in the circumferential direction.

[0013] As shown in Figures 1(b) and 2, the portion of the tapered surface 18 corresponding to the low-rigidity portion 19 in the circumferential direction is a protruding portion 20 with a greater protruding height than the portion of the tapered surface 18 that does not correspond to the low-rigidity portion 19 in the circumferential direction. The clockwise angle from 0° to 360° from the 0° position in Figure 1(b) corresponds to the horizontal axis angle from 0° to 360° in the graph in Figure 2.

[0014] The graph in Figure 2 shows that the portion of the tapered surface 18 corresponding to the low-rigidity portion 19 has a higher protrusion height than the portion of the tapered surface 18 that does not correspond to the low-rigidity portion 19. Curve A, shown by the dashed line in Figure 2, represents the protrusion height of the tapered surface 18. Curve B, shown by the solid line in Figure 2, represents the rigidity of the valve seat 17.

[0015] <Valve body 13> As shown in Figure 1(a), the valve body 13 is located inside the main body 12. The valve body 13 is substantially cylindrical in shape and extends along the axis L. The tip surface 21 of the valve body 13 is formed by a circular plane facing the injection nozzle 16. Around the tip surface 21 of the valve body 13, an annular sealing surface 22 is formed when viewed from the direction in which the axis L extends. The sealing surface 22 has an arc shape in cross-sectional view.

[0016] The valve body 13 is configured to move along axis L between a closed position (shown in Figure 1(a)) where the sealing surface 22 contacts the tapered surface 18 of the valve seat 17 and closes the injection port 16, and an open position where the sealing surface 22 separates from the tapered surface 18 of the valve seat 17 and opens the injection port 16. That is, the valve body 13 is configured to move along axis L between the closed position and the open position by a moving mechanism (not shown). When the valve body 13 is in the closed position, fuel is not injected from the injection port 16. When the valve body 13 is in the open position, fuel is injected from the injection port 16.

[0017] As shown in Figure 1(a), Figure 2 and Figure 3, when the valve element 13 is in the closed position, the portion that forms a seal with the sealing surface 22 of the valve element 13 on the tapered surface 18 of the valve seat 17 is defined as a seal portion 23. The seal portion 23 has a polygonal shape (the shape shown by the solid line in Figure 3) when viewed in the direction in which the axis L extends (the axial direction of the main body 12) due to the action of the protruding portion 20 on the tapered surface 18. The angles of 0° to 360° in the clockwise direction from the 0° position in Figure 3 respectively correspond to the angles of 0° to 360° in the clockwise direction from the 0° position in Figure 1(b) and the angles of 0° to 360° in the graph of Figure 2.

[0018] <Method for Processing Valve Seat 17> As shown in Figure 1(a) and Figure 1(b), the tapered surface 18 of the valve seat 17 is ground in a state where low-rigidity portions 19 having partially lower rigidity than other portions in the circumferential direction are provided on the outer surface of the valve seat 17. Thereby, in the portion corresponding to the low-rigidity portion 19 in the circumferential direction of the tapered surface 18, a protruding portion 20 (see Figure 2) having a higher protruding height than the portion not corresponding to the low-rigidity portion 19 in the circumferential direction of the tapered surface 18 is formed due to springback after grinding.

[0019] Therefore, as shown in Figure 3, the shape of the seal portion 23 during grinding of the tapered surface 18 is a circular shape as indicated by the two-dot chain line, but the shape of the seal portion 23 after grinding of the tapered surface 18 becomes a polygonal shape as indicated by the solid line due to the action of the protruding portion 20.

[0020] <Operations and Effects of the Present Embodiment> The amount of fuel leaking from the injection port 16 when the valve element 13 is in the closed position is considered to be the flow rate of the viscous fluid fuel (gasoline) through the gap between the valve element 13 and the tapered surface 18 of the valve seat 17 caused by poor roundness, driven by fuel pressure. Assuming that the fuel leakage flow rate Q can be approximated by plane Poiseuille flow, the fuel leakage flow rate Q can be expressed by the following (Equation 1).

[0021] Q=1 / 12ρv×dp / dx×h 3 ···(Equation 1) In equation (1), ρ is the fuel density, v is the viscosity, dp / dx is the pressure gradient, and h is the gap. Therefore, from equation (1), the fuel leakage flow rate Q is proportional to the cube of the gap h (roundness).

[0022] As a comparative example, if the shape of the seal portion is an elongated hole, the valve body 13 is more likely to move in the longitudinal direction of the seal portion, and therefore is more likely to be eccentric from the position of the largest inscribed circle of the seal portion. When the valve body 13 is at the position of the largest inscribed circle of the seal portion, gaps h are created at two locations at both ends in the longitudinal direction of the seal portion.

[0023] Then, when the valve body 13 is eccentrically positioned from the position of the largest inscribed circle of the seal portion to one end in the longitudinal direction of the seal portion, the number of gaps h formed decreases from two to one, but the size of the gap h doubles. Therefore, the fuel leakage flow rate Q is 1 / 2 (the decrease in the number of gaps h) × 2 3 The gap widens to four times its original size.

[0024] On the other hand, in this embodiment, since the shape of the seal portion 23 is polygonal, the valve body 13 is hardly eccentric from the position of the largest inscribed circle of the seal portion 23. Therefore, in this embodiment, unlike in the comparative example described above, the two gaps h are not combined, so the fuel leakage flow rate Q does not increase fourfold.

[0025] Thus, in the fuel injection valve device 11 of this embodiment, by grinding the tapered surface 18 with the low-rigidity portion 19 provided on the valve seat 17, a protrusion 20 is formed on the tapered surface 18 in the portion corresponding to the low-rigidity portion 19 due to springback after grinding. As a result, the shape of the seal portion 23 becomes polygonal when viewed from the axial direction of the main body 12. Therefore, the required roundness of the seal portion 23 can be relaxed, and the eccentricity of the valve body 13 when the valve body 13 is in the closed position can be suppressed. Thus, the fuel injection valve device 11 for an internal combustion engine can be easily manufactured, and fuel leakage from the injection port 16 when the valve body 13 is in the closed position can be suppressed.

[0026] <Example of changes> The above embodiment can be implemented with the following modifications. Furthermore, the above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0027] The number of low-rigidity portions 19 formed on the outer surface of the valve seat 17 may be one. A low-rigidity portion 19 may be formed on the inner surface of the valve seat 17. [Explanation of Symbols]

[0028] 11…Fuel injection valve system 12…Main unit 13… Valve body 14…Flow channel 15...Bottom wall 16...Injection port 17... Valve seat 18... Tapered surface 19...Low rigidity part 20...Protrusion 21…Tip surface 22...Sealing surface 23... Seal part A,B…Curve L…Axis line

Claims

[Claim 1] A cylindrical body having an injection nozzle from which fuel is injected, A valve seat is provided on the main body so as to surround the injection nozzle, A valve body is disposed within the main body and is configured to be movable along the axis of the main body between a closed position in which it contacts the valve seat and closes the injection port and an open position in which it is separated from the valve seat and opens the injection port. A method for processing a fuel injection valve device for an internal combustion engine, comprising: A method for machining a fuel injection valve device for an internal combustion engine, characterized in that a low-rigidity portion is provided on the valve seat in a circumferential direction, where the rigidity of the valve body is partially lower than that of other portions, and the portion of the valve seat that contacts the valve seat is then ground.

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