Butterfly valve seal ring

Abstract

To provide a seal ring for a butterfly valve which assumes an excellent planar shape irrespective of the shape of the seal ring.SOLUTION: A seal ring 1 is an injection molding composed of a resin composition for arrangement on an external periphery of a valve body of a butterfly valve and has an abutment port 5 in a portion in a peripheral direction. A groove 6 is formed in a side face 4, with an axial cross section of the seal ring 1 at a point where the groove 6 is formed being a substantially squared-U shape. When a position of the abutment port 5 is assumed to be 0° with respect to a circumferential center point O of the seal ring 1, a gate mark 7 is formed within in least either of a range exceeding 45°and equal to or smaller than 135° or a range exceeding 225°and equal to or smaller than 315°.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a seal ring for a butterfly valve used to seal gases such as exhaust gases in equipment that utilizes the gases. [Background technology]

[0002] In an internal combustion engine's exhaust gas recirculation (EGR) system, a seal ring is attached to the EGR valve, which controls the flow rate of exhaust gas. The EGR system is a device that returns a portion of the exhaust gas to the intake system, lowering the maximum temperature at which the mixture burns and thereby reducing the amount of NOx produced. The EGR valve is a butterfly valve that is rotatably mounted within the EGR flow path (housing), and the amount of recirculated exhaust gas is controlled by adjusting the opening of this valve. An annular groove is provided on the outer periphery of the roughly disc-shaped EGR valve (valve body), and a seal ring is attached to this annular groove.

[0003] A seal ring for such an EGR valve is known from Patent Document 1. This seal ring is made of resin, and a metal spring is arranged in an annular shape within the radial width of the seal ring. The spring is capable of pressing the seal ring radially outward and inward in response to pressure acting on the seal ring or deformation of the seal ring. The spring is housed in a groove formed in one axial end face of the seal ring, and the axial cross section of the seal ring at the location where the groove is formed is formed in a substantially U-shape.

[0004] Patent Document 2 discloses a resin seal ring in which the thickness of the ring is 7% to 11% of the outer diameter of the ring in a free state, and the inner diameter of the ring expanded by the pressure of the sealing fluid when the valve is open is smaller than the outer diameter of the valve. This seal ring has a larger thickness (radial dimension) than its width (axial dimension). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-39441 [Patent Document 2] Japanese Patent Application Publication No. 2019-168012 [Patent Document 3] Patent No. 2875773 Summary of the Invention [Problem to be solved by the invention]

[0006] Generally, resin seal rings for butterfly valves are manufactured by injection molding. During injection molding, it is a well-known technique to provide a gate at the center of the seal ring's overall length (see, for example, Patent Document 3), and this is a commonly used molding technique currently used to manufacture seal rings with good balance.

[0007] However, when a seal ring having a generally U-shaped cross section, such as that in Patent Document 1, is manufactured by placing a gate in the center of the seal ring's overall length in accordance with the conventional technology, the planar shape tends to deteriorate. Generally, when the planar shape of the seal ring deteriorates, air leaks (gas leaks) increase, and the function of the butterfly valve may deteriorate.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a seal ring for a butterfly valve that has an excellent planar shape regardless of the shape of the seal ring. [Means for solving the problem]

[0009] The seal ring of a butterfly valve of the present invention is a seal ring provided on the outer periphery of a valve body of a butterfly valve, the seal ring being an injection-molded article of a resin composition having a joint in a part of its circumferential direction, and characterized in that, when the position of the joint is defined as 0° with respect to the circumferential center point of the seal ring, a gate mark is formed in at least one of a range of more than 45° and less than 135°, or more than 225° and less than 315°.

[0010] The seal ring is characterized in that a recess is formed on one axial end face, and the axial cross section of the seal ring at the location where the recess is formed is approximately U-shaped.

[0011] The gate mark is formed on the inner peripheral surface, and is formed at a position that does not overlap with the recess in the radial direction in an axial cross section of the seal ring.

[0012] The ratio of the width direction length (axial dimension) of the seal ring to the thickness direction length (radial dimension) of the seal ring is 1:1.5 to 1:2.5.

[0013] The resin composition is characterized in that it uses polyether ether ketone (PEEK) resin, polyamide imide (PAI) resin, or polyphenylene sulfide (PPS) resin as a base resin. [Effects of the Invention]

[0014] The seal ring of the butterfly valve of the present invention is an injection-molded article of a resin composition having a circumferential joint, and when the position of the joint is defined as 0° relative to the circumferential center point of the seal ring, the gate mark is formed in at least one of the ranges of more than 45° and less than 135°, or more than 225° and less than 315°, so that, as will be shown in the examples described later, the flatness is superior to cases where the gate mark is formed at a location outside the above ranges. This results in a seal ring with excellent flatness regardless of the shape of the seal ring, and as a result, air leakage can be reduced.

[0015] The above seal ring has a recess formed in one axial end face, and even if the axial cross section of the seal ring at the recessed portion is substantially U-shaped, the seal ring has excellent flatness. [Brief explanation of the drawings]

[0016] [Figure 1]1 is a plan view showing an example of a seal ring of the present invention. FIG. [Figure 2] 2 is a cross-sectional view of the seal ring of FIG. 1 taken along line AA. [Figure 3] FIG. 10 is an enlarged view of the gap of the composite step cut. [Figure 4] FIG. 2 is a diagram showing the state of the seal ring of FIG. 1 when the valve is closed. [Figure 5] FIG. 10 is a diagram showing the positions of gate marks on the seal rings of the example and the comparative example. [Figure 6] FIG. 10 is a diagram showing the measurement results of flatness in an example and a comparative example. [Figure 7] 10 is a plan view and a partially enlarged view of Comparative Example 3. FIG. [Figure 8] FIG. 10 is a diagram showing the measurement results of the planar shape of Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0017] The seal ring of the present invention is used in a control valve using a butterfly valve, and is a sealing member that is fitted into an annular groove provided on the outer periphery of a substantially disk-shaped butterfly valve to seal the gap between the valve and the housing in which the valve is accommodated. The control valve opens and closes when the substantially disk-shaped butterfly valve rotates within the housing around a valve stem. An example of this type of control valve is a control valve for an exhaust gas recirculation (EGR) system of an internal combustion engine (also simply referred to as an "EGR control valve").

[0018] An example of the seal ring of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view of the seal ring, and FIG. 2 is a cross-sectional view taken along line AA thereof. In FIG. 1, the seal ring 1 is an injection-molded article made of a resin composition. The axial cross section of the seal ring 1 is substantially rectangular, surrounded by one side surface 4 (one axial end surface), the other side surface 4' (the other axial end surface), an outer peripheral surface 2, and an inner peripheral surface 3. Although not shown, the corners between the inner peripheral surface 3 and the side surfaces 4, 4' may be chamfered in a linear or curved manner, or may have a step that protrudes from the mold when the seal ring is injection molded. The chamfer or step may extend to the pair of ends that form the joint.

[0019] The seal ring 1 is a cut-type ring having a joint 5 in part of its circumferential direction. The joint 5 is open in the molded body after injection molding, and is then closed by heat setting as shown in Figure 1. The shape of the joint 5 can be a straight cut shape, an angle cut shape, or the like, but it is preferable to adopt a compound step cut shape as shown in Figure 3 because this provides excellent sealing properties for the sealed fluid.

[0020] In FIG. 1, a groove 6 is formed on one side surface 4 of the seal ring 1 as a recess recessed in the axial direction. The groove 6 is formed along the circumferential direction over substantially the entire circumference of the side surface 4, excluding the joint 5. The groove 6 does not open to the inner peripheral surface 3 or the outer peripheral surface 2, but is a closed recessed groove within the side surface. Also, in FIG. 1, the groove 6 is formed with a substantially constant groove width and groove depth. An elastic member such as a metal spring is housed in this groove 6 (see FIG. 4). In this case, by using an elastic member with an elastic constant higher than that of the seal ring, it is possible to apply a radial expansion force to the seal ring and improve sealing performance. Examples of materials that can be used for the elastic member include metals, resin compositions, and organic-inorganic composite materials.

[0021] In FIG. 1, no recess is formed on the other side surface 4' of the seal ring 1, and the side surface 4' is a flat surface.

[0022] Figure 2 shows an axial cross section of the seal ring at a location where a groove is formed. The axial cross section of the seal ring 1 shown in Figure 2 is approximately U-shaped. In Figure 2, the groove 6 has an approximately rectangular cross section and is composed of a bottom surface 6a and side wall surfaces 6b, 6b standing upright from the bottom surface 6a. Note that in the approximately U-shaped form of the seal ring, the cross section of the groove is not limited to an approximately rectangular shape, and an approximately triangular shape, an arc shape, or the like can also be used.

[0023] The dimensions of the seal ring 1 will be described with reference to FIG. 2. As shown in FIG. 2, the width W (axial dimension) of the seal ring 1 is the distance from one side surface 4 to the other side surface 4' in the axial direction. The thickness T (radial dimension) of the seal ring 1 is the distance from the outer peripheral surface 2 to the inner peripheral surface 3. The relationship between the width and thickness of the seal ring is not particularly limited. However, to prevent the seal ring from expanding in diameter and falling off the annular groove during valve use, it is preferable for the thickness to be greater than the width (width W < thickness T). Specifically, the ratio of the width to thickness of the seal ring is preferably 1:1.2 to 1:3.0, and more preferably 1:1.5 to 1:2.5. According to the present invention, even if the ratio of the width to thickness of the seal ring is within the above-mentioned range, the flatness of the seal ring can be maintained satisfactorily. The width W of the seal ring is not particularly limited, but is preferably set to 1.5 mm to 2.5 mm.

[0024] The depth d of the groove 6 from the side surface 4 is preferably 20% to 70% of the width W of the seal ring, and more preferably 30% to 60%. By keeping the depth within this range, deformation of the seal ring during use can be easily suppressed, and the elastic member can be easily accommodated in the groove. Note that if the depth of the recess varies, the "depth" mentioned above refers to the depth of the deepest part.

[0025] As shown in Fig. 2, the groove 6 is formed near the inner periphery on the side surface 4. Near the inner periphery means that the radial center position of the groove 6 is located closer to the inner periphery than the radial center position of the side surface 4. In this case, the thickness of the seal ring on the inner periphery side, with the groove 6 as the boundary, is smaller than the thickness of the seal ring on the outer periphery side.

[0026] Here, when recesses such as those shown in Figures 1 and 2 are formed on the axial end surface of a seal ring, the fluidity of the molten resin during injection molding is reduced compared to when no recesses are formed, and this may result in insufficient filling of the cavity. In fact, it has been found that when a seal ring having a recess is manufactured by injection molding, positioning the gate at the center of the seal ring's entire length results in a problem of poor flatness. Furthermore, when a seal ring is molded with poor flatness due to a gate being positioned at the center, the flatness does not improve even after heat setting. Therefore, the present inventors have discovered that the problem of poor flatness can be resolved by positioning the gate at a predetermined position.

[0027] As shown in Fig. 1, when the position of the gap relative to the circumferential center point O is taken as 0°, the seal ring of the present invention has gate marks 7 formed in the ranges of more than 45° and less than 135° and more than 225° and less than 315°. In Fig. 1, when the position of the gap relative to the circumferential center point O of the seal ring 1 is taken as 0°, the gate marks 7 are formed at a position of 270°. Note that the above angles represent clockwise angles with the anti-seal surface of the seal ring (the side surface on which the groove is formed in Fig. 1) as the reference, with the position of the gap at that time taken as 0°.

[0028] In the seal ring 1, if the gate marks are formed in the range of 0° to 45° or 315° to 360°, the flow length to the gap on the side without the gate marks becomes longer, making it difficult to fill the cavity. Furthermore, sink marks and burrs are more likely to occur around the gap on the side with the gate marks. On the other hand, if the gate marks are formed in the range of 135° to 225°, flatness tends to deteriorate, as shown in the examples described later.

[0029] As shown in Figure 1, it is preferable that only one gate mark 7 is formed in the seal ring 1 within the above range. In this case, the gate is a pin gate, and a single-point gate is used. If a multi-point gate is used, a weld will be formed where the molten resin meets. Since the weld has low mechanical strength, it is preferable to use a single-point gate that does not cause a weld.

[0030] The range in which the gate marks 7 are formed is preferably 65° to 115° (90°±25°) and 245° to 295° (270°±25°), with the joint position being taken as 0°, and more preferably 80° to 100° (90°±10°) and 260° to 280° (270°±10°). By forming the gate marks 7 in the ranges near 90° and 270°, it becomes easier to maintain good flatness while maintaining a certain degree of balance in the flow lengths in the two directions.

[0031] 1, the groove 6 is formed in at least a region of 45° to 315° on the side surface 4 when the position of the gap is taken as 0°. The gate mark 7 is formed on the inner circumferential surface 3, and the gate mark 7 is formed at a position that overlaps with the groove 6 in the radial direction in the plan view of FIG. 1. As shown in the axial cross section of FIG. 2, the gate mark 7 is formed at a position in the axial direction of the inner circumferential surface 3 closer to the side surface 4' where no groove 6 is present, and is formed so as not to overlap the depth region of the groove 6 in the radial direction where the gate mark 7 is present. In this case, in the axial cross section of the seal ring 1, the gate mark 7 is formed at a position that does not overlap with the groove 6 in the radial direction. Note that not overlapping in the radial direction means that the groove 6 does not exist on the radial extension of the gate mark 7 in FIG. 2.

[0032] FIG. 3 shows an enlarged view of the joint of the composite step cut. FIG. 3(a) shows the state of the molded body after injection molding, with the joint open. The joint 5 is composed of a pair of complementary interlocking end portions 8 and 9. One end portion 8 has a butt portion 8a on the inner circumferential surface side and a lip portion 8b protruding from the butt portion 8a and a recessed pocket portion 8c on the outer circumferential surface side. The other end portion 9 has a butt portion 8a, a lip portion 8b, and a pocket portion 8c, and a butt portion 9a, a pocket portion 9c, and a lip portion 9b formed to complementarily interlock with the butt portion 8a, lip portion 8b, and pocket portion 8c. This open state of the joint 5 is referred to as a closed state by heat setting (FIG. 3(b)). In the present invention, the position of the joint that serves as the reference for 0° is the center of the closed joint, that is, the center position between the butt portions 8a and 9a.

[0033] The shape of the seal ring of the present invention is not limited to the shapes shown in Figures 1 to 3. The shape of the recess is not limited to the groove shape described above and can be changed as appropriate. The present invention is also applicable to seal rings in which recesses are not formed on both axial end faces.

[0034] The seal ring of the present invention is an injection-molded article made of a resin composition based on a synthetic resin. Examples of synthetic resins that can be used include thermoplastic polyimide resins, polyetherketoneetherketoneketone (PEKEKK) resins, polyetherketone (PEK) resins, PEEK resins, wholly aromatic polyester resins, PPS resins, PAI resins, and polyamide (PA) resins. These resins may be used alone or in combination to form a polymer alloy. Among these, PEEK resins, PAI resins, and PPS resins are preferred because of their excellent abrasion resistance, sealing properties, heat resistance, durability, and flexural modulus.

[0035] If necessary, the synthetic resin can be blended with fibrous reinforcing materials such as carbon fiber, glass fiber, and aramid fiber; spherical fillers such as spherical silica and spherical carbon; scale-like reinforcing materials such as mica and talc; and microfiber reinforcing materials such as potassium titanate whiskers. Solid lubricants such as polytetrafluoroethylene (PTFE) resin, graphite, and molybdenum disulfide; sliding reinforcing materials such as calcium phosphate and calcium sulfate; and carbon black can also be blended. These can be blended alone or in combination. In particular, PEEK resin, PAI resin, or PPS resin containing carbon fiber as a fibrous reinforcing material and PTFE resin as a solid lubricant is preferred, as it easily achieves the properties required for the seal ring of the present invention. The inclusion of carbon fiber improves mechanical strength, such as flexural modulus, while the inclusion of PTFE resin improves sliding properties.

[0036] The above raw materials are melted and kneaded to obtain molding pellets. Using these, a gate (e.g., a single-point pin gate) is placed at a predetermined position in the molding cavity corresponding to the shape of the seal ring, and molten resin is injected through the gate. At this time, the gate is positioned so that a gate mark is formed at the above-mentioned position on the seal ring. This allows the molten resin to be distributed uniformly throughout the molding cavity, improving the flatness of the molded body after injection molding. After injection molding, the gaps of the molded body are closed by heat setting to obtain a seal ring 1 as shown in Figure 1.

[0037] FIG. 4 shows an EGR valve fitted with a seal ring of the present invention. FIG. 4 shows the state when the valve is closed. Seal ring 1 is expanded in diameter by elastic deformation using a jig and fitted into annular groove 12 of butterfly valve 11. In FIG. 4, seal ring 1 is fitted into annular groove 12 provided on the outer periphery of approximately disc-shaped butterfly valve 11, and seals annular gap 14 between butterfly valve 11 and housing 13. Butterfly valve 11 is rotatably accommodated inside housing 13 and supported by a shaft (not shown) that serves as a valve stem. Rotating butterfly valve 11 inside housing 13 opens and closes the valve.

[0038] In FIG. 4, the pressure of the EGR gas, which is the sealing gas, acts on the side surface 4 of the seal ring 1, pressing the side surface 4' against one side wall surface of the annular groove 12. This pressure, the tension in the radial expansion direction of the seal ring, and the spring force of the elastic member 15 housed in the groove press the outer peripheral surface 2 against the inner wall of the housing 13, ensuring sealing. Furthermore, by housing the elastic member 15, sealing can be ensured even if the tension of the seal ring is reduced due to, for example, high-temperature creep. Note that the side surface 4' of the seal ring 1 opposite the side surface 4 where the groove 6 is provided becomes the sealing surface. [Example]

[0039] Example 1, Comparative Examples 1 to 3 Seal rings (outer diameter φ40 mm x width 1.8 mm x thickness 3.6 mm) were manufactured by injection molding, with 20 of each test example being manufactured with different gate positions. The seal ring materials and gate designs are shown below. The positions of the gate marks on the seal rings of each test example are as shown in Figure 5. These seal rings have a groove formed on one side surface into which an elastic member is attached, and the axial cross section of the seal ring at the location where the groove is formed is approximately U-shaped. A step is also provided at the corner between the inner peripheral surface and the side surface. Material: PEEK (Bearee PK5301) Gate: φ0.9mm, 1-point pin gate Joint: Compound step cut

[0040] The flatness of the seal ring obtained above was measured (n=20 for each test example). In measuring the flatness, first, the seal ring was placed on a flat test table with the side on which the groove was formed facing downward, and a 100g glass plate was placed on the other side. Then, using a three-dimensional measuring machine (Keyence One Shot 3D VR-5200), the difference between the minimum height and the maximum height over the entire circumference of the other side (seal surface) was measured as the flatness.

[0041] The measurement results are shown in Figure 6, which shows the relationship between gate position and flatness. The smaller the flatness value on the vertical axis, the better the flatness. Figure 6 shows the results for the side surface opposite the groove where the elastic member is attached (the anti-groove side). As shown in Figure 6, Example 1 and Comparative Example 3 had better flatness than Comparative Examples 1 and 2, and the variation was smaller. Comparative Examples 1 and 2 had poor flatness, which is thought to result in greater air leakage. Furthermore, when comparing the seal rings, there was a tendency for flatness to improve the closer the gate position was to the gap.

[0042] Next, the appearance of the seal ring of each test example was observed. As a result, no sink marks or burrs were observed in Example 1 and Comparative Examples 1 and 2. On the other hand, although good flatness results were obtained in Comparative Example 3 (see FIG. 6), sink marks and burrs were observed. A plan view of the seal ring of Comparative Example 3 and the results of shape measurement are shown in FIGS. 7 and 8.

[0043] Figure 7(a) is a plan view of Comparative Example 3 before the gap is closed, and Figure 7(b) is an enlarged view of part B. As shown in Figure 7(b), a burr occurred on the outer peripheral surface of the lip at the end where the gate mark was formed. The height of this burr was 0.466 mm. Meanwhile, a sink mark was observed at the end where the gate mark was not formed. Figure 8 shows the results of measuring the planar shape along line CC in Figure 7(b). As shown in Figure 8, a sink mark of approximately 0.06 mm was confirmed on the side of the end where the gate mark was not formed. It is believed that Comparative Example 3, which has a sink mark, has a gap with the annular groove of the butterfly valve, which increases the air leak.

[0044] As described above, when the position of the joint relative to the circumferential center point of the seal ring is defined as 0°, the seal ring of Example 1, which has gate marks in the ranges of more than 45° but less than 135° and more than 225° but less than 315°, has excellent flatness and can suppress the occurrence of sink marks and burrs. In this way, by positioning the gate, which is the injection port for molten resin, at a predetermined position, it is possible to suppress deformation after injection molding, prevent deterioration of flatness, and suppress an increase in air leakage. [Industrial Applicability]

[0045] The seal ring for a butterfly valve of the present invention has an excellent planar shape regardless of the shape of the seal ring, and therefore can be widely used as a seal ring to be fitted into the annular groove of a butterfly valve, and is particularly suitable as a seal ring for an EGR valve. [Explanation of symbols]

[0046] 1 Seal ring (butterfly valve seal ring) 2 Outer surface 3 Inner surface 4, 4' side 5. Joint 6 Groove (recess) 7 Gate Remains 8 End 9 End 11 Butterfly valve 12 Annular groove 13. Housing 14 Annular gap 15 Elastic member

Claims

1. A seal ring provided on the outer periphery of a valve body of a butterfly valve, the seal ring is an injection-molded article of a resin composition having a joint in a part of a circumferential direction, a recess formed in one end face in an axial direction, and an axial cross section of the seal ring at the location where the recess is formed is substantially U-shaped, A seal ring for a butterfly valve, characterized in that, when the position of the gap is defined as 0° with respect to the circumferential center point of the seal ring, a gate mark is formed in at least one of a range of 90°±10° or 270°±10°.

2. 2. The seal ring for a butterfly valve according to claim 1, wherein the gate mark is formed on the inner peripheral surface and is formed at a position that does not overlap with the recess in the radial direction in an axial cross section of the seal ring.

3. A seal ring provided on the outer periphery of a valve body of a butterfly valve, the seal ring is an injection-molded article of a resin composition having a joint in a part of a circumferential direction, a recess formed in one end face in an axial direction, and an axial cross section of the seal ring at the location where the recess is formed is substantially U-shaped, When the position of the gap is defined as 0° with respect to the circumferential center point of the seal ring, a gate mark is formed in at least one of a range of more than 45° and less than 135° or a range of more than 225° and less than 315°, 1. A seal ring for a butterfly valve, wherein the gate mark is formed on an inner peripheral surface, and the gate mark is formed at a position that does not overlap with the recess in the radial direction in an axial cross section of the seal ring.

4. 4. The seal ring for a butterfly valve according to claim 1, wherein a ratio of an axial dimension of the seal ring to a radial dimension of the seal ring is 1:1.5 to 1:2.

5.

5. 5. The seal ring for a butterfly valve according to claim 1, wherein the resin composition has a base resin selected from the group consisting of polyether ether ketone resin, polyamide imide resin, and polyphenylene sulfide resin.

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