JP2011226470A - Oil seal member and method for producing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance responsiveness of a variable valve timing mechanism; to enhance wear resistance of an oil seal member; to prevent damage of a powder compact; and to enhance dimension accuracy of the oil seal member.SOLUTION: An oil seal member 20 is formed by molding a bottom surface 31 of the powder compact 30 into a flat surface in a powder compacting process, and molding a flat bottom surface 41 of a sintered compact 40 into a curved surface in a sizing process, the sintered compact 40 being obtained by sintering the powder compact. Namely, a bottom surface 21 of the oil seal member 20 is molded into a curved surface by sizing.

Description

  The present invention relates to an oil seal member provided between a plurality of hydraulic chambers formed by a rotor and a housing of a variable valve timing mechanism and partitioning each hydraulic chamber in a liquid-tight manner, and in particular, formed of sintered metal. The present invention relates to an oil seal member.

  The variable valve timing mechanism is attached to a camshaft of an engine and makes the intake / exhaust valve open / close timing variable (see, for example, Patent Document 1). For example, a variable valve timing mechanism 100 shown in FIG. 11 rotates in synchronization with a camshaft S and a rotor 104 that accommodates the rotor 103 in a relatively rotatable manner. With.

  As shown in FIG. 11A, the rotor 103 includes a plurality (four in the illustrated example) of vanes 105 protruding to the outer peripheral side. The housing 104 has a plurality (four in the illustrated example) of teeth 106 protruding between the circumferential directions of the plurality of vanes 105. Hydraulic chambers 107 and 108 are formed between the vane 105 and the teeth 106. The hydraulic chamber 107 on one side in the circumferential direction of the vane 105 forms an advance chamber to which hydraulic pressure is supplied when the rotor 103 is driven to the advance side. The hydraulic chamber 108 on the other circumferential side of the vane 105 forms a retard chamber to which hydraulic pressure is supplied when the rotor 103 is driven to the retard side.

  The hydraulic chambers 107 and 108 are liquid-tightly partitioned by oil seal members 120 and 130. As shown in FIG. 11A, the oil seal member 120 provided on the vane 105 is fitted into a groove portion 105 a formed on the front end surface of the vane 105 and slides with the inner peripheral surface of the housing 104. As shown in FIG. 11B, a plate spring 109 is provided between the oil seal member 120 and the groove bottom surface of the groove portion 105 a, and the plate spring 109 causes the bottom surface 121 of the oil seal member 120 to move to the inner periphery of the housing 104. Pressed against the surface. The bottom surface 121 of the oil seal member 120 has a shape along the inner peripheral surface of the housing 104. Specifically, as shown in FIG. Formed in a planar shape. As shown in FIG. 12B, the top surface 122 of the oil seal member 120 has a pair of convex portions 122a and 122a at both ends in the long side direction, and the leaf spring 109 is curved between the convex portions 122a and 122a. (See FIG. 11B). In FIG. 12C, for easy understanding, the curvature of the bottom surface 121 is exaggerated (shown smaller than the actual radius of curvature).

  As shown in FIG. 11A, the oil seal member 130 provided on the tooth 106 is fitted in a groove portion 106 a formed on the front end surface of the tooth 106 and slides on the outer peripheral surface of the rotor 103. As shown in FIG. 11C, a leaf spring 110 is disposed between the oil seal member 130 and the groove bottom surface of the groove portion 106 a, and the bottom surface 131 of the oil seal member 130 is arranged on the outer peripheral surface of the rotor 103 by the plate spring 110. Pressed against. The shape of the oil seal member 130 is the same as that of the oil seal member 120 shown in FIG.

  If the oil seal members 120 and 130 as described above are formed of a sintered metal having excellent moldability, the dimensional accuracy (particularly the dimensional accuracy of the bottom surface) can be increased as compared with the case where the oil seal members 120 and 130 are formed of resin. As a result, the contact state with the housing 104 or the rotor 103 is improved, and the sealing performance of the hydraulic chambers 107 and 108 is improved. Therefore, the time until the rotor 103 rotates after the hydraulic pressure is supplied to the hydraulic chamber 107 or 108 is increased. This shortens the responsiveness of the variable valve timing mechanism.

JP 2009-297812 A JP 2007-262451 A JP 2007-246939 A

  However, when the oil seal member is made of sintered metal, numerous surface openings are formed in the oil seal member. If the oil in the hydraulic chamber falls out of the oil seal member through the surface opening, the hydraulic pressure in the hydraulic chamber is difficult to increase, and the responsiveness of the variable valve timing mechanism may be reduced. Further, if oil between the inner peripheral surface of the housing that slides relative to each other (or the outer peripheral surface of the rotor) and the bottom surface of the oil seal member escapes into the oil seal member, an oil film is hardly formed on the sliding portion. There is a risk that the lubricity of the sliding portion is lowered and the wear resistance of each member is lowered.

  Further, when the oil seal member is formed of sintered metal, the following problems may occur. In the following description, an oil seal member (see FIG. 12) having a convex curved bottom surface will be described. However, since an oil seal member (see FIG. 9) having a concave curved bottom surface is the same, duplicated description will be given. Is omitted.

  The oil seal member made of sintered metal is formed by compression molding metal powder to form a green compact, and then sintering the green compact at a predetermined temperature. In the compression molding step, as shown in FIG. 13 (a), the metal powder M ′ is filled in the cavity formed by the die 141 and the lower punch 142, and then the upper punch 143 is moved as shown in FIG. 13 (b). The green compact M is formed by lowering and compressing the metal powder M ′. In this mold, as shown in FIG. 14, a bottom surface M 1 having a convex curved surface is formed on the green compact M by the lower punch 142. Thereafter, as shown in FIG. 13 (c), the lower punch 142 is raised to discharge the green compact M from the forming hole of the die 141, and the green compact M is discharged in the horizontal direction. M is removed from the mold.

  In the compression molding process, for example, as shown in FIG. 15, when a convex curved bottom surface M <b> 1 of the green compact M is molded with the die 141, it is necessary to provide a concave portion 141 a on the molding surface of the die 141. For this reason, when the green compact M is discharged from the forming hole of the die 141, the concave portion 141a of the die 141 and the convex curved bottom surface M1 of the green compact M are engaged in the die cutting direction (vertical direction in the figure). Therefore, the green compact M cannot be discharged from the die 141.

  Also, as shown in FIG. 16, when the curved bottom M1 of the green compact M is formed with the upper punch 143, the top surface having convex portions M21 at both ends in the long side direction as shown in FIG. M2 is formed by the lower punch 142. In this case, when the green compact M is taken out from the mold, the lower punch 142 and the projection M21 of the top surface M2 of the green compact M are engaged in the horizontal direction as shown in FIG. It is necessary to lift the powder M upward and separate it from the lower punch 142. As described above, since it takes time to release the green compact M, the productivity of the oil seal member is lowered.

  For the above reasons, in the conventional compression molding process, the curved bottom M1 of the green compact M is molded with the lower punch 142 as shown in FIGS. However, in this case, as shown in FIG. 13B, since the convex portion M21 of the top surface M2 of the green compact M protrudes upward in the drawing, both ends in the long side direction of the green compact M (convex portion M21). The thickness in the compression direction (vertical direction in the figure) differs between the formation portion and the central portion (the flat portion M22 formation portion). In the thick portion x ′ having a relatively large thickness (see FIG. 13B), the density of the sintered metal is reduced because the compression rate is small, and in the thin portion y ′ having a relatively small thickness, Since the compression rate increases, the density of the sintered metal increases. In this case, since the strength of the thick wall portions (low density portions) at both ends in the long side direction is relatively weak, for example, when the green compact M is transferred to the sintering process, chipping or cracking occurs in the low density portions. There is a fear. In addition, since the amount of deformation during sintering differs depending on the density of the green compact, if the density of the green compact varies from place to place, the amount of deformation during sintering may vary and the dimensional accuracy of the oil seal member may be reduced. There is.

Conventionally, by reducing the difference between the thickness H ₁ ′ of the thick portion X ′ of the oil seal member 120 and the thickness H ₂ ′ of the thin portion Y ′ as much as possible, the thick portion X ′ and the thin portion Y ′. The density difference was reduced (see FIG. 12B). However, in this case, since the step H ₃ ′ between the convex portion 122a and the flat portion 122b of the top surface 122 of the oil seal member 120 is reduced, it is difficult to lock both ends of the leaf spring 109 (see FIG. 11B). Become.

  For example, as shown in Patent Document 2, the green compact is sintered in a state of being aligned in one direction, or as shown in Patent Document 3, the sintering process is divided into two stages. If the method is adopted, damage to the green compact and reduction in dimensional accuracy during sintering can be suppressed. However, if these methods are adopted, the number of man-hours increases, resulting in a decrease in productivity.

  The problem to be solved by the present invention is to suppress the intrusion of oil from the surface opening of the oil seal member made of sintered metal, improve the responsiveness of the variable valve timing mechanism, and slide with the oil seal member. The purpose is to increase the wear resistance of the member.

  In addition, the problem to be solved by the present invention is to make the density of the green compact uniform, thereby preventing damage to the green compact and suppressing variation in the amount of deformation during sintering. Is to increase.

  In order to solve the above-mentioned problems, the present invention provides an oil formed into a slender shape by sintering a plurality of hydraulic chambers provided between a rotor and a housing of a variable valve timing mechanism in a liquid-tight manner. A sealing member, comprising a top surface having convex portions at both ends in the long side direction and a bottom surface having a curved surface provided on the opposite side of the top surface and curved in the short side direction. The surface is formed into a curved surface by subsequent sizing.

  In order to solve the above-mentioned problems, the present invention provides a plurality of hydraulic chambers provided between a rotor and a housing of a variable valve timing mechanism in a liquid-tight manner, and is formed into an elongated shape with sintered metal. A method for manufacturing an oil seal member, comprising compressing and molding metal powder, a top surface having convex portions at both ends in the long side direction, and a flat surface provided on the opposite side of the top surface A compression molding process for forming a green compact with a bottom surface, a sintering process for obtaining a sintered body by sintering the green compact, and a curved bottom surface in which the flat bottom surface of the sintered body is curved in the short side direction. It is performed through a sizing process for forming the film.

  In the compression molding process, the metal powder is relatively high in fluidity because the metal cavities are filled in a state where the metal powders are not bonded to each other. For this reason, in a compression molding process, metal powder flows by compression and the density of a green compact increases as a whole. On the other hand, in the sizing process, the metal powders are bonded to each other through the sintering process, so the fluidity of the metal powder is very low. For this reason, if a sintered compact is shape | molded by a sizing process, the pressing force of a metal mold | die will be hard to be transmitted to the inside of a sintered compact, and it will be in the state by which only the surface layer part of the sintered compact was crushed.

  Therefore, as described above, the bottom surface of the oil seal member is not a compression molding process, but is formed into a curved surface by sizing after sintering, so that the surface layer portion of the bottom surface is crushed and crushed. It is possible to reduce the surface area ratio of the surface. As a result, the intrusion of oil from the bottom surface can be suppressed, so that the hydraulic pressure in the hydraulic chamber is easily increased and the responsiveness of the rotation of the rotor is enhanced. In addition, since an oil film is easily formed between the oil seal member and the housing or the rotor, the lubricity of the sliding portion is enhanced, and the wear resistance of each member is enhanced.

  When the bottom surface of the oil seal member has a convex curved shape with the central part in the short side direction as the apex, the surface open area ratio at both ends in the short side direction is reduced in the short side direction due to the difference in compression rate during sizing. It becomes smaller than the surface opening rate in the central part. On the other hand, when the bottom surface of the oil seal member has a concave curved surface shape with the central portion in the short side direction as the apex, the surface open area ratio in the central portion in the short side direction is reduced in the short side direction due to the difference in compression rate during sizing. It becomes smaller than the surface area ratio at both ends.

  Further, the density of the green compact can be made uniform by making the compression direction of the green compact in the compression molding process different from the compression direction of the sintered body in the sizing process. Specifically, in the compression molding process, by compressing a pair of flat side surfaces provided on both sides of the bottom surface of the green compact with upper and lower punches, the thickness of the green compact in the compression direction is constant. Therefore, the density of the green compact can be made uniform by making the compression ratio uniform. In this case, the problem of interference between the die and the green compact in the compression molding process as shown in FIG. 15 can be avoided by forming the bottom surface of the green compact flat. In the subsequent sizing step, the flat bottom surface of the sintered body can be formed into a curved surface by compressing the top and bottom surfaces of the sintered body with the upper and lower punches.

By the way, according to the conventional method for manufacturing an oil seal member (see FIGS. 13 and 14), if the thickness difference between the thickness H ₁ of the thick portion and the thickness H ₂ of the thin portion of the oil seal member is large (that is, When the thickness ratio H ₂ / H ₁ between the thick part and the thin part is small), the difference in compression ratio between the thick part and the thin part of the green compact becomes large. For this reason, as shown in Table 1, when the thickness ratio H ₂ / H ₁ between the thick part and the thin part is less than 0.7, the thick part (convex part) of the green compact is sufficiently compressed. In this case, it was difficult to mold, and the thick part was low in density, resulting in insufficient strength. If the thickness ratio H ₂ / H ₁ is 0.7 or more and less than 0.75, the conventional method can be used for molding, but the thickness of the thick part of the green compact is not sufficient, and there are no cracks or chips. There was a fear.

Therefore, according to the method of the present invention, since the density of the oil seal member can be made uniform, as shown in Table 1, the thickness ratio H ₂ / H ₁ is less than 0.7, and further less than 0.6. Even in such a case, sufficient strength can be obtained. However, if the thickness ratio H ₂ / H ₁ is less than 0.4, the thickness of the thin portion is too thin, and it becomes extremely difficult to manufacture a mold for forming the thin portion of the green compact in the compression molding process. In fact, it cannot be molded. In addition, when the thickness ratio H ₂ / H ₁ is less than 0.5, it can be used, but the protruding amount of the convex part of the green compact (thickness difference between the thick part and the thin part) is Since it becomes large, it becomes easy to produce a crack and a chip | tip in a convex part. Therefore, H ₂ / H ₁ is 0.4 or more, preferably 0.5 or more.

From the above, the thickness ratio H ₂ / H ₁ between the thick part and the thin part of the oil seal member, that is, the distance H ₁ between the convex part on the top surface and the bottom surface, and the long side direction of the convex part on the top surface The ratio H ₂ / H ₁ of the distance H ₂ between the intermediate region and the bottom surface is preferably 0.4 or more and less than 0.7. As described above, by reducing the thickness ratio H ₂ / H ₁ between the thick part and the thin part, the protrusion amount of the convex part on the top surface can be increased, and the leaf spring can be easily locked. In order to reduce the wall thickness ratio H ₂ / H ₁ of the thick portion and the thin portion, increase the thickness H ₁ of the thick portion, or reducing the thickness of H ₂ thin portion Can be considered. However, since the thickness H ₁ of the thick portion is limited by the groove depth of the grooves 105a and 106a (see FIG. 11) provided in the vane 103 and the housing 104, it is difficult to increase the thickness H ₁ . Therefore, it is only necessary to reduce the thickness H ₂ of the thin wall portion, thereby reducing the size and weight of the oil seal member.

  By the way, since the oil seal member has an elongated shape, if the oil seal member is taken out of the sizing mold after the sizing process, the oil seal member 20 ′ warps as shown in FIG. 18 due to the spring back. There is. In this case, since the oil seal member 20 'cannot be finished in a shape that matches the sizing mold, the dimensional accuracy of the oil seal member 20' may be reduced. In particular, if the bottom surface 21 ′ of the oil seal member 20 ′ is warped, the contact state with the housing is deteriorated, and the sealing performance may be reduced. Therefore, by sizing the sizing mold by bending the bottom surface of the sintered body in the short side direction and forming the curved surface that is linear in the long side direction in the long side direction. It is preferable to cancel the warpage generated in the oil seal member.

  As described above, according to the present invention, since the intrusion of oil from the bottom surface can be suppressed by reducing the surface porosity of the bottom surface of the oil seal member made of sintered metal, the responsiveness of the rotation of the rotor is reduced. In addition to being enhanced, the wear resistance of the oil seal member and the sliding member is enhanced.

  In addition, according to the present invention, since the density of the green compact can be made uniform, local weak parts are not formed in the green compact, so that the green compact can be prevented from being damaged and deformed during sintering. The dimensional accuracy of the oil seal member is increased by suppressing variation in the amount.

It is (a) top view, (b) side view, and (c) front view of an oil seal member concerning one embodiment of the present invention. It is sectional drawing which shows the sliding part of an oil seal member and a housing. It is a figure which shows the manufacturing process of an oil seal member. It is (a) top view, (b) side view, (c) front view of a green compact. (A) is a cross-sectional view in the long side direction of the compression molding die, (b) is a cross-sectional view taken along line BB in FIG. (A), (c) is a cross-sectional view taken along line CC in FIG. d) is a sectional view taken along line DD in FIG. It is a long side direction sectional view showing signs that a green compact is released from a compression mold. It is a short side direction sectional view of a sizing die. It is a long side direction sectional view of a sizing metal mold. It is (a) top view, (b) side view, and (c) front view of an oil seal member concerning other embodiments. It is a short side direction sectional view of a sizing die concerning other embodiments. (A) is sectional drawing of the direction orthogonal to the cam shaft axial direction of a variable valve timing mechanism, (b) is sectional drawing in the XX line of (a) figure, (c) is Y of (a) figure. It is sectional drawing in the -Y line. It is the (a) top view, (b) side view, and (c) front view of the oil seal member of FIG. (A)-(c) is a longitudinal cross-sectional view of the compression mold in the manufacturing method of the conventional oil seal member. It is a short side direction sectional view of the compression molding die of Drawing 13 (b). It is sectional drawing of the short side direction of another compression molding metal mold | die. It is sectional drawing of the short side direction of another compression molding metal mold | die. (A) And (b) is a short side direction sectional view of the compression molding die of FIG. It is a side view of the oil seal member which warped.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The oil seal member 20 according to the embodiment of the present invention is provided at the same location as the oil seal member 120 shown in FIG. 11, that is, between the housing 104 and the vane 105 of the variable valve timing mechanism 100. The oil seal member 20 is formed of a sintered metal, for example, a sintered metal mainly composed of copper, iron, or a copper-iron alloy. The oil seal member 20 has the same shape as the oil seal member 120 shown in FIG. 12, and specifically, as shown in FIG. 1, a bottom surface 21 and a top surface 22 provided on the opposite side of the bottom surface 21 And a pair of flat side surfaces 23, 23 provided on both sides of the bottom surface 21 in the short side direction and a pair of flat end surfaces 24, 24 provided on both sides of the bottom surface 21 in the long side direction. The bottom surface 21 slides with the inner peripheral surface of the housing 104, and the end surface 24 slides with the inner side end surface of the housing 104 (see the oil seal member 120 in FIG. 11B).

The top surface 22 has a pair of convex portions 22a provided at both ends in the long side direction and a flat portion 22b provided in the region between the long side directions. Thereby, the thick portion X having a relatively thick thickness in the direction in which the top surface 22 and the bottom surface 21 face each other (the vertical direction in FIG. 1B) is provided in the formation region of the convex portion 22a. A thin portion Y having a relatively thin thickness in the same direction is provided in the formation region 22b. The ratio H ₂ / H ₁ and the wall thickness of H ₂ thickness H ₁ and the thin portion Y of the thick portion X is in the range of 0.4 or more and less than 0.7, preferably less than 0.5 to 0.6 Is set within the range. The total axial length L of the oil seal member 20 is about 15 to 30 mm, and the ratio L / H ₁ between the total axial length L and the thickness H ₁ of the thick portion X is in the range of 5 to 10, Preferably it is set within the range of 6-8. A leaf spring 109 (see FIG. 11B) is mounted between the long sides of the pair of convex portions 22a, and both ends of the leaf spring 109 are locked by the pair of convex portions 22a. A chamfered portion 25 is provided outside the convex portion 22a in the long side direction. The chamfered portion 25 can be omitted or made smaller than the illustration.

  As shown in FIG. 1C, the bottom surface 21 is formed in a convex curved surface curved in an arc shape in the short side direction. In this embodiment, the bottom surface 21 is formed in a convex cylindrical surface with the central part in the short side direction as a vertex. Is done. The bottom surface 21 of the oil seal member 20 is in contact with the inner peripheral surface 104a of the housing 104 as shown in FIG. For this reason, in order to improve the sealing performance by the oil seal member 20, the curvature of the bottom surface 21 of the oil seal member 20 and the curvature of the inner peripheral surface 104a of the housing 104 are completely matched, and these surfaces are brought into surface contact. Is ideal. However, since it is practically impossible to completely match the curvatures of these surfaces, the curvature of the bottom surface 21 of the oil seal member 20 is made slightly larger than the curvature of the inner peripheral surface 104a of the housing 104. (The curvature radius is slightly reduced), and these surfaces are in a line contact state close to surface contact. Thereby, the short side direction central portion 21 a of the bottom surface 21 is in line contact with the inner peripheral surface 104 a of the housing 104 (the contact portion is indicated by P), and both short side direction end portions 21 b of the bottom surface 21 are in contact with the inner peripheral surface of the housing 104. It is opposed through a gap. Thereby, a gap Q having a tapered shape toward the contact portion P is formed between the bottom surface 21 and the inner peripheral surface 104 a of the housing 104, and an oil film is formed in the gap Q and the contact portion P.

  The bottom surface 21 of the oil seal member 20 is a surface formed into a convex curved surface by sizing. For this reason, the surface of the bottom surface 21 is in a crushed state, and the surface porosity is smaller than the surface porosity of the top surface 22, for example. In particular, the short-side end portions 21b of the bottom surface 21 have a particularly small surface opening ratio because of a high compression ratio by sizing, and the surface opening ratio is smaller than the short-side direction center portion 21a of the bottom surface 21.

  Thus, since the surface opening rate of the bottom surface 21 is small, the oil in each hydraulic chamber is less likely to enter the oil seal member 20 from the bottom surface 21, and therefore the rotor 103 when the hydraulic pressure is supplied to each hydraulic chamber. The responsiveness of rotation (see FIG. 10) is improved. Further, since the surface area ratio of the bottom surface 21 is small, the oil in the sliding portion (contact portion P and gap Q) between the oil seal member 20 and the housing 104 is difficult to escape into the oil seal member 20. For this reason, since the lubricity can be enhanced while maintaining the state in which the oil film is formed on the sliding portion, the wear resistance of the oil seal member 20 and the housing 104 is enhanced.

  Hereinafter, a method for manufacturing the oil seal member 20 having the above configuration will be described. As shown in FIG. 3, the oil seal member 20 includes a compression molding process in which a metal powder is compression molded to form a green compact 30, a sintering process in which the green compact 30 is sintered to obtain a sintered body 40, And it manufactures through the sizing process which sizes the sintered compact 40 to a predetermined dimension.

  As shown in FIG. 4, the green compact 30 formed in the compression molding process has a flat bottom surface 31. In addition, the green compact 30 includes a top surface 32 having a convex portion 32a and a flat portion 32b, a side surface 33, an end surface 34, and a chamfered portion 35. Except for a slight change in dimensions due to the sizing process, the oil seal member 20 is the same as that shown in FIG.

  In the compression molding process, as shown in FIG. 5A, the metal powder is filled in the cavity formed by the molding hole 51a of the die 51 and the molding surface 52a of the lower punch 52, and the upper punch 53 is lowered to lower the metal powder. The green compact 30 is formed by compressing. In this mold, the pair of flat side surfaces 33 and 33 of the green compact 30 are compression-molded by the upper punch 53 and the lower punch 52, and at the same time, the bottom surface 31 of the green compact 30 is formed by the molding hole 51 a of the die 51. The top surface 32, the end surface 34, and the chamfered portion 35 are formed (see FIG. 5B). The inner surface (molding surface) of the molding hole 51a of the die 51 is all a flat surface parallel to the compression direction. Therefore, the bottom surface 31, the top surface 32, the end surface 34, and the chamfered portion 35 of the green compact 30 are molded flat. (See FIG. 4).

  Thus, by compressing and molding the pair of flat side surfaces 33, 33 of the green compact 30 with the upper punch 53 and the lower punch 52, the thickness of the green compact 30 in the compression direction can be made constant. it can. Specifically, the thickness of the green compact 30 is constant in any of the cross sections in the compression direction of FIGS. 5 (a), (c), and (d). For this reason, the compression ratio of the green compact 30 is constant throughout the entire area, and the density can be made uniform. As a result, the density of the green compact 30 becomes uniform, and a local low density portion (that is, a fragile portion) is not formed on the green compact 30. The situation where 30 is damaged can be prevented.

Further, by making the density of the green compact 30 constant, the thickness h ₂ of the thin portion y is made smaller than the thickness h ₁ of the thick portion x of the green compact 30 so that the convex portion 32 a The level difference h ₃ between the flat portion 32b can be increased (see FIG. 4B). Accordingly, the thickness H ₂ of the thin portion Y is reduced with respect to the thickness H ₁ of the thick portion X of the oil seal member 20, and the step H ₃ between the convex portion 22a and the flat portion 22b is increased. (See FIG. 1B), which makes it easier to lock the leaf spring 109 (see FIG. 11B). Further, by reducing the thickness H ₂ of the thin wall portion Y, the oil seal member 20 can be reduced in size and weight.

  Thereafter, as shown in FIG. 6, the upper punch 53 and the lower punch 52 are raised together with the green compact 30, and the green compact 30 is discharged from the forming hole 51 a of the die 51. At this time, since the forming hole 51a of the die 51 and the bottom surface 31 of the green compact 30 formed by the forming hole 51a are all flat surfaces parallel to the compression direction (that is, the die cutting direction), The green compact 30 does not engage in the mold release direction. Thereafter, the green compact 30 placed on the lower punch 52 is discharged in the horizontal direction, whereby the green compact 30 can be easily released. At this time, since the flat side surface 33 of the green compact 30 is formed by the flat forming surface 52a of the lower punch 52, these surfaces do not engage in the horizontal direction.

  In the sintering step, the green compact 30 transferred from the green compacting step is sintered at a predetermined temperature, whereby the metal powders of the green compact 30 are bonded to each other, and the sintered body 40 is obtained. Since the sintered body 40 has substantially the same shape as the green compact 30, detailed description thereof is omitted. Although the dimensional change occurs in the green compact 30 due to heating in this sintering process, since the density of the green compact 30 is uniform as described above, the amount of deformation during sintering becomes uniform, and the green compact 30 is sintered. As a result, a decrease in dimensional accuracy (particularly a change in shape) when forming the sintered body 40 can be suppressed.

  In the sizing process, the sintered body 40 is compressed in a direction different from the compression direction of the green compact 30 in the compression molding process. Specifically, as shown in FIG. 7, the bottom punch 41 and the top surface 42 of the sintered body 40 (shown by dotted lines) disposed on the inner periphery of the forming hole 61 a of the die 61 are replaced by the upper punch 62 and the lower punch 63. Compress from above and below. The shape of the molding surface 63a of the lower punch 63 is a concave curved surface with a concave central portion in the short side direction. By pressing the molding surface 63a against the sintered body 40, the convexity of the oil seal member 20 is formed. A curved bottom surface 21 is formed. The sizing process can also be performed in a state where the sintered body 40 is turned upside down with respect to the direction shown in FIG. 7, that is, in a state where the top surface 42 of the sintered body 40 faces downward. In this case, after the sizing step, the convex portion of the top surface 42 of the sintered body 40 and the lower punch are engaged in the horizontal direction. However, the sintered body 40 after sizing has very high strength and hardness. Since it is high, for example, it can be easily released by blowing and blowing air.

  By this sizing process, the surface layer portion of the sintered body 40 is crushed, and the surface opening ratio of the oil seal member 20 is reduced. In particular, the bottom surface 21 of the oil seal member 20 formed into a curved surface from the flat surface (the bottom surface 41 of the sintered body 40) has a large surface deformation rate due to a large amount of deformation (compression rate) due to the sizing process. Especially, since the deformation | transformation amount is especially large in the short side direction both ends of the bottom face 21, surface opening rate becomes small compared with the short side direction center part. In general, on the surface of a sintered metal, a portion having a small surface porosity is more glossy than a portion having a large surface porosity. Therefore, the bottom surface 21 of the oil seal member 20 according to the present embodiment has gloss at both ends in the short side direction than at the center. In other words, if there is a difference in gloss between the short side direction both ends of the bottom surface 21 and the central portion, it can be estimated that this surface is formed into a curved surface by sizing.

  Since the side surface 23 and the end surface 24 of the oil seal member 20 slide in a state of being pressed against the forming hole 61a of the die 61 in the sizing process, the surface opening ratio is the smallest among the surfaces of the oil seal member 20. It has become. Therefore, the surface open area ratio of the oil seal member 20 is (1) the side surface 23 and the end surface 24, (2) the width direction both ends of the bottom surface 21, (3) the width direction center portion of the bottom surface 21, the top surface 22, and The chamfered portion 25 increases in order.

  The molding surface 63a of the lower punch 63 of the sizing mold has a curved shape in which the central portion in the long side direction is expanded upward as shown in an exaggerated manner in FIG. This is provided in order to cancel out the warp (see FIG. 18) generated in the oil seal member 20 due to the spring back when taken out from the sizing mold. Thereby, the bottom face 21 of the oil seal member 20 taken out from the mold can be linear in the long side direction. Although the top surface 22 of the oil seal member 20 may be warped, the top surface 22 has a lower surface accuracy than the bottom surface 21 that slides with the housing. Therefore, as shown in FIG. 8, a curved shape for offsetting the warp of the oil seal member 20 may be provided at least on the molding surface 63 a of the lower punch 63. Of course, the molding surface 62a of the upper punch 62 may have a curved shape that cancels the warpage of the top surface 22.

  The present invention is not limited to the above embodiment. Hereinafter, although other embodiment of this invention is described, the same code | symbol is attached | subjected to the location of the function similar to said embodiment, and duplication description is abbreviate | omitted.

  In the above embodiment, the oil seal member 20 (corresponding to the oil seal member 120 in FIG. 11A) that fits into the groove 105a of the vane 105 of the rotor 103 and slides with the inner peripheral surface of the housing 104 is shown. However, the present invention is not limited to this, and the present invention is applied to an oil seal member (corresponding to the oil seal member 130 in FIG. 11A) provided in the groove 106 a of the tooth 106 of the housing 104 and sliding with the outer peripheral surface of the rotor 103. You can also In this case, the bottom surface 21 of the oil seal member 20 may be formed into a convex curved surface shape as in the above embodiment, or as shown in FIG. 9, a concave curved surface with a concave portion in the short side direction. You may shape | mold.

  As shown in FIG. 10, the sizing mold for molding the concave curved bottom surface 21 of the oil seal member 20 shown in FIG. 9 is a convex curved surface in which the molding surface 63a of the lower punch 63 bulges the center in the short side direction upward. It is made into a shape. In this case, the flat bottom surface 41 of the sintered body 40 (indicated by the dotted line) is pressed by the molding surface 63a of the lower punch 63, and the concave curved bottom surface 21 is molded. At this time, since the amount of compression is large in the center portion in the short side direction of the bottom surface 21, the surface area ratio is relatively smaller than both end portions in the short side direction. Therefore, oil can be kept between the central portion in the short side direction of the bottom surface 21 and the rotor 103 (see FIG. 11), and lubricity is improved. Moreover, since the amount of compression is large in the center part of the short side direction of the bottom face 21, the density is relatively higher than both ends of the short side direction, thereby increasing the strength. As described above, in the oil seal member 130, the lubricity and strength are enhanced at the central portion in the short side direction of the bottom surface 21 that mainly contacts and slides with the outer peripheral surface of the rotor 103, so that the wear resistance is particularly enhanced. it can.

  Further, in the above-described embodiment, the oil seal member 20 is arranged at the circumferential center (the position of the oil seal member 120 in FIG. 11A) of the tip surface of each vane 105 of the rotor 103 or each of the housings 104. Although provided at the circumferential center of the tip surface of the tooth 106 (position of the oil seal member 130 in FIG. 11A), the present invention is not limited to this, and the circumference of the tip surface of the vane 105 or the tooth 106 is not limited. You may provide the oil seal member 20 in the position offset from the direction center part.

  Further, in the above embodiment, as shown in FIG. 11A, the oil seal member 20 (the oil seal member 120 in FIG. 11A) fitted in the groove portion 105a of the vane 105 of the rotor 103 is disposed in the housing. On the contrary, a groove portion is provided on the inner peripheral surface of the housing 104, and the bottom surface 21 of the oil seal member 20 fitted in the groove portion is disposed outside the vane 105. It may be slid in contact with the radial surface. In this case, the bottom surface 21 of the oil seal member 20 is formed in a convex curved surface shape or a concave curved surface shape. Similarly, in the above embodiment, the oil seal member 20 (the oil seal member 130 in FIG. 11A) fitted in the groove 106 a of the tooth 106 of the housing 104 is slid in contact with the outer peripheral surface of the rotor 103. However, conversely, a groove portion may be provided on the outer peripheral surface of the rotor 103, and the oil seal member 20 fitted in the groove portion may be slid in contact with the inner diameter surface of the tooth 106.

20 Oil seal member 21 Bottom surface 22 Top surface 23 Side surface 24 End surface 30 Compact 31 Bottom surface 32 Top surface 33 Side surface 34 End surface 40 Sintered body 41 Bottom surface 42 Top surface 51 Die 52 Lower punch 53 Upper punch 61 Die 62 Upper punch 63 Lower Punch 100 Variable valve timing mechanism 103 Rotor 104 Housing 105 Vane 106 Teeth 107, 108 Hydraulic chamber 109, 110 Leaf spring S Camshaft X Thick part Y Thin part H ₁ Thick part thickness H ₂ Thin part thickness L Overall axial dimension of oil seal member

Claims (16)

A plurality of hydraulic chambers provided between the rotor and the housing of the variable valve timing mechanism are liquid-tightly divided, and an oil seal member formed into an elongated shape with sintered metal,
A top surface having convex portions at both ends in the long side direction, and a bottom surface provided on the opposite side of the top surface and having a curved shape curved in the short side direction,
An oil seal member, wherein the bottom surface is a surface formed into a curved surface by sizing after sintering.   The oil seal member according to claim 1, wherein the bottom surface has a convex curved surface shape with the short side direction central portion as a vertex.   3. The oil seal member according to claim 2, wherein a surface opening rate at both ends in the short side direction of the bottom surface is smaller than a surface opening rate in a center portion in the short side direction of the bottom surface.   The oil seal member according to claim 1, wherein the bottom surface has a concave curved surface shape with a short side direction central portion as a vertex.   5. The oil seal member according to claim 4, wherein a surface porosity at a center portion in the short side direction of the bottom surface is smaller than a surface porosity at both end portions in the short side direction of the bottom surface. The ratio H ₂ / H ₁ between the distance H ₁ between the convex portion of the top surface and the bottom surface and the distance H ₂ between the long side direction region of the convex portion of the top surface and the bottom surface is 0.4 or more. The oil seal member according to any one of claims 1 to 5, wherein the oil seal member is less than 7. Oil seal member according to claim 1 distance H ₁ and the ratio L / H ₁ between a long side direction overall length L is in the range of 5 to 10 and said bottom surface and said convex portion.   The oil seal member according to any one of claims 1 to 7, wherein the bottom surface is a cylindrical surface.   The oil seal member according to claim 1, wherein the bottom surface slides with an inner peripheral surface of the housing.   The oil seal member according to any one of claims 1 to 8, wherein the bottom surface slides with an outer peripheral surface of the rotor.   A variable valve timing mechanism comprising: the oil seal member according to claim 1; a rotor attached to a camshaft; and a housing that rotatably accommodates the rotor. A method for liquid-tightly partitioning a plurality of hydraulic chambers provided between a rotor and a housing of a variable valve timing mechanism, and manufacturing an oil seal member formed into an elongated shape with sintered metal,
A compression molding step of molding a green compact having a top surface having protrusions at both ends in the long side direction and a flat bottom surface provided on the opposite side of the top surface by compression molding metal powder; An oil seal that is subjected to a sintering process for obtaining a sintered body by sintering the green compact, and a sizing process for forming a flat bottom surface of the sintered body into a curved surface curved in a short side direction. Manufacturing method of member.   The method for producing an oil seal member according to claim 12, wherein the compression direction of the green compact in the compression molding step is different from the compression direction of the sintered body in the sizing step.   In the compression molding step, a pair of flat side surfaces provided on both sides in the short side direction of the bottom surface of the green compact are compressed with the upper and lower punches, and in the sizing step, the top surface and the bottom surface of the sintered body are compressed with the upper and lower punches. Item 14. A method for producing an oil seal member according to Item 13.   The method for producing an oil seal member according to claim 14, wherein in the sizing step, the flat bottom surface of the sintered body is compressed into a curved shape by compressing with a lower punch or an upper punch.   The bottom surface of the sintered body is curved in the short side direction, and the molding surface of a sizing mold for forming a curved surface that is linear in the long side direction is curved in the long side direction. The manufacturing method of the oil seal member in any one of.

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