WO2012157383A1

WO2012157383A1 - Oil seal member and method for manufacturing same

Info

Publication number: WO2012157383A1
Application number: PCT/JP2012/060267
Authority: WO
Inventors: 敏彦毛利
Original assignee: Ntn株式会社
Priority date: 2011-05-16
Filing date: 2012-04-16
Publication date: 2012-11-22
Also published as: JP2012241729A; JP5749073B2

Abstract

An oil seal member consisting of sintered metal and capable of effectively preventing oil from entering the inside can be mass manufactured without a particular increase in cost. An oil seal member (1) consisting of sintered metal liquid-tightly defines a hydraulic chamber (106) formed between a rotor (101) and a housing (103). The oil seal member (1) is formed from a sintered metal material for bearings and comprises: a pair of side surfaces (4, 4) which face each other in the rotation direction of the rotor (101) and which are parallel to each other; and a surrounding surface comprising surfaces which extend between both the side surfaces (4, 4) and one of which slides on the inner diameter surface of the housing (103). The surrounding surface comprises: an upper surface (2) having an irregular surface shape; a lower surface (3) sliding on the housing (103); a pair of end surfaces (5, 5); and a pair of sloped surfaces (6, 6). In the oil seal member (1), each one of the pair of side surfaces (4, 4) and the surrounding surface is a molded surface.

Description

Oil seal member and manufacturing method thereof

The present invention relates to an oil seal member that liquid-tightly partitions a plurality of hydraulic chambers formed between a rotor and a housing constituting a variable valve timing mechanism, and a method for manufacturing the same, and in particular, an oil seal made of sintered metal. The present invention relates to an improvement of a member and a manufacturing method thereof.

The variable valve timing mechanism is attached to the camshaft of the engine to vary the opening / closing timing of the intake / exhaust valves. For example, as shown in FIGS. 14a to 14c, the rotor rotates integrally with the camshaft S. 101 and a cylindrical housing 103 that rotates in synchronization with a crankshaft of an engine (not shown) and rotatably accommodates the rotor 101. In the variable valve timing mechanism 100 shown in the figure, the rotor 101 has vanes 102 projecting on the outer diameter side at four locations in the circumferential direction, and the housing 103 surrounds the teeth 104 projecting on the inner diameter side. It has four places in the direction. Then, the teeth 104 and the vanes 102 are alternately arranged in the circumferential direction, whereby hydraulic chambers 106 are formed on both circumferential sides of each vane 102 (the teeth 104).

A groove portion 105 extending in the axial direction is formed on each of the outer diameter surface of the vane 102 and the inner diameter surface of the tooth 104, and one seal device 110 is attached to each groove portion 105. The seal device 110 includes an oil seal member 120 extending in the axial direction of the rotor 101 (housing 103), and a plate spring 130 as an urging member interposed between the oil seal member 120 and the groove portion 105 in a compressed state. Thus, the oil seal member 120 is constantly urged against the counterpart member (the housing 103 or the rotor 101) by the elastic restoring force of the leaf spring 130. Thereby, the lower surface 123 of the oil seal member 120 is pressed against the counterpart member, and the hydraulic chamber 106 is partitioned in a liquid-tight manner (see, for example, Patent Document 1).

Here, among the oil seal members 120, general ones attached to the vanes 102 of the rotor 101 are shown in FIGS. 15a and 15b. The oil seal member 120 is opposed to the upper surface 122 disposed to face the groove bottom surface of the groove portion 105 of the vane 102, the lower surface 123 that slides on the inner surface of the housing 103 on the opposite side of the upper surface 122, and the rotor 102 in the rotational direction. It has a long thin plate shape with a pair of

parallel side surfaces

124, 124 connecting the upper surface 122 and the lower surface 123, and both end portions in the longitudinal direction (left-right direction in FIG. 15a / axis direction of the rotor 102) And a thick portion having a relatively large thickness between the upper and lower surfaces and a thin portion having a relatively small thickness between the upper and lower surfaces provided at the central portion in the longitudinal direction. The lower surface 123 is formed in a convex curved surface curved in the short direction (left and right direction in FIG. 15b / rotation direction of the rotor 102), and the upper surface 122 is provided with convex portions 122a at both ends in the longitudinal direction. Thereby, it is formed in an uneven shape in the longitudinal direction.

The above oil seal member is often formed of a material that is excellent in moldability and can be mass-produced at low cost, for example, an elastic material such as resin or rubber, or a sintered metal material. In particular, the sintered metal is excellent in dimensional stability and can effectively enhance the lubricity of the sliding portion due to the porous body. Therefore, if the hydraulic chamber is partitioned liquid-tightly with an oil seal member made of sintered metal, the sliding state between the oil seal member and the counterpart member can be kept good, so the responsiveness of the variable valve timing mechanism is improved. It is possible to enhance and maintain the responsiveness stably. Therefore, recently, an oil seal member made of sintered metal tends to be used heavily.

JP 2009-297812 A JP-A-8-127808

The oil seal member made of sintered metal has been often formed of a sintered metal material for structural parts defined in Appendix 2 of JIS Z2550. A sintered metal body formed of a sintered metal material for a structural component is generally high in density because mechanical strength is important. For this reason, it has been found that an oil seal member made of the material is excellent in wear resistance but may not be able to ensure the required slidability. Accordingly, when the variable valve timing mechanism equipped with this oil seal member is operated, the frictional resistance between the sliding portion of the housing and the oil seal member and the sliding portion of the rotor and the oil seal member is increased, and the engine rotation There have been problems such as a decrease in responsiveness of the valve timing mechanism to a number change, and a large loss torque.

Therefore, the inventor of the present application tried to use an oil seal member formed of a sintered metal material for a bearing specified in Appendix 1 of JIS Z2550. A metal sintered body formed of a sintered metal material for bearings is generally low in density because oil film forming ability is more important than mechanical strength. Therefore, if an oil seal member formed of this material is used, it is possible to improve the lubricity at the sliding portion, improve the response of the valve timing mechanism to changes in the engine speed, and reduce the loss torque. . However, on the other hand, because of the low density, oil intervening in the hydraulic chamber (supplied to the hydraulic chamber) and oil intervening in the sliding part enter the oil seal member through the surface opening. It becomes easy. In this case, it is difficult to appropriately increase the hydraulic pressure in the hydraulic chamber, and the responsiveness of the valve timing mechanism may be lowered. In addition, the oil seal member and / or the sliding member may slide due to the reduced lubricity of the sliding portion. The wear of the mating member is likely to proceed early.

The above-mentioned various problems are caused by forming an appropriate surface treatment film on the surface of the metal sintered body, as described in, for example, JP-A-8-127808 (Patent Document 2), or on the surface of the metal sintered body. It can be eliminated as much as possible by applying machining such as grinding and turning to crush the surface openings. However, if such a means is adopted, the manufacturing cost increases as the number of steps increases, and the cost merit due to forming the oil seal member with sintered metal is lost.

In view of the above circumstances, the object of the present invention is to enable mass production of an oil seal member made of sintered metal capable of effectively suppressing internal penetration of oil without causing a particular increase in cost. Therefore, it is possible to provide a low-cost variable valve timing mechanism that is high in responsiveness and durability.

The present invention created to achieve the above object is an oil seal member made of sintered metal that liquid-tightly partitions a hydraulic chamber formed between a rotor and a housing constituting a variable valve timing mechanism. A pair of side surfaces facing each other in the rotational direction of the rotor and a plurality of surfaces that circulate between both side surfaces, one of which is the outer diameter surface of the rotor or the inner diameter of the housing. One of the surfaces and a circumferential surface that constitutes a sliding surface that slides, and the pair of side surfaces and the circumferential surface are both molding surfaces.

The “sintered metal material for bearing” in the present invention refers to a material that is preferably used when obtaining a sintered metal bearing. For example, those specified in Appendix 1 of JIS Z2550 are used. The The sintered metal material is a powder material in which metal powder is used as a main raw material and appropriate amounts of additives and binders that impart various properties are added thereto. In addition, the “circumferential surface” referred to here refers to a surface including the upper surface 122 and the lower surface 123, referring to FIGS. 15 a and 15 b described above.

Thus, the oil seal member made of sintered metal according to the present invention has a pair of side surfaces and a circumferential surface composed of a plurality of surfaces that circulate between both side surfaces as a molding surface. That is, the pair of side surfaces and the circumferential surface (outer surface whole area) are compressed by a molding die used in the manufacturing process of the oil seal member, and deformed following the cavity of the molding die, so that a so-called crushing process is performed. It means that the plastic working surface is executed. Therefore, among the surfaces constituting the oil seal member, the surface open area ratio of the sliding surface sliding with the rotor or the housing or the surface (side surface) always in contact with oil is not subjected to special post-processing or the like. It can be appropriately reduced. As a result, it is possible to mass-produce a sintered metal oil seal member that has a high effect of suppressing the intrusion of oil and is excellent in wear resistance at a low cost without causing a particular increase in cost. As described above, the sintered metal formed by using the sintered metal material for bearings has a lower density than that formed by using the sintered metal material for structural parts. However, there is a demerit that it is difficult to suppress internal penetration of oil and improve wear resistance. In contrast, the above-described configuration of the present invention eliminates the disadvantages of using a sintered metal material for a bearing, so an oil seal member manufactured using a sintered metal material for a bearing is a variable valve timing mechanism. It can be suitably used as an oil seal member.

The oil seal member according to the present invention having the above-described structure includes a compression molding step for obtaining a green compact by compression molding a sintered metal material for a bearing, and a sintering for obtaining a sintered body by sintering the green compact. In a manufacturing method including a step and a sizing step in which the sintered body is compressed to finish into a final shape, the compression direction of the green compact by a pair of punches used in the compression molding step and the sintering by a pair of punches used in the sizing step It can be manufactured by changing the compression direction of the body.

At the time of compression molding of the green compact or sizing of the sintered body, the surface layer portion of the surface directly compressed by the pair of punches is in a state where the porous structure becomes dense and crushed, but the degree of crushed ( The effect of reducing the surface porosity is much greater when the green compact or sintered body is crushed as it slides on the molding die. Therefore, if both the pair of side surfaces and the circumferential surface are crushed by sliding with the molding die, an oil seal member having a smaller surface opening rate and a further enhanced effect of suppressing oil intrusion can be easily obtained. Obtainable.

In addition, in order to determine whether or not each of the surfaces is crushed by sliding with the molding die, it is possible to determine whether or not the metal powder constituting each of the surfaces has a sliding mark. it can. The sliding trace is a trace that can be formed by plastic deformation of the metal powder, whereas when each surface is formed by removal processing such as turning or grinding, the metal powder that constitutes each of the surfaces, This is because a broken mark remains by sliding with the blade or the grindstone. For reference, FIGS. 21a and 21b show enlarged photographs of the surface of a sintered metal body that has been ground and turned, respectively.

If a sintered metal material containing a solid lubricant is used, the releasability can be improved and a highly accurate metal sintered body can be obtained, and the sliding characteristics of the metal sintered body can be enhanced. Here, when the green compact of the material powder containing the metal powder and the solid lubricant is heated to obtain the metal sintered body, the compound of the metal powder and the solid lubricant is mainly formed by adjusting the heating temperature and the heating time. Or a crystal structure mainly composed of a solid solution of a metal powder and a solid lubricant. The latter is superior in sliding characteristics as compared to the former, and the sintering temperature is relatively lower than that in the former, so that the amount of dimensional change associated with sintering can be reduced. As a result, it is advantageous in obtaining an oil seal member. Therefore, when forming an oil seal member using a sintered metal material containing a solid lubricant, the oil seal member preferably has a crystal structure mainly composed of a solid solution of metal powder and solid lubricant.

In the above configuration, the surface area ratio of the pair of side surfaces and the circumferential surface is preferably 5% or more and 40% or less. In this way, the amount of oil penetration can be effectively reduced, so that an appropriate amount of oil can be interposed in the sliding portion between the oil seal member and the counterpart member and the hydraulic chamber. Thereby, the responsiveness and durability life of the variable valve timing mechanism can be improved.

The sliding surface of the oil seal member is a surface that slides (contacts slidably) with a curved surface curved in the rotational direction of the rotor, such as the outer diameter surface of the rotor or the inner diameter surface of the housing. Depending on the mode, the sealing performance of the hydraulic chamber and the response of the variable valve timing mechanism are greatly affected. Therefore, the sliding surface of the oil seal member is formed in a curved surface curved in the rotational direction of the rotor so that a good sliding contact state can be maintained between the outer diameter surface of the rotor or the inner diameter surface of the housing. Is desirable. Further, among the circumferential surfaces of the oil seal member, the surface facing the sliding surface in the radial direction of the rotor is a surface to which a biasing member such as a leaf spring extending in the axial direction of the rotor is attached. It is desirable to form an uneven shape in the axial direction. The present invention can be preferably applied to an oil seal member having such a shape.

Here, the oil seal member made of sintered metal having the above shape has been manufactured as follows. In the following, a method for manufacturing the oil seal member 120 shown in FIG. 15 in which the lower surface 123 constituting the sliding surface has a convex curved surface will be described.

First, in the compression molding process shown in FIGS. 16a to 16c, after filling the material powder 150 ′ into the cavity defined by the die 141 and the lower punch 143 (FIG. 16a), the upper punch 142 is lowered to lower the material powder 150. ′ Is compressed to form the green compact 150 (FIG. 16 b). As shown in FIG. 17, the lower punch 143 is provided with a concave curved surface portion 143a corresponding to the shape of the lower surface 123 constituting the sliding surface of the oil seal member 120, and the green compact 150 is compression molded. At the same time, the lower surface of the green compact 150 is formed into a convex curved surface (rough molding). Then, after forming the green compact 150, the upper punch 142 and the lower punch 143 are raised, the green compact 150 is discharged from the die 141, and the green compact 150 is discharged in the horizontal direction (FIG. 16c). In order to form the bottom surface of the green compact 150 into a convex curved surface, in addition to the above, as shown in FIG. 18, a die 141 having a concave curved surface portion 141a on the inner diameter surface is used, or FIG. As shown, it is conceivable to use an upper punch 142 whose pressing surface 142a has a concave curved surface shape. However, when the lower surface of the convex curved surface is molded with the die 141, the concave curved surface portion 141a of the die 141 and the lower surface of the green compact 150 are engaged in the mold release direction, so that the green compact 150 is discharged from the die 141. I can't do that. When the convex curved lower surface is molded with the upper punch 142, the concave and convex upper surface is molded with the lower punch 142, as shown in FIG. 20a. Since the green compact 150 and the lower punch 143 engage with each other in the paying-out direction when discharged from the 141 (see FIG. 20b), it takes time to pay out the green compact 150, and the productivity is reduced.

In view of these circumstances, conventionally, as shown in FIG. 17, the lower punch 143 constituting the compression molding die is used to form the lower surface of the green compact 150 into a convex curved surface, and the upper punch 142 constituting the compression molding die. Thus, the upper surface of the green compact 150 was formed into an uneven shape. However, when this is done, a large density difference occurs between the longitudinal end portion and the longitudinal center portion of the green compact 150. When such a density difference exists in the green compact 150, cracks and chips are likely to occur when the green compact 150 is transferred to the sintering process, and the deformation amount during sintering is the longitudinal direction of the green compact 150. Therefore, it is difficult to obtain the oil seal member 120 having a predetermined shape. Such a problem can be solved as much as possible by molding the green compact 150 having a small step between the irregularities on the upper surface. However, in the assembly process of the variable valve timing mechanism, the leaf springs 130 (see FIG. 14) are attached and fixed between the convex portions 122a provided at the two ends of the upper surface 122 of the oil seal member 120. If the height is reduced, the attachment of the leaf spring 130 may be reduced.

In view of the various problems described above, when the oil seal member having the above shape is manufactured, the sliding surface is formed into a curved surface curved in the rotational direction of the rotor by sizing after sintering. More specifically, the peripheral surface of the green compact is formed by a die used in the compression molding process of the material powder, and both sides of the green compact are formed by a pair of upper and lower punches (see FIG. 6). In the sizing process, both the side surfaces 14 and both end surfaces 5 of the sintered body are formed by the die 41, the upper surface 2 is formed by the upper punch 42, and the sliding surface 3 is curved in the rotational direction of the rotor by the lower punch 43. Molded into a curved surface (see FIGS. 9 and 10). In this way, it is possible to obtain a green compact with a uniform density, and thus an oil seal member, without impairing the mold releasability of the green compact.

The curved sliding surface curved in the rotational direction of the rotor can be either a convex curved surface or a concave curved surface. When obtaining a convex curved sliding surface, due to the difference in compression ratio during sizing, the surface area ratio of the sliding surface at both ends of the rotor in the rotational direction is the top of the sliding surface (the central portion of the rotor in the rotational direction). ) Is smaller than the surface open area ratio. On the other hand, when obtaining a concave curved sliding surface, the surface opening ratio at the apex of the sliding surface is the surface opening at both ends of the rotor in the rotational direction due to the difference in compression rate during sizing. Smaller than the rate.

A variable valve timing mechanism may be configured by the oil seal member according to the present invention described above, a rotor having a mounting groove for the oil seal member, and a housing that rotatably mounts the rotor. it can.

As described above, according to the present invention, it is possible to mass-produce a sintered metal oil seal member capable of effectively suppressing internal penetration of oil without causing a particular increase in cost. As a result, it is possible to provide a variable valve timing mechanism with high sliding characteristics and excellent responsiveness and durability life at low cost.

It is a top view of the oil seal member concerning one embodiment of the present invention. It is a side view of the oil seal member shown in FIG. It is a front view of the oil seal member shown in FIG. It is sectional drawing which expands and shows the sliding part vicinity of an oil seal member and a housing. It is an enlarged view which shows notionally the surface layer part of an oil seal member. It is a figure which shows typically the manufacturing process of an oil seal member. It is a top view of the green compact processed into the oil seal member shown in FIG. FIG. 5b is a side view of the green compact shown in FIG. 5a. 5b is a front view of the green compact shown in FIG. 5a. FIG. FIG. 6 schematically shows a compression molding process of the green compact shown in FIG. 5 and is a cross-sectional view of a compression molding die. FIG. 6B is a cross-sectional view taken along line YY in FIG. 6A. FIG. 6B is a cross-sectional view taken along line X1-X1 in FIG. 6a. FIG. 6B is a cross-sectional view taken along line X2-X2 in FIG. 6a. It is sectional drawing which shows typically the mode of mold release of a green compact. It is an enlarged photograph of the lower surface of a green compact. It is an enlarged photograph of the side of a green compact. It is sectional drawing which shows the sizing process of a sintered compact typically. It is sectional drawing which shows the sizing process of a sintered compact typically. It is an enlarged photograph of the lower surface of an oil seal member. It is an enlarged photograph of the side of an oil seal member. It is a top view of the oil seal member concerning other embodiments of the present invention. It is a side view of the oil seal member shown in Drawing 12a. It is a front view of the oil seal member shown in Drawing 12a. It is sectional drawing which shows typically the sizing process of the sintered compact processed into the oil seal member shown in FIG. It is an axis orthogonal sectional view of a publicly known variable valve timing mechanism. FIG. 14B is a cross-sectional view taken along line XX in FIG. 14A. FIG. 14B is a cross-sectional view taken along line YY in FIG. 14A. FIG. 14B is an enlarged side view of the oil seal member shown in FIG. 14B. It is a front view of the oil seal member shown in FIG. 14b. It is a schematic sectional drawing which shows the stage which filling of material powder completed in the compression molding process among the manufacturing processes of the conventional oil seal member. It is a schematic sectional drawing which shows the compression step of material powder in a compression molding process among the manufacturing processes of the conventional oil seal member. It is a schematic sectional drawing which shows the step by which the green compact was discharged | emitted from the die | dye in the compression molding process among the manufacturing processes of the conventional oil seal member. It is sectional drawing when seeing FIG. 16b from another direction. It is sectional drawing of another compression molding die. It is sectional drawing of another compression molding die. It is sectional drawing when the compression molding die shown in FIG. 19 is seen from the other direction. FIG. 20 is a cross-sectional view of the green compact in the compression mold shown in FIG. 19 as viewed from the other direction when discharged from the die. It is the surface enlarged photograph of the metal sintered compact to which the grinding process was given. It is the surface enlarged photograph of the metal sintered compact to which the turning process was given.

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

FIGS. 1a, 1b and 1c show a plan view, a side view and a front view of an oil seal member 1 according to an embodiment of the present invention, respectively. The oil seal member 1 shown in the figure is attached to an axially extending groove 105 provided in the vane 102 of the rotor 101 among the rotor 101 and the housing 103 that constitute the variable valve timing mechanism 100 shown in FIG. The hydraulic chamber 106 formed between the rotor 101 and the housing 103 is liquid-tightly partitioned with a sliding contact with the inner diameter surface of the housing.

The oil seal member 1 has the same shape as the oil seal member 120 shown in FIG. That is, the oil seal member 1 has a thin plate shape extending in the axial direction of the rotor 101 (hereinafter also referred to as “longitudinal direction”), and the rotational direction of the rotor 101 (hereinafter referred to as “short direction”). And a pair of

parallel side surfaces

4 and 4 facing each other, and a circumferential surface composed of a plurality of surfaces that circulate between both

side surfaces

4 and 4. The circumferential surface faces the lower surface 3 and the lower surface 3 constituting the sliding surface with the inner diameter surface of the housing 103 in the radial direction of the rotor 101 (provided on the opposite side of the lower surface 3 and faces the groove bottom surface of the groove portion 105. ) A pair of

parallel end surfaces

5, 5 connecting the upper surface 2 and the lower surface 3 on both sides in the longitudinal direction of the upper surface 2, the lower surface 3, and a pair of

inclined surfaces

6, 6 provided at the boundary between the upper surface 2 and each end surface 5. Composed.

The oil seal member 1 includes a pair of thick portions A and A having a relatively large separation distance (thickness) between the upper and lower surfaces provided at both ends in the longitudinal direction, and the upper and lower surfaces provided at the central portion in the longitudinal direction. A thin spring portion B having a relatively small separation distance is integrally formed, and a leaf spring 130 (see FIG. 14) as an urging member is fixed in a curved state between the pair of thick portions A and A. It has become. And the thickness _{d 1} of the thick portion A, the ratio of the thickness _{d 2} of the thin portion B ₍₌ d 2 / _{d 1)} is in the range of 0.4 or more and less than 0.7, more preferably 0.5 It is set within the range of 0.6 or less (the reason will be described later). The total length L of the oil seal member 1 is about 15 to 30 mm, and the ratio (= L / d ₁ ) between the total length L and the thickness d ₁ of the thick portion A is in the range of 5 to 10. More preferably, it is in the range of 6-8.

At both ends in the longitudinal direction of the upper surface 2,

convex portions

2a and 2a constituting the thick portions A and A are provided. In other words, the upper surface 2 has a concavo-convex shape in the longitudinal direction, with both end portions in the longitudinal direction being a high surface and the central portion in the longitudinal direction being a low surface.

As shown in FIG. 1c, the lower surface 3 constituting the sliding surface is a convex curved surface curved in an arc shape in the short direction, more specifically, the central portion in the short direction is the apex (the central portion in the short direction is It is formed in a convex curved surface shape that bulges in the direction of increasing the distance from the upper surface 2. As shown in FIG. 2, the lower surface 3 is slidably in contact with the inner surface of the housing 103, and oil leaks from the hydraulic chamber 106 (oil flows between the

hydraulic chambers

106 and 106 adjacent in the circumferential direction. ) Functions as a sealing surface to prevent as much as possible. Therefore, from the viewpoint of preventing oil leakage and appropriately increasing the pressure in the hydraulic chamber 106, it is ideal that the curvature of the lower surface 3 and the curvature of the inner diameter surface of the housing 103 are made to completely coincide with each other, and both surfaces are brought into surface contact. However, it is extremely difficult to make the curvatures of both sides completely coincide.

Therefore, as shown in FIG. 2, the curvature of the lower surface 3 of the oil seal member 1 is made slightly larger than the curvature of the inner diameter surface of the housing 103 so that both surfaces can be contacted in a line contact state close to surface contact. As a result, when the oil seal member 1 is attached to the groove portion 106 of the rotor 101, the short-side central portion 3a of the lower surface 3 is in line contact with the inner diameter surface of the housing 103, and the lower surface 3 on both circumferential sides of the contact portion P of both. (Both ends 3b in the short direction) and the inner surface of the housing 103 are opposed to each other with a radial gap Q therebetween. By setting the curvature of the lower surface 3 and the curvature of the inner diameter surface of the housing 103 as described above, the radial gap Q has a wedge shape in which the gap width is gradually reduced toward the contact portion P.

The oil seal member 1 is made of sintered metal, and in particular, a sintered metal material for a bearing containing a solid lubricant N (a material powder in which a metal powder M is a main raw material and at least a solid lubricant N is added). Is formed into the above shape by compacting and sintering. Further, as shown in FIG. 3, the oil seal member 1 is a solid solution of the metal powder M and the solid lubricant N (the metal powder M and the solid lubricant N are not compounded, and the original shape is maintained to some extent. The crystal structure is mainly composed of (bonded).

As sintered metal materials for bearings, those specified in Appendix 1 of JIS Z2550 are used. Among them, pure iron (P1011Z, P1012Z, P1013Z), iron-copper (P2011Z, P2012Z, P2013Z) are used. , And iron-carbon-graphite systems (P1053Z, P1054Z) can be preferably used. Further, as the solid lubricant N, graphite, molybdenum disulfide, boron nitride, tungsten disulfide, polytetrafluoroethylene, and the like can be used. As described above, the oil seal member 1 includes the metal powder M and the solid lubricant. In view of having a crystal structure mainly composed of a solid solution of N, graphite is particularly preferably used. The material powder includes fillers other than the solid lubricant N, such as glass fiber, pitch-based carbon fiber, PAN-based carbon fiber, aramid fiber, alumina fiber, etc. that have an effect of improving wear resistance and heat resistance. It can also be included.

Both

side surfaces

4 and 4 and the circumferential surface (outer surface whole area) of the oil seal member 1 are formed surfaces, and particularly in this embodiment, the entire outer surface area of the oil seal member 1 is as shown in FIG. A molding surface having a sliding mark S formed along with sliding with the molding die is formed (FIG. 3 schematically shows a part of the lower surface 3 of the oil seal member 1). In other words, the oil seal member 1 is so-called clogged by sliding the entire outer surface of the oil seal member 1 with a molding die used in a compression molding process or a sizing process, which is an essential process for obtaining a metal sintered body having a predetermined shape. The plastic working surface is subjected to the processing (sealing processing). As a result, the surface area ratio of each surface of the oil seal member 1 is set to 5 to 40%. The lower surface 3 of the oil seal member 1 forms a contact portion P and a radial gap Q between the inner surface of the housing 103 and the surface opening ratio is the surface of the outer surface because of the surface to which the highest hydraulic pressure is applied. Among them, it is set to the smallest value, for example, within a range of 5 to 30%. However, in the lower surface 3, the surface aperture ratios of the lateral

direction end portions

3 b and 3 b are smaller than the surface aperture ratio of the lateral direction central portion 3 a. This is because, as will be described later, the lower surface 23 of the sintered body 20 having a flat surface shape is formed (compressed) into a convex curved surface shape by sizing. Further, the surface open area ratio of the pair of

side surfaces

4 and 4 that are formed in flat surfaces parallel to each other and face the hydraulic chamber 106 is, for example, in the range of 20 to 40%.

As shown in FIG. 4, the oil seal member 1 having the above configuration includes a compression molding process for obtaining a green compact 10 by compression molding a sintered metal material (material powder) containing a solid lubricant N, and a green compact. It is manufactured through a sintering process in which the body 10 is sintered to obtain the sintered body 20 and a sizing process in which the sintered body 20 is compressed into a final shape.

In the compression molding process, the green compact 10 having a shape approximate to the oil seal member 1 as a finished product is formed. Specifically, as shown in FIGS. 5a to 5c, each of the pair of side surfaces 14 and 14 parallel to each other and a plurality of circumferential surfaces that circulate between both side surfaces 14 and 14 are provided. The upper surface 12 having an uneven shape, the lower surface 13 provided on the opposite side of the upper surface 12, a pair of parallel end surfaces 15 and 15 connecting the upper surface 12 and the lower surface 13 on both longitudinal sides of the lower surface 13, and the upper surface 12 and each end surface The green compact 10 composed of the

inclined surfaces

16 and 16 provided at the boundary portion 15 is formed. However, as shown in FIG. 5 c, the lower surface 13 of the green compact 10 is not a convex curved surface curved in the lateral direction, but the entire region thereof is formed on a flat surface parallel to the upper surface 12.

Such a green compact 10 is compression molded using a first molding die 30 having a die 31, an upper punch 32 and a lower punch 33, as shown in FIG. 6a. Specifically, after filling the above material powder into a cavity defined by the forming hole 31a of the die 31 and the pressing surface 33a of the lower punch 33 disposed on the inner periphery of the die 31, the upper punch 32 is lowered. Thus, the material powder is compressed to form the green compact 10. In the first molding die 30, both side surfaces 14 and 14 of the green compact 10 are formed by the pressure surface 32 a of the upper punch 32 and the pressure surface 33 a of the lower punch 33 (see FIG. 6 a). The circumferential surface (upper surface 12, lower surface 13, end surface 15 and inclined surface 16) of the green compact 10 is molded in the molding hole 31a (see FIG. 6b). The inner wall surface constituting the forming hole 31a of the die 31 is a flat surface parallel to the compression direction (the moving direction of the upper and lower punches 32 and 33). Therefore, the peripheral surface formed by the forming hole 31 a of the die 31 in the green compact 10 is formed into a flat surface parallel to the compression direction of the green compact 10.

When the upper punch 32 reaches the lowering limit and the compacting of the green compact 10 is completed, the upper punch 32 and the lower punch 33 are lifted together with the compact 10 as shown in FIG. The green compact 10 is discharged, and then the green compact 10 is discharged in the horizontal direction. The discharged green compact 10 is transferred to the sintering process which is the next process. As described above, since the inner wall surface constituting the molding hole 31a of the die 31 is a flat surface parallel to the compression direction, the die 31 is discharged in the process of discharging the green compact 10 from the molding hole 31a of the die 31. And the green compact 10 do not engage in the pulling direction. In addition, since the pressing surface 33a of the lower punch 33 is a surface that forms the flat side surface 14 without unevenness, when the green compact 10 is discharged, the lower punch 33 and the green compact 10 are engaged in the discharging direction. Never do. Therefore, when the green compact 10 is discharged, a situation in which the green compact 10 is deformed is prevented. Further, since the green compact 10 is molded by compressing the material powder to which the solid lubricant N is added, it is smoothly discharged from the molding hole 31a of the die 31.

On the outer surface of the green compact 10, as the downward movement of the upper punch 32 (relative movement of the upper punch 32 and the lower punch 33) progresses, the pressing surface 32 a of the upper punch 32 and the lower punch 33 The pressure surface 33a and the molding hole 31a of the die 31 are molded, and among these, the circumferential surface of the green compact 10 is molded with sliding with the inner wall surface of the molding hole 31a of the die 31. For this reason, the metal powder M and the solid lubricant N constituting the circumferential surface of the green compact 10 are formed with a sliding mark S (see FIG. 3) due to sliding with the inner wall surface of the molding hole 31a of the die 31. As a result, the surface opening of the circumferential surface of the green compact 10 is crushed. In the green compact 10, both side surfaces 14 and 14 formed by the upper and

lower punches

32 and 33 are also crushed by receiving the compressive force from the

pressing surfaces

32 a and 33 a, but the amount of crushed is the upper and lower punches. The circumferential surface formed by sliding with the molding hole 31a of the die 31 is larger than the both side surfaces 14, 14 formed by being pressed by the

pressures

32, 33. Therefore, in the green compact 10, the surface area ratio of the upper surface 12, the lower surface 13, the end surface 15, and the inclined surface 16 is smaller than the surface area ratio of the side surface 14. This is shown in FIGS. 8a and 8b. FIG. 8 a shows an enlarged photograph of the lower surface 13 of the green compact 10 formed by the forming hole 31 a of the die 31, and FIG. 8 b shows an enlarged view of the side surface 14 of the green compact 10 formed by the pressing surface of the punch. A photograph is shown.

Further, as described above, by forming the both side surfaces 14 and 14 of the green compact 10 with the upper punch 32 and the lower punch 33, the pressure in any of the cross sections in the compression direction shown in FIGS. 6a, 6c and 6d. The thickness of the powder 10 in the compression direction is constant. Therefore, the compression ratio of the green compact 10 is uniform throughout the entire area, and the green compact 10 having a uniform density is obtained. As a result, a problem caused by the existence of a density difference in each part of the green compact 10, for example, a situation in which the green compact 10 is damaged when the green compact 10 is transferred to the sintering process occurs. Can be prevented as much as possible.

Further, if the pair of side surfaces 14 and 14 of the green compact 10 are formed by the upper punch 32 and the lower punch 33, the green compact 10 having a large step on the upper surface 12 can be formed. Thereby, the thickness difference of the thick part A of the oil seal member 1 and the thin part B can be enlarged, and the attachment property of the leaf | plate spring 130 with respect to the oil seal member 1 improves.

Here, as described above, by using a conventional method for manufacturing an oil seal member (see FIG. 16 and the like), the green compact 10 in which the thickness between the upper and lower surfaces is different between the longitudinal end portion and the longitudinal central portion. If it shape | molds, a compression rate will differ greatly by the thick part and thin part of the compact 10. As a result of verification by the inventor of the present application, as shown in Table 1 below, the separation distance (thickness of the thick portion A) d ₁ between the upper and lower surfaces constituting the thick portion A of the oil seal member ₁ and the thin portion When the ratio (= d ₂ / d ₁ ) of the separation distance between the upper and lower surfaces constituting B (thickness of the thin portion B) d ₂ (= d ₂ / d ₁ ) is less than 0.7, the compression ratio of the thick portion A is not good. It became clear that the strength of the thick part A could not be ensured, and it was difficult to mold the green compact 10 itself. If the ratio d ₂ / d ₁ is 0.7 or more and less than 0.75, the conventional method can be used for molding, but the strength of the thick portion of the green compact 10 becomes insufficient and cracks occur. Or chipping easily occurs.

On the other hand, according to the manufacturing method according to the present invention described above, since the density of the green compact 10 in the longitudinal direction can be made uniform, the ratio d ₂ / d _{1 is set} to 0.7 as shown in Table 1. Even if it is less than 0.6, or even less than 0.6, the strength required for the thick portion A of the oil seal member 1 can be ensured. However, when the thickness difference between the thick part A and the thin part B is further increased (the ratio d ₂ / d ₁ is less than 0.4), the upper and lower punches 32 constituting the molding die of the green compact 10. , 33 partially lacks the strength, it was concluded that the molding was practically impossible. Further, when the ratio d ₂ / d ₁ is less than 0.5, cracks and chips are likely to occur in the convex portion. Accordingly, the lower limit value of the ratio d ₂ / d ₁ is 0.4 or more, preferably 0.5 or more. From the above, the thickness _{d 1} of the thick portion A of the oil seal member 1, the ratio _d 2 / _{d 1} between the thickness _{d 2} of the thin portion B is 0.4 or more and less than 0.7, preferably It is desirable to set it to 0.5 or more and less than 0.7. Thereby, the oil seal member 1 excellent in the moldability and strength of the green compact 10 and the attachment property of the leaf spring 130 as the urging member can be obtained.

In the sintering process, the green compact 10 is heated at a predetermined temperature for a predetermined time, thereby bonding (sintering) the metal powders M constituting the green compact 10, and further the metal powder M and the solid lubricant N. The sintered body 20 is obtained. Since the sintered body 20 has substantially the same shape as the green compact 10, detailed description thereof is omitted.

As the sintered body 20, by adjusting the heating temperature and heating time of the green compact 10, (1) one having a structure composed mainly of a compound of metal powder M and solid lubricant N, or (2 ) Having a crystal structure mainly composed of a solid solution of metal powder M and solid lubricant N. In the present invention, (2) a crystal mainly composed of a solid solution of metal powder M and solid lubricant N A sintered body 20 having a structure is obtained. This is because the solid lubricant N remains with its original shape remaining to some extent, which is advantageous in obtaining a final product (oil seal member 1) having excellent sliding characteristics. In general, the heating temperature required to obtain the configuration (2) is lower than the heating temperature required to obtain the configuration (1), and the heating time required is also as follows. short. Therefore, if the configuration of (2) is obtained, the amount of dimensional change associated with sintering can be reduced, which is advantageous in obtaining a highly accurate sintered body 20 and thus the oil seal member 1. . Moreover, as described above, since the green compact 10 to be heated has a uniform density throughout the entire area, the amount of dimensional change associated with sintering is that of the green compact 10 (sintered body 20). It becomes almost equal in each part. Therefore, higher accuracy of the sintered body 20, and hence the oil seal member 1 is achieved.

The sintered body 20 obtained in the sintering process is transferred to the sizing process. In the sizing process, the second molding die 40 including the die 41, the upper punch 42, and the lower punch 43 shown in FIG. 9 is used, and the sintered body 20 is different from the compression direction of the green compact 10 in the compression molding process. , The sintered body 20 is finished into a final shape.

In the sizing process, the upper surface 22 and the lower surface 23 (indicated by dotted lines in FIG. 9) of the sintered body 20 disposed on the inner periphery of the forming hole 41 a of the die 41 are added to the pressurizing surface 42 a of the upper punch 42 and the lower punch 43. Each is compressed by the pressure surface 43a. The pressure surface 43 a of the lower punch 43 is formed in a shape in which the shape of the lower surface 3 of the oil seal member 1 is inverted, that is, a concave curved surface shape in which the center portion in the short direction bulges away from the upper punch 42. . Therefore, when the lower surface 23 of the sintered body 20 is compressed by the pressing surface 43a of the lower punch 43, the lower surface 23 of the sintered body 20 is formed into a convex curved surface. At the same time, the other surface of the sintered body 20 is finished to a final shape.

By the way, as described above, when the lower surface 23 of the sintered body 20 is formed into a convex curved shape by sizing, the deformation amount of the lower surface 23 due to sizing becomes larger than the deformation amount of the upper surface 22, and thus the forming hole 41 a of the die 41. The sintered body 20 discharged from the substrate tends to warp in the longitudinal direction. The lower surface 3 of the oil seal member 1 is a surface that also functions as a seal surface that liquid-tightly partitions the hydraulic chamber 106 with sliding contact with the inner diameter surface of the housing 103, so that its busbar is possible. It is necessary to form it so that it may become linear form.

Therefore, in the second molding die 40 that executes sizing, the pressurizing surface 43a of the lower punch 43 that molds the lower surface 23 of the sintered body 20 into a convex curved surface is exaggerated in FIG. The central portion is formed in a circular arc shape bulging in a direction approaching the upper punch 42. In this way, the warp generated in the sintered body 20 due to the spring back is offset, so the bus bar of the lower surface 23 (the lower surface 3 of the oil seal member 1) of the sintered body 20 discharged from the second molding die 40. Can be straight in the longitudinal direction. Thereby, favorable sealing performance is ensured.

Also in this sizing process, as the downward movement of the upper punch 42 progresses, each surface of the sintered body 20 is divided into the pressing surface 42a of the upper punch 42, the pressing surface 43a of the lower punch 43, and the molding hole 41a of the die 41. Among them, both side surfaces 24, 24 of the sintered body 20 are formed (shaped) with sliding with the inner wall surface of the forming hole 41a of the die 41. Therefore, in the metal powder M and the solid lubricant N constituting the both side surfaces 24, 24 of the sintered body 20, a sliding trace is newly formed due to sliding with the inner wall surface of the molding hole 41a of the die 41. In this way, the crushing process is performed, and the surface area ratio is further reduced. As described above, the amount of crushing is such that sliding marks are formed on the surface formed by sliding with the inner wall surface of the die forming hole rather than the surface formed by pressurization. It will be more. Therefore, the effect of reducing the surface area ratio in the sizing step is that the side surfaces 24 and 24 of the sintered body 20 formed by the inner wall surface of the forming hole 41a of the die 41 are pressed surfaces of the upper and

lower punches

42 and 43. It becomes larger than the surrounding surface of the sintered compact 20 shape | molded by 42a, 43a.

In the present invention, the compression direction of the green compact 10 by the upper and

lower punches

32 and 33 used in the compression molding process is different from the compression direction of the sintered body 20 by the upper and

lower punches

42 and 43 used in the sizing process. The entire surface of the outer surface of the oil seal member 1 is uniformly formed with sliding traces associated with sliding with the molding die, and the entire surface of the outer surface is formed with a sufficiently small surface opening ratio (plastic working surface). ) This is shown in FIGS. 11a and 11b. 11a shows the lower surface 3 of the oil seal member 1 formed by the pressurizing surface 43a of the lower punch 43, and FIG. 11b shows the side surface 4 of the oil seal member 1 formed by the forming hole 41a of the die 41. ing.

However, because the lower surface 23 of the sintered body 20 is formed into a convex curved surface in the sizing process, the lower surface 23 has the largest amount of deformation (compression ratio) of each surface of the sintered body 20 due to sizing. Thereby, the lower surface 2 has the smallest surface opening rate of the oil seal member 1 completed by being discharged from the second molding die 40. In particular, both ends of the lower surface 2 in the short direction are portions where the surface opening ratio is the smallest in the oil seal member 1 because the amount of deformation due to sizing is larger than that in the central portion in the short direction.

The sizing of the sintered body 20 can also be performed in a state in which the sintered body 20 and both punches are inverted with respect to the configuration shown in FIG. In this case, the upper surface 22 of the sintered body 20 discharged from the molding hole 41a of the die 41 and the pressing surface 42a of the lower punch 42 are engaged in the paying-out direction (horizontal direction). The body 20 has higher strength than the green compact 10. Therefore, even if air injection or the like is performed, the engagement state between the sintered body 20 and the pressure surface 42a of the lower punch 42 can be easily eliminated without damaging the sintered body 20.

As described above, the oil seal member 1 made of sintered metal according to the present invention has a pair of

side surfaces

4 and 4 parallel to each other and a circumferential surface composed of a plurality of surfaces that circulate between both

side surfaces

4 and 4. Are all formed surfaces. In other words, the entire outer surface is compressed by a molding die used in the manufacturing process of the oil seal member 1 and deforms following the cavity of the die, so that a so-called crushing process is performed. Means that. Therefore, among the surfaces constituting the oil seal member 1, the surface porosity of the lower surface 3 that is a sliding surface that slides on the housing 103 and the both

side surfaces

4 and 4 that are always in contact with oil is determined by It can be appropriately reduced without any processing or the like. Furthermore, in the present invention, both the side surfaces 4 and 4 and the circumferential surface of the oil seal member 1 are all formed molds for forming the oil seal member 1 made of sintered metal (the die 31 and the sizing used in the compression molding process). Since it is crushed by sliding with the die 41) used in the process, the surface area ratio of the entire outer surface of the oil seal member 1 can be further reduced. Accordingly, it is possible to mass-produce the sintered metal oil seal member 1 that has a high effect of suppressing the intrusion of oil and is excellent in wear resistance at a low cost without causing a particular increase in cost. The sintered metal obtained by using the sintered metal material for bearings has a lower density than that obtained by using the sintered metal material for structural parts. There is a demerit that it is difficult to suppress internal penetration and improve wear resistance. In contrast, the above-described configuration of the present invention improves the disadvantages of using a sintered metal material for bearings, so that the oil seal member 1 manufactured using the sintered metal material for bearings has a variable valve timing. It can be suitably used as an oil seal member for a mechanism.

Moreover, in this embodiment, since the lower surface 3 of the oil seal member 1 was formed into a convex curved surface by sizing, the surface area ratio of the lower surface 3 is the smallest among the surfaces constituting the oil seal member 1. . The lower surface 3 of the oil seal member 1 constitutes a sliding surface that slides with the inner diameter surface of the housing 102, and is the surface on which the highest hydraulic pressure acts on the oil seal member 1. If the porosity is small, it is difficult for oil to enter the oil seal member 1 via the lower surface 3, and the oil seal member 1 can be stably attached to the sliding portion between the lower surface 3 of the oil seal member 1 and the inner diameter surface of the housing 102. An oil film can be formed. Accordingly, the response of rotation of the rotor 101 can be improved.

In the above, the present invention is applied to the oil seal member 1 that is attached to the groove portion 105 provided on the outer diameter surface of the rotor 101 and partitions the hydraulic chamber 106 in a liquid-tight manner with sliding with the inner diameter surface of the housing 103. As described above, the present invention is attached to the groove portion 105 provided on the inner diameter surface of the housing 103, and the lower surface 3 makes the hydraulic chamber 106 fluid-tight with sliding with the outer diameter surface of the rotor 101. The present invention can also be preferably applied to an oil seal member partitioned into two. In this case, the lower surface 3 of the oil seal member 1 may be formed into a convex curved surface shape in which the central portion in the short direction is bulged away from the upper surface 2, as in the above-described embodiment, On the contrary, as shown in FIGS. 12a to 12c, the central part in the short direction may be formed into a concave curved surface bulged in a direction approaching the upper surface 2.

The oil seal member 1 shown in FIG. 12 differs from the oil seal member 1 shown in FIG. 1 in the curved form of the lower surface 3 and the size relationship of the surface open area ratio in the short direction of the lower surface 3. That is, the oil seal member 1 shown in FIG. 12 is finished to a final shape by sizing the sintered body 20 using a second molding die 40 as shown in FIG.

More specifically, in the second molding die 40 for molding the oil seal member 1 shown in FIG. 12, the pressing surface 43a of the lower punch 43 approaches the upper punch 42 in the center in the short direction as shown in FIG. It is formed in a convex curved shape that bulges in the direction (upward). In this case, the flat lower surface 23 of the sintered body 20 is compressed by the pressing surface 43a of the lower punch 43, so that the lower surface 23 of the sintered body 20 is formed into a concave curved surface. At this time, since the amount of compression at the center portion in the short direction of the lower surface 23 is larger than the amount of compression at both ends in the short direction, the lower surface 23 (oil seal member 1) of the sintered body 20 formed into a concave curved surface shape. The surface open area ratio of the lower surface 3) is smaller at the center in the short direction than at both ends in the short direction. Accordingly, oil can be retained between the center portion in the short direction of the lower surface 3 of the oil seal member 1 and the outer diameter surface of the rotor 101, and the lubricity is improved. Further, in this case, the lower surface 3 of the oil seal member 1 has a relatively high density in the central portion in the short direction rather than both ends in the short direction. The strength of the central portion in the short direction, which is mainly in sliding contact with the radial surface, is increased, and the wear resistance is improved.

As described above with reference to FIG. 14, the variable valve timing mechanism 100 described above includes the groove portion 105 provided at the center in the circumferential direction of the outer diameter surface of each vane 102 of the rotor 101, and each tooth of the housing 103. The oil seal member is attached to the groove portion 105 provided in the center portion in the circumferential direction of the inner diameter surface of the 104. The groove portion 105 for attaching the oil seal member is provided on the outer diameter surface of the vane 102 or the inner diameter surface of the tooth 104. The oil seal member 1 according to the present invention can also be preferably used in the variable valve timing mechanism 100 provided at the offset position in the circumferential direction from the circumferential center.

In the variable valve timing mechanism 100 described above, the groove portion 105 is provided on the outer diameter surface of the vane 102 and the inner diameter surface of the tooth 104, but the inner diameter of the housing 103 facing the outer diameter surface of the vane 102. The variable valve timing mechanism 100 configured such that the groove portion 105 is provided on the outer diameter surface of the rotor 101 facing the inner surface of the surface and the teeth 104 and the oil seal member 1 is attached to the groove portion 105 is also included in the present invention. The oil seal member 1 according to the above can be preferably used.

1 Oil seal member 2 Upper surface 2a Convex portion 3 Lower surface (sliding surface)
4 Side surface 5 End surface 10 Compact 20 Sintered body 30 First molding die 40 Second molding die 100 Variable valve timing mechanism 101 Rotor 103 Housing 106 Hydraulic chamber 130 Leaf spring (biasing member)
A Thick part B Thin part M Metal powder N Solid lubricant P Contact part Q Radial gap

Claims

An oil seal member made of sintered metal that liquid-tightly partitions a hydraulic chamber formed between a rotor and a housing constituting a variable valve timing mechanism,
Formed of sintered metal material for bearings,
A pair of side surfaces facing each other in the rotational direction of the rotor and a plurality of surfaces that circulate between both side surfaces, one of which is a sliding surface that slides on either the outer diameter surface of the rotor or the inner diameter surface of the housing. An oil seal member comprising: a circumferential surface to be configured; and the pair of side surfaces and the circumferential surface are both molded surfaces.
2. The oil seal member according to claim 1, wherein the pair of side surfaces and the circumferential surface are both crushed by sliding with a molding die.
The sintered metal material contains a solid lubricant,
The oil seal member according to claim 1, which has a crystal structure mainly composed of a solid solution of metal powder and a solid lubricant.
2. The oil seal member according to claim 1, wherein the surface area ratio of the pair of side surfaces and the circumferential surface is 5% or more and 40% or less.
The sliding surface has a curved surface curved in the rotational direction of the rotor, and a surface of the circumferential surface that faces the sliding surface in the radial direction of the rotor is uneven in the axial direction of the rotor. Oil seal member.
The oil seal member according to claim 5, wherein the sliding surface has a convex curved surface.
The oil seal member according to claim 6, wherein the surface aperture ratio at both ends of the rotor in the rotational direction of the sliding surface is smaller than the surface aperture ratio at the apex of the sliding surface.
The oil seal member according to claim 5, wherein the sliding surface has a concave curved surface.
The oil seal member according to claim 8, wherein the surface opening ratio at the apex of the sliding surface is smaller than the surface opening ratio at both ends in the rotational direction of the rotor of the sliding surface.
A variable valve timing comprising: the oil seal member according to any one of claims 1 to 9; a rotor having an oil seal member mounting groove; and a housing that rotatably mounts the rotor. mechanism.
An oil seal member made of sintered metal that liquid-tightly partitions a hydraulic chamber formed between a rotor and a housing constituting a variable valve timing mechanism, a pair of side surfaces facing each other in the rotational direction of the rotor, and both sides In the manufacturing method of what comprises a plurality of surfaces that circulate between the surfaces, one of which comprises a circumferential surface that constitutes a sliding surface that slides with either the outer diameter surface of the rotor or the inner diameter surface of the housing,
A compression molding process to obtain a green compact by compressing a sintered metal material for a bearing, a sintering process to obtain a sintered body by sintering the green compact, and a sintered body to be compressed into a final shape A sizing process to finish,
A method for producing an oil seal member, wherein a compression direction of a green compact by a pair of punches used in a compression molding step and a compression direction of a sintered body by a pair of punches used in a sizing step are made different.
The oil seal member has a curved surface in which the sliding surface is curved in the rotation direction of the rotor, and the surface of the circumferential surface that faces the sliding surface in the radial direction of the rotor is uneven in the axial direction of the rotor. Is,
The method for producing an oil seal member according to claim 11, wherein a circumferential surface of the green compact is formed by a die used in the compression molding step, and both side surfaces of the sintered body are formed by a die used in the sizing step.
The method for producing an oil seal member according to claim 12, wherein the sliding surface is formed into a curved surface curved in the rotational direction of the rotor by a punch used in the sizing step.