JP2010096249A - Fastening structure of two members and fluid filter using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fastening structure of two members capable of preventing the loosening of screwing even if used at a high temperature after the two members having different coefficients of thermal expansion are assembled by screwing and capable of always maintaining a strong fastening state, and to provide a fluid filter using the structure. <P>SOLUTION: A member 20 having a higher thermal expansion coefficient of the two members includes a male screw 20b and a member 30 having a lower thermal expansion coefficient includes a female screw 30b formed to have a shorter pitch than the male screw. When used in a high temperature environment after fastening the two members by screwing at an ordinary temperature, since a forward side flank surface A of the male screw and an anti-forward side flank surface C of the female screw are press-fit at a tip side of a male screw and an anti-forward side flank surface B of the male screw and a forward side flank surface D of the female screw are press-fit at a root side of the male screw by a difference of the thermal expansion coefficients of the two members, the fastening of the two members is not loosened. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a two-member fastening structure for fastening two members having different coefficients of thermal expansion by screwing by relative rotation of screws provided on each member, and a fluid filter using the same. Specifically, it is possible to prevent the fastening by screwing of screws provided on two members having different coefficients of thermal expansion such that one member is a metal and the other member is a synthetic resin from being loosened at a high temperature 2. The present invention relates to a member fastening structure and a fluid filter using the same.

  Conventionally, in a fluid filter (for example, an oil filter) or the like, two members having different coefficients of thermal expansion are assembled by being screwed together, such as forming a casing by screwing together a base and a cap that are made of different materials. . As shown in FIG. 7, an oil filter 1 having a conventional casing 4 is made of a synthetic resin and a bottomed cylindrical cap 2 and a base 3 made of aluminum alloy that can be screwed together by relative rotation. It has. On the outer peripheral surface of the cap 2, a screwing portion 2 a made up of a male screw portion 2 b is formed, and an O-ring 5 is attached. Further, a threaded portion 3 a made up of a female screw portion 3 b is formed on the inner peripheral surface of the base 3. When the screwed portion 2a and the screwed portion 3a are screwed and the cap 2 and the base 3 are screwed via the O-ring 5, the inside of the casing 4 is held in a liquid-tight manner. .

  In addition, an oil passage pipe portion 9 that discharges oil inside the casing 4 and an inflow port 10 through which oil flows into the casing 4 are provided at the bottom of the base 3. A cylindrical protector 13 having a large number of through holes 6 is provided inside the cap 2, and a filter element 11 is attached to the outer periphery of the protector 13. A support spring 7 made of a coil spring that urges the protector 13 toward the base 3 is provided on the upper portion of the spring receiving portion 14 of the protector 13.

  In the oil filter 1 configured as described above, the casing 4 generally has a male screw portion 2b of the screwed portion 2a of the cap 2 screwed into a female screw portion 3b of the screwed portion 3a of the base 3 at room temperature. Can be assembled together. After the assembly, the screwed portion 3a of the base 3 is sandwiched between the flange 2d of the cap 2 with which the end surface 3e of the tip portion of the base 3 abuts and the screwed portion 2a of the cap 2 as shown in FIG. As a result, an axial force P that is an axial compression force is generated. Thereby, the cap 2 and the base 3 are fastened by being firmly fastened.

Next, focusing on the threaded portion, an example in which a dimensional difference is formed between the pitch of the female screw and the pitch of the male screw in order to prevent loosening of the screw has been disclosed (see Patent Document 1).
In the above conventional example, when the male screw is screwed into the female screw and tightened slightly, the leading flank surface of the female screw thread comes into contact with the leading flank surface of the male screw thread, and due to the difference in pitch, the female thread The non-advanced flank surface of the other screw thread is pressed against the anti-advanced flank surface of the other screw thread. This prevents loosening and return between the female screw and the male screw.

  In another conventional example, a dimensional difference is formed between the thread of the male screw and the thread of the female screw, and a screw configured by making the thread of the male screw thin is disclosed (see Patent Document 2). reference). The pitch of the female screw is equal, the virtual pitch of the male screw (the pitch of the male screw when the thread of the male screw is not thinned) is the same as the pitch of the female screw, and the anti-advanced flank surface of the male screw and the female screw are opposite to each other. The screw thread of the male screw is made thin so that the gap with the advancing-side flank surface gradually increases from the tip of the male screw toward the mouth, thereby achieving strong tightening.

JP-A-8-135543 JP 2000-227109 A

  However, depending on the conventional fastening structure using a screw that prevents the looseness by forming a dimensional difference between the thread pitch of the male screw and the pitch of the female screw, the screw is attached to two members having different thermal expansion coefficients. When the two members are relatively rotated and fastened by screwing, there is a problem that the tightening is loosened when used in a high temperature state even if it is firmly tightened during assembly. That is, there is a problem in that when two members formed of materials having different thermal expansion coefficients of male and female screws are assembled at room temperature, and when used at a high temperature, the fastening is loosened due to the difference in the thermal expansion coefficient of the two members. Arise.

  Further, as shown in FIG. 7, the conventional oil filter 1 is assembled by screwing the male screw portion 2 b of the screwing portion 2 a of the cap 2 to the female screw portion 3 b of the screwed portion 3 a of the base 3. After the assembly, the screwed portion 3a of the base 3 is sandwiched between the flange 2d of the cap 2 with which the end surface 3e of the tip portion of the base 3 abuts and the screwed portion 2a of the cap 2 as shown in FIG. As a result, an axial force P that is an axial compression force is generated. Thereby, the cap 2 and the base 3 are fastened by being firmly fastened.

  However, since the conventional oil filter 1 becomes high temperature when the engine is used for vehicle running or the like, the cap 2 and the base 3 are thermally expanded. As described above, when the cap 2 is made of a synthetic resin and the base 3 is made of an aluminum alloy, the cap 2 has a higher coefficient of thermal expansion than the base 3. For this reason, the screwed portion 2a formed of the male screw portion 2b of the cap 2 expands larger than the screwed portion 3a formed of the female screw portion 3b of the base 3 at a high temperature, and the tip portion of the base 3 shown in FIG. Starting from the contact position V2 between the end surface 3e of the cap 2 and the flange 2d of the cap 2, the base 3 extends in the axial direction, that is, vertically downward in FIG. As a result, the axial force P shown in FIG. 6 is lower than that during tightening, and the tightening force between the threaded portion 2a of the cap 2 and the threaded portion 3a of the base 3 tends to decrease.

  In the present invention, after two members having different coefficients of thermal expansion are assembled by screwing by relative rotation, the screwing can be prevented from loosening even when used at a higher temperature than the time of assembly. It is an object to provide a two-member fastening structure capable of maintaining a state and a fluid filter using the same.

The present invention is as follows.
1. A two-member fastening structure in which two members are fastened by screwing by relative rotation, the two members having different coefficients of thermal expansion, and a member having a large coefficient of thermal expansion is a male screw. A member having a small coefficient of thermal expansion of the two members includes a female screw formed at a pitch shorter than the pitch of the male screw, and when the two members are fastened by screwing of the male screw and the female screw, the male screw The advancing-side flank surface (A) of the male screw and the counter-advancing flank surface (C) of the female screw are in contact with each other at the leading end of the male screw, and the anti-advancing flank surface (B) of the male screw is The flank surface (A) and the flank surface (C) are brought into pressure contact when the advancing flank surface (D) of the female screw comes into contact and the member having a large coefficient of thermal expansion thermally expands in the axial direction of the screw. And Fastening structure of two members the flank (B) and said flank face (D) and is characterized in that it is pressed against the.
2. A two-member fastening structure in which two members are fastened by screwing by relative rotation, the two members having different coefficients of thermal expansion, and a member having a large coefficient of thermal expansion among the two members is a female screw. A member having a small coefficient of thermal expansion among the two members includes a male screw formed at a pitch shorter than the pitch of the female screw, and the male screw is fastened when the two members are fastened by screwing of the male screw and the female screw. The advancing flank surface (G) of the male screw and the advancing flank surface (E) of the female screw are in contact with each other at the tip end of the male screw, and the advancing flank surface (H) of the male screw and the female screw are at the root side of the male screw. The flank surface (G) and the flank surface (E) are pressed against each other when the non-advancing flank surface (F) abuts and the member having a high thermal expansion coefficient thermally expands in the axial direction of the screw. And Fastening structure of two members the flanks (H) and said flanks (F) and is characterized in that it is pressed against the.
3. One of the two members is a cap that constitutes one of the casings of a fluid filter in which a filter element is accommodated in a casing formed of a two-part body, and the other one of the two members is the above-described one 1. the base constituting the other side of the casing of the fluid filter; Or 2. The fastening structure of 2 members as described in above.
4). The member having a large coefficient of thermal expansion is made of a synthetic resin material, and the member having a small coefficient of thermal expansion is made of a metal material. Or 2. The fastening structure of 2 members as described in above.
5). The cap is made of a synthetic resin material, and the base is made of a metal material. The two-member fastening structure described.
6). A fluid filter comprising: a filter element; a protector that supports the filter element; and a cap and base that house the filter element and the protector and that can be fastened together by screwing, wherein the cap and the base are 1 above. To 5. A fluid filter comprising the two-member fastening structure according to any one of the above.

  A two-member fastening structure in which two members having different coefficients of thermal expansion are fastened by screwing by relative rotation, and a member having a large coefficient of thermal expansion among the two members includes a male screw, and thermal expansion of the two members. The member having a small ratio is provided with a female screw formed at a pitch shorter than the pitch of the male screw, so that when the two members are fastened with a predetermined tightening torque at a normal temperature, a leading side flank of the male screw is formed at the front end side of the male screw. The surface (A) and the counter-advancing flank surface (C) of the female screw are in strong contact with each other, and the counter-advancing flank surface (B) of the male screw and the advanced flank surface (D) of the female screw are provided on the base side of the male screw. Is strongly abutted, so that it is firmly fastened. When the fastened two members are used at a high temperature, the member having a large coefficient of thermal expansion is more thermally expanded in the axial direction of the screw than the member having a small coefficient of thermal expansion. A) and the flank surface (C) are further pressed together and the flank surface (B) and the flank surface (D) are further pressed together, increasing the axial force acting in the axial direction of the threaded portion. It is possible to prevent the two members from being fastened and loosened by the strength exceeding the fastening state at.

  A two-member fastening structure in which two members having different coefficients of thermal expansion are fastened by screwing by relative rotation, and a member having a large coefficient of thermal expansion among the two members includes a female screw, and thermal expansion of the two members. The member having a small ratio is provided with a male screw formed at a pitch shorter than the pitch of the female screw, so that when the two members are fastened with a predetermined tightening torque at room temperature, the male screw is on the leading side of the male screw. The flank surface (G) and the advancing flank surface (E) of the female screw are in strong contact with each other, and the advancing flank surface (H) of the male screw and the anti-advancing flank surface (F) of the female screw are provided on the base side of the male screw. Is strongly abutted, so that it is firmly fastened. When the fastened two members are used at a high temperature, the member having a large coefficient of thermal expansion is more thermally expanded in the axial direction of the screw than the member having a small coefficient of thermal expansion. G) and the flank surface (E) are further pressed and the flank surface (H) and the flank surface (F) are further pressed to increase the axial force acting in the axial direction of the threaded portion. It is possible to prevent the two members from being fastened and loosened by the strength exceeding the fastening state at.

  One of the two members is a cap constituting one of the casings of the fluid filter in which a filter element is accommodated in the casing, and the other one of the two members is a casing of the fluid filter. If it is the base which comprises the other, it can prevent that the fastening with the said cap and said base from which a coefficient of thermal expansion differs loosens at the time of high temperature.

  If the member having a large coefficient of thermal expansion is made of a synthetic resin material, and the member having a small coefficient of thermal expansion is made of a metal material, one of the members can enjoy the effects such as being light in weight by the synthetic resin material and being inexpensive to manufacture. About the other member, effects, such as a high intensity | strength and rigidity, can be enjoyed with a metal material.

  If the cap is made of a synthetic resin material and the base is made of a metal material, the cap is lightweight and can be manufactured at a low cost in a fluid filter or the like disposed in the engine room of a vehicle that becomes hot during use. The base is excellent in strength and rigidity, and the cap and the base can always be maintained in a strong fastening state.

  Even if the fluid filter having the above-described fastening structure is assembled and then used at a higher temperature than the time of assembly, the fastening by the screwing of the cap and the base using materials having different coefficients of thermal expansion will not be loosened. It is possible to always maintain a strong fastening state.

  In the two-member fastening structure according to the present invention, one of two members having different coefficients of thermal expansion includes a threaded portion in which a male screw or a female screw is formed, and the other has a threaded portion in which a female screw or a male screw is formed. A two-member fastening structure that is fastened by screwing by relative rotation of the two members, and a member having a small coefficient of thermal expansion is a screw provided on a member having a large coefficient of thermal expansion. A screw having a pitch shorter than the pitch is provided.

As long as the “two members” have different coefficients of thermal expansion and are fastened by screwing by relative rotation, the material, shape, use location, and the like are not particularly limited. As a material, various materials such as a metal material, a synthetic resin material, and ceramics are applied.
For example, in the present fastening structure, a member having a large coefficient of thermal expansion among two members is made of a synthetic resin material, and a member having a small coefficient of thermal expansion can be used for fastening two members made of a metal material.

The “metal material” can be arbitrarily selected, and examples thereof include an aluminum alloy and steel. Of these, aluminum alloys are lightweight and can be suitably used. “Synthetic resin material” can also be arbitrarily selected, and examples thereof include polyamide resin to which reinforcing fibers such as glass fibers are added. In the case of a synthetic resin material, a material to which a reinforcing material such as glass fiber, glass wool, or carbon fiber is added may be used as necessary to increase the rigidity of the member.
As an aspect in which the coefficient of thermal expansion is different from each other, for example, one member can be made of synthetic resin and the other member is made of metal. Even in such cases, the material properties may be different from each other.

The “threaded portion” of one of the two members is formed by a male screw or a female screw. Further, the “screwed portion” of the other member is formed by a female screw or a male screw having a dimensional difference with respect to the screw provided in the screwed portion. The shape of the thread is not particularly limited. For example, it may be a screw having a thread angle of 60 degrees and formed symmetrically with respect to a right axis, or a trapezoidal screw, a square screw, or the like.
In addition, the screwed part and the screwed part are not limited to the screw structure of the male screw and the female screw, for example, are formed by a spiral groove and a convex part, and are fitted in a spiral shape to each other, The thing of the form which can be screwed together may be sufficient.
These “screwed portion” and “screwed portion” do not simply mean a portion where a male screw or a female screw is formed, but a portion where two members are engaged in screwing by relative rotation. means.

The fastening structure of the present invention can be arbitrarily applied as long as it is a two-member fastening structure in which two members having different thermal expansion coefficients are relatively rotated and fastened to each other, and in particular, an environment in which a temperature difference occurs. It can use suitably for the fastening structure used in.
For example, a cap portion of a tank and containers of an internal combustion engine, specifically, a cap and a base in a fluid filter, and a threaded portion such as a casing and a drain cap can be mentioned. Further, there can be mentioned bushes provided in holes extending from the base to the outside of the base, and screwed portions of bases and caps such as oil tanks and fuel tanks. Furthermore, a screwed part of a base such as a fuel tank of a heater and a cap, a screwed part of a cooler box made of a heat insulating material and a cap provided in the drainage hole, and the like can be exemplified. In particular, the present invention can be suitably applied to the cap portion of the fluid filter and the screwed portion of the base, which become hot during use. This fastening structure does not reduce the clamping force between the two members or reduce the axial force even when the assembly is placed at a higher temperature than when assembled, and always provides a strong fastening state between the two members. This is because it can be maintained.
(First fastening structure)

First, of the two members, a member having a large coefficient of thermal expansion may include a male screw, and a member having a small coefficient of thermal expansion may include a female screw formed at a pitch shorter than the pitch of the male screw.
FIG. 1 is a schematic cross-sectional view for explaining a state in which a member 20 having a large coefficient of thermal expansion and a member 30 having a small coefficient of thermal expansion are screwed together. The threaded portion 20a of the member 20 is provided with a male screw 20b, and the threaded portion 30a of the member 30 is provided with a female screw 30b. Here, the pitch of the thread of the male screw 20b is p, and the pitch of the thread of the female screw 30b is formed to be p−β which is a minute amount (β) smaller than the pitch of the male screw.

When the member 20 and the member 30 are relatively rotated at normal temperature and the screwed portion 20a and the screwed portion 30a are tightened with a predetermined tightening torque, the pitches of the screws provided on both members are different. At the front end side of the portion 20a, the advancing flank surface A of the male screw 20b and the counter-advancing flank surface C of the female screw 30b of the threaded portion 30a are in strong contact. In each of the opposing screw threads, the load applied to the advance side flank surface of the male screw 20b and the counter-advance side flank surface of the female screw 30b is gradually reduced toward the root side of the threaded portion 20a. At the same time, the load applied to the opposite flank surface of the male screw 20b and the advanced flank surface of the female screw 30b is gradually increased toward the root side of the threaded portion 20a in each of the opposing screw threads, and the root side of the threaded portion 20a. , The counter-advance side flank surface B of the male screw 20b and the advance-side flank surface D of the female screw 30b are in strong contact with each other. Thus, a large axial force P ₂₀ in the axial direction of the screw is generated in the member 20, since a large axial force P ₃₀ in the axial direction of the screw members 30 occurs, firmly the two members 20 and 30 Fastened to prevent loosening.

Here, the “tip side” refers to the tip side where the male screw advances (in FIG. 1, the lower side of the threaded portion 20a), and the “root side” refers to the root portion of the screw opposite to the direction in which the male screw advances (see FIG. 1 is the upper side of the screwing portion 20a).
The “advance-side flank surface” of the male screw and the female screw refers to a flank surface in a direction in which the male screw advances (downward in the example of FIG. 1) when screwing. In addition, the “counter-advanced flank surface” of the male screw and the female screw refers to a flank surface on the opposite side to the direction in which the male screw advances when screwed together.
The “axial force” refers to a compression force and a tensile force that are generated in the axial direction of two members fastened by screwing by relative rotation and fasten the two members.

  As described above, when the member 20 and the member 30 fastened at a normal temperature with a predetermined tightening torque are used in a high-temperature environment, the member 20 having a higher coefficient of thermal expansion is more thermally expanded. It is larger than the member 30 with a small rate. For this reason, the flank surface A and the flank surface C are pressed closer to each other at the front end side of the screwing portion 20a than at normal temperature. At the same time, on the base side of the screwing portion 20a, the flank surface B and the flank surface D are pressed more strongly than at normal temperature. Thereby, a larger axial force is generated in the member 20 and the member 30 in the axial direction of the screw than at normal temperature.

Specifically, the linear thermal expansion coefficient of the member 20 is α _20, and the length from the flank surface B to the center portion of the flank surface A of the male screw 20b at normal temperature is L ₂₀ as shown in FIG. If the external thread 20b portion is free expansion, elongation [Delta] L ₂₀ of the length _{L 20} when the temperature increases [Delta] T from the normal temperature, the α ₂₀ · ΔT · _{L 20.} On the other hand, when the linear thermal expansion coefficient of the member 30 is α _30, and the length from the center of the flank surface C to the flank surface D of the female screw 30b at normal temperature is L ₃₀ as shown in FIG. 1, the female screw 30b If parts are free expansion, elongation [Delta] L ₃₀ of the length _{L 30} when the temperature increases [Delta] T from the normal temperature, the α ₃₀ · ΔT · _{L 30.}
In room temperature, the length _{L 20} of the male screw 20b portion is the same as the length _{L 30} of the female screw 30b section. When the temperature is high, the member 20 has a larger linear thermal expansion coefficient than the member 30 and α ₂₀ > α _30. Therefore, in the free expansion, the extension ΔL ₂₀ of the length of the male screw 20b portion is equal to the length of the female screw 30b portion. It is greater than the growth ΔL _30.
Then, each of the flank surfaces where the female screw 30b and the male screw 20b are in contact with each other is further pressed by the difference in length expansion due to thermal expansion, and the flank surface C is located on the tip side of the male screw 20b. At the same time, the flank surface D is strongly pressed by the flank surface B on the base side of the male screw 20b. That is, as a result of increasing the force acting so as to press-contact each flank surface where the female screw 30b and the male screw 20b are in contact with each other, the screw portions of the member 20 and the member 30 are distorted, and according to the strain. The axial force will increase from that at room temperature.
Thereby, when the temperature is high, the tightening force of the screwing portion is increased, and the fastening between the two members 20 and 30 is not loosened, and a firm fastening state is obtained.

(Second fastening structure)
Secondly, in the two-member fastening structure of the present invention, a member having a large coefficient of thermal expansion of the two members includes a female screw, and a member having a small coefficient of thermal expansion includes a male screw formed at a pitch shorter than the pitch of the female screw. You may prepare.
In contrast to the example shown in FIG. 1, FIG. 2 illustrates a case where the member 22 has a small coefficient of thermal expansion and the member 32 has a large coefficient of thermal expansion. The threaded portion 22a of the member 22 is provided with a male screw 22b, and the threaded portion 32a of the member 32 is provided with a female screw 32b. Here, the pitch of the thread of the female screw 32b is p, and the pitch of the thread of the male screw 32b is formed to be p-β smaller than the pitch of the female screw by a minute amount (β).

  When the member 22 and the member 32 are relatively rotated at normal temperature and the screwed portion 22a and the screwed portion 32a are tightened with a predetermined tightening torque, the pitches of the screws provided on both members are different. At the front end side of the portion 22a, the non-advancing flank surface G of the male screw 22b and the advancing flank surface E of the female screw 32b of the screwed portion 32a are in strong contact. In each of the opposing screw threads, the load applied to the non-advancing flank surface of the male screw 22b and the advancing flank surface of the female screw 32b gradually decreases toward the root side of the screwing portion 22a. At the same time, the load applied to the leading flank surface of the male screw 22b and the non-advancing flank surface of the female screw 32b is gradually increased toward the root side of the screwing portion 22a at each of the opposing screw threads. , The advance side flank surface H of the male screw 22b and the counter-advance side flank surface F of the internal screw 32b are in strong contact with each other. As a result, since a large axial force is generated in the axial direction of the screw on the member 22 and the member 32, the two members 22 and 32 are firmly fastened to prevent loosening.

As shown in FIG. 2, the length of the male screw 22b portion at normal temperature is L ₂₂ , and the length of the female screw 32b portion is L ₃₂ . When the member 22 and the member 32 fastened at a normal temperature with a predetermined tightening torque are used in a high-temperature environment, the member 32 has a larger coefficient of thermal expansion. The elongation ΔL ₃₂ is larger than the elongation ΔL ₂₂ of the length of the male screw 22b.
Then, the flank surfaces where the female screw 32b and the male screw 22b are in contact with each other are further pressed by the difference in thermal expansion, and the flank surface G is strengthened by the flank surface E at the front end side of the male screw 22b. At the same time, the flank surface H is strongly pressed by the flank surface F on the base side of the male screw 22b. That is, as a result of an increase in the force acting so as to press-contact each flank surface where the female screw 32b and the male screw 22b are in contact with each other, the screw portions of the member 22 and the member 32 are subjected to strain, and according to the strain. The axial force will increase from that at room temperature.
Thereby, when the temperature is high, the tightening force of the screwing portion is increased, and the fastening between the two members 22 and 32 does not occur and a firm fastening state is obtained.

Here, the “tip side” refers to the tip side where the male screw advances (in FIG. 2, the lower side of the screwing portion 22a), and the “root side” refers to the root portion of the screw opposite to the direction in which the male screw advances (see FIG. 2 is the upper side of the screwing portion 22a).
The “advance-side flank surface” of the male screw and the female screw refers to a flank surface in the direction in which the male screw advances (downward in the example of FIG. 2) when screwing. In addition, the “counter-advanced flank surface” of the male screw and the female screw refers to a flank surface on the opposite side to the direction in which the male screw advances when screwed together.
The “axial force” refers to a compression force and a tensile force that are generated in the axial direction of two members fastened by screwing by relative rotation and fasten the two members.

(Two-member fastening structure in fluid filter)
The fluid filter is a filter of any fluid such as oil and water. FIG. 4 shows an example of an oil filter, in which a filter element 11 is accommodated in a casing 4 composed of two divided bodies. The casing 4 includes a cap 2 and a base 3 that can be screwed together by relative rotation. The shape of the cap 2 and the base 3 is not particularly limited as long as the cap 4 and the base 3 constitute a casing 4 that receives the filter element 11 by being engaged with each other.
Further, the material of the cap 2 and the base 3 can be arbitrarily selected even if they are materials having different coefficients of thermal expansion. Preferably, the cap 2 can be formed of a synthetic resin material, and the base 3 can be formed of a metal material. In this case, the cap 2 includes a male screw, and the base 3 includes a female screw.

The cap 2 and the base 3 constituting the casing of the fluid filter are provided with screws having different thread pitches, and the cap 2 and the base 3 can be fastened by screwing. FIG. 3 is a schematic cross-sectional view for explaining the fastening structure of the base 3 and the cap 2 constituting the casing as described above.
When the cap 2 and the base 3 are relatively rotated at an ambient temperature of 25 ° C. under normal temperature and the screwed portion 2a and the screwed portion 3a are tightened with a predetermined tightening torque, the thread of the female screw 3b provided in the base 3 is reduced. Since the pitch is β smaller than the pitch p of the thread of the male screw 2b provided in the cap 2, the leading-side flank surface J of the male screw 2b and the screwed portion 3a are formed on the tip side of the screwing portion 2a. The anti-advance side flank surface M of the female screw 3b comes into strong contact. At the same time, on the base side of the threaded portion 2a, the non-advancing flank surface K of the male screw 2b and the advancing flank surface N of the female screw 3b are in strong contact. As a result, since a large axial force is generated in the cap 2 and the base 3 in the axial direction of the screw, the cap 2 and the base 3 are firmly fastened to prevent loosening.

  Next, when the cap 2 and the base 3 fastened as described above at normal temperature become high temperature, both of them thermally expand in the axial direction. Since the cap 2 has a higher coefficient of linear thermal expansion than the base 3, when the cap 2 is freely expanded, the extension of the length of the male screw 2 b part is larger than the extension of the length of the female screw 3 b part. Then, the abutting flank surfaces are further pressed by the difference in expansion due to thermal expansion, and the flank surface M is strongly pressed by the flank surface J. At the same time, the flank surface N is strongly pressed by the flank surface K. It will be pushed. As a result, the strain received by the screwed portion 2a and the screwed portion 3a is greater than that at normal temperature, and the axial force of the cap 2 and the base 3 increases according to the strain. The cap 2 and the base 3 are not loosened and a firm fastening state is obtained.

  Contrary to the above, when the thermal expansion coefficient of the cap 2 is smaller than that of the base 3, the thread pitch of the male screw provided in the screwed portion 2 a of the cap 2 is provided in the screwed portion 3 a of the base 3. It may be formed smaller than β of the thread pitch of the female screw. That is, when the member 22 shown in FIG. 2 corresponds to the cap 2 and the member 32 corresponds to the base 3, the same effect as described above can be obtained.

(Fluid filter)
Conventionally, in a casing of a fluid filter, as illustrated in FIGS. 6 and 7, a base 3 made of an aluminum alloy and a cap 2 made of a synthetic resin are assembled by screwing by relative rotation. The thread pitches of the female screw portion 3b of the screwed portion 3a of the base 3 and the male screw portion 2b of the screwed portion 2a of the cap 2 are formed to be the same (p).
After the assembly, as shown in FIG. 6, the screwed portion 3a of the base 3 is sandwiched between the flange 2d of the cap 2 with which the end surface 3e of the tip of the base 3 abuts and the screwed portion 2a of the cap 2. The axial force P, which is an axial compression force, is generated by being compressed. Thereby, the cap 2 and the base 3 are fastened by being firmly fastened.

  However, when used in a high temperature state, the cap 2 and the base 3 are thermally expanded. As described above, the cap 2 and the base 3 are made of different materials, and the cap 2 has a larger coefficient of thermal expansion than the base 3, so that the threaded portion formed by the male threaded portion 2 b of the cap 2 at a high temperature. 2a extends larger than the screwed portion 3a formed by the female screw portion 3b of the base 3, and starts from the contact position V2 between the end surface 3e of the distal end portion of the base 3 and the flange 2d of the cap 2, and It will extend in the axial direction relative to the threaded portion 3a, that is, vertically downward in FIG. As a result, the axial force P is reduced, and the fastening force between the cap 2 and the base 3 tends to be lower than that at normal temperature. That is, even if the cap 2 and the base 3 are relatively rotated at a normal temperature and tightened and tightened with a predetermined tightening torque, the cap 2 and the base 3 are relatively rotated in the opposite direction to those at the time of tightening to loosen the tightening. The loosening torque required for the process tended to decrease significantly compared to the tightening torque at room temperature.

The fluid filter 1 is a filter of an arbitrary fluid such as oil and water, and contains a filter element 11, a protector 13 that supports the filter element 11, and the filter element 11 and the protector 13 as illustrated in FIG. And a cap 2 and a base 3 which can be screwed together by relative rotation, and the cap 2 and the base 3 are provided with the fastening structure of the present invention as shown in FIG.
The shape or the like of the “cap 2” is not particularly limited as long as the “cap 2” is engaged with the base 3 and constitutes the casing 4 that houses the filter element 11 and the protector 13.
In the “base 3”, an inflow path 10 for allowing a fluid to flow into the casing 4 from the outside and an outflow path 9 for flowing the fluid to the outside are usually formed.
The material of the cap 2 and the base 3 can be arbitrarily selected even if the materials have different coefficients of thermal expansion. Among these, it is preferable that the cap 2 is a synthetic resin material and the base 3 is made of a metal material. In this case, the cap 2 includes a male screw, and the base 3 includes a female screw.

The “filter element 11” is a member for filtering by allowing fluid to pass from the outer peripheral side to the central shaft portion, and the material and structure are not particularly limited. Moreover, although the filter element is a cylindrical body, the shape of the outer peripheral side and the inner peripheral side may be similar or different. Furthermore, it is only necessary that one end surface of the central shaft portion is opened, and the other end surface may be opened or closed. Further, the filter element 11 can be provided with a seal member 12 at a portion in contact with the base 3 and the protector 13 to prevent fluid leakage.
The “protector 13” may be arbitrarily selected as long as it can hold the filter element 11 so as not to be damaged by the pressure of the fluid. Further, the protector 13 can be provided with a through hole 6 so that a fluid can pass from the outer peripheral side to the central shaft portion.

  Hereinafter, the fluid filter having the two-member fastening structure of the present invention will be described in detail. In this embodiment, the base and the cap constituting the casing of the oil filter mounted on the cylinder block of the internal combustion engine are exemplified as the two members.

As shown in FIG. 4, the oil filter 1 includes a casing 4 including a bottomed cylindrical cap 2 and a bottomed cylindrical base 3 that can be screwed together by relative rotation. The cap 2 is integrally formed of a synthetic resin material such as a polyamide resin blended with glass fiber from the viewpoint of light weight and manufacturing cost reduction. The base 3 is formed by die casting of an aluminum alloy from the viewpoint of securing the strength of the casing 4 and increasing the rigidity.
The cap 2 is provided with a screwed portion 2a, and the base 3 is provided with a screwed portion 3a. The cap 2 and the base 3 are fastened by screwing by relative rotation.

  An O-ring 5 is mounted in the space above the screwed portion 2 a of the cap 2 and above the screwed portion 3 a of the base 3. In the oil filter 1, when the male screw portion 2 b and the female screw portion 3 b are screwed together and the cap 2 and the base 3 are screwed through the O-ring 5, the inside of the casing 4 is held in a liquid-tight state. It is like that. At the bottom of the base 3, there are provided an oil passage pipe portion 9 that discharges oil inside the casing 4 and an inlet 10 through which oil flows into the casing 4.

Inside the cap 2, a cylindrical protector 13 made of synthetic resin having a large number of through holes 6 is provided. On the outer periphery of the protector 13, a cylindrical filter element 11 formed by folding a filter paper into a fold-fold chrysanthemum shape via a seal member 12 is mounted. The protector 13 includes a flange portion 8 formed on the base end portion side, a spring receiving portion 14 formed inside the vicinity of the base end portion side, and an oil passage connecting portion 15 formed on the tip end portion. .
The flange portion 8 is detachably supported by a protector holding portion 16 formed inside the cap 2, and is prevented from dropping by a stopper 17 formed at an edge portion of the protector holding portion 16. Further, an engaging mechanism such as an engaging claw for integrally rotating the cap 2 and the protector 13 is provided. The oil passage connecting portion 15 is fitted to the oil passage pipe portion 9 of the base 3 so as to be relatively rotatable. Further, a support spring 7 made of a coil spring is provided on the upper part of the spring receiving portion 14 of the protector 13. The support spring 7 biases the protector 13 toward the base 3 side. Due to the urging force of the support spring 7, the seal member 12 provided on the filter element 11 is pressed and the sealing performance is enhanced.

FIG. 3 is a schematic cross-sectional view for explaining a fastening structure of the base 3 and the cap 2 constituting the casing of the oil filter 1 thus configured.
On the outer peripheral surface of the cap 2, a threaded portion 2a comprising a male threaded portion 2b is formed, and the threaded portion 2a is provided with a male threaded portion 2b having a thread pitch of 3.0 mm. On the other hand, a threaded portion 3 a made up of an internal thread portion 3 b is formed on the inner peripheral surface of the base 3, and the thread pitch of the internal thread portion 3 b is larger than the thread pitch of the external thread portion 2 b of the cap 2. It is a small 2.9 mm.

  The operation of this fastening structure is as described above. When the cap 2 and the base 3 are relatively rotated at an ambient temperature of 25 ° C. at normal temperature and the screwed portion 2a and the screwed portion 3a are tightened with a predetermined tightening torque, the male screw 2b is formed at the tip side of the screwed portion 2a. The advancing flank surface J and the counter-advancing flank surface M of the female screw 3b of the threaded portion 3a are in strong contact with each other, and the anti-advancing flank surface K of the male screw 2b is provided at the root side of the screwing portion 2a. And the advancing flank surface N of the female screw 3b are in strong contact with each other. As a result, a large axial force is generated in the axial direction of the screw in the cap 2 and the base 3, so that the cap 2 and the base 3 are firmly fastened.

  Next, as the oil filter 1 in which the cap 2 and the base 3 are assembled as described above becomes hot due to the use of an engine such as a vehicle running, the cap 2 and the base 3 also become hot, and both of them heat in the axial direction. Inflate. Due to the difference in expansion due to thermal expansion of the male screw 2b portion of the cap 2 and the female screw 3b portion of the base 3, the abutting flank surfaces are further pressed, and the flank surface M is strongly pressed by the flank surface J, At the same time, the flank surface N is strongly pressed by the flank surface K. As a result, the strain received by the screwed portion 2a and the screwed portion 3a is greater than that at normal temperature, and the axial force of the cap 2 and the base 3 increases according to the strain. The cap 2 and the base 3 are not loosened and a firm fastening state is obtained.

In the oil filter, the result of the comparison test of the fastening strength between the product of the present invention and the conventional product is as follows. In the test, after tightening the base and the cap with the same tightening torque for the product of the present invention and the conventional product at the normal temperature of 25 ° C, the loosening torque required to loosen the cap from the base is measured under the high temperature of 130 ° C. Thus, the fastening strength of both products was compared.
As a result, the loosening torque at 130 ° C. of the conventional product was almost halved relative to the tightening torque at room temperature of 25 ° C. On the other hand, in the product of the present invention, the loosening torque at 130 ° C. increased to about 1.5 times the tightening torque at room temperature of 25 ° C. As a result, it was confirmed that the fastening force of the conventional oil filter decreases at a high temperature, whereas the oil filter of the present invention increases conversely.

It is typical sectional drawing for demonstrating the screwing state by this fastening structure of the member 20 with a large thermal expansion coefficient, and the member 30 with a small thermal expansion coefficient. It is typical sectional drawing for demonstrating the screwing state by this fastening structure of the member 20 with a small coefficient of thermal expansion and the member 30 with a large coefficient of thermal expansion. It is typical sectional drawing for demonstrating the screwing state of the base and cap of a fluid filter by the fastening structure of this invention. It is an exploded sectional view showing an example of a fluid filter of the present invention. It is typical sectional drawing which shows the screwing state of the 2 members by the conventional fastening structure. It is principal part sectional drawing which shows the fastening structure of the base and cap of the conventional fluid filter. It is a disassembled sectional view which shows the conventional fluid filter.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1; Fluid (oil) filter, 2; Cap, 2a; Screwing part, 2b; Male screw part, 3; Base, 3a; Screwed part, 3b; Female screw part, 4: Casing, 11: Filter element, 20a, 22a; threaded portion, 20b, 22b; male threaded portion, 30a, 32a; threaded portion, 30b, 32b; female threaded portion.

Claims (6)

A two-member fastening structure in which two members are fastened by screwing by relative rotation,
The two members have different coefficients of thermal expansion,
Of the two members, a member having a large coefficient of thermal expansion includes a male screw,
Of the two members, a member having a small coefficient of thermal expansion includes a female screw formed at a pitch shorter than the pitch of the male screw,
When the two members are fastened by screwing the male screw and the female screw, the leading flank surface (A) of the male screw and the counter-advancing flank surface (C) of the female screw are in contact with each other at the tip side of the male screw. , The non-advancing flank surface (B) of the male screw and the advancing flank surface (D) of the female screw abut on the root side of the male screw,
When the member having a large coefficient of thermal expansion thermally expands in the axial direction of the screw, the flank surface (A) and the flank surface (C) are pressed together and the flank surface (B) and the flank surface (D And a two-member fastening structure. A two-member fastening structure in which two members are fastened by screwing by relative rotation,
The two members have different coefficients of thermal expansion,
Of the two members, a member having a large coefficient of thermal expansion includes a female screw,
Of the two members, the member having a low coefficient of thermal expansion includes a male screw formed at a pitch shorter than the pitch of the female screw,
When the two members are fastened by screwing the male screw and the female screw, the forwardly-flank flank surface (G) of the male screw and the advanced-side flank surface (E) of the female screw come into contact with each other at the distal end side of the male screw. The advancing flank surface (H) of the male screw abuts the anti-advancing flank surface (F) of the female screw on the root side of the male screw,
When the member having a large coefficient of thermal expansion thermally expands in the axial direction of the screw, the flank surface (G) and the flank surface (E) are pressed together and the flank surface (H) and the flank surface (F) And a two-member fastening structure. One of the two members is a cap constituting one of the casings of the fluid filter in which the filter element is accommodated in a casing formed of a two-part body,
The fastening structure of two members according to claim 1 or 2, wherein the other one of the two members is a base constituting the other of the casing of the fluid filter. The member having a large coefficient of thermal expansion is made of a synthetic resin material,
The two-member fastening structure according to claim 1 or 2, wherein the member having a low coefficient of thermal expansion is made of a metal material. The cap is made of a synthetic resin material,
4. The two-member fastening structure according to claim 3, wherein the base is made of a metal material. A filter element;
A protector for supporting the filter element;
A cap and a base that house the filter element and the protector and can be fastened together by screwing;
A fluid filter comprising:
The said cap and the said base are provided with the fastening structure of the 2 member in any one of Claims 1 thru | or 5, The fluid filter characterized by the above-mentioned.

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