VIBRATION ISOLATING DEVICE [Technical Field] [0001]
The present invention relates to a vibration isolating device that absorbs a vibration transmitted to a resin molding, which can be applied to a ground station for mobile communications for automobiles or combinations of vehicles, an on-vehicle electronic control unit, or a general industrial machine, for example. [Background Art] [0002]
In recent years, various electronic control devices, sensors and the like on which an electronic circuit board is mounted are increasingly installed in severe vibrating environments. For example, with an electronic control device for automobiles, vibrations caused by the engine or vibrations that occur while the vehicle is running are transmitted to the device. If an excessive vibration is transmitted to the electronic circuit board, electronic components mounted on the board can fail, or a crack can occur in a soldered joint. A simple and common measure to avoid these failures is to reduce the level of vibrations transmitted to the device by using a rubber washer or other vibration absorbing member when tightening a bolt in fixing the device in a vibrating environment as described in Japanese Patent Publication No. 2002-331935 (Patent Literature 1). [0003]
However, with such an arrangement, the bolt tightening force is exerted on the rubber washer. Since the rubber material is a viscoelastic material, the bolt tightening force gradually decreases because of stress relaxation. Therefore, to prevent loosening of the bolt, additional tightening of the bolt or replacement of the rubber material has to be regularly conducted. Therefore, there is a demand for an arrangement in which the bolt tightening force is not exerted on the vibration absorbing member. [0004]
An example of such arrangements is described in Japanese Patent Publication No. 7-280034 (Patent Literature 2), which is shown in FIG. 7. If a housing 3 of an electronic control device that is an object of vibration isolation is a resin molding, a vibration absorbing part can be easily attached to the housing 3 by bonding an elastic member 6, which serves as the vibration absorbing part, to the periphery of a cylindrical insert member 4 made of a metal used for bolt fastening and then installing the assembly in a mold before resin molding. With this arrangement, the bolt tightening force is not exerted on the vibration absorbing part, so that the reliability of the bolt fastening is significantly improved. [0005]
However, since the elastic member 6 is bonded to the whole of the outer periphery of the cylindrical insert member, a vibration in the direction of the axis of the bolt, for example, causes not only tensile deformation and compressive

deformation of the elastic member between flange parts 5 and the housing 3 but also shear deformation of the elastic member between the side surface of the insert member and the housing 3. The longer the insert member, the higher the rigidity of the shear-deformed part of the elastic member becomes, so that the rigidity of the entire vibration absorbing part increases. [0006]
In general, by reducing the rigidity of the vibration absorbing part, the vibration isolating arrangement can reduce the transmissibiiity of vibrational components at lower frequencies. Larger structures require reduction of vibrational components at lower frequencies. However, this apparatus has a characteristic that the longer the insert member, the fewer the vibration absorbing effect in a lower frequency region becomes. Therefore, there h^s been a demand for a vibration isolating device that has a high reliability of bolt fastening, a high manufacturability and a lower rigidity. [Citation List] [Patent Literature] [0007]
[Patent Literature 1] Japanese Patent Publication No. 2002-331935 [Patent Literature 2] Japanese Patent Publication No. 7-280034 [Summary of Invention] [Problems to be Solved by the Invention] [0008]
An object to be attained is to provide a vibration isolating device that has a high reliability of bolt fastening, a high manufacturability, and a high vibration isolating effect in a low frequency region. [Means for Solving the Problems] [0009]
In order to attain the object, the present invention adopts the configurations described in claims, for example. This application includes a plurality of means for attaining the object described ^bove, an example of which is a vibration isolating device comprising a cylindrical insert member that is integrally molded with a resin molding and has a through-hol^ for bolt fastening, and a ring-shaped elastic member disposed in a part of a space between the resin molding and the insert member, wherein the resin molding and the insert member slide in a displaceable manner with respect to each other at a part where the resin molding and the insert member come into contact with each other, the insert member has at least one thick part that has a greater outer diameter than the remaining part of the insert member, and one of surfaces of the elastic member perpendicular to a direction of an axis of the insert member comes into contact with the thick part. [Advantageous Effects of invention] [0010]
The vibration isolating device according to the present invention reduces the rigidity of the vibration absorbing part and can achieve higher vibration isolating effect

in a lower frequency region, given the same material and the same thickness of the
vibration isolating rubber.
[Brief Description of Drawings]
[0011]
[FIG. 1] FIG. 1 is a perspective view of an example of an electronic control device
provided with a vibration isolating device according to the present invention.
[FIG. 2] FIG. 2 is a cross-sectional view taken along the line A-A' in FIG. 1.
[FIG. 3] FIGS. 3 are cross-sectional views for illustrating a vibration isolating device
according to an embodiment of the present invention.
[FIG. 4] FIG. 4 is a perspective view for illustrating how elastic members are attached
to an insert member according to the present invention.
[FIG. 5] FIG. 5 is a cross-sectional view for illustrating a vibration isolating device
according to an embodiment of the present invention.
[FIG. 6] FIG. 6 is a cross-sectional view for illustrating a vibration isolating device
according to an embodiment of the present invention.
[FIG. 7] FIG. 7 is a cross-sectional view for illustrating a conventional vibration
isolating device.
[Mode for Carrying Out the Invention]
[0012]
In the following, embodiments will be described with reference to the drawings. [Embodiment 1] [0013]
FIG. 1 is a perspective view of an electronic control device 1 provided with a vibration isolating device 2 according to the present invention, and FIG. 2 is a cross-sectional view taken along the line A-A' in FIG. 1. The electronic control device 1 is intended to be fixed with a bolt to a vibration generating part. An insert member 4 is fixed to a housing 3 made of a fiber reinforced plastics (FRP) by integral molding. The insert member 4 serves also as a through-hole for bolt fastening and is desirably made of a metal material from the viewpoint of reliability of bolt fastening. The insert member has flange parts 5 at both ends and ring-shaped elastic members 6 are interposed between the flange parts 5 and the housing 3. An interface 7 between the insert member 4, the housing 3 and the elastic members 6 that is parallel with the direction of the bolt axis is a sliding surface at which the components described above can be displaced with respect to each other. The interface 7 prevents adhesion between the resin molding and the insert member 4 and allows the resin molding and the insert member 4 to slide with respect to each other, and therefore, the shearing rigidity between the insert member 4 and the housing 3 can be reduced compared with conventional arrangements. FIG. 3(a) is a cross-sectional view of the vibration isolating device 2 fastened with a bolt to a vibration generating part, and FIG. 3(b) is a cross-sectional view of the vibration isolating device 2 in the case where the vibration generating part is displaced in the direction of the bolt axis. The insert member 4 and the housing 3 are displaced with respect to each other, and the lower elastic member 6 is compressed and deformed, thereby absorbing the vibration.

Given the same material, a thicker elastic member 6 has a lower rigidity and a higher vibration isolating effect in a low frequency region than a thinner elastic member 6. However, the thicker the elastic member 6, the thinner the part of the housing 3 engaged with the insert member 4 becomes. Therefore, the dimensions of the elastic member 6 have to be determined by carefully considering the vibrations in the environment in which the device is placed and the strength of the material of the housing 3. [0014]
To provide the arrangement described above, as shown in FIG. 4, it is more desirable that the elastic members 6 are attached in advance to the cylindrical insert member 4 before resin molding of the housing, and assembly is fixed in the mold when resin molding of the housing is carried out. As described above, the interface parallel with the bolt axis has to be a sliding surface. Therefore, it is more desirable that, after the elastic members 6 are fixed to the insert member 4, any exposed surface is subjected in advance to a treatment to prevent adhesion of the resin material, such as application of a release agent. While the elastic members 6 have to be fixed to the insert member at predetermined positions during th© molding process as shown in FIG. 4, the interfaces between the flange parts and the elastic members have no effect on the vibration isolating effect even if the flange parts and the elastic members are bonded to each other, so that a bonding treatment, such as application of an adhesive, may be carried out on these interfaces. Although the insert member 4 shown in FIG. 4 has a cylindrical shape, the effects of the present invention can be achieved even if the cross section of the cylinder is not circular but elliptical, for example. The insert member 4 may have a polygonal cross section. However, from the viewpoint of adhesion to the elastic members, a cross section closer to a circle is desirable because a gap is less likely to occur. Depending on the shape of the insert member 4, the interface parallel with the bolt axis may be formed by a plurality of planes or formed by a curved plane. The insert member 4 has at least one thick part, which has a greater outer diameter than the remaining part, and the elastic members 6 are each disposed in contact with a surface of the thick part that is perpendicular to the bolt axis and therefore can absorb a vibration in the direction parallel with the bolt axis. [0015]
As a resin molding process, a wide variety of processes, such as injection molding of a thermoplastic resin or compression molding of a thermosetting fiber reinforced plastics using a sheet molding compound (SMC), can be used. However, the relationship between the temperature during molding and the heatproof temperature of the rubber material used for the elastic members 6 has to be carefully considered. For example, a combination of an ethylene propylene rubber (EPDM) commonly used as a vibration isolating rubber and the SMC molding described above can provide the arrangement according to the present invention. [0016]

According to the present invention, the elastic members are shielded from the outside environment. Many rubber materials used for the elastic members change characteristics through oxidation. With the arrangement according to the present invention, the amount of oxygen supplied to the elastic members is remarkably reduced, so that the vibration isolating effect is expected to last for a longer time. [Embodiment 2] [0017]
In the embodiment 1, the insert member 4 has a simple cylindrical shape except for the flange parts 5. As shown in FIG. 3(b), according to the present invention, the elastic members 6 are compressed and deformed to provide a vibration isolating effect. However, many vibration isolating rubber materials are incompressible materials. Therefore, when a vertical compressive load is applied, the compression rigidity increases if the lateral displacement is restricted. In view of this, according to an embodiment 2, as shown in FIG. 5, a recess 10 that provides a clearance that allows for compressive deformation of the elastic member 6 is formed in the insert member 4 at a part that comes into contact with the elastic member 6. In the molding process described above, the recess 10 is sealed by the elastic member 6, so that there is no possibility that the material of the housing flows into the recess 10. The rigidity of the elastic member can be further reduced by making the elastic member more deformable in this way. However, since forming the recess results in the insert member 4 being partially notched, the shape and dimensions of the recess are desirably determined by carefully considering the load on the insert member 4 and other factors. [Embodiment 3] [0018]
In the embodiment 1, the insert member 4 has the flange parts 5 at both ends, thereby fixing the elastic members 6 in the space to provide the vibration isolating effect. Alternatively, the insert member may have a collar part 11 at a middle part thereof as shown in FIG. 6. A vibration isolating effect similar to the vibration isolating effect provided according to the embodiment 1 can be provided by attaching the elastic members 6 to the upper and lower surfaces of the collar part 11. In addition, the ring-shaped elastic member 6 can be attached to the insert member 4 without passing the elastic member 6 over the flange part 5 having a greater outer diameter, so that the manufacturability is drastically improved. In addition, the recess arrangement adopted in the embodiment 2 can also be used in combination. However, the insert member 4 has to have an outer diameter greater than the diameter of the bolt seating surface or the diameter of a washer used, so that the total weight slightly increases. [0019]
Although the description of the embodiments 1 to 3 has been made on the assumption that the vibration isolating device is separate from the object of vibration isolation, the same effects can be achieved even if the inner surface of the through-

hole of the insert member is threaded, and the vibration isolating device is mounted on the vibration generating part. [Reference Signs List] [0020]

1 ELECTRONIC CONTROL DEVICE
2 VIBRATION ISOLATING DEVICE
3 HOUSING
4 INSERT MEMBER
5 FLANGE PART
6 ELASTIC MEMBER
7 INTERFACE
8 BOLT
9 ENGAGING PART
10 RECESS
11 COLLAR

[Claim 1]
A vibration isolating device, comprising:
a cylindrical insert member that is integrally molded with a resin molding and has a through-hole for bolt fastening; and
a ring-shaped elastic member disposed in a part of a space between the resin molding and the insert member,
wherein the resin molding and the insert member slide in a displaceable manner with respect to each other at a part where the resin molding and the insert member come into contact with each other,
the insert member has at least one thick part that has a greater outer diameter than the remaining part of the insert member, and
one of surfaces of the elastic member perpendicular to a direction of an axis of the insert member comes into contact with the thick part. [Claim 2]
The vibration isolating device according to claim 1, wherein the insert member has a recess in an outer surface thereof at a part of the insert member that comes into contact with the elastic member. [Claim 3]
The vibration isolating device according to claim 1 or 2, wherein an inner surface of the through-hole is threaded.