JP2003042005A - Rubber floating structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber floating structure for reducing a cutoff frequency and damping vibration noises while suppressing a reduction in seal surface pressure and in permanent strain resistance and maintaining durability. SOLUTION: This rubber floating structure A using a gasket rubber 12 arranged on the whole peripheral edge of the abutment surface of a rocker cover 2 to be mounted on an engine 1 and a washer rubber 11 laid between the fastening surface of a bolt B for fastening the rocker over 2 to the engine 1 and the rocker cover 2 for damping vibration given from the engine 1 comprises a combination of the gasket rubber 12 having a rubber hardness of 40-60 degrees and the washer rubber 11 having a rubber hardness of 40-50 degrees or a combination of the washer rubber 11 having a rubber hardness of 40-60 degrees and the gasket rubber 12 having a rubber hardness of 40-50 degrees.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber floating structure which can be mounted while securing both a vibration damping function and a sealing property when mounting an engine component to a main part.

[0002]

2. Description of the Related Art An engine is formed by connecting a plurality of engine components to each other. Main components constituting an outer shell of the engine are integrally connected to each other, and some of the mounting parts are apt to amplify vibration noise. Are bolted to the vibration source side using a rubber floating structure. For example, a rocker cover attached to a cylinder head or a camshaft case,
Tighten the mounting parts such as the oil pan mounted on the bottom of the cylinder block and the timing belt case mounted on the end of the cylinder block with gaskets and rubber washers so that they are not directly subjected to vibration from the cylinder block on the vibration source side. In many cases, a rubber floating structure is used, such as tightening with bolts. Originally, the mounting parts such as rocker covers directly receive the vibration and noise accompanying the engine drive, and the mounting parts such as the rocker covers, which have an internal space, are easy to amplify the engine vibration and noise and diffuse the noise to the outside. There is a tendency to prevent this. Therefore, when attaching these attachment parts to other engine body component parts, usually, a rubber float structure that has a vibration and noise damping function and can secure the airtightness of the internal space is used. There is.

By the way, when a rubber floating structure is adopted and, for example, the rocker cover is fastened to the cylinder head side, a plurality of fastening bolts are passed through the rocker cover, and each bolt is fastened to the cylinder head or the like. On this occasion,
A washer rubber is interposed between the rocker cover side and the tightening surface of each tightening bolt, and a gasket rubber is interposed between the cylinder head and the entire peripheral edge of the contact surface of the rocker cover. Here, the engine vibration transmitted to the rocker cover side from the cylinder head damps the vibration transmitted to the rocker cover by displacing the washer rubber and the gasket rubber in the vertical direction, which is the longitudinal direction of the tightening bolt, and at the same time improves the sealing performance. I try to hold it.

As described above, the washer rubber and the gasket rubber are intended to damp vibrations and suppress an increase in vibration noise due to engine vibration, and particularly to suppress an increase in vibration noise in the resonance frequency range. In the engine vibration, the vibration frequency of both the cylinder head on the vibration source side and the rocker cover on the mounting component side is out of phase and frequency when the rubber floating structure is adopted. There is a cut-off frequency that inverts large and small, and the vibration level of the rocker cover on the mounting component side drops significantly in the frequency range above the cut-off frequency, so the cut-off frequency is moved to the frequency range below the resonance frequency. It is known that lowering the frequency is effective in reducing noise. Furthermore, the washer rubber and gasket rubber maintain the sealing surface pressure MPa at an appropriate value to ensure the airtightness on the rocker cover side. At the same time, it is necessary to maintain the settling resistance (compression set) to ensure the durability, and the conventional washer rubber and gasket rubber are 60IRHD ( The is used as a rubber hardness standard) hardness of at least the time is common.

[0005]

When the rubber floating structure is adopted and the mounting parts are mounted on the engine side as described above, there is a demand to reduce vibration noise while ensuring sealing property and durability. It is desired to improve the vibration damping function. Here, the cutoff frequency in the conventional rocker cover of the engine is, for example, 2000.
It is in the vicinity of (Hz), and the cutoff frequency is lowered to improve the vibration damping function. In this case, the main resonance frequency of the engine is usually around 1000 (Hz), and it is necessary to set a cutoff frequency below this. Therefore, it is assumed that a rubber material having a lower hardness is used to reduce the spring constant. However, if the washer rubber and the gasket rubber are simply formed of a low-hardness material, a problem that the seal surface pressure and the settling resistance (compression set) are deviated in the direction of deterioration tends to occur. Therefore, it is desired that the cutoff frequency be set to a frequency lower than the resonance frequency while suppressing a decrease in seal surface pressure and a decrease in permanent set resistance (compression set).

On the basis of the above-mentioned problems, the present invention can lower the cut-off frequency while suppressing the decrease of the seal surface pressure and the deterioration of the settling resistance, and can reduce the vibration noise. The purpose is to provide a rubber floating structure that can be achieved.

[0007]

According to a first aspect of the present invention, a gasket rubber is provided on the entire peripheral edge of a contact surface of a mounting part to be mounted on an engine, and a fastening surface of a fastening member for fastening the mounting part to the engine. In the rubber floating structure in which vibration from the engine is damped by the washer rubber interposed between the mounting part and the mounting part, the rubber hardness is 40 to
The gasket rubber having a hardness of 60 degrees and the rubber hardness of 40 to 5
A combination with the washer rubber having a degree of 0 degrees or a combination of the washer rubber with a rubber hardness of 40 to 60 degrees and the gasket rubber with a rubber hardness of 40 to 50 degrees. In this way, the attachment parts attached to the engine with the fastening members have a rubber hardness of 40 to
A combination of a gasket rubber of 60 degrees and a washer rubber of 40 to 50 degrees, or a rubber hardness of 4
The washer rubber having a hardness of 0 to 60 degrees and the rubber hardness of 40 to
Since the combination with the gasket rubber of 50 degrees is adopted, the cutoff frequency can be lowered, the vibration from the engine applied to the mounting parts can be damped, and the sealing surface pressure can be kept comparatively large, It is possible to secure durability by suppressing deterioration of settling property.

In the rubber floating structure according to the first aspect of the present invention, the gasket rubber and the washer rubber may be acrylic rubber or nitrile rubber, respectively. In this way, the washer rubber interposed between the fastening member for fastening the mounting component to the engine and the mounting component, and the gasket rubber interposed between the mounting component and the engine are each molded with acrylic rubber or nitrile rubber. Therefore, it is possible to easily reduce the hardness of the washer rubber and the gasket rubber, and it is possible to secure oil resistance and heat resistance, and to secure a rubber floating structure that is durable for use in an engine.

[0009]

FIG. 1 shows an engine 1 to which a rubber floating structure A of the present invention is applied. The rubber floating structure A is shown in FIG.
Is used to connect the rocker cover 2 to the upper end of the engine 1. In the engine 1, a cylinder head 5, a camshaft case 6, and a rocker cover 2 are stacked in this order on an upper part of a cylinder block 4, and they are connected to each other, an oil pan 3 is connected to a lower part, and a timing is provided at one end of the cylinder block 4. The belt cover 8 is connected.

The engine 1 is a multi-cylinder diesel or gasoline engine, and a plurality of combustion chambers (not shown) are arranged inside the cylinder block 4 along the longitudinal direction X of the engine.
Inside the cylinder head 5 and the camshaft case 6, a valve operating system (not shown) is provided, and each of these parts serves as a vibration source. Here, the cylinder block 4, the cylinder head 5,
The camshaft case 6, the oil pan 3, and the timing belt cover 8 are integrally connected to each other by tightening bolts (not shown). On the other hand, the rocker cover 2 is tightened with the tightening bolts B using the rubber floating structure A, which will be described later, to the camshaft case 6, whereby the sealability is secured and vibration noise is attenuated.

The camshaft case 6 integrally connected to the cylinder head 5 has a substantially rectangular outer peripheral frame portion 601 and an inner frame portion 6.
02 (see FIGS. 2A and 2B), and the rocker cover 2 is placed on the upper end surface f of the outer peripheral frame portion 601. The rocker cover 2 has a substantially rectangular lid shape as shown in FIG.
An inverted dish-shaped main portion 201 that bulges upward and a flange portion 202 that extends from the entire peripheral edge of the main portion 201 are provided, and these are integrally formed by sheet metal, aluminum, heat-resistant resin, or the like. The flange portion 202 is formed in an annular shape so as to continuously contact the upper end surface f of the annular outer peripheral frame portion 601 of the camshaft case 6. The main portion 201 has a central mounting hole h1 described later formed at a position along the longitudinal direction of the rocker cover 2 (the same as the engine longitudinal direction X) at a predetermined interval with a plurality of predetermined intervals therebetween. An oil supply hole 9 that is normally closed by the cap 7 is formed in the central portion in the arrangement direction.

Further, the flange portion 202 is formed with a plurality of mounting holes h penetrating from the upper surface toward the lower surface at predetermined intervals along the longitudinal direction of the flange (the peripheral direction of the rocker cover). Flange lower surface f inside the rocker cover (right side in Fig. 2 (a)) from the arrangement position
1 is formed a downward concave long groove m. The concave long groove m is formed continuously in an annular shape along the flange longitudinal direction, and an annular gasket rubber 12 described later is fitted therein.
The upper end surface f of the camshaft case 6 and the flange lower surface f1 of the rocker cover 2 facing the camshaft case 6 are formed into flat surfaces that can be in intimate surface contact with each other if the gasket rubber 12 described later is excluded. It

As shown in FIGS. 2 (a) and 2 (b), each mounting hole h formed in the flange portion 202 has a bolt hole bh formed in the upper end surface f of the camshaft case at a position facing the mounting hole h. The flange portion 202 of the rocker cover 2 can be screwed to the camshaft case 6 by screwing the bolts B, which are formed so as to communicate with each other and are fitted and inserted into the respective mounting holes h, into the bolt holes bh. Similarly, rocker cover 2
Each central mounting hole h1 of the main portion 201 of the main body 201 is disposed so as to face the central bolt hole bh1 of the inner frame portion 602 in the camshaft case 6. Here, the bolt B, which is the fastening member inserted into the central mounting hole h1, is a washer rubber 1 described later.
The center of the rocker cover 2 can be screwed to the side of the camshaft case 6 by being screwed into the central bolt hole bh1 with 1 inserted.

As shown in FIGS. 2A and 2B, each mounting hole h of the flange portion 202 of the rocker cover 2 and the main portion 2 are shown.
Each central mounting hole h1 of No. 01 has an upper end formed in tapered portions h-1 and h1-1 of the cone surface, and a lower portion thereof has a straight portion h-.
2, h1-2. Tapered parts h-1, h1-1
In addition to facilitating the attachment of the bolt B fitted therein, it can function to apply the tightening force of the bolt B fitted with the washer rubber 11 to the flange 202 and the main portion 201. Each washer rubber 11 is formed of nitrile rubber (NBR) capable of ensuring oil resistance and heat resistance, and has a top shape having a bolt insertion hole, and an upper flat surface i at the upper end and a cone-shaped convex surface j at the lower end. It is formed. The upper plane i can come into close contact with the lower surface of the head, which is the tightening portion of the bolt B, through the washer 13, and the cone-shaped convex surface j is each mounting hole h of the rocker cover 2,
The tapered portions h-1 and h1-1 of h1 can be closely joined. Therefore, when the bolt B is tightened to the camshaft case 6, the washer rubber 9 is elastically deformed by an amount equivalent to the tightening force, and the tightening force can be added to the flange portion 202 and the main portion 201 of the rocker cover 2 for sealing. The cover 2 can be pressed so as to be elastically displaceable in the vertical direction of the bolt, which is the vertical direction.

A concave long groove m formed in the flange portion 202
Gasket rubber 12 is interposed between and the upward surface f of the camshaft case 6. The gasket rubber 12 is elastically deformed by being pressed against the upward surface f of the camshaft case 6 by the tightening force received when the rocker cover 2 is tightened by the bolt, and at that time, a seal surface pressure (MPa) is generated, so that sealing performance can be secured. . As shown in FIGS. 3 and 4 (a), the gasket rubber 12 is arranged so as to oppose along the entire outer peripheral edge on the lower surface side that is the contact surface of the rocker cover 2. Acrylic rubber AC with good heat resistance and heat resistance
It is molded with M, AEM, nitrile rubber (NBR), or the like. The cross-sectional shape of the gasket rubber 12 is shown in FIG.
As shown in (a), it is composed of a base portion 121 and a protruding portion 122. The base portion 121 is formed by doubling the upper and lower seal step portions k so that it can be tightly fitted in the trapezoidal concave long groove m (see FIG. 2A), and the protruding portion 122 is compared with the base portion 121. It is tapered. Since the protruding portion 122 is formed in a tapered shape, the contact area can be made relatively small when the protruding portion 122 abuts on the upward surface f of the camshaft case 6, and as a result, the protruding portion 1 increases as the tightening force increases.
The contact area of 22 is gradually increased. For this reason,
The gasket rubber 12 can keep the contact area against the tightening force relatively small, can hold the elastic displacement amount in the gasket height direction H relatively large, and can secure the vibration damping function. Moreover, by keeping the contact area relatively small, the seal surface pressure (MPa) is made relatively large and the sealing property is secured.

The cross-sectional shape of the gasket rubber 12 is
Instead of the one shown in FIG. 2 (a), as shown in FIG. 2 (b), a substantially tapered gasket rubber 1 whose tip is flattened is shown.
2a may be used, or another substantially tapered shape may be adopted. Regardless of whether the gasket rubber 12 having a substantially tapered distal end is used or any other shape, the contact area associated with the elastic displacement of the gasket rubber 12 with respect to the tightening force is suppressed to a relatively small value. It is preferable that the amount of elastic displacement in the gasket height direction H be kept relatively large and the vibration damping function be ensured. As described above, the washer rubber 11 is made of nitrile rubber (NBR) and the gasket rubber 12 is made of acrylic rubber (AEM). The hardness of the nitrile rubber (NBR) and acrylic rubber (AEM) adopted here is Both are of 50 IRHD (International Rubber Hardness Standard), which can sufficiently reduce the spring constant and lower the cut-off frequency to reduce the seal surface pressure (M
The one that can secure Pa) was adopted. Here, the combination of the materials of the washer rubber 11 and the gasket rubber 12 may be other combinations, and it is considered that it is easy to optimize the seal surface pressure and the cutoff frequency by using these rubber materials. Will be adopted.

In addition, in setting the hardness distribution range of the washer rubber and the gasket rubber in the claims and the detailed description of the present application, it is assumed that the allowable width is ± 5 IRHD. Therefore, when 40IRHD to 60IRHD is set as the threshold value of the hardness distribution range, the allowable width of the hardness distribution range is 35IRHD to 65IRH.
The range of D is included. Next, the characteristics of each value of the seal surface pressure (MPa), the cutoff frequency (Hz), and the compression set (%), which is a set, are obtained by varying the hardness of the washer rubber 11 and the gasket rubber 12. Description will be made in comparison with the value of each test material. First, the seal surface pressure when the rocker cover 2 was tightened and coupled to the camshaft case 6 with a predetermined tightening force was measured.

The vibration tester 14 used in this measurement is shown in FIG.
As shown in FIG. 6, a drive base 16 corresponding to the camshaft case 6 driven by the vibration exciter 15, and an upward surface ft of the drive base 16.
And a movable base 17 corresponding to the rocker cover 2 which is tightened with the tightening bolt B1. The movable table 17 has a diameter d (for example, 100 mm) and has a disk shape of, for example, 500 g, a mounting hole 18 for the tightening bolt B1 is formed in the center thereof, and a downward annular groove 19 is provided on the lower surface of the peripheral portion for each test. The gasket rubber T1 is attached. Each test washer rubber T2 is mounted between the peripheral portion of the insertion hole 18 of the movable table 17 and the lower surface of the head of the tightening bolt B1.

Here, between the washer rubber T2 (for example, washer rubber 11) and the taper portion h-1 (or h1-1) of each mounting hole 18 (hole corresponding to h, h1), and the gasket rubber T1 ( For example, a pressure sensitive paper (not shown) is provided between the gasket rubber 12 of reference numeral 12) and the upward surface ft of the drive base 16 (upward surface f of the camshaft case 6), and the sealing surface pressure (MPa) is measured. . Here, the circles in Table 1 which are combinations of hardness when the allowable value of the sealing surface pressure (MPa) exceeds (for example, 0.8 MPa in this case), and the marks X in other combinations are shown. Marked.

[0020]

[Table 1]

As shown in Table 1, as the hardness of the washer rubber 11 and the gasket rubber 12 approaches the 30IRHD side, the sealing surface pressure (MPa) decreases too much and the allowable value (0.8 MPa) is satisfied. It became clear that there was not (x mark). If the gasket rubber 12 has an excessively high hardness, the amount of deformation of the gasket rubber 12 is reduced, and an appropriate amount of elastic deformation cannot be ensured, so that the gap between the upward surface ft (the upward surface f of the camshaft case 6) is reduced. It was found that the seal area could not be stably formed and the sealability could not be secured.

Further, instead of measuring the sealing surface pressure (MPa) using a pressure-sensitive paper (not shown), the sealing pressure (kgf) inside the rocker cover 2 (lower movable area g of the movable table 17) is used.
/ Cm ² ) and the measurement result of the airtightness is shown in FIG. 7. This test result is almost the same, and the washer rubber 11
It became clear that the required value of the sealing pressure was not satisfied as the hardness of each of the rubber washer (described as a rubber washer) and the gasket rubber 12 (described as a gasket) approached the 30IRHD side.

As described above, the washer rubber 11 is basically used.
On the side where the hardness of the gasket rubber 12 exceeds 40 IRHD, the surface pressure (MP
It became clear that a) and the sealing pressure (kgf / cm ² ) were maintained at appropriate values. Next, the characteristics of the cutoff frequency (Hz) when the hardness of the washer rubber 11 and the gasket rubber 12 are changed will be compared with the values of the test materials.
First, using the vibration tester 14 described with reference to FIG. 5, the vibration characteristics of the washer rubber and the gasket rubber for each test at each hardness were measured, and the characteristics of the cutoff frequency in Table 1 were obtained.

Here, the downward annular groove 1 of the vibration tester 14 is used.
Each gasket rubber T1 for test is attached to 9 and the test rubber is attached between the taper portion h-1 of the mounting hole 18 (hole corresponding to h, h1) of the movable table 17 and the lower surface of the head of the tightening bolt B1. Each washer rubber T2 is attached. Here, the movable base 17 and the drive base 16 are provided with acceleration sensors 21 and 2, respectively.
2 is attached, each acceleration signal is taken into the controller 23, and the vibration characteristic value {mobility root mean square (cm / s / kg / cm ² ) ² } according to the acceleration signal is 4000.
It was measured in the frequency range up to (Hz). As such washer rubber T2 and gasket rubber T1 for testing, washer rubber (marked as a rubber washer) made of NBR and gasket rubber (marked as a gasket) made of AEM were sequentially attached to the vibration tester 14 in an actual vehicle. Appropriate predetermined tightening force is applied, the cut-off frequency is measured, the suitability is judged, and the result is shown in Table 1 as above-mentioned seal surface pressure (MPa).
Was also written.

Here, an allowable value of the cutoff frequency (Hz), for example, 800 (Hz) in this case, the resonance frequency (1
A value sufficiently lower than 000 Hz) is set, and combinations below this value are indicated by ∘, and combinations other than this are indicated by ×.
As shown in Table 1, as the hardness of each of the washer rubber 11 (denoted as a rubber washer) and the gasket rubber 12 (denoted as a gasket) approaches the 70IRHD side, the cutoff frequency (Hz) increases to 800 ( It is clear that the value below the allowable value of (Hz) is not satisfied.

Here, the washer rubber 11 (NB, which has a hardness of 50 IRHD and is adopted in the rubber floating structure A of FIG.
R) and a gasket rubber 12 (AEM) equivalent test material, it is clear that a cutoff frequency (about 600 Hz) sufficiently lower than the permissible value of 800 (Hz) (marked with a proper circle) is obtained. It was

Furthermore, washer rubber 11 of 50 IRHD
(NBR) and 60IRHD gasket rubber 12 (A
EM) test results with a corresponding test material, or vice versa,
60 IRHD washer rubber 11 (NBR) and 50I
Even the test material corresponding to the gasket rubber 12 (AEM) of RHD obtained cutoff frequencies (640 to 620 Hz) below the allowable value of 800 (Hz) (marked with an appropriate circle). On the other hand, both are 60 IRHD washer rubber 11 (made by NBR) and gasket rubber 12 (AEM
The test result of the equivalent test material is 800 (Hz)
A cutoff frequency of about 850 (Hz) that exceeds the allowable value of (indicated by an incorrect X mark) was detected.

Incidentally, here, washer rubber 11 made of NBR, which is considered to easily achieve the effect of reducing the cut-off frequency.
And test material T equivalent to AEM gasket rubber 12
1, T2 were used. If, instead, a rubber material with other similar rubber characteristics is used, it is considered that the characteristic value of the cutoff frequency deviates, but even if the deviation width in such a case is taken into account, the By adjusting the hardness combination of the washer rubber and the gasket rubber so that the cut-off frequency can be sufficiently reduced so that the off-frequency is sufficiently lower than the resonance frequency, it is possible to reliably measure the vibration noise attenuation. Next, here, the washer rubber 11 (NBR) and the gasket rubber 12 adopted in the rubber floating structure A of FIG.
The results of the actual vehicle vibration test using (AEM) are shown in FIG.

Also in this case, the rocker cover 2 and the camshaft case 6 are respectively provided with acceleration sensors (not shown), and their vibration characteristic values {mobility root mean square (cm /
s / kg / cm ² ) ² } was measured in the frequency range up to 4000 (Hz).

Here, the vibration characteristics of the first embodiment using the 50IRHD washer rubber 11 (NBR) and the gasket rubber 12 (AEM) adopted in the rubber floating structure A of FIG. Rubber (N
BR) and 60 IRHD gasket rubber (NBR) in the second embodiment, the vibration characteristics are indicated by a two-dot chain line B, and the washer rubber (NBR) and gasket rubber (NBR) are both set to 60 IRHD in the conventional example (currently). The solid line C shows the vibration characteristics of the above, and the broken line D shows the vibration characteristics of the camshaft case 6. As is clear here, the cutoff frequency at which the solid line C of the current example intersects the vibration characteristic line D of the camshaft case is 2000 (Hz), and this frequency is the resonance of the normal engine. Frequency (about 10
It is located in a higher frequency range than near (00 Hz). It is clear that the presence of the resonance frequency in the lower frequency range than the cutoff frequency is a factor of the high vibration noise at present.

On the other hand, the cut-off frequency at which the alternate long and short dash line A of the first embodiment intersects the vibration characteristic line D of the camshaft case is 750 (Hz), and the two points of the second embodiment. The cutoff frequency at which the chain line B intersects was 710 (Hz). As is clear from this, the cutoff frequency is the allowable value 800 (Hz) in both the first embodiment (value in the rubber floating structure adopted by the engine of FIG. 1) and the second embodiment (sufficiently smaller than the resonance frequency). It became clear that it became lower, the region where the vibration level was high was narrowed, the vibration level at the resonance frequency could be damped, and the effect of reducing vibration noise, that is, the reduction of the sound production amount of 6 dB could be expected here. In Table 1, the cutoff frequency (Hz) and the seal surface pressure (MPa) are both appropriate, that is, an appropriate hardness combination region e that can prevent the cutoff frequency from decreasing and the seal surface pressure from excessively decreasing. Is indicated by a two-dot chain line.

Next, the compression set (%) of the gasket rubber formed of AEM (acrylic rubber) having a hardness of 50 IRHD, which is the set, was measured. The test material here is AEM
(Acrylic rubber) gaskets with current hardness of 60IRHD, hardness of 50IRHD, hardness of 40I
Each test material of RHD was adopted. As a result, as shown in FIG. 8, each of these three test materials was 50 (%).
It was judged that it was possible to secure sufficient durability when it was installed in an actual vehicle, satisfying the allowable value (described as the specification) of.

As mentioned above, the rubber floating structure A here is used.
Then, a combination of a gasket rubber 12 having a rubber hardness of 40 to 60 IRHD and a washer rubber 11 having a rubber hardness of 40 to 50 IRHD, or a rubber hardness of 40 to 60 I
RHD washer rubber 11 and rubber hardness 40-50
The cutoff frequency (Hz) is 800 (H
The value can be reduced below the allowable value of z), and the frequency can be lowered. As a result, the vibration applied to the rocker cover 2 from the camshaft case 6 can be damped, the sealing surface pressure (MPa) can be held relatively large, and the deterioration of the sag resistance can be suppressed and the durability can be ensured. In the above, although the rocker cover 2 is attached to the camshaft case 6, the present invention can be similarly applied to the case where the rocker cover is directly attached to the cylinder head in the case of an engine without the camshaft case. Similar effects can be obtained.

[0034]

As described above, according to the present invention, the mounting component mounted on the engine by the fastening member has a rubber hardness of 40 to 40.
A combination of a gasket rubber of 60 degrees and a washer rubber of 40 to 50 degrees, or a rubber hardness of 4
Washer rubber with 0-60 degrees and rubber hardness 40-50
Since it uses a combination with a gasket rubber, the cutoff frequency can be relatively reduced and the frequency can be lowered, the vibration from the engine applied to the mounting parts can be damped, and the sealing surface pressure can be kept relatively large. , It is possible to suppress the deterioration of the settling resistance and ensure the durability. If the gasket rubber and the washer rubber are acrylic rubber or nitrile rubber, respectively, the washer rubber interposed between the fastening member and the mounting component for fastening the mounting component to the engine, and the interposition between the mounting component and the engine. Since each gasket rubber to be formed is formed of acrylic rubber or nitrile rubber, it is possible to easily reduce the hardness of these washer rubber and gasket rubber,
Moreover, oil resistance and heat resistance can be secured, and a durable rubber floating structure can be secured when used in an engine.

[Brief description of drawings]

FIG. 1 shows the overall structure of a rubber floating structure adopted in an engine as an embodiment of the present invention.

2 is an enlarged cutaway sectional view of a fastening portion between a rocker cover and a camshaft case to which the rubber floating structure of FIG. 1 is applied, (a) showing a flange portion, and (b) showing an inner frame portion.

FIG. 3 is an enlarged exploded perspective view of a rocker cover and gasket rubber that are fastened with the rubber floating structure of FIG.

4 shows a gasket rubber used in the rubber floating structure of FIG. 1, (a) is an enlarged sectional view of the gasket rubber of FIG. 1,
(B) is an expanded sectional view of another gasket rubber as a modified example.

5 shows a vibration tester for performing a vibration test or the like by mounting a washer rubber and a gasket rubber as test materials used in the rubber floating structure of FIG. 1, (a) is a schematic view of the tester,
(B) shows a movable base.

FIG. 6 is a vibration characteristic diagram of a rocker cover of an engine using the rubber floating structure of FIG.

FIG. 7 is a seal pressure diagram according to a difference in hardness of a washer rubber and a gasket rubber used in a rocker cover of an engine using the rubber floating structure of FIG.

8 is a compression set diagram according to the difference in hardness between the washer rubber and the gasket rubber used in the rocker cover of the engine using the rubber floating structure of FIG. 1. FIG.

[Explanation of symbols]

1 engine 2 rocker cover 202 Flange 11 washer rubber 12 Gasket rubber f Top surface f1 Flange bottom surface A rubber floating structure B bolt X engine longitudinal direction

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Claims (2)

[Claims] 1. A gasket rubber disposed on the entire periphery of an abutting surface of a mounting part to be mounted on an engine, and a gasket which is interposed between a tightening surface of a fastening member for tightening the mounting part to the engine and the mounting part. In a rubber floating structure for damping vibrations from an engine with a washer rubber, a combination of the gasket rubber having a rubber hardness of 40 to 60 degrees and the washer rubber having a rubber hardness of 40 to 50 degrees, or a rubber hardness of 40. A rubber floating structure comprising a combination of the washer rubber having a hardness of -60 degrees and the gasket rubber having a rubber hardness of 40 to 50 degrees. 2. The rubber floating structure according to claim 1, wherein the gasket rubber and the washer rubber are acrylic rubber or nitrile rubber, respectively.