JPS6132816Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a vibration isolation structure for a center member for supporting an engine, and more specifically for a front engine. The present invention relates to a vibration isolation structure for a center member for supporting a horizontally mounted engine in a front drive type automobile.

Front engine. Due to installation constraints in front-drive vehicles, so-called front-wheel drive vehicles, the engine is often placed horizontally, that is, the crankshaft is placed along the width of the vehicle body. This horizontally mounted engine is installed at two locations on the center member, which is supported at both ends in the longitudinal direction by a pair of cross members that extend in the width direction of the vehicle body, and in two locations on both sides of the vehicle body in the longitudinal direction. It is supported at a total of four locations, one on each of a pair of extending side members. In this case, an engine mount made of anti-vibration rubber is interposed between each member and the engine, but vibrations passing through each member are still transmitted to the passenger compartment, causing low-speed muffled noise and high-frequency noise. It is becoming.

In order to reduce the low-speed muffled sound and high-frequency sound, the center member and the pair of side members are
Because the transmission paths of vibration and the form of vibration themselves are different, it is said that it is better to take measures individually.
Therefore, the present invention aims to reduce the noise by improving the vibration isolation structure of the center member.

Incidentally, the center member is disposed between the side members so as to extend in the longitudinal direction of the vehicle body, and its front and rear ends are supported by a pair of cross members extending in the width direction of the vehicle body. Conventionally, methods for connecting this pair of cross members and the center member include (a) a direct attachment method at both ends in which both ends of the center member are directly fixed to the cross member, and (b) a direct attachment method at both ends.
A double-end vibration isolation method is adopted in which vibration isolation rubber is interposed between each end of the center member and the cross member to connect them.

However, in the former both-end direct mounting method, vibrations are transmitted from the engine via the center member to a large extent, and unless the resonant frequency of the center member is made sufficiently high, the vibration amplitude of the center member becomes large. In addition, with the latter both-end vibration isolation method, while the transmission of vibration from the engine via the center member is reduced, by using a vibration-isolating structure at both ends, bounce resonance where the front and rear of the vehicle body vibrate in the same phase, Pitting resonance occurs, where the front and rear parts of the vehicle vibrate in opposite phases, and the vibration level may even increase.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vibration-isolating structure for a center member that can eliminate the drawbacks of the direct mounting method at both ends and the drawbacks of the vibration-isolating method at both ends.

The center member vibration isolation structure of the present invention is characterized in that the center member includes an end portion connected to one cross member via vibration isolating rubber and an end portion directly connected to the other cross member. shall be.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The center member 10 is arranged in the longitudinal direction of the vehicle body, and is formed in a known shape. As shown in FIG. 1, the front end 11 of the center member 10 is directly connected to a cross member 14 extending in the width direction of the vehicle body by a bolt and nut 16. Anti-vibration rubber 20 is applied to the upper and lower parts of the rear end 12 of the center member 10, respectively, and the rear end 12 is connected to bolts and nuts 2 through the anti-vibration rubber.
2, the cross member 18 extends in the width direction of the vehicle body.
is connected to. Although the cross member 18 is a support member of the steering device in this example, it may be a cross member similar to the front cross member 14.

A front mount 24 and a rear mount 26 for the engine are attached to the center of the center member 10. These two mounts and mounts provided respectively on a pair of side members (not shown) disposed in the longitudinal direction of the vehicle body at both ends in the width direction of the vehicle body, sandwiching the center member 10, allow the engine ( ) is supported. In this case, the center member does not need to be located in the center of both side members.

In the example shown in FIG. 2, the center member 10 is connected to a cross member 14 at the front end 11 via a vibration isolating rubber 20, and is connected to the cross member 18 at the rear end 12.
is directly connected to.

In this invention, as shown in Figs. 1 and 2,
The front end or the rear end is directly connected to one cross member, and the other end is connected to the other cross member via vibration isolating rubber. In this case, which end should be supported with anti-vibration rubber depends on the mounting position of the center member and the vehicle model, depending on the influence of the sound pressure level on the passenger compartment at the end where the center member is connected to the cross member. Since the degree is different,
If the connection end with the higher sound pressure level is provided with a vibration-proofing structure using vibration-proofing rubber, the vibration-proofing effect will be great.

The frequency characteristics of the conventional vibration isolation structure and the vibration isolation structure of the present invention are shown in FIG. In the figure, A is a conventional both-end direct attachment method, B is a conventional both-end vibration isolation method, and C is a direct attachment method according to the present invention, and the other is an anti-vibration method. In A, the vibration level also increases as the frequency increases. In B, the vibration level does not increase as the frequency increases, but reaches a maximum value at a certain frequency like B ₁ and B ₂ , and decreases in other frequency ranges. B has a maximum value B ₁ is a bounce resonance, and B ₂ is a pitching resonance. However, in C, only bounce resonance C ₁ appears,
Pitting resonance appears outside the normal driving range. As a result, the vibration level in the shaded area indicated by D in the figure is lower than in the conventional system. In this way, with the present invention, it is easy to perform so-called frequency tuning so that the pitching resonance generation frequency deviates from the normal running frequency, so that the vibration level in the range including the minimum value from the bounce resonance point to the pitching resonance point It is possible to maintain the

According to the present invention, the vibration level is significantly reduced, especially in the high frequency range, so that the transmission of unpleasant noise to the passenger compartment is reduced. This ensures a comfortable drive.

[Brief explanation of drawings]

1 and 2 are front views showing the vibration isolation structure of the present invention, and FIG. 3 is a frequency characteristic diagram of the vibration level of the conventional method and the method according to the present invention. 10: Center member, 11: Front end, 12:
Rear end, 14, 18: Cross member, 20: Anti-vibration rubber, 22, 24: Engine mount.

Claims (1)

[Scope of utility model registration request] A vibration-isolating structure for a center member in which both longitudinal ends of a center member are supported by a pair of cross members extending in the width direction of a vehicle body to support an engine, wherein the center member is supported by one cross member. An anti-vibration structure for an engine supporting center member, including an end portion connected via anti-vibration rubber and an end portion directly connected to the other cross member.