JPH07277007A - Engine sub-frame supporting structure - Google Patents

Abstract

PURPOSE:To provide an engine sub-frame supporting structure capable of restraining the generation of an internally working sound in the car cabin due to the bounce vibration of a sub-frame. CONSTITUTION:In supporting a car body 10 with elastic members 20 and 21 intervening at each corner of a nearly rectangular subframe 17 on which an engine is mounted, a value is set to the spring constant K1 of the two elastic members 20 on the diagonal line of the sub-frame 17, the value which is different from a value set to the spring constant K2 of the other elastic members 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support structure for elastically supporting a subframe on which an engine is mounted on a vehicle body.

[0002]

2. Description of the Related Art For example, in an FF type automobile, as shown in FIG. 5, an engine unit is mounted on a sub-frame 1 having a substantially rectangular shape in plan view, and each corner portion of the sub-frame 1 is mounted via a mount member 2. There is a structure that is elastically supported by the vehicle body. Each of the mount members 2 supports the weight of the engine and absorbs engine vibration to suppress transmission to the vehicle body. An outer cylinder fixed to the subframe 1 side and an inner cylinder fixed to the vehicle body side are provided. It has a structure in which a support rubber is interposed between (for example,
298). The spring constant Ko of such support rubber is conventionally set to a value corresponding to engine weight, engine vibration, and the like.

[0003]

However, in the above-mentioned conventional support structure, the bounce resonance in which the sub-frame 10 is a mass and the support rubber is a spring is in-phase input to the vehicle body through the mount member, and a muffled sound is likely to be generated. There's a problem. This is because the in-phase bounce resonance input to the vehicle body 3 deforms the vehicle body 3 as schematically shown in FIG. 6, which changes the volume of the interior space of the vehicle body 3 and results in muffled sound. it is conceivable that. This muffled noise is apt to occur particularly at an engine speed of around 3000 rpm, and there is a feeling of pressure, and therefore improvement is required.

Here, in order to reduce the in-phase input to the vehicle body, the elastic force (hardness) of each support rubber is increased,
Or it can be lowered. However, if the hardness is increased, the sound from other drive systems may be easily transmitted to the vehicle interior, and if the hardness is decreased, the maneuverability during turning may be reduced, and it is not possible to uniformly change the hardness of each support rubber. I can not cope.

The present invention has been made in view of the above-mentioned conventional situation, and the generation of muffled noise due to the in-phase input of the bounce vibration does not occur without causing the noise from the drive system or the problem of deterioration of maneuverability. An object is to provide an engine subframe support structure that can be suppressed.

[0006]

SUMMARY OF THE INVENTION The present invention provides a subframe support structure for an engine in which each corner portion of a substantially rectangular subframe on which an engine is mounted is supported by a vehicle body with an elastic member interposed therebetween. It is characterized in that the spring constant of any one of the elastic members or the two elastic members located diagonally is set to a value different from the spring constants of the remaining elastic members.

Here, setting the spring constants of the elastic members to different values means making the spring constants larger or smaller than the spring constants of the remaining elastic members. In this case, the total spring constant obtained by combining the elastic members is determined in terms of engine weight, engine vibration, maneuverability during turning, and the like. Therefore, it is desirable to set the respective ratios while ensuring the required total spring constant, and specifically, the range of 1: 5 to 7 is preferable.

[0008]

According to the subframe support structure for an engine of the present invention, since the spring constant of any one elastic member or two elastic members on a diagonal line is changed, torsional vibration occurs in the subframe. This torsional vibration is also input to the vehicle body in the torsional direction. As a result, since the resonance mode due to the torsional deformation is excited in the vehicle body, it is possible to avoid the change in the interior volume due to the in-phase input as in the conventional case, and it is possible to suppress the muffled sound.

Further, in the present invention, since the spring constant of the total tar of each elastic member is secured and only the ratio is changed, it is possible to secure the elastic force corresponding to the engine weight, engine vibration, etc. The noises from other drive systems and the problems of maneuverability at the time of turning do not occur.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views for explaining an engine sub-frame supporting structure according to an embodiment of the present invention.
In the present embodiment, the case of application to an FF type automobile will be described as an example.

In the figure, reference numeral 10 is a vehicle body of an FF type vehicle to which the structure of this embodiment is applied, and an engine unit (not shown) is provided in an engine room 10a in the front part of the vehicle body 10.
Is provided. This engine unit is mounted on the subframe 17. The sub-frame 17 is formed in a substantially rectangular shape in a plan view, and a cross member 18 extending in the vehicle front-rear direction is bridged and joined to a central portion of the sub-frame 17 and an upper portion of the cross member 18 is provided at an upper portion. A bracket 19 extending in the direction is joined.

Mount members 20 and 21 are provided at the corners of the sub-frame 17, respectively. Each of the mount members 20 and 21 has a schematic structure in which an inner member is inserted into the shaft center of an outer member (not shown) and the two members are joined together with a support rubber interposed. The outer member is joined to the sub-frame 17, and the inner member is fastened to the vehicle body 10. As a result, the engine unit is elastically supported by the vehicle body 10 via the sub-frame 17.

The spring constant K1 of the two mount members 20 located on one diagonal line is set to a value larger than the spring constant K2 of the remaining mount members 21 located on the other diagonal line. Specifically, each mount member 2
Support rubbers having different hardnesses are used so that the spring constant K1 of 0 is 5 to 7 times the spring constant K2 of the mount member 21.

The sum of the spring constants K1 and K2 of the mount members 20 and 21 is the sub-frame 17 described above.
The spring constant is set so as to correspond to the weight of the engine unit 11 mounted on the vehicle, engine vibration, and the like.

Next, the function and effect of this embodiment will be described. According to this embodiment, the spring constant K1 of the two mounting members 20 located on the diagonal line is set to the remaining mounting members 21.
Since it is larger than the spring constant K2 of
A torsional vibration is generated in the vehicle, and this torsional vibration is also input to the vehicle body 10 in the torsional direction. As a result, as shown schematically in FIG. 2, since the vehicle body 10 is vibrated in the resonance mode due to the torsional deformation, it is possible to suppress the change in the interior volume of the vehicle body 10 and the muffled sound.

Further, according to this embodiment, each mount member 2
As the total spring constant of the spring constants K1 and K2 of 0 and 21 was changed only while maintaining the required value, the functions of supporting the engine unit and absorbing engine vibration can be ensured. Moreover, there is no problem with noise from other drive systems or maneuverability during turning.

FIG. 3 is a diagram showing the result of an experiment conducted to confirm the effect of this embodiment. In this experiment, the ratio of the spring constant of each mount member was K1 = 7, as compared with the conventional example in which the spring constant Ko of each mount member was the same (see the solid line in the figure).
The sound pressure level of the room noise at the time of acceleration of the engine was measured in this example (refer to the broken line in the figure) where K2 was set. K1 and K2 are dynamic spring constants of the support rubber at 100 Hz.

As is clear from the figure, in the conventional example, the muffled noise is generated in the region where the engine speed exceeds 3000 rpm. On the other hand, in the present embodiment, the sound pressure level in this region is low, and it can be seen that the muffled sound is suppressed.

FIG. 4 is a diagram showing an experimental result of measuring the room sound pressure level by changing the ratio K1 / K2 of the spring constants of the mount members 20 and 21 in the range of 1 to 10. In the figure, the sound pressure level becomes smaller as the above-mentioned ratio of the spring constant becomes larger, and the sound pressure level becomes flat when the ratio exceeds 7. From this, it is understood that the above ratio is preferably in the range of 5 to 7.

In the above embodiment, the case where the spring constants K1 of the two diagonal mount members 20 are changed has been described as an example. However, in the present invention, the spring constant of any one mount member may be changed. . Even in this case, the resonance mode in the twisting direction can be generated with respect to the vehicle body, and the muffled noise can be reduced.

When the spring constant is changed by one, it is preferable to soften the mount member near the driver's seat. Further, in the case of changing only one of the above, softening the mounting member on the rear side is effective for high frequencies in the normal vehicle speed region, and softening the front side is effective for low frequencies in the idling region.

Further, although the FF type automobile has been described as an example in the above embodiment, the present invention is not limited to this and can be applied to, for example, a pickup type truck.

[0023]

As described above, according to the subframe supporting structure for an engine of the present invention, any one elastic member that elastically supports the subframe, or two elastic members located diagonally is used.
Since one elastic member is set to a spring constant different from that of the other elastic members, it is possible to suppress the change in the cabin volume by exciting the resonance mode in the twisting direction with respect to the vehicle body, and as a result, it is possible to reduce the muffled noise. There is.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating an engine sub-frame support structure according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic diagram showing a torsional vibration state of the vehicle body according to the structure of the embodiment.

FIG. 3 is a characteristic diagram showing an effect of the above embodiment.

FIG. 4 is a characteristic diagram showing the relationship between the ratio of the spring constant and the sound pressure level in the above embodiment.

FIG. 5 is a perspective view showing a conventional subframe support structure.

FIG. 6 is a schematic view showing a vehicle body vibration state according to a conventional structure.

[Explanation of symbols]

 10 vehicle body 12 engine 17 sub-frame 20,21 mount member (elastic member) K1, K2 spring constant

Claims (1)

[Claims] 1. A subframe support structure for an engine, wherein each corner portion of a substantially rectangular subframe on which an engine is mounted is supported by a vehicle body with an elastic member interposed therebetween. Alternatively, the subframe support structure for an engine is characterized in that the spring constants of two elastic members located diagonally are set to values different from the spring constants of the remaining elastic members.