JP4558137B2 - Vehicle front structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle body front structure, and more particularly to a vehicle body front structure that includes a side frame and a subframe that is coupled to the side frame and supports a front wheel, an engine, and the like.
[0002]
[Prior art]
A front portion of a vehicle, for example, an automobile is partitioned into an engine room 103 and a vehicle compartment 104 by a toe board 101 and a floor 102 continuously formed at the lower end of the toe board 101, as schematically shown in a side view of the main part in FIG. A side frame 105 extends in the front-rear direction along the lower surface of the toe board 101 and the floor 102 from the front portion of the engine room 103, and a subframe 106 that supports the front wheels, the engine, and the like extends below the side frame 105, The rear end of the sub frame 106 is firmly supported by the side frame 105, and the front part is coupled to the side frame 105 via the support bracket 107.
[0003]
Further, as disclosed in Japanese Patent Application Laid-Open No. 11-171045 and schematically shown in FIG. 7, a cross member 113 is provided between the front ends and the rear ends of the left and right side members 111, 112 extending in the longitudinal direction of the vehicle body. A substantially rectangular frame-shaped subframe 110 connected at 114 is formed, and the four corners of the subframe 110 are supported on the left and right side frames 121 and 122 via bolts 125, 126, 127, and 128, respectively.
[0004]
When an impact load P of a predetermined value or more is applied from the front of the vehicle, the left rear bolt 127 is first broken and the rear end of the left side member 111 is separated from the side frame 121, and then the right rear bolt A vehicle body front structure is proposed in which 128 is broken and the rear end of the right side member 112 is separated from the side frame 122.
[0005]
[Problems to be solved by the invention]
According to the former vehicle body structure shown in FIG. 6, when an impact load P of a predetermined value or more acts on the front end of the sub-frame 106 from the front, the rear end is firmly coupled, and therefore, as shown by a two-dot chain line 106a in FIG. The intermediate portion of the subframe 106 may buckle and deform so as to protrude downward. When the subframe 106 opposes the impact load P input from the front, the deceleration of the vehicle gradually increases. When the frame 106 buckles and the drag against the impact load P disappears, the deceleration decreases rapidly. Therefore, there is a concern that the peak value of the deceleration occurs at the moment of buckling and the impact cannot be reduced sufficiently. Is done.
[0006]
Further, according to the latter, Japanese Patent Application Laid-Open No. 11-171045, when the subframe 110 receives an impact load P from the front, the rear portions of the left and right side members 111 and 112 are separated from the side frames 121 and 122 with a time difference. Therefore, compared with the case where the rear ends of the left and right side members 111 and 112 are simultaneously separated from the side members 121 and 122 and one deceleration peak occurs instantaneously, the deceleration peak is distributed in two. The peak value can be kept low to reduce the impact, and the deceleration can be continuously generated.
[0007]
However, when the impact load P is received, the rear ends of the side members 111 and 112 are separated from the side frames 121 and 122 with a time difference, so that the subframe 110 behaves and the side members 111 and 112 are stably seated. Since the bending deformation is hindered and the absorption of impact energy due to the deformation of the subframe 110 becomes unstable, an effective reduction in impact cannot be obtained, and it is difficult to predict the impact energy absorption characteristics of the subframe 110 in advance. is there.
[0008]
Accordingly, an object of the present invention made in view of the above point is to provide a front body structure of a vehicle in which stable impact energy absorption characteristics are obtained by a subframe when subjected to an impact load.
[0009]
The invention of the front vehicle body structure of the vehicle according to claim 1 that achieves the above object includes a side frame extending in the longitudinal direction of the vehicle body, and a sub frame extending and supporting in a longitudinal direction below the side frame. In the front vehicle body structure of the vehicle, at least one attachment point for attaching to the side frame with a fixture on each of the front side portion, the extension portion located in the intermediate region, and the rear side portion of the subframe. Of the attachment points, the strength of the fixture at the attachment point of the extending portion is set lower than the strength of the fixation portion of the attachment point at the front side portion and the rear side portion.
[0010]
According to the invention of claim 1, since the subframe is mounted and supported on the side frame at the mounting points distributed along the front-rear direction, when an impact load acts on the front end of the side frame from the front, The deformation and behavior generated in the frame are suppressed, the drag of the subframe against the impact load acting from the front is ensured, and an effective deceleration is obtained.
[0011]
In addition, a deformation mode characteristic in which a deformation part generated in the subframe based on an excessive impact load, that is, an inflection point is set between each attachment point, is obtained, and the energy generated by the deformation as the number of deformation parts increases. And the effectiveness against impact loads is increased resulting in effective deceleration. Furthermore , by setting the strength of the fixture at the attachment point of the extension part of the subframe to be lower than the strength of the fixture at the attachment point of the front side part and the rear side part, the attachment point of the extension part when the subframe is deformed This can break down the fixing tool and reduce the drag of the subframe. Thereby, the deformation mode characteristics of the subframe can be adjusted, and a stable shock energy absorption characteristic can be obtained.
[0012]
According to a second aspect of the present invention, in the front body structure of the vehicle according to the first aspect, the subframe has a front inclined portion that descends as it moves rearward between the front side portion and the extension portion. And it has the back side inclination part which rises as it shifts back between the extension part and the back side part, It is characterized by the above-mentioned.
[0013]
As described in claim 2, by bending the shape of the subframe in advance, it becomes possible to predict the inflection point of the deformation mode characteristic of the subframe due to the impact load, and the deformation of the subframe varies. The effect of claim 1 is effectively achieved.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(Reference example)
A reference example of a vehicle front body structure according to the present invention will be described below with reference to FIGS. The arrow F indicates the front of the vehicle body, and the arrow OUT indicates the side of the vehicle body.
[0017]
FIG. 1 is a perspective view of a main part showing an outline of a vehicle body frame at the front of the vehicle body, FIG. 2 is a side view of FIG. 1, FIG. 3 is an explanatory diagram schematically showing FIG. 2, and FIG. It is a graph explaining.
[0018]
The front part of the vehicle body is partitioned into an engine room 3 and a vehicle compartment 4 by a toe board 1 and a floor 2 continuously formed at the lower end of the toe board 1, and a pair of left and right side frames 10 (only the left side is shown in the vehicle traveling direction) Extends in the front-rear direction from the front end of the engine room 3 to the front surface of the toe board 1 and the lower surface of the floor 2, and a suspension cross member 20 extending in the vehicle width direction is installed between the left and right side frames 10. .
[0019]
The side frame 10 has a first subframe support 21 formed by brackets in order from the front side, a second subframe support 22 formed at the end of the suspension cross member 20, a third subframe support 23, a first 4 sub-frame support parts 24 are provided to protrude downward, and a fixing tool, for example, first, second, or the like, is provided at the lower end of each of the first, second, third, and fourth sub-frame support parts 21, 22, 23, 24. The third and fourth mounting bolts 21a, 22a, 23a, and 24a connect the attachment points of the subframe 30 extending in the front-rear direction below the side frame 10, and the third subframe support portion 23 and the fourth subframe. A lower arm 28 of the front suspension is swingably supported by the support portion 24.
[0020]
The left and right sub-frames 30 are connected by a cross member 38 whose front end extends in the vehicle width direction, and is substantially straight and extends in the front- rear direction, and the rear end of the front side 30A via a bent portion 30a. A front inclined portion 30B that descends as it continuously moves rearward, an extended portion 30C that continues to the rear end of the front inclined portion 30B via the bent portion 30b and extends in the front-rear direction, and a bent portion 30c. The rear inclined portion 30D that continues to the rear end of the extending portion 30C and rises as it moves backward, and extends in the front-rear direction continuously to the rear end of the rear inclined portion 30D via the bent portion 30d. The rear side portion 30E is continuously formed, and the rear side portion 30E is coupled and supported by attachment bolts 25a and 25b to a fifth subframe support portion 25 formed on the side frame 10 in the vicinity of the lower end of the toe board 1.
[0021]
2 is determined by the shape of the subframe 30 when an impact load P of a predetermined value or more is applied from the front to the front end in a state where only the rear side portion is fixed. Compressive deformation is performed according to the deformation mode characteristics indicated by M1. That is, the stress concentrates on the bent portions 30a, 30b, 30c, and 30d to induce buckling deformation with the portion as an inflection point, and the rear side of the front side portion 30A is pushed up as the front end is retracted. The buckling portion 30a is retreated, and the front inclined portion 30B is raised, and the buckling portion 30b is pushed down to be retracted while being buckled.
[0022]
As the buckling portion 30b retreats, the extending portion 30C extending in the front-rear direction retreats, the buckling portion 30c is pushed backward, and the rear inclined portion 30D is raised to push up the buckling portion 30d. Will buckle and deform.
[0023]
Therefore, in the deformation mode characteristic M1 of its own due to the shape of the subframe 30, the amplitude is particularly large at the bent portions 30a, 30b, 30c, and 30d, which is a so-called abdomen. By suppressing the deformation amount of the bent portions 30a, 30b, 30c, and 30d serving as the abdomen, the deformation of the subframe 30 is suppressed, and the drag force against the impact load P acting on the front end of the subframe 30 is effectively increased. .
[0024]
Therefore, the first subframe support portion 21 that supports the subframe 30 is placed at a position corresponding to the rear end of the front side portion 30A that is in the vicinity of the bent portion 30a that is the inflection point of the subframe 30 itself. Extension of the third subframe support part 23 and the fourth subframe support part 24 in the vicinity of the bent part 30c at a position corresponding to the rear end of the front inclined part 30B that is in the vicinity of the bent part 30b. At the position corresponding to the rear end of the portion 30C, attachment points are set at positions corresponding to the front end of the rear side portion 30E in the vicinity of the bent portion 30d. 1st, 2nd, 3rd, 4th, 5th mounting bolts 21a, 22a, 23a, 24a, 25a and 25b respectively, 1st, 2nd, 3rd, 4th, 5th subframe support parts 21, 22 23, 24, 25 Attaching the support at the lower end.
[0025]
Next, the operation of the vehicle body front part structure configured as described above will be described with reference to FIG. 3 schematically showing FIG.
[0026]
When the impact load P from the front of the vehicle body acts on the front end of the subframe 30 and the front end of the subframe 30 moves backward, the subframe 30 has first, second, third, fourth, and fifth subframe support portions. Since 21, 21, 23, 24, and 25 are attached and supported on the side frame 10, the deformation of the subframe 30 is suppressed, and the resistance against the impact load P is ensured.
[0027]
On the other hand, the deformation part where the subframe 30 buckles due to the impact load P of a predetermined value or more, that is, the inflection point is between the first subframe support part 21 and the second subframe support part 22, and the second subframe support part 22. 3 and the third subframe support part 23, between the fourth subframe support part 24 and the fifth subframe support part 25, and schematically shows the structure in FIG. The deformation mode characteristics of the subframe 30 as shown are obtained.
[0028]
Since the subframe 30 has a deformation mode characteristic in a state where the subframe 30 is attached to and supported by the side frame 10, when an impact load P of a predetermined value or more acts on the front end of the subframe 30 from the front of the vehicle body, the subframe 30 is The first, second, third, fourth, and fifth subframe support portions 21, 22, 23, 24, and 25 are attached to and supported by the side frame 10 to secure a drag force. As shown in FIG. When input, the deceleration of the vehicle body gradually increases, and when the deceleration reaches a predetermined value, the deformation is brought about from the front end of the subframe 30 and the deceleration is controlled to be substantially constant, and then the inflection point. In other words, between the first subframe support portion 21 and the second subframe support portion 22 of the subframe 30, between the second subframe support portion 22 and the third subframe support portion 23, 4 deformation is initiated between the sub-frame supporting portion 24 and the fifth sub-frame support 25, the drag according to overall generation energy associated with deformation of each inflection point increases, i.e., the deceleration of the increase is obtained.
[0029]
Therefore, according to the present reference example , a plurality of subframe support portions arranged along the front-rear direction, that is, the first, second, third, fourth, and fifth subframe support portions 21, 22, 23, 24, 25, the subframe 30 is attached to and supported by the side frame 10 to suppress the occurrence of deformation, the resistance against the impact load P acting from the front on the front end of the subframe 30 is ensured, and the effective deceleration is ensured. .
[0030]
On the other hand, the deformation part generated in the subframe 30 based on the excessive impact load P, that is, the inflection point is between the first subframe support part 21 and the second subframe support part 22, and the second subframe support part 22. Deformation mode characteristics M2 set between the first subframe support section 23 and the fourth subframe support section 24 and the fifth subframe support section 25 are obtained. The energy generated due to deformation increases. Therefore, the drag force against the impact load of the subframe 30 is increased to effectively absorb the impact energy, and the deceleration can be continuously generated.
[0031]
As a result, it is possible to avoid problems such as the sudden decrease in deceleration due to buckling deformation at the intermediate portion of the subframe and the peak value of deceleration occurring instantaneously as shown in FIG. Further, since the rear end of the sub-frame 30 is held by the side frame 10, the behavior of the sub-frame 30 is suppressed, the deformation of the sub-frame 30 is eliminated, and the deformation mode characteristics due to the impact load of the sub-frame 30 are accurately determined in advance. Therefore, the subframe 30 can be easily designed.
[0032]
Further, by appropriately omitting the subframe support portions such as the second subframe support portion 22, the third subframe support portion 23, and the fourth subframe support portion 24, the deformation position that becomes the inflection point of the subframe 30 can be obtained. Decreasing or increasing the number of inflection points by increasing the number of subframe support portions changes the deformation mode characteristics and adjusts the drag.
[0033]
The implementation in the form of (the implementation of Embodiment) The present invention will be explained with reference to FIG. 5. In FIG. 5, the same reference numerals are given to the portions corresponding to those in FIG. 2, and detailed description thereof will be omitted. In the present embodiment, the third subframe support portion 23 and the fourth subframe support portion 24 are connected to the subframe support portion 24. The strength of the third and fourth mounting bolts 23a and 24a for mounting and supporting the frame 30 is set low.
[0034]
In such a vehicle, when the impact load P from the front of the vehicle body acts on the front end of the subframe 20, when the front end of the subframe 30 moves backward as in the reference example , the subframe 30 has the first, second, second Since the third, fourth, and fifth subframe support portions 21, 22, 23, 24, and 25 are attached to and supported by the side frame 10 and the occurrence of deformation is suppressed, the resistance against the impact load P is ensured.
[0035]
On the other hand, the deformation portion of the subframe 30 due to the impact load P exceeding the predetermined value, that is, the inflection point, is between the first subframe support portion 21 and the second subframe support portion 22 as in the reference example. When set between the frame support portion 22 and the third subframe support portion 23, between the fourth subframe support portion 24 and the fifth subframe support portion 25, and when the mounting bolts 23a and 24a are broken The support at the third subframe support part 23 and the fourth subframe support part 24 is released, and the deformation mode characteristic indicated by a two-dot chain line M3 is obtained.
[0036]
Since the subframe 30 has such a deformation mode characteristic in a state where it is attached and supported, when an impact load P of a predetermined value or more acts on the front end of the subframe 20 from the front of the vehicle body, the subframe 30 is first, The second, third, fourth, and fifth subframe support portions 21, 22, 23, 24, and 25 are attached and supported to the side frame 10 to secure the drag of the subframe 30, and as shown in FIG. When P is input, the deceleration of the vehicle body gradually increases, and when the deceleration reaches a predetermined value, the deceleration is controlled to be substantially constant due to the crushing deformation from the front end of the subframe 30.
[0037]
Thereafter, between the first subframe support 21 and the second subframe support 22 of the subframe 30, between the second subframe support 22 and the third subframe support 23, and the fourth subframe support. The deformation between the part 24 and the fifth subframe support part 25 is started, and the drag is increased and the deceleration is obtained according to the total generated energy accompanying the deformation of each inflection point. When deformed, the mounting bolts 23a, 24a set to low strength are broken, and the third and fourth subframe support portions 23, 24 are restrained between the second subframe support portion 22 and the fifth subframe support portion 25. The subframe 30 is buckled and deformed, and an increase in the drag of the subframe 30 is suppressed, and the deceleration is positively suppressed as shown by a one-dot chain line in FIG.
[0038]
Therefore, in addition to the reference example , the deceleration, that is, the resistance of the subframe 30 against the impact load P input to the subframe 30 from the front can be set by changing the strength of the mounting bolts 23a and 24a.
[0039]
Similarly, the deformation mode characteristics of the sub-frame 30 can be changed by changing the strength of the mounting bolt 22a that attaches and supports the sub-frame 30 to the second sub-frame support portion 22.
[0040]
Therefore, according to the present embodiment, by changing the strength of the mounting bolts 21a, 22a, 23a, 24a, 25a, 25b that support the subframe 30 on each of the subframe support portions 21, 22, 23, 24, 25, The deformation mode characteristics, that is, the deceleration can be adjusted without changing the subframe 30.
[0041]
The present invention is not limited to the above reference examples and embodiments, and various modifications can be made without departing from the spirit of the invention. For example, in the reference example and the embodiment described above, the subframe 30 is formed by the five subframe support portions of the first, second, third, fourth, and fifth subframe support portions 21, 22, 23, 24, and 25. Although attached to and supported by the side frame 10, the resistance against the impact load of the subframe 30, that is, the deceleration, can be changed and adjusted by appropriately increasing or decreasing the support of the subframe 30 by the subframe support portion.
[0042]
【The invention's effect】
According to the present invention, when the subframe is mounted and supported on the side frame at the mounting points distributed along the front-rear direction, the impact occurs on the side frame when an impact load acts on the front end of the side frame from the front. Deformation and behavior are suppressed, a resistance against an impact load acting on the subframe from the front is secured, and an effective deceleration is secured.
[0043]
In addition, the deformation part that occurs in the subframe due to excessive impact load is set between each attachment point, the energy generated due to deformation increases as the number of deformation parts increases, the resistance against impact load increases and continues Therefore, an effective deceleration can be obtained, and further, there is no variation in the deformation of the subframe, and it becomes easy to preset the deformation mode characteristics due to the impact load of the subframe.
[0044]
In particular, by supporting the inflection point of the deformation mode characteristic of the subframe itself on the side frame as an attachment point, deformation of the inflection point having a large deformation amount is suppressed, and more effective subframe characteristics can be secured. Further, by changing the strength of the fixture that attaches the subframe to the side frame, the deformation mode characteristic of the subframe in the attached state can be variably adjusted, and an effective subframe drag can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view of an essential part showing a reference example of the present invention.
FIG. 2 is a side view of FIG.
FIG. 3 is an operation explanatory view schematically showing FIG. 2;
FIG. 4 is a graph illustrating an impact absorption effect.
FIG. 5 is a side view showing a main part of the embodiment of the present invention.
FIG. 6 is a side view of an essential part of an automobile schematically showing a conventional subframe mounting support.
FIG. 7 is a plan view showing a main part of a conventional vehicle body front portion.
[Explanation of symbols]
10 Side frame 20 Suspension cross member 21 First subframe support (subframe support)
21a First mounting bolt (fixing tool)
22 2nd sub-frame support part (sub-frame support part)
22a Second mounting bolt (fixing tool)
23 Third sub-frame support (sub-frame support)
23a Third mounting bolt (fixing tool)
24 4th sub-frame support part (sub-frame support part)
24a Fourth mounting bolt (fixing tool)
25 Fifth subframe support (subframe support)
25a, 25b Fifth mounting bolt (fixing tool)

Claims (2)

In the front body structure of the vehicle in which the side frame extending in the longitudinal direction of the vehicle body and the subframe is attached and supported below the side frame in the longitudinal direction,
At least one attachment point for attaching to the side frame with a fixture is set on each of the front side portion of the subframe, the extension portion located in the intermediate region, and the rear side portion,
The front body structure of the vehicle characterized in that the strength of the fixture at the attachment point of the extending portion among the attachment points is set lower than the strength of the fixing portion at the attachment points of the front side portion and the rear side portion. . The subframe has a front inclined portion that descends as it moves rearward between the front side portion and the extension portion, and rises as it moves rearward between the extension portion and the rear side portion. The vehicle body structure according to claim 1, further comprising a rear inclined portion.

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