JP4132428B2 - Method for manufacturing bracket for vehicle door mirror, and bracket for vehicle door mirror - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibration damping vehicle door mirror, more particularly, it relates to a bracket method of manufacturing a vehicle door mirror which can suppress the screen shake of the mirror during travel.
[0002]
[Prior art]
The vehicle door mirror can be roughly divided into two types depending on the mirror mounting mechanism. For example, a synthetic resin mirror housing on which the mirror is supported is directly attached to a metal stay made of aluminum die cast or the like fixed to the vehicle body. A bracket is attached to a metal stay made of a manually adjustable door mirror and an aluminum die cast fixed to the vehicle body via a metal shaft, and a mirror housing and a movable mirror are attached to the bracket. There are electrically adjustable door mirrors that are installed independently.
[0003]
The bracket used for the electric adjustment type door mirror requires durability that reliably supports the mirror housing and the movable mirror for a long period of time, and excellent mechanical strength that does not vibrate the mirror with respect to the vehicle body. Conventionally, a metal die cast or a bracket made of a synthetic resin having a flexural modulus of 1600 kg / mm ² or less has been adopted.
[0004]
[Problems to be solved by the invention]
However, in the case of the metal die-cast bracket, the durability and mechanical strength can be satisfied relatively easily, but since the molten metal is used, the die wear rate per shot is large, and therefore the die Has a short life of about 40,000 to 70,000 shots, and there is a problem that the manufacturing cost increases by frequently updating the mold.
[0005]
In addition, in the conventional bracket using a synthetic resin up to a bending elastic modulus of 1600 kg / mm ² , the life of the mold is extended, but a reinforcing rib is added in order to sufficiently satisfy the above durability and mechanical strength. Therefore, it is necessary to improve the elastic modulus by increasing the size, to reinforce by metal parts, to suppress vibration by adding a metal balancer, etc., and it is inevitable that the thickness and weight of the door mirror increase and the material cost increases.
[0006]
As described above, the conventional vehicle door mirror bracket is constructed by individually examining each element such as material selection, cross-sectional shape, rib arrangement, weight balance, etc. The synthetic resin bracket designed as above does not yet exist.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the present situation, and is intended to provide a bracket for a vehicle door mirror that is inexpensive, lightweight, compact, and can suppress screen blur of the mirror during vehicle travel.
[0008]
[Means for Solving the Problems]
As a result of diligent investigations to solve the above-mentioned problems, the present inventor found that the cause of the image blur of the mirror is the resonance phenomenon of the bracket caused by running vibration. As a restraining factor, the density (ρ) of the material used for the bracket, the flexural modulus (E), the secondary moment of inertia (I) calculated from the basic cross section of the bracket, and the cross sectional area (A) are closely related. I found it.
[0009]
The flexural modulus at this time is basically measured by the method shown in ASTM-D790. This is a rod-shaped sample injection molding said to be a bar test piece having a cross-sectional shape of approximately 12.7 mm in width and 6.2 mm in thickness, and maintained at a predetermined curing time (72 hours or more) at 23 ° C. and 50% relative humidity. In the same manner, the test piece was placed in a horizontal direction (6.2 mm in the height direction) at a pitch of 100 mm (metal-made) at 23 ° C. and 50% relative humidity. A metal part called a indenter (a semi-cylindrical shape with a width of 10 mm and a tip radius of 5 mm) at the center. Is used at a rate of 5 mm / min, the inclination is obtained from two bending stresses at 5 Kg and 15 Kg, and the elastic modulus is obtained.
[0010]
Furthermore, it was clarified that the following relationships exist among the various physical properties and coefficients.
[0011]
That is, when the periodic vibration transmitted from the vehicle body side is represented by acos ωt (a indicates the amplitude).
W (L) = a × (cosλ + coshλ) / (1 + cosλ · coshλ) (1)
If W (L) obtained by this equation (1) satisfies a resonance magnification of 20 times or less under the condition of a forced vibration frequency of 120 Hz or less, the screen shake during actual driving is sufficiently suppressed to the reference value or less. Can do it.
[0012]
Here, W (L) indicates a forced vibration response (a function representing a magnification of amplitude with respect to static deflection) of a portion separated by L from the fixed side when the periodic vibration acosωt is adopted as a steady forced vibration. Λ represents an eigenmode and is calculated by the following equation (2).
[0013]
λ = kL (2)
The k represents a spring constant of the bracket, and the spring constant is calculated by the following formula (3).
[0014]
k ⁴ = ω ² ρA / EI (3)
Ω at this time is the frequency of forced vibration, and is calculated by the following equation (4).
[0015]
ω = 2πf (4)
Further, f at this time is the frequency (unit: Hz) of the vehicle.
[0016]
Further, E is the flexural modulus of the synthetic resin composition forming the bracket, I is the secondary moment of section of the bracket, ρ is the density of the synthetic resin composition constituting the bracket, and A is the cross-sectional area of the bracket. .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail with reference to the accompanying drawings.
[0018]
By making the forced vibration response W (L) obtained by the above formulas (1) to (4) to be 20 times or less of the resonance magnification, the mold life used for manufacturing is longer than that of the metal die-cast bracket, Despite being made of a synthetic resin composition, it is possible to provide an inexpensive and compact door mirror with little screen blurring during vehicle travel. Synthetic resin brackets satisfying these formulas (1) to (4) can be easily obtained by the following method.
[0019]
First, the vibration in the bracket is most prominent at the position farthest from the fixed side, so L can be calculated as the distance from the fixed side to the tip in the bracket cross section. Further, as a vibration frequency on the vehicle body side, it is only necessary to examine the vibration of the vehicle up to about 120 Hz, and the resonance phenomenon of the third natural mode that appears in the vicinity of 70 to 90 Hz is particularly important.
[0020]
Moreover, the cross-sectional secondary moment (I) of the bracket is practically in the range of 4000 to 8000 mm ⁴ , and the cross-sectional area (A) is practically in the range of 350 to 550 mm ² . Therefore, in order to obtain the target synthetic resin bracket, the distance (L) from the fixed side to the tip in the bracket cross section, the secondary moment (I) of the cross section of the bracket, and the cross sectional area (A) are within practical ranges. By appropriately designing and producing a bracket by selecting a resin composition that satisfies the flexural modulus (E) and density (ρ) such that the resonance magnification is 20 times or less up to a forced frequency of about 120 Hz, It can be set as the vehicle door mirror by which the target screen blur was suppressed.
[0021]
1 to 3 show typical embodiments of a bracket for a vehicle door mirror according to the present invention, in which 1 is a door mirror and 6 is a bracket. FIG. 1 is a schematic exploded perspective view showing the structure of the door mirror 1. The electrically adjustable door mirror 1 has a bracket 6 attached to an aluminum die cast metal stay 8 fixed to a vehicle body via an aluminum die cast metal shaft 9, and ABS resin or AAS resin is attached to the bracket 6. And a movable mirror 7 which is tilted by an electric motor (not shown).
[0022]
As shown in FIG. 2, the bracket 6 has a dimension of height (h) = 129 mm, and the main rib is provided along the lateral direction. Therefore, the forced vibration response W (L) in the bracket 6 is considered. In this case, attention should be paid to the resonance magnification at the upper end 12 having the lower end 11 as a fixed end, and the distance (L) to the tip is h.
[0023]
Further, FIG. 3 showing the AA cross section in FIG. 2 can be regarded as a basic cross section having a uniform cross sectional shape along the height direction in the bracket 6. The moment (I) can be obtained as 7648.64 mm ⁴ and the cross-sectional area (A) as 471.6 mm ² . Here, the dimension (not shown) in FIG. 3 is 2 mm.
[0024]
When the flexural modulus (E) of the synthetic resin composition forming the bracket 6 is 1800 Kg / mm ² , the density ρ is 1.5 g / cm ³ , 1.78 g / cm ³ , 2 g / cm ^3. Each forced vibration response W (L) obtained by the above formulas (1) to (4) is as shown in FIG. From FIG. 4, if the density (ρ) of the synthetic resin material constituting the bracket 6 is 1.7 × 10 ⁻⁶ Kg / mm ³ or more, the forced vibration response W obtained by the equations (1) to (4) is obtained. It can be seen that a synthetic resin bracket with (L) having a resonance magnification of 20 times or less can be obtained.
[0025]
Further, when the density (ρ) of the synthetic resin composition forming the bracket 6 is 1.78 × 10 ⁻⁶ Kg / mm ³ , the flexural modulus (E) is 1500 Kg / mm ² , 1600 Kg / mm ² , Each forced vibration response W (L) obtained by the above formulas (1) to (4) set to 1800 kg / mm ² and 1900 kg / mm ² is as shown in FIG. From FIG. 5, if the bending elastic modulus (E) of the synthetic resin material constituting the bracket 6 is 1800 Kg / mm ² or more, the forced vibration response W (L) obtained from the equations (1) to (4) is resonant. It can be seen that a synthetic resin bracket having a magnification of 20 times or less can be obtained.
[0026]
As the synthetic resin composition having the above density (ρ) and longitudinal elastic modulus (E), reinforced polyethylene terephthalate containing 55 to 70% filler, polybutylene terephthalate, an alloy of polyethylene terephthalate and polybutylene terephthalate, Examples thereof include polypropylene and polyamide. Examples of the filler in this case include glass fiber, inorganic powder such as mica, charcoal cal, wollastonite, and talc, and carbon fiber.
[0027]
Since the bracket of the vehicle door mirror according to the present invention obtained as described above is formed of a synthetic resin material, it has a longer mold life at the time of manufacture than a metal die-cast product, and is made of a synthetic resin. Even in such a case, it is possible to provide an inexpensive and compact door mirror with less vibration during vehicle travel.
[0028]
【Example】
Hereinafter, the present invention will be described by way of examples. The vibration test performed in this example and the evaluation method thereof are as follows.
(Vibration test)
FIG. 6 is an explanatory view showing a method for evaluating the vibration of the door mirror employed in the present embodiment. As shown in the figure, the door mirror 1 is vibrated in the range of 0 to 120 Hz through a fixing jig, and the mirror 7 is moved from the mirror 7 to the position 0. Laser light is irradiated from the laser pointer 2 at a position 8 to 1 m away, and the reflected light is received by the screen 3 about 2 m away.
(Evaluation methods)
The amplitude of the light blur of the measurement light source 4 due to the reflected light received by the screen 3 is measured.
[0029]
In both Example 1 and Comparative Example 1, the bracket 6 having the cross-sectional shape shown in FIG. 3 described above is used, the cross-sectional secondary moment (I) is 7648.64 mm ⁴ , and the cross-sectional area (A) is 471.6 mm ² .
[0030]
And the synthetic resin composition used is shown below.
[0031]
That is, as the synthetic resin composition, in Example 1, 60% filler-reinforced polyethylene terephthalate having a flexural modulus of 1900 Kg / mm ² and a density of 1.88 × 10 ⁻⁶ Kg / mm ³ was used, and in Comparative Example 1, flexural elasticity was used. A 50% filler-reinforced polyethylene terephthalate having a rate of 1500 Kg / mm ² and a density of 1.78 × 10 ⁻⁶ Kg / mm ³ was used.
[0032]
Here, the forced vibration response obtained by the formulas (1) to (4) in the door mirror of the first embodiment has a resonance magnification of 12 times the third natural mode that appears at a forced frequency of about 75 Hz, as shown in FIG. Therefore, it is presumed that the light shake amplitude of the measurement light source in the actual vibration test sufficiently satisfies the above-mentioned criteria.
[0033]
In addition, the forced vibration response obtained by the equations (1) to (4) in the door mirror of Comparative Example 1 has a resonance magnification of the secondary eigenmode that appears at a resonance frequency of about 25 Hz as shown in FIG. The resonance magnification of the third-order eigenmode appearing at about 70 Hz is about 20 times, and it can be assumed that the amplitude of the light blur of the measurement light source by the actual vibration test does not satisfy the standard.
[0034]
The evaluation results are as follows.
(Example 1)
As shown in FIG. 9, the amplitude of light blur by an actual vibration test is about 13 mm at the maximum and sufficiently clears the standard “20 mm or less”.
(Comparative Example 1)
As shown in FIG. 10, the amplitude of light blur by an actual vibration test is about 22 mm at the maximum, which does not satisfy the above criteria and is not good.
[0035]
From the above, it is clear that the result of the formula (1) matches the result of the actual vibration test, and the forced vibration response W (L) obtained by the formulas (1) to (4) is a forced frequency of 120 Hz or less. It is apparent that the object of the present invention to obtain a vehicle door mirror that suppresses screen blur can be achieved by configuring a synthetic resin bracket that satisfies a resonance magnification of 20 times or less under the above conditions.
[0036]
【The invention's effect】
The bending elastic modulus of the synthetic resin composition constituting the bracket of the vehicle door mirror, its density, the moment of inertia of the cross section of the bracket, the cross sectional area, etc. By setting so as to satisfy the resonance magnification of 20 times or less under the conditions, it is possible to suppress the vibration of the mirror that hinders the rear visibility of the vehicle door mirror, that is, the screen shake, even with the synthetic resin bracket.
[0037]
Further, since it is made of synthetic resin, it is possible to use an injection mold having a long life, and the cost can be reduced by reducing the number of mold production surfaces.
[0038]
Furthermore, by reducing the reinforcing ribs, the vehicle door mirror can be easily made compact by flattening the bracket shape, and the cost can be reduced by reducing the amount of synthetic resin to be used.
[0039]
As such a synthetic resin composition, those having a density of 1.7 × 10 ⁻⁶ Kg / mm ³ or more and a flexural modulus of 1800 Kg / mm ² or more are suitable. Specific examples of such synthetic resin compositions include high filler reinforced thermoplastic resins, particularly reinforced polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate and polybutylene terephthalate alloys, polypropylene, polyamides containing 55-70% filler. Is mentioned.
[Brief description of the drawings]
FIG. 1 is a schematic exploded perspective view showing a structure of a door mirror according to a representative embodiment of the present invention.
FIG. 2 is a simplified front view showing an example of a bracket.
3 is a cross-sectional view taken along the line AA in the bracket of FIG. 2. FIG.
FIG. 4 is a graph showing the forced vibration response of the bracket obtained by the equations (1) to (4), in which the vertical axis represents amplitude magnification and the horizontal axis represents forced frequency.
FIG. 5 is a graph showing the forced vibration response of the bracket obtained by the equations (1) to (4), where the vertical axis indicates the amplitude magnification and the horizontal axis indicates the forced frequency.
FIG. 6 is an explanatory view showing a vibration evaluation method for a door mirror.
FIG. 7 is a graph showing the forced vibration response of the bracket obtained by the equations (1) to (4) in the door mirror of the first embodiment, where the vertical axis indicates the amplitude magnification and the horizontal axis indicates the forced frequency.
FIG. 8 is a graph showing the forced vibration response of the bracket obtained by the equations (1) to (4) in the door mirror of Comparative Example 1, where the vertical axis indicates the amplitude magnification and the horizontal axis indicates the forced frequency.
FIG. 9 is a graph showing the amplitude of light blurring by a vibration test in the door mirror of Example 1, where the vertical axis indicates the amplitude and the horizontal axis indicates the vibration frequency of the vibration exciter.
FIG. 10 is a graph showing the amplitude of light shake by a vibration test in the door mirror of Comparative Example 1, where the vertical axis indicates the amplitude and the horizontal axis indicates the vibration frequency of the vibration exciter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Door mirror 2 Laser pointer 3 Screen 4 Measurement light source 5 Mirror housing 6 Bracket 7 Mirror 8 Stay 9 Shaft 10 Upper end part 11 Lower end part h Height

Claims (4)

A method for manufacturing a bracket for a vehicle door mirror, wherein the bracket is formed from a synthetic resin composition, and a combination of materials and shapes satisfying the following conditions is selected:
Polyethylene reinforced with 55-70% filler, wherein the synthetic resin composition has a flexural modulus (E) of 1800 Kg / mm ² or more and a density (ρ) of 1.7 × 10 ⁻⁶ Kg / mm ³ or more. And at least one selected from the group consisting of terephthalate, polybutylene terephthalate, polyethylene terephthalate and polybutylene terephthalate alloy, and polypropylene , and
Its shape, Acosomegati on the fixed side (provided that, a magnitude, omega is the frequency of the forced vibration, when the frequency of the vehicle and f, ω = 2πf) when given periodic oscillations of fixed The following formula (1) at the other end away from the side by a distance L:
W (L) = a × (cosλ + coshλ) / (1 + cosλ · coshλ) (1)
[In the formula (1), λ is λ = kL and k ⁴ = ω ² ρA / EI (ρ is the resin composition density, A is the cross-sectional area of the bracket cross section, E is the flexural modulus of the resin composition, I Is a natural mode determined from the cross-sectional second moment of the cross-section). ]
Forced response W obtained from (L) is, Ru der resonance magnification 20 times or less in the case the frequency f is below 120Hz shape. ^2. The method for manufacturing a bracket for a vehicle door mirror according to claim 1, wherein the cross-sectional area (A) is in a range of 350 to 550 mm ^{2 and} the secondary moment (I) is in a range of 4000 to 8000 mm ⁴ . The bracket of the vehicle door mirror obtained using the manufacturing method of any one of Claim 1 or 2. The bracket of the vehicle door mirror according to claim 3, wherein the door mirror is used for a vehicle door mirror including a movable mirror whose electric angle is adjusted electrically.

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