JP2005199861A - Suspension device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the maximum value of engine vibration transmitted from a suspension to a vehicle body. <P>SOLUTION: Non-suspended system resonance frequencies of a front right wheel and a front left wheel are made different from each other. More specifically, when a vehicle body bending resonance frequency is high, a frequency smaller than the bending resonance frequency and equivalent to the minimum value of a vehicle body sensitivity is employed as a non-suspended system resonance frequency of one of the wheels prominent in evaluation of vehicle body vibration. The non-suspended system resonance frequency of the other wheel is set to a value between the non-suspended system resonance frequency of the one wheel and an engine rigidity resonance frequency lower than the former. The non-suspended resonance frequency is adjusted by adjusting the rigidity of a strut upper mount insulator, for example. With this arrangement, the suspended system spring characteristics and the non-suspended system spring characteristics of the right and left wheels when a large displacement is inputted can be equalized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a suspension device for a vehicle, and is particularly suitable as a suspension device for a front wheel.

The vibration of the engine during idling is roughly divided into those transmitted to the vehicle body via the engine mount and those transmitted to the vehicle body via the suspension. Among these, as a means for suppressing vibration transmitted to the vehicle body via the suspension, for example, among suspension apparatuses for the front wheels, there is one provided with a vibration isolating device on the strut upper mount (for example, Patent Document 1). This anti-vibration device is a so-called active mount device that cancels out the phase of the newly introduced force by interference, and detects an anti-vibration mechanism comprising a diaphragm, a partition, a pressure chamber, etc., and vibration (phase) input to the vehicle body. The sensor includes a controller and a controller that causes the vibration isolation mechanism to generate vibration having a phase opposite to that of the vibration detected by the sensor.
JP 2000-168332 A

However, the conventional apparatus is not only large and complicated, but also has problems of cost and weight increase. Moreover, since the vibration isolating mechanism is provided on the strut upper mount, there is a problem that a gap with the hood (also referred to as a bonnet) is reduced.
The present invention has been made paying attention to the above-described problems, and an object of the present invention is to provide a suspension device that has a simple structure and can secure a gap with a hood.

  In order to solve the above-described problem, the suspension device of the present invention is characterized in that the unsprung resonance frequency of the front wheels when the engine is idling is different between the left and right wheels.

  Thus, according to the suspension device of the present invention, the unsprung resonance frequencies of the front left and right wheels are superposed by making the unsprung resonance frequencies of the front wheels different when the engine is idling. In other words, the maximum value of vibration transmitted from the engine to the vehicle body via the suspension (strut) can be reduced.

Next, an embodiment of the suspension device of the present invention will be described with reference to the drawings.
FIG. 1 shows a strut upper mount of a suspension device according to the present embodiment. FIG. 1a shows a front right wheel, and FIG. 1b shows a front left wheel. Among the strut upper mounts, for example, shock absorbers 2 and coil springs 3 other than the mount insulator 1 are equivalent to the front left and right wheels. That is, only the mount insulator 1 is different between the front left and right wheels. Specifically, the shape of the lower portion of the insulator is different, and the front right wheel shown in FIG. 1a is thicker, whereas the front left wheel shown in FIG. 1b is thinner. As a result, the deflection-load characteristic of the mount insulator 1 differs between the front left and right wheels in a region where the deflection, that is, a small displacement, as shown in FIG. However, for example, the front left-wheel mount insulator 1 shown in FIG. 1b also has a large displacement because the thin-walled portion has the same deflection-load characteristics as the thick-walled mount insulator 1 shown in FIG. 1a. In the area, the front left and right wheels show the same behavior.

  As shown in FIG. 3, the unsprung resonance frequency of the suspension when the engine is idling is changed to the front left and right, as shown in FIG. It could be different in a circle. Specifically, for example, the unsprung resonance frequency of the front right wheel during engine idle operation is about 28 Hz, and the unsprung resonance frequency of the front left wheel is about 25 Hz.

  There are two types of paths through which engine vibration is transmitted to the vehicle body: a path directly input from the engine mount and a path input from the drive shaft via the suspension device. Since the vibration transmitted from the suspension device to the vehicle body is amplified by the unsprung vertical resonance of the front suspension, a vibration peak is formed at the unsprung resonance frequency. The vehicle body vibration level is determined by the transmission force from the suspension to the vehicle body and the vehicle body sensitivity (for example, the vehicle body vibration response to the strut upper mount attachment point input). In the case of the present embodiment, as shown in FIG. 4, the vehicle body (floor in the figure) vibration component input from the front right wheel is larger than the vehicle body vibration component input from the front right wheel. Car body vibration evaluation is performed using. In the case of the present embodiment, the unsprung resonance frequencies of the front left and right wheels are deviated from each other, so that they are not overlapped with each other, and the peak of the total input from the suspension during engine idle operation is relatively small.

  On the other hand, FIG. 5 shows vibration characteristics when the front left and right wheel suspension devices are exactly the same. In this case, in principle, the unsprung resonance frequencies of the front left and right wheels are the same, and in this example, both are 25 Hz. As a result, the same-phase vehicle body vibrations at the unsprung resonance frequencies of the front left and right wheels are superposed, and the peak of the total input during engine idle operation becomes large.

  Further, when setting the unsprung resonance frequencies of the front left and right wheels, engine rigid body resonance and vehicle body bending resonance should be considered. FIG. 6 shows frequency characteristics of general engine rigid body resonance and vehicle body bending resonance. Since the engine vibration that becomes the vibration generating force is amplified by engine rigid body resonance, if the engine rigid body resonance frequency is within the generated vibration frequency band during engine idle operation, the engine vibration itself increases. This engine rigid body resonance is determined by the engine itself and the engine mount. On the other hand, the vehicle body bending resonance is a vibration mode in which the vehicle body vibrates like a wave. In this embodiment, the engine rigid body resonance frequency can be removed from the generated vibration frequency band during engine idle operation by tuning the engine itself and the engine mount. The resonance frequency was not made the same. Considering this vehicle body bending resonance, for example, as shown in FIG. 7a, there is a minimum value of vehicle body sensitivity where the vehicle body bending resonance frequency is several Hz lower. The vehicle body sensitivity here means the vehicle body vibration response to the strut upper mount attachment point input. Therefore, in this embodiment, as shown in FIG. 7B, the frequency at which the vehicle body vibration response is minimized is set to the unsprung resonance frequency of the front right wheel that is dominant in the vehicle body vibration. The unsprung resonance frequency of the other front left wheel was set between the unsprung resonance frequency of the front right wheel and the engine rigid body resonance.

  In FIG. 8, the comprehensive evaluation result of the vehicle body vibration of this embodiment is shown. FIG. 8a shows the vibration of the vehicle body right floor, and FIG. 8b shows the vibration of the vehicle body left floor. Curve α in the figure is the same when the unsprung resonance frequency of the front left and right wheels is the same, and curve γ is a value obtained by making the unsprung resonance frequency of the front right wheel larger than the unsprung resonance frequency of the front left wheel as described above. Curve β is a comparative example in which the unsprung resonance frequency of the front left wheel is larger than the unsprung resonance frequency of the front right wheel, and any unsprung resonance frequency overlaps with the vehicle body bending resonance or the engine rigid body resonance. Not. As is clear from the figure, the peak level of the vehicle body vibration is minimized when the unsprung resonance frequency of the front right wheel is made larger than the unsprung resonance frequency of the front left wheel on both the right and left floors of the vehicle body. be able to. This is because, as described above, in this embodiment, the vibration input from the front right wheel is dominant for the vehicle body vibration evaluation. However, compared with the same, the front left and right wheels have the same unsprung resonance frequency. Even when the unsprung resonance frequency of the front left wheel is larger than the unsprung resonance frequency of the front right wheel, the peak level of vehicle body vibration can be reduced. ing. Therefore, in the suspension device of the present invention, the maximum value of the vehicle body vibration during engine idle operation can be reduced by making the unsprung resonance frequencies of the front left and right wheels different.

In addition, vibrations amplified by resonance are set by setting the unsprung resonance frequencies of the different front left and right wheels between the vehicle body bending resonance frequency during engine idle operation and the engine rigid body resonance frequency determined by the engine and the engine mount. Are not superposed on each other, and the maximum value of the vehicle body vibration during engine idling can be reliably reduced.
In addition, one of the resonance frequencies of the different front left and right wheels is set to a frequency that is smaller than or near the vehicle body bending resonance frequency during engine idle operation and has a minimum vehicle body sensitivity, and one of the other front and rear wheels has a minimum vehicle body sensitivity. The maximum value of the vehicle body vibration during the engine idle operation can be further reduced by setting between the above-described frequency and the engine rigid body resonance frequency.

Also, by making the vertical spring characteristics of the strut upper mount insulator different between the front left and right wheels, the unsprung resonance frequencies of the front left and right wheels during engine idle operation are made different, so the structure is simple and reliable. The maximum value of body vibration during handling can be reduced.
In addition, by making the vertical spring characteristics of the front left and right wheels the same or approximately the same when a large displacement is input, the suspension characteristics of the front left and right wheels can be made equivalent to a large displacement input such as a lane change or overhang of a protrusion. .

It is a longitudinal cross-sectional view of the strut upper mount which shows one Embodiment of the suspension apparatus of this invention, (a) is a thing of a front right wheel, (b) is a thing of a front left wheel. FIG. 2 is a deflection-load characteristic diagram of a mount insulator of the strut upper mount of FIG. 1. FIG. 2 is a vehicle vibration level frequency characteristic diagram of front left and right wheels of FIG. 1. It is a vehicle body vibration level frequency characteristic figure by the suspension apparatus of FIG. It is a vehicle body vibration level frequency characteristic view by a suspension apparatus with the same unsprung resonance frequency of front left and right wheels. It is a frequency characteristic figure of engine rigid body resonance and body bending resonance. It is explanatory drawing of the setting of the unsprung resonance frequency of a front left-right wheel with respect to vehicle body bending resonance. It is a vehicle body vibration level frequency characteristic figure by the suspension apparatus of FIG.

Explanation of symbols

1 is a mount insulator 2 is a shock absorber 3 is a coil spring

Claims (5)

  A suspension device, wherein the left and right wheels have different unsprung resonance frequencies when the engine is idling.   A suspension device, wherein the unsprung resonance frequencies of the different front left and right wheels are set between a vehicle body bending resonance frequency during engine idle operation and an engine rigid body resonance frequency determined by the engine and the engine mount.   Any one of the unsprung resonance frequencies of the different front left and right wheels is set to a frequency that is smaller than the vehicle body bending resonance frequency during the engine idle operation and has a minimum vehicle body sensitivity, or the vicinity thereof. The suspension apparatus according to claim 2, wherein the suspension apparatus is set between a minimum frequency and the engine rigid body resonance frequency.   4. The unsprung resonance frequency of the front left and right wheels during engine idle operation is made different by making the vertical spring characteristics of the strut upper mount insulator different between the front left and right wheels. The suspension device according to claim 1.   The suspension device according to claim 4, wherein the vertical spring characteristics of the front left and right wheels when a large displacement is input are made equal or substantially equal.

Images