vehicle

Abstract

To suppress vibrations in the drive shaft. [Solution] The dynamic damper 8 is set such that the frequency fa at which the vibration level of the waveform W1 of the drive shaft 7 is minimized is lower than the resonant frequency fv caused by bending resonance of the drive shaft 7 when the dynamic damper 8 is not installed. The resonant frequency fv is the frequency at which the vibration level of the waveform W2 of the drive shaft 7 is maximized when the dynamic damper 8 is not installed. Furthermore, the dynamic damper 8 is set such that the high-frequency resonant frequency fb of the drive shaft 7 is higher than the frequency f1 of vibration that occurs when the engine speed in the normal operating range of the internal combustion engine 3 is at its maximum.

Description

Technical Field

[0001] The present invention relates to a vehicle in which a dynamic damper is attached to a drive shaft.

Background Art

[0002] For example, in Patent Document 1, in order to suppress resonant vibration at the resonance frequency of a vehicle component caused by vibration from a vibration source, a vehicle dynamic damper is disclosed that forms a resonance waveform having peaks where the vibration level with respect to the frequency of vibration is lower than the peak of the vibration level at the resonance frequency on both the low-frequency side and the high-frequency side by being attached to the vehicle component.

[0003] In Patent Document 1, the set frequency of the dynamic damper that causes a downward peak between the peak on the low-frequency side and the peak on the high-frequency side in the resonance waveform of the vehicle component is set to a lower frequency side than the resonance frequency. Here, the set frequency of the dynamic damper is the frequency at which a downward peak occurs in the waveform of the vibration level with respect to the frequency of the vehicle component by attaching the dynamic damper to the vehicle component.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, no consideration is given to the frequency characteristics of the vibration from the vibration source. That is, in a dynamic damper for reducing vehicle vibration, there is room for further improvement by considering the vibration generated according to the engine speed of the internal combustion engine that is the vibration source of the vehicle.

Means for Solving the Problems

[0006] The vehicle of the present invention has a dynamic damper attached to the drive shaft. The dynamic damper is set such that the frequency at which the vibration level waveform of the drive shaft vibration level is minimized when the dynamic damper is attached is lower than the resonant frequency caused by bending resonance of the drive shaft when the dynamic damper is not attached. The dynamic damper is set such that the high-frequency resonant frequency at which the vibration caused by bending resonance of the drive shaft peaks when the dynamic damper is attached is higher than the frequency of vibration that occurs when the engine speed of the internal combustion engine mounted on the vehicle is at its maximum in the normal operating range. [Effects of the Invention]

[0007] The vehicle is configured such that the high-frequency resonance frequency of the drive shaft, where vibrations peak due to bending resonance of the drive shaft when the dynamic damper is installed, is higher than the frequency of vibrations that occur when the engine speed is at its maximum in the normal operating range of the internal combustion engine. Therefore, drive shaft vibrations can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram illustrating the general outline of a vehicle drive system to which the present invention is applied. [Figure 2] A cross-sectional view showing an example of the structure of a dynamic damper attached to the drive shaft of a vehicle to which the present invention is applied. [Figure 3] An explanatory diagram showing the relationship between the frequency of vibrations occurring in the drive shaft and the magnitude of the vibration level occurring in the drive shaft. [Modes for carrying out the invention]

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 is a schematic diagram illustrating the general structure of the drive system of a vehicle 1 to which the present invention is applied. Figure 2 is a cross-sectional view showing an example of the structure of a dynamic damper 8 attached to the drive shaft 7 of a vehicle 1 to which the present invention is applied. Figure 3 is a diagram illustrating the relationship between the frequency of vibrations occurring in the drive shaft 7 and the magnitude of the vibration level occurring in the drive shaft 7.

[0010] Vehicle 1 is a so-called series hybrid vehicle having an internal combustion engine 3 for power generation that drives a generator 2, and a drive motor 5 that drives the drive wheels 4.

[0011] The internal combustion engine 3 is, for example, a three-cylinder in-line internal combustion engine. The driving force (rotational force) of the internal combustion engine 3 is transmitted to the generator 2 via a gear train (not shown) in the gearbox 6. In other words, the generator 2, the internal combustion engine 3, and the drive motor 5 are connected via a power generation gear train (not shown) in the gearbox 6. The electricity generated by the generator 2 is supplied to a battery (not shown) or the drive motor 5.

[0012] The driving force (rotational force) of the drive motor 5 is transmitted to the drive shaft 7, to which the drive wheels 4 are connected, via a drive gear train (not shown) and differential gear (not shown) in the gearbox 6. The drive shaft 7 then transmits the driving force (rotational force) from the drive motor 5 to the drive wheels 4. In other words, the drive motor 5 and the drive wheels 4 are connected to the left and right drive wheels 4a and 4b via a gear train (not shown) and differential gear (not shown) in the gearbox 6, and the left and right drive shafts 7a and 7b. The drive motor 5 is a motor generator capable of regenerative power generation.

[0013] Dynamic dampers 8 are attached to the left and right drive shafts 7a and 7b, respectively.

[0014] The dynamic damper 8 is a so-called spring-mass mechanism with a single degree of freedom, and is composed of a cylindrical elastic member 9 attached to the drive shaft 7 and a cylindrical mass body 10 attached to the outer circumference of the elastic member 9, as shown in Figure 2.

[0015] The elastic member 9 is a member having a predetermined spring constant, and is made of, for example, a rubber material. The mass body 10 is a member having a predetermined mass, and is made of, for example, a metal material.

[0016] Here, vibrations from the internal combustion engine 3 are transmitted to the drive shaft 7 via the gearbox 6. Therefore, the dynamic damper 8 is configured such that the spring constant of the elastic member 9 and the mass of the mass body 10 are set to suppress vibrations of the drive shaft 7.

[0017] More specifically, as shown in Figure 3, the dynamic damper 8 is set such that the frequency fa at which the vibration level waveform W1 of the drive shaft 7 is minimized when the dynamic damper 8 is installed is lower than the resonant frequency (natural frequency) fv caused by bending resonance of the drive shaft 7 when the dynamic damper 8 is not installed. The resonant frequency fv is the frequency at which the vibration level waveform W2 of the drive shaft 7 is maximized when the dynamic damper 8 is not installed. Furthermore, the dynamic damper 8 is set such that the resonant frequency (natural frequency) fb on the high-frequency side of the drive shaft 7, where the vibration caused by bending resonance of the drive shaft 7 peaks when the dynamic damper 8 is installed, is higher than the vibration frequency f1 that occurs when the engine speed of the internal combustion engine 3 is at its maximum value in the normal operating range. f1 is the frequency of the third-order booming sound when the engine speed of the inline 3-cylinder internal combustion engine 3 is, for example, 5000 rpm.

[0018] Here, f2 in FIG. 3 is the frequency of vibration generated when the engine speed in the normal operation range of a non-hybrid vehicle is at its maximum value, and is the frequency of the rotational third-order booming sound when the engine speed of the in-line three-cylinder internal combustion engine 3 is, for example, 7200 rpm. In a non-hybrid vehicle, since the operating point of the internal combustion engine changes according to the load, the internal combustion engine may be operated at a higher speed. F3 in FIG. 3 is the frequency of the rotational 1.5-order booming sound when the engine speed of the in-line three-cylinder internal combustion engine 3 is, for example, 5000 rpm. Fc in FIG. 3 is the resonance frequency (natural frequency) on the low-frequency side of the drive shaft 7 at which the vibration caused by the bending resonance of the drive shaft 7 in the state where the dynamic damper 8 is attached peaks.

[0019] The dynamic damper 8 is set such that the peak of the vibration at the resonance frequency fb on the high-frequency side caused by the bending resonance of the drive shaft 7 in the state where the dynamic damper 8 is attached is larger than the peak of the vibration at the resonance frequency fv caused by the bending resonance of the drive shaft 7 in the state where the dynamic damper 8 is not attached.

[0020] In the vehicle 1 of the above-described embodiment, the dynamic damper 8 is set such that the frequency fa at which the vibration level of the waveform W1 of the vibration level of the drive shaft 7 in the state where the dynamic damper 8 is attached becomes the minimum value is on the lower frequency side than the resonance frequency fv caused by the bending resonance of the drive shaft 7 in the state where the dynamic damper 8 is not attached.

[0021] When the vibration of the internal combustion engine 3 is transmitted to the drive shaft 7, by appropriately setting the vibration of the target frequency (fa in this embodiment) to be reduced by the dynamic damper 8 in this way, the peak of the resonance frequency fc on the low-frequency side can be reduced, and the vibration of the drive shaft 7 can be suppressed.

[0022] The dynamic damper 8 is set such that the frequency fa at which the vibration level of the waveform W1 of the vibration level of the drive shaft 7 becomes the minimum value is a low frequency, so that the effect of reducing the vibration of the drive shaft 7 due to an increase in the mass body 10 of the dynamic damper 8 can be obtained.

[0023] Also, when the dynamic damper 8 is set to reduce the vibration at the resonance frequency fv caused by the bending resonance of the drive shaft 7 in a state where the dynamic damper 8 is not attached, although the vibration at this resonance frequency fv is reduced, new vibration peaks (maximum values) will occur on the higher frequency side and the lower frequency side than this resonance frequency fv.

[0024] Here, the dynamic damper 8 of the above-described embodiment is set such that the resonance frequency fb on the higher frequency side of the drive shaft 7 where the vibration peaks due to the bending resonance of the drive shaft 7 in a state where the dynamic damper 8 is attached is higher than the frequency f1 of the vibration generated when the engine speed is at the maximum value in the normal use range of the internal combustion engine 3. Therefore, it is possible to avoid the vibration of the resonance frequency fb on the higher frequency side of the drive shaft 7 from becoming a problem, and overall, the vibration of the drive shaft 7 can be suppressed.

[0025] By setting the dynamic damper 8 such that the frequency fb at which the vibration peaks on the higher frequency side due to the bending resonance of the attached drive shaft 7 is higher than the frequency of the vibration caused by the internal combustion engine 3, the peak (maximum value) of the vibration level on the lower frequency side of the drive shaft 7 can be significantly reduced. This is because the dynamic damper 8 is set such that the frequency fa at which the waveform W1 becomes the minimum value is smaller than the resonance frequency fv.

[0026] Furthermore, if the internal combustion engine 3 is used solely for power generation, it is generally operated at a fuel-efficient operating speed and is never operated at high engine speeds (e.g., 5000 rpm or higher). Therefore, when the internal combustion engine 3 is installed in a vehicle solely for power generation, it is configured such that, for example, its maximum rotational speed does not exceed 5000 rpm. In other words, the upper limit of the engine speed in the normal operating range (usable range) for internal combustion engine 3 is less than 5000 rpm.

[0027] Therefore, vehicle 1 can easily make the natural value (natural frequency) of the drive shaft 7 to which the dynamic damper 8 is attached greater than the frequency of the booming sound from the internal combustion engine 3. In other words, the present invention is well-suited to being combined with the internal combustion engine 3 for power generation in order to reduce vibration of the drive shaft 7 and reduce noise inside the vehicle 1's cabin.

[0028] Although specific embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0029] For example, the internal combustion engine 3 may be an inline four-cylinder internal combustion engine. In this case, the dynamic damper 8 is set such that the high-frequency resonance frequency fb of the drive shaft 7, where vibration peaks due to bending resonance of the drive shaft 7 when the dynamic damper 8 is installed, is higher than the frequency of the second-order booming sound of the inline four-cylinder internal combustion engine.

[0030] Furthermore, the present invention is not limited to series hybrid vehicles, but is applicable to vehicles in which vibrations from the internal combustion engine 3 are transmitted to the drive shaft 7, and is applicable to non-hybrid front-wheel-drive vehicles, for example. [Explanation of Symbols]

[0031] 1…Vehicle 2…Generator 3…Internal combustion engine 4…Drive wheels 5…Drive motor 6…Gearbox 7…Drive shaft 8…Dynamic damper 9…Elastic member 10...mass body

Claims

1. The drive shaft transmits power to the drive wheels, It has a dynamic damper attached to the above drive shaft, The vehicle is characterized in that the dynamic damper described above is set such that the frequency at which the vibration level waveform of the drive shaft vibration level is minimized when the dynamic damper is installed is lower than the resonant frequency caused by bending resonance of the drive shaft when the dynamic damper is not installed, and the high-frequency resonant frequency at which the vibration caused by bending resonance of the drive shaft peaks when the dynamic damper is installed is higher than the frequency of vibration that occurs when the engine speed of the mounted internal combustion engine is at its maximum value in the normal operating range.

2. The vehicle according to claim 1, characterized in that the dynamic damper is set such that the peak of vibration at the high-frequency resonant frequency caused by the bending resonance of the drive shaft when the dynamic damper is installed is greater than the peak of vibration caused by the bending resonance of the drive shaft when the dynamic damper is not installed.

3. The vehicle according to claim 1, characterized in that the above-mentioned internal combustion engine is used exclusively for power generation, and the upper limit of the normally operated range of engine speed is less than 5,000 rpm.

4. The above internal combustion engine is a 3-cylinder in-line internal combustion engine. The vehicle according to claim 1, characterized in that the dynamic damper is set such that the high-frequency resonance frequency of the drive shaft, where vibration peaks due to bending resonance of the drive shaft when the dynamic damper is installed, is higher than the third rotational frequency of the internal combustion engine.

5. The above internal combustion engine is an inline four-cylinder internal combustion engine. The vehicle according to claim 1, characterized in that the dynamic damper is set such that the high-frequency resonance frequency of the drive shaft, where vibration peaks due to bending resonance of the drive shaft when the dynamic damper is installed, is higher than the second rotational frequency of the internal combustion engine.

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