JPH0717869Y2 - Viscous damper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a viscous damper used to suppress torsional vibration generated in a crankshaft of an internal combustion engine.

(Prior Art) Generally, in an in-line multi-cylinder internal combustion engine that corrects a crank shaft having a large axial dimension, particularly in an in-line multi-cylinder diesel engine in which an exciting torque applied to the crank shaft is large, torsional vibration occurs in the crank shaft. If the natural frequency of the crankshaft related to this torsional vibration coincides with the frequency of the exciting torque, resonance will occur and the amplitude of the vibration will increase, leading to an increase in engine noise or early torsional damage to the crankshaft. Problem occurs.

Therefore, in order to suppress the torsional vibration of the crankshaft,
A casing having an annular hollow chamber mounted on the crankshaft and rotating integrally with the crankshaft; and an annular inertial body housed in the annular hollow chamber with a small gap between the inner wall and the wall surface. Often, a viscous damper in which a viscous liquid such as silicon oil is sealed in a gap between the inner wall surface of the casing and the inertial body is adopted. This type of viscous damper converts the energy of the torsional vibration generated on the crankshaft by viscous resistance of viscous liquid such as silicon oil into heat energy and dissipates it to the outside through the casing to damp the vibration and suppress the vibration. Is what causes the.

(Problems to be Solved by the Invention) In recent years, as supercharging of internal combustion engines for vehicles has been progressing, further improvement of vibration damping performance of the viscous damper has been demanded. However, in the conventional viscous damper, since the torsional vibration is suppressed by the damping effect based on the viscous resistance of the viscous liquid enclosed in the casing, in order to further improve the vibration damping capability, the inertia contacting with the viscous liquid is required. It is necessary to increase the surface area of the body and increase the moment of inertia. As a result, the damper becomes large and it becomes difficult to secure a mounting space for the internal combustion engine. Also, the weight of the damper increases and the weight of the crankshaft increases. The burden becomes large, and problems such as bending of the crankshaft and easy breakage occur.

In order to solve the above-mentioned problems, the present applicant has previously shown that
In Japanese Patent Application No. 198354, as a viscous liquid such as silicone oil enclosed in a viscous damper, a so-called viscoelastic liquid having much higher viscosity than a conventional viscous liquid is used, and its viscous resistance and spring characteristics are used. It has been disclosed that a viscous damper having a small size and a light weight and excellent vibration damping performance can be realized. However, as a result of repeated trial research after that,
When using high viscosity silicone oil as the viscoelastic liquid,
Due to thermal deterioration that inevitably progresses during operation, the viscosity of silicone oil decreases relatively early, gradually approaching the viscous damper using conventional low-viscosity silicone oil, and accompanying vibration damping performance. Was confirmed to be gradually reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to ensure the durability of a viscous damper using the above-mentioned viscoelastic liquid of high viscosity.

(Means for Solving the Problems) The present invention was devised to achieve the above object, and includes a casing having an annular hollow chamber that is attached to a crankshaft and rotates integrally with the crankshaft; A damper having an annular inertial body housed in the hollow chamber with a small gap between it and the wall surface, and filling the gap between the inner wall surface of the casing and the inertial body with a high-viscosity viscous liquid. At the time of filling, the above high-viscosity viscous liquid is
℃) viscoelastic liquid, and the natural frequency fd of the damper
And the natural frequency ratio Λ expressed as the ratio of the natural frequency fe of the crankshaft system, and the damping ratio ζd expressed as Cd / 2Id × 2πfe when the damping coefficient of the damper is Cd and the inertial mass of the damper is Id. The gist is a viscous damper characterized by being set within the range of 0.8 ≦ Λ ≦ 1.1 0.3 ≦ ζd ≦ 0.45, respectively.

(Operation) As disclosed in detail in the above-mentioned proposed invention, when a viscous damper having a casing filled with viscoelastic liquid is mounted on a crankshaft, the torsional resonance peaks of the crankshaft system are equal to those of Sections I and II. It is divided into two resonance peaks. Then, by appropriately selecting the spring constant Kd and the damping coefficient Cd of the damper, the amplitudes of the section I and II resonance peaks are set to be substantially equal and low (hereinafter referred to as optimum amplitude).
The damping effect can be exerted in a wide frequency range.

According to the present invention, in the gap between the inner wall surface of the casing and the inertial body, 500 to 600,000 cst (at 25 ° C) at the time of encapsulation
Of the viscous damper and by setting the natural frequency ratio Λ and the damping ratio ζd of the viscous damper within the above range, the damper allows the amplitude of the crankshaft torsional vibration in terms of strength in its initial state. The vibration amplitude is sufficiently smaller than the possible limit amplitude (hereinafter referred to as the allowable limit amplitude) but larger than the above-mentioned optimum amplitude, and the viscoelastic liquid gradually deteriorates during operation and its viscosity decreases. As a result, the vibration is damped to the optimum amplitude, and even if the viscoelastic liquid deteriorates and its viscosity further decreases, it is sufficiently smaller than the allowable limit amplitude but larger than the optimum amplitude. It operates so as to suppress vibration, and as a result of this, it is possible to sufficiently lengthen the entire operation period in which the torsional vibration amplitude of the crankshaft can be suppressed to a safe amplitude smaller than the allowable amplitude.

(Embodiment) First, in FIG. 1, reference numeral 10 generally indicates a viscous damper, which is a disk-shaped damper plate 12 mounted on a shaft end portion of a crankshaft of an internal combustion engine, and the plate 12.
And a casing 16 having an annular hollow chamber 14 having a rectangular cross section integrally formed on the outer peripheral portion of the casing. Above casing
Inside the 16, small gaps between the casing wall and hi, ho
, And hs are retained, the annular inertial body 18 of rectangular cross section is stored,
A high-viscosity viscoelastic liquid 20 is sealed in the gap between the casing 16 and the inertial body 18. Silicon oil, which has excellent heat resistance, is suitable for the viscoelastic liquid, and its viscosity is 500,000 to 600,000.
cst (at 25 ° C). Further, spacers 22 for positioning the inertial body 18 in the casing 16 are mounted on both sides of the inner circumference of the inertial body 18, and the spacers 22 are provided in the casing 16.
It has a function of preventing direct contact between the inertial body 18 and.

By the way, in the conventional viscous damper, since a viscous liquid having a relatively low viscosity, for example, a viscosity of about 100,000 cst (at 25 ° C) was used, the elastic effect of the viscous liquid was hardly obtained, and the viscous resistance of the viscous liquid was not obtained. Although the torsional vibration was suppressed by the damping effect due to, in the present invention, as described above,
Since 600,000 cst (at 25 ° C) of high viscosity silicone oil is used, the damping effect by viscous resistance and the vibration damping effect by elasticity coexist, and the vibration damping is performed by both of them.
Therefore, the crankshaft system equipped with the viscous damper 10 shown in FIG. 1 can be represented by an equivalent vibration model of a two-degree-of-freedom system as shown in FIG. In the figure, Id is the moment of inertia of the damper 10, Kd is the spring constant of the damper, and Cd
Also indicates a damping coefficient, Ie indicates a combined moment of inertia of the entire crankshaft system excluding the damper 10, Ke indicates a spring constant of the crankshaft system, and Ce indicates a damping coefficient.

Next, FIG. 3 shows the relationship between the resonance frequency and the amplitude of the resonance peak vertices of Sections I and II with the natural frequency ratio Λ and the damping ratio ζd of the viscous damper 10 as parameters, and the horizontal axis indicates the frequency ratio. λ is taken, and the vertical axis is the amplitude θ of the crankshaft torsional vibration.
It is the diagram which took and showed. The natural frequency ratio Λ is the ratio of the natural frequency d of the damper 10 and the natural frequency e of the crankshaft system, that is, Λ = d / e, Is. Further, the damping ratio ζd is expressed by the following equation.
I.e. Further, in the figure, P is the point where the damping ratio ζd of the damper is zero, and therefore the damping coefficient Cd is zero, which coincides with the resonance peak of the crankshaft system without mounting the damper, and Q is the damping ratio ζd of the damper. Infinity, that is, in FIG. 2, the crankshaft system and the inertial mass of the damper are integrated. By installing the viscous damper 10, the torsional resonance peak of the crankshaft system is divided into two resonance peaks of section I and section II.
The positions of the resonance peak vertices of the node are separated into left and right with λ = λ _Q (λ _Q represents the resonance frequency at the point Q) as a boundary line. In the viscous damper of the present invention, the natural frequency ratio Λ
Is set in the range of 0.8 to 1.1, and the damping ratio ζd is 0.3 to
It is set to a range of 0.45, that is, to be included in a region R shown by hatching in FIG.

FIG. 4 is a line showing the relationship between the viscosity of the silicone oil enclosed in the viscous damper and the crankshaft torsional vibration amplitude, with the vertical axis representing the amplitude of torsional vibration θ and the horizontal axis representing the vibration frequency. In the figure, θ _L shown by the alternate long and short dash line in the figure is an allowable limit swing that is allowable in terms of the strength of the crankshaft. Silicon oil of the viscous damper 10 included in the region R of FIG. 3 has a high viscosity of, for example, 600,000 cst (at 25 ° C.) in the initial state, and at this time, the peak of the resonance peak is point A of FIG.
It is sufficiently lower than the allowable limit amplitude θ _L and safe. When operating for a long time, the encapsulated silicone oil gradually deteriorates and its viscosity decreases. For example, when the viscosity reaches 300,000 cst (at 25 ° C), the peak of the resonance peak becomes point B, which is the minimum value that is approximately equal to the optimum swing. Silicon oil deteriorates and its viscosity is 100,000 cst (at2
When the temperature drops to 5 ° C), the peak of the resonance peak becomes point C, which is sufficiently lower than the allowable limit amplitude θ _L and still safe.
That is, the viscous damper has a resonance peak apex A-B-C as shown by a dotted line in FIG.
It is possible to exert the vibration damping effect safely with a sufficiently long durability from the initial point A to the final point C. This will be described with reference to FIG. 3. The viscous damper 10 whose resonance peak is included in the region R in the initial state in the initial state is accompanied by a decrease in viscosity due to the deterioration of the silicone oil, and therefore two dotted lines are shown in the figure. S ₁ , S ₂
It operates while drawing the locus of the resonance peak that gradually moves from the left to the right in the region limited by, and can operate safely for a long period of time while exerting a sufficient damping effect as a whole.

(Effect of the Invention) As described above, the viscous damper according to the present invention includes a casing having an annular hollow chamber attached to a crankshaft and rotating integrally with the crankshaft, and a wall surface of the casing in the annular hollow chamber. A damper comprising an annular inertial body stored with a small gap between them, wherein the gap between the inner wall surface of the casing and the inertial body is filled with the high-viscosity viscous liquid. Is a viscoelastic liquid of 500 to 600,000 cst (at 25 ° C) at the time of filling, and the natural frequency ratio Λ expressed as the ratio of the natural frequency fd of the damper and the natural frequency fe of the crankshaft system, and the damper Is the damping coefficient of Cd and the inertial mass of the damper is Id
Then, the damping ratio ζd represented by Cd / 2Id × 2πfe is
Each of them is set in the range of 0.8 ≦ Λ ≦ 1.1 0.3 ≦ ζd ≦ 0.45, and there is an advantage that a viscous damper having excellent durability can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part showing an embodiment of a viscous damper of the present invention, FIG. 2 is an explanatory view of an equivalent vibration model of a crankshaft equipped with the viscous damper of FIG. 1, and FIG. 3 is a motion of the viscous damper. FIG. 4 is a diagram showing the relationship between the characteristics and the amplitude and frequency of the torsional resonance peak, and FIG. 4 is a diagram showing the relationship between the viscosity of the silicone oil enclosed in the viscous damper and the amplitude of the torsional vibration. 10 …… Viscous damper, 14 …… annular hollow chamber, 16 …… Casing, 18 …… Inertia, 20 …… Silicon oil (viscoelastic liquid).

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A casing having an annular hollow chamber attached to a crankshaft and rotating integrally with the crankshaft; and an annular inertia housed in the annular hollow chamber with a small gap between its wall surface. In a damper that comprises a body and is filled with a high-viscosity viscous liquid in the gap between the inner wall surface of the casing and the inertial body, the high-viscosity viscous liquid has a capacity of 500 to 600,000 cs at the time of filling.
A natural frequency ratio Λ, which is a viscoelastic liquid of t (at 25 ° C) and is expressed as a ratio between the natural frequency fd of the damper and the natural frequency fe of the crankshaft system, and the damping coefficient of the damper is Cd, A viscous damper characterized in that the damping ratio ζd represented by Cd / 2Id × 2πfe when the inertial mass is Id is set within a range of 0.8 ≦ Λ ≦ 1.1 0.3 ≦ ζd ≦ 0.45.