Rotary damper

Details Rotary damper Rotary damper

1998-12-17

2000-08-08

Oberleitner, Robert J.

Brakes

Internal-resistance motion retarder

Using a rotary-type fluid damper

188307, F16D 5700

Patent

active

060987650

DESCRIPTION:

BRIEF SUMMARY
1. Technical Field
The present invention relates to a rotary damper used in a vehicular suspension system for generating a suspension force (damping force) against an external input in its pivotal direction.
2. Technical Background
A Japanese Patent Application First (Tokkai) Publication No. Heisei 3-96727 exemplifies a conventional rotary damper.
In the conventional rotary damper, a stationary vane and a swingable vane are disposed within a casing. Two pressure chambers are defined between the stationary vane and the swingable vane, the two pressure chambers being communicated via a bypass circuit. In the bypass circuit, a first circuit including a check valve and a damping valve and a second circuit including another damping valve and another check valve are disposed in parallel to each other.
Hence, when the swingable vane is pivoted, an oil within one of the pressure chambers is caused to flow into the other pressure chamber via the damping valve. However, due to a resistance when the damping valve is opened, a differential pressure between both pressure chambers is generated and, due to the differential pressure, the suspension force (damping force) is acted upon the pivotal movement of the swingable vane.
However, in the conventional rotary damper described above, both pressure chambers are disposed at portions nearest to an axial core portion of a pivotal axis and oil pressures of both pressure chambers become high and a sealing characteristic on a slide surface between the casing and the swingable vane becomes extremely difficult.
When a considerably high damping force is generated, a leakage of oil is increased and their internal pressure cannot be higher.
That is to say, a leakage Q [cm.sup.3 /s] in a gap is generally expressed as the leakage Q(=b.multidot.h.sup.3 /12 .mu..multidot.L).multidot.(P.sub.1 -P.sub.2)+(b.multidot.h)/U - - - (1).
In the equation (1), (P.sub.1 -P.sub.2) denotes a pressure difference, .mu. denotes a fluid viscosity, h denotes a gap, U denotes a movement velocity of a lower plate, b denotes a width of a flat plate, and L denotes a length of the gap h.
As appreciated from the equation (1), when the pressure difference (P.sub.1 -P.sub.2) is enlarged to generate the high damping force, the leakage Q is so large that a predetermined damping force characteristic cannot be achieved.
There are conceivably two methods to reduce the leakage Q: 1 a reduction in the gap length h; or 2 an increase in the fluid viscosity .mu..
However, since a high dimensional accuracy is required for a sealing portion in order to 1 reduce the gap length h, a working cost is accordingly increased.
In addition, 2 when an oil having a high fluid viscosity .mu. is used, a throttling at the damping valve portion provides a laminar stream throttling due to the presence in the high viscosity oil so that a temperature characteristic is worsened and a variation rate in the damping force characteristic due to the variation in temperature becomes large.
With the above-described conventional problems in mind, it is an object of the present invention to provide a rotary damper which can suppress a working cost to be lowered without requirement of a high dimensional accuracy in a seal portion and which can reduce the characteristic variation of the damping force due to the temperature variation.


DISCLOSURE OF THE INVENTION

The above-described object can be achieved by providing a rotary damper comprising: a pressure generating mechanism portion including a casing, a stationary vane fixed on an inner peripheral surface of the casing, and a pivotably installed swingable vane, at least one pair of pressure chambers being defined and formed between the stationary vane and the pivotably installed swingable vane so that when a volume of one of the pressure chambers is increased due to a pivotal movement of the swingable vane, the volume of the other pressure chamber is decreased, and within which a fluid is filled; a damping force generating mechanism portion including damping force generating means, interposed in a m

REFERENCES:
patent: 2028164 (1936-01-01), Peo
patent: 2678115 (1954-05-01), Loe
patent: 5305858 (1994-04-01), Haga et al.
patent: 5810129 (1998-09-01), Hanawa et al.

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