Rotary shafts – gudgeons – housings – and flexible couplings for ro – Electrical or magnetic coupling
Reexamination Certificate
1999-09-24
2001-10-02
Browne, Lynne E. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Electrical or magnetic coupling
C464S057000, C192S084961
Reexamination Certificate
active
06296572
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a power transmission mechanism for connecting a drive source to a driven apparatus, which includes a rotating member. More particularly, the present invention pertains to a power transmission mechanism used in a compressor of a vehicle air conditioner.
BACKGROUND ART
A compressor used in a vehicle air conditioner includes a drive shaft and an inner compression mechanism. The compression mechanism is actuated by rotation of the drive shaft. The compressor also includes an electromagnetic clutch to transmit power from the vehicle's engine to the drive shaft. The clutch is engaged and disengaged based, for example, on the cooling load in an external refrigerant circuit. A typical electromagnetic clutch includes a pulley, an armature and a coupling member. The coupling member connects the armature to an inner hub, which is located at the distal end of the drive shaft. The armature is selectively engaged with and disengaged from the pulley. When the clutch is electromagnetically engaged, engine power is transmitted to the drive shaft by a belt, the pulley, the armature, the coupling member and the inner hub. The coupling member, which is supported by the inner hub, separates the armature from the pulley when the electromagnetic force of the clutch is stopped. Rubber dampener (rubber hub) type and a leaf spring type coupling members are known in the art. The leaf springs used in leaf spring type coupling members are practically ineffective as dampeners.
If a coupling member for coupling an armature with an inner hub is made of rubber, torque fluctuation in the compressor is absorbed by the rubber, which serves as a dampener. However, the coupling member must function not only as a dampener but also as a torque transmitting member. Thus, the spring constant of the rubber must be relatively high to make the coupling member durable. The resonance frequency is determined by the moment of inertia of rotation system of the compressor and the spring constant of the rubber. When the spring constant of the rubber is high, the resonance frequency tends to be higher than the lowest frequency of torque fluctuation generated in the rotation system of the compressor. A typical compressor operates at 1000 rpm to 2000 rpm. If the frequency of torque fluctuation of the compressor substantially matches the resonance frequency when the compressor is operating in a normal speed range, resonance occurs and increases the torque fluctuation. The increased torque fluctuation produces noise in the vehicle.
Using leaf springs, in comparison to rubber, to couple the armature and the inner hub increases the resonance frequency. Further, the leaf springs are ineffective as dampeners. Thus, when resonance occurs, torque fluctuation is excessive, which results in seizing and wearing of contact surfaces of the electromagnetic clutch.
An objective of the present invention is to provide a power transmission mechanism that suppresses vibration and noise due to torque fluctuation and prevents the inner parts of the compressor from being damaged.
DISCLOSURE OF THE INVENTION
The present invention relates to a power transmission mechanism that couples a drive source with a rotating member of a driven apparatus. The power transmission mechanism includes a first rotor, a second rotor and elastic means. The first rotor is provided in the drive source. The second rotor is provided in the driven apparatus and is coupled to the rotating member. The elastic means couples the first rotor with the second rotor.
(1) The resonance frequency (fR) is determined based chiefly on the spring constant of the elastic means and the sum of the moment of inertia of the rotating member in the driven apparatus and the moment of inertia of the second rotor. According to a power transmission mechanism of a first invention, the spring constant of the elastic means is determined such that the resonance frequency (fR) is lower than the lowest frequency (f1) of torque fluctuation of the driven apparatus (fR<f1).
The first rotor, the elastic member and the second rotor not only form a power transmission system from the drive source to the driven apparatus, but also a vibrating system, which includes the driven apparatus. When power from the first rotor, which is coupled to the drive source, is transmitted to the second rotor, which is coupled to the driven apparatus, the rotating member of the driven apparatus receives a load. The load generates repulsion load torque. Depending on the type of the driven apparatus, the load and the repulsion load torque fluctuate periodically. However, according to the first invention, the spring constant of the elastic means is carefully selected such that the resonance frequency (fR), which is determined based chiefly on the spring constant of the elastic means and the sum of the moment of inertia of the rotating member of the driven apparatus and the moment of inertia of the second rotor, is lower than the lowest frequency (f1) of torque fluctuation generated in the driven apparatus. In other words, the resonance frequency (fR) is outside of the frequency range of torque fluctuation generated in the driven apparatus. Therefore, for any torque fluctuation in the driven apparatus, the amplitude of the torque fluctuation is not increased by resonance (resonance phenomena) due to the mechanical characteristics of the power transmission system. As a result, excessive noise and damage in the rotation system due to torque fluctuations of the driven apparatus are prevented.
(2) The resonance frequency (fR) is determined based chiefly on the spring constant of the elastic means and the sum of the moment of inertia of the rotating member of the driven apparatus and the moment of inertia of the second rotor. According to a power transmission mechanism of a second invention, the spring constant of the elastic means is determined such that the resonance frequency (fR) is lower than the lowest frequency (f2) of torque fluctuation generated in the drive source (fR<f2).
The first rotor, the elastic member and the second rotor form not only a power transmission system from the drive source to the driven apparatus, but also a vibrating system, which includes the drive source. The elastic means transmits rotation power of the first rotor, which is coupled to the drive source, to the second rotor, which is coupled to driven apparatus. Accordingly, the torque of the drive source is transmitted to the driven apparatus against the load acting on the rotating member of the driven apparatus. Depending on the type of the drive source, the torque fluctuates periodically. However, according to the second invention, the spring constant of the elastic means is carefully selected such that the resonance frequency (fR), which is determined based chiefly on the spring constant of the elastic means and the sum of the moment of inertia of the rotating member of the driven apparatus and the moment of inertia of the second rotor, is lower than the lowest frequency (f2) of the torque fluctuation generated in the drive source. In other words, the resonance frequency (fR) is outside of the frequency range of torque fluctuation generated in the drive source. Therefore, given any torque fluctuation in the drive source, the amplitude of the torque fluctuation is not increased by resonance (resonance phenomena) due to the mechanical characteristics of the power transmission system. As a result, excessive noise and damage in the rotation system due to torque fluctuations of the driven apparatus are prevented.
The first invention and the second invention may be combined. That is, it is preferable that the spring constant of the elastic means be determined such that the resonance frequency (fR), which is determined based chiefly on the spring constant of the elastic means and the sum of the moment of inertia of the rotating member of the driven apparatus and the moment of inertia of the second rotor, is lower than the lowest frequency (f1) of the torque fluctuation generated in the driven apparatus an
Kato Tomonari
Kimura Kazuya
Okada Masahiko
Uryu Akifumi
Browne Lynne E.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
Thompson Kenn
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